Resumo

Bovine herpesvirus 1 (BoHV-1) is member of the order Herpesvirales, family Herpesviridae, subfamily Alphaherpesvirinae, genus Varicellovirus. BoHV-1 is recognized as one of the most important pathogens of cattle in view of the significant economic losses it may cause to beef and dairy productive chains. BoHV-1 has been mainly associated with respiratory and genital infections and, more significantly, reproductive problems such as embryo losses and abortions. This study was carried out to estimate the seroprevalence of antibodies to BoHV-1 in different cattle management categories in 180 farms with familiar agriculture management systems, distributed in 7 cities from the northwest and southeast regions of the state of Rio Grande do Sul, Brazil. Serum samples (n= 1915) were collected from non vaccinated cattle, including 268 calves (123 animals ≤ 6 months and 145 > 6 months), 142 heifers, 104 pregnant heifers, 1364 cows and 37 bulls. The sera were tested in a 24 hour incubation serum neutralization (SN) in search for antibodies to BoHV-1.1 strain Los Angeles (BoHV-1.1). The overall prevalence of antibodies to BoHV-1 in the samples was 26.7% (512/1915). The antibodies frequencies found in calves were 15.3% (41/268) which 17.9% (22/123) in animals until six months and 13.1% (19/145) in animals more than six months. In addition, the prevalence was 14.8% (21/142) in heifers, 11.5% (12/104) in pregnant heifers, 31.6% (431/1364) in cows and 18.9% (7/37) in bulls. All farms showed at least one antibody-positive animal. The prevalence of BoHV-1 antibodies in calves until six months could be associated with maternal antibodies. There was no significant variation in frequency between pregnant and non pregnant heifers suggesting that a number of different factors (handling, gathering, reproduction) may be involved in the dissemination of the infection in the flocks under study. These findings provide further evidence to substantiate that BoHV-1 antibodies are largely spread in dairy herds and the seroprevalence among distinct cattle categories within flocks may be quite variable.