Feline Infectious Peritonitis (FIP) in Plain Language

Wacky Blacky died of FIP. Photo by Tim Pearce, Los Gatos. This post is in his memory.
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FIP is caused by a virus. A virus is the sort of organism that gives us the common cold. The virus that causes FIP is a coronavirus – feline enteric coronavirus (FeCV).

In infected cats the virus is found in:

  • feces
  • urine
  • saliva

FIP is spread from cat to cat but requires prolonged exposure to become infected.

How Common?

30-40% of all cats have been exposed to it and have antibodies in their blood. Antibodies are produced in response to the presence of the virus. 80-90% of cats in catteries have antibodies to FeCV. It is widespread, therefore. It is a problem for catteries². It is hard to get rid of it in an infected cattery. In fact FIP is a danger in any multicat environment.

However, 99% of cats do not develop the secondary fatal disease that we call FIP. 75% of exposed cats have no symptoms and some have mild symptoms such as a runny nose and eye discharge.

Less than one percent of infected cats develop the FIP.

Age of Cats

Most cats are 6 months to 5 years old¹ (2 years²) when they develop the disease. Also older cats are ‘often infected’¹.


These may occur from weeks to years after exposure. They usually show after 2-3 weeks. There are 2 forms: wet and dry FIP.

In wet, fluid builds in the chest or abdomen. This is due to damage to very small blood vessels causing them to leak fluid into body spaces and tissues. This makes breathing difficult if there is fluid in the chest cavity. You might see a bloated abdomen if the fluid is in the abdomen. The fluid is clear and light yellow in color (egg white consistency¹). Other signs are:

  • fever
  • anemia
  • diarrhea
  • vomiting
  • dehydration

In dry, there are abnormalities in the cells (lesions) of a granular pus filled nature. This form of FIP is ‘disseminated’² – spread out and dispersed. The early signs are as for the wet type. Eyes can be affected. 60% of cases show brain and eye problems.

FIP can cause renal failure, liver disease and nervous system defects.


“He will die”². “A very small percentage of cats survive FIP”¹ Excellent nursing skills are required.


As at 2008 there is a vaccine that is not part of the routine schedule and at that time its effectiveness was not established.

Associated Pages

Respected References:

  1. Medical, Genetic & Behavioral Aspects of Purebred Cats edited by Ross Clark DVM ISBN 0-9634124-0-X
  2. Cat Owner’s Home Veterinary Handbook 3rd edition by Eldredge, Carlson, Carlson (DVMs) and Giffin MD. ISBN 978-0-470-09530-0

6 thoughts on “Feline Infectious Peritonitis (FIP) in Plain Language”

  1. We lost 2 cats to FIP in 1983. We didn’t know anything about it until one of our cats took sick and he died within a week. It was misdiagnosed. Then, several months later the second cat showed symptoms. Correct diagnosis this time but nothing could be done. She died in my arms on a weekend, sooner than expected, when no vet was available to euthanize her . Horrible disease. I heard about the vaccine but didn’t realize its effectiveness still hadn’t been established. It seems to me that effective prevention, treatment, and cure is LONG overdue. There certainly should be enough money in it for the pharmaceutical industry.


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