Bovine Herpesvirus-4, A Potential Cause of Mastitis in Canadian Dairy Cows

Bovine herpesvirus-4 (BHV-4), genus Rhadinovirus, is a member of the family Herpesviridae, subfamily Gammaherpesvirinae with a worldwide distribution. This study was conducted to investigate the role of the virus in mastitis and/or subclinical mastitis in the Canadian dairy herds.Milk samples from 176 dairy cows were divided into 2 main groups; “A” contained samples with no bacterial isolates, and “B” containing samples either with Staphylococcus aureus or Streptococcus uberisisolates. Approximatelyninety-eight percentages of milk samples had antibodies against BHV-4. Among cows with negative bacterial milk cultures, significantly higher titres of BHV-4 antibodies were associated with samples which had high Somatic Cell Counts (SCC), compared to low SCC samples. Viral DNA was detected in 2% of milks samples by the PCR amplification of BHV-4 glycoprotein-B gene. To our knowledge, this is the first report of the presence of BHV-4 in milk of Canadian dairy herds. Further investigation is needed to determine whether BHV-4 is one of primary causative agents in bovine mastitis, or whether the observed correlation of high titres of specific milk BHV-4 antibody with high SCC was due to reactivation of latent BHV-4 infections by primary bacterial insults.