CAHFS Connection - January 2025

Avian

Avian pulmonary proteinosis was diagnosed in a 17-month-old chicken with a two-day history of lethargy and anorexia prior to death. The lungs were wet and mottled pale to dark pink on gross examination. On histology, there were large deposits of material in air spaces, consistent with surfactant. Avian pulmonary proteinosis has been sporadically reported in birds, including chickens, and is caused by abnormal accumulation of surfactant in the lungs. In some cases, this is an incidental finding, but in severe cases such as this one, it can lead to respiratory failure and death.

Pseudomonas aeruginosa septicemia was diagnosed in eight, 16-day-old quail chicks presented with a history of poor viability after hatching, bloody noses, sneezing, and lethargy in the last two hatches. 

On necropsy, the livers and spleens were enlarged and mottled red to brown. Microscopically, there was splenic and hepatic necrosis. These changes are compatible with septicemia. P. aeruginosa was isolated from the livers in pure culture. This microorganism grows well in warm, humid climates and in this case, it is believed that the incubators were contaminated.

Bovine

H5N1 Avian influenza (AI) virus has been recently diagnosed as the cause of a marked uptick in abortions and stillbirths on several dairies. On necropsy, fetuses had pale-streaked hearts, dark red lungs with prominent interlobular septa, and enlarged livers. Microscopic lesions included myocardial necrosis, mineralization, and lymphocytic inflammation. The lungs and livers had vasculitis. A few fetuses had lymphocytic meningoencephalitis. H5N1 AI virus was detected by PCR on lung swabs. Affected tissues were positive for Influenza A on immunohistochemistry.

Leptospira interrogans serovar pomona was the cause of stillbirth in a crossbred beef calf from a herd of 100 pastured cattle where four stillbirths and three deaths occurred shortly after birth. Field necropsy revealed marked, diffuse icterus, swollen kidneys, pale liver, and enlarged spleen. 

Histology revealed mild suppurative nephritis. The L. pomona titer in the dam was >1:3200 while the other 4 serovars were negative at 1:100. The herd had not been vaccinated against leptospirosis. PCR, immunohistochemistry, and silver stains failed to detect the organism; Leptospira organisms can be multifocal in tissues and missed on sampling, which supports the value of serology on dam sera on abortion submissions. 

Equine

Epiploic foramen entrapment and strangulation of the large colon were diagnosed in a five-year-old Thoroughbred mare with a 24-hour history of colic that was euthanized after failing to respond to medical treatment. At necropsy, approximately three meters of small intestine, including the distal jejunum and proximal ileum, were incarcerated (from left to right) through the epiploic foramen. The incarcerated segment of intestine was very congested, hemorrhagic and edematous. In addition, the anterior part of the jejunum was wrapped around the sternal and diaphragmatic flexures of the large colon producing a constriction and obstruction of this organ.

Actinobacillus equuli ssp. equuli neonatal septicemia was the cause of death of a one-day-old, male, miniature donkey that was lethargic since birth. At necropsy, the lungs were non collapsed and histologically there was multifocal hemorrhage and necrosis with intralesional bacteria in many organs. A. equuli ssp. equuli was isolated from liver, lung, and spleen, and there were no IgG in serum, which is consistent with failure of passive transfer.  A. equuli ssp. equuli is part of the normal microbiota of the gastrointestinal and reproductive systems. Fetal/neonatal infection can occur in uterus, during parturition or through the umbilicus or small wounds. Poor colostrum intake/failure of passive transfer is the main predisposing factor. 

Pigs

Colonic sand impaction and mesocolon twist resulted in the death of an eight-month-old Duroc barrow. The hog was wheezing, teeth grinding, and vomiting in the 36 hours prior to death. Necropsy revealed a 360^o twist of the mesocolon and the entire spiral colon was bright to dark red, gas distended with fibrin over the serosa, and had dark red-brown content. Distal to the twist, a 32 cm segment of colon was impacted with dry gray sand and there was focal pressure necrosis of the wall. The twist was most likely secondary to the sand impaction.

Valvular endocarditis of the right atrioventricular valve was diagnosed in a three-month-old Yorkshire pig that died after a four-day period of lethargy, anorexia and pale mucous membranes. Fresh heart was submitted for examination and testing, and multifocal to coalescing, gritty-to-soft, cauliflower-like yellow-to-green masses were observed in the right atrioventricular valve. Dense fibrinosuppurative inflammation admixed with large colonies of cocci were observed histologically, and Streptococcus suis and Escherichia coli were isolated.

Small Ruminant

Acute bacterial bronchopneumonia was the cause of death of a juvenile Nubian goat that was found in the morning without observed prior signs of illness. Grossly, there was pulmonary cranioventral consolidation with fibrin over the pleura. Histologically, there was severe acute suppurative inflammation with “oat cells” and bacterial colonies. Streptococcus sp., Klebsiella aerogenes, and Escherichia coli were recovered from the lung. No Mycoplasma spp. was isolated. The presence of “oat cells” suggests that other bacteria, in particular members of the family Pasteurellaceae, such as Mannheimia haemolytica, may have played a role. In this case, the poor postmortem condition of the carcass could have hindered the bacteriology results.

Wildlife

Rabies was diagnosed in a grey fox that was found dead. On necropsy, this animal had punctures of the skin and underlying musculature in the thorax, fractured ribs, hemothorax, and pulmonary hemorrhage. These changes were considered to be compatible with predation. Microscopically, there was lymphoplasmacytic encephalitis with intracytoplasmic inclusion bodies characteristic of rabies. Rabies was confirmed by immunofluorescence. 

Tularemia was diagnosed in an immature female California ground squirrel which was exhibiting severe distress before being euthanized. Necropsy and histologic examination revealed disseminated necrotic foci in lung, liver, spleen and lymph nodes, and multiple hydatid cysts in the liver. Francisella tularensis was detected by PCR on tissue samples. Immunohistochemistry for this microorganism was also positive. The hydatid cysts in liver were considered incidental.