CAHFS Connection August 2024

CAHFS Davis is offering the following new assays:

Avian metapneumovirus ELISA (serotype A, B or C) on chicken and turkey sera. This test for antibodies does not distinguish between the different serotypes, but detects exposure to any of the three serotypes.

Avian metapneumovirus rt PCR type A. This assay is still under validation but has performed well on flocks exhibiting clinical signs. Preferred samples to submit are sinus swabs followed by oropharyngeal or tracheal swabs in VTM or BHI. Alternatively, the swabs can be kept moist with a few drops of sterile saline. Care should be taken not to over dilute the sample in the transport media. Pooling of up to five swabs is acceptable.

Avian

Erysipelothrix rhusiopathiae septicemia resulted in increased mortality in a flock of 52 and 65-week-old layer hens. Some affected birds had cloudy air sacs, fibrin on the liver and enlarged spleens. Microscopically, there was coelomitis, airsacculitis, pericarditis, splenitis, and hepatitis. E. rhusiopathiae was isolated from liver, air sac, and spleen. 

Quail bronchitis adenovirus infection was the cause of increased mortality in a group of eight-month-old quail. Affected birds presented with upper respiratory signs, congestion, lethargy and decreased feed intake of five days duration prior to death. Gross exam revealed increased mucus in the trachea and nasal cavity, and red, wet lungs. Histology revealed tracheitis, bronchitis, parabronchitis and airsacculitis with intranuclear viral inclusions typical of an adenovirus infection. Fowl adenovirus PCR was positive on trachea and lung. A good read on sequencing of the virus was not achievable, but readable segments were compatible with fowl adenovirus group A, the cause of quail bronchitis.

Bovine

Histophilus somni systemic infection was the cause of death of a ten-month-old, Angus heifer from a group of 300, that was found recumbent and died shortly after antibiotic treatments began. Significant gross lesions included fibrinous polyarthritis, meningitis and a grey focal discoloration (infarct) in the papillary muscle of the left ventricle. Histologic examination revealed severe thrombosing arteritis in the meninges, heart and synovium with bacterial colonies in the thrombi. Histophilus somni was isolated from the cerebral spinal fluid in pure culture.

Salmonella group D1 (likely S. Dublin) septicemia was diagnosed in tissues submitted from three Holstein calves less than two months old from a calf ranch. Two of the three calves had disseminated inflammation in the lung, liver, spleen and kidney accompanied by a fibrinonecrotic enterocolitis. Salmonella group D1 was isolated from organs and intestine confirming septicemic salmonellosis.

Equine

Verminous meningoencephalitis was diagnosed in a euthanized 15-year-old Appaloosa stallion with a history of acute onset of neurologic signs (including difficulty rising and nystagmus). Grossly, no remarkable abnormalities were appreciated. Histologically, in the brain there was granulomatous inflammation associated with cross and tangential sections of nematodes. Microscopically, the nematodes exhibited features consistent with Halicephalobus spp., a free-living opportunistic nematode. The parasites can be found in decaying organic matter, soil, water, and manure; transmission typically occurs via wounds in the skin or mucous membranes.

Bacillary hemoglobinuria was diagnosed in a ten-year-old Thoroughbred stallion euthanized after a four-day history of high fever and extreme pain unresponsive to treatment. The animal had mild icterus, abundant cloudy brown peritoneal fluid, fibrinous peritonitis, and perihepatitis involving the left liver lobe. The latter was swollen and had multiple large necrotic foci surrounded by a dark red halo. Histologically, there was massive coagulation necrosis with numerous intralesional gram-positive bacterial rods. Clostridium novyi I type D (formerly Clostridium haemolyticum) was isolated in large numbers from the liver, and Clostridium novyi was detected in the same organ by immunohistochemistry.

Small Ruminants

Copper deficiency was the cause of death of a two-month-old Boer goat kid submitted after a two-week history of progressive neurologic decline, including inability to ambulate. Three kids were affected and two kids had died in a herd of 25 goats housed on pasture with mineral block access.  The major histological findings included central chromatolysis throughout the spinal cord and segmental demyelination of the peripheral nerves. Liver copper concentration at 0.68ppm (normal 25-150ppm) was extremely deficient. Sera from the 3 affected kids had no detectable copper and two adults had 0.5ppm and 0.16ppm (normal 0.8-1.5ppm), confirming copper deficiency. Copper is essential for neural function, and deficiency in young goats and lambs can result in weakness, incoordination and paralysis.

Attaching and effacing E. coli (AEEC) and Cryptosporidium spp. were the cause of diarrhea in two one-week-old Boer goat kids from a herd in which 30% of kids were affected and seven had died. Necropsy of two kids revealed semifluid yellow intestinal content and histopathology identified large numbers of adhered coccobacilli in the small intestine. Cryptosporidium ELISA was positive in the small and large intestine in both animals.