Bovine herpesvirus type 1 (BoHV-1), is responsible for clinical manifestations such as infectious bovine rhinotracheitis, abortion, conjunctivitis, infectious pustular vulvovaginitis and balanoposthitis. This virus has been responsible for major losses in different productive and reproductive herds in the country. Thus, the objective of this study was to estimate the frequency of antibodies against BoHV-1 in beef heifers not vaccinated in Microregion of Imperatriz, Maranhao, and identify the age group most affected by the virus, as well as a study of factors associated with virus infection and to evaluate the indirect ELISA using the serum neutralization (SN) as a reference standard. The study was conducted in 48 herds, cutting, distributed in 12 counties of Microregion of Imperatriz. The samples were collected from female cattle stratified into three age groups, ≤ 12 months, between 12 and 36 months and ≥ 36 months of age. The samples were subjected to two serological tests, ELISA and SN. In each herd, an epidemiological questionnaire was applied in order to obtain information on management and reproductive sanitary, for the study of risk factors. The frequency of antibodies against BoHV-1 in Microregion of Imperatriz was 63.23%, and the municipalities of Açailândia Buritirana showed the highest frequencies, both with 80.44%, the most affected age group, the Microregion, was animals aged ≥ 36 months (69.65%). Based on the results we can conclude that the frequency of antibodies against BoHV-1 is high, between the age groups most affected were the animals aged ≥ 36 months were considered risk factors for virus transmission, return to estrus (OR=1.874), recovery of animals from other states / region (OR=1.365) and the creation of goat / sheep associated with bovine (OR=1.348), the indirect ELISA technique showed moderate concordance when compared to SN technique, which is the gold standard technique for diagnosis of BoHV-1.
