FeLV is a retrovirus causing immunosuppression and cancer in cats, with outdoor and multi-cat household exposures creating welfare risks that vaccination and testing can substantially reduce.
FeLV welfare impacts are substantial and prolonged: infected cats experience progressive immunosuppression, frequent secondary infections, and eventual tumor development. The chronic nature of the disease requires sustained management attention over years. Prevention through testing, vaccination, and keeping cats indoors or testing before introducing new cats is far more welfare-positive than treating established infection. FeLV-positive cats can still have good quality of life for extended periods with attentive veterinary care, but proactive prevention eliminates years of potential chronic disease burden.