Feline Infectious Peritonitis (FIP)

Feline infectious peritonitis (FIP) is a very devastating disease in cats caused by a virus. We have traditionally recognized two forms of the disease: the wet form (with accumulation of massive amounts of fluid in the abdomen or chest) and the dry form (with no fluid accumulation).  Our current understanding is that many cats present with signs that don’t fall neatly into one category or the other, and more typically falls along a spectrum between the two forms.  Cats of any age can be affected, but the disease occurs most often in young cats from six months to five years of age.

What are the signs of feline infectious peritonitis?

At first, the signs of the disease can be hard to distinguish from many other conditions. The cat may have a fever, trouble breathing, runny nose or eyes, diarrhea or weight loss. If the cat has the wet form of the disease, he or she will have abdominal swelling due to fluid accumulation in the abdomen. This swelling, combined with weight loss, makes the cat appear “fat,” but it is very easy to feel the spine and hip bones. If the fluid accumulation is in the chest, then difficulty breathing may be the only sign. Occasionally, there may be changes in the appearance of the eyes (clouding, redness or hemorrhage). Sometimes the disease also affects the nervous system, causing changes in personality or seizures.  In some cats, jaundice, or a yellow tint, to the skin and whites of the eyes may be noted.

How is FIP diagnosed?

Diagnosis by laboratory testing can be difficult since most cats naturally have the corona virus that can lead to the disease. What causes the development of the disease is a mutation of the common coronavirus to a strain that causes serious illness. For this reason, FIP is not considered to be a contagious disease in the traditional sense.

There is a laboratory test that looks for coronavirus, but a positive test merely means that the cat has a coronavirus, not the mutated form of the virus, and so even with a positive test, it is unlikely that the cat will develop FIP disease.  Up to 90% of cats in shelters will test positive for previous exposure to a coronavirus, and we know that the vast majority of cats will never develop FIP disease.

Diagnosis is often made by analysis of the characteristic fluid drawn from the abdomen or chest coupled with the development of the characteristic signs of the disease. In cats with the dry form of the disease, diagnosis can be more difficult.  Diagnostic testing is a key area of current research.

Is there a cure for the disease?

Traditionally, FIP was thought to be uniformly fatal, but treatment is an area of active research and new therapies are promising. Unfortunately, these therapies are not yet commercially available and are prohibitively expensive for most shelters and owners.  These may become more widely available in the future, however.

How can we prevent FIP?

The incidence of clinical disease is low in most cat populations and especially low in single-cat households. The disease prevalence is highest in multi-cat facilities or households.

Stress is a risk factor of the development of the disease, and so shelters can work to prevent FIP by practicing good population management (reducing stress and overcrowding, reducing cats’ time in the shelter), proper sanitation, and monitoring for any signs of illness in individual cats.