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Flashcards in Test 1- Respiratory Deck (180):

The upper respiratory tract is found where

In general the upper respiratory tract is the portion of the respiratory system located outside the thoracic cavity.


What are the 3 systems in the RT?

1. Conducting system

2.Transitional system

3.Exchange system


Conducting system

Conducting system: MORE ROSTRAL SYSTEMIncludes the nasal cavity, paranasal sinuses, larynx, trachea and bronchi. The mucosa of this system is primarily lined by pseudostratified ciliated epithelium and goblet cells.


Transitional system :

Transitional system : consists exclusively of bronchioles(lined by simple cuboidal epithelium) which are lined by Clara cells (detoxification of xenobiotics), non-ciliated secretory cells and only a few ciliated cells. Healthy bronchioles do not have goblet cells( goblet cells are in most other places).


Exchange system

Exchange system: Composed of alveolar ducts and millions of alveoli; thin-walled structures enveloped by a rich network of capillaries, the pulmonary capillaries. Alveoli are lined by epithelial
type I (membranous) and type II (granular) pneumocytes (also called pneumonocytes).


Type II- produce surfactant

Type I- more common


What is the blood supply to the lungs?

The lungs have a dual blood supply: Through the pulmonary arteries which conduct deoxygenated blood from
the right side of the heart, and the bronchial arteries, which carry oxygenated blood.


In addition to gas exchange, the respiratory system is also involved in

In addition to gas exchange, the respiratory system is also involved in phonation, olfaction, temperature regulation, acid–base balance, blood pressure regulation etc.


Normal Flora

Normal Flora – Restricted only to the most proximal region of the conductive system: nasal cavity, nasopharynx, larynx and trachea.
The distal portions of the respiratory tract are considered to be sterile.


The majority of the flora in the RT are ....

Even though the majority of the organisms of the normal respiratory flora are harmless others are potentially pathogenic; e.g.: Mannheimia haemolytica, Bordetella bronchiseptica.


2 Defense Mechanisms in the RT

 Non-specific (non immune- mediated):

  Mucous trapping

  Mucociliary clearance (mucociliary escalator- movement of the cillia moving the mucus)

  Phagocytosis

  Air turbulence (generated by coughing and sneezing).

*smokers loose the ability to do mucous trapping and mucocillary escalator- thus they can only use air turbulence and phagocytosis)

Specific (immune-mediated):
 Antibody production
 Antibody-mediated phagocytosis

 Cell-mediated immunity


Pulmonary Macrophages

  Alveolar Macrophages (“PAMs”)

  Intravascular Macrophages (“PIMs”> ruminants, cats, pigs and horses)- macrophages that live in the pulmonary capillaries- function is to get rid of bacteria, viruses that may reach the lungs through the blood


In dogs, humans and laboratory rodents the cells responsible for removing circulating bacteria and other particles from blood are

In dogs, humans and laboratory rodents the cells responsible for removing circulating bacteria and other particles from blood are the Kupffer cells (liver) and splenic macrophages.


NOT PIMs as in ruminants, cats, pigs and horses


What happens when animals have an infection?

Animals suffering from a respiratory viral infection
have notably suppressed defence mechanisms which make them susceptible to bacterial colonization within the airways.

 Viruses are not the only factor known to predispose to bacterial pneumonia, other causes are:

 Stress
 Dehydration
 Pulmonary edema
 Uremia
 Ammonia
 Immunosuppression/ immunodeficiency


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Pig normal lungs, AVC



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Nasal Cavity


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Ethmoidal hematoma –  MOST COMMON cause of epistaxis in horses


Pedunculated tumor-like lesion in older horses. The exact etiology of this lesion is unknown.


Lesion in the nasal tubinates



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Ethmoidal hematoma –  MOST COMMON cause of epistaxis in horses


Pedunculated tumor-like lesion in older horses. The exact etiology of this lesion is unknown.



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Fibrinous rhinitis – mid-sagittal section of the head – Calf with IBR


Infectious Bovine Rhinotracheitis (formation of diphtheritic membrane)-

happens a lot in younger cattle- CAUSED BY BOVINE HERPES VIRUS I



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fibrin hemoorhage- VERY CHARACTERISITIC of IBR


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Oestrus ovis, nasal bot in sheep – worldwide distribution


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Aberrant migration of Oestrus ovis larva, sheep-Texas A&M.

bot fly can go into the brain to cause an encephaltitis


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Atrophic rhinitis in pigs.


causes deventation in the snout


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Atrophic rhinitis in pigs.

Multifactorial disease in growing pigs. - There can be several organisms isolated

Currently is thought to be the result of a combined infection of Bordetella bronchiseptica and Pasteurella multocida types D and A.


