Feline Infectious Peritonitis

Dr W J Grobler BVSc

  1. Introduction
  2. Pathogenesis
  3. Clinical signs
  4. Diagnosis
  5. Treatment
  6. Epidemiology
  7. Prevention
  8. Links to other articles on FIP
  9. Bibliography


FIP is a slowly progressive fatal disease of domestic and wild cats.  It occurs in two forms a wet form with excess fluid in the body cavities and a dry form with granulomatous lesions (whitish nodules consisting of white blood cells) in the body cavities, abdominal organs, brain and eyes.  It is caused by Feline Coronavirus of which two types exist;  The Feline Enteric Coronavirus (FECV) and the FIP virus.  The latter is thought to be a mutation of FECV, but it is not known whether this mutation occurs inside the body.  FECV causes mild infection of the gastro-inestinal tract.


The symptoms vary considerably and includes the following:


After entering through the nose or mouth the virus multiplies in the tissues of the throat and then spreads to the lining of the gut.  Usually the infection is inapparent, but it sometimes causes mild enteritis and diarrhoea.  The final outcome of the infection depends on the animal's age, immune status, the strain of virus and the route of infection.

If the FIP virus is the culprit, the virus enters the gut macrophages (special white blood cells) and thus escapes detection by antibodies in the cat's blood.  The virus spreads throughout the body leading to classic FIP.  In the wet form variable amounts of a slimy yellow fluid accumulates in the body cavities with small granulomatous lesions (white nodules) on the omentum and abdominal organs as well as inside the lymph nodes, liver and spleen.  In the dry form larger, more fibrotic lesions (lesions with more fibrous tissue) are found in the abdomen as well as in the brain and eyes.

High levels of antibodies do not protect against FIP as the virus hides away in macrophages.  White blood cells geared against FIP could however effect a cure by eradicating the virus from the body.  It is thought that a moderate white blood cell response leads to the dry form while a weak response leads to the wet from of FIP.

Clinical signs

With FECV infection there may be no clinical signs, but sometimes light vomiting and diarrhoea is seen.  In extreme cases severe diarrhoea could ensue from this infection.

With FIP initially the symptoms are non-specific fever,lethargy,depression, inappetance and sometimes diarrhoea.  After a matter of days or even months a fluctuating fever develops with anorexia and weight loss.  In the wet form 75% of animals develop fluid in the abdomen while 25% develop it in the chest.  This leads to swelling of the abdomen in the former and discomfort or difficult breathing in the latter case.  In the later stages jaundice could become apparent.

In the dry form lesions develop on the liver, lymph nodes and less often the kidneys.  Symptoms are related to the involvement of these organs.  Nervous symptoms may occur whenever there are lesions in the nervous system while lesions in the eye are often easily noticable.  There could however be overlapping signs between the two forms.


With FECV infection a rise in antibody titres are found.  The virus could also be demonstrated in faeces with the electron microscope or with DNA testing (PCR).

With FIP infection the definitive diagnosis is microscopic evaluation of the granulomatous lesions.  There are several signs indicative of FIP which include the following:


There is unfortunately no safe treatment at present.  Supportive care is very important, but will only ease the animal's burden.  This comprises fluid therapy or blood transfusions and feeding by stomach tube.  In some instances cortisone or chemotherapy may prolong the cat's life since most of the symptoms are due to damage by the animal's own immune system.  Ribavirin, an antiviral drug has been tried, but the effective dose is very close to its toxic dose, so it is not a viable option.  Interferon strengthens the animal's defenses against the virus, but is quite expensive.


Amongst cats in breeding establishments 75 to 100% of animals may be serologically positive for Coronavirus.  This figure drops to about 25% for ordinary household cats.  Most kittens in catteries will be positive by 10 weeks, but normally they don't show any symptoms.  Most clinical cases occur in cats 6 months to 2 years old, but cats older than 10 years are also at risk.  The disease is usually preceded by some stressful event such as pregnancy, weaning, surgery, moving to a new home or diseases like Feline AIDS and Feline Leukaemia.  Some cats become carriers that shed virus in their faeces for periods of up to ten months.


Buy kittens from smaller catteries, since the disease is usually less common there than in large catteries.  Breeders should group cats into smaller groups and isolate kittens immediately after weaning.  FIP-positive cats should be isolated and all cats vaccinated against Feline Leukaemia.  Queens with a previous history of producing FIP-kittens should not be used for breeding.  Good hygiene is imperative prevent overcrowding and clean cages and sand boxes on a regular basis.

Vaccination is another option.  Reasonable results have been obtained with an intranasal vaccine of which millions of doses have been administered with minimal side effects.  The protection provided by vaccination has unfortunately not been that good and it is uncertain whether kittens younger than sixteen weeks are protected.

  1. Newman Veterinary Medical Services

  2. The Winn Feline Foundation


  1. Gaskell R, Dawson S: FIP-related disease in: Ettinger SJ, Feldman EC eds.: Textbook of Veterinary Internal Medicine, (5th Ed) Philadelphia WB Saunders 2000 p438
  2. Sherding RG: Feline infectious peritonitis in: Birchard SJ, Sherding RG eds.: Saunders Manual of Small Animal Practice (2nd Ed) Philadelphia WB Saunders 2000 p91