Signs and Symptoms of FIP

Primary FIP Infection

Most cats initially are asymptomatic, but the virus is at work. After ingestion, the virus immediately begins to replicate in the cat's pharynx and small intestine. From there it moves into the throat, lungs, stomach, and large intestines. About 1 to 10 days later, it can be spread to other cats.

During this time, cats may display the symptoms of a mild upper respiratory infection: sneezing, watery eyes, and nasal discharge. Others give the appearance of having intestinal problems: diarrhea, weight loss, and lethargy. Many cats have nonspecific symptoms: intermittent loss of appetite, depression, rough hair coat, weight loss, and fever. Most cats that undergo the primary infection recover fully, although some may become virus carriers.

A small percentage of exposed cats develop lethal FIP weeks, months, and even years after primary infection. In some cats, especially kittens, the onset of symptoms may be sudden. In others, FIP symptoms may appear and increase in severity over a period of weeks. When the classic symptoms of full-blown FIP appear, the disease typically is diagnosed as wet (effusive) or dry (noneffusive), and many cats present symptoms of both.

When the FIP infection reaches the lymph nodes, it spreads throughout the cat's body. The disease is no longer contagious at this stage.

Effusive (Wet) FIP

The hallmark of lethal effusive FIP is the accumulation of fluid inside the abdomen and/or chest cavity. Some animals take on a "pot-bellied" appearance. Excessive fluid buildup compresses the lungs and backs up into the airways, making it difficult for the cat to breathe. The lining of the affected cavity, along with the liver and spleen, becomes coated with white, fibrinous matter. Some lymph nodes may be enlarged.

Other signs of wet FIP include the following:

  • Gastrointestinal and eye ulcers
  • Jaundice (yellowing of the eyes)
  • Mild anemia
  • Neurological abnormalities
  • Severe conjunctivitis

Noneffusive (Dry) FIP

Noneffusive FIP usually develops slowly, with little fluid accumulation. Weight loss, depression, anemia, and fever are common. In young cats, growth may be stunted. Other symptoms depend on the organs affected and include the following:
  • Increased water consumption and urination (kidneys)
  • Jaundice (liver)
  • Vomiting and/or diarrhea (pancreas)
  • Ocular inflammation, conjunctivitis, and blindness (eyes)
  • Brain inflammation, paralysis in the hind legs, weakness, shaking, vertigo, seizures, and personality changes (central nervous system)

The affected organs often develop a characteristic pyogranulomatous inflammation, in which the diseased tissue becomes thickened with an accumulation of white blood cells. The only definitive way to diagnose this form of FIP is by postmortem biopsy of the lesions.

Publication Review By: the Editorial Staff at

Published: 01 Oct 2001

Last Modified: 16 Dec 2014