Mostly in younger pigs

Damages the nasal turbinates

Post-mortem cut by the second molar- you will usually see symmetry


The atrophy is mostly seen in the ventral turbinates.


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Atrophic Rhinitis- the atrophy of the turbinates is caused by the decreased osteoclast activity


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Normal Pig


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The toxigenic strains of P. multocida produce cytotoxins which inhibit osteoblastic activity and promote osteoclastic reabsorption of the nasal turbinates. “The ventral scroll of the ventral nasal turbinate is the area most commonly and consistently affected”...




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Inclusion Body Rhinitis – Porcine Cytomegalovirus (suis herpesvirus 2 [SHV-2]) infection, Pig, AVC, OI-  Induces cytomegalolity in the cells. Glandular cells will have basophilic or amphophlici (grey) inclusion bodies- this confirms the diagnosis

Usually in pigs 3-5 weeks of age. Fatal systemic infection occurs occasionally in younger suckling pigs (less than 3 weeks of age)- this is where you see the most fataties.


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Nasal submucosal glands with large basophilic Intranuclear inclusions (SHV-2).


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Feline herpesvirus 1 (Feline viral rhinotracheitis [FVR]): rhinitis, conjunctivitis; usually in immunosupressed animals


Disease can be in the upper and lower RTS


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vesicles, tongue – Feline calicivirus, Noah’s Arkives- presents very simliar to FHV

Morphologic Diagnosis?



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Cat, feline calicivirus – ulcerative glossitis


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Feline Calicivirus (FCV). Mild oculonasal discharge in addition to vesicular and ulcerative stomatitis - diffuse interstitial pneumonia may also occur.


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Cat, diffuse interstitial pneumonia, FCV.

Diffucult to diagnosis grossly

Inflammation is mostly in the interstitium


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Granulomatous rhinitis, dog due to Rhinosporidium seeberi (aquatic protistan parasite)- in Lousisana, MI- dogs who like to play in ponds


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Guttural pouch tympany in a foal- YOUNG HORSES

guttural pouch is filled with air- NOT PAINFUL


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Strangles, Streptococcus equi, lymph node and guttural pouch involvement

this is extremely painful because this is inflammation(euchchitis= inflammation of the guttural pouch)

you will see neutrophils mostly in suppurative exudate




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Strangles, Streptococcus equi, lymph node and guttural pouch involvement


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Inflammation of the guttural pouch, horse (guttural pouch empyema) due to “strangles”-TAMU

Medial compartment of the guttural pouch(9-12) is associated with cranial nerves and the internal carotid- Thus THEY CAN HAVE NEURO SIGNS



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also called Inspissated exudate


Dried exudate


can look like hyaline cartilage- why they are called chondroids


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Guttural Pouch mycosis- fungus can damage internal cartoid a.(unique to fungul infection) - so they can present with epistaxis. This can happen in horses of any age.

- Caused by infection with Aspergillus fumigatus or other Aspergillus species.

- Involvement of cranial nerves (VII, IX, X, XI, XII) is common and result in a variety of clinical signs.

-Erosion of the wall of the internal carotid artery can lead to epistaxis or fatal hemorrhage


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Guttural pouch Mycosis- horse.


Multifocal, ulcerative and necrotizing eustachitis


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Guttural pouch mycosis, horse


blue arrows- lumen of the internal cartoid a.


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Guttural pouch mycosis, horse


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Guttural pouch mycosis

you can see blood in the lumen


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Guttoral pouch mycosis, horse


What is the difference between Type I and Type II pneumocytes

Type I- More numerous but more succeptible to injury

Type II- can proliferate after injury and can replace the Type I pneumocytes that are destroyed

-Produce surfactant


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Guttoral pouch mycosis, horse, AVC, Dr. A. Lopez.


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Guttoral pouch mycosis


Which special stains are often used to visualize fungi within tissue sections?

GMS (Gomori’s methenamine silver) stain and PAS (Periodic Acid Shiff) stain.


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Nasal Squamous Cell Carcinoma, Cat


slow to metasize, but they invade surrounding tissues


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Nasal neoplasia

Nasal carcinoma,
10 year-old dog, AVC


can lead to bleeding and secondary bacterial infections


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Enzootic nasal carcinoma (or adenocarcinoma), sheep mostly but can be in cattle

Etiology: Enzootic Nasal Tumor virus (ENTV, an ovine beta-retrovirus)


Tumors are rarer in large animals


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Necrotic laryngitis (Calf diphtheria)

Secondary infection by Fusobacterium necrophorum following trauma or viral infection (IBR). Can also occur as part of oral necrobacillosis in calves and swine.

