Seroprevalence of bovine herpesvirus types 1 and/or 5 in the state of Rio Grande do Sul

Holz C. L., Cibulski S. P., Teixeira T. F., Batista H. B. C. R., Campos F. S., Silva J.R., Varela A. P. M., Cenci A., Franco A. C. & Roehe P. M. 2009. [Seroprevalence of bovine herpesvirus types 1 and/or 5 in the state of Rio Grande do Sul.] Soroprevalencia de herpesvirus bovinos tipos 1 e/ou 5 no Estado do Rio Grande do Sul. Pesquisa Veterinaria Brasileira 29(9): 767-773. Instituto de Pesquisas Veterinarias Desiderio Finamor, Fepagro Sa de Animal, Estrada do Conde 6000, Cx. Postal 47, Eldorado do Sul, RS 92990-000, Brazil. E-mail: proehe@gmail.com This study was carried out to estimate the prevalence of antibodies to bovine herpesviruses types 1(BoHV-1) and 5 (BoHV-5) in the state of Rio Grande do Sul (RS), Brazil, by testing serum samples against different BoHV-1 and BoHV-5 strains. The sera examined were obtained from a larger sample designed to estimate the prevalence of bovine brucellosis within the state. All sera were collected from cows 24 months or older, not vaccinated to bovine herpesviruses, from both dairy and beef herds. The number of samples to be tested was calculated based on an estimated prevalence of infection of 33%, with an average standard deviation of <= 1% and a 95% limit of agreement. Sera from 2.200 cattle from 390 farms distributed in 158 counties were tested by serum neutralization (SN) tests in search for antibodies to the following strains: BoHV-1.1 (strains EVI123/98 and Los Angeles), BoHV-5a (strain EVI88/95) and BoHV-5b (strain A663). The overall seroprevalence to BoHV-1 and BoHV-5 in the sampled herds was 29.2% (642/2.200); seropositive animals were detected in 225 (57.7%) of the sampled farms. Prevalence estimates varied according to the virus used for challenge in SN tests. The highest prevalence and sensitivity were attained when positive SN results against the four different strains were added together. The use of only one virus for challenge in SN tests would lead to a loss in sensitivity from 20.4% to 34.6% when compared to the combined SN-positive results. These findings provide evidence that antibodies to BoHV-1 and BoHV-5 are largely spread in dairy and beef herds in RS, although prevalence in distinct geographic regions is quite variable. The results were strongly affected by the virus strains used for challenge in SN testing. This must be taken into account when performing serologic tests to detect BoHV-1 and BoHV-5 antibodies. As SN test is not capable of discriminating between antibody responses to BoHV-1 and BoHV-5, type-specific prevalence remains unknown.