Bovine leukosis virus is widespread in cattle globally, causing lymphoma and immune dysfunction with welfare consequences that are often underrecognised due to the long incubation period.
BLV-related lymphoma causes significant chronic suffering as tumours grow and impair organ function. Cattle with abomasal lymphoma develop progressive indigestion, weight loss, and abdominal pain. Spinal cord tumours cause progressive paresis and eventual recumbency — an undignified and painful end stage. The insidious nature of BLV means that by the time lymphoma develops, herds may have high seroprevalence with tumours found at slaughter in cattle that appeared clinically normal. For welfare purposes, cattle showing signs of lymphoma should be identified early and humanely euthanased rather than allowed to deteriorate. Eradication through test-and-remove programmes eliminates the virus and prevents future welfare losses.