Plaques of ulceration covered by fibrinonecrotic exudate- very characterisitic


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Laryngeal hemiplegia (paralysis) – “roaring” horses. Atrophy of the left dorsal cricoarytenoid muscle.

 Usually the result of an idiopathic neuropathy affecting the left recurrent laryngeal nerve.


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Tracheal collapse: Mainly in toy and miniature dog breeds; occasionally seen in horses, cattle and goats.


results in widening of the trachea


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Dorso-ventral flattening of the trachea and concomitant widening of the dorsal tracheal membrane, pony

May result in coughing and exercise intolerance/ respiratory distress


Mainly in toy and miniature dog breeds


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IBR- infectious bovine rhinotrachtitis, RED NOSE Cattle

Ulcerative and necrotizing laryngo-tracheitis- almost pathopneumotic

lesions in the upper respiratory tract and can lead to pneumonia; also can see edema of the mucosa


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Systemic Herpesvirus infection in neonatal calves

IBR- also can produce abortions and neo-natal death


Canine infectious tracheobronchitis (Kennel cough)

-A variety of infectious agents are often isolated from affected dogs but there is consensus that Bordetella bronchiseptica usually plays a primary role.

-CAV-2, CPIV-2 and to a lesser extend canine distemper virus and Mycoplasma spp., have predisposing roles.


chronic bronchiolitis-emphysema complex

Horses and ponies– chronic bronchiolitis-emphysema complex, “heaves”, “broken wind”, Recurrent Airway Obstruction (RAO). Asthma-like syndrome (used to be known as Chronic Obstructive Pulmonary Disease (COPD)


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Severe heaves. The head &neck are extended and the horse shows nasal flaring with mucoid nasal discharge


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‘‘Heave line.’’ The hypertrophy of external abdominal oblique muscles as a result of expiratory efforts suggests that the horse has been chronically affected by heaves.


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Reoccurent Airway Obstruction (RAO), Heaves. Mucous accumulation contributes to the lower airway obstruction in RAO.


“ Clinical signs are caused by resistance to airflow in the lung because of diffuse bronchoconstriction. They are usually worst in winter when horses stay housed indoors and the ventilation of barns is not optimal”

allergens in the environment trigger this


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horse, HE stained histo slide Exposure to aeroallergens are implicated in the pathogenesis of the disease.

not dry hay;


you will see eosinophils because there is an allergic reaction


Blood-Air Barrier

Blood-Air Barrier: Composed of the vascular endothelium, basement membrane of the endothelial cell, basement membrane of the type I pneumocyte and the cytoplasm of the of the type I pneumocyte.


Exercise-induced pulmonary haemorrhage (EIPH)

Exercise-induced pulmonary haemorrhage (EIPH): Relatively common condition in race horses.

-Follows strenuous exercise.

-Epistaxis is present in only 1-10% of affected horses.

-Frequency increases with age and the severity of exertion.

- Probably the result of marked elevations in arterial and capillary pressures during strenuous exercise.

- Haemorrhage occurs in the dorso-caudal portions of the caudal lung lobes.

-Massive pulmonary haemorrhage may be the only detectable lesion in horses that die during exercise .


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Epistaxis and pulmonary hemorrhage are relatively common in cattle with vena cava thrombosis


common in feedlot cattle


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pulmonary edema, pig

when you open the cavity, the lungs will not collapse- this is how you know there is edema. Also many times you will see rib impressions


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Pulmonary edema, pig


fluid can be present in the interstitum


Pulmonary edema

Main pathogenic mechanisms:

1. ↑ hydrostatic pressure (cardiogenic edema).

2. ↑ vascular permeability: Injury to the blood-air barrier

3. Obstruction to lymphatic drainage: Neoplasia

involving thoracic lymph nodes or vessels.


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chronic pulmonary edema and congestion


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horse with left sided congestive heart failure


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chronic pulmonary edema


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increased pulmonary alveolar macrophages


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HE-stain, dark brown pigment(hemosiderion) within the cytoplasm of alveolar macrophages, UCVM

Heart Failure Cells



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Iron (Perl’s) stain – Hemosiderin-laden macrophages (“heart failure cells” --> siderophages) within alveoli – UCVM.


What pigment is this?

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Pigmentary disturbances: Pulmonary anthracosis




you see this in poluated cities



-Incomplete expansion of the lungs or portions of the lungs.

-Pulmonary parenchyma appears dark-red and sunken in comparison to aerated lung. Consistency is fleshy and the lung tissue does not float.

