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Flashcards in EQUINE Deck (239):
1

Which of these parasites causes granulomatous skin lesions that often contain small calcified dead larvae inside?

a. Onchocerca

b. Haematobia

c. Culicoides

d. Habronema

d. Habronema

Habronemiasis is a condition where the larvae of the stomach worm migrate and emerge, creating granulomatous lesions, usually around the eyett, male genitalia, or lower extremities. Inside the granulomas, you can find dead larvae. Culicoides hypersensitivity, also referred as sweet itch, occurs due to allergy to the saliva of the gnat. It recurs seasonally in the warmer months and tends to worsen with age. Typically, horses are pruritic and develop lesions on the poll, mane, and tail from self trauma, although ventral midline dermatits can occur as well. More chronically, scarring can occur. Treatment is to decrease exposure to the gnat and to treat with steroids. Haematobia irritants is a bigger problem in cattle than horses (they reproduce in cow feces) but can affect horses, especially ones that are near cattle. It typically causes ventral midline dermatitis with wheals with a central crust that progress to alopecia and ulceration with fairly focal lesions. Onchocerca can cause dermatitis in the horse due to hypersensitivity to dying microfilariae. Lesions include alopecia and scaling of the ventral midline, face, and pectoral region. Often lesions are diamond shaped, and there may be a "bull's eye" lesion on top of the head

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2

You are visiting a horse farm to evaluate a horse with seborrheic lesions of the oatern and mild lameness.  The owner notes that his horses have had problems with "Scrathces" in the past.  Which of the following management recommendations would be helpful in preventing this problem?

a. Keep the horses in an insect-free environment

b.  Keep the horses away from the sun during the hottest hours of the day

c. Keep the horses in a dry and clean environment

d.  Keep the horses on a regular deworming regimen

c. Keep the horses in a dry and clean environment

Scartches is a condition of chronic seborrheic dermatitis of the palmar/plantar aspect of the pastern.  The condition is sometimes referred to by several other names including "grease heel", "dermatitis verrucosa". "dew poisoning" and "mud fever".  It is not specific to the underlying infectious cause but the condition is generally associated with horse kept in wet or muddy environment.

Treatment involves removing the horse from the wet environment, clipping the surrounding hair, and gently washing and cleaning the area with a disinfectant followed by careful drying.  Topical ointments or astringent dressings may sometimes be used.  The best prevention is to keep horses in a dry and clean environment and maintain good hygiene practices

3

A 2-month-old Thoroughbred foal presents with the onset of profuse watery diarrhea and you suspect salmonellosis (image).  There are three specific diagnostic parameters that you, as the clinician. must assess to determine whetehr or not this patient should be confined to isolation.  What are the three diagnostic parameters?

a. Diarrhea, fever, and neutrophilia.  All 3 of the diagnostic parameters must be present to qualify for isolation

b.  Diarrhea, fever, and neutrophilia.  All 3 of the diagnostic parameters must be present to qualify for isolation

c.  Diarrhea, fever, and neutropenia.  Any 2 of the 3 diagnostic parameters qualify for isolation

d.  Diarrhea, fever, and neutrophilia.  Any 2 of the 3 diatnostic parameters qualify for isolation

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c.  Diarrhea, fever, and neutropenia.  Any 2 of the 3 diagnostic parameters qualify for isolation

Any 2 of these 3 parameters meet the criteria to admit any equine patient into isolation.  The most likely cause of the neutropenia is bacteria septicemia and endotoxemia due to gastrointestinal disease.  Other common disease that can cause a neutropenia are metritis and coliform mastitis

4

What is the most common cause of colic in a newborn foal?

a. Salmonella

b. Nephrosplenic entrapment

c. Strongylus vulgaris

d. Meconium impaction

e. Parascaris equorum

d. Meconium impaction

Meconium impaction occurs in the rectum or small colon.  Clinical signs include straining, swishing of the tail, and restlessness.  Rectal examination reveals numerous hard fecal balls.  Treatment consists of an enema with water and a mild soap.  Meconium is the first intestinal discharges of the newborn foal, consisting of epithelial cells, mucus, and bile

5

What is the most common gastric neoplasia in the horse?

a. Lymphosarcoma

b. Adenocarcinoma

c. Squamous cell carcinoma

d. Mesothelioma

c. Squamous cell carcinoma

Squamous cell carcinoma is the most common reported gastric neoplasia in the horse; the other answers have been rarely observed.  Presenting signs include weight loss and colic.  Unfortunately, there is no effective treatment at this time

6

A 13-year old Hanoverian brood mare presents for an acute onset of lethargy, anorexia, and explosive, watery, diarrhea. The diarrhea began approximately 14 hours after the initial signs of anorexia and lethargy. Clinicopathologic findings include neutropenia 2300/ul (normal 2,900-8,500/ul) with toxic neutrophils along with the typical electrolyte abnormalities seen with diarrhea Sodium 115 mEq/L (128-142 mEq/L) and Chloride 83 mEq/L (98-109 mEq/L). Which of the following pathogens is most commonly known for being able to cause a presentation such as the one described in this horse?

a. Parascaris equorum

b. Ehrlichial equi (Anaplasma phagocytophilia)

c. Strongyloides westeri

d. Salmonella

d. Salmonella

Salmonella can cause several different clinical presentations including subclinical infection, self limiting diarrhea, and acute diarrhea with endotoxemia.

Parascaris equorum and Strongyloides westeri are both parasites that may cause diarrhea. Parascaris equorum infestations may result in lethargy, depression, and respiratory signs. Occasionally, they result in intestinal obstruction and subsequent perforation. Strongyloides westeri is associated with diarrhea in foals and not in adult horses. Mares usually harbor this organism in their tissues and then transmit the parasite in the milk, thus infecting foals. Ivermectin administered to the mare will usually kill any Strongyloides westeri harbored by the mare.

Clinical signs of Ehrlichia equi include lethargy, anorexia, fever, limb edema and hematology changes such as neutropenia and thrombocytopenia. One might confuse Ehrlichia equi with Ehrlichia risticii (Neorickettsia risticii), the later causing lethargy, anorexia, fever, diarrhea, and laminitis. However, keep in mind that less than 60% of horses with Potomac Horse Fever develop diarrhea.

Diagnosis of E. risticii requires measurement of paired serum titer via immuno-fluorescent antibodies or detection of the organism via PCR in the blood or feces. Diagnosis of Salmonella requires serial cultures of feces for 3-5 days. Diagnosis of Strongyloides westeri and Parascaris equorum is by demonstration of eggs in the feces.

7

A valuable horse suddenly developed severe intractable diarrhea and fever 5 days ago. The owner has been giving it oral electrolytes free choice in the water, and offering it hay, grain, and green grass. It is brought to your clinic on a normal warm summer day looking thin, dehydrated, weak, and anorectic (see photo). You do a physical exam and find T=102F (38.9 C), HR=56, RR=24, with somewhat purplish oral mucous membranes. The urine is normal but has a small volume and looks concentrated. You run a PCV (45%), WBC count (normal at 7000/microliter) and total protein (TP). The TP is low at 3.5 gm/dL and the albumin is 1.4 gm/dL indicating a protein-losing enteropathy. Of the following, what is the best treatment for the low plasma proteins in this horse?

a. IV plasma

b. Whole blood IV

c. Oral albumin

d. IV amino acids

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a. IV plasma

The damaged bowel is leaking albumin out into the gut lumen, and the horse may develop other problems such as edema and poor healing ability if the protein levels are not boosted. The best way to do that in an animal with GI disease is by the IV route. Whole blood may raise the PCV to a level where sludging and circulatory problems develop in an already dehydrated horse. Another option to consider if plasma is not readily available is the use of synthetic colloidal solutions such as hetastarch.

8

You are treating a colicky 8-year old horse and pass a stomach tube to assess gastric reflux. The 20 liters of reflux is hemorrhagic, orange-brown in color, and foul-smelling. On physical exam, you find T=101.5F (38.6 C), HR=70, and RR=35 and overall depressed attitude. There are few auscultable gut sounds. Oral mucous membranes are injected. On rectal exam, there are multiple dilated fluid-filled loops of bowel palpated. Peritoneal fluid is serosanguinous with a 3.5 gm/dl protein and a WBC count of 7000. After decompressing the stomach, the horse appears less painful, but remains depressed. Based on these findings, what is the best tentative diagnosis?

a. Impaction colic (large bowel impaction)

b. Verminous arteritis cuased by strongylus vulgaris

c. Duodenitis-proximal jejunitis

d. Large bowel torsion

e. Acute small intestinal obstruction

c. Duodenitis proximal jejunitis

Duodenitis-proximal jejunitis, also known as either anterior enteritis, or proximal enteritis best fits this case because of the characteristic reflux, fever, peritoneal fluid characteristics, rectal findings, the depression and relatively less pain than would be expected with an obstruction. The cause is still uncertain, but a relationship of this disease to positive cultures of reflux for Clostridium difficile has been found. Typically these cases are treated medically, which would include repeated decompression of the stomach, IV fluids, replacement of electrolyte deficiencies, analgesics and correction of any acid-base abnormalities.

9

Consumption of yellow star thistle results in this lesion.

a. Leukoencephalomalacia of the reticular system

b. Destruction of the lateral and medial geniculate nucleus

c. Destruction of the pons

d. Nigropallidal encephalomalacia

d. Nigropallidal encephalomalacia

Consumption of yellow star thistle destroys the globus pallidus and the substantia nigra. These lesions will result in a characteristic dysphagia.

10

A 12-year old mare presents for a sudden onset of ptyalism and an inability to prehend food. Where is the lesion?

a. Substantia nigra and globus pallidus

b. Carpus callosum and amyglada

c. Caudal cerebellar peduncle and medial longitudinal fasciculus

d. Lateral lemniscus and rostral olivary nucleus

a. Substantia nigra and globus pallidus

A lesion to these basal ganglia will result in movement disorders. Particularly, yellow star thistle poisoning will lead to an inability to prehend food in horses. The corpus callosum connects the two cerebral hemispheres together, and the amygdala is involved with fear and memory. The caudal cerebellar peduncle connects the medulla to the cerebellum and is involved in transmission of signals pertaining to movement. The medial longitudinal fasciculus is involved in conjugate gaze. The rostral olivary nucleus and lateral lemniscus are both involved in auditory pathways.

11

The owner of a horse farm in the Southeastern United States calls you to come to his place two days after a huge wind storm that knocked down trees and power poles. There are seven ill horses. Upon examination you note lethargy, anorexia, dyspnea, coffee-colored urine, and icterus. Which of the following is the most likely cause?

a. Rattlesnake bite

b. Equine infectious anemia

c. Red maple (Acer rubrum) poisoning

d. Babesiosis

e. Copper poisoning

c. Red maple (Acer rubrum) poisoning

Horses seem to eat the leaves when branches are available, and the plant contains an unidentified hemolysin in wilted leaves. Ingestion can be fatal.

12

You are examining a 5-year old pony for lethargy, anorexia, and mild intermittent colic. Upon physical examination, you notice the abnormal finding in the image. Consumption of which of the following can produce these clinical signs and physical examination findings?

a. Oak leaves and acorns (Quercus sp)

b. Red maple leaves (Acer rubrum)

c. Black walnut (Juglans nigra)

d. Yellow star thistle (Centaurea solstitialis)

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b. Red maple leaves (Acer rubrum)

The sclera appears icteric. In combination with the clinical signs, ingestion of Red maple leaves would result in these signs due to hemolysis and low oxygen content of the blood. Oak is toxic but causes diarrhea and abdominal pain, whereas Black walnut is associated with laminitis. Yellow star thistle causes nigropallidal encephalomalacia resulting in CNS signs.

13

Which of the following causes liver failure when ingested by horses?

a. Oleander

b. Fiddleneck

c. Bracken fern

d. Astragalus

 

b. Fiddleneck

Fiddlenecks contain pyrrolizidine alkaloids as does groundsel, ragwort, and senecios. Pyrrolizidine alkaloids cause secondary photosensitization as well as hepatic damage that are cumulative and progressive. Treatment consists of supportive care for liver failure and prognosis is poor.

14

What are the two most common NSAID toxicoses seen in the horse?

a. Right ventral colitis and pulmonary edema

b. Renal papillary necrosis and right dorsal colitis

c. Hepatic necrosis and renal papillary necrosis

d. Bone marrow suppression and hepatic necrosis

e. Right dorsal colitis and splenic infarcts

b. Renal papillary necrosis and right dorsal colitis

The exact reason why the right dorsal colon is susceptible to ulceration as a result of NSAID use is not entirely known. Interestingly, some horses may develop right dorsal colitis even on appropriate doses of NSAIDS. Consistent findings of right dorsal colitis include colic and hypoproteinemia. The lesion in the kidney is classic and is due to the limited blood flow normally supplied to the corticomedullary region of the kidney. This part of the kidney relies on prostaglandins for adequate blood flow; with inappropriate NSAID use, blood flow to this area of the kidney is compromised, resulting in this classic lesion. Don't forget, NSAIDs are also associated with gastric ulcers.

15

If a horse is in seasonal anestrus, which of these is the most effective means of hastening the start of the breeding season?

a. Provide artificial light for 16 hours per day 30 days prior to the start of breeding

b. Provide artificial light for 12 hours per day 60 days prior to the start of breeding

c. Provide artificial light for 16 hours per day 60 days prior to the start of breeding

d. Provide artificial light for 12 hours per day 30 days prior to the start of breeding

c. Provide artificial light for 16 hours per day 60 days prior to the start of breeding

To get a horse to transition out of seasonal anestrus, you can gradually increase the amount of light to 15-16 hours per day to initiate ovarian activity. It usually takes at least 60 days until physiologic breeding will occur. There are hormonal methods to promote cycling, but they are less consistent than altering light.

16

You suspect equine infectious anemia is a cause of abortion in a mare. What test would confirm this diagnosis?

a. Direct Coomb's test

b. Coggin's test

c. Indirect Coomb's test

d. Live biopsy with immunofluorescent antibody

e. Blood smear

b. Coggin's test

This test is an agar immunodiffusion to detect serum antibodies against the retrovirus causing equine infectious anemia. Coomb's tests are done to diagnose immune mediated hemolytic anemias. The blood smear and liver biopsy would not show anything specific for equine infectious anemia.

17

A uterine biopsy is most useful for which of the following in a mare?

a. Predicting if a mare can carry a foal to term

b. Predicting where a mare is in the estrus cycle

c. Predicting if a mare can undergo parturition without dystocia

d. Predicting if a mare can become pregnant

a. Predicting if a mare can carry a foal to term

Uterine biopsies in horses are most useful to determine the amount of fibrosis present in an older mare's uterus, which indicates how able she is to carry a foal to term. Biopsies can be categorized into Kenney categories, which is a scoring system from 1-3 where a "1" means there are minimal changes and a "3" indicates marked changes. A mare with a score of "3" has approximately a 5% chance of carrying a pregnancy to term. However, she may still be able to get pregnant. Biopsy will show some changes that reflect the phase of the cycle but is not an accurate way to predict where you are in the cycle.

18

A mare has aborted due to an equine herpesvirus-1 infection. What would you tell the owner about her future as a breeding horse?

a. She should be treated with oral acyclovir for at least 3 weeks to avoid future abortions

b. Future breeding are still possible, and the mare can still prodcue healthy foals in the future

c. She will be latently infected and should not breed this mare again

d. The mare can maintain a future pregnancy, but the fetus is likely to be born with equine herpesvirus with a low chance of survival

b. Future breeding are still possible, and the mare can still prodcue healthy foals in the future

Vaccination of the mare during her next pregnancy against EHV (gestational months 5, 7 and 9) may help lessen the chance of abortion in the future. Acyclovir, while active against herpesvirus is not indicated (and is not well absorbed orally anyway).

19

You examine a 2 year old horse with the complaint of bilateral nasal discharge and lethargy for about a week. The horse has a temperature of 102F (38.9 C), HR 40, and RR 25. The nasal discharge is non-odorous and contains multiple bacteria and neutrophils. The lateral throat area is swollen and tender on palpation. Lateral radiographs reveal fluid lines in the area of the guttural pouches. You submit some of the liquid pus for culture. What treatment is now most indicated?

a. Dialy catheterization and lavage of the pouches

b. IM tetracycline daily for 2 weeks

c. Systemic erythromycin for one month

d. Systemic treatment with antifungal drugs for 4 weeks

e. Immediate surgical drainage

a. Dialy catheterization and lavage of the pouches

Irrigation should use saline or saline plus an appropriate and non-irritating antimicrobial drug. Systemic antimicrobial drugs are also used, but the hallmark of successful therapy is lavage and drainage. For inspissated pus or refractory cases, surgical drainage may be necessary.

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20

Which of the following treatments is the least effective in the management of Recurrent Airway Obstruction (RAO; also known as chronic obstructive pulmonary disease) in a horse?

a. Corticosteroids

b. Flunixin meglumine

c. Environmental changes

d. Clenbuterol

b. Flunixin meglumine

While flunixin (Banamine) is a common non-steroidal anti-inflammatory drug used in horses, it does not impart great therapeutic benefits in the horse with RAO. RAO is characterized by bronchoconstriction and accumulation of mucus/neutrophils. Clenbuterol is a Beta agonist that causes bronchodilation, while corticosteroids are potent anti-inflammatory medications that can reduce mucus and neutrophil accumulation. Environmental changes, such as placing the horse at pasture, feeding hay that has been soaked in water, and trying to reduce exposure to inhaled allergens are also part of the treatment protocol for a horse with RAO.

21

Equine viral arteritis can be transmitted by which of these routes?

a. Blood-sucking arthropods

b. Venereally

c. Fecal-oral

d. Through open wounds

b. Venereally

Carrier stallions can infect mares. It can also be spread by aerosol. Equine viral arteritis (EVA) is in the genus Arterivirus, family Arteriviridae and causes vasculitis leading to edema, conjunctivitis, rhinitis, and abortion.

 

22

You are evaluating a 4 year old Thoroughbred for intermittent epistaxis. Upon examination of skull radiographs (see image), what is the most likely diagnosis for the epistaxis?

a. Exercise induced pulmonary hemorrhage

b. Nasal adenocarcinoma

c. Guttural pouch mycosis

d. Ethmoid hematoma

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d. Ethmoid hematoma

The most likely cause of the epistaxis based on the radiographs is ethmoid hematoma. These lesions are angiomatous masses that originate from the mucosal lining of the ethmoid conchae or walls of the maxillary or frontal sinus. Guttural pouch mycosis also can result in epistaxis but typically has no radiographic changes. Although horses can get tumors in the nasal passages, this is relatively rare. Exercise-induced pulmonary hemorrhage also can result in epistaxis, but the blood originates from the lungs. In the radiograph provided, notice the smooth, well-defined soft tissue mass in the sinus region of this horse. No osseous changes or fluid lines are apparent in this radiograph. In this particular case (ethmoid hematoma), the soft tissue mass is actually dorsal to the ethmoid turbinates (ethmoids are normal appearance in this case). Upon surgical removal, a definitive diagnosis of ethmoid hematoma was confirmed

23

What is the treatment of choice for a Rhodococcus equi infection in a foal?

a. Penicillin and metronidazole

b. Enrofloxacin and ampicillin

c. Trimethoprim-sulfa and metronidazole

d.  Erythromycin (or other macolide antimicrobial such as clarithromycin and rifampin

d.  Erythromycin (or other macolide antimicrobial such as clarithromycin and rifampin

This is a must-know fact, as this disease is very commonly encountered. Treatment is usually for about 2 months but should be based on resolution of clinical signs, radiographic signs, and bloodwork. More recently, newer macrolide antimicrobials such as Clarithromycin and Azithromycin have been used in foals with R. equi pneumonia. One clinical study demonstrated better outcome with Clarithromycin and rifampin; additionally, Clarithromycin is typically administered twice daily, whereas erythromycin may have to be administered four times a day.

24

A 4 year old horse presents to you with a mucopurulent nasal discharge, lethargy, and depression. On physical exam, the horse has a temperature of 103.7F (39.8 C) and has markedly enlarged mandibular and retropharyngeal lymph nodes. You suspect that the horse has strangles. What would you expect to see if you aspirated one of the enlarged lymph nodes?

a. Purulent inflammation and gram positove cocci with large capsules

b. Reactive lymphocytes and macrophages with no bacteria

c. Purulent inflammation and gram negative rods with large capsules

d. Granulomatous inflammation and gram negative cocci

e. Fungal hyphae and granulomatous inflammation

a. Purulent inflammation and gram positove cocci with large capsules

The causative agent of strangles is streptococcus equi ssp. equi which is a gram positive cocci with a large capsule. It causes suppurative abscessation and enlargement of the mandibular and retropharyngeal lymph nodes.

25

7 year old male Clydesdale horse presents for exercise intolerance and noisy breathing. On your exam, you note mild inspiratory dyspnea with an audible whistling sound on inspiration. What is the most likely diagnosis?

a. Laryngeal hemiplegia

b. Sinusitis

c. Asthma

d. Intrathoracic large airway obstruction

a. Laryngeal hemiplegia

In this condition, the recurrent laryngeal nerve is damaged. Interestingly, the left side is almost always the side that is affected. An actual cause is usually not found, although direct trauma and certain toxins can cause laryngeal hemiplegia. It is thought to be a hereditary disorder. An intrathoracic large airway obstruction and asthma would both cause more expiratory dyspnea. Sinusitis may cause nasal discharge but is not likely to cause the signs this horse is showing.

26

In the horse, what is the most important muscle or muscle group required for the inspiratory phase of the respiratory cycle?

a. External intercostals

b. Abdominal muscles

c. Diaphragm

d. Internal intercostals

c. Diaphragm

Contraction of the diaphragm pushes the abdominal contents back, increasing the length of the thoracic cavity, and pulls the ribs abaxially. The external intercostal muscles assist in pulling the ribs abaxially. This ends up producing subatmospheric intrathoracic pressures and allows inspiration to occur. Contraction of the internal intercostal muscles and the muscles of the abdominal wall decrease lung volume and compress the chest wall. The diaphragm is important in this process because diseases altering innervation or strength of the diaphragm (such as botulism or phrenic nerve damage) or diseases preventing expansion of the diaphragm into the abdomen (such as large colon torsion) are important causes of respiratory distress and potentially hypoxemia and death.

27

Cervical vertebral stenotic myelopathy in horses is best treated with _______.

a. Surgery

b. Steroids

c. Non-steroidal anti-inflammatories

d. Stall rest

a. Surgery

Surgery is required so that you may stabilize the cervical vertebrae and decompress the spinal cord. There are two forms of cervical vertebral stenotic myelopathy (aka wobbler syndrome). One form is called cervical vertebral instability. In this case, ventroflexion of the neck results in spinal cord compression. Most commonly affected sites are C3-4 and C4-5. The other form is known as cervical static stenosis. In this case, the compression is continuous regardless of the neck position. Clinical signs are usually in the form of a wide-based stance, conscious proprioceptive deficits, ataxia, paresis, and spasticity which is worse in the hindlimbs. Anti-inflammatories and stall rest may temporarily decrease clinical signs but are typically not a long-term therapy.

28

A 6-year old Morgan horse presents for an ocular evaluation. The owner is concerned that the horse has a corneal ulcer. You notice that the horse has marked blepharospasm. Which of the following best describes the effects of an auriculopalpebral nerve block in this horse?

a. Blocks sensory innervation of the upper two-thirds of the eyelids

b. Blocks sensory innervation of the cornea

c. Disrupts motor innervation to the levator palpebrae superioris

d. Disrupts motor and sensory innervation to the eyelids

e. Disrupts motor innervation to the orbicularis oculi

e. Disrupts motor innervation to the orbicularis oculi

The auriculopalpebral nerve is a branch of the facial nerve and is therefore motor only. The auriculopalpebral block is useful in providing eyelid akinesis by blocking motor innervation primarily to the orbicularis oculi, thereby allowing manipulation of the eyelids without putting pressure on an already painful eye. This block is motor only and does not provide any desensitization.

The supraorbital/frontal nerve block can be used to block a branch of the ophthalmic division of the trigeminal nerve, desensitizing the middle two-thirds of the upper eyelid and forehead skin. It may also provide some motor block of the levator palpebrae superioris due to a branch of the oculomotor nerve which runs adjacent.

