Feline infectious peritonitis was until recently an invariably fatal disease causing severe suffering in young cats, but the development of antiviral treatments has transformed welfare outcomes for affected cats in the last decade.
FIP causes severe suffering including painful fluid accumulation, progressive neurological deterioration, fever, weight loss and eventual organ failure. Before effective antivirals became available, the only welfare-preserving option after diagnosis was euthanasia. The development of effective treatment has transformed the welfare outlook for affected cats, converting a universally fatal disease into a treatable condition for many individuals. The main ongoing welfare challenge is the cost and duration of treatment, which places effective care beyond reach for many owners. Early diagnosis is critical for best outcomes, as neurological FIP is harder to treat than effusive forms. The availability of treatment creates a welfare obligation to diagnose and treat rather than reflexively euthanise.