FeLV remains one of the most significant infectious diseases in outdoor cats. Vaccination, testing and welfare-positive management of positive cats can dramatically improve outcomes.
FeLV causes a progressive reduction in immune function that leaves infected cats increasingly vulnerable to opportunistic infections and tumours. The welfare trajectory for progressively infected cats involves recurrent illness episodes of increasing severity and duration. The welfare priority for FeLV-positive cats is preventing secondary infections through careful management, prompt treatment of any illness and stress reduction to support remaining immune function. Vaccination of uninfected cats in multi-cat households is the most important welfare intervention, preventing the spread that leads to additional welfare suffering. Cats with FeLV should not be euthanised at diagnosis but managed proactively to maintain quality of life for as long as it can be sustained.