Bovine viral diarrhea virus causes significant welfare harm and is the most economically important viral pathogen in cattle. Understanding PI animals and control enables welfare improvement.
BVDV causes welfare harm at multiple levels: acute respiratory disease in naive cattle, reproductive failure reducing fertility, immune suppression predisposing to secondary infections, and the fatal, painful mucosal disease in PI cattle that causes severe oral ulcers and hemorrhagic diarrhea. The welfare case for PI animal identification and removal is clear: PI cattle will inevitably develop fatal mucosal disease, and allowing them to progress to this terminal disease state when removal was possible represents avoidable welfare harm. BVDV control through PI testing also removes the major herd source of immunosuppression that enables other diseases to cause additional welfare harm.