Inflammation in avians is characterized by mainly caseous exudate, due to minimal amounts of this enzyme in heterophils.
Myeloperoxidase
What is the most common cause of abomasal impaction?
Poor quality/coarse roughage as the sole feed
(typically used in overwintering beef cows)
Should brain tissue submitted for rabies testing be refrigerated or frozen?
Refrigerated
Which gross hepatic lesions are expected secondary to right heart failure?
- Hepatomegaly
- Rounding of liver margins
- A characteristically “nutmeg liver” appearance on cut section
In small animals, what is the most likely anatomic location (i.e., small or large bowel) of a lesion when diarrhea is characterized by weight loss, large volume of liquid feces, and melena?
Small bowel diarrhea
In contrast, small, frequent, mucus- or blood-streaked stools (hematochezia) with straining indicate large bowel origin
The lesions of pyogranulomatous nephritis that are associated with the non-effusive/”dry” form of feline infectious peritonitis (FIP) are related to which type of hypersensitivity reaction?
Type IV
(delayed-type hypersensitivity)
What is the characteristic brain histologic finding of rabies?
Negri bodies in neurons
However, the gold standard diagnostic is direct fluorescent antibody test on fresh brain tissue.
What is the classic histopathologic triad seen in a liver biopsy of a horse with pyrrolizidine alkaloid toxicosis?
- Hepatocyte megalocytosis
- Biliary duct proliferation
- Bridging portal fibrosis
A horse fed moldy corn over several weeks develops apathy, blindness, circling, and staggering. What disease is most likely, and what is the causative agent?
- Disease: Equine leukoencephalomalacia (liquefactive necrosis of cerebral white matter)
- Cause: Fumonisins produced by Fusarium spp.
What is a pathognomonic gross lesion seen in classical swine fever in pigs?
“Button ulcers” in the gastrointestinal mucosa
(especially in the tonsils and colon)
These ulcers reflect necrosis in lymphoid‑rich tissue caused by the pestivirus’s vasculitis and are characteristic of this disease.
A chicken presents with progressive leg paralysis and enlarged, discolored nerves on necropsy.
What disease is most likely?
Marek’s disease
This causes enlargement of peripheral nerves (e.g., sciatic, brachial) with loss of normal striations and lymphoid infiltration. Herpesvirus‑induced T‑cell lymphomas and nerve enlargement are hallmark features of Marek’s disease.
A growing pig has a shortened, twisted snout with occasional nasal discharge and hemorrhage. What disease is this, and what is the primary cause?
- Disease: Atrophic rhinitis
- Cause: Toxigenic bacteria, primarily Bordetella bronchiseptica and Pasteurella multocida
The bacterial toxins damage nasal turbinates, leading to snout deformities and respiratory signs.
How should a recently deceased animal be stored to preserve tissues for necropsy?
Refrigerate the carcass at 39°F (4°C) and avoid freezing, if possible
Cooling slows tissue decomposition while preventing freeze-thaw artifacts that can preclude diagnostic evaluation.
What is the ideal tissue thickness and tissue-to-formalin ratio for fixation in 10% buffered formalin?
Tissue slices ≤1 cm thick, placed in 10x their volume of formalin
(ensures proper penetration and preservation of tissue architecture for histopathology)
What is the most reliable postmortem test for diagnosing scrapie in sheep?
Immunohistochemistry (IHC) of brain tissue, specifically the medulla oblongata at the obex and cerebellum
How are mesenchymal tumors typically named and classified in veterinary pathology?
Mesenchymal tumor names reflect the tissue of origin and biologic behavior, with “‑oma” indicating benign and “‑sarcoma” indicating malignant
Name three histologic features that are most indicative of malignancy in epithelial tumors.
- Cellular and nuclear atypia (pleomorphism, hyperchromatic nuclei)
- High mitotic activity
- Loss of normal tissue architecture
- Invasiveness
Which organ system is primarily affected by aflatoxin ingestion, and which animals are most susceptible?
Hepatic - in young or immunocompromised animals
(chronic exposure can affect adults, who are usually more resistant)
Aflatoxin causes centrilobular hepatic necrosis and hepatocellular carcinoma.
What organ system shows pathognomonic lesions in cattle ingesting bracken fern?
Hematopoietic system
Bracken fern induces bone marrow suppression, hematuria, and bladder neoplasms.
What histologic artifact can occur if tissue is left at room temperature before fixation?
Autolysis, leading to cell swelling, nuclear fading, and tissue disintegration
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