What is feline infectious peritonitis (FIP)?

Feline infectious peritonitis (FIP) is a disease caused by a coronavirus infection. Many different strains of coronavirus are capable of infecting cats, but most do not produce serious disease. FIP-producing strains are distinguished by their ability to invade and grow in certain white blood cells. The infected cells transport the virus throughout the cat's body. An intense inflammatory reaction occurs in the tissues where these virus-infected cells locate. It is this interaction between the body's own immune system and the virus that is responsible for the disease.

Infected cats shed coronavirus in their saliva and feces. Most cats become infected by inhaling or ingesting the virus, either by direct contact with an infected cat, or by contact with virus-contaminated surfaces like clothing, bedding, feeding bowls, or toys.

What are the signs of FIP?

Initial exposure to the FIP virus usually results in no obvious clinical disease, although some cats may experience a mild upper respiratory disease that is characterized by sneezing, watery eyes, and watery nasal discharge. Some cats may experience a mild intestinal disease. Most cats that undergo the primary infection completely recover, although some of them may become virus carriers. Only a small percentage of exposed cats develop the lethal disease: weeks, months, or perhaps years after primary infection.

The onset of clinical signs of lethal FIP may be sudden (especially in kittens), or the signs may gradually increase in severity over a period of weeks. Many cats have nonspecific signs such as intermittent inappetence, depression, rough hair coat, weight loss, and fever.

The major forms of lethal FIP are effusive (wet) FIP, noneffusive (dry) FIP, and combinations of both. The most characteristic sign of effusive FIP is the accumulation of fluid within the abdomen and/or chest. When fluid accumulation becomes excessive, it may become difficult for the cat to breathe normally.

The onset of noneffusive FIP is usually slower. Fluid accumulation is minimal, although weight loss, depression, anemia, and fever are almost always present. Signs of kidney failure (increased water consumption and urination), liver failure (jaundice), pancreatic disease (vomiting, diarrhea, diabetes), neurologic disease (loss of balance, behavioral changes, paralysis, seizures), enteritis (vomiting, diarrhea), or eye disease (inflammation, blindness) may be seen in various combinations. FIP is often a difficult disease to diagnose because each cat can display different signs that are similar to those of many other diseases.

Should I have an FIP test done on my cat?

There are two primary situations where the determination of coronavirus-antibody titers can be useful to the cat owner or breeder and the veterinarian:

1. As a screening test, to determine the presence or absence of antibodies in a previously untested household and to detect potential virus carriers or shedders when introducing new cats into households or catteries that are negative for coronavirus antibodies

2. As an aid (and nothing more than an aid) in the clinical diagnosis of a diseased cat that has signs suggestive of FIP.

3.