FIP in Cats

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FIP in cats

FIP in cats is an abbreviation for “Feline Infectious Peritonitis”. This is a disease caused by mutation of a virus called the feline coronavirus, commonly abbreviated in literature as FCoV.  FIP in cats is fairly uncommon, affecting less than 1% of cats. However, once the virus mutates, it is generally a progressive and ultimately fatal disease.

FIP in cats is most common in cats 6 months to 2 years of age with a slightly higher distribution in male cats. Certain purebred cats also have a higher incidence including Asian breeds such as Himalayan and Birman cats.

Below we will discuss what is FIP in cats, signs of FIP, FIP symptoms, if FIP is contagious, and give you information on the FIP vaccine.

What is FIP in Cats?

FIP in cats is a disease caused by a mutated coronavirus. Feline coronavirus is commonly present in the intestines of cats.  In fact, it is estimated that approximately half of the cats in single cat households have the virus. It is even more common in multi-cat environments e.g. catteries where it is estimated that up to 90% of cats may have coronavirus.

Most cats that have coronavirus live a normal life. However, it is estimated that 5% of cats with coronavirus will go on to develop FIP. In this small percentage of cats, the virus mutates into a pathogenic and harmful virus that causes a variety of problems that we will discuss below under “Signs of FIP in Cats”. This only happens in some cats and the cause is uncertain but is most likely related to the cats’ immune system.

It is important to understand that FIP in cats is NOT transmitted from one cat to another. This can be confusing to some pet owners. The coronavirus CAN be transmitted from cat to cat, but FIP CANNOT be transmitted from one cat to another.

Once a cat has been exposed to coronavirus, 95% will have a normal life. When the coronavirus mutates in the other 5% this is what causes FIP.

What are the Signs of FIP in Cats?

There are two forms of FIP in cats. The first form is called effusive (also known as wet or feline coronavirual polyserositis) FIP and second is called non-effusive (also known as dry or granulomatous) FIP. It is possible for cats to get both forms of the disease.  Signs of FIP in cats generally develop over weeks to months.


The signs of FIP in cats will depend on which form of FIP they acquire.  When the virus mutates, generally one of two things happen. Sometimes the virus affects the blood vessels which is what happens with the “wet” form, or the cat develops granulomatous lesions which is what occurs in the “dry” form of FIP.


With the wet form of FIP, cats develop vasculitis (inflammation of the blood vessels) which causes abnormal fluid accumulations. If the fluid accumulation occurs in the chest (also known as a pleural effusion), common signs are trouble breathing. If the fluid accumulation occurs in the abdomen (commonly referred to as ascites), the abdomen can become distended. The excessive abdominal fluid is uncomfortable and causes signs such as nausea, decreased appetite, lethargy, weight loss, vomiting, and/or diarrhea. Most pet owners don’t notice the distended abdomen but will take their cats to the vet for trouble breathing or the signs that result from abdominal distension.


The dry form of FIP in cats causes granulomatous lesions to various organs including the eyes, skin, and/or nervous system.  A granuloma is a collection of immune cells that form in response to the virus and can be found with many different diseases. The granuloma creates lesions on the skin, in the eye, or nervous system that cause associated signs of FIP. For example, if granuloma forms in the brain, a cat may have trouble walking, be off balance, develop head tremors, and/or seizure just to name a few possibilities.

Many cats with FIP will also have a fever and eventually become anemic (pale).

What are the Symptoms of FIP in Cats?

FIP symptoms in cats may include any or all of the following:

  •   Fever
  •   Lethargy
  •   Depression
  •   Loss of appetite
  •   Weight loss
  •   Vomiting
  •   Diarrhea
  •   Unkempt appearance
  •   Trouble breathing or difficult breathing
  •   Distended abdomen (ascites)
  •   Jaundice (yellow color of the skin, eyes, ears, nose or gums)
  •   Pale gums
  •   Trouble walking or unsteady walking (ataxia)
  •   Seizures or paralysis with nervous system involvement
  •   Eye abnormalities

FIP Symptoms Kittens

FIP symptoms in kittens can be the same as those in adult cats. Some kittens with FIP will appear lethargic and fail to thrive relative to their littermates. They tend to sleep more, play less, appear lethargic, sometimes vomit or not eat, and overall fail to grow like a normal kitten. When the wet form is present, it can be more common to see a profoundly distended abdomen.

Is FIP Contagious?

The question “is FIP contagious” is a common and important one. As mentioned above, the cause of FIP is an abnormal mutation of the coronavirus. Coronavirus is contagious cat to cat, but FIP is NOT contagious cat to cat.


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