BVD and Cattle Welfare
Bovine Viral Diarrhoea (BVD) causes a complex spectrum of disease with profound welfare implications, from subclinical immunosuppression increasing susceptibility to other diseases, to the severe suffering of Mucosal Disease in persistently infected (PI) animals. BVD eradication programmes deliver significant welfare as well as economic benefits.
Persistently Infected Animals
The most welfare-significant aspect of BVD is the persistently infected (PI) animal. When a cow is infected with BVD during early pregnancy (before 120 days), the foetus may not recognise the virus as foreign and becomes persistently infected — shedding virus continuously throughout its life and unable to mount an immune response against BVD.
PI animals are at high risk of developing Mucosal Disease — a fatal condition causing severe oral and gastrointestinal ulceration, profuse diarrhoea, fever, and progressive decline. There is no treatment. PI calves that develop Mucosal Disease experience significant suffering before death, and humane euthanasia is the only welfare option when disease develops. Identifying and removing PI animals from herds is therefore both an epidemiological and a welfare priority.
Subclinical BVD Welfare Impact
Beyond PI animals, BVD causes widespread subclinical welfare impact through immunosuppression. BVD infection (even transient) suppresses immune function, making cattle more susceptible to BRD, salmonella, and other infections. Herds with circulating BVD experience higher disease rates, increased antibiotic use, and reduced welfare outcomes across the population — even when clinical BVD disease is not obvious.
BVD Eradication — Welfare Benefits
National BVD eradication programmes (Scotland has achieved very low prevalence; England, Wales, and Ireland are implementing programmes) reduce PI animal prevalence, cut disease burden across herds, and reduce antibiotic use. The welfare return from BVD eradication — fewer PI animals suffering Mucosal Disease, reduced immune suppression, lower disease rates — is substantial. Testing cattle for BVD status (PI testing of youngstock, antibody testing of batches) and vaccinating breeding cattle are cornerstones of eradication.