Feline leukemia virus (FeLV) is a major cause of illness and death in cats, with vaccination and testing programs providing effective prevention for at-risk populations.
FeLV-positive cats face welfare risks from secondary infections and malignancy as disease progresses. However, modern understanding shows that many cats can be regressive FeLV carriers with normal lifespans if well managed. The welfare calculus for FeLV-positive cats includes ensuring access to veterinary monitoring, vaccination against other pathogens, indoor housing to prevent transmission and protect them from additional infections, and quality-of-life assessment as disease progresses. Shelter euthanasia of FeLV-positive cats should be replaced with adoption programs wherever possible.