Feline infectious peritonitis

What is it?

Feline infectious peritonitis is a serious and often fatal viral disease that affects cats, especially young ones. It results from the mutation of a usually benign feline coronavirus into an aggressive form. It exists in two main forms, wet (with liquid effusion) and dry.

Commonly observed signs

These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.

Causes and risk factors

FIP is caused by a mutation in the feline coronavirus (FCoV), a generally harmless intestinal virus, which becomes capable of infecting immune cells and spreading throughout the body. This mutation only occurs in certain cats infected with the coronavirus.

Kittens and young cats under two years old are most at risk, as are cats living in communities, shelters or breeders. Stress, a weakened immune system and certain genetic predispositions also favor the onset of the disease.

Transmission

The feline coronavirus is mainly transmitted by the fecal-oral route, particularly via litter boxes shared between several cats. FIP itself, resulting from an internal mutation in the cat, is not considered directly contagious from one cat to another.

Diagnosis and care

Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.

Prevention

References

MSD Veterinary Manual

Content reviewed by the TunisieVet editorial team · Updated 18 August 2026