29

A 3-month-old paint colt presents to you after flipping over backward while being led by the owner the previous day. Clinical signs at the time of presentation are shown in the image (head tilt, flaccid ear, muzzle deviation). Based on the history and clinical signs, what cranial nerves are damaged and what is the most likely diagnosis?

a. Cranial nerves V and VII (left side); atlanto-occipital malformation

b. Cranial VII and VIII (left side); fracture of the basisphenoid bone

c. Cranial nerves V and VIII (left side); fracture of the sphenoid bone

d. Cranial nerves V and VII (left side); atlanto-occipital malformation

e. Cranial nerves VII and VIII (rightside); fracture of the basisphenoid bone

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b. Cranial VII and VIII (left side); fracture of the basisphenoid bone

The correct answer is damage to cranial nerves VII (facial nerve) and VIII (vestibular nerve) on the left side caused by fracture of the basisphenoid bone. This is a common injury when a fractious young foal rears up and falls backward on the poll. The basisphenoid bone becomes injured resulting in injury to cranial nerves VII and VIII. Damage to the facial nerve results in the muzzle deviation (opposite direction of the side of injury, in this case deviated to the right), ptosis of the left eye and drooping of the left ear. Damage to the vestibular nerve results in the head tilt.

30

What structure is not likely to be affected with a guttural pouch infection of a horse?

a. CN VIII

b. CN VI

c. CN IX

d. Carotid artery

e. Cranial sympathetic trunk

b. CN VI

This nerve does not run along the guttural pouch in contrast to the others listed. Both the internal and external carotids may be affected during a guttural pouch infection. In case you don't remember, the guttural pouch in a horse is the air-filled diverticula of the auditory tube which communicates between the middle ear and the pharynx. Sometimes foreign material will get trapped there and result in infection.

31

How long after receiving a puncture wound would you expect to see clinical signs of tetanus if a horse was infected?

a. 3-4 weeks

b. 3-5 days

c. 1-2 hours

d. 10-14 days

e. 12-24 days

 

d. 10-14 days

Typically, the incubation period for tetanus is about 2 weeks, because it takes time for the spores to grow in an anaerobic environment before they produce toxin that can then be picked up by the nerves.

32

The owner of a weanling colt has asked for a pre-purchase examination to be performed on her 4 month old colt. The colt appears in good health based on physical examination with the only abnormality noted being a holosystolic murmur heard best on the right side of the thorax. What is your diagnosis based on auscultation and echocardiographic findings (see image; long-axis view from left side)?

a. Atrial septal defect (ASD)

b. Ventricular septal defect (VSD)

c. Truncus arteriosus

d. Patent ductus arteriosus (PDA)

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b. Ventricular septal defect (VSD)

The image demonstrates a VSD or a hole in the intraventricular septum (identified by two markers). This is one of the more common congenital defects of the heart in horses.

The murmur occurs as blood is shunted from the left side of the heart to the right during systole. Some horses can perform normally with a VSD while others, with large defects, can demonstrate heart failure. In this case, it was an incidental finding, as the horse was bright and alert at the time of exam. The remainder of the answers (ASD, PDA, and truncus arteriosus) can occur but are less common and would appear differently on echocardiography.

It is unlikely but possible that you will be asked to interpret an echocardiogram on your board exam. If you are, this is likely to be one of the diseases you could be shown.

33

What is the treatment of choice for atrial fibrillation in the horse?

a. Electrical defibrillation

b. Digoxin

c. Precordial thump

d. Do nothing; this is a benign arrhythmia in the horse

e. Quinidine

e. Quinidine

Ideally, you would begin oral dosing of quinidine via a nasogastric tube at 2 hour intervals until there is conversion or toxicosis. An increase in the QRS duration of greater than 25% as compared to before initiation of treatment is considered a sign of toxicity. Clinical signs of toxicosis include colic, ataxia, hypotension, diarrhea, and edema. Digoxin will not convert an atrial fibrillation to a normal rhythm. However, it is indicated as adjunctive therapy when the vagolytic effect of quinidine causes a significant acceleration in ventricular response rate, the resting heart rate in excess of 90 beats per minute, if the horse is exhibiting a low vagal tone, or if conversion has not been achieved within 24 hours of initiating quinidine therapy. A precordial thump is ineffective, and defibrillation is only indicated during ventricular fibrillation, not atrial. Usually, there is an excellent prognosis for conversion if the horse has a heart rate of less than 60 beats per minute, atrial fibrillation of less than four months duration, and if there is a murmur less than or equal to a grade 3/6.

34

What is the most frequently observed side effect associated with acepromazine use in horses?

a. Arrythmias

b. Paraphimosis

c. Hypotension

d. Seizures

 

c. Hypotension

Acepromazine will reliably cause hypotension. Acepromazine may cause paraphimosis in male horses, but this is not very common. However, because of this, many veterinarians will not use acepromazine on stallions. Acepromazine actually has anti-arrhythmogenic properties. Acepromazine does reduce the seizure threshold, but seizures are not as common as hypotension.

35

A 28 year old Paint stallion presents with an acute onset of colic. On presentation he has a rectal temperature of 99.8F (37.7 C), heart rate of 75 beats/min, respiratory rate of 24 breaths/min, and is pawing and trying to lie down. CRT is approximately 3.0 seconds, and mucous membranes are purple-red. Gastrointestinal sounds are completely absent, and gastric reflux yielded 18L of brown- to yellow-colored fluid. Peritoneal fluid analysis yielded a cloudy yellow fluid with a protein of 3.2 gm/dl and white blood cell count of 11,000/ul. Which of the following is a possible diagnosis?

a. Cecal volvulus

b. Left dorsal colon displacement

c. Strangulating lipoma

d. Strongylus vulgaris infestation

e. Right dorsal colon displacement

c. Strangulating lipoma

Lipomas are a common cause of small intestinal obstruction in older horses. Typically, a section of the small intestine becomes intertwined with a pedunculated lipoma, resulting in obstruction and possible devitalization of the small intestine. Surgical correction is necessary to correct this problem. None of the other answer choices typically result in the clinical signs described, particularly gastric reflux. Left dorsal colon displacement typically have milder clinical signs, and the diagnosis can be made by rectal palpation and ultrasonography.

36

A Paint horse is found to be approximately 7% dehydrated after a several day trail ride.  Assuming there are no other ongoing losses and the horse weights 500kg how many liters of fluid will you need to give this horse over a 24 hou period to correct the deficit and account for maintenance requirements?

a.  40L

b.  65L

c.  35L

d.  75L

e.  125L

b.  65L

To determine this answer you must figure out the deficit and calculate the horse's maintenance needs.  The deficit is 35L (deficit x BW).  Maintenance needs for a horse is approximately 60mL/kg/day.  In this case, 30L.  Adding the deficit and maintenance fluids together yields a total of 65 liters.

37

A 36 hour foal born from a multiparous mare presents for weakness, decreased appetitie, and tachycardia.  On physical exam, you examine the sclera as seen in the photo.  Based on the signalment and findings, what is a likely cause?

a.  Congenital iron toxicity

b.  Neonatal Isoerythrolysis

c.  Immune mediated thrombocytopenia

d.  Failure of passive transfer

b.  Neonatal Isoerythrolysis

Neonatal Isoerythrolysis (NI) would be a possible cause of the icterus noted in the sclera.  NI is common in multiparous mares and usually affects foals between 24-72 hours of age.  NI results in hemolysis, hyperbilirubinemia, and icterus.  A low packed cell volume would further support NI.

 

NI develops because the newborn foal expresses alloantigens on its red blood cells inherited from the sire that the mare does not have.  If the mare becomes sensitized to the sire's specific antigen, maternal antibodies are produced and absorbed by the foal soon after birth.  This subsequently results in lysis of the red blood cells

38

Which of the following can cause aggression in mares?

a.  Melanoma

b.  Luteal cyst

c.  Granulosa cell tumor

d.  Sertoli Cell tumor

c.  Granulosa cell tumor

Granulosa=theca cell tumors are the most comon ovarian tumor in horses and can cause increased levels of testosterone, sometimes causing aggressive behavior towards people.  Another cause of aggression in horses is hypothyroidism.

39

During your examination of an 19-year old horse, you observe what

 

40

Two pet horses on a ranch are presented for extreme pruritus at their ventrum. The owners report the pruritus has gotten worse during the summer, and they notice increased numbers of small flying insects around at dusk and dawn. Examination of the horses reveals excoriations, alopecia, and thickening of the skin at the ventrum. One of the flies collected in the field by the owner is a small fly with mottled wings. What is your most likely diagnosis?

a. Onchocerciasis

b. Tabanus fly bites

c. Culicoides hypersensitivity

d. Mosquito hypersensitivity

e. Chrysops fly bites

c. Culicoides hypersensitivity

Culicoides hypersensitivity is extremely pruritic and is also known as "sweet itch". Horses can be affected on their ventrum or dorsum, depending on the species of the fly. The horse develops a type 1 hypersensitivity to the flies' salivary antigens and develops excoriations, alopecia, and thickened skin as a result of scratching. The flies are more prevalent during the warmer seasons and are most active during dusk and dawn. Treatment includes controlling the fly population. Stabling the horses at dusk is often helpful because the flies rarely enter barns. Insecticides, stable blankets, and fans for circulating air in the stables may also be useful. The extreme pruritus and seasonality of the clinical signs is often enough to differentiate the Culicoides hypersensitivity from other skin diseases. Onchocerciasis is vectored by Culicoides, but is not seasonal and is not nearly as pruritic. Mosquitoes can be an annoyance and, more importantly, are vectors for more serious diseases such as the equine encephalitides. Tabanus flies and Chrysops flies cause pain to horses by lacerating them with their mouth parts to feed on their oozing blood. They do not cause pruritus and can be differentiated by their large, robust size.

41

Which of the following is not known to classically cause crusting dermal lesions on horses?

a. Dermatophytosis

b. Dermatophilosis

c. Generalized granulomatous disease

d. Corynebacterium psuedotuberculosis

e. Pemphigus foliaceus

d. Corynebacterium psuedotuberculosis

Corynebacterium pseudotuberculosis is also known as pigeon fever. It causes an ulcerative lymphangitis and abscesses in the pectoral region of horses. Treatment is aimed at hot packing the swellings and draining the abscesses. Antibiotics can be administered but have been known to prolong the disease by delaying abscess formation. The other four answer choices classically present as crusting dermal lesions on horses.

42

A 6-year old Quarter Horse presents with the lesion seen in the photograph. Which of the following is true regarding equine sarcoids?

a. Papiloomavirus is believed to play a role in the pathogenesis

b. They usually regress spontaneously without treatment

c. Surgical excision is nearly always curative

d. Metastasis is common with advanced lesions

Q image thumb

a. Papiloomavirus is believed to play a role in the pathogenesis

Sarcoids are one of the most common tumors in horses. They are considered non-metastatic tumors in virtually all cases. For this reason, small lesions are sometimes treated with benign neglect, but they are not expected to regress. More advanced lesions or tumors in certain sites do need to be treated more aggressively. Unfortunately, no single treatment is universally effective. Recurrence rates after surgical excision are approximately 50%. Although there is still controversy surrounding this issue, either bovine papillomavirus or an equine variant is thought by many to play a role in development of these tumors.

43

A Thoroughbred race horse has been moved from California to Florida in July and is experiencing poor performance, exercise intolerance and tachypnea. You observe the horse working out one hot afternoon and see these signs, but you also note that the horse is not sweating. You check the rectal temperature and note that it is 104F (40 C). What is the diagnosis?

a. Anhidrosis

b. Hypothyroidism

c. Diabetes insipidus

d. Equine Cushing's

e. Influenza

a. Anhidrosis

Anhidrosis is the inability to sweat, which can be fatal if not addressed. The cause is unknown. It tends to occur in hot humid climates, and may occur in horses raised in the climate, or more commonly, horses brought into the climate. The most successful treatment is to move the horse back to a more favorable climate.

44

What stimulates antidiuretic hormone (ADH) secretion in the horse?

a. Hyperosmolality and increased circulating blood volume

b. Hypoosmolality and decreased circulating volume

c. Hypoosmolality and increased circulating volume

d. Hyperosmolality and decreased circulating blood volume

d. Hyperosmolality and decreased circulating blood volume

In the horse, as in other species, ADH increases renal water reabsorption and urine osmolality by increasing permeability of the collecting tubules. Osmoreceptors in the hypothalamus detect subtle changes in plasma osmolality. If osmolality rises, you will hope to see ADH secretion so that the urine excreted would be more concentrated. The same is true if circulating volume decreases; thus, a lesser volume of water would be lost. When ADH secretion does not occur or if the kidneys are unable to respond to ADH, this is likely diabetes insipidus, and animals will be very polyuric, polydipsic and have extremely dilute urine.

45

A 23-year old Morgan horse presents to you for evaluation due to several changes that the owner has noticed in recent months. He reports that the horse has been drinking and urinating more frequently and seems to have lost muscle mass. He also reports excessive sweating and hair coat changes. Specifically he reports that the horse has developed a long curly hair coat that does not shed properly (see image). You recognize this array of clinical signs as being very consistent with a common clinical syndrome in older horses. Which of the following is the most appropriate treatment for this condition?

a. Pergolide

b. Levothyroxine

c. Quinidine

d. Glargine

e. Dexamethasone

Q image thumb

a. Pergolide

This case describes the typical presentation of equine pituitary pars intermedia dysfunction (PPID), sometimes referred to as equine Cushing's disease. The disease is a progressive disorder of pituitary pars intermedia enlargement (adenoma). The condition usually affects horses greater than 15 years of age and may affect any breed but ponies and Morgan horses have increased incidence. The classic symptom which is highly suggestive of this condition is hirsutism which is the symptom of a long curly hair coat that does not shed properly. Other symptoms include polyuria, polydipsia, laminitis, lethargy, excessive sweating or lactation, decreased muscle mass, infertility, and susceptibility to infections such as tooth root abscesses.

Hirsutism as a clinical sign is the most sensitive indicator of PPID. Diagnosis of PPID by laboratory testing in horses with subtle signs can be challenging since no single test is absolutely sensitive and specific. Measurement of plasma ACTH concentrations is a simple and acceptable test, but must be compared to seasonal reference intervals as the concentration of ACTH fluctuates during the year (highest in the September, lower in January). Of practical note, the sample must be chilled or frozen until processing. Others have suggested the use of the thyrotropin-releasing hormone (TRH) stimulation test, which causes a significantly higher concentration of ACTH in PPID horses. However, TRH is may not be readily available. Finally, the dexamethasone suppression test has historically been used to diagnose PPID, but concerns in regard to steroid administration and the development of laminitis (or worsening of existing laminitis) has resulted in the test being used less frequently.

Treatment aims to decrease clinical signs and does not typically result in a cure or complete remission of all signs. Pergolide is generally considered the treatment of choice. Pergolide is a dopamine agonist that is used to treat Parkinson's disease in humans. The drug acts to suppress pituitary hormone secretion. Older references will refer to the use of cyproheptadine which is a serotonin antagonist as a preferred treatment for PPID. There is also investigation that trilostane, a 3-beta hydroxysteroid dehydrogenase inhibitor may be useful in the management of PPID.

Quinidine is used to treat atrial fibrillation in horses. Glargine is a long acting insulin analogue used in the treatment of diabetes mellitus. Levothyroxine is a synthetic thyroid hormone used to treat hypothyroidism. Dexamethasone is a corticosteroid and can be used to help establish a diagnosis of PPID but is not a treatment.

46

A 2-month-old Thoroughbred foal presents with the onset of profuse watery diarrhea and you suspect salmonellosis (see image). There are three specific diagnostic parameters that you, as the clinician, must assess to determine whether or not this patient should be confined to isolation. What are the three diagnostic parameters?

a. Diarrhea, fever, and neutropenia.  All 3 of the diagnostic parameters must be present to qualify for isolation

b. Diarrhea, fever, and neutrophilia.  All 3 the diagnostic parameters must be present to qualify for isolation

c. Diarrhea, fever, and neutropenia.  Any 2 of the 3 diagnostic parameters qualify for isolation

d. There are no specific diagnostic parameters for isolation qualification.  Any foal or horse with diarrhea should be admitted to isolation.

e. Diarrhea, fever, and neutrophilia.  Any 2 of the 3 diagnostic parameters qualify for isolation

Q image thumb

c. Diarrhea, fever, and neutropenia.  Any 2 of the 3 diagnostic parameters qualify for isolation

The most likely cause of the neutropenia is bacterial septicemia and endotoxemia due to gastrointestinal disease. Other common diseases that can cause a neutropenia are metritis and coliform mastitis.

47

You are treating a colicky 8-year old horse and pass a stomach tube to assess gastric reflux. The 20 liters of reflux is hemorrhagic, orange-brown in color, and foul-smelling. On physical exam, you find T=101.5F (38.6 C), HR=70, and RR=35 and overall depressed attitude. There are few auscultable gut sounds. Oral mucous membranes are injected. On rectal exam, there are multiple dilated fluid-filled loops of bowel palpated. Peritoneal fluid is serosanguinous with a 3.5 gm/dl protein and a WBC count of 7000. After decompressing the stomach, the horse appears less painful, but remains depressed. Based on these findings, what is the best tentative diagnosis?

a. Impaction colic (large bowel impaction)

b. Verminous arteritis caused by strongylus vulgaris

c. Doudenitis-proximal jejunitis

d. Large bowel torsion

e. Acute small intestinal obstruction

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c. Doudenitis-proximal jejunitis

Duodenitis-proximal jejunitis, also known as either anterior enteritis, or proximal enteritis best fits this case because of the characteristic reflux, fever, peritoneal fluid characteristics, rectal findings, the depression and relatively less pain than would be expected with an obstruction. The cause is still uncertain, but a relationship of this disease to positive cultures of reflux for Clostridium difficile has been found. Typically these cases are treated medically, which would include repeated decompression of the stomach, IV fluids, replacement of electrolyte deficiencies, analgesics and correction of any acid-base abnormalities.

48

Horses living in a sandy region such as California and Florida tend to be predisposed to developing sand enteropathies. If one is suspected, which of the following treatments will be most effective?

a. Mineral oil

b. Charcoal

c. Psyllium

d. Bismuth subsalicylate

c. Psyllium

Psyllium is a hemicellulose laxative that has the ability to bind with sand and help remove it from the gastrointestinal tract. Feeding the horse in a stall and/or utilizing hay racks will also help the inadvertent consumption of sand that may be ingested if a horse is eating on sandy ground. None of the other answer choices are as effective as psyllium.

49

A 7-year old male Thoroughbred presents with a history of colic, increased heart rate, and increased respiratory rate. On physical exam, there is no reflux; on rectal exam, the colon is palpable between the cecum and body wall. What is the diagnosis?

a. Cecal volvulus

b. Left dorsal colon displacement

c. Right dorsal colon displacement

d. Strandulating lipoma

c. Right dorsal colon displacement

The rectal exam findings are characteristic for a right dorsal colon displacement. You can sort of figure out the answer even if you know nothing about horses, just think anatomy. The cecum is on the right side... so there is probably something going on in the right side. A left dorsal displacement is the same thing as a nephrosplenic entrapment. In this case, the colon becomes trapped in the renosplenic space. A primary cecal volvulus is rare in horses and are usually seen secondary to a large colon volvulus. These horses will ping similarly to a cow and usually present with acute colic. A strangulating lipoma is highly unlikely, given the age of the horse and lack of gastric reflux. Additionally, these tend to strangulate small intestines, not the colon.

50

A horse presents to you with a corneal ulcer. You are concerned because it appears to be infected, as shown in this image. You perform cytology and find gram negative rods. What is the most likely organism infecting the corneal ulcer in this horse?

a. E. coli

b. Pasturella multocida

c. Pseudomonas

d. Staphylococcus spp

Q image thumb

c. Pseudomonas

Pseudomonas is the most common agent causing bacterial keratitis in the horse. The gram negative cytology provides further evidence that it is the likely culprit. Staphylococcus can cause keratitis in horses but is gram positive. E. coli and Pasteurella are not agents that are commonly involved with keratitis in the horse.

51

Which of the following toxins causes reproductive failure in mares?

a. Fescue

b. Cantharidin

c. Pyrrolizidine alkaloids

d. Red maple

e. St. John's wort

a. Fescue

Fescue ingestion leads to prolactin suppression and can result in thickened placenta, dystocia, or agalactia. Red maple causes Heinz body anemia. St John's wort causes photosensitization and hepatotoxicity. Pyrrolizidine alkaloids cause photosensitization and hepatotoxicity. Cantharidin causes colic.

52

An 11-year old Peruvian Paso presents with a history of progressive weight loss. Serum chemistry shows elevation in sorbitol dehydrogenase, lactate, alkaline phosphatase, and a decrease in albumin. A vast amount of Crotalaria spp. is seen in the pasture. What type of toxin does Crotalaria spp. possess?

a. Nitrate

b. Pyrrolizidine alkaloid

c. Cyanide

d. Organophosphate

 

b. Pyrrolizidine alkaloid

The clinical signs described are typical for pyrrolizidine alkaloid toxicity. Consumption of this plant typically results in abnormalities in hepatic cell division; thus resulting in large hepatocytes known as megalocytosis.

53

In the Spring of 2001, a syndrome later termed Mare Reproductive Loss Syndrome, also known as MRLS, occurred in central Kentucky. This resulted in the abortion of 20-30% pregnant mares. Which of the following was NOT a manifestation of MRLS?

a. Fetal or neonatal hemoabdomen

b. Early fetal loss

c. Neonatal foal death

d. Late-term abortion

e. Fibrionous pericarditis

 

a. Fetal or neonatal hemoabdomen

The correct answer is fetal or neonatal hemoabdomen. All other choices listed were potential disease manifestations of MRLS. The exact pathogenesis of MRLS is still unknown, but the presence of eastern tent caterpillars was strongly associated with the disease. Later, experimental studies in which pregnant mares were exposed to or fed, via NG tube, eastern tent caterpillars resulted in early and late fetal loss.

54

You are called one hot summer day to see a group of horses in New Mexico which are slobbering and not eating their hay. Three out of 20 horses seem to be visibly affected. On physical exam of the first one, you find fever of 104 F (40 C) and obvious oral ulcers as shown in the image, mainly on the tongue. What is your tentative diagnosis?

a. Glanders

b. Bovine papular stomatitis

c. Foot-and-mouth disease (FMD)

d. Vesicular stomatitis

e. African Horse Sickness

Q image thumb

d. Vesicular stomatitis

VS affects horses, cattle and pigs with similar clinical signs. It is a viral disease of high morbidity and low mortality that appears about every 7 to 10 years in the Southwestern United States. Yearly outbreaks occur in southern Mexico and northern South America. Black flies and midges appear to be the vectors. Affected premises should be quarantined.

55

Which of the following is not a cause of dysphagia in the horse?

a. Foxglove

b. Guttural pouch mycosis

c. Tetanus

d. Rabies

a. Foxglove

This is a cardiotoxic plant

56

Consumption of fescue grass infected with Neotyphodium coenophialum by a pregnant mare may typically result in which of the following clinical signs?

a. Shortened gestational length and fetal skeletal malformation of the cuboidal bones

b. Prolonged gestation and decreased milk production

c. Shortened gestational length and fetal joint laxity

d. Prolonged gestation and fetal mummification

b. Prolonged gestation and decreased milk production

Common clinical signs associated with fescue toxicosis include prolonged gestation and/or decreased milk production (agalactia). Ergopeptine alkaloids are ingested by the mare, which act as dopamine agonists. Dopamine serves to inhibit prolactin, thus inhibiting lactation. Placental thickening and weak or stillborn foals may also occur.

57

Which of these is normally found in the guttural pouch of a healthy horse?

a. Aspergillus nidulans

b. Streptococcus equi ssp. zooepidemicus

c. Streptococcus equi ssp. equi

d. Salmonella

b. Streptococcus equi ssp. zooepidemicus

This is a normal inhabitant of the guttural pouch. Streptococcus equi ssp. equi can be present when there is guttural pouch empyema. Aspergillus nidulans can be present in cases of guttural pouch mycosis. Salmonella should not be present in the guttural pouch.

58

What age of horse is at highest risk for development of recurrent airway obstruction or heaves?

a. 2-6 months

b. 0-2 months

c. > 6 years of age

d. 1-5 years

e. 6 months to 1 year

c. > 6 years of age

RAO is a disease of mature horses older than 6 years of age. The direct cause is debatable but it has a progressive onset and is thought to be related to hypersensitivity to environmental factors. It is seen most commonly in the winter in stabled horses.

59

A 1.5-year old Quarter Horse gelding is presented to you for symmetric ataxia, weakness, and spasticity of all limbs, but worse in the hind limbs. When walking, the horse frequently drags his toes and the hind limbs frequently interfere with one another. Based on the signalment, history and physical examination findings, which of the following is the most likely cause of these clinical signs?

a. Equine Protozoal Myeloencephalitis (EPM)

b. Botulism

c. Equine Motor Neuron Disease (EMND)

d. Cauda Equina Syndrome

e. Equine Degenerative Myeloencephalopathy (EDM)

e. Equine Degenerative Myeloencephalopathy (EDM)

The horse in this question has clinical signs most consistent with EDM; cervical vertebral malformation (wobblers) is also a possibility, but was not provided as an answer. The cause of EDM is unknown, but this disease typically affects young horses (< 2-3 years of age; but older horses can develop disease). Clinical signs are a result of diffuse neuronal fiber degeneration of various portions of the central nervous system. This disease has been associated with low serum vitamin E concentrations, suggesting that oxidative damage may play a role in the development of disease.

