Bovine Viral Diarrhea Virus causes reproductive failure, immunosuppression, and mucosal disease. Eradication through PI animal identification is the most welfare-positive strategy.
BVD causes welfare harm at multiple levels across the herd. Acutely infected animals experience fever, immune suppression, and reduced productivity. The immunosuppressive effect — sometimes called the 'BVD effect' — predisposes acutely infected animals to secondary diseases including bovine respiratory disease, which compounds welfare burden.
PI animals suffer the most severe welfare consequences. Born immunotolerant to the virus, they shed BVD continuously but may appear relatively healthy until mucosal disease develops. Mucosal disease — occurring when PI animals are superinfected with a related BVD strain — causes severe gastroenteritis with bloody diarrhea, oral ulceration, and is invariably fatal within days to weeks. The suffering of mucosal disease is significant and represents an entirely preventable welfare harm.
National eradication programs demonstrate that BVD can be eliminated through systematic testing and PI removal. Scotland's compulsory program has dramatically reduced BVD prevalence, improving herd welfare at population scale. Participating in voluntary or compulsory eradication programs is the highest-welfare action available to cattle producers.