Feline Infectious Peritonitis (FIPV)

What is Feline Infectious Peritonitis (FIP)?

Feline Infectious Peritonitis (FIP) is a fatal viral disease caused by a strain of virus called Feline Coronavirus (FCoV). Many cats carry this worldwide virus. FIP is much more prevalent in multi-cat households, shelters, and breeding colonies. Most cats carry the Feline Enteric Coronavirus (FECV) which, rarely causes disease in itself. When the feline Coronavirus mutates into a strain of the virus that has the ability to cause disease it is referred to as the FIP virus. It is fortunate that the mutation only occurs rarely.


Feline Infectious Peritonitis (FIP) is a progressive and often fatal disease that is caused by a Coronavirus. In most cases, a Coronavirus causes mild, treatable symptoms (respiratory and/or gastroenteritis) in cats. In rare cases, the Coronavirus may mutate to a more virulent form which is able to weaken the cat’s immune system and spread throughout the body by way of the white blood cells, often resulting in death. Kittens and cats under the age of 3 are at greatest risk for FIP. As cats mature and their immune systems strengthen, their risk is reduced.

Kittens and young cats are at highest risk for infection. Cats with weakened immune systems, such as those infected with Feline Leukemia (FELV) or Feline Immunodeficiency Virus (FIV) are also at risk. Cats in multiple-cat households and catteries are also at a higher risk. Not all cats exposed to FIP will develop the disease; the majority of cats exposed to it will not get sick. FIP is thought to spread through feces; the virus can stay active for a long period of time, until surfaces are thoroughly disinfected.

Two Forms of FIP

There are two forms of FIP.

An acute form, often referred to as “wet” FIP and a chronic form, known as “dry” FIP.

The acute or “wet” form comes on suddenly, and its most common sign is a buildup of fluid in the abdomen and chest cavity, causing difficulty in breathing and, in some cases, a swollen abdomen. With the chronic or “dry” form, there is no fluid buildup; instead, lesions develop on the organs, often resulting in neurological symptoms such as seizures or paralysis. Liver and kidney

  • Wet (effusive): The wet form of FIP results in fluid accumulation in body cavities such as the abdomen and chest. It causes abdominal distension and/or difficulty breathing. This fluid is often a yellow color.
  • Dry (non-effusive): In the dry form of FIP, inflamed lesions are found throughout the cat’s body, including the eyes, kidneys, liver, and nervous system. Symptoms depend on which organ is most affected by disease.
Are certain cat breeds more susceptible to FIP?

Certain breeds of cats may be more likely to develop FIP. Those breeds include the Abyssinian, Bengal, Birman, Himalayan, Ragdoll, and Devon Rex. FIP may be more common in cats that live in multi-cat households, shelters, or catteries. Cats that are stressed due to re-homing, have recently had surgery, or have concurrent infections (more than one infection at a time) may also be more susceptible to developing FIP. Genetic factors are also thought to contribute to the development of FIP

What is Feline Infectious Peritonitis (FIP)How does a cat become infected with feline Coronavirus?

Most cats become infected with feline Coronavirus through the fecal-oral route (oral contact with infected feces). It is estimated that about one-third of these cats shed the virus in their feces. Most cats only shed the virus for a few months, but a small percentage will shed the virus continuously for life. Although the virus is quite fragile and does not survive for more than 24-36 hours in the normal environment, it is believed that cold temperatures may preserve the virus for months. Transmission on clothing or other objects is only likely within a few hours of contact.

"Cold temperatures may preserve the virus for months."

As explained above, most infections are with relatively harmless strains of feline Coronavirus. Unfortunately, this initial benign infection may later mutate to cause FIP in some cats. Even with the more harmful strains, apparently healthy cats may be carriers of the virus, and may shed the virus without ever showing signs of disease. Many cats that develop FIP have no history of contact with other cats showing clinical signs of FIP. The virus can remain dormant or inactive in the body for months to years before the cat eventually develops disease.

What age is a cat most at risk for developing FIP?

It is believed that most cats are exposed to feline Coronavirus at a very young age, perhaps during the first few weeks of life. Most cats that develop FIP are between the age of 3 months and 2 years of age, although any age cat can develop the disease.

Signs & Symptoms

There are no symptoms unique to FIP. However, in either form of FIP, cats commonly show vague symptoms such as:

  • Loss of appetite
  • Weight loss
  • Lethargy
  • Fluctuating fever that is not responsive to antibiotics
What clinical signs does a cat infected with FIP develop?

In cats that develop FIP disease, the first signs of illness may be very vague. Listlessness, lethargy, decreased or absent appetite, weight loss, and a fluctuating fever are commonly reported clinical signs. After a period of several days to a few weeks other symptoms typically begin to occur.

At this stage, most cats will develop the 'wet' or effusive form of FIP, which refers to the accumulation of fluid in body cavities; fluid may accumulate in the abdomen, leading to a swollen abdomen, or in the chest cavity, resulting in difficulty with breathing.

Some cats develop 'dry' or non-effusive FIP where little to no fluid accumulates. The dry form often involves severe inflammation in one or more organs including the eyes, brain, liver, intestine, or other organs of the body, leading to a variety of clinical signs. Many cats with non-effusive FIP will have ocular (eye) symptoms as their only clinical sign.

Once disease develops, most individuals deteriorate rapidly, although some cats remain normal for several weeks. Unfortunately, the disease will eventually result in death in almost every case.