-Congenital or acquired. Acquired can be divided in compressive (caused by space-occupying lesions like hydrothorax, hemothorax, pleuritis), massive (pneumothorax) or obstructive (inflammation, edema).

------- If congenital, the animal is born dead


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Pulmonary atelectasis – bovine fetus; also in stillborn animals



“Meconium is the dark-green mucilaginous material in the intestine of a full term fetus –a mixture of secretions from intestinal glands and amniotic fluid”


Meconium Aspiration Syndrome (MAS)

Meconium Aspiration Syndrome (MAS)” – well- described in human babies


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Patchy pulmonary atelectasis due to aspiration of meconium and amniotic fluid-calf, 1 day old, AVC.


Pulmonary Emphysema

 Def: Permanent enlargement of air-spaces distal to the terminal bronchiole, accompanied by destruction of alveolar walls”

 -It is thought to be an imbalance between proteases, particularly elastase and matrix metalloproteinases from a variety of sources are the likely culprits. Their concentrations are enhanced by neutrophil and macrophage activation induced in chronic bronchitis” –JKP, 2007 –G Maxie, ed.

-The emphysematous lung is dysfunctional since the loss of alveolar septa reduces the alveolar surface area->Reduction in gas exchange.

- In animals is always secondary to obstruction of outflow of air or agonal at slaughter.

- Frequent in animals with bronchopneumonia -> airflow imbalance-> the volume of air entering the lungs exceeds the volume exiting the lung during expiration.

-  Classified also as alveolar or interstitial (the latter mainly in cattle).


Most cases have exudate in the airways or inflammation


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Bullous emphysema: Large focal air-filled spaces (bullae) _>rupture may lead to fatal pneumothorax.


Cow with "fog fever"; cow pulmonary edema emphysema


alveolar emphysema- clear bubbles

The emphysema can get very large and involve neighboring alveoli(bullous emphysema)- these will decrease the negative pressure and you get pneumothroax



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Bovine, interstitial emphysema


connective tissue is extended and there are air bubbles


Guttural pouch inflammation


usually with strepococcus equi


What are the three most common Guttural pouch issues?

1. tympany

2. Guttoral pouch empyenga

3. Guttural pouch mycosis



  No universal classification in veterinary medicine –quite confusing.

  Right: Diagram of common patterns of pneumonia:

  A: Normal lung

  B: Suppurative


  C: Fibrinous bronchopneumonia

  D: Interstitial pneumonia

  E: Embolic pneumonia

  F: Granulomatous pneumonia


 Viral Pneumonias in cattle


 Infectious Bovine Rhinotracheitis (IBR): Caused by BoHV-1- mostly has lesions in the upper respiratory tract

 Para-influenza-3 virus (PI-3 virus) and Bovine Respiratory Syncytial virus (BRSV) cause a transient rhino-tracheitis and broncho-interstitial pneumonia with the formation of eosinophilic intracytoplasmic inclusions bodies in bronchial, bronchiolar and alveolar epithelial cells and alveolar macrophages. Formation of syncytial cells occurs in both, BRSV and PI-3 virus infection.

 BRSV and PI-3 should be considered in calves with necrotizing bronchiolitis

Diagnosis is confirmed by virus isolation, PCR or detection of viral antigens by fluorescence antibody test (FAT) or immunohistochemistry (IHC).


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BRSV, heifer, Cornell files – Syncytial cells


greyish discoloration is normal in ruminats

There are rib impressions- that tells us that the lungs are enlarged


syncital cells in the lower right- they have mulitple nuclei


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BRSV- damage to the respiratory epithelium; more syncitum cells


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Bovine enzootic pneumonia (chronic suppurative bronchopneumonia)

Disease caused by a variety of etiologic agents which include respiratory viruses, Mycoplasmas, Chlamydophila, followed by opportunistic bacteria such as Pasteurella multocida,Arcanobacterium pyogenes, Histophilus somni, Mannheimia haemolytica and E.coli.

Calves with bovine leukocyte adhesion deficiency (BLAD), which prevents the migration of neutrophils from the capillaries, are highly susceptible to bronchopneumonia.

This can be an accidental finding- can be subclinical


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Chronic suppurative bronchopneumonia, Calf, OVC.


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Chronic suppurative bronchopneumonia, Calf,



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Abscessation and bronchiectasis( look like absycesses that can be differeniated via histology) are Common sequels of chronic suppurative pneumonia.


Pneumonic mannheimiosis (“shipping fever”)

-Acute respiratory disease that occurs in cattle several days or weeks after shipment.

- Because Mannheimia haemolytica (formerly Pasteurella haemolytica) is typically isolated the term penumonic mannheimiosis or pneumonic pasteurellosis have been used.

