Anais do Congresso Paranaense de Microbiologia
IV Congress of Microbiology in Paraná

Reproduction has an important role in the efficiency and profitability of the breeding phase of bovine production; however, the increase of production intensification can predispose to occurrence of infectious diseases that can impair reproductive performance. The viral etiological agents frequently associated with reproductive disorders in bovine are alphaherpesvirus 1 (BoHV-1) and bovine viral diarrhea virus (BVDV). This study aimed to verify the occurrence of antibodies against BoHV-1 and BVDV in cows with reproductive problems from a dairy cattle herd from São Paulo State, Brazil. Thirty-three serum samples were collected from Girolando cows of different ages with milk production average 15 liters/cow/day that presented reproductive disorders from an open dairy cattle herd located in the city of Gália, São Paulo State, Brazil. This research was approved by the Ethics Committee on the Use of Animals in Teaching and Research of the Universidade Estadual de Londrina (UEL), Londrina, Brazil, under number 1835.2019.45. The blood serum samples were submitted to virus neutralization (VN) test to verify the presence of antibodies against BoHV-1 and BVDV. The serum samples were inactivated at 56°C for 30 minutes and the VN test was performed in Madin-Darby Bovine Kidney (MDBK) cells and 100 tissue culture infective doses of 50% (TCID50) of the cell culture adapted BoHV-1 (Los Angeles strain) and BVDV-1a (Singer strain), according the Manual of Diagnostic Tests and Vaccines for Terrestrial Animals. The neutralizing antibodies titer was considered the reciprocal of the highest serum dilution capable of neutralizing viral replication. Serum samples with neutralizing activity at a final dilution ≥1:2 for BoHV-1 and ≥1:8 for BVDV were considered positive. Of the 33 serum samples analyzed, 32 (96.97%) were seropositive for BoHV-1 in the VN test with antibody titers ranging from 4 to ≥128. The serology results show that 23/32 (71.875%) had high (64 or ≥128) antibody titers, 8/32 (25%) had intermediate (16 or 32) antibody titers, and 1/32 (3.125%) had low (4) antibody titers. Regarding BVDV, of the 33 serum samples evaluated, 24 (72.73%) were seropositive in the VN test with titers ranging from 64 to ≥512, being that all positive serum samples had high (64 to ≥512) antibody titers. We conclude that the open dairy cattle herd evaluated had seropositive animals, both for BoHV-1 and for BVDV with high antibody titers, indicating viral circulation in the dairy cattle herd.