EMND is typically associated with muscle tremors, shifting of weight while standing, muscle atrophy and recumbency. Botulism is associated with generalized muscle weakness. Cauda equina syndrome causes analgesia of the perineum. EPM can cause a range of clinical signs, but is typically with asymmetric neurologic deficits.

60

A 2-year-old Quarter horse filly presents with a history of intense pruritis and alopecia in the perineal area (see image). The owners indicated that they noticed the filly rubbing her tail head and perineal area along fences for a period of one week. What diagnostic test will you use to confirm your top differential?

a. A fecal flotation to confirm Oxyruis equi

b. A scotch tape test to confirm Oxyuris equi

c. A scotch tape test to confirm Strongyloides vulgaris

d. A superficial skin scrape to confirm Chorioptes spp.

e. A fecal flotation to confirm Cyathostomiasis

Q image thumb

b. A scotch tape test to confirm Oxyuris equi

While all of these diagnostic tests are important when you suspect parasitism, the scotch tape test will enable you to observe the eggs stuck to the hair. The egg laying activity by the female worm is what causes the intense pruritis. Occasionally, eggs can be found in a flotation, which may give you a false negative interpretation if not found. A superficial skin scrape is a great alternative for this case; however, Chorioptes spp. tend to infest breeds with feathered legs. An infestation of Strongyloides vulgaris or Cyathostomes will likely cause colic, diarrhea, and lethargy.

61

A horse presents to you with a laceration across the caudal aspect of the hock; the horse is not weight-bearing, and the hock completely dropped to the ground. What structure has likely been ruptured to cause these clinical signs?

a. Suspensory ligament

b. Superficial digital flexor

c. Proximal check ligament

d. Achilles tendon

e. Gastrocnemius

d. Achilles tendon

A complete laceration of the Achilles tendon involves rupture of the gastrocnemius and superficial flexor tendons. A gastrocnemius rupture alone may cause a dropped hock, but horses with this injury will still bear weight on the affected limb. Prognosis for this injury is grave.

62

A 9-month old foal presents with difficulty walking. You immediately note that the foal appears to have a flexural deformity of the right forelimb consisting of an increased dorsal hoof wall angle of 80 degrees such that the heel does not contact the ground. The coronary band is prominent. You take radiographs which confirm a broken forward hoof-pastern angle. What is the most appropriate treatment for this type of flexural limb deformity?

a. Superior check ligament desmotomy

b. Transection of the insertion of the semitendinosus

c. Lateral digital extensor tenectomy

d. Desmotomy of the accessory ligament of the deep digital flexor tendon

d. Desmotomy of the accessory ligament of the deep digital flex

This case describes a severe flexural deformity of the distal interphalangeal joint, also known as "clubfoot". This is typically a congenital condition in young horses although it can be acquired. A genetic component is suspected. Mild cases can sometimes be managed conservatively with NSAIDs, farriery, exercise and nutritional changes. Severe cases often require surgery; the surgical procedure of choice is desmotomy of the accessory ligament of the deep digital flexor tendon (also known as inferior check ligament desmotomy). The accessory ligament of the deep digital flexor tendon (inferior check ligament) runs from the palmar surface of the proximal metacarpus to the deep flexor tendon in the mid-metacarpal region.

The superior check ligament originates above the knee and attaches to the superficial flexor tendon, and its primary purpose is to support the tendon. Superior check ligament surgery is used to treat a bowed tendon.

Lateral digital extensor tenectomy is a procedure used to treat stringhalt. Transection of the insertion of the semitendinosus is used to treat fibrotic myopathy.

63

A 24-year old Appaloosa has an increased heart rate, increased respiratory rate, and is pacing while staring at her abdomen. During initial colic work up there was no gastric reflux. On rectal exam, a distended large colon could be palpated. On abdominal ultrasound, large colon was the predominant structure visualized on the left side while the left kidney could not be visualized via ultrasonography. What is the most likely diagnosis?

a. Right dorsal displacement

b. Strangulating lipoma

c. Nephrosplenic entrapment

d. Sand impaction

c. Nephrosplenic entrapment

The kidney is obscured as a result of a left dorsal displacement of the large colon over the nephrosplenic ligament. Additionally, the spleen is pushed away from the body wall, making it difficult to see on ultrasound. Large horses may be predisposed to this. Besides surgical correction, one may try to roll the horse 360 degrees. Pain associated with these types of displacements are usually mild to moderate.

64

What is the most common form of neoplasia seen in the intestines of a horse?

a. Lipoma

b. Squamous cell carcinoma

c. Lymphosarcoma

d. Leiomyosarcoma

c. Lymphosarcoma

Squamous cell carcinoma is the most common tumor of the equine stomach. Lipomas are seen commonly, but these do not involve the intestinal tract directly. Leiomyosarcomas are simply not as common as lymphosarcoma. Unfortunately, the prognosis in horses with lymphosarcoma is extremely poor.

65

You are examining a 13-year old Standardbred brood mare 5 hours after parturition. You note that the placenta is still present in the reproductive tract of the mare (see image). What is the most appropriate therapy?

a. Administer penicillin (IM) until the placenta is expelled on its own

b. Do nothing; the placenta is not considered retained until 12 hours post-parturition and it will likely be expelled by this time

c. Place physical traction on the placenta and remove it manually

d. Administer oxytocin (IM or IV) and lavage the uterus to facilitate removal

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d. Administer oxytocin (IM or IV) and lavage the uterus to facilitate removal

Most texts state that the placenta in a mare is retained after greater than 3 hours post-parturition; therefore, this would be considered a retained placenta. Oxytocin, along with uterine lavage, will cause the uterus to contract and facilitate expulsion of the placenta. Strong physical traction on the retained placenta is generally considered contraindicated, as you may tear the placenta and leave remnants of it within the uterus, resulting in possible complications. Broad-spectrum antimicrobials are often administered to decrease the incidence of metritis but alone would not be appropriate.

66

Equine infectious anemia is caused by what type of organism?

a. Bacteria

b. Rickettsia

c. Virus

d. Fungus

e. Protozoan

c. Virus

Equine infectious anemia is caused by a retrovirus that establishes a lifelong infection and causes cyclic anemia and abortions.

67

Which of the following answer choices results in encephalomyelitis?

a. Influenza

b. Strangles

c. Eastern equine encephalomyelitis

d. Tetanus

c. Eastern equine encephalomyelitis

This question was not meant to be hard. Another cause of a viral encephalomyelitis which we also vaccinate for is western equine encephalomyelitis. The other diseases do not result in encephalomyelitis. Tetanus will cause a rigid paralysis due to binding of tetanus toxin to inhibitory receptors. Influenza will usually cause respiratory disease. Strangles will usually result in a raging lymphadenopathy with subsequent abscessation.

68

A 12-year old Quarter Horse gelding presented to you for acute diarrhea, mild colic signs and moderate neurologic signs. Upon initial examination, neurologic signs consisted of head pressing, ataxia, recumbency and general lethargy. The vital parameters included a heart rate of 60 beats/min, respiratory rate of 16 breaths/min and rectal temperature of 102.8F (39.3 C). You decide to perform a biochemistry profile with the following abnormalities observed:

Lactate: 6.5 mmol/L; (RR 0-2.5 mmol/L)
Glucose: 180 mg/dL; (RR 80-115 mg/dL)
Ammonia: 608 micromol/L; (RR 12-61 micromol/L)
Sodium: 124 mEq/L; (RR 137-145 mEq/L)
Chloride: 86 mEq/L; (RR 95-105 mEq/L)
Creatinine: 3.4 mg/dL; (RR 1-2.1 mg/dL)
BUN: 30 mg/dL; (RR 14-21 mg/dL)

Based on the clinical signs and clinicopathologic data, you suspect the horse has colitis; how would you best explain the neurologic deficits in this case?

a. Neurologic signs associated with hyponatremia and osmotic fluid shifts in the brain

b. Neurologic signs associated with acute renal failure and azotemia

c. Neurologic signs associated with extreme hyperglycemia

d. Neurologic signs associated with hyperammonemia and intestinal disease

e. Neurologic signs associated with hepatic encephalopathy

d. Neurologic signs associated with hyperammonemia and intestinal disease

Ok, admittedly this is a tough question, but we do not want to make them too easy. Hyperammonemia has been associated with intestinal disease in horses. The exact cause of the neurologic signs and disease process is unknown, but it is presumed to result from excessive ammonia production within the intestinal tract. This overwhelms the ability of the liver to metabolize ammonia, and subsequently causes the development of encephalopathic signs, such as those reported in this question.

Diarrhea is a common concurrent problem suggesting a possibility that overgrowth of ammonia producing bacteria causes an elevated blood ammonia. In regards to the other possible answers, hyponatremia can cause neurologic deficits if the sodium is very low (100-105 mEq/L), so the sodium of 124 mEq/L in this question rules that option out. The mild azotemia and hyperglycemia are unlikely to cause neurologic deficits and there is no other evidence to support hepatic disease.

69

What is the most commonly reported tumor in the bladder of a horse?

a. Squamous cell carcinoma

b. Lymphosarcoma

c. Prostatic carcinoma

d. Transitional cell carcinoma

a. Squamous cell carcinoma

he most common tumor of the kidney in a horse is renal carcinoma.

70

A horse presents with urticaria, edema of the extremities, petechiation of the mucous membranes, and a stiff gait. On physical exam, you suspect the horse to have purpura hemorrhagica. Which of these abnormalities is associated with purpura hemorrhagica?

a. Thrombocytopenia

b. Anemia

c. Prolonged PT and PTT

d. Hypoproteinemia

b. Anemia

Purpura hemorrhagica is a possible sequela of streptococcus equi infection exposure or vaccination. It develops from a Type III hypersensitivity resulting in immune complex deposition in blood vessel walls and vasculitis. Common clinical signs are as described in the question. This is a nonthrombocytopenic purpura (most horses will have a normal platelet count). Common findings include anemia, hyperproteinemia, hyperfibrinogenemia, hyperglobulinemia, and neutrophilia.

71

You diagnose a horse with vesicular stomatitis. What should you do next?

a. Euthanize the horse immediately

b. Notify the state and federal authorities

c. Vaccinate the horse

d. Start the horse on anti-viral medications

b. Notify the state and federal authorities

The correct answer is notify the state and federal authorities. Vesicular stomatitis is a disease that must be reported to state and federal authorities. There is no specific treatment for the disease. Secondary infections should be treated symptomatically.

72

What is the main disadvantage of giving xylazine to a horse with acute colic?

a. Inhibition of intestinal motility

b. Laminitis

c. Cardiac arrhythmias

d. Masking of clinical signs and the need for surgical intervention

a. Inhibition of intestinal motility

The correct answer is inhibition of intestinal motility. When xylazine is given at 1.1 mg/kg it decreases the motility of the distal jejunum, cecum, and pelvic flexure for over 2 hours. Xylazine can also transiently decrease cardiac output in a potentially hypovolemic horse with colic. Conversely, xylazine is a potent analgesic and can provide immediate relief to a horse with abdominal pain.

73

You are visiting Egypt with a friend and go to a horse farm where you see several horses with swelling in the indentation above the eyes. You recall from your classes in veterinary school that swelling of the supraorbital fossa is a characteristic sign of which of the following exotic diseases?

a. Glanders

b. Surra

c. African Horse Sickness

d. Rift Valley Fever

c. African Horse Sickness

African horse sickness (AHS) is a viral disease of equids that is transmitted by insects, primarily Culicoides. Clinical signs of AHS typically develop 5-7 days after infection and begin with fever and conjunctivitis. Some animals may recover but many go on to develop the pulmonary and/or cardiac form of AHS. The pulmonary form consists of acute respiratory distress, coughing, sweating, and foaming from the nostrils; this form is usually fatal. The cardiac form consists of edema of the head and neck as well as abdominal pain and depression. A characteristic sign is swelling in the indentation above the eyes (also referred to as swelling of the supraorbital fossa). About 50% of animals with the cardiac form die from heart failure while the rest gradually recover after about one week.

Glanders is a bacterial disease caused by Burkholderia mallei (previously known as Pseudomonas mallei). Burkholderia mallei causes 3 different forms of disease; nasal glanders, pulmonary glanders, and cutaneous glanders. The nasal form presents with high fever, loss of appetite and labored breathing with cough. The pulmonary form often develops over several months, beginning as a fever with dyspnea and cough. The cutaneous form develops over several months as nodules develop in subcutaneous tissue along the course of the lymphatics of the legs, costal areas, and ventrum.

Surra is a trypanosomal disease causing primarily fever, weakness, and lethargy.

Rift Valley Fever is a viral disease primarily of ruminants causing influenza-like signs and hepatic lesions.

74

An 8-year old Thoroughbred gelding was presented for acute onset of trembling, excessive recumbency, constant shifting of body weight while standing, and muscle atrophy. The horse is housed in a dry lot with no pasture availability. Diet consists of moderate quality grass hay and sweet feed. The CBC is normal with abnormalities on biochemistry analysis including mild elevation in creatine kinase (CK) and aspartate aminotransferase (AST). Cerebrospinal fluid (CSF) analysis shows no remarkable findings. Based on this information, what disease process do you suspect?

a. Equine Protozoal Myeloencephalitis (EPM, Sarcocystis neurona)

b. Cervical Vertebral Malformation (Wobbler Syndrome)

c. Verminous encephalomyelitis (Halicephalobus deletrix)

d. Equine Herpes Myeloencephalopathy (EHV-1)

e. Equine Motor Neuron Disease (EMND)

e. Equine Motor Neuron Disease (EMND)

The correct answer is EMND. This is a neurologic disease associated with dietary vitamin E deficiency which is believed to contribute to oxidative damage to the CNS. However, the precise pathophysiology is unknown. Retrospective studies have noted that horses with EMND are commonly housed on dry lots with little to no availability to pasture or good quality hay (perhaps contributing to low blood vitamin E concentrations). The clinical signs in this question are classic for EMND whereas horses afflicted with the other options do not typically demonstrate trembling or shifting of body weight.

75

An 11 year old Quarter Horse mare presents to you for progressive neurologic signs over 4 days. The horse has been vaccinated for rabies only.

Signs began with anorexia and depression but moved on to hyperesthesia, propulsive walking and a head tilt. Cerebrospinal fluid analysis shows CSF protein of 75 mg/dl with a mononuclear pleocytosis. Which of these is the most likely diagnosis?

a. Equine protozoal myeloencephalitis

b. Wobbler Syndrome

c. Equine degenerative myelopathy

d. Thiamine deficiency

e. Western Equine Encephalitis

e. Western Equine Encephalitis

The keys to this question are that the horse is unvaccinated for WEE, has a progression of central nervous system signs over several days and characteristic CSF changes.

Another reasonable differential would be rabies, particularly if the horse had not been vaccinated for it.

Equine protozoal myeloencephalitis (or myelitis) can be seen at any age and is caused by Sarcocystis neurona. It should be suspected when a horse has asymmetric neurological signs as it is a multifocal disease of the central nervous system.

Cervical vertebral malformations (Wobbler Syndrome) and degenerative myeloencephalopathy are diseases seen primarily in horses under a year of age. Degenerative myelopathy causes a symmetrical ataxia.

Cerebellar abiotrophy is usually observed in foals which are less than one year of age, particularly 1-6 months of age. It is mostly seen in Arabian, Oldenburg, and Gotland breeds. There is no treatment and signs may be progressive. Diagnosis is based on a good history and clinical signs such as intention tremors, lack of a menace, hypermetria, and ataxia.

Thiamine deficiency in horses usually occurs from ingestion of thiaminase-containing plants (bracken fern) and results in loss of condition and slight uncoordinated movements. If not treated, the disease may progress to cause twitching, tremors and seizures.

76

What is the definitive host for the causative agent of equine protozoal myelitis/myeloencephalitis?

a. Opossum

b. Donkey

c. Horse

d. Wildebeest

e. Raccoon

a. Opossum

The correct answer is opossum. This is a must-know fact. The opossum is the definitive host for Sarcocystis, the causative agent of equine protozoal myelitis.

77

Nine out of 100 adult cattle are found weak, depressed, and staring into space. On physical exam, they are found to be pale, icteric, and febrile. None of them have hemoglobinuria. The nine cattle all arrived at the ranch approximately one month ago. What is your most likely diagnosis?

a. Anaplasmosis

b. Leptospirosis

c. Bacillary hemoglobinuria

d. Anthrax

a. Anaplasmosis

The correct answer is Anaplasmosis. The causative agent is Anaplasma marginale. The clinical signs are fairly straight forward, and you need to pick up on a couple key features. The fact that new adults are sick is one feature because cattle are resistant to clinical Anaplasmosis as calves. Also, it should be remembered that hemoglobinuria with Anaplasmosis is never seen because it is all extravascular hemolysis. Since there is no hemoglobinuria, leptospirosis, bacillary hemoglobinuria, and anthrax can be ruled out. Additionally, icterus with anthrax is not seen.

78

What is the treatment for a horse with a Streptococcus equi abscess?

a. Lance and drain the abscess

b. Non-steroidal anti-inflammatory drug administration

c. Corticosteroid administration

d. Systemic antibiotic administration

a. Lance and drain the abscess

Antibiotics should only be used early on in the infection before abscessation or in cases where the abscess has become internal (bastard strangles).

79

You are visiting a horse farm to evaluate a horse with seborrheic lesions of the pastern and mild lameness. The owner notes that his horses have had problems with "Scratches" in the past. Which of the following management recommendations would be helpful in preventing this problem?

a.  Keep the horses in a dry and clean environment

b. Keep the horses in an insect-free environment

c. Keep the horses on a regular deworming regimen

d. Keep the horses away from the sun during the hottest hours of the day

a.  Keep the horses in a dry and clean environment

Scratches is a condition of chronic seborrheic dermatitis of the palmar/plantar aspect of the pastern. The condition is sometimes referred to by several other names including "grease heel", "dermatitis verrucosa", "dew poisoning" and "mud fever". It is not specific to the underlying infectious cause but the condition is generally associated with horses kept in wet or muddy environments.

Treatment involves removing the horse from the wet environment, clipping the surrounding hair, and gently washing and cleaning the area with a disinfectant followed by careful drying. Topical ointments or astringent dressings may sometimes be used. The best prevention is to keep horses in a dry and clean environment and maintain good hygiene practices.

80

You are examining a 6-year old Thoroughbred gelding for acute onset of diarrhea on a warm summer day. Upon physical examination, tachycardia and fever are present along with severe diarrhea. You also notice signs of lameness in the front feet suggestive of laminitis. What is a cause of diarrhea that is seasonal and is associated commonly with laminitis?

a. Corynebacterium pseudotuberculosis

b. Neorickettsia risticii (Potomac Horse Fever)

c. Clostridium sordellii

d. Salmonella typhimurium

b. Neorickettsia risticii (Potomac Horse Fever)

Neorickettsia risticii commonly causes diarrhea in the warmer summer months and is observed in horses stabled near bodies of water. Although a trematode vector is suspected, the exact pathogenesis remains an area of study. The treatment is oxytetracycline. While many causes of diarrhea can result in laminitis, PHF has been associated with laminitis frequently. Salmonella can also result in the clinical signs noted but is not restricted by season.

81

How is equine influenza transmitted?

a. Venereally

b. Blood-sucking arthropods

c. Aerosol

d. Through bite wounds

c. Aerosol

Equine influenza is an orthomyxovirus and is spread in respiratory secretions of infected animals. It can be endemic in areas or spread as an epidemic because it is highly contagious.

82

A 4-year old Standardbred stallion presents to you in the afternoon with a recent onset of lameness. The owner reports that in the early morning, feed was delivered and the horse apparently got into a bag of grain. On exam, you note heat over the hoof wall and coronary band in the front feet and a very strong digital pulse. The horse is tremoring and sweating. A hoof tester reveals pain over the sole at the toe and the horse is sensitive to tapping on the hoof wall. What treatment is most appropriate?

a. Induce vomiting with xylazine and the administer activated charcoal by stomach tube

b. Administer 1 gallon of saline by stomach tube and give an injection of dexamethasone

c. Administer intravenous fluids, penicillin, and gentamycin

d. Attempt to empty any grain out of the stomach via NG lavage of stomach, administer NSAIDs and start IV fluids

e. Administer neomycin and lactulose by stomach tube and cold pack the feet

d. Attempt to empty any grain out of the stomach via NG lavage of stomach, administer NSAIDs and start IV fluids

The clinical presentation is consistent with a case of acute laminitis secondary to grain overload. Acute laminitis is frequently associated with excessive ingestion of carbohydrates, grazing of lush pastures, and/or excessive exercise.

Acute laminitis more commonly affects the front feet but can affect all four. Local heat and pain are usually detected as well as bounding digital pulses. Pain may also manifest as tachycardia, muscle tremors, or sweating.

The goals of treatment are to prevent further development of laminitis, reduce pain, and reduce other complications from laminitis. Acute laminitis is considered a medical emergency and treatment should be initiated as soon as possible. When a horse is suspected of grain overload, administration of mineral oil by stomach tube acts as a laxative and decreases absorption of toxic material from the gastrointestinal tract. Other recommended treatments include intravenous fluids, parenteral antimicrobials, anti-inflammatory drugs (such as flunixin meglumine or phenylbutazone), and hyperimmune serum or plasma. It is also recommended to place the horse in a stall with soft flooring. Other treatment considerations include heparin, phenoxybenzamine, and heart-bar shoeing. There are some practitioners who recommend cold packs but there is conflicting evidence that hot packs may be more beneficial. Corticosteroids are contraindicated.

83

Newly formed type III collagen is eventually replaced by what permanent type of collagen?

a. Type I

b. Type II

c. Type III collagen is never placed

d. Type IV

a. Type I

The newly formed type III collagen is eventually replaced by type I collagen; however, the replacement is never complete. This process takes between 8-11 months.

84

What is the most common slab fracture in the horse?

a. Accessory carpal bone

b. Central tarsal bone

c. Radial carpal bone

d. Intermediate tarsal bone

e. Third carpal bone

e. Third carpal bone

Chip fractures of the radial carpal bone and radius are common and slab fractures are most common in the third carpal bone. Slab fractures of the central tarsal bone and third tarsal bone do occur but less frequently than in the carpus.

85

What is the average percent of gross production paid to an equine practitioner that is paid exclusively on a percent production basis?

a. 40

b. 35

c. 12

d. 18

e. 25

e. 25

Most equine practitioners should earn 25-30% of their gross intake; the average is about 26%. The national board examination will ask a few basic practice management questions that you should be prepared for.

86

An 18-year old Miniature Horse mare is presented with signs of lethargy, anorexia and mild diarrhea of 5 days duration. Upon physical examination, the mare is quiet and lethargic with a heart rate of 56 beats/min, respiratory rate of 16 breaths/min and rectal temperature of 102.8F (39.3 C). The mare postures to urinate but only produces a small volume of urine. In addition, intestinal borborygmi are slightly increased and loose feces is noted staining the tail. You suspect the mare has colitis, thus prompting collection of blood for a CBC and chemistry profile. After leaving the blood on the counter top for a few minutes prior to submission to the laboratory, you note the unusual appearance of the sample (see image). Based on the history and clinical examination, what would be the most likely abnormal clinicopathologic data measured from your blood samples?

a. Hyponatremia, hypochloremia and hypokalemia suggestive of acute kidney injury

b. Elevations in serum triglycerides, gamma glutamyl transpeptidase (GGT), and sorbital dehydrogenase (SDH) suggestive of hyperlipemia and hepatic lipidosis

c. Elevations in serum fatty acids and cortisol along with hypoglycemia suggestive of pituitary pars intermedia dysfunction (equine Cushing's syndrome) with secondary colitis

d. Neutropenia, hyponatremia and metabolic alkalosis suggestive of colitis and pre-renal azotemia

b. Elevations in serum triglycerides, gamma glutamyl transpeptidase (GGT), and sorbital dehydrogenase (SDH) suggestive of hyperlipemia and hepatic lipidosis

The most likely clinicopathologic changes that you would observe are elevations in serum triglycerides, GGT, and SDH. Unlike other larger sized horses, Miniature horses are susceptible to the development of hyperlipemia and hepatic lipidosis as a result of anorexia; the anorexia typically results from a primary disease, in this case mild colitis. Because of the negative energy balance, fats are mobilized in excess resulting in the opaque appearance of the serum.

