Feline leukemia virus (FeLV) is a retrovirus that suppresses the immune system and causes cancer in cats. Vaccination, testing, and responsible management dramatically reduce its welfare impact.
FeLV-positive cats experience a progressive decline in immune function that leaves them vulnerable to opportunistic infections, cancers, and anemia. The suffering associated with secondary infections and lymphoma can be profound, making prevention through vaccination and testing a major welfare priority. Responsible management of FeLV-positive cats in multi-cat households requires strict separation from uninfected animals to prevent transmission. Supportive care including prompt treatment of infections, nutritional support, and regular veterinary monitoring can extend quality of life significantly. The emotional impact on owners and the welfare cost to infected animals make FeLV prevention one of the most cost-effective welfare interventions available to cat owners.