Bovine leukemia virus is widespread in cattle populations globally, causing lymphoma and immune compromise. Control programs protect herd welfare and reduce cancer-related suffering.
Bovine leukemia virus creates a welfare burden at two levels: the 5% of infected cattle that develop lymphoma experience progressive suffering from tumor masses, respiratory compromise, digestive obstruction, and a prolonged decline before death, while a much larger population of subclinically infected cattle may experience immune compromise that increases susceptibility to other infections. European eradication programs demonstrate that BLV control is achievable, and the welfare benefits of reduced lymphoma incidence and improved immune function justify the investment in testing and management.