The other answers have one incorrect variable within the response: colitis is associated with metabolic acidemia, acute kidney injury is associated with hyperkalemia, and equine Cushing's syndrome is associated with hyperglycemia.

87

You are treating a colicky 8-year old horse and pass a stomach tube to assess gastric reflux. The 20 liters of reflux is hemorrhagic, orange-brown in color, and foul-smelling. On physical exam, you find T=101.5F (38.6 C), HR=70, and RR=35 and overall depressed attitude. There are few auscultable gut sounds. Oral mucous membranes are injected. On rectal exam, there are multiple dilated fluid-filled loops of bowel palpated. Peritoneal fluid is serosanguinous with a 3.5 gm/dl protein and a WBC count of 7000. After decompressing the stomach, the horse appears less painful, but remains depressed. Based on these findings, what is the best tentative diagnosis?

a. Impaction colic (large bowel impaction)

b. Duodenitis-proximal jejunitis

c. Verminous arteritis caused by strongylus vulgaris

d. Large bowel torsion

e. Acute small intestinal obstruction

Q image thumb

b. Duodenitis-proximal jejunitis

Duodenitis-proximal jejunitis, also known as either anterior enteritis, or proximal enteritis best fits this case because of the characteristic reflux, fever, peritoneal fluid characteristics, rectal findings, the depression and relatively less pain than would be expected with an obstruction. The cause is still uncertain, but a relationship of this disease to positive cultures of reflux for Clostridium difficile has been found. Typically these cases are treated medically, which would include repeated decompression of the stomach, IV fluids, replacement of electrolyte deficiencies, analgesics and correction of any acid-base abnormalities.

88

A one-month old foal is suffering from diarrhea. The foal is depressed, anorectic, and has a watery diarrhea. Bloodwork abnormalities are consistent with electrolyte loss from diarrhea, dehydration, and a stress leukogram. Which of the following viruses is most likely to result in this clinical presentation?

a. Flavivirus

b. Rotavirus

c. Calicivirus

d. Coronavirus

b. Rotavirus

The correct answer is rotavirus. Rotaviruses are the most common viral cause of diarrhea in foals. Rotavirus will destroy absorptive intestinal cells in the small intestine thus causing a malabsorptive diarrhea. As with almost all viral diseases, treatment is supportive.

89

You are presented with a 7-year old Thoroughbred gelding with persistent epistaxis (see image). Which medication would be appropriate to administer to promote hemostasis?

a. Aminocaproic Acid

b. Aspirin

c. Low-Molecular Weight Hepatin (LMWH)

d. Tissue Plasminogen Activator (tPA)

Q image thumb

a. Aminocaproic Acid

Aminocaproic acid is the only anti-fibrinolytic medication listed that may promote hemostasis. Aminocaproic acid binds and inhibits plasminogen activation thereby promoting clot maintenance and stabilization. The other medications would be considered fibrinolytics (tPA) or anti-coagulants (LMWH, aspirin).

90

Which of these combinations should not be used in horses?

a. Flunixin meglumine and medetomidine

b. Prednision and omeprazole

c. Flunixin meglumine and phenylbutazone

d. Phenylbutazone and trimethoprim sulfa

c. Flunixin meglumine and phenylbutazone

The correct answer is flunixin meglumine and phenylbutazone. Simultaneous administration of two NSAIDS increases the likelihood of gastric ulceration.

91

An 18 year old mare presents with a head tilt, circling, and nystagmus with the fast phase to the left. Where is the lesion most likely located?

a. Not enough information

b. Left side

c. Bilateral involvement

d. Right side

d. Right side

The correct answer is right side. Although this is not right 100% of the time, the fast phase of nystagmus tends to go away from the lesion. The direction of nystagmus is named after the fast phase. So be careful, this can get a little confusing. In addition, if this question had provided information as to which direction the head tilt and circling were occurring, you would be that much more confident in localizing your lesion (ex. right-side head tilt or circling would be a right-sided lesion). Sometimes you may have paradoxical vestibular disease, in which the lesion does not follow the rules, and the lesion is on the opposite side of what is expected; however, this is rare. This is usually caused by destruction of the cerebellopontine angle or flocculonodular lobe.

92

A 15-year old Quarter Horse gelding is presented for a chronic history of right forelimb lameness. Upon examination of the radiograph (see image), what is the most distal diagnostic nerve block necessary to desensitize the source of lameness?

a. Abaxial Sesamoid Nerve Block

b. Palmar Digital Nerve Block

c. Palmar Metacarpal Nerve Block (low four points)

d. Subcarpal Nerve BLock (high four point)

Q image thumb

a. Abaxial Sesamoid Nerve Block

First, you must determine that there is osteoarthritis of the pastern joint (proximal interphalangeal joint). Observe the periosteal bone proliferation and sclerosis along the medial side of the joint along with collapse of the medial joint space.

Next, it is important to know what locations are blocked by the various perineural injections. You are likely to see at least one question on the board exam in regard to nerve blocks.

The palmar digital nerve block typically blocks the palmar part of the foot; the abaxial block desensitizes the foot and proximal interphalangeal (pastern) joint; the low four point block desensitizes the foot, pastern and fetlock joint; and the subcarpal block desensitizes the metacarpal region and below. Thus, the lowest block that would likely desensitize the area in question is the abaxial sesamoid block.

A image thumb
93

A horse presenting for discharge around the ear should be assessed for this condition.

a. Demodex

b. Sarcoptes

c. Tooth root abscess

d. Dentigerous cyst

d. Dentigerous cyst

The correct answer is dentigerous cyst. This occurs as a result of having tooth germ tissue in the ear. Usually, a swelling at the base of the ear and observe a seromucoid discharge can be identified. Treatment is surgical removal of the tissue.

94

Salmonella typhimurium is a _________________

a. Gram positive obligate aerobe

b. Gram negative facultative anaerobe

c. Gram negative obligate anaerobe

d. Gram negative obligate aerobe

b. Gram negative facultative anaerobe

The correct answer is gram negative facultative anaerobe. In horses, it primarily infects the cecum and proximal colon.

95

A client presents a horse that was found dead in the pasture. The horse was normal yesterday. On examination, you note cherry red mucous membranes and an almond smell to the horse. What is the most likely diagnosis?

a. Black walnut toxicity

b. Rhododendron toxicity

c. Cyanide toxicity

d. Carbon monoxide toxicity

c. Cyanide toxicity

The correct answer is cyanide toxicity. Cyanide does not allow hemoglobin to release oxygen, thus causing the cherry red lips. It is found in cherries, chokecherries, arrow grass, and Sudan grass. Large amounts must be consumed. There is a bitter odor of almonds to the GI tract with this toxicity. Treatment is sodium nitrate and sodium thiosulfate. Prognosis is poor due to the rapid onset. Carbon monoxide can cause cherry red mucous membranes but would not cause the almond smell.

96

Equine infectious anemia is caused by what type of organism?

a. Fungus

b. Protozoan

c. Rickettsia

d. Virus

e. Bacteria

d. Virus

The correct answer is virus. Equine infectious anemia is caused by a retrovirus that establishes a lifelong infection and causes cyclic anemia and abortions.

97

The modified live vaccine for equine viral arteritis is safe and effective for which of the following?

a. Non-pregnant mares only

b. Stallions only

c. Stallions and non-pregnant mares

d. Foals of less than 6 weeks of age

e. Pregnant mares

c. Stallions and non-pregnant mares

The correct answer is stallions and non-pregnant mares. Since the vaccine is modified live, there is a risk for clinical signs in under developed immune systems such as foals. Immunity will last for 1-3 years, and vaccinated horses cannot be distinguished from infected horses by serology.

98

When should a pregnant mare be vaccinated with equine herpes virus-1?

a. At 1, 3, and 5 months of gestation

b. At 3 and 7 months of gestation

c. At 5, 7, and 9 months of gestation

d. At 2 and 4 months of gestation

c. At 5, 7, and 9 months of gestation

The correct answer is at 5, 7, and 9 months of gestation. Failure to do this will result in an increased chance of abortion. The vaccine only provides immunity for 2-4 months making it necessary to booster every 2 months toward the end of gestation.

99

What breed of horse is predisposed to the development of cerebellar abiotrophy?

a. Thoroughbred

b. Appaloosa

c. Quarterhorse

d. Morgan

e. Arabian

e. Arabian

The correct answer is Arabian. This condition should be suspected in an Arabian horse with cerebellar disease. Signs usually develop after 6 months of age and vary in severity, but usually consist of ataxia, hypermetria, head tremors (intention tremors), and hyperreflexia.

100

All of the following cause Heinz body anemia in the horse except for ___________.

a. Methylene blue

b. Phenothiazine

c. Selenium

d. Red maple leaf

e. Molybdenum deficiency

c. Selenium

The correct answer is selenium. The causes of oxidative denaturation of hemoglobin (Heinz body anemia) in horses include phenothiazines, methylene blue, acetylphenyl hydrazine, low molybdenum diet, rye grass diet, brassica family, onions, and wilted red maple leaves.

101

How is equine viral arteritis transmitted?

a. Transplacentally

b. Tick

c. Venerally

d. Mosquito

c. Venerally

The correct answer is venereally. EVA may also be transmitted via aerosolized secretions. Most infections are asymptomatic in adults, but clinical signs may include fever, lethargy, anorexia, edema, oculo-nasal discharge, and petechia. In foals, severe respiratory distress, leukopenia, thrombocytopenia, and death after 12-24 hours can occur.

102

Failure of closure of the foramen ovale within the first 48 hours of life in a healthy foal will result in _______.

a. Shunting of blood from the left ventricle to the right venticle

b. Shunting of blood from the left atrium to the right atrium

c. Shunting blood from the right atrium to the left atrium

d. Shunting of blood from the right atrium to the ductus arteriosus

c. Shunting blood from the right atrium to the left atrium

The correct answer is shunting of blood from the right atrium to the left atrium. The foramen ovale is a small slit that allows shunting between the right atrium and left atrium in the fetus. Once the foal is born, the lungs expand (right atrial pressure decreases) and the left atrium becomes a higher pressure system than the right. This higher pressure in the left atrium at birth forces the closure of the foramen ovale flap against the septum secundum and, in health, typically fusion of these tissues occurs to permanently close the foramen ovale. However, if the foramen ovale flap does not fuse, this leads to patency. In this case, the flap acts somewhat akin to a one-way valve so when the LA pressure is higher the flap is closed, but when the RA pressure is higher, blood can flow right to left. This occurrence (RA pressure > LA pressure) may happen when the patient coughs, takes a deep breath or sneezes which increases the return of venous blood to the RA.

103

You are examining a 6-year old race horse that has been experiencing decreased performance. On auscultation you note, a slow heart rate of 16 beats per minute with an irregular rhythm consisting of occasional dropped beats. An ECG confirms the presence of a second degree atrioventricular block. Which of the following should you tell the owner?

a. This conduction finding likely indicates serious underlying pathology in the heart and further diagnostic tests are needed

b. This conduction finding is common in racehorses and is unlikely to contribute to poor performance

c. This conduction finding is a common cause of poor performance and is usually effectively treated by quinidine

d. This conduction finding is a common cause of poor performance and is not treatable; the horse should be retired

e. This conduction finding is a life-threatening abnormality and placement of a pacemaker is indicated

b. This conduction finding is common in racehorses and is unlikely to contribute to poor performance

Second-degree atrioventricular block is commonly seen in athletic horses. First-degree and second-degree blocks are considered variations of normal in the horse and are usually associated with high vagal tone. Horses with second-degree atrioventricular block are NOT predisposed to electrical-mechanical disassociation. This is not a cause of poor performance or a concern in horses because high vagal tone is overcome by sympathetic tone during exercise.

104

A 3-year old Appaloosa mare presents with progressive neurologic signs over the past 2 weeks. She has an ataxic, spastic gait, knuckling on the left legs. She also has a right-sided head tilt and atrophy of the temporal and masseter muscles on the right side. There is muscle atrophy of the left gluteal muscles. Based on the most likely diagnosis, which of the following should you tell the owner about the prognosis for this horse with treatment?

a. It is unlikely that treatment will significantly delay the progression of this disease

b. Treatment will likely prevent further progression of the disease but the existing deficits are unlikely to improve

c. Most horses improve with treatment, but relatively few make a complete recovery

d. Most horses recover completely with treatment but a small subset of horses relapse when treatment is discontinued

c. Most horses improve with treatment, but relatively few make a complete recovery

This is a case of Equine protozoal myeloencephalitis. EPM can be tricky to diagnose because the clinical signs can be quite variable but the key findings are the "3 A's", namely asymmetry, ataxia, and atrophy. The onset of clinical signs are frequently gradual but rapid progression is seen in some cases. Differential diagnoses can include cervical vertebral malformation, equine degenerative myeloencephalopathy, equine herpes myeloencephalitis, polyneuritis equi, and verminous myeloencephalitis. However, the asymmetric and multifocal signs as well as the horse's age and gradual onset of signs make EPM the most likely diagnosis.

The prognosis for horses with EPM is often described as variable. Studies show that about 70% of treated horses will improve but only up to 25% recover completely and perform normally. In addition, a subset (5-20%) of horses may improve while undergoing treatment but then relapse when treatment is discontinued. It is unclear whether relapse represents reemergence or persistence of resistant parasite or re-exposure. Based on these features of EPM, the best answer choice of those listed is that most horses improve with treatment but relatively few make a complete recovery.

105

One of your clients recently purchased a horse that she plans to add to her stable. She is concerned about potential exposure of the horse to Streptococcus equi subsp. equi. Which of the following is the most sensitive test for detecting carriers of the disease?

a. Serology for antibodies to S. equi M protein (SeM)

b. PCR of a guttural pouch wash for the S. equi M protein (SeM) gene

c. Guttural pouch culture Columbia CNA (colistin, nalidixic acid) agar with 5% sheep or horse blood

d. Nasopharyngeal culture on Columbia CNA (colistin, nalidixic acid) agar with 5% sheep or horse blood

b. PCR of a guttural pouch wash for the S. equi M protein (SeM) gene

Testing for Streptococcus equi subsp. equi can be complex. The 3 major tests are PCR, serology, and culture. PCR and serology both detect SeM which is an important virulence factor for the bacteria. Culture is best performed on Columbia CNA agar with 5% sheep or horse blood.

While there are pros and cons to each test, the key to answering this question correctly is focusing on the issues of sensitivity and detecting carriers.

PCR is approximately 3 times more sensitive than culture. In general, sampling the guttural pouch is a better way to detect carriers than the nasopharynx because it is where most carriers harbor the organism.

Serology is the best test for assessing exposure but is not a good tool for detecting carriers. This is because antibodies may be elevated after an infection has been cleared or even after vaccination. It may also be falsely negative if an exposure was recent.

To summarize the best uses of culture, PCR and serology:

Culture is the gold standard for diagnosing a horse with an infection.

PCR is best for detecting asymptomatic carriers, establishing infection status prior to or following transport, and to determine the success of elimination of S. equi from the guttural pouch. PCR cannot distinguish live DNA from dead DNA and may have false positives after a cleared infection. Using PCR in combination with culture may be helpful in such an instance.

Serology is best for determining exposure and the need for vaccination as well as for supporting diagnoses of S equi associated purpura hemorrhagica or of bastard strangles.

106

What is the causative agent of Tyzzer's disease?

a. Clostridium difficile

b. Clostridium perfringens

c. Clostridium botulinum

d. Clostridium piliforme

e. Clostridium chauvoei

d. Clostridium piliforme

The correct answer is Clostridium piliforme. This is a motile, filamentous, gram negative, spore forming bacterium. Of note, all Clostridia are categorized as gram positive organisms with the exception of Clostridium piliforme, which is gram negative (yes, Microbiology is confusing). Clinical signs associated with Tyzzer's include depression, anorexia, coma, convulsions, and jaundice. Horses between 6 days and 6 weeks of age are affected; however, most are affected at 1-2 weeks. Affected foals will have elevated liver enzymes, marked hypoglycemia, and acidosis.

107

What is the most common neoplasia seen in the equine stomach?

a. Gastric adenocarcinoma

b. Mesothelioma

c. Squamous cell carcinoma

d. Lymphosarcoma

c. Squamous cell carcinoma

108

A horse presents to you with a corneal ulcer.  You are concerned because it appears to be infected ,as shown in this image.  You perform cytology and find gram negative rods.  What is the most likely organism infecting the corneal ulcer in this horse?

a. Staphylococcus spp.

b. Pasteurella multocida

c. Pseudomonas

d. E. coli

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c. Pseudomonas

The correct answer is Pseudomonas. Pseudomonas is the most common agent causing bacterial keratitis in the horse. The gram negative cytology provides further evidence that it is the likely culprit. Staphylococcus can cause keratitis in horses but is gram positive. E. coli and Pasteurella are not agents that are commonly involved with keratitis in the horse.

109

You are presented a healthy 10-year-old maiden mare for breeding evaluation in January in North America.  On rectal palpation, both ovaries have multiple, small (less than 15mm) follicles and no corpus lutea.  The uterus is flaccid with no edema.  Which one of the following choices is the most likely explanation of the finding in this mare?

a. Seasonal anestrus

b. The mare is in diestrus

c. Estrus has just passed

d. Early pregnancy

e. The mare is too old and now is infertile

a. Seasonal anestrus

Mares are seasonal breeders and enter anestrus in the short-day months of late fall and winter.  In anestrus, the ovaries are inactive with small follicles and no corpus lutea.  During estrus, the uterus softens and multiple follicles form on the ovaries.  During pregnancy, the uterus has good tone.

110

A 6-year old Quarter Horse presents with the lesion seen in the photograph. Which of the following is true regarding equine sarcoids?

a. They usually regress spontaneously without treatment

b. Metastasis is common with advanced lesions

c. Surgical excision is nearly always curative

d. Papillomavirus is believed to play a role in the pathogenesis

Q image thumb

d. Papillomavirus is believed to play a role in the pathogenesis

Sarcoids are one of the most common tumors in horses. They are considered non-metastatic tumors in virtually all cases. For this reason, small lesions are sometimes treated with benign neglect, but they are not expected to regress. More advanced lesions or tumors in certain sites do need to be treated more aggressively. Unfortunately, no single treatment is universally effective. Recurrence rates after surgical excision are approximately 50%. Although there is still controversy surrounding this issue, either bovine papillomavirus or an equine variant is thought by many to play a role in development of these tumors.

111

An 8-year old horse presents for evaluation of ear lesions.  On examination, you note coalescing depigmented and hyperkeratoic plaques on the inner (concave) surface of the pinna bilaterally.  Which of the following treatments is most likely to result in regression of the lesions?

a. Systemic antibiotics

b. Topical imiquimod (Aldara)

c. Environmental insect control

d. Systemic glucocorticoid

b. Topical imiquimod (Aldara)

Aural plaques in horses are caused by papillomavirus and are mechanically spread by insects such as black flies. Lesions do not typically regress but a 2010 study (Veterinary Dermatology; 21(5) 503-509) showed that topical application of imiquimod cream was efficacious in causing resolution of the lesions. Environmental insect control is also a wise recommendation in this case but would not lead to regression of the lesions. Systemic antibiotics or glucocorticoids would not be effective against this viral lesion but glucocorticoids are sometimes used to control clinical signs (pruritus) seen concurrently with these lesions.

112

What is the oldest tooth in the horse

a. Incisor 1

b. Canine

c. Molar 1

d. Premolar 1

d. Premolar 1

The correct answer is premolar 1. This is also known as the wolf tooth and is commonly removed so that bits can be easily fitted to the horse's mouth. This tooth erupts at 5-6 months of age. Molar 1 does not erupt until about one year of age. The canine does not come in until 4-5 years of age. The first permanent incisor is seen at approximately 2.5 years of age.

113

You are examining a 5-year old pony for lethargy, anorexia, and mild intermittent colic.  Upon physical examination, you notice the abnormal finding in the image.  Consumption of which of the following can produce these clinical signs and physical examination findings?

a. Red maple leaves (Acer rubrum)

b. Yellow star thistle (Centaurea solstitialis)

c. Oak leaves and acorns (Quercus sp)

d. Black walnut (Juglans nigra)

Q image thumb

a. Red maple leaves (Acer rubrum)

The sclera appears icteric. In combination with the clinical signs, ingestion of Red maple leaves would result in these signs due to hemolysis and low oxygen content of the blood. Oak is toxic but causes diarrhea and abdominal pain, whereas Black walnut is associated with laminitis. Yellow star thistle causes nigropallidal encephalomalacia resulting in CNS signs.

114

The most commonly isolated equine pathogen is Streptococcus zooepidemicus.  Which of the following is the least expensive antibiotic which is an effective treatment?

a. Metronidazole

b. Amikacin

c. Doxycycline

d. Gentamicin

e. Penicillin

e. Penicillin

The only disadvantage is that procaine penicillin needs to be injected and the individual horse may become sore and needle shy.

115

If concerned about the liver function of a neonatal foal, which antibiotic does not undergo extensive hepatic metabolism?

a. Trimethoprim

b. Erythromycin

c. Chloramphenicol

d. Ampicillin

e. Rifampin

d. Ampicillin

The correct answer is ampicillin. Ampicillin is excreted by the kidneys and without hepatic metabolism. All other answer choices undergo extensive hepatic metabolism before being excreted.

116

In the Spring of 2001, a syndrome later termed Mare Reproductive Loss Syndrome, MRLS, occurred in central Kentucky. This syndrome was characterized by early and late-term fetal loss, fibrinous pericarditis, neonatal foal death and unilateral uveitis. Which of the following was incriminated as a likely potential cause of MRLS?

a. Exposure or ingestion of black walnut

b. Exposure or ingestion of eastern tent caterpillars

c. Exposure or ingestion of blister beetles

d. Exposure of ingestion of red maple leaves

e. Exposure or ingestion of Japanese yew

b. Exposure or ingestion of eastern tent caterpillars

The correct answer is exposure or ingestion of eastern tent caterpillars. The exact pathogenesis of MRLS is still unknown, but the presence of eastern tent caterpillars was strongly associated with the disease. Later, experimental studies in which pregnant mares were exposed to or fed eastern tent caterpillars resulted in early and late fetal loss.

117

A yearling horse has fever of 103F (39.4 C), depressed attitude, and a ruptured submandibular abscess draining thick white non-odorous pus (see image). What is the most likely cause of these signs?

a. Rhodococcus equi

b. Rhinopneumonitis

c. Strangles

d. Guttural pouch empyema

e. Histoplasma capsulatum

Q image thumb

c. Strangles

Strangles is caused by Streptococcus equi. It is a highly contagious disease, especially to naive young animals.

A image thumb
118

How many paris of ribs does the normal horse have?

a. 21

b. 13

c. 18

d. 10

c. 18

The horse has 18 pairs of ribs

119

A 3-month-old paint colt presents to you after flipping over backward while being led by the owner the previous day. Clinical signs at the time of presentation are shown in the image (head tilt, flaccid ear, muzzle deviation). Based on the history and clinical signs, what cranial nerves are damaged and what is the most likely diagnosis?

a. Cranial nerves VII and VIII (left side); fracture of the basiphenoid bone

b. Cranial nerves V and VIII (left side); fracture of the sphenoid bone

c. Cranial nerves VII and VIII (right side); fracture of the basisphenoid bone

d. Cranial nerves V and VII (right side); atlanto-occipital malformation

e. Cranial nerves V and VII (left side); atlanto-occipital malformation

 

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a. Cranial nerves VII and VIII (left side); fracture of the basiphenoid bone

The correct answer is damage to cranial nerves VII (facial nerve) and VIII (vestibular nerve) on the left side caused by fracture of the basisphenoid bone. This is a common injury when a fractious young foal rears up and falls backward on the poll. The basisphenoid bone becomes injured resulting in injury to cranial nerves VII and VIII. Damage to the facial nerve results in the muzzle deviation (opposite direction of the side of injury, in this case deviated to the right), ptosis of the left eye and drooping of the left ear. Damage to the vestibular nerve results in the head tilt.

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120

The most common equine tumor is a locally aggressive fibroblastic tumor of the dermis and subcutis with a variable proliferative epithelial component.  What is this tumor commonly called?

a. Mastocytosis

b. Cutaneous lymphoma

c. Sarcoid

d. Pemphigus

e. Pythiosis

c. Sarcoid

The sarcoid comes in many forms and can be difficult to eliminate in many cases. Bovine papillomavirus types 1 and 2 are associated with this tumor of horses.

121

What other species of animal would you expect to find around horses that are showing signs of Haematobia irritans infestations?

a. Canine

b. Bovine

c. Feline

d. Porcine

b. Bovine

The correct answer is bovine. Haematobia irritans requires cattle feces to reproduce, although the adults will feed on horses, sheep, and goats as well. The flies spend all of their life cycle on the host except when reproducing and cannot fly much further than 10 miles off of the host.

