Feline infectious peritonitis (FIP)
Also known as FIP.
A disease that appears when feline coronavirus, which is very common and harmless in the gut, mutates inside the cat. It used to be almost always fatal; today antivirals cure most cats.
Persistent fever in a young cat, a swollen belly or difficulty breathing: see the vet that same day.
- System
- Infectious diseases
- Is it urgent?
- Not usually
- Spreads to other cats
- Very rarely
- Spreads to people
- No
- Typical cost in Spain
- Diagnosis, €200–600; full treatment, €500–5,000 depending on the cat and the legal route available.
The underlying coronavirus is contagious, but FIP itself almost never passes from one cat to another. It does not affect people.
Symptoms
- Fever that does not respond to antibiotics
- Swollen belly from fluid (wet form)
- Difficulty breathing if there is fluid in the chest
- Weight loss and listlessness
- Cloudy eyes or changes in eye colour
- Wobbling or seizures (neurological form)
Causes
A mutation of feline enteric coronavirus inside each individual cat. It is more common in young cats, cats from breeders or shelters, and after stressful situations.
How it is diagnosed
There is no single test: blood tests, fluid analysis, ultrasound and PCR or immunocytochemistry are combined.
Treatment
Antivirals such as GS-441524 or remdesivir for about twelve weeks, always directed by the vet and obtained through legal channels.
No doses, on purpose: any medicine must be prescribed by your vet for your cat.
Prognosis
With antivirals, around 80 % or more of the cats treated in studies are cured. Without treatment, mortality is almost total.
Prevention
Fewer cats per space, plenty of clean litter trays and less stress. No useful vaccine is available in Spain.
Breeds at higher risk
It is described more often in these breeds. That does not mean all of their cats will have it, nor that a moggy is free of it.
Frequently asked questions
Is feline infectious peritonitis (FIP) contagious?
To other cats: very rarely. To people: no. The underlying coronavirus is contagious, but FIP itself almost never passes from one cat to another. It does not affect people.
Can feline infectious peritonitis (FIP) be cured?
With antivirals, around 80 % or more of the cats treated in studies are cured. Without treatment, mortality is almost total. Antivirals such as GS-441524 or remdesivir for about twelve weeks, always directed by the vet and obtained through legal channels.
How much does it cost to treat feline infectious peritonitis (FIP)?
As a guide for Spain in 2026: Diagnosis, €200–600; full treatment, €500–5,000 depending on the cat and the legal route available. Prices vary a lot between clinics and cities, and out-of-hours emergencies cost more.
Which breeds are most at risk?
It is described more often in Bengal, Sacred Birman, Ragdoll, British Shorthair, Abyssinian and Devon Rex. That does not mean every cat of those breeds will have it, nor that a moggy is free of it.
More in infectious diseases
Educational content from Michipedia. It does not replace diagnosis or treatment by a vet: if you have any doubt about your cat's health, ask. Costs are a guide for Spain in 2026.