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  • Author or Editor: Barbara A. Steficek x
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in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association

Summary:

Eight of 19 calves born to bovine viral diarrhea virus (bvdv)-negative and -immunocompetent dams were determined to be infected with a noncytopathic strain of bvdv. Six of the 8 calves had diarrhea and 2 had no clinical signs of disease. In 3 euthanatized calves, lesions consistent with mucosal disease were found throughout the gastrointestinal tract, and the virus was isolated from the spleen, lymph nodes, and small intestine. In 5 calves, bvdv was isolated from mononuclear cells in blood samples obtained 21 days apart, indicating persistent infection. The virus was not isolated from sera obtained from 2 calves, with chronic nonclinical infections, that had neutralizing antibody titers ≥ 1:512 against bovine viral diarrhea-Singer virus and titers ≥ 1:256 against the persistent bvdv. Twenty-one days after vaccination with a vaccine that contained inactivated noncytopathic and cytopathic biotypes of bvdv, 4 of 5 persistently infected calves had neutralizing antibody titers ≤ 1:4 against the bovine viral diarrhea-Singer virus and their persistent virus. Prior to vaccination, 2 of 11 virus-negative calves had neutralizing antibody titers ≤ 1:128 against the bovine viral diarrhea-Singer virus, and after vaccination, only 1 virus-negative calf had a titer ≤ 1:512. At 149 days after revaccination and prior to weaning, 4 virus-negative calves had neutralizing antibody titers ≤ 1:512 (range, 1:16 to 1:384). Under the specific conditions in this herd, we were not able to detect a beneficial effect of vaccination. Colostral origin bvdv-specific antibody, capable of neutralizing the persistently infective bvdv strain, most likely interfered with isolation of the virus from the sera of 2 persistently infected calves.

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective

To evaluate platelet aggregation responses in calves experimentally infected with a thrombocytopenia-inducing type II bovine viral diarrhea virus (BVDV) isolate (BVDV 890).

Animals

9 neonatal male Holstein calves.

Procedure

5 calves were inoculated with BVDV 890, and 4 were used as controls. Platelet aggregation studies and attempts to isolate BVDV from platelets were performed 2 days before, the day of, and every 2 days for 12 days after inoculation. Platelet function was assessed by means of optical aggregometry, using adenosine diphosphate and platelet-activating factor as agonists. Bovine viral diarrhea virus was isolated from purified platelet preparations by use of an immunoperoxidase monolayer assay.

Results

Maximum percentage aggregation and slope of the aggregation curve decreased over time in calves infected with BVDV. Bovine viral diarrhea virus was not isolated from platelets from control calves, but it was isolated from infected calves from 4 through 12 days after inoculation.

Conclusions and Clinical Relevance

Results suggest that platelet function may be depressed in calves infected with type II BVDV. Although the mechanism for altered platelet function was not determined, it likely involved an increase in the percentage of aged platelets in the circulation, a direct virus-platelet interaction, or an indirect virus-platelet interaction. Platelet dysfunction, in addition to thrombocytopenia, may contribute to the hemorrhagic syndrome associated with acute type II BVDV infection in calves. (Am J Vet Res 1999;60:1396–1401)

Free access
in American Journal of Veterinary Research