Cat Feline Infectious Peritonitis: Welfare Revolution

Feline infectious peritonitis was once universally fatal. The development of antiviral treatments has transformed FIP from a death sentence to a manageable disease.

Key Facts

FIP is caused by a mutated form of feline coronavirus that becomes pathogenic in some cats
The wet (effusive) form causes fluid accumulation in the chest or abdomen; dry form causes granulomas in organs
Without treatment, FIP was invariably fatal — typically within days to weeks of diagnosis
GS-441524 (an antiviral nucleoside analog) and molnupiravir achieve remission rates over 80% with 12-week treatment courses
Treatment costs are significant — £2,000-5,000 for a full course — but cats achieve full clinical remission
Relapse occurs in a minority of cases and typically responds to extended treatment

Welfare Considerations

The welfare significance of antiviral FIP treatment cannot be overstated. Before GS-441524 became available, FIP diagnosis was equivalent to a death sentence — cats deteriorated rapidly with significant suffering from fluid accumulation, systemic inflammation, and neurological involvement. Treatment now offers most cats a return to completely normal life. The welfare challenge is access — treatment costs remain prohibitive for some owners, and geographic availability varies. Supporting access to antiviral treatment for FIP-diagnosed cats is one of the most impactful individual interventions available in companion animal welfare.

What You Can Do

Ask your vet about GS-441524 or licensed antiviral alternatives immediately if FIP is diagnosed
Seek diagnosis confirmation (coronavirus titres, effusion analysis, PCR) before beginning expensive treatment
Explore FIP treatment assistance programs and online communities connecting owners with affordable supply access
Support research into FIP vaccine development and more accessible treatment formulations