Biosecurity practices associated with bovine viral diarrhea virus infection in dairy herds in Brazil

This study determined the association between biosecurity practices and the status of bovine viral diarrhea virus (BVDV) in dairy production systems. Approximately 280 herds were screened for BVDV virus detection. Following the screening, 68 herds were selected to identify individual BVDV PI animals using an ear notch biopsy and ELISA-antigen. All offspring of the last generation were tested, and the maternal lineage of positive cases was examined. A questionnaire on BVDV biological risk assessment was completed. A multiple correspondence analysis (MCA) was conducted to determine the association between herds with or without BVDV circulation and biosecurity practices. The MCA revealed that farms with virus circulation lacked knowledge about the disease and wrongly perceived their herds as protected, while farms without virus circulation were aware of the disease but considered their herds unprotected. Vaccination practices differed between positive and negative herds, with positive herds using vaccines only for reproductive diseases and negative herds vaccinating for respiratory and reproductive issues. Biosecurity practices such as frequent visitation, contact between animals of different ages, and annual introduction of new animals were linked to viral circulation, while virus-free herds implemented measures like controlled visitation, no contact between different age groups, and quarantine. Lastly, herds with virus circulation acquired pregnant females without prior testing. This study emphasized the crucial role of biosecurity practices in controlling BVDV in dairy herds. It highlighted the sharper risk perception and better application of biosecurity practices in negative herds compared to BVDV-positive herds.