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Flashcards in EQUINE Deck (53):
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

Q image thumb

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.