-Most economically important respiratory disease of cattle in North America, particularly in feedlot cattle.


Characterisitc= fibrinous bronchopnuemonia


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Fibrinous bronchopneumonia, OVC.

lots of fibrin- characterisitic


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Pneumonic mannheimiosis, steer, from McGavin.


bluish discoloration/uleration and on the surface, you see lots of fibrin


differential dx: Histophilius somni- looks just like this


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Pneumonic mannheimiosis: Marbling appearance of the
pulmonary parenchyma.




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Mannheimia haemolytica biotype A, serotype 1 is responsible for the severe pulmonary lesions (areas of necrosis etc.)

What type of necrosis? fibrinous nerotizing pneumonia- loss of microscopic details, but perservation of the over all archetecisure


Respiratory histophilosis

Part of the Histophilus somni disease complex (TME, pneumonia, pleuritis, myocarditis, arthritis, abortion etc.,).

  May cause suppurative or fibrinous bronchopneumonia. The later may be undistinguishable from the fibrinous bronchopneumonia caused by Mannheimia haemolytica.


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Fibrinous pneumonia, cattle-Cornell files


Mycoplasma bovis pneumonia

  Important cause of chronic respiratory disease in North America „s feedlot


  The organism causes a chronic necrotizing bronchopneumonia which is quite characteristic.

 M. bovis also causes severe chronic fibrinous arthritis.


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Chronic necrotizing bronchopneumonia, heifer, UCVM. Mycoplasma bovis was cultured from the lesions, OI, 2008.


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Mycoplasma bovis


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Necrotizing bronchopneumonia, heifer,


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Positive immunoperoxidase staining of M. bovis antigens, from McGavin’s, 2012


Bovine TB

Caused by M. bovis. It has been suggested that the term TB should be limited to diseases caused by M. tuberculosis (human) and M. bovis (cattle); other conditions should be referred as “Mycobacteriosis”.

In North America the disease has been almost eliminated but there still outbreaks that often originate from wild life (M. bovis not only affects cattle and humans but also deer, elk, bison etc.wild ruminants).

Lesions are more common in retropharyngeal lymph nodes, lungs, thoracic and mesenteric lymph nodes.

Lesions in cervids often contain prominent suppurative exudate and may resemble abscesses...


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Multifocal granulomatous pneumonia, M. bovis, cow, Dr. King-Cornell’s file.


Verminous bronchitis/ pneumonia

In cattle is caused by infection with Dictyocaulus viviparus. Varies from interstitial pneumonia (larval migration) to chronic bronchitis (intrabronchial adult parasites) to granulomatous pneumonia (eggs, dead larvae).


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Dictyocaulus filaria –sheep, goats Dictyocaulus arnfieldi –equids (horses, donkeys)


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Terminal bronchi from the right caudal lung lobe, pig. Slaughterhouse specimen, St. Kitts. Lung worms are admixed within slightly turbid mucoid exudate. Morphologic dx?.., etiologic dx?...


Atypical Interstitial Pneumonia (AIP) of cattle

 Pneumonias that did not fit any of the “classical” forms of pneumonia

 Characterized by the presence of edema, interstitial emphysema, hyaline membranes, type II pneumocyte hyperplasia and interstitial fibrosis with cellular infiltrates

 These types of pneumonias have specific etiologies.

 Investigators have proposed that these syndromes previously clustered under AIP be named according to their specific cause or pathogenesis.


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Diffuse alveolar damage –formation of hyaline membranes –


Atypical Interstitial Pneumonias - common syndromes:

 Bovine pulmonary edema & emphysema (“fog fever”)

  Extrinsic allergic alveolitis (hypersensitivity pneumonitis)

  Reinfection syndrome (hypersensitivity to Dictyocaulus sp. or BRSV).

  Milk allergy: type I hypersensitivity in cows sensitized to their own milk casein and lactalbumin.

  Ingestion of moldy potatoes  contain 4-ipomeanol which is metabolized by mixed function oxydases in the lung (Clara cells) to a potent pneumotoxicant.


“Fog Fever”

Bovine pulmonary edema & emphysema (“fog fever”)occursin cattle grazing “fog” pastures (re- growth pasture after a hay or silage has been cut or lush green grass). L- tryptophan present in the pasture is metabolized in the rumen to 3- methylindole → absorbed into the blood and carried to the lungs → metabolized by the mixed function oxidases of non-ciliated bronchiolar epithelial cells (“Clara” cells) into a highly pneumotoxic compound that causes extensive necrosis of bronchiolar epithelial cells and type I pneumocytes (diffuse alveolar damage).


