Search Results

You are looking at 1 - 3 of 3 items for

  • Author or Editor: David J. Bezek x
  • Refine by Access: All Content x
Clear All Modify Search

Summary

A total of 21 calves were inoculated IV with 1 of the following isolates of bovine viral diarrhea virus (BVDV); CD87 (n = 10), NY-1 (n = 3), NADL (n = 5), or were sham-inoculated with virus-free medium (n = 3). Subsequent to inoculation, platelet counts were monitored to detect differences between noncytopathic (CD87, NY-1) and cytopathic (NADL) isolates in their ability to induce thrombocytopenia. Platelet count decrease throughout infection was statistically analyzed by comparing the slope of the line drawn from the count on the day of infection to the lowest count achieved by that calf. Significant difference was observed in the CD87-inoculated calves and in the NY-1-inoculated calves, compared with those of the same control group. Significant difference was not observed in the slope of platelet count decrease between the cytopathic NADL-infected calves and control-group calves. The data indicate that noncytopathic BVDV isolates may more easily induce thrombocytopenia than do cytopathic isolates in immune-naive, immunocompetent calves; acute infection with 1 cytopathic BVDV isolate (NADL) did not induce thrombocytopenia. In addition, although each calf seroconverted, virus was rarely isolated from mononuclear cells obtained from calves with cytopathic infections. At some point after infection, virus was always isolated from each of the calves undergoing noncytopathic infections, and occasionally, transient association of noncytopathic BVDV antigen with platelets was observed during these infections.

Free access
in American Journal of Veterinary Research

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

Summary

The relationship between bovine viral diarrhea virus (bvdv) infection and thrombocytopenia was studied in 18 veal calves experimentally infected with bvdv. All calves were free of bvdv, and 13 calves were free of serum neutralizing antibodies to bvdv before virus inoculation. Calves were inoculated at approximately 10 days of age, and platelet counts were monitored over a period of several weeks. Ten additional calves housed in close proximity were kept as uninoculated controls. A profound decrease in platelet counts by 3 to 11 days after inoculation was seen in all calves that had neutralizing antibody titers < 1:32 before infection. Severe thrombocytopenia (<5,000 platelets/μl) was seen in 12 calves, 11 of which also developed hemorrhages. Necropsy findings in 3 severely thrombocytopenic calves that died included multiple hemorrhages throughout the body. Calves that recovered had increased platelet counts, and in most instances, a corresponding increase in neutralizing antibody titers to bvdv. At 11 days after inoculation, bvdv was detected on platelets by use of immunofluorescence, but evidence of surface-bound immunoglobulin was not found. The results suggest that a nonimmunoglobulin-mediated method of platelet destruction or sequestration develops as a sequela to bvdv infection.

Free access
in Journal of the American Veterinary Medical Association