FIP was once a universally fatal disease in cats but new antiviral treatments have transformed outcomes and quality of life for affected cats.
The transformation of FIP from universally fatal to largely treatable represents one of the most dramatic welfare improvements in feline medicine in recent decades. Before antiviral treatment availability, FIP caused profound suffering through fluid accumulation causing breathing difficulty and abdominal discomfort, progressive neurological deterioration, and the psychological distress of a dying young cat in obvious decline. Euthanasia was the only welfare-positive option in most cases. The development and validation of nucleoside analogue antivirals has changed this completely: cats that previously would have died within weeks now achieve complete clinical remission and return to normal life. The welfare burden of treatment itself is significant since daily injections or pills for 12 weeks in a sick cat require owner commitment and cause handling stress, but this temporary burden is justified by the transformation from death sentence to treatable disease.