What is Feline Infectious Peritonitis (FIP)?

Feline infectious peritonitis (FIP) is a fatal viral disease caused by a strain of virus called feline coronavirus (FCoV). Many cats carry this worldwide virus. FIP is much more prevalent in multi-cat households, shelters, and breeding colonies. Most cats carry the feline enteric coronavirus (FECV) which, rarely causes disease in itself. When the feline coronavirus mutates into a strain of the virus that has the ability to cause disease it is referred to as the FIP virus. It is fortunate that the mutation only occurs rarely.

How is FIP Transmitted?

The benign, or usually harmless, FECV lives in the cells of the intestinal tract and is shed in cats’ feces. Cats become infected after they ingest the virus when they groom or eat. The mutant feline infectious peritonitis virus (FIPV) that causes the disease is generally not considered to be contagious among cats. The exact cause of the mutation of the virus is not known. It is likely that it mutates for a number of reasons. The FIPV lives inside a type of white blood cell and not in the intestines. So once the virus mutates, it is not shed in cats’ feces.

cat with collar

Two Forms of FIP

Wet (effusive)

The wet form of FIP results in fluid accumulation in body cavities such as the abdomen and chest. It causes abdominal distension and/or difficulty breathing. This fluid is often a yellow color.

Dry (non-effusive)

In the dry form of FIP, inflamed lesions are found throughout the cat’s body, including the eyes, kidneys, liver, and nervous system. Symptoms depend on which organ is most affected by disease.

Signs & Symptoms

There are no symptoms unique to FIP. However, in either form of FIP, cats commonly show vague symptoms such as:

  • Loss of appetite
  • Weight loss
  • Lethargy
  • Fluctuating fever that is not responsive to antibiotics

How Can I Prevent My Cat from Getting FIP?

Preventing your cat from contracting FIP is difficult because there are many factors that contribute to the development of the disease. Research shows that some cats have a genetic predisposition. This causes them to be more susceptible to develop FIP. Therefore, although the FIPV itself is not contagious, multiple cats within the same family may be affected. Selective breeding for disease resistance and stress reduction is beneficial. Please try to keep your cat healthy and visit your veterinarian for regular checkups. Also try to minimize exposure to infectious diseases and by keeping your cat up to date on vaccinations. And, remember to clean your cat’s litter box daily and locate them away from food and water dishes.

Testing for FIP

Currently, there isn’t a test to screen healthy cats for the risk of developing FIP. To diagnose FIP in a sick cat, veterinarians must piece together several diagnostic clues. These include clinical signs and common findings on lab work that correlates with FIP, as well as ruling out other diseases. Analysis of any fluid in the abdomen or chest helps make an accurate diagnosis.

FIP Vaccine

While there is a vaccine to prevent FIP in cats, it is controversial. Also, there is limited evidence to show its effectiveness. Therefore, it is not recommended at this time.


There are no known effective treatments for cats with FIP. You can help keep your cat comfortable and pain-free with supportive care. Currently, several veterinary research groups are working on novel approaches to treat the disease. Hopefully, in the future, a treatment will be available.

Contributed by Dr. Amy Lowe, DVM