Most cats exposed to feline Coronavirus, even to the potentially FIP-inducing strains, are able to develop an immune response that protects them, therefore only a small proportion of infected cats actually develop clinical disease. However, as stated above, those that do develop the disease almost invariably die.

How Can I Prevent My Cat from Getting FIP?

  • Prevention of FIP is difficult because there are many factors that contribute to the development of the disease.
  • Research shows that some cats have a genetic predisposition. This causes them to be more susceptible to develop FIP. Therefore, although the FIPV itself is not contagious, multiple cats within the same family may be affected.
  • Selective breeding for disease resistance and stress reduction is beneficial.
  • Keep your cat healthy and visit your veterinarian for regular check-ups
  • Minimize exposure to infectious diseases and keep your cat up to date on vaccinations.
  • Clean your cat’s litter box daily and locate them away from food and water dishes.


  • Currently, there isn’t a test to screen healthy cats for the risk of developing FIP.
  • To diagnose FIP in a sick cat, veterinarians must piece together several diagnostic clues. These include clinical signs and common findings on lab work that correlate with FIP, as well as ruling out other diseases. Analysis of any fluid in the abdomen or chest helps make an accurate diagnosis.
fip diagnosticHow can FIP be diagnosed?

Many of the clinical signs of FIP are vague and occur with other diseases found in cats, making FIP particularly difficult to diagnose. There may be abnormalities in a routine blood analysis, but none is specific for FIP. X-rays may be helpful to determine the presence of fluid in the abdomen or chest. If fluid is present, some of it can be removed by tapping the chest or the abdomen. Analysis of this fluid at a veterinary laboratory can be particularly valuable, as few other diseases produce the same type of fluid that FIP creates. Nevertheless, fluid analysis does not always provide a definitive diagnosis of the disease. Sometimes FIP is a diagnosis of exclusion, meaning that a variety of similar conditions have been ruled out. The diagnosis may be further complicated because FIP may exist at the same time as some other conditions such as Feline Leukemia Virus diseases. See the handout “Feline Infectious Peritonitis Testing” for further information on diagnosing FIP.

"Your veterinarian may advise that a biopsy be taken from your cat, so that FIP can be distinguished from a treatable disease."

Currently the only way to make a positive diagnosis of FIP is by histological examination of affected tissue (or by post-mortem examination) by a pathologist at a laboratory. If there is any doubt about the diagnosis, your veterinarian may advise that a biopsy be taken from your cat, so that FIP can be distinguished from a treatable disease.

I understand there are specific blood tests. How reliable are these?

Veterinary laboratories provide tests that detect antibodies to feline Coronavirus in the blood, but these tests are non-specific and cannot be used alone to diagnose FIP. Some laboratories provide tests such as polymerase-chain reaction (PCR) tests, which can detect very small amounts of the virus, but no unique genetic sequence associated with FIP has been identified. Although some of these tests claim to be able to distinguish between the strains, and to detect strains more likely to be associated with FIP, many independent experts disagree with these claims. Therefore, a positive test in a healthy cat is not a strong predictor of subsequent FIP disease.

"If a cat has clinical signs consistent with a diagnosis of FIP, then a positive test is supportive of the diagnosis, but not conclusive."

If a cat has clinical signs consistent with a diagnosis of FIP then a positive test is supportive of the diagnosis, but not conclusive. Likewise, a negative test in the presence of advanced signs does not rule out the diagnosis of FIP.

As you can see, FIP is one of the most challenging diagnoses for your veterinarian to make because of the complexity of the disease and the limitations of current tests.


There are no known effective treatments for cats with FIP. You can help keep your cat comfortable and pain free with supportive care. Currently, several veterinary research groups are working on novel approaches to treat the disease. Hopefully, in the future a treatment will be available.

Is there any treatment for FIP?

FIP is fatal in almost all cases. Supportive treatments may extend longevity and improve quality of life, however, there is no specific cure. Anti-inflammatory drugs such as corticosteroids (e.g., prednisolone) in combination with certain drugs that suppress the immune system (e.g., cyclophosphamide), may temporarily reduce inflammation and improve the cat's quality of life. An experimental drug, polyprenyl immunostimulant (PI), is currently being investigated for use in the dry form of FIP. For the clinically ill cat, once FIP has been diagnosed, euthanasia may be the most humane and appropriate course of action.

Vaccination for FIP?

While there is a vaccine to prevent FIP in cats, it is controversial. Also, there is limited evidence to show its effectiveness. Therefore, it is not recommended at this time.

Is there a vaccine for FIP?

In recent years, some manufacturers have developed vaccines to help in the prevention of FIP. Because the method of transmission and the sequence of events leading to clinical FIP disease are poorly understood, and because infection may have occurred before vaccination, the success of vaccination is not certain. Currently the vaccines for FIP are not recommended for general use. You and your veterinarian can discuss whether vaccination is appropriate for your cat.

Are other cats in the household at risk?

If your cat has FIP, other cats in your household may be at a greater risk for becoming infected with feline Coronavirus. Fortunately, infection will lead to this fatal disease in a minority of cats. As a precaution, many veterinarians recommend that you wait about a month after an infected cat dies before introducing a new cat into the house, to minimize the chance of exposure to the virus. In a multi-cat household in which an infected cat has died, it is recommended to wait at least three months to see if any other cats develop clinical disease. However, these previously exposed cats could be carriers of the disease and could potentially infect any new cats.

"Infection will lead to this fatal disease in only a few cats."

Cleaning with dilute bleach (1:32) is adequate to kill the virus. Keeping adequate numbers of litter boxes can also help minimize exposure to other cats’ feces.

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