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"fog fever"


“Extrinsic Allergic Alveolitis”

(hypersensitivity pneumonitis)

  Common; mainly seen in adult dairy cows in the winter. The human counterpart is referred to as “farmer‟s lungs”.

  Type III hypersensitivity reaction to inhaled organic antigens, most commonly fungal spores present in moldy hay (local deposition of Ag- Ab complexes in the lungs).

 Gross lesions vary from subtle gray subpleural foci of granulomatous inflammation to severe lesions in which the lungs acquire a “meaty appearance” due to alveolar epithelial hyperplasia, interstitial inflammation and fibrosis.


Pathogenesis of toxic and allergic pneumonias (“AIP”) in cattle

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Viral pneumonias:

Viral pneumonias: Like in cattle PI-3 virus and RSV can produce pneumonitis in sheep.

Maedi (maedi-visna): Lifelong, persistent disease of sheep that occurs in most countries with the exception of Australia and New Zealand. It is also known as Ovine Progressive Pneumonia (OPP).

The disease is caused by a retrovirus of the lentivirus subfamily (ovine lentivirus) similar to the agent of CAE. Infection results in a lymphocytic interstitial pneumonia (LIP).

The virus may also cause a non-suppurative encephalitis (Visna), lymphocytic arthritis, lymphofollicular mastitis and vasculitis.

Maedi is characterized by dyspnea and an insidious slowly progressive emaciation despite good appetite.

In goats, CAE virus can cause a lymphocytic interstitial pneumonia similar to OPP in sheep.


Chronic enzootic pneumonia:

Multifactorial disease –rarely fatal. In general it affects animals younger than 1-year-old. Etiologic agents include Mannheimia haemolytica,

Pasteurella multocida, PI-3, adenovirus, reovirus, RSV, Chlamydophila, and Mycoplasmas (mycoplasma ovipneumoniae).


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Suppurative bronchopneumonia, sheep – Pasteurella multocida – from McGavin’s.


Ovine pneumonic Mannheimosis

Similar to shipping fever in cattle.


Septicemic pasteurellosis

 Septicemic pasteurellosis: Caused by
 Mannheimia haemolytica (biotype A) usually in lambs under 3


 Bibersteinia (Pasteurella) trehalosi (biotype T) usually in lambs 5 to 12 months-old.

Lesions: necrotizing pharyngitis and tonsilitis, septicemia with disseminated intravascular thrombosis and bacteremia.


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Multifocal subpleural pneumonitis – Muellerius capillaris sheep


Viral pneumonias:

Viral pneumonias: Equine viral rhinopneumonitis (EHV-1, EHV- 4) and equine influenza are important diseases in horses worldwide. In addition, equine viral arteritis (EVA) virus and equine adenovirus can also cause pneumonia in horses.

These viruses often cause only a transient broncho-interstitial pneumonia but impair the pulmonary defences and make horses susceptible to secondary bacterial pneumonias (P. Multocida, Streptococcus spp., E.coli, Klebsiella pneumoniae, Rhodococcus equi etc.).

It has also been suggested that viral respiratory infections may predispose horses to “airway hyper-responsiveness” and Recurrent Airway Obstruction (chronic bronchiolitis-emphysema complex, “heaves”).


Equine Viral Arteritis (EVA) virus

Equine Viral Arteritis (EVA) virus – Arterivirus. Sporadic pansystemic disease of foals and horses: May result in interstitial pneumonia with vasculitis, pulmonary edema, hydrothorax and hydroperitoneum.


Equine Morbillivirus (Hendra virus disease)

Equine Morbillivirus (Hendra virus disease): Fatal respiratory disease in horses and humans (high mortality rates were seen in both horses and humans) which appeared in 1994 in Australia. Classified as a Morbillivirus, subfamily Paramyxoviridae. Affected horses have severely edematous lungs. Histologically there is vasculitis and the presence of multinucleated syncytial cells, typical of morbillivirus infections, in the endothelium of small pulmonary blood vessels and alveolar capillaries. No inclusion bodies are seen. Clinical signs are non-specific and include fever, anorexia, respiratory distress and nasal discharge


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Interstitial pneumonia-foal, Equine Viral Rhinopneumonitis, Texas A&M, JE.


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Interstitial pneumonia due to adenovirus or Pneumocystis carinii Infection are common complication in Arabian foals with SCID (Inherited disorder- autosomal recessive trait- characterized by lack of B and T lymphocytesdie before 5 months of age)


very common in HIV- very similar disease reported in Jack Russell Terriers


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 Pneumocystosis, Pig, AVC. Foamy( due to Fungi) eosinophilic proteinaceous material within alveoli. Fungal organisms are detected with Gomori’s methenamine silver stain (GMS).