122

You are asked to perform a necropsy on a 17-year old Standardbred mare on a large horse ranch. Although not related to the cause of death, you notice the parasite shown in the image within the stomach. You tell the owner that this parasite is also responsible for the eggs that he sees seasonally on the hair of the front legs of his horses. The owner asks what should be done about this. You discuss the importance of promptly cleaning up feces and transporting feces away. In addition, which of the following is the most appropriate recommendation for ongoing control of this parasite?

a. Administer fenbendazole twice annually, once in the early summer and again in later summer

b. Administer ivermectin twice annually, once in the early spring and again in the winter

c. Administer fenbendazole twice annually, once in the early sping and again in the fall

d. There is no need to treat these parasites because they are not associated with disease in horses

e. Administer ivermectin twice annually, once in the early summer and again in the fall

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e. Administer ivermectin twice annually, once in the early summer and again in the fall

This case describes the appearance of the horse bot fly, Gasterophilus spp. Gasterophilus is frequently asymptomatic but treatment is recommended because bots can cause gastritis and frequently are a source of annoyance and stress to horses. In addition, the larval instars can cause stomatitis, and colic.

The key to answering this question regarding optimal treatment and management is an understanding of the Gasterophilus life cycle. Gasterophilus undergoes complete metamorphosis, including three larval instars and only one generation is produced per year. The general cycle typically begins with the female ovipositing 150-1,000 eggs on a horse during the early summer months directly on single hairs of the horse's front legs (especially around the cannon bone area) as well as the abdomen, flanks, and shoulders. The eggs are approximately 1-2mm long and are pale to grayish yellow attached near the tip of the hair.

The eggs develop into first instar larvae within five days and they are stimulated to emerge by the horse licking or biting at the fully developed eggs. The larvae then crawl to the mouth or are ingested and subsequently bury themselves in the tongue or gingiva and remain for approximately 28 days. The larvae molt to the second stage and move into the stomach. The second and later third stage larvae typically attach to the lining of the stomach in the non-glandular portion near the junction of the esophageal and cardiac regions where they remain immobile for the following 9 to 12 months.

The third instar larvae are relatively large, between 1-2cm long with a rounded body, narrow, hooked mouthparts, and spines. The hooked mouthparts enable the larvae to securely attach to the lining of the stomach and intestinal tract. After the third instar larvae have matured, they detach from the gastrointestinal tract and pass from the horse's body in the feces. The larvae burrow into the soil or dried manure where they pupate and remain for the next one to two months. This stage of the life cycle occurs between late winter and early spring.

Based on this life cycle, the recommended management protocol is typically to treat with an avermectin to control adults and all larval stages by administering in the early summer, shortly after any eggs are seen and again in the fall at the end of the botfly season. Such a control program will substantially reduce fly numbers.

123

Which of the following is true about demodectic mange infections in horses?

a. The infection can be treated with Amitraz

b. The head, neck, and withers are the most commonly affected area

c. The disease is very pruritic

d. The disease commonly occurs in young foals

e. Skin scraping are usually unrewarding

b. The head, neck, and withers are the most commonly affected area

The correct answer is the head, neck, and withers are the most commonly affected areas. Demodicosis in horses is a rare disease and is not typically pruritic in nature. A skin scraping is the diagnostic test of choice, and there is no satisfactory treatment for the disease. Amitraz can be used to treat dogs with Demodex, but it causes colic and death in horses.

124

Which of these urine specific gravities would you most likely find in a horse with chronic renal insufficiency and moderate azotemia?

a. 1.001

b. 1.024

c. 1.012

d. 1.042

e. 1.004

c. 1.012

The correct answer is 1.012. Isosthenuria would be expected in any horse with chronic renal insufficiency that is causing azotemia. Isosthenuria is typically defined by a urine specific gravity of about 1.008-1.015.

125

A 2-year old Thoroughbred race horse presents for lameness evaluation. The trainer reports that the lameness has been slowly progressive over the past 3 weeks. You observe the horse walk and see a short, choppy gait in the front legs. There is swelling over the front of both fetlock joints and palpation and flexion of the fetlocks elicits pain. Radiographs show no evidence of new bone formation in the fetlock. You diagnose the horse with osselets (periostitis of the distal dorsal cannon bone). What is the best treatment recommendation?

a. Rest, phenylbutazone, and intra-articular injections of sodium hyaluronate

b. Deep digital flexor tenotomy

c. Arthrodesis of the fetlock

d. Palmar digital neurectomy

a. Rest, phenylbutazone, and intra-articular injections of sodium hyaluronate

Cases of osselets that are caught before the development of osteoarthritis often respond completely to medical management consisting of rest, anti-inflammatories (such as phenylbutazone) and intra-articular injections of sodium hyaluronate or polysulfated glycosaminoglycans (Adequan).

Fetlock arthrodesis is reserved for more advanced fetlock injuries. Deep digital flexor tenotomy is used to treat certain cases of chronic laminitis. Palmar digital neurectomy is used to treat navicular disease and results in desensitization of the heel.

126

Which of the following is the most plausible reason for finding an elevated serum level of gamma glutamyltransferase (GGT) in a 7-year old horse?

a. Hemolysis

b. Cardiomyopathy

c. Acute skeletal muscle injury

d. Renal disease

e. Chronic liver disease

e. Chronic liver disease

GGT is a marker of hepatobiliary disorders and cholestasis in large animals.

127

You are called to examine an 18-year old horse with the complaint of not shedding out this spring and having less energy. The horse is hirsute, has loss of muscle mass, and has evidence of chronic laminitis. The owner also complains that the animal drinks twice as much as her other horses and seems to urinate a lot. Based on this history and these signs, what diagnosis should be at the top of your list of differential diagnoses?

a. Adrenal hyperplasia

b. Hypervitaminosis D

c. Parathyroid gland malfunction

d. Pituitary pars intermedia dysfunction

e. Hyperthyroidism

d. Pituitary pars intermedia dysfunction

This disorder used to be called equine Cushing's. This condition is a result of hypertrophy, hyperplasia, and micro- or macroadenoma of the pituitary pars intermedia that secretes increased amounts of propiomelanocortin peptides. Adjacent pituitary tissues are compressed and secrete less of some other peptides. Data suggest that horses with this disease have hypothalamic dysfunction and decreased amounts of dopamine

128

Clinical signs associated with bracken fern ingestion in a horse include which of the following?

a. Dysphagia

b. Anemia

c. Dyspnea

d. Opisthotonos

e. Colic

d. Opisthotonos

The correct answer is opisthotonos. Bracken fern contains thiaminase, leading to thiamine (vitamin B1) deficiency. Clinical signs include anorexia, weight loss, incoordination, convulsions, wide-based stance, opisthotonos, and death.

129

Which of these toxins might lead to hemoglobinuria in a horse?

a. Onions

b. Oleander

c. Cantharidin

d. Astragalus

a. Onions

The correct answer is onions. Onions can cause Heinz body anemia through oxidative damage to red blood cells and result in hemoglobinemia and hemoglobinuria.

130

Approximately how long does it take for spermatogonia to mature to sperm in the stallion?

a. 5 days

b. 60 days

c. 30 days

d. 14 days

b. 60 days

The correct answer is 60 days. For this reason, a stallion with poor quality semen should be re-evaluated in 2 months before making a final judgment.

131

The image shows a 2 month old Thoroughbred foal with a limb abnormality. What is the name of this abnormality?

a. Osteoarthritis

b. Septic arthritis

c. Carpus valgus

d. Carpus varus

e. Subchondral bone cyst

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c. Carpus valgus

This is one of the most common angular limb deformities that occurs in foals, usually as the result of asynchronous growth of the metaphyseal and epiphyseal growth plates.

132

Endotoxemia is a term applied when an animal exhibits multiple adverse clinical signs including one or more of the following: fever or hypothermia, leukopenia, tachycardia, tachypnea, obtundation, and a change in gut motility. These physiologic effects are caused by what?

a. DNA from Gram negative bacteria

b. Exotoxins from Clostridial organisms

c. An adverse reaction to aspirin, phenylbutazone or other NSAIDs

d. Bacterial lipopolysaccharide

e. Cell wall components of Gram positive bacteria

d. Bacterial lipopolysaccharide

The cell walls of all Gram negative bacteria contain varying amounts of lipopolysaccharide, which in turn varies in its potency to create adverse reactions in animals. The signals have evolved on monocytes and macrophages to warn the animal when a Gram negative bacterium has gained access. When the reaction to this signal is overzealous, a cascade of adverse physiologic reactions can occur.

133

For neonatal isoerythrolysis to occur, which of these pairs must mate?

a. Stallion negative for Qa and mare positive for Qa

b. Stallion positive for Qa and mare negative for Qa

c. Stallion positive for Qa and mare positive for Qa

d. Stallion negative for Qa and mare negative for Qa

b. Stallion positive for Qa and mare negative for Qa

The correct answer is stallion positive for Qa and mare negative for Qa. For neonatal isoerythrolysis to occur, the mare must develop antibodies to the foal's red blood cell antigens. Aa and Qa are the two antigens most frequently implicated in this condition. For this condition to occur, the foal must inherit the Aa or Qa antigen from the stallion, and the mare must be negative for the antigen (if she was positive, meaning she has the Qa antigen on her RBCs, she would not make antibodies against it). Then, when the mare becomes exposed to the foal's red blood cell antigens, she makes antibodies. When she passes these antibodies to the foal through colostrum, an acute hemolytic event will occur in the foal. In most cases, the first time a mare has a foal with the antigen, she will not produce sufficient antibodies to cause severe damage to the foal. Therefore, this condition is usually seen in multiparous dams or in mares that have previously had a blood transfusion that exposed them to the red blood cell antigens.

134

Which of the following large animal diseases is most likely to be the cause of vesicular lesions and ulcerations in the mouths of cattle and horses in the United States?

a. Vesicular stomatitis

b. Rinderpest

c. Foot-and-mouth disease

d. Vesicular exanthema

e. Swine vesicular disease

a. Vesicular stomatitis

None of the other choices have occurred in the US in many decades.
VS is a rhabdoviral disease which occurs in cycles in the USA, Mexico and South America, and can affect cattle, horses, donkeys, mules and pigs. In addition to the mouth, lesions can occur on teats and interdigital areas as well. Morbidity can be high, but mortality is usually low. The NJ serotype has been found in the US every year. Both migratory grasshoppers and the plants they eat can be infected with VS virus. Biological vectors include the midge Culicoides sonorensis, sand flies, and black flies. This is a reportable disease.

135

A 9-day old foal is experiencing mild diarrhea. What is the most likely diagnosis?

a. Lactose intolerance

b. Rhodococcus equi

c. Foal heat diarrhea

d. Clostridium perfringens

c. Foal heat diarrhea

The correct answer is foal heat diarrhea. Although any of these answers could be correct, sometimes this is all you have to go on for some exam questions. To answer this question you need to know at what time periods foals get what diarrhea and the severity.

Foal heat diarrhea is mainly seen at the age of 7-14 days and is usually very mild in nature, making this the best answer choice.

Rhodococcus equi will result in diarrhea in foals that are between the ages of 1-4 months; however, remember that this organism primarily causes respiratory disease, so look for that too.

Clostridium perfringens Types A, B, and C will usually result in an acute to peracute diarrhea in foals, leaving most of them dead in 48 hours if treatment is not instituted.

Primary lactose intolerance is rare in foals.

136

Phenylbutazone toxicosis in horses is known for resulting in ________.

a. Left dorsal colitis

b. Right dorsal colitis

c. Left ventral colitis

d. Right ventral colitis

b. Right dorsal colitis

The correct answer is right dorsal colitis. Concurrent renal medullary crest necrosis may also occur with NSAID toxicity.

137

A 3-year-old Standardbred gelding presents with epiphora, blepharospasm, and severe pain of the right eye (see image). There are numerous treatment options. Which medication would be contraindicated for this case?

a. Tropicamide

b. Neomycin and polymyxin B and dexamethasone (Neo-Poly-Dex)

c. Tobramycin

d. Banamine

e. Serum

f. EDTA

Q image thumb

b. Neomycin and polymyxin B and dexamethasone (Neo-Poly-Dex)

The correct answer is Neo-Poly-Dex. This is an illustration of a melting ulcer. Any corneal ulcer, whether it is superficial or deep, can be perpetuated by steroid use. Steroids increase the protease activity causing the "melting"; therefore, one of the primary goals in managing corneal ulcers is to decrease protease activity by using EDTA and serum. Further, aggressive topical antibiotic use is essential. Tobramycin, gentamicin, neomycin-polymyxin B-bacitracin, among others are appropriate. Intravenous banamine is the drug of choice for ocular pain and inflammation in horses. Tropicamide is used for its mydriatic and cycloplegic effect because all animals with corneal ulcers have uveitis. Atropine is an alternative to tropicamide. It is important to note that, even though atropine has a longer duration of action than tropicamide, atropine must be used with extreme caution in horses as it may potentiate colic

138

Claviceps purpura is the causative agent for which of the following?

a. Aflatoxicosis

b. Moldy corn poisoning

c. Moldy sweet clover poisoning

d. Ergotism

d. Ergotism

The correct answer is ergotism. Claviceps purpura is a parasitic fungus found on rye, oats, wheat, and Kentucky bluegrass. Its toxicity comes from alkaloids and causes vascular constriction, thrombosis, gangrene, and vomiting, colic, diarrhea, and constipation. Diagnosis is made by identifying ergot on the grain.

 

139

What is the earliest day that pregnancy can be diagnosed by rectal palpation in the mare?

a. Day 90

b. Day 45

c. Day 10

d. Day 60

e. Day 25

e. Day 25

The correct answer is day 20. By day 20-30 the vesicle forms as a ventral bulge and thinning to the side of the bifurcation of the uterus. The fetus is usually not palpable until about day 90-120. Ultrasound can be used to diagnose pregnancy as early as 11-14 days. However, we want to know about "rectal palpation".

140

A mare in the last month of gestation develops ventral edema from the udder to the xiphoid. She then becomes acutely painful and tachypneic and does not want to ambulate. What condition did the mare experience?

a. Uterine torsion

b. Colonic torsion

c. Ruptured prepubic tendon

d. Vaginal cystocele

c. Ruptured prepubic tendon

The correct answer is ruptured prepubic tendon. This tendon courses along the ventrum and provides the major support for all the structures in the equine abdomen. It can rupture in late pregnancy, especially in obese draft mares. This is usually preceded by ventral swelling. If such swelling is noted, preventative measures should be taken such as restricting activity and possibly slinging the abdomen to provide support. This condition is very painful to the mare and may affect the ability to increase intra-abdominal pressure during parturition. Assisted parturition by a veterinarian should be strongly considered. A body wall hernia may also result in similar signs as a ruptured prepubic tendon.

141

A 48-hour Paint colt is presented to you for lethargy, irregular facial twitching and prolonged recumbency (see image). The owner reports that the gestation was 343 days and parturition was normal. Upon physical examination, the foal heart rate is 88 beats/min, respiratory rate is 10 breaths/min, and the rectal temperature is 101.2F (38.4 C). The foal is difficult to arouse and appears to have mild intermittent seizure-like activity. The foal can stand briefly but has no suckle response. The CBC and biochemistry analysis are within normal limits for a foal of this age; the arterial blood gas (collected while foal was in lateral recumbency) demonstrates the following results:

pH 7.19 (7.35-7.5)
PO2 78 mmHg (~94 mmHg)
PCO2 80 mmHg (36-46 mmHg)
HCO3 42 mEq/L(24-30 mEq/L)
Ionized Ca++ 1.7 mmol/L (1.4-1.8 mmol/L)

What is your interpretation of this arterial blood gas analysis and what is the most likely cause?

a. Respiratory alkalosis with metabolic compensation caused by bacterial meningitis

b. Respiratory acidosis with metabolic compensation caused by atlantoaxial malformation (OAAM)

c. Respiratory acidosis without metabolic compensation caused by neonatal septicemia

d. Respiratory acidosis with metabolic compensation caused by neonatal encephalopathy  (hypoxic-ischemic encephalopathy)

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d. Respiratory acidosis with metabolic compensation caused by neonatal encephalopathy  (hypoxic-ischemic encephalopathy)

This is a more complicated question that requires evaluation of the entire case. First, recognize the foal's problem list includes: lethargy, hypoventilation, intermittent seizures as well as no suckle response. Next recognize that the arterial blood gas reveals a normal PO2 in a recumbent foal but hypercarbia (respiratory acidosis) with metabolic compensation. Based on these findings, the most likely cause in neonatal encephalopathy.

This disease can arise from hypoxic conditions in utero or during parturition (dystocia, premature placental separation) resulting in a cascade of biochemical derangements within the body. Clinical signs include lethargy, failure to find and nurse from the udder, seizure activity, and in more severe cases damage to the gastrointestinal system and/or kidneys from hypoxia. Many foals are hypercapnic because the respiratory center within the CNS is not operating normal. There can be evidence of infection that complicates the presentation of some foals with neonatal encephalopathy, but in this case the CBC and rectal temperature are normal, making infectious diseases (bacterial meningitis, septicemia) less likely.

You should have some knowledge of what normal arterial blood gas reference intervals are: pH 7.35-7.5; PO2 variable in venous blood; PCO2 around 40 mmHg, HCO3 24-30 mEq/L, iCa++ 1.4-1.8 mmol/L. This is a general range, with each species having slight changes to this range.

142

What is the most likely cause of dysmetria in an Arabian foal?

a. Equine protozoal myeloencephalopathy

b. Cerebellar abiotrophy

c. Otitis media

d. Equine herpesvirus infection

b. Cerebellar abiotrophy

The correct answer is cerebellar abiotrophy. This is a condition seen primarily in Arabian foals and results in ataxia, dysmetria, head tremors (intention tremors), and hyperreflexia. Signs typically develop around 6 months of age.

143

An 8-day old foal presents for diarrhea. What is the most likely cause?

a. Cryptosporidium

b. Strongyloides westeri

c. Strongylus vulgaris

d. Foal heat diarrhea

d. Foal heat diarrhea

The correct answer is foal heat diarrhea. The exact cause of this is unknown and is termed foal heat diarrhea because of the relationship to the occurrence of post foaling estrous in the mare. However, we don't believe it is caused by estrous. It is possible that consumption of grain and hay may play a role in altering the gastrointestinal flora such that diarrhea develops. Foal heat will occur at 7-14 days of age. S. vulgaris and S. westeri will usually cause diarrhea later on in life due to their life cycles. Cryptosporidium may be a cause of diarrhea, but it is also found in healthy foals.

144

Which of these urine specific gravities would you most likely find in a horse with chronic renal insufficiency and moderate azotemia?

a. 1.042

b. 1.012

c. 1.024

d. 1.001

e. 1.004

b. 1.012

The correct answer is 1.012. Isosthenuria would be expected in any horse with chronic renal insufficiency that is causing azotemia. Isosthenuria is typically defined by a urine specific gravity of about 1.008-1.015.

145

146

You are examining a 13-year old Standardbred brood mare 5 hours after parturition. You note that the placenta is still present in the reproductive tract of the mare (see image). What is the most appropriate therapy?

a. Administer oxytocin (IM or IV) and lavage the uterus to facilitate removal

b. Place physical traction on the placenta and remove it manually

c. Administer penicillin (IM) until the placenta is expelled on its own

d. Do nothing; the placenta is not considered retained until 12 hours post-parturition and it will likely be expelled by this time

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a. Administer oxytocin (IM or IV) and lavage the uterus to facilitate removal

147

You examine a 2 year old horse with the complaint of bilateral nasal discharge and lethargy for about a week. The horse has a temperature of 102F (38.9 C), HR 40, and RR 25. The nasal discharge is non-odorous and contains multiple bacteria and neutrophils. The lateral throat area is swollen and tender on palpation. Lateral radiographs reveal fluid lines in the area of the guttural pouches. You submit some of the liquid pus for culture. What treatment is now most indicated?

a. IM tetracycline daily for 2 weeks

b. Systemic erythromycin for one month

c. Systemic treatment with antifungal drugs for 4 weeks

d. Daily catheterization and lavage of the pouches

e. Immediate surgical drainage

Q image thumb

d. Daily catheterization and lavage of the pouches
Irrigation should use saline or saline plus an appropriate and non-irritating antimicrobial drug. Systemic antimicrobial drugs are also used, but the hallmark of successful therapy is lavage and drainage. For inspissated pus or refractory cases, surgical drainage may be necessary.

148

Below is a lateral thoracic radiograph of the caudodorsal lung field of a 4-month old foal with clinical evidence of weight loss, fever, and tachypnea. What is the best diagnosis based on the clinical signs and radiograph?

a. Congestive heart failure

b. Pulmonary abscesses

c. Pulmonary carcinoma

d. Phinopneumonitis pneumonia

e. Pulmonary aneurism

Q image thumb

b. Pulmonary abscesses

The two horizontal lines represent fluid or pus capped by gas within cavitary lesions. In foals, this occurs most frequently with Rhodococcus equi pneumonia.

A image thumb
149

Which of the following is not believed to be a cause of physitis in young horses?

a. Malnutrition

b. Conformational defects

c. Abnormal hoof growth

d. Growth plate compression

e. Osteochondrosis

 

e. Osteochondrosis

The correct answer is osteochondrosis. Physitis in young horses involves swelling around growth plates in long bones. Physitis is sometimes thought to be a component of osteochondrosis, but the other answer choices have been suggested to be causes of physitis.

150

On a routine screening physical exam, you have noted low serum potassium in a 4-year old Thoroughbred racehorse. Which one of the following is the most likely cause of hypokalemia in a horse?

a. Chronic use of furosemide, a diuretic

b. Dietary insufficiency of potassium

c. Hyperlipidemia

d. Salt poisoning

e. Psychogenic polydipsia

a. Chronic use of furosemide, a diuretic

Loop diuretics cause excessive amounts of potassium to be lost via the urine.

151

An adult horse presents to you for recurrent seasonal pruritus during the summer months that seems to be worsening. On physical examination, you find multiple excoriations along the poll, mane, and tail. What is the most likely cause of this horse's pruritus?

a. Haematobia

b. Onchocerca

c. Culicoides

d. Habronema

e. Hypoderma

c. Culicoides

The correct answer is Culicoides. Culicoides hypersensitivity, also referred to as sweet itch, occurs due to allergy to the saliva of the gnat. It recurs seasonally in the warmer months and tends to worsen with age. Typically, horses are pruritic and develop lesions on the poll, mane, and tail from self trauma, although ventral midline dermatitis can occur as well. More chronically, scarring can occur. Treatment is to decrease exposure to the gnat and to treat with steroids. Habronemiasis is a condition where the larvae of the stomach worm migrate and emerge creating granulomatous lesions, usually around the eye, male genitalia, or lower extremities. Inside the granulomas, you can find dead larvae. Haematobia irritans is a bigger problem in cattle than horses (they reproduce in cow feces) but can affect horses, especially ones that are near cattle. It typically causes ventral midline dermatitis with wheals with a central crust that progress to alopecia and ulceration with fairly focal lesions, rather than more diffuse lesions caused by Culicoides. Onchocerca can cause dermatitis in the horse due to hypersensitivity to dying microfilariae. Lesions include alopecia and scaling of the ventral midline, face, and pectoral region. Often, lesions are diamond shaped and there may be a "bull's eye" lesion on top of the head. Onchocerca is nonseasonal, in contrast to Culicoides hypersensitivity, and variably pruritic. Ocular lesions can also occur with Onchocerca including uveitis, conjunctivitis, and keratitis. Lastly, Hypoderma is also a bigger problem in cattle but can occur in horses and typically creates nodules on the dorsum that have a pore on top.

152

The wolf tooth in the horse is ______.

a. Incisor 1

b. Premolar 1

c. Molar 1

d. Premolar 2

e. Canine

b. Premolar 1

The correct answer is Premolar 1. For some reason it is commonly confused as being a canine tooth.

153

A 5-year old mare is hospitalized for intestinal impaction. The horse passed the impaction today and now has diarrhea. How would you treat this horse?

a. Intravenous fluids

b. Antibiotics

c. Oral fiber

d. Docusate sodium (DSS)

e. Mineral oil

a. Intravenous fluids

The correct answer is intravenous fluids. DSS, mineral oil, and fiber supplementation will likely not benefit a horse with diarrhea. There is no described infection, so antibiotics are not indicated at this time. IV fluids will help replace fluid losses associated with diarrhea and will help maintain a normal hydration state.

