Investigation of an outbreak of infectious pustular balanoposthitis in cattle breeding bulls at a frozen semen bank.

Abstract

Infectious pustular balanoposthitis (IPB) is one of the reproductive disorders caused by bovine herpesvirus 1 (BoHV1) that can be transmitted through artificial insemination. A herd of 63 breeding bulls at a frozen semen bank in Odisha state in India experienced a suspected outbreak of IPB, with 11 bulls showing clinical signs of the infection. Clinical signs were noticed in two bulls initially and a few days after in the other nine animals. Serum samples from 53 bulls were examined for anti-BoHV1 antibodies using a virus neutralisation test (VNT) and a competitive enzyme-linked immunosorbent assay (cELISA); the remaining ten bulls were not included in the study because it was difficult to restrain them at that time. Paired serum samples were collected 21 days apart from ten clinically affected bulls (the eleventh clinically affected bull was not included in the study for the reason stated above). In the neutralisation test, the paired serum samples showed a two- to fourfold increase in anti-BoHV1 antibody titre; in the cELISA, the paired samples were also found positive for anti-BoHV1 antibodies. Serum samples from 43 in-contact bulls were collected about day 22 after the first observation of clinical infection in the herd. Among these serum samples, a total of 30 were found positive for anti-BoHV1 antibodies in the VNT and a total of 30 were found positive in cELISA. Ten samples were positive in one test but not the other and 25 tested positive in both tests. In all, 35 serum samples from in-contact bulls tested positive in either one or both of the two types of test. An overall agreement of 76.74% was found in detection of anti-BoHV1 antibodies in the two tests. Sensitivity was higher than specificity in detection of anti-BoHV1 antibodies in the serum samples. The glycoprotein C region of the genomic DNA of BoHV1 was amplified from semen samples by polymerase chain reaction. The findings from the outbreak indicate that continuous monitoring of breeding bulls at frozen semen banks is warranted to avoid the risks associated with artificial insemination.