Cat Infectious Peritonitis: Welfare and New Treatments

Feline infectious peritonitis (FIP) was previously a near-invariably fatal disease, but the development of antiviral treatments has transformed welfare outcomes for affected cats.

Key Facts

FIP is caused by a mutation of feline coronavirus that produces a virulent systemic form of the disease
Wet FIP causes fluid accumulation in the abdomen or chest; dry FIP causes granulomatous lesions in organs
Prior to 2021, FIP was almost universally fatal — supportive care only prolonged suffering for weeks to months
GS-441524 and molnupiravir are antiviral drugs that produce remission in approximately 80-85 percent of treated FIP cats
Treatment requires 12 weeks of daily injections or oral medication; relapse occurs in approximately 10-15 percent of cats
Access and cost remain barriers — treatment can cost £3,000-8,000 for a full course, and GS-441524 is not yet licensed in the UK

Welfare Considerations

FIP caused profound welfare suffering — cats deteriorated over weeks with increasing fluid accumulation, weight loss, lethargy, and eventual death from organ failure. Supportive care extended suffering without altering the outcome. The development of effective antiviral treatment has transformed FIP from a welfare catastrophe to a manageable disease for cats whose owners can access and afford treatment. The primary current welfare challenge is access: the most effective drug (GS-441524) is not yet licensed in the UK and must be sourced through compounding pharmacies or imported, creating legal and cost barriers. Advocacy for licensing and affordability of FIP antivirals is a direct animal welfare priority.

What You Can Do

If your cat is diagnosed with FIP, seek specialist feline medicine consultation about antiviral treatment options urgently
Support advocacy by International Society of Feline Medicine and other bodies for rapid licensing of GS-441524 in the UK and EU
Connect with FIP UK support groups that provide information about treatment access for cats in affected families
Consider pet insurance that covers specialist treatment costs — FIP antiviral treatment is expensive but can achieve remission