154

Which of the following is false concerning abdominal paracentesis in a horse?

a. Usually performed to the left of midline

b. Normal color is usually yellow

c. Nucleated cells are usually less than 5,000/uL and total protein is less than 2.5gm/dL if normal

d. Bitch catheter is commonly useds

a. Usually performed to the left of midline

The correct answer is usually left of midline. It is not recommended to perform an abdominal paracentesis to the left of midline as you are more likely to hit an organ such as the spleen. It is usually performed just to the right of midline. All other choices are true about abdominal paracentesis in a horse.

 

155

In which of these situations is an acetylcysteine enema most likely to be used?

a. Small colon impaction

b. Enterolith

c. Sand impaction

d. Meconium impaction

d. Meconium impaction

The correct answer is meconium impaction. This occurs in neonatal foals, typically within the first 24 hours of birth, and results in tenesmus and variable degrees of colic. Acetylcysteine will cleave disulfide bonds in mucoproteins of meconium impactions and help break them down.

156

Warfarin intoxication in horses interferes with synthesis of which clotting factors?

a. II, VII, IX, X

b. VII, VIII, IX, X

c. VIII, IX, XI, XII

d. II, V, VII, X

a. II, VII, IX, X

The correct answer is II, VII, IX, X. These are the vitamin K-dependent coagulation factors. Warfarin is an inhibitor of vitamin K and interferes with hepatic synthesis of these factors.

157

Which of these would you expect to see in a horse that has had significant blood loss?

a. Hypoproteinemia

b. Macrocytic, hypochromic anemia

c. Nonresponsive bone marrow

d. Microcytic, hypochromic anemia

e. Polycythemia

a. Hypoproteinemia

The correct answer is hypoproteinemia. The expected findings in a horse with blood loss are anemia (normocytic, normochromic), hypoproteinemia, and responsive bone marrow.

 

158

A 19 year old Saddlebred gelding presents with a history of staggering and respiratory distress. On physical exam, it is noted the horse is sweating, has a heart rate of 52, and a respiratory rate of 44. Hemoglobinuria is identified on urinalysis. This horse lives in close proximity to cattle, and it is suspected that he may have been eating cow feed. What feedstuff additive is known to be very toxic to horses and result in cardiomyopathy if consumed at high enough doses?

a. Salinomycin

b. Monensin

c. Lasalocid

d. Selenium

e. Copper

b. Monensin

The correct answer is monensin. Monensin is a commonly used coccidiostat in feedstuff of cattle. This ionophore is highly toxic to horses (the toxic dose for hoses is 10 to 15 times less than for cattle) and will result in cardiomyopathy and myocardial necrosis. Unfortunately, there is no quick and easy antidote, and treatment usually consists of trying to empty the intestinal tract by using mineral oil, activated charcoal, and fluid therapy. Lasalocid and salinomycin are also ionophores that you might worry about, but monensin is much more toxic to horses. Selenium and copper are usually added to feedstuffs as a result of being deficient in the soil. Lack of supplementation with these minerals may result in cardiovascular disease, such as white muscle disease with selenium deficiency, and excessive bleeding in aged parturient mares with copper deficiency. One way of determining prognosis is to evaluate the horse's fractional shortening via echocardiography. Normally the fractional shortening is 30-40%; if you calculate fractional shortening to less than 20%, the prognosis is poor.

159

Which of these is not an appropriate physiologic response to acute blood loss in a horse?

a. Decreased cardiac output

b. Splenic contraction

c. Vasoconstriction

d. Increased water resorption by the kidney

a. Decreased cardiac output

The correct answer is decreased cardiac output. In an event of acute blood loss in a horse, catecholamines induce vasoconstriction and increased cardiac output. Antidiuretic hormone release causes water and sodium resorption in the kidney. Splenic contraction occurs to inject stored erythrocytes into circulation.

160

An 8 year-old, 1223 lb, Quarter Horse gelding is presented to you with a 4-day history of lethargy, inappetance, intermittent fever (ranging from 101.2-104.5F, 38.4-40.3 C), and peripheral limb edema. Upon physical examination, you note the following abnormalities: lethargy, tachycardia (60 beats/min), limb edema and fever (103.2F, 39.6 C). The serum biochemistry analysis is within relatively normal reference intervals but the CBC yields the following abnormalities:

WBC: 1.50 x 10,000/mcL (reference 5.0-11 x 10,000/mcL)
HCT: 32% (reference 34-45%)
Platelet: 71 x 10,000/mcL (reference 130-300 x 10,000/mcL)
Neutrophil: 1.20 x 10,000/mcL (reference 2.2-6.5 x 10,000/mcL)
Lymphocyte: 0.23 x 10,000/mcL (reference 1.3-4.5 x 10,000/mcL)
Fibrinogen: 500 mg/dL (reference 100-400 mg/dL)

In addition, the following was observed on microscopic examination of the blood smear (see image). The most likely diagnosis, based on the history, clinical findings, and CBC results in this case, is which of the following?

a. Streptococcus equi infection

b. Heinz body anemia

c. Endotoxemia/septicemia (toxic changes within cell)

d. Anaplasma phagocytophilum infection

e. Equine infectious anemia (EIA) infection

Q image thumb

d. Anaplasma phagocytophilum infection

Based on the clinical signs (fever, lethargy, tachycardia and limb edema), CBC results (leukopenia, neutropenia, thrombocytopenia) and microscopic observation of a morula within the neutrophil, the correct answer and diagnosis is Anaplasma phagocytophilum infection. Diagnosis can be supported via PCR assays.

Anaplasmosis (formerly Ehrlichi equi) infects primarily neutrophils and form inclusion bodies which consists of one or more coccobacillary organisms within these cells, known as morula. The complete pathogenesis of this disease is not fully elucidated but the organism is spread via tick bites. Other clinical signs that may be associated with this disease include petechiation, icterus and ataxia. The drug of choice for this disease is...(think about it for a second)...you got it...oxytetracycline.

161

You are examining a 13-year old Standardbred brood mare 5 hours after parturition. You note that the placenta is still present in the reproductive tract of the mare (see image). What is the most appropriate therapy?

a. Administer oxytocin (IM or IV) and lavage the uterus to facilitate removal

b. Place physical traction on the placenta and remove it manually

c. Administer penicillin (IM) until the placenta is expelled on its own

d. Do nothing; the placenta is not considered retained until 12 hours post-parturition and it will likely be expelled by this time

Q image thumb

a. Administer oxytocin (IM or IV) and lavage the uterus to facilitate removal

Most texts state that the placenta in a mare is retained after greater than 3 hours post-parturition; therefore, this would be considered a retained placenta. Oxytocin, along with uterine lavage, will cause the uterus to contract and facilitate expulsion of the placenta. Strong physical traction on the retained placenta is generally considered contraindicated, as you may tear the placenta and leave remnants of it within the uterus, resulting in possible complications. Broad-spectrum antimicrobials are often administered to decrease the incidence of metritis but alone would not be appropriate.

162

You are an equine clinician working out in the field. You encounter a colic case and palpate a small intestinal obstruction. You decide to refer the case to a nearby hospital for surgical intervention. What is the most important thing to do before shipping the horse?

a. Abdominal ultrasound

b. Sedate

c. Pass a nasogastric tube

d. Belly tap

e. CBC and Chemistry

c. Pass a nasogastric tube

The correct answer is to pass a nasogastric tube. It is crucial to do this, as horses are unable to vomit due to high lower esophageal sphincter tone. By passing the tube, you will allow reflux and relieve life-threatening gastric pressure. Sedation is important to help provide relief; however, gastric rupture will kill the horse first.

163

Clostridium difficile is a spore-forming bacteria commonly associated with enterocolitis and diarrhea in adult horses and foals. Which of the following statements is NOT correct in regard to C. difficile in horses?

a. The 2 main virulence toxins are toxin A and toxin B

b. C. difficile is a Gram-positive, rod shaped, obligate anaerobe

c. Administration of non-steroidal anti-inflammatory medications.  For examples flunixin meglumine, is a risk factor for the development of C. difficile enterocolitis

d. Transmission of C. difficile occurs via the oral-fecal route

e. C. difficile can survive for prolonged periods of time in the spore form

c. Administration of non-steroidal anti-inflammatory medications.  For examples flunixin meglumine, is a risk factor for the development of C. difficile enterocolitis

The correct answer is NSAID treatment is a risk factor for the development of C. difficile enterocolitis. Remember all the other answers are correct, so hopefully you can take away some of these important facts from this question. Risk factors for the development of disease include antibiotic treatment and hospitalization, but does not include administration of NSAIDs.

164

A horse presents to you with a corneal ulcer. You are concerned because it appears to be infected. You perform cytology and find gram negative rods. What is the most appropriate treatment for this infection?

a. Topical natamycin

b. Topical tobramycin

c. Systemic penicillin

d. Topical cefazolin

b. Topical tobramycin

The correct answer is topical tobramycin. Tobramycin is an aminoglycoside and would be effective against most gram negative organisms, including Pseudomonas, which are the most common cause of bacterial keratitis. Cefazolin would be useful topically for a gram + infection. Systemic antibiotics would not penetrate to the site at levels that would be effective. Natamycin is an antifungal drug and would not be useful in this case of bacterial keratitis.

165

A 4 year old mare has bilateral swelling and drainage of the mandibular lymph nodes. Rectal temperature is 101.8F (38.8 C). Which of the following is the most appropriate plan for this horse?

a. Administer penicillin

b. Administer corticosteroids

c. Culture the discharge for bacteria

d. Inform the state veterinarian

c. Culture the discharge for bacteria

The correct answer is to culture the discharge for bacteria. The most likely diagnosis for this horse is equine strangles. Strangles most commonly affects younger horses (<5 years of age), but can cause disease in any age horse. The etiologic agent of this disease is Streptococcus equi subsp. equi. The diagnostic test of choice to confirm this is bacterial culture. While awaiting culture results, the horse should be separated from any other horses, as strangles is highly contagious to other horses. Antibiotic therapy is controversial and thought to lengthen the course of disease rather than shorten it when given at this stage; also, it may possibly interfere with the natural immunity acquired from natural infection. Strangles is a reportable disease.

166

A 9 year old Thoroughbred mare presents for intermittent left-sided epistaxis over several months. There is no history of trauma. The horse has mildly increased respiratory effort on your physical exam. Which of these is the most likely cause of recurrent, intermittent, unilateral epistaxis in this animal?

a. Exercise induced pulmonary hemorrhage

b. Ethmoid hematoma

c. Purpura hemorrhagica

d. Warfarin toxicity

b. Ethmoid hematoma

The correct answer is ethmoid hematoma. An ethmoid hematoma is a progressive and locally destructive mass that resembles a tumor but is not truly neoplastic. The most common clinical sign is mild, persistent, spontaneous, intermittent epistaxis that can be unilateral or bilateral. Warfarin is not as likely in this horse due to the recurrent nature of the condition and the fact that it is unilateral. Exercise-induced pulmonary hemorrhage actually causes epistaxis only about 10% of the time. Also, since the bleeding is pulmonary in origin, the epistaxis would likely be bilateral. Epistaxis with this condition also occurs immediately after exercise, which was not reported in this horse. Purpura hemorrhagica is a vasculitis that results from a type III immune complex hypersensitivity after a streptococcus equi infection. This leads to vasculitis, and the main clinical signs are petechia and ecchymoses of mucous membranes.

167

A 1-year old pony presents to you for lameness evaluation. You observe the pony walking and note that the left pelvic limb locks in rigid extension and there is a delay in flexion of the stifle resulting in the horse dragging the toe. You also note excessive wear on the toe, presumably from repeated dragging. Which of the following is the most specific diagnosis?

a. Thoroughpin

b. Gonitis

c. Jack spavin

d. Upward patellar fixation

e. Stringhalt

d. Upward patellar fixation

Upward patellar fixation causes the gait described above. Any horse that has the hind limb in rigid extension and is unable to flex it should be suspected of having this problem. One condition that can mimic this gait is luxation of the coxofemoral joint which can lead to an inability to flex the hind limb but this can be distinguished clinically because the limb will not be extended.

Normally, when horses are standing and resting their hindlimbs, the patella elevates to the top of the femoral trochlea, and the medial patellar ligament hooks over the medial ridge of the trochlea, locking the joint and allowing the horse to rest the limbs. To flex the stifle again, the quadriceps femoris muscle contracts, lifting the medial patellar ligament free of the medial trochlear ridge allowing the patella to return to its working position. When something prevents the horse's ability to release the stifle, the condition is known as upward patellar fixation (also called "upward fixation of the patella" or "locked stifle").

Most cases of upward patellar fixation can be managed conservatively (exercise (physical therapy), improved body condition). In severe and unresponsive cases, surgery to cut the medial patellar ligament is an option.

Stringhalt is involuntary flexion of the hindlimb and is usually bilateral. The problem in this case is rigid extension. Stringhalt is treated with lateral digital extensor tenectomy.

Gonitis is a term indicating stifle arthritis. It is nonspecific to the underlying cause and could be due to osteochondrosis, ligament injury, or some other problem. Upward patellar fixation and its consequences could be referred to as gonitis but this is a less specific diagnosis in this case.

Jack spavin is a lay term for cunean bursitis or irritation of the cunean tendon as a result of bone growth on the medial hock.

Thoroughpin is the term for effusion of the tarsal sheath (sheath of the deep digital flexor).

168

You diagnose a horse with vesicular stomatitis. What should you do next?

a. Notify the state and federal authorities

b. Vaccinate the horse

c. Start the horse on anti-viral medications

d. Euthanize the horse immediately

a. Notify the state and federal authorities

The correct answer is notify the state and federal authorities. Vesicular stomatitis is a disease that must be reported to state and federal authorities. There is no specific treatment for the disease. Secondary infections should be treated symptomatically.

169

A 12-year old mare presents to you as a "windsucker". Why is pneumovagina in mares of medical concern?

a. It causes abortion or early embryonic death

b. It heavily predisposes to vaginitis and endometritis

c. It predisposes to colic

d. It prevents normal estrus cycling

b. It heavily predisposes to vaginitis and endometritis

The correct answer is it heavily predisposes to vaginitis and endometritis. Aspiration of air leads to contamination, and pneumovagina is the most common cause of genital infections in the horse. Pneumovagina is a common cause of infertility due to the high incidence of vaginitis, cervicitis, and endometritis in affected mares. The Caslick procedure can be used in cases of pneumovagina in mares.

170

How soon after administration of tetanus antitoxin in a horse is there protection against tetanus?

a. 7 dats

b. 14 days

c. 28 days

d. 6 months

e. Immediately

e. Immediately

The correct answer is immediately. Administration of 1500 IU results in immediate protection that will last for approximately 2-3 weeks. Administration of tetanus toxoid will provide protective titers 14 days after the second dose, when given 3-6 weeks apart.

171

A horse presents for further evaluation as a result of a progressive onset of strange behavior, according to the owner. On physical exam, the horse is noted to have a jerky and awkward motion when trying to initiate movement. The horse is noted have an exaggerated arc and flight of the limbs when stepping over a curb. Where is the lesion most likely to be?

a. Pons

b. Midbrain

c. Medulla

d. Cerebellum

e. Cerebrum

d. Cerebellum

The correct answer is cerebellum. The cerebellum is responsible for the coordination and regulation of range, rate, and strength of movement along with balance and posture. Clinical signs associated with cerebellar disease include intention tremors, hypermetria, hypometria, and ataxia. Mentation will be normal if the disease is strictly confined to the cerebellum.

172

In adult horses, tetanus usually occurs from ______________?

a. Performed tetanus toxin entering a puncture wound

b. Ingestion of performed tetanus toxin

c. Ingestion of clostridial spores

d. Inhalation of clostridial spores

e. Clostridial spores entering a deep puncture wound

e. Clostridial spores entering a deep puncture wound

The correct answer is clostridial spores entering a deep puncture wound. The spore is found in the soil and in feces and requires entry through a deep wound to find an anaerobic environment. They then form their toxin and release it, where it is picked up by nerves and travels to the spinal cord.

173

Failure of closure of the foramen ovale within the first 48 hours of life in a healthy foal will result in _______.

a. Shunting of blood from the left atrium to the right atrium

b. Shunting of blood from the right atrium to the left atrium

c. Shunting of blood from the left ventricle to the right ventricle

d. Shunting of blood from the right atrium to the ductus arteriosus

b. Shunting of blood from the right atrium to the left atrium

The correct answer is shunting of blood from the right atrium to the left atrium. The foramen ovale is a small slit that allows shunting between the right atrium and left atrium in the fetus. Once the foal is born, the lungs expand (right atrial pressure decreases) and the left atrium becomes a higher pressure system than the right. This higher pressure in the left atrium at birth forces the closure of the foramen ovale flap against the septum secundum and, in health, typically fusion of these tissues occurs to permanently close the foramen ovale. However, if the foramen ovale flap does not fuse, this leads to patency. In this case, the flap acts somewhat akin to a one-way valve so when the LA pressure is higher the flap is closed, but when the RA pressure is higher, blood can flow right to left. This occurrence (RA pressure > LA pressure) may happen when the patient coughs, takes a deep breath or sneezes which increases the return of venous blood to the RA.

174

What percentage of the kidney must be damaged in order to see laboratory changes consistent with renal insufficiency in horses?

a. 66%
b. 80%
c. 33%

d. 25%

e. 50%

a. 66%

The correct answer is 66%. At this point you begin to see isosthenuria due to a decreased ability to concentrate urine. Azotemia will be apparent at approximately 75% damage to the kidneys.

175

A 2-year old Thoroughbred race horse presents for lameness evaluation. The trainer reports that the lameness has been slowly progressive over the past 3 weeks. You observe the horse walk and see a short, choppy gait in the front legs. There is swelling over the front of both fetlock joints and palpation and flexion of the fetlocks elicits pain. Radiographs show no evidence of new bone formation in the fetlock. You diagnose the horse with osselets (periostitis of the distal dorsal cannon bone). What is the best treatment recommendation?

a. Palmar digital neurectomy

b. Deep digital flexor tenotomy

c. Rest, phenylbutazone, and intra-articular injections of sodium hyaluronate

d. Arthrodesis of the fetlock

c. Rest, phenylbutazone, and intra-articular injections of sodium hyaluronate

Cases of osselets that are caught before the development of osteoarthritis often respond completely to medical management consisting of rest, anti-inflammatories (such as phenylbutazone) and intra-articular injections of sodium hyaluronate or polysulfated glycosaminoglycans (Adequan).

Fetlock arthrodesis is reserved for more advanced fetlock injuries. Deep digital flexor tenotomy is used to treat certain cases of chronic laminitis. Palmar digital neurectomy is used to treat navicular disease and results in desensitization of the heel.

176

You diagnose this 15-year old mare in the picture with a mild, acute laminitis. Which of the following can be used as treatment for this horse?

a. Prednisone

b. Application of horse shoes

c. Phenoxybenzamine

d. Trimethoprim sulfa

Q image thumb

c. Phenoxybenzamine

The correct answer is phenoxybenzamine. Phenoxybenzamine is an alpha-adrenergic antagonist promoting vasodilation and restoration of blood flow to the digits. Prednisone is contraindicated in laminitis because corticosteroids are believed to induce the condition. Antibiotics are not indicated unless a secondary bacterial infection develops. Application of a horse shoe would not help and would be very painful in an already sensitive and painful condition. Other medications used to restore blood flow to the digits include acepromazine, isoxsuprine hydrochloride, dimethylsulfoxide (DMSO), heparin, and nitroglycerine.

177

A pony owner has had several ponies develop acute and severe cases of laminitis this season. You evaluate the environment and attempt to determine the cause. Which of the following changes could you recommend to decrease the incidence of this problem?

a. Prevent free access to lush grass pastures

b. Institute better arthropod control measures

c. Supplement ponies with selenium

d. Increase gain in diet

a. Prevent free access to lush grass pastures

Acute laminitis is commonly associated with excess carbohydrate intake. Grazing of lush pastures is an especially common precipitating cause in ponies. Laminitis is not associated with selenium deficiency or arthropod problems.

178

A one-month old foal develops fever, icterus, and diarrhea acutely. Bloodwork shows hyperfibrinogenemia, hypoglycemia, and elevated liver enzymes. Which of these conditions is most likely?

a. Theiler's disease

b. Clostridium novyi type B

c. Tyzzer's disease

d. Herpesviral hepatitis

c. Tyzzer's disease

The correct answer is Tyzzer's disease. This is the most likely cause because of the age of the foal and the acute nature of the disease. Tyzzer's disease is caused by Clostridium piliformis, which causes an acute necrotizing hepatitis. It affects only foals from about 1-6 weeks of age. Theiler's disease is a condition of adult horses. Clostridium novyi is rare in horses and seen much more in sheep and cattle. Herpesvirus can cause hepatitis but is usually seen at or very soon after birth.

179

A 1.5-year old Quarter Horse gelding is presented to you for symmetric ataxia, weakness, and spasticity of all limbs, but worse in the hind limbs. When walking, the horse frequently drags his toes and the hind limbs frequently interfere with one another. Based on the signalment, history and physical examination findings, which of the following is the most likely cause of these clinical signs?

a. Botulism

b. Cauda Equina Syndrome

c. Equine Degenerative Myeloencephalopathy (EDM)

d. Equine Motor Neuron Disease (EMND)

e. Equine Protozoal Myeloencephalitis (EPM)

c. Equine Degenerative Myeloencephalopathy (EDM)

The horse in this question has clinical signs most consistent with EDM; cervical vertebral malformation (wobblers) is also a possibility, but was not provided as an answer. The cause of EDM is unknown, but this disease typically affects young horses (< 2-3 years of age; but older horses can develop disease). Clinical signs are a result of diffuse neuronal fiber degeneration of various portions of the central nervous system. This disease has been associated with low serum vitamin E concentrations, suggesting that oxidative damage may play a role in the development of disease.

EMND is typically associated with muscle tremors, shifting of weight while standing, muscle atrophy and recumbency. Botulism is associated with generalized muscle weakness. Cauda equina syndrome causes analgesia of the perineum. EPM can cause a range of clinical signs, but is typically with asymmetric neurologic deficits.

180

A valuable horse suddenly developed severe intractable diarrhea and fever 5 days ago. The owner has been giving it oral electrolytes free choice in the water, and offering it hay, grain, and green grass. It is brought to your clinic on a normal warm summer day looking thin, dehydrated, weak, and anorectic (see photo). You do a physical exam and find T=102F (38.9 C), HR=56, RR=24, with somewhat purplish oral mucous membranes. The urine is normal but has a small volume and looks concentrated. You run a PCV (45%), WBC count (normal at 7000/microliter) and total protein (TP). The TP is low at 3.5 gm/dL and the albumin is 1.4 gm/dL indicating a protein-losing enteropathy. Of the following, what is the best treatment for the low plasma proteins in this horse?

a. IV plasma

b. Oral albumin

c. Whole blood IV

d. Feed very high protein diet with added amino acids

e. IV amino acids

Q image thumb

a. IV plasma

The damaged bowel is leaking albumin out into the gut lumen, and the horse may develop other problems such as edema and poor healing ability if the protein levels are not boosted. The best way to do that in an animal with GI disease is by the IV route. Whole blood may raise the PCV to a level where sludging and circulatory problems develop in an already dehydrated horse. Another option to consider if plasma is not readily available is the use of synthetic colloidal solutions such as hetastarch.

181

Which of these toxins can cause colic?

a. Aflatoxin

b. Black locust

c. Cantharidin

d. Fescue

e. Cyanide

c. Cantharidin

The correct answer is cantharidin. The blister beetle is the organism known to make this toxin. The toxin commonly gets incorporated into alfalfa, and the beetles get killed when the hay is processed. Other toxic causes of colic include oleander, rhododendron, and nightshades.

182

Black walnut toxicity causes what condition in horses?

a. Pulmonary edema

b. Hypersalivation

c. Colic

d. Laminitis

d. Laminitis

The correct answer is laminitis. Black walnuts contain Juglone (naphthoquinone) which results in laminitis. Do not use black walnuts for horse bedding.

Black walnut shavings, photo courtesy of Krishona Martinson, University of Minnesota

A image thumb
183

You suspect liver failure in a sick horse. You perform a liver biopsy which shows histopathological changes of megalocytosis, periportal fibrosis, and biliary hyperplasia. What most likely caused the liver failure?

a. Theiler's disease

b. Chronic active hepatitis

c. Pyrrolizidine alkaloid toxicity

d. Tyzzer's disease

e. Copper toxicity

c. Pyrrolizidine alkaloid toxicity

The correct answer is pyrrolizidine alkaloid toxicity. The three histopathologic changes described are the classic changes seen with pyrrolizidine alkaloid toxicity. With Tyzzer's disease, you would see randomly distributed foci of necrosis and long slender rods in hepatocytes at the periphery of the necrotic foci. With chronic active hepatitis, histopathologic changes would be hepatocyte damage, variable fibrosis, inflammatory infiltration, and evidence of biliary hyperplasia with bile stasis.

