Serological Profile for Major Respiratory Viruses in Unvaccinated Cows from High-Yielding Dairy Herds.

Simple Summary: Bovine Respiratory Disease (BRD) is a major health issue in dairy farming worldwide. It commonly affects lactating and recently weaned calves, but dairy cows can also be impacted resulting in significant losses to the milk production chain. This research aimed to investigate the serological status of dairy cows for the four main bovine respiratory viruses. This study took place in the central-eastern mesoregion of the state of Paraná, which has the highest milk productivity in Brazil. A total of 497 serum samples were assessed from unvaccinated dairy cows from 39 herds. This study aimed to determine the presence of antibodies to bovine alphaherpesvirus 1 (BoAHV1), bovine viral diarrhea virus (BVDV), bovine parainfluenza virus 3 (BPIV3), and bovine respiratory syncytial virus (BRSV) using virus neutralization tests. The frequencies of BoAHV1, BVDV, BPIV3, and BRSV seropositive cows and herds were 71.4, 56.3, 96.8, and 63.4%, and 79.5, 82.0, 100, and 84.6%, respectively. Rates of more than 50% of cows and herds seropositive for the 4 viruses indicate that these respiratory pathogens are endemic in dairy herds in the region evaluated. In this region for BRD prevention, we recommend implementing cow vaccination programs that provide passive immunity in calves and active immunity in cows. This study aims to determine the serological profile of high-yielding dairy cows for four main viruses (bovine alphaherpesvirus 1 (BoAHV1), bovine viral diarrhea virus (BVDV), bovine parainfluenza virus 3 (BPIV3), and bovine respiratory syncytial virus (BRSV)) related to bovine respiratory disease (BRD) in cattle herds worldwide. In this survey, 497 blood serum samples were collected from non-vaccinated dairy cows without clinical respiratory signs in 39 herds in the central-eastern mesoregion of Paraná State, South Brazil. The presence of neutralizing antibodies was determined by virus neutralization (VN) tests. VN antibodies against BoAHV1, BVDV, BPIV3, and BRSV were detected in 355 (71.4%), 280 (56.3%), 481 (96.8%), and 315 (63.4%) serum samples, respectively. The frequencies of seropositive herds for BoAHV1, BVDV, BPIV3, and BRSV were 79.5 (n = 31), 82.0 (n = 32), 100 (n = 39), and 84.6% (n = 33), respectively. The frequencies of seropositive cows varied according to the type of herd management and the number of cows in the herd. The detection of VN antibodies in unvaccinated dairy cattle herds demonstrated the endemic circulation of the four viruses in the herds evaluated. For BRD prevention, it is recommended to implement a vaccination program for cows that provides passive immunity in calves and active immunity in cows. [ABSTRACT FROM AUTHOR]