CAHFS Connection - March 2025

Avian

Pharyngoesophageal squamous cell carcinoma caused sudden death by asphyxia in a backyard rooster. Grossly, there was an approximately 6 cm x 5 cm x 4 cm mass arising from the mucosa of the pharynx and cranial esophagus, and compressing the laryngeal opening. The comb was cyanotic. Microscopically, the mass consisted of infiltrative cords and islands of neoplastic keratinocytes. Oral squamous cell carcinomas are relatively common in backyard chickens and can arise from the epithelial lining of the oral cavity, pharynx, esophagus or larynx. They may infiltrate the adjacent tissues and/or compress and occlude the glottis, as in this case.

 Pigeon paramyxovirus type-1 (PPMV-1) infection was diagnosed in adult squab-type pigeons. The birds, which had been vaccinated against PPMV-1 with a killed autogenous injectable vaccine, originally presented for elevated mortality and later developed torticollis. Post mortem exams revealed mottled livers, kidneys and pancreas, swollen kidneys, splenomegaly and splenic hemorrhage. Histologically, there was multifocal necrosis, hemorrhage, and inflammation in the spleen, liver, pancreas and kidneys. The diagnosis was confirmed by PCR on oropharyngeal and cloacal swabs. PPMV-1 is believed to be the result of chicken-to-pigeon transmission of Newcastle disease virus that has developed increased virulence in pigeons and decreased virulence in chickens.  Pneumonia by Aspergillus fumigatus was also observed in some pigeons.

Bovine

Locoism was the cause of clinical signs in a 10-month-old Angus heifer that presented with a stiff gait and slight head tremor. Histology revealed microvacuolation of neurons, including Purkinje cells, glial cells, and renal tubule epithelium typical of locoweed intoxication. Lesions are reversible if caught early and cattle are removed from pastures with locoweed. 

A mast cell tumor was diagnosed in a skin biopsy from a 6-year-old Angus cow that had multiple raised proliferative and ulcerated cutaneous nodules ranging from 1 cm to 7.5 cm over the body for the past month.  Many bovine mast cell tumors appear to be associated with multicentric cutaneous and/or visceral disease and may be malignant and metastatic.

Equine

A four-year-old Irish sport horse suffered a comminuted fracture of the pelvis associated with a fall during training. The horse went down and was unable to rise, so euthanasia was elected for humane reasons. Catastrophic pelvic fractures are relatively common in horses; they can occur as a consequence of trauma and are usually predisposed by stress fractures. 

Halicephalobus gingivalis was the cause of osteomyelitis in an 11-year-old Warmblood gelding with an osteolytic mass involving the mandible bilaterally. Histologic changes in the bone revealed profiles of rhabditiform nematodes consistent with H. gingivalis, within granulomatous bone inflammation. Infection by this parasite may cause facial swelling, uveitis, lameness, orchitis, renal disease, posthitis, and various CNS disorders.

Pigs

Escherichia coli septicemia was the cause of death of two, 10-day-old piglets in a group experiencing 30% mortality. Clinical signs included ataxia and seizures. Gross and microscopic examination revealed fibrinosuppurative polyserositis with intralesional gram-negative bacilli. E. coli was isolated in pure culture from the lung, liver, and brain of both piglets. Antimicrobial susceptibility testing showed the isolates were resistant to multiple antibiotics.

Small Ruminant

Actinobacillosis was diagnosed in a 10-year-old crossbred ewe with subcutaneous, lymph node and lung abscesses. Postmortem examination revealed multiple, white to yellow, raised, firm nodules measuring 2 -6 cm in diameter in the subcutaneous tissue of the face, the lung and submandibular, retropharyngeal, and mediastinal lymph nodes. Pyogranulomatous inflammation with Splendore-Hoeppli material was seen microscopically, and Actinobacillus sp. was isolated from subcutis, lymph node and lung. Trauma to the oral mucosa—often due to the ingestion of rough plants or forages, or abrasions from teeth—is considered the primary route of entry of this bacterial infection. 

Grayanotoxins were detected in a 7-month-old Nubian goat with a history of lack of energy, decreased appetite, drooling, regurgitation of food, no rumen contractions, and “splashy” rumen with intermittent fluid sounds of 24 hours duration. The animal was from a dairy goat farm and was on a pasture that contained numerous acorns, but no other potential toxicants. Due to the persistent regurgitation, exposure to a grayanotoxin-containing plant was considered. Both grayanotoxin I and III were detected in a fecal sample submitted, thus confirming exposure. Grayanotoxins are found in rhododendrons, azaleas, mountain laurel, and andromedas. The toxins affect voltage-dependent sodium channels and intoxication is often associated with cardiac arrhythmias and heart block. A source plant was not identified.