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Adenovirus infection, foal, HE.


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Interstitial pneumonia due to Pneumocystis carinii infection with concomitant Rhodococcus equi infection in a foal (Arabian CID foal).


Rhodococcus equi

Rhodococcus equi

Important cause of morbidity and mortality in foals worldwide.

Facultative intracellular gram positive bacterium that causes two major clinical syndromes.

The organism may become enzootic in farms where the organisms has been shed earlier by affected foals.

Virulence factors encoded by plasmids (virulence-associated proteins) appear to be responsible for the survival of the organism within macrophages (avoid phagocytosis by inducing defective phagosome-lysosome fusion).


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6-week-old foal, Chronic pyogranulomatous pneumonia –Rhodococcus equi,


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6-week-old foal, Chronic pneumonia –Rhodococcus equi,
Mdx: Pyogranulomatous pneumonia(not suppuralative)

Cytokines, lysosomal enzymes and bacterial toxins are responsible for extensive caseous necrosis of the lungs and recruitment of large numbers of neutrophils, macrophages and giant cells containing numerous intracytoplasmic organisms. Affected foals develop chronic coughing and weight loss.

“Any foal with bronchopneumonia unresponsive to routine broad-spectrum antibiotic therapy should be suspected of having R. equi bronchopneumonia” Equine practice, vol 14 (1): 15-18, 1992.


Is R. equi zoonotic?

R. equi can infect people undergoing immunosuppression (AIDS, chemotherapy, therapeutically-induced immunosuppression because of organ transplantation).


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Foal, Rhodococcus equi– Texas A&M pyogranulomatous enterocolitis/ lymphadenitis


cecum with R. equi


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Horse, idiopathic broncho-interstitial pneumonia. Note prominent Type II pneumocyte hyperplasia., HE


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Horse, embolic Aspergillus infection (Mycotic pneumonia), Texas A&M, Dr. John Edwards.


embolic- secondary to hematagneous spread


This is an example of embolic pnuemonia

fungal- eosinophilic reaction


Pneumonias of pigs

• Viral Pneumonias:

Porcine reproductive and respiratory syndrome (PRRS): First recognized in Europe in 1987. PRRS is characterized by late-term abortions, stillbirths and respiratory disease in young pigs (interstitial pneumonia).

Swine Influenza: Resulted from adaptation of the type A influenza virus that caused the pandemic of human influenza during World War I. Low mortality unless complicated with secondary bacterial infections. H1N1 influenza pandemic in 2009.

Postweaning multisystemic wasting syndrome (PMWS): Causes progressive emaciation in weaned pigs. The causative agent is PCV-2. May result in interstitial pneumonia.

Porcine Respiratory Coronavirus (PRCV): Sporadic cause of mild bronchointerstitial pneumonia with necrotizing bronchiolitis.


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Interstitial pneumonia, feeder
pig – highly suggestive of viral pneumonia


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Right: Pneumocystosis, Pig, AVC. Foamy eosinophilic proteinaceous material within alveoli. Fungal organisms are detected with Gomori’s methenamine silver stain (GMS). Infections with Pneumocystis carinii are common in pigs with PRRS and PMWS.


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Pig, enzootic pneumonia- Multifactorial disease,
Mycoplasma hyopneumoniae is the main pathogen involved. The organism induces a suppurative or cattarrhal bronchopneumonia with BALT hyperplasia that is quite characteristic. This highly contagious disease of pigs is influenced by immune status and management factors such as crowding, poor ventilation, humidity and temperature fluctuation in the barns. The disease is characterized by low mortality unless complicated with secondary pathogens.


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Porcine Enzootic Pneumonia : Mycoplasma pneumonia (Mycoplasma hyopneumoniae, young piglet, UCVM, O.Illanes. Multifactorial disease.


