Bovine Leukemia Virus: Managing BLV in Cattle Herds

Bovine leukemia virus causes lymphoma and immunosuppression in cattle, with herd management strategies reducing transmission and welfare impact.

Key Facts

BLV is a retrovirus infecting approximately 40% of US dairy cattle and lower percentages of beef cattle
Most BLV-infected cattle remain persistently infected without clinical signs throughout their lives
Approximately 1-5% of infected cattle develop enzootic bovine leukosis (EBL) with lymphoma
BLV transmission occurs through blood transfer: shared needles, rectal sleeves, and ear tags
Subclinical BLV infection causes measurable immune suppression increasing susceptibility to other diseases
No commercial vaccine exists; control relies on reducing iatrogenic transmission and culling positive animals
Some European countries have achieved BLV freedom through testing and culling programs

Welfare Considerations

BLV causes two distinct welfare impacts: the acute suffering of lymphoma in the small proportion developing EBL, and the chronic immune suppression affecting all infected cattle. The latter is difficult to detect but measurable through increased disease susceptibility and reduced response to vaccination. Herd control programs that reduce transmission prevent new infections and reduce the long-term welfare burden. Cattle developing lymphoma suffer significantly - progressive weight loss, enlarged lymph nodes causing organ compression, and eventual systemic failure - and should be euthanized before this stage is reached.

What You Can Do

Use individual needles and clean rectal sleeves for each animal during veterinary procedures
Test purchased cattle for BLV before introduction to BLV-free or low-prevalence herds
Implement separate management for BLV-positive animals to reduce transmission risk
Monitor BLV-positive cows for lymphoma signs: enlarged lymph nodes, weight loss, reproductive failure
Euthanize cattle showing clinical lymphoma signs promptly rather than continuing production
Discuss BLV control strategies with your vet appropriate for your herd's current prevalence
Support BLV eradication programs if they become available in your country or region