184

Which of these is a sign of anestrus in a mare when presented with a stallion?

a. Raising tail

b. Frequent urination

c. Squatting

d. Ears back

d. Ears back

The correct answer is ears back. During anestrus, a mare will typically reject a stallion's romantic interest. Other signs of rejection by a mare include striking and avoidance of a stallion. The other choices are all signs of estrus.

185

A 4 year old horse presents to you with a mucopurulent nasal discharge, lethargy, and depression. On physical exam, the horse has a temperature of 103.7F (39.8 C) and has markedly enlarged mandibular and retropharyngeal lymph nodes. You suspect that the horse has strangles. What would you expect to see if you aspirated one of the enlarged lymph nodes?

a. Reactive lymphocytes and macrophages with no bacteria

b. Purulent inflammation and gram positive cocci with large capsules

c. Fungal hyphae and granulomatous inflammation

d. Purulent inflammation and gram negative rods with large capsules

e. Granulomatous inflammation and gram negative cocci

b. Purulent inflammation and gram positive cocci with large capsules

The correct answer is purulent inflammation and gram positive cocci with large capsules. The causative agent of strangles is streptococcus equi ssp. equi which is a gram positive cocci with a large capsule. It causes suppurative abscessation and enlargement of the mandibular and retropharyngeal lymph nodes.

186

A Paint horse is found to be approximately 7% dehydrated after a several day trail ride. Assuming there are no other ongoing losses and the horse weighs 500kg how many liters of fluid will you need to give this horse over a 24 hour period to correct the deficit and account for maintenance requirements?

a. 35L

b. 65L

c. 75L

d. 40L

e. 125L

b. 65L

To determine this answer you must figure out the deficit and calculate the horse's maintenance needs. The deficit is 35L (deficit x BW). Maintenance needs for a horse is approximately 60ml/kg/day. In this case, 30L. Adding the deficit and maintenance fluids together yields a total of 65 liters.

187

You are asked to perform a necropsy on a 17-year old Standardbred mare on a large horse ranch. Although not related to the cause of death, you notice the parasite shown in the image within the stomach. You tell the owner that this parasite is also responsible for the eggs that he sees seasonally on the hair of the front legs of his horses. The owner asks what should be done about this. You discuss the importance of promptly cleaning up feces and transporting feces away. In addition, which of the following is the most appropriate recommendation for ongoing control of this parasite?

a. Administer ivermectin twice annually, once in the early summer and again in the fall

b. There is no need to treat these parasites because they are not associated with disease in horses

c. Administer fenbendazole twice annually, once in the early summer and again in late summer

d. Administer fenbendazole twice annually, once in the early spring and again in the fall

e. Administer ivermectin twice annually, once in the early spring and again in the winter

a. Administer ivermectin twice annually, once in the early summer and again in the fall

This case describes the appearance of the horse bot fly, Gasterophilus spp. Gasterophilus is frequently asymptomatic but treatment is recommended because bots can cause gastritis and frequently are a source of annoyance and stress to horses. In addition, the larval instars can cause stomatitis, and colic.

The key to answering this question regarding optimal treatment and management is an understanding of the Gasterophilus life cycle. Gasterophilus undergoes complete metamorphosis, including three larval instars and only one generation is produced per year. The general cycle typically begins with the female ovipositing 150-1,000 eggs on a horse during the early summer months directly on single hairs of the horse's front legs (especially around the cannon bone area) as well as the abdomen, flanks, and shoulders. The eggs are approximately 1-2mm long and are pale to grayish yellow attached near the tip of the hair.

The eggs develop into first instar larvae within five days and they are stimulated to emerge by the horse licking or biting at the fully developed eggs. The larvae then crawl to the mouth or are ingested and subsequently bury themselves in the tongue or gingiva and remain for approximately 28 days. The larvae molt to the second stage and move into the stomach. The second and later third stage larvae typically attach to the lining of the stomach in the non-glandular portion near the junction of the esophageal and cardiac regions where they remain immobile for the following 9 to 12 months.

The third instar larvae are relatively large, between 1-2cm long with a rounded body, narrow, hooked mouthparts, and spines. The hooked mouthparts enable the larvae to securely attach to the lining of the stomach and intestinal tract. After the third instar larvae have matured, they detach from the gastrointestinal tract and pass from the horse's body in the feces. The larvae burrow into the soil or dried manure where they pupate and remain for the next one to two months. This stage of the life cycle occurs between late winter and early spring.

Based on this life cycle, the recommended management protocol is typically to treat with an avermectin to control adults and all larval stages by administering in the early summer, shortly after any eggs are seen and again in the fall at the end of the botfly season. Such a control program will substantially reduce fly numbers.

188

A 3-year old Thoroughbred race horse presents for lameness evaluation. The trainer reports that the lameness has been slowly progressive over the past 6 weeks. You observe the horse walk and see a short, choppy gait in the front legs. There is swelling over the front of both fetlock joints and palpation and flexion of the fetlocks elicits pain. Which of the following is the most likely diagnosis?

a. Osselets

b. Sidebones

c. Low ringbone

d. Navicular syndrome

e. High ringbone

a. Osselets

Osselets are inflammation of the periosteum on the dorsal distal epiphyseal surface of the third metacarpal bone and fetlock joint. As in this case, they are often (but not always) bilateral. Osselets typically begin from chronic stress injury to the front fetlock(s) from repeated concussive forces during racing and hard training. Horses with long or upright pasterns may be predisposed. The major clinical signs are increasing lameness and a short choppy gait. Thickening and soreness of the fetlock are also frequently seen. Early diagnosis and intervention is important because once the condition progresses to osteoarthritis, the prognosis is much worse. If recognized early and treated with rest, anti-inflammatory medications, and intra-articular sodium hyaluronate injections, many horses can recover completely.

None of the other choices listed are associated with the fetlock. Low ringbone is osteoarthritis of the distal interphalangeal (coffin) joint. High ringbone is osteoarthritis of the proximal interphalangeal (pastern) joint. Sidebones are ossification of the collateral (alar) cartilages of P3. Navicular syndrome affects the heel.

189

A 3-year old gelding is presented for lameness. Physical exam reveals moist, exudative dermatitis of the central and lateral sulci of the frog of his feet and a thick black discharge with a malodorous smell. Which of the following is an appropriate way to treat the disease?

a. Trim away the necrotic tissue and administer systemic antibiotics

b. Trim away necrotic hoof material, apply antiseptic products, apply a bandage, and educate the client on proper hygiene

c. Administer systemic antibiotics, corticosteroids, and educate the client on proper hygiene

d. Administer systemic antibiotics and advise the owner about proper hygiene for the horse

e. Advise the owner to clean up the horse's environment and educate about proper hygiene

b. Trim away necrotic hoof material, apply antiseptic products, apply a bandage, and educate the client on proper hygiene

The correct answer is to trim away necrotic hoof material, apply antiseptic products, apply a bandage, and educate the client on proper hygiene. The horse has thrush, a condition often caused by Fusobacterium necrophorum in horses. The condition is usually caused by unsanitary conditions, poor foot care, and lack of exercise. Systemic antibiotics and corticosteroids are usually unnecessary.

190

One of your clients recently purchased a horse that she plans to add to her stable. She is concerned about potential exposure of the horse to Streptococcus equi subsp. equi. Which of the following is the most sensitive test for detecting carriers of the disease?

a. Guttural pouch culture Columbia CNA (Colistin, nalidixic acid) agar with 5% sheep or horse blood

b. Nasopharyngeal culture on Columbia CNA (Colistin, nalidixic acid) agar with 5% sheep or horse blood

c. Serology for antibodies to S. equi M protein (SeM)

d. PCR of a guttural pouch wash for the S. equi M protein (SeM) gene

d. PCR of a guttural pouch wash for the S. equi M protein (SeM) gene

Testing for Streptococcus equi subsp. equi can be complex. The 3 major tests are PCR, serology, and culture. PCR and serology both detect SeM which is an important virulence factor for the bacteria. Culture is best performed on Columbia CNA agar with 5% sheep or horse blood.

While there are pros and cons to each test, the key to answering this question correctly is focusing on the issues of sensitivity and detecting carriers.

PCR is approximately 3 times more sensitive than culture. In general, sampling the guttural pouch is a better way to detect carriers than the nasopharynx because it is where most carriers harbor the organism.

Serology is the best test for assessing exposure but is not a good tool for detecting carriers. This is because antibodies may be elevated after an infection has been cleared or even after vaccination. It may also be falsely negative if an exposure was recent.

To summarize the best uses of culture, PCR and serology:

Culture is the gold standard for diagnosing a horse with an infection.

PCR is best for detecting asymptomatic carriers, establishing infection status prior to or following transport, and to determine the success of elimination of S. equi from the guttural pouch. PCR cannot distinguish live DNA from dead DNA and may have false positives after a cleared infection. Using PCR in combination with culture may be helpful in such an instance.

Serology is best for determining exposure and the need for vaccination as well as for supporting diagnoses of S equi associated purpura hemorrhagica or of bastard strangles.

191

Two pet horses on a ranch are presented for extreme pruritus at their ventrum. The owners report the pruritus has gotten worse during the summer, and they notice increased numbers of small flying insects around at dusk and dawn. Examination of the horses reveals excoriations, alopecia, and thickening of the skin at the ventrum. One of the flies collected in the field by the owner is a small fly with mottled wings. What is your most likely diagnosis?

a. Chrysops fly bites

b. Tabanus fly bites

c. Mosquito hypersensitivity

d. Culicoides hypersensitivity

e. Onchocerciasis

d. Culicoides hypersensitivity

The correct answer is Culicoides hypersensitivity. Culicoides hypersensitivity is extremely pruritic and is also known as "sweet itch". Horses can be affected on their ventrum or dorsum, depending on the species of the fly. The horse develops a type 1 hypersensitivity to the flies' salivary antigens and develops excoriations, alopecia, and thickened skin as a result of scratching. The flies are more prevalent during the warmer seasons and are most active during dusk and dawn. Treatment includes controlling the fly population. Stabling the horses at dusk is often helpful because the flies rarely enter barns. Insecticides, stable blankets, and fans for circulating air in the stables may also be useful. The extreme pruritus and seasonality of the clinical signs is often enough to differentiate the Culicoides hypersensitivity from other skin diseases. Onchocerciasis is vectored by Culicoides, but is not seasonal and is not nearly as pruritic. Mosquitoes can be an annoyance and, more importantly, are vectors for more serious diseases such as the equine encephalitides. Tabanus flies and Chrysops flies cause pain to horses by lacerating them with their mouth parts to feed on their oozing blood. They do not cause pruritus and can be differentiated by their large, robust size.

192

Which of the following does not typically cause ventral midline dermatitis in horses?

a. Haematobia irritans

b. Chorioptes equi

c. Culicoides hypersensitivity

d. Onchocerciasis

b. Chorioptes equi

The correct answer is Chorioptes equi. Chorioptes is a mange mite that is usually found around the foot and fetlock. It causes a pruritic dermatitis that can cause the formation of papules, crusts, thickened skin, as well as alopecia. The mites are often found in the feathered hair around the fetlocks of draft horses. As with other mites, ivermectin is the treatment of choice. Culicoides, Haematobia irritans (the Horn fly) and onchocerciasis often cause dermatitis at the ventral midline of horses.

193

It is a rainy April and you are visiting a horse farm to evaluate a horse with itchy and flaky skin lesions on the pastern and mild lameness. On examination, you see an exudative seborrheic dermatitis of the plantar aspect of the pastern that is slightly malodorous. Which of the following is a term used to describe this condition in horses?

a. Ringbone

b. Sweeney

c. Scratches

d. Sweet itch

e. Summer sores

c. Scratches

Scratches is a condition of chronic seborrheic dermatitis of the palmar/plantar aspect of the pastern. The condition is sometimes referred to by several other names including "grease heel", "dermatitis verrucosa", "dew poisoning" and "mud fever". It is not specific to the underlying infectious cause but the condition is generally associated with horses kept in wet or muddy environments.

Summer sores are caused by Habronema spp. and Draschia spp. stomach worms of the horse. The larvae in feces are ingested by the maggots of flies, and the flies can deposit them at susceptible moist skin areas, damaged skin areas, or mucous membranes where the larvae cause an eosinophilic granuloma as a reaction to their migration.

Sweet itch results from a Type 1 allergic reaction to Culicoides spp. Clinical signs of sweet itch are usually in the form of self-trauma due to pruritus.

Sweeney is the common name for shoulder atrophy in the horse. The muscle atrophy is caused by damage to the suprascapular nerve which innervates to the infraspinatus and supraspinatus muscles.

Ringbone refers to osteoarthritis or bony exostosis in the pastern (high ringbone) or coffin (low ringbone) joints.

194

A 10-year old gelding presents for salivation and vesicular lesions on the tongue and on the inside of the mouth. A full physical exam shows that there are similar lesions on the feet of the horse as well. Which of the following is a possible diagnosis for this horse?

a. Foot-and-mouth disease

b. Vesicular exanthema

c. Swine vesicular disease

d. Vesicular stomatitis

d. Vesicular stomatitis

The correct answer is vesicular stomatitis. Vesicular stomatitis is characterized by vesicle lesions on the tongue, inside of the mouth, teats, and feet. Besides horses, cattle, sheep, goats, and pigs are susceptible to the disease. The disease is differentiated from the others listed because horses are not naturally susceptible to the other diseases. The absence of papules and pustules allows us to differentiate vesicular stomatitis from horsepox.

195

An adult horse presents to you for crusting lesions along the ventral midline. The lesions are relatively not pruritic and are very round and focal. What is the most likely cause of these lesions?

a. Habronema

b. Culicoides

c. Hypoderma

d. Onchocerca

e. Haematobia

e. Haematobia

The correct answer is Haematobia. Haematobia irritans is a bigger problem in cattle than horses (they reproduce in cow feces) but can affect horses, especially ones that are near cattle. It typically causes ventral midline dermatitis with wheals with a central crust that progress to alopecia and ulceration with fairly focal lesions, rather than more diffuse lesions caused by culicoides. Onchocerca can cause dermatitis in the horse due to hypersensitivity to dying microfilariae. Lesions include alopecia and scaling of the ventral midline, face, and pectoral region. Often lesions are diamond shaped, and there may be a ""bull's eye"" lesion on top of the head. Onchocerca is nonseasonal, in contrast to culicoides hypersensitivity, and variably pruritic. Ocular lesions can also occur with Onchocerca including uveitis, conjunctivitis, and keratitis. Culicoides hypersensitivity, also referred to as sweet itch, occurs due to allergy to the saliva of the gnat. It recurs seasonally in the warmer months and tends to worsen with age. Typically, horses are pruritic and develop lesions on the poll, mane, and tail from self trauma, although ventral midline dermatitis can occur as well. More chronically, scarring can occur. Treatment is to decrease exposure to the gnat and to treat with steroids. Habronemiasis is a condition where larvae of the stomach worm that emerge from flies feeding on pre-existing wounds or genitalia or eyes, then migrate into the tissue and cause a granulomatous reaction. Inside the granulomas, you can find dead larvae. Lastly, Hypoderma is a bigger problem in cattle but can occur in horses and typically creates nodules on the back that have a pore on top.

196

A Thoroughbred race horse has been moved from California to Florida in July and is experiencing poor performance, exercise intolerance and tachypnea. You observe the horse working out one hot afternoon and see these signs, but you also note that the horse is not sweating. You check the rectal temperature and note that it is 104F (40 C). What is the diagnosis?

a. Anhidrosis

b. Hypothyroidism

c. Diabetes insipidus

d. Equine Cushing's

e. Influenza

a. Anhidrosis

Anhidrosis is the inability to sweat, which can be fatal if not addressed. The cause is unknown. It tends to occur in hot humid climates, and may occur in horses raised in the climate, or more commonly, horses brought into the climate. The most successful treatment is to move the horse back to a more favorable climate.

197

What stimulates antidiuretic hormone (ADH) secretion in the horse?

a. Hyperosmolality and increased circulating blood volume

b. Hypoosmolality and decreased circulating volume

c. Hyposomolality and increased circulating volume

d. Hyperosmolality and decreased circulating blood volume

d. Hyperosmolality and decreased circulating blood volume

The correct answer is hyperosmolality and decreased circulating volume. In the horse, as in other species, ADH increases renal water reabsorption and urine osmolality by increasing permeability of the collecting tubules. Osmoreceptors in the hypothalamus detect subtle changes in plasma osmolality. If osmolality rises, you will hope to see ADH secretion so that the urine excreted would be more concentrated. The same is true if circulating volume decreases; thus, a lesser volume of water would be lost. When ADH secretion does not occur or if the kidneys are unable to respond to ADH, this is likely diabetes insipidus, and animals will be very polyuric, polydipsic and have extremely dilute urine.

198

You are out in the field and you notice a horse tilt his head up and curl back his lips in a manner that makes it appear to be "grimacing". You identify this as a flehmen response. What is thought to be happening when this response occurs?

a. This is a pathognomonic sign of yellow star thistle toxicity

b. Scents are moved to the vemeronasal organ

c. This is a sign of secual interest or arousal and you need to be careful if the horse is near by

d. This is a display of aggression or dominance that a horse will display when it detects the presence of other stallions

e. This is a sign of colic

b. Scents are moved to the vemeronasal organ

The flehmen response, as described in the question, helps animals trap pheromone scents in the vomeronasal organs (VNOs) so they can be analyzed more closely. Pheromones are the chemical signals emanating from other animals.

When a horse draws in an organic odor, he curls up his lip to temporarily close the nasal passages and hold the particles inside. The upward head tilt seems to help the airborne molecules linger in the VNOs, which are located under the floor of the horse's nasal cavity.

While sex pheromones are the most common flehmen trigger, they are not the only ones, and the response itself does not indicate sexual interest.

199

An 8-year old Thoroughbred horse presents to you for evaluation of skin lesions. On exam, you see the lesions shown in the photo. Which of the following toxins is most likely responsible for these lesions?

a. Slaframine

b. Blue-green alga

c. St. John's wort

d. Cantharidin

Q image thumb

c. St. John's wort

This image shows a horse with skin sloughing due to cutaneous photosensitization. St. John's wort acts as a primary photosensitizer and can lead to photophobia, conjunctivitis, sloughed skin, and icterus. Blue-green algae cause sudden death. Slaframine causes hypersalivation and cantharidin causes colic.

200

A 1-year old Appaloosa gelding presents for generalized crusting lesions around the mucocutaneous junctions of its head and along its ventrum. A biopsy of the lesions shows acantholytic cells and a diagnosis of Pemphigus foliaceus. What is the treatment for this disease?

a. Immue suppressive doses of corticosteoids

b. Topical anti-fungals

c. Penicillin

d. Anti-inflammatory doses of corticosteroids

e. Systemic anti-fungals

a. Immue suppressive doses of corticosteoids

The correct answer is immune suppressive doses of corticosteroids. Pemphigus foliaceus is an autoimmune disease in which antibodies are formed against the intercellular adhesin proteins. In horses, this disease causes crusting lesions of the head, limbs, and ventrum. Definitive diagnosis is found on biopsy of the skin showing acantholysis. There are two forms of the disease in horses. The juvenile form may result in spontaneous remission and carries a good prognosis. The adult form of the disease carries a worse prognosis.

201

Equine Cushing's disease is most commonly due to _________?

a. Pancreatic tumor

b. THyroid tumor

c. Adrenal tumor

d. Pituitary tumor

d. Pituitary tumor

The correct answer is pituitary tumor. Equine Cushing's disease is usually due to a pituitary adenoma of the pars intermedia secreting ACTH and leading to increased cortisol secretion from the adrenal glands.

202

A miniature horse presents for colic. What cause of colic are they prone to?

a. Small colon impactions

b. Small intestinal obstructions

c. Entrapment at the epiploic foramen

d. Enteroliths

a. Small colon impactions

The correct answer is small colon impactions. Just a fun fact that is good to know.

203

Which is not a common side effect of aminoglycoside therapy?

a. Hepatotoxicity

b. Vestibulotoxicity

c. Nephrotoxicity

d. Ototoxicity

a. Hepatotoxicity

The correct answer is hepatotoxicity. Ototoxicity, nephrotoxicity, and vestibulotoxicity have all been associated with aminoglycoside use. An example of an aminoglycoside is gentamicin or amikacin.

204

An 11-year old Peruvian Paso presents with a history of progressive weight loss. Serum chemistry shows elevation in sorbitol dehydrogenase, lactate, alkaline phosphatase, and a decrease in albumin. A vast amount of Crotalaria spp. is seen in the pasture. What type of toxin does Crotalaria spp. possess?

a. Nitrate

b. Cyanide

c. Organophosphate

d. Pyrrolizidine alkaloid

d. Pyrrolizidine alkaloid

The correct answer is pyrrolizidine alkaloid. The clinical signs described are typical for pyrrolizidine alkaloid toxicity. Consumption of this plant typically results in abnormalities in hepatic cell division; thus resulting in large hepatocytes known as megalocytosis.

205

Physical characteristics of a premature foal include all of the following EXCEPT:

a. Laxity of flexor tendons

b. Pliant floopy ears

c. Short silky hair coat

d. Immature hippomane formation

 

 

d. Immature hippomane formation

A premature foal is typically defined as a foal born before 320 days of gestation and demonstrating physical characteristics such as a short silky hair coat, soft pliant ears, laxity of the flexor tendons, a soft muzzle, and incomplete ossification of the carpal and tarsal bones. The hippomane is not part of the fetal anatomy but is the collection of cellular material and secretions found within the allantoic fluid.

206

You are examining a 3 year old Thoroughbred gelding that just completed a race and notice discharge from the nostrils (see image). What would be an appropriate treatment for this horse prior to the next race?

a. Furosemide

b. VItamin K

c. Plasma transfusion to replace clotting factors

d. Vasopressin

e. Whole blood transfusion

Q image thumb

a. Furosemide

In this instance, the discharge is blood, with the most likely diagnosis being exercise-induced pulmonary hemorrhage (EIPH). One of the most commonly administered medications for EIPH is furosemide, which seems to decrease the incidence or lessen the severity of bleeding. The exact mechanism by which this occurs is not completely known but may be associated with reduced pulmonary capillary pressure.

207

A 4 month old male Arabian presents with a one-week history of ataxia, hypometria, conscious proprioceptive deficits, and generalized weakness. On physical exam, there is no muscle atrophy or cranial nerve deficits and normal mentation. Additionally, the temperature is 100.2F (37.9 C). Which of the following is not a likely differential based on the clinical signs?

a. Occupitp-atlanto-axial malformation (OAAM)

b. Cervical vertebral stenotic myelopathy

c. Equine degenerative myeloencephalopathy

d. Cerebellar abiotrophy

d. Cerebellar abiotrophy

The correct answer is cerebellar abiotrophy. The cerebellum is responsible for the coordination and regulation of range, rate, and strength of movement along with balance and posture. Clinical signs associated with cerebellar disease include intention tremors, hypermetria, hypometria, and ataxia. In addition, weakness is not observed with cerebellar abiotrophy. Mentation will be normal if the disease is strictly confined to the cerebellum. The key clinical sign not observed in this question is intention tremors. The clinical signs and presentation are definitely compatible with equine degenerative myeloencephalopathy, cervical vertebral myelopathy, and occipito-atlanto-axial malformation (OAAM). Computerized tomography (or radiography) is needed to rule in or rule out cervical vertebral myelopathy and OAAM. OAAM is relatively rare, but is most frequently observed in Arabian foals. These foals may be born dead, or may develop ataxia at several months of age. Histopathologic examination is the only way to definitively diagnose equine degenerative myeloencephalopathy (lesions in caudal brainstem nuclei and spinal cord).

208

The drug of choice to treat babesiosis in the horse is _____________.

a. Doxycycline

b. Enrofloxacin

c. Imidocarb

d. Amitraz

e. Nitrofurantoin

c. Imidocarb

The correct answer is imidocarb.

209

Which of these urine specific gravities would you most likely find in a horse with chronic renal insufficiency and moderate azotemia?

a. 1.001

b. 1.004

c. 1.042

d. 1.012

e. 1.024

d. 1.012

The correct answer is 1.012. Isosthenuria would be expected in any horse with chronic renal insufficiency that is causing azotemia. Isosthenuria is typically defined by a urine specific gravity of about 1.008-1.015.