M. hyopneumonia- looks like salmon

neutrophils in airways


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Mycoplasma pneumonia, young piglet, UCVM, OI. The bronchopneumonia is mild to moderate (low mortality) unless complicated with Pasteurella multocida, Arcanobacterium pyogenes, Bordetella bronchyseptica, Haemophilus spp., Mycoplasma hyorhinis etc.).


hyperplasia of the bronchial tissue


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Young pig

Glasser's disease(Haematophilius parasuis)


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3-month-old pig, fibrinous pleuritis and pneumonia,
may be a component of Glasser’s disease (Haemophilus parasuis) CVM, Western University of Health Sciences, O.Illanes


Porcine Contagious Pleuropneumonia,


Actinobacillus pleuropneumoniae- lesions are in the caudal lung lobes, espesically dorsal surface or the middle lung lobes

Highly contagious often fatal fibrinous bronchopneumonia of pigs 2-5 months of age. Dorsal area of the caudal lung lobes are often affected. Lesions are severe and characterized by hemorrhage, necrosis and thrombosis. Except for the distribution lesions are similar to those of pneumonic mannheimiosis(shipping fever) of cattle.


frothy fluid coming from the nose



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Porcine Contagious Pleuropneumonia,

Actinobacillus pleuropneumoniae


dorsal part of the caudal lung lobe-


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Porcine Contagious Pleuropneumonia,

Actinobacillus pleuropneumoniae,


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Top: Cut surface, contagious

pleuropneumonia, pig


Pneumonias in Dogs

Pneumonias are not as common in dogs as in food- producing animals.

 Infectious pneumonias: Infectious tracheobronchitis (Kennel cough) and canine distemper are the most common.

 Non-infectious: Uremia and paraquat (widely used herbicide) toxicity are most common, renal disease

In addition to distemper, canine adenovirus type 2 (CAV-2), canine herpesvirus 1 (CHV-1) and canine influenza virus can produce pneumonias in dogs.

Bacterial pneumonias are often secondary to distemper virus infection or aspiration of gastric contents (when pulmonary defence mechanisms have been impaired). Pasteurella multocida, Streptococcus spp., E. Coli, Klebsiella pneumoniae and Bordetella bronchiseptica can be involved.


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Broncho-interstitial pneumonia, canine distemper


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Aspiration pneumonia, dog.


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Granulomatous pneumonia, Blastomyces dermatitidis, dog -OVC


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Dog, mycotic pneumonia (granulomatous pneumonia). Left: Blastomycosis,


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Uremic pneumonitis, dog.


stain for mineral or Ca+=


Pneumonias of cats

 Upper respiratory infections: Common

 Pneumonias: Rare

The viruses that produce upper respiratory disease may also induce pneumonia, but unless complicated with secondary bacterial infections they usually do not pose a significant clinical problem.


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Cat- Aelurostronglylus abstrusus


lesions primarily in the caudal lung lobes


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Aelurostrongylus abstrusus


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Snails and slugs are the intermediate hosts. Subpleural nodules contain larvae and eggs, HE.


Aelurostronglylus abstrusus


Pulmonary Neoplasia

In comparison to humans primary pulmonary tumors are rare in animals

 Most are malignant an appear as solitary masses of variable size

 In domestic animals they are most common in dogs and cats.


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Cat, pulmonary adenocarcinoma,- malignant

arises from the bronchial epithelium


Ovine pulmonary carcinoma (pulmonary adenomatosis).

Caused by a transmissible retrovirus. Found around the world but not in New Zealand or Australia. Mainly seen in mature sheep. Slowly progressive signs of respiratory disease ---> death after several months from the initial onset of respiratory signs.


looks grossly like pnuemonia, but not microscopically


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Ovine pulmonary carcinoma (pulmonary adenomatosis).


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Metastatic neoplasms are relatively common. Primary pulmonary neoplasms, largely carcinomas are relatively rare but more common in aged dogs and cats.


In pic on the left- hemanigosarcoma

right- Metastic thyroid gland carcinoma


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Mdx: Melanoma, metastatic


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Hydrothorax, 8-y-old dog, AVC

Chronic liver disease (end-stage liver, cirrhosis).- Etiology




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Hemothorax, dog with ruptured aortic aneurism.


could be result of trauma


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Chylothorax, mink,




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Fibrnous pleuritis, horse.


"shipping fever"; strep. equi subsp. zooepidemicus


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Pyothorax, Pasteurella Multocida, cat


usually ass. with a ruptured pulmonary abysess


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Chronic pleuritis with “sulfur granules”, nocardiosis (Nocardia asteroides), Cat.


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Mesothelioma – In domestic animals seen mainly in cattle – can be congenital. In humans has been associated with inhalation of asbestos (mining, construction, ship building).


Not very common in animals, but when we do see them, they are in cattle


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Fibrinosuppurative pleuropneumonia, rabbit –P. Multocida,

Pasteurellosis is a common disease in domestic rabbits. P.multocida can result in rhinitis (“snuffles”), pneumonia, abscesses, reproductive tract infections, ear infections and septicemia.


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Mycotic airsacculitis – Aspergillus spp.


thickened, with fibrin exudate on the air sacks


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Emu, granulomatous pneumonia – Aspergillus, spp.


Ddx: neoplasia, or mycoplasma