Cat Feline Leukemia Virus: Prevention, Testing, and Welfare Management

Feline leukemia virus (FeLV) is a retrovirus causing cancer and immune suppression in cats. Vaccination, testing, and appropriate management of FeLV-positive cats significantly improves outcomes and welfare.

Key Facts

FeLV is the most common cause of cancer in cats and causes significant immune suppression
Approximately 2-3% of cats in the US are FeLV-positive, with higher rates in multi-cat households
The virus is transmitted primarily through saliva from social behaviors including mutual grooming and shared bowls
Vaccination is highly effective - FeLV vaccine is recommended for all cats with outdoor or multi-cat exposure
Testing before introducing new cats to a household prevents transmission to resident negative cats
A proportion of exposed cats develop regressive infection and clear the virus without developing disease
Progressive infection leads to lymphoma, anemia, and immunosuppression with shortened lifespan
FeLV-positive cats can live comfortably for years with appropriate management and supportive care

Welfare Considerations

FeLV welfare management involves both preventing transmission and providing appropriate care for FeLV-positive cats. Undiagnosed FeLV in multi-cat households creates ongoing transmission risk to negative cats. Testing allows informed management decisions - FeLV-positive cats should live separately from negative cats. FeLV-positive cats in shelters historically faced automatic euthanasia, but growing evidence supports that FeLV-positive cats can have good quality of life for years with appropriate care. Dedicated FeLV-positive adoption programs have demonstrated that these cats can be successfully adopted into FeLV-appropriate households. The welfare of FeLV-positive cats improves dramatically with stress reduction, high-quality nutrition, and regular veterinary monitoring for secondary infections.

What You Can Do

Vaccinate all cats with outdoor or multi-cat exposure against FeLV beginning in kittenhood
Test all new cats for FeLV before introducing them to resident cats
House FeLV-positive and negative cats separately to prevent transmission
Consider adopting FeLV-positive cats who need homes and can live as single or FeLV-only cats
Monitor FeLV-positive cats closely for lymph node changes and early cancer signs
Support shelters that maintain FeLV-positive adoption programs rather than automatic euthanasia