210

Endotoxemia is a term applied when an animal exhibits multiple adverse clinical signs including one or more of the following: fever or hypothermia, leukopenia, tachycardia, tachypnea, obtundation, and a change in gut motility. These physiologic effects are caused by what?

a. An adverse reaction to aspirin, phenylbutazone or other NSAIDs

b. Cell wall components of Gram positive bacteria

c. Exotoxins from Clostridial organisms

d. Bacterial lipopolysaccharide

e. DNA from Gram negative bacteria

d. Bacterial lipopolysaccharide

he cell walls of all Gram negative bacteria contain varying amounts of lipopolysaccharide, which in turn varies in its potency to create adverse reactions in animals. The signals have evolved on monocytes and macrophages to warn the animal when a Gram negative bacterium has gained access. When the reaction to this signal is overzealous, a cascade of adverse physiologic reactions can occur.

211

You are examining a 7-year old Thoroughbred gelding for a 5-day history of anorexia and jaundice. Which of the following enzymes would you consider to be liver specific in the horse?

a. Gamma Glutamyl Transferase (GGT) and Alanine Aminotransferase (ALT)

b. Alkaline Phosphatase (ALP) and Sorbitol Dehydrogenase (SDH)

c. Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST)

d. Sorbitol Dehydrogenase (SDH) and Gamma Glutamyl Transferase (GGT)

d. Sorbitol Dehydrogenase (SDH) and Gamma Glutamyl Transferase

You have to read the possible answers carefully in this question and recall which enzymes are liver-specific in the horse. In this instance, SDH and GGT are both liver-specific; SDH is found in the liver of all animals. An increase in serum SDH concentration suggests hepatocellular injury. Elevation in serum GGT is predominately associated with biliary epithelial cells and is also liver-specific.

The other enzymes listed may be increased with liver disease but may also arise from bone (ALP) or muscle (ALT, AST).

212

Clostridium difficile is a spore-forming bacteria commonly associated with enterocolitis and diarrhea in adult horses and foals. Which of the following statements is NOT correct in regard to C. difficile in horses?

a. Transmission of C. difficile occurs via the oral-fecal route

b. Administration of non-steroidal anti-inflammatory medications.  For example, flunixin meglumine, is a risk factor for the development of C. difficile enterocolitis

c. The 2 main virulence toxins are toxin A and toxin B

d. C. difficile is a Gram-positive, rod shaped, obligate anaerobe

e. C. difficile can survive for prolonged periods of time in the spore form

b. Administration of non-steroidal anti-inflammatory medications.  For example, flunixin meglumine, is a risk factor for the development of C. difficile enterocolitis

The correct answer is NSAID treatment is a risk factor for the development of C. difficile enterocolitis. Remember all the other answers are correct, so hopefully you can take away some of these important facts from this question. Risk factors for the development of disease include antibiotic treatment and hospitalization, but does not include administration of NSAIDs.

213

A 14-year old 500 kg multiparous mare presents for a 3 hour history of moderate to severe colic. Her current foal is 2 weeks of age. Upon physical examination the mare is uncomfortable with a heart rate of 70 beats/min, respiratory rate of 16 breaths/min and rectal temperature of 98.4F (36.9 C). A nasogastric tube is placed with no net gastric reflux obtained. A large gas filled section of intestine is noted on rectal examination. You administer 5 mg of detomidine IV which provides only brief sedation. Based on this limited information, what is the most likely cause of these clinical signs?

a. Large colon volvulus

b, Small intestinal strangulation

c. Hemorrhage from rupture of the uterine artery post-foaling

d. Small intestinal entrapment within the epiploic foramen

e. Large colon impaction

a. Large colon volvulus

The correct answer is large colon volvulus. Typically, horses with this problem demonstrate rapid onset of severe unrelenting pain and often occurs in postpartum broodmares. Gas distension of the colon may be significant and result in respiratory compromise because the distended colon presses on the diaphragm. Gastric reflux may not be present as the small intestine may not be obstructed in this process.

This is a surgical emergency; if surgery or necropsy is performed, the volvulus is typically located at the mesenteric attachment of the colon to the dorsal body wall. Because of the rapid onset, the prognosis is guarded to poor in many cases.

214

Rhodococcus equi causes pneumonia in foals, characterized by pulmonary abscesses. Which of the following drugs would be most effective in treating R. equi foal pneumonia?

a. Oxytetracycline

b. Ampicillin

c. Penicillin

d. Erythromycin

e. Metronidazole

d. Erythromycin

Erythromycin is often used in combination with rifampin. Others used are clarithromycin or azithromycin.

 

215

What is the duration of a mare's estrus?

a. 14 days

b. 6 days

c. 1 day

d. 12 hours

e. 20 days

b. 6 days

The correct answer is 6 days. Estrus in a mare can last 2-10 days but, on average, is 6 days long. The mare is a polyestrous animal from the beginning of spring through summer. The estrous cycle's duration lasts 19-26 days.

216

A horse with peripheral vestibular disease will not have this clinical sign.

a. Conscious proprioceptive deficits of the pelvic limbs

b. Left-sided head tilt

c. Nystagmus

d. Facial nerve paralysis

a. Conscious proprioceptive deficits of the pelvic limbs

The correct answer is conscious proprioceptive deficits of the pelvic limbs. Usually the CP deficits will be on the side of the lesion. So you can expect to see right-sided CP deficits on a right-sided central vestibular lesion. Head tilt, facial nerve paralysis, and nystagmus are non-specific signs of vestibular disease. However, they do help you determine on which side the lesion is located. Quick note: if there are multiple cranial nerves paralyzed then you should start thinking this could be central. A right sided head tilt, right sided nerve paralysis, and nystagmus with the fast phase to the left will indicate a right-sided lesion. Abnormal mentation or seizures along with other vestibular disease signs would imply central vestibular disease.

217

A 5 year old Standardbred from the east coast presents for progressive ataxia. On physical exam, there are areas of muscle loss noted around the left gluteal region of the horse. A neurologic exam revealed knuckling over on all four limbs, stumbling of limbs when walked in a circle, and a dysmetric gait. Given these clinical signs what is the most likely differential?

a. Caudal equina neuritis

b. Cervical vertebral stenotic myelopathy

c. Equine protozoal myeloencephalitis

d. Verminous myelitis

c. Equine protozoal myeloencephalitis

The correct answer is equine protozoal myeloencephalopathy. If at any time you observe vague asymmetric/multifocal neurologic clinical signs with focal muscle atrophy, this disease should be your top differential. Other potential clinical signs include hyporeflexia, spasticity, localized areas of sweating, cerebellar signs, head tilt, facial paralysis, circling, dysphagia, and blindness. EPM is caused by Sarcocystis neurona which is a protozoal organism that migrates randomly through the spinal cord and brain. This will result in damage of both white and gray matter. Cauda equina neuritis is an inflammation of the nerve roots (usually the cauda equina but sometimes cranial nerves) which results in lower motor neuron signs. You may see paresis and paralysis. Clinical signs include chewing the tail head, hypotonic anus, fecal retention, urinary incontinence (see urine scalding of the thighs), and hindlimb ataxia. Unfortunately, there is no good treatment. There are two forms of cervical vertebral stenotic myelopathy (aka Wobbler Syndrome). One form is called cervical vertebral instability. In this case, ventroflexion of the neck results in spinal cord compression. Most commonly affected sites are C3-4 and C4-5. The other form is known as cervical static stenosis. In this case, the compression is continuous regardless of the neck position. Clinical signs are usually in the form of a wide based stance, conscious proprioceptive deficits, ataxia, paresis, and spasticity which is worse in the hindlimbs. Verminous myelitis results from aberrant migration of parasites through the central nervous system. Clinical signs are very similar to that of EPM. However, EPM occurrence is much more common. Parasites known to undergo aberrant migration in the horse are Strongylus vulgaris, Micronema deletrix, Draschia megastoma, and Setaria spp.

218

A first-degree atrioventricular conduction block is characterized by _________.

a. An increase in the S-T interval

b. A lack of P waves

c. A widening of the QRS complex

d. An increase in the P-R interval

d. An increase in the P-R interval

The correct answer is an increase in the P-R interval. First-degree, second-degree, and third-degree blocks are associated with delays in conduction at the level of the atrioventricular conduction system.

In a first-degree block, the impulse is still able to transmit through the atrioventricular conduction system; however, it takes longer. Therefore, you will see an increased P-R interval.

Second-degree AV block is associated with intermittent AV block in which some but not all P waves are conducted to the ventricles.

In third-degree block, there is complete dissociation between the P waves and the QRS complexes. Frequently in third-degree block, the heart rate is slower than normal (20 beats/min) because a subservient pacemaker (i.e. in the AV node or ventricle) has to fire to cause ventricular contraction.

219

During a routine pre-purchase exam of a 24 year old Peruvian Paso, a harsh and decrescendo holodiastolic 3/6 murmur is auscultated with a point of maximum intensity at the left base of the heart. There were no other abnormal physical exam findings. What is the most likely diagnosis based on clinical exam and prognosis of this horse?

a. This horse most likely has aortic stenosis due to turbulent flow resulting in severe stenosis, which will limit the ability to perform

b. This horse most likely has aortic regurgitation due to degeneration of the aortic valve and should have no impacton performance

c. This horse most likely has pulmonic stenosis due to turbulent flow resulting in severe stenosis, which will limit the ability to perform

d. This horse most likely has pulmonic regurgitation due to degeneration of the pulmonic valve and should have no impact on performance

b. This horse most likely has aortic regurgitation due to degeneration of the aortic valve and should have no impacton performance

The correct answer is this horse most likely has aortic regurgitation due to degeneration of the aortic valve and should have no impact on performance. Given the location of the murmur and signalment, this should be the logical answer to choose. The thing you need to know is that aortic regurgitation in the horse is usually a degenerative change and there isn't much that can be done about it. Horses are rarely impaired by development of the murmur. In a true pre-purchase exam, you would be wise to recommend a full cardiac work-up to definitively diagnosis the source of the heart murmur. The potential buyer may decline further diagnostics, but at least you will have offered the choice and have provided the proper information to the client.

220

A horse is referred to your practice for further evaluation and treatment of glomerulonephritis. Which of the following is not a treatment option?

a. Long term furosemide administration

b. Plasma transfusion

c. Low protein diet

d. Corticosteroids

a. Long term furosemide administration

The correct answer is long term furosemide administration. Horses with glomerulonephritis are usually polyuric. Furosemide is only indicated for oliguric renal failure. The other choices are commonly used in the treatment and management of glomerulonephritis. A low protein diet will help decrease the amount of proteinuria and blood urea nitrogen circulating at any given time, therefore helping reduce the degree of azotemia.

221

Most equine uroliths are composed of which of the following substances?

a. Phosphate

b. Magnesium ammonium phosphate

c. Calcium carbonate

d. Cysteine

e. Calcium oxalate

c. Calcium carbonate

he correct answer is calcium carbonate. Equine urine contains high amounts of calcium carbonate. Magnesium ammonium phosphate (aka struvite crystals) is also occasionally noted in horse urine.

222

You examine a horse for lameness and find that the 8-year old gelding is lame on both forelimbs. The stride is short and choppy, and the horse is reluctant to move. There is an increased digital pulse in both forelimbs, and the horse is sensitive to tapping on the hoof wall. At rest he leans back and puts more weight on his rear limbs. The horse appears improved and moves much better following a nerve block of the foot using local anesthesia. You take radiographs (see image). What is the diagnosis?

a. Fracture of the third phalanx

b. Navicular disease

c. Sole abscesses

d. Laminitis with rotation of the third phalanx

e. Coffin joint sepsis

Q image thumb

d. Laminitis with rotation of the third phalanx

Laminitis, or founder, is severe and has progressed to the point of rotation of the third phalanx. The angle of the hoof wall surface and the dorsal third phalanx are no longer parallel. These radiographic findings along with the clinical signs are diagnostic for laminitis.

223

On a hot July day in Michigan, an adult horse develops acute depression, high fever (104.5F) and subsequently has profuse watery diarrhea. On presentation to your hospital, the horse's heart rate is 80 beats/min, respiratory rate is 36 breaths/min and temperature is 103.4F. After your physical examination, you perform some routine clinicopathologic tests with the below results:

PCV- 56%
Total Protein- 8 gm/dL
Lactate- 5.2 mmol/L
White blood cell count- 2500 cells/microliter
Neutrophil count- 625 cells/microliter with toxic changes
Band neutrophil count-300 cells/microliter

You have the horse moved to an isolation stall and also notice that it seems to be very sore in the forelimbs. Based on the clinical signs and examination, what would be a top-rule out and how would you confirm your suspicion?

a. Clostridium chauvoei type A, Supportive test - Measure clostridial toxins via ELISA

b. Neorickettsii risticii, Supportive test - a PCR of blood or feces

c. Cantaharidin toxicity (Blister beetle toxicity), Supportive test - Measure blood cantharadin concentrations

d. Salmonella typimurium, Supportive test - Culture of feces

b. Neorickettsii risticii, Supportive test - a PCR of blood or feces

The correct answer is Neorickettsii risticii, the causative agent of Potomac Horse Fever (PHF). The clues that best indicate PHF are the time of year (disease usually occurs in the summer in the northern states), the high fever and diarrhea, and the presence of laminitis. The horse is also dehydrated and has a profound leucopenia, both consistent with PHF. Salmonella also causes diarrhea and leucopenia, and could be a viable choice, but Salmonella can occur at any time of the year; moreover, laminitis is not as often seen with Salmonella. This question has a practical aspect to it as horses often present with the described history and physical examination findings, and the veterinarian has to decide if he or she wants to treat specifically for PHF; the drug of choice is oxytetracycline. In this clinical situation, you as a veterinarian would have to start treatment empirically as your PCR test will take several days to get results. The good news is that PHF is very susceptible to oxytetracycline.

224

Why are horses more predisposed to gastric ulceration as compared to other species?

a. They are easily stressed

b. They are hind gut fermentors

c. They constantly secrete gastric fluid

d. They are predisposed to gastric reflux disease

e. They have an underdeveloped gastric wall

c. They constantly secrete gastric fluid

The correct answer is they constantly secrete gastric fluid. This is unique to equids, as many other species only secrete gastric fluids in response to consumption of food items.

225

Rhodococcus equi causes pneumonia in foals, characterized by pulmonary abscesses. Which of the following drugs would be most effective in treating R. equi foal pneumonia?

a. Erythromycin

b. Penicillin

c. Oxytetracycline

d. Ampicillin

e. Metronidazole

a. Erythromycin

Erythromycin is often used in combination with rifampin. Others used are clarithromycin or azithromycin.

226

What is the main disadvantage of giving xylazine to a horse with acute colic?

a. Inhibition of intestinal motility

b. Laminitis

c. Masking of clinical signs and the need for surgical intervention

d. Cardiac arrhythmias

a. Inhibition of intestinal motility

The correct answer is inhibition of intestinal motility. When xylazine is given at 1.1 mg/kg it decreases the motility of the distal jejunum, cecum, and pelvic flexure for over 2 hours. Xylazine can also transiently decrease cardiac output in a potentially hypovolemic horse with colic. Conversely, xylazine is a potent analgesic and can provide immediate relief to a horse with abdominal pain.

227

All aminoglycosides have the potential for causing tubular nephrosis. Which of the following aminoglycosides is most nephrotoxic to horses?

a. Amikacin

b. Amphotericin B

c. Neomycin

d. Streptomycin

e. Gentamicin

c. Neomycin

The correct answer is neomycin. This is followed by gentamicin and then amikacin. Streptomycin is the least nephrotoxic aminoglycoside. Amphotericin B is an anti-fungal and not an aminoglycoside.

228

What is the most common clinical sign of guttural pouch mycosis in the horse?

a. Epistaxis

b. Facial rubbing

c. Vestibular signs

d. Sneezing

a. Epistaxis

The correct answer is epistaxis. This occurs due to the fungus eroding the wall of the carotid artery (usually internal carotid).

229

A 7-year old Arabian gelding is presented to you for clinical signs of fever and lethargy of 2 days duration along with signs of hind-limb ataxia and muscle fasciculations of the face and neck. The CBC and biochemistry profile are relatively normal and you decide to collect cerebrospinal fluid (CSF) from the lumbosacral space. Results of CSF analysis yields the following:

Color Clear
Total Protein 156 mg/dL (reference interval 50-80 mg/dL)
Total Nucleated Cell Count 40 cells/mcL (ref interval less than 5 cells/mcL)
Cytology Lymphocytic pleocytosis

Based on the clinical signs and CSF analysis, which of the following is the most likely diagnosis and the most appropriate diagnostic test listed to confirm your diagnosis?

a. Cervical Vertebral Malformation (CVM); Myelography of the cervical spine

b. Verminous encephalitis (Micronema deletrix); CUlture of CSF

c. Equine Protozoal Myelitis (EPM); Western Blot of CSF

d. West Nile Encephalitis (WNV); Serum Immunoglobulin M (IgM) capture ELISA

e. Equine Herpes Virus (EHV) Myeloencephalitis; Virus isolation of buffy coat, nasal swab and/or CSF

d. West Nile Encephalitis (WNV); Serum Immunoglobulin M (IgM) capture ELISA

The correct answer is WNV. This is a mosquito born flavivirus that affects horses in multiple areas of the United States. Clinical signs are variable and can be mild (muscle fasiculations, slight ataxia) to severe (recumbency). Of note, muscle fasiculations is somewhat characteristic of WNV but fever may be detected in all patients. A readily available diagnostic test is the serum IgM capture ELISA which will detect infection, even in the face of vaccination. There is a vaccine available for WNV, making the clinical presentation less common.

230

A 3-month-old paint colt presents to you after flipping over backward while being led by the owner the previous day. Clinical signs at the time of presentation are shown in the image (head tilt, flaccid ear, muzzle deviation). Based on the history and clinical signs, what cranial nerves are damaged and what is the most likely diagnosis?

a. Cranial nerves VII and VIII (left side); fracture of the basisphenoid bone

b. Cranial nerves V and VII (right side); atlanto-occipital malformation

c. Cranial nerves VII and VIII (right side); fracture of the basisphenoid bone

d. Cranial nerves V and VII (left side); atlanto-occipital malformation

e. Cranial nerves V and VIII (left side); fracture of the sphenoid bone

Q image thumb

a. Cranial nerves VII and VIII (left side); fracture of the basisphenoid bone

The correct answer is damage to cranial nerves VII (facial nerve) and VIII (vestibular nerve) on the left side caused by fracture of the basisphenoid bone. This is a common injury when a fractious young foal rears up and falls backward on the poll. The basisphenoid bone becomes injured resulting in injury to cranial nerves VII and VIII. Damage to the facial nerve results in the muzzle deviation (opposite direction of the side of injury, in this case deviated to the right), ptosis of the left eye and drooping of the left ear. Damage to the vestibular nerve results in the head tilt.

 

231

The most common conduction disorder in the horse occurs at the level of the _________.

a. Sinoatrial node

b. Purkinje fiber system

c. Bundle of His

d. Atrioventricular node

d. Atrioventricular node

The correct answer is the atrioventricular node. At the atrioventricular node, we see first-degree AV blocks, second-degree AV blocks, and third-degree AV blocks.

232

A 2-year old Standardbred gelding presents for a prepurchase exam. On auscultation you hear a loud grade IV/VI systolic murmur on the right thorax. An echocardiogram is performed, which is shown below. The cardiac chambers are labeled LV (left ventricle), RV (right ventricle), Ao (Aorta). What is your diagnosis?

a. Unremarkable echocardiogram

b. Tricuspid valve endocarditis

c. Ventricular septal defect

d. Patent ductus arteriosus

e. Subaortic stenosis

Q image thumb

c. Ventricular septal defect

The correct answer is ventricular septal defect. There is echo dropout immediately below the aortic valve and extending into the right ventricle. The auscultatory findings also fit with a VSD as the murmur is typically louder on the right. A PDA would cause a continuous heart murmur. There is no narrowing in the LV outflow tract so subaortic stenosis is not evident. There is no evidence of a vegetation or mass on the tricuspid valve so endocarditis is not correct.

A image thumb
233

A 12-year old mare presents for infertility and abnormal sexual behavior. On rectal palpation, you feel a large multicystic ovary and the other ovary feels very small. What is the most likely diagnosis?

a. Granulosa-thecal cell tumor

b. Ovarian hematoma

c. Cystic ovarian follicles

d. Ovaritis

a. Granulosa-thecal cell tumor

The correct answer is granulosa-thecal cell tumor. The clinical signs and palpation findings are both consistent with this diagnosis. The other choices listed may create a palpable ovarian mass but would not cause atrophy of the contralateral ovary and should not cause infertility.

234

Which of these urine specific gravities would you most likely find in a horse with chronic renal insufficiency and moderate azotemia?

a. 1.001

b. 1.012

c. 1.042

d. 1.024

e. 1.004

b. 1.012

The correct answer is 1.012. Isosthenuria would be expected in any horse with chronic renal insufficiency that is causing azotemia. Isosthenuria is typically defined by a urine specific gravity of about 1.008-1.015.

235

A 5-year old horse presents to for a gait abnormality. You observe the horse walking and note that when the horse lifts the left hindlimb, it draws the foot up sharply until it touches its abdomen and then strikes it violently toward the ground. What condition should you suspect?

a. Bone spavin

b. Stringhalt

c. Bog spavin

d. Sweeny

b. Stringhalt

Stringhalt is a myoclonic disease affecting one or both pelvic limbs. It causes spasmodic hyperflexion of the leg. The etiology is unknown but sweet pea poisoning is thought to be associated with the condition. Diagnosis is based on clinical signs, but electromyography can be used to confirm the diagnosis. Treatment involves tenectomy of the lateral digital extensor tendon; however, not all cases respond to the treatment.

Bog spavin, also known as tarsal hydrarthrosis, is often due to poor conformation and can result in increased synovial fluid formation. Both hindlimbs are usually affected. The horse is usually not lame from this condition. Distension may spontaneously appear and disappear in young horses.

Bone spavin is osteoarthritis of the hock.

Sweeney is supraspinatous contracture.

236

A horse presents with urticaria, edema of the extremities, petechiation of the mucous membranes, and a stiff gait. On physical exam, you suspect the horse to have purpura hemorrhagica. Which of these abnormalities is associated with purpura hemorrhagica?

a. Anemia

b. Thrombocytopenia

c. Prolonged PT and PTT

d. Hypoproteinemia

a. Anemia

The correct answer is anemia. Purpura hemorrhagica is a possible sequela of streptococcus equi infection exposure or vaccination. It develops from a Type III hypersensitivity resulting in immune complex deposition in blood vessel walls and vasculitis. Common clinical signs are as described in the question. This is a nonthrombocytopenic purpura (most horses will have a normal platelet count). Common findings include anemia, hyperproteinemia, hyperfibrinogenemia, hyperglobulinemia, and neutrophilia.

237

A 3-year old open beef cow presents as a result of lameness in her right hind limb. Upon physical examination, you notice an ulcerated necrotic lesion in the interdigital space. Which of the following is NOT a differential diagnosis?

a. Infectious bovine rhinotracheitis

b. Bovine viral diarrhea

c. Interdigital necrobacillosis

d. Malignant catarrhal fever

e. Foot-and-Mouth-disease

a. Infectious bovine rhinotracheitis

The correct answer is infectious bovine rhinotracheitis. There are three subtypes of infectious bovine rhinotracheitis identified. BHV-1.1 (Bovine herpes virus) is responsible for respiratory infections. BHV-1.2 may cause genital infections and respiratory disease. BHV-1.3 (reclassified recently and now called BHV 5) has been known to cause neurologic infections. Since most people are not aware of the reclassification, this aspect of the issue is unlikely to be questioned on a board examination. All of the other listed answer choices can cause the lesion described in the question.

238

A 5-year old cow presents with skin lesions confined to the nonpigmented areas (see image). The affected skin is dry and raised at the periphery. The skin of the teats appears dry. Which of the following could result in this presentation?

a. Ingestion of moldy feed containing aflatoxins

b. Ingestion of Quercus spp.

c. Ingestion of lupine

d. Ingestion of preridum aquilinum (bracken fern)

Q image thumb

a. Ingestion of moldy feed containing aflatoxins

This is a case of photosensitization based on the skin lesions confined to the nonpigmented areas. Primary photosensitization can occur when photodynamic agents are absorbed from the G.I. tract such as Hypericum perforatum (St. John's wort), Fagopyrum esculentum (buckwheat), Ammi majus (bishop's weed), and Cymopterus watsonii (spring parsley). Secondary (hepatogenous) photosensitization occurs when the liver's excretion of phylloerythrin is impaired due to liver damage. Phylloerythrin is derived from the breakdown of chlorophyll by rumen microbes. The best answer in this question is aflatoxins because they are known to cause liver damage.

Bracken fern toxicity causes acute hemorrhagic syndrome in cattle. Lupine toxicity primarily causes birth defects. Quercus (oak) toxicity causes GI and renal dysfunction.

239