Severe acute bovine viral diarrhea in Ontario, 1993-1995.

In 1993, noncytopathic bovine viral diarrhea virus (BVDV) strains with enhanced virulence caused unprecedented outbreaks of severe acute bovine viral diarrhea (BVD) in dairy, beef, and veal herds in Ontario (Canada). Fever, pneumonia, diarrhea, and sudden death occurred in all age groups of cattle. Abortions often occurred in pregnant animals. Gross lesions in the alimentary tract were similar to those associated with mucosal disease, especially in animals >6 months of age. Cattle of all age groups had microscopic lesions in the alimentary tract similar to those seen with mucosal disease. The epidemic peaked in the summer of 1993, with 15% of all bovine accessions from diseased cattle presented to the diagnostic laboratory being associated with BVDV. The virus strains involved in the outbreak were analyzed using monoclonal and polyclonal antibodies and the polymerase chain reaction. The virus isolates from these outbreaks of severe disease were determined to be type 2 BVDV. Type 2 BVDV has been present in Ontario at least since 1981 without causing widespread outbreaks of severe acute BVD, which suggests that type 2 designation in itself does not imply enhanced virulence. Cattle properly vaccinated with type 1 BVDV vaccines appear to be protected from clinical disease.

An evaluation of the API ZYM system as a means of identifying Haemophilus somnus and related taxa.

The commercially available API ZYM microbiological identification system was evaluated for the rapid identification of Haemophilus somnus. Eighty-seven isolates of the organism had API ZYM profiles which were characteristic. The API ZYM profiles demonstrate clear differences between H. somnus and other genera but suggest a close association to three related organisms. Enzyme activity of H. somnus isolates were similar to organisms identified as Histophilus ovis, Haemophilus agni and strains UQV of Actinobacillus actinoides and Actinobacillus seminis but was clearly different from isolates of Pasteurella haemolytica, Pasteurella multocida, Bordetella bronchiseptica and group EF4. The API ZYM system allowed more rapid identification of H. somnus than conventional biochemical tests and may be a useful adjunct to conventional methods used for identification of H. somnus isolates. The test did not reveal obvious differences between isolates from various anatomic locations.

Porcine rabies in a closed feeder barn.

Rabies was diagnosed in a 40 kg pig from a closed feeder barn in which recently unexplained deaths of eight to ten pigs had occurred. A stray cat, probably crawling through a ventilation duct into the barn, was the suspected vector. Over a four and one-quarter year period a disproportionate 53 cases of animal rabies had been diagnosed within a 5 km radius of the farm (13% of the cases in the county in 3% of the county area). Histological lesions, mostly lymphocytic cuffing of blood vessels in the brain with lymphocytic meningitis, patchy to focal gliosis and satellitosis with neuronal necrosis were nonspecific and Negri bodies were rare. Fluorescent antibody technique examination of the brain for rabies virus antigen was positive.

Haemophilus somnus: investigations of its potential role in bovine mastitis.

Mammary glands of 6 lactating Holstein cows were inoculated with Haemophilus somnus strain 43826. Three cows developed chronic mastitis and shed bacteria for up to 1 year. Three cows developed acute gangrenous mastitis, with evidence of bacteremia and endotoxemia. Cows with gangrenous mastitis had lower somatic cell counts early after inoculation in affected quarter secretions compared with those in cows that developed chronic mastitis. Cows with gangrenous mastitis developed hypocalcemia, hypoalbuminemia, azotemia, hyperbilirubinemia, mildly increased serum aspartate aminotransferase and creatine kinase activity, and a marked neutropenia with a degenerative left shift. Histopathologic examination of gangrenous quarters revealed edema, necrosis, and vascular thrombosis with few inflammatory cells. A limited survey failed to recover H somnus from dairy cows with clinical mastitis or from mammary secretions from 41 beef cattle at an abattoir.

Fatal mastitis of dairy cows: a retrospective study.

The necropsy records of dairy cows with mastitis were reviewed from the provincial veterinary laboratory in Guelph (44 cases of mastitis in nine years) and from the Ontario Veterinary College (168 cases in 14 years). Mastitis was considered to be the primary cause of death in 167 of 212 cows (79%). Of these 167 cases of mastitis, Escherichia coli was involved in 107 (64%), Klebsiella sp. in 12 (7%) and Staphylococcus aureus in 11 (7%). Bacteriology was not reported in 22 cases. Coliform mastitis, the most commonly identified type of fatal mastitis, was characterized histologically by the presence of infarcted areas in affected glands and by the lack of demonstrable bacteria, and was thus easily identified from fatal mastitis caused by S. aureus.

A retrospective study of heart disease in doberman pinscher dogs.

The prevalence of gross and/or histological cardiac lesions was found to be much greater in Doberman pinscher dogs (16/26 or 62%) than in non-Doberman dogs (124/417 or 30%). At least some of the affected Dobermans were unrelated. Middle aged (mean age 4.7 yr) Dobermans of both sexes (11 M:5F) were affected. Four of the Dobermans with heart lesions had congestive cardiomyopathy; three of these four had congestive heart failure and the other one died suddenly. Prominent gross lesions were ventricular dilation and atrioventricular valvular endocardiosis. Histological lesions noted were prominent myocardial fibrosis, myofiber degeneration with fatty replacement, myofiber vacuolation and arterial intimal cushion formation. A spectrum of myocardial disease exists in Dobermans and clinically overt congestive cardiomyopathy represents one end of this spectrum.