Detection of bovine viral diarrhea virus in semen obtained after inoculation of seronegative postpubertal bulls.

OBJECTIVE: To evaluate persistence of bovine viral diarrhea virus (BVDV) in semen after inoculation of postpubertal bulls. ANIMALS: Three 2-year-old bulls and five 6-month-old calves. PROCEDURE: 3 seronegative 2-year-old bulls were inoculated intranasally with BVDV. Serum and semen samples were obtained at regular intervals until 7 months after inoculation. Serum samples were tested for BVDV by use of virus isolation (VI) and reverse transcription-nested polymerase chain reaction (RT-nPCR) tests. Semen samples were tested for virus by use of VI and RT-nPCR tests. Testicular biopsy specimens were obtained 7 months after inoculation and tested for BVDV by use of immunohistochemical analysis and VI and RT-nPCR tests. Semen samples collected from 1 bull immediately before and 5 and 7 months after inoculation were administered IV to seronegative calves, which were monitored for subsequent viremia and seroconversion.
RESULTS: Use of VI and RT-nPCR tests detected transient virus in serum of all bulls. The VI test detected BVDV in semen of 2 bulls for < 21 days after inoculation, whereas RT-nPCR assay detected BVDV until 7 months after inoculation. Virus was detected in testicular biopsy specimens of these 2 bulls by use of immunohistochemical analysis and RT-nPCR assay but could only be isolated from the biopsy specimen of 1 bull. Of the calves administered semen IV to detect infectious virus, only the recipient of semen collected 5 months after inoculation of the adult bull was viremic and seroconverted. CONCLUSIONS AND CLINICAL RELEVANCE: Bovine viral diarrhea virus can persist in semen of acutely infected bulls for several months after exposure.