FIP or Feline Infectious Peritonitis

Two Persian kittens on a bed

© Pelaqita Persians

Feline Infectious Peritonitis commonly referred to as "FIP" is -

  • a disease that is infectious but not contagious;
  • has a 100% death rate;
  • has no real diagnostic test to confirm FIP; and
  • there is no effective treatment.

What is FIP?

The virus which causes FIP is "feline coronavirus" (FCoV). Feline coronavirus is very common among cats living in multicat households, catteries, rescues and shelters (basically, anywhere that 5 or more cats are housed together). Most strains of feline coronavirus do not cause the actual disease and are referred to as "feline enteric coronavirus".  (Analogy: humans carrying or being exposed to the virus which causes cold-sores, but not every one develops an actual cold sore.)

Cats infected with feline coronavirus, initially do not show any symptoms and antiviral antibodies develop during this time. In a small percentage of cats (1 in 300 of the ENTIRE cat population), a mutation of the virus occurs and infection progresses into clinical FIP which is then referred to as "feline infectious peritonitis virus" (FIPV). White blood cells which are supposed to protect the cat carry the virus throughout the cat's body. Once a cat develops clinical FIP involving one or many systems of the cat's body (abdomen, kidney, brain), the disease is progressive and is always fatal.

There are two forms of FIP: the wet (effusive) form and the dry (non-effusive) form. The wet form is characterized by an accumulation of fluid in the chest or abdomen. The dry form of FIP is characterized by inflammatory sores that can be found in almost any organ of the body, including the nervous system. In both the wet and dry forms of the illness, the cat will experience loss of appetite, weight loss, lethargy, and a fluctuating fever that is not responsive to antibiotics.

Most often FIP occurs in cats between 3 and 16 months of age.

..."to produce FIP, it takes not only the mutant virus, but a cat predisposed to mount an ineffective and inappropriate immune response to the virus – the "right" virus and the "right" cat. This is why FIP is uncommon, though infection with FCoV is widespread among cats." (Winn Feline Foundation, Feline Infectious Peritonitis, 2015.

Feline coronavirus is different from other feline viruses in a few distinct ways:

  • Antibody titers from a blood sample are meaningless for the diagnosis or prognosis of FIP;
  • Detection of feline coronavirus is also not diagnostic;
  • There currently is no ACCURATE test for FIP; and
  • The ONLY way to positively diagnose FIP is a necropsy (an autopsy on a deceased animal) and even a necropsy does not always result in a diagnosis (the results may be inconclusive).


  • Infectious   refers to the disease being communicable by infection from one part of the body to another.
  • Contagious   means capable of being transmitted by contact with an infected animal or object.
  • FIP   is the medical term for the clinical disease associated with the mutated form of feline coronavirus. FIP is infectious but not contagious.
  • FECV   ("feline enteric infection") is the common benign form of the feline coronavirus.  (The term "enteric" refers to an infection of the intestines).
  • FIPV   ("feline infectious peritonitis virus") is the term used when FECV has mutated into the disease-causing form.
  • FCoV   ("feline coronavirus") in general, is called "coronavirus".

Is FIP Contagious?

No.  According to research, FIP is not passed from cat to cat. While all cats (as well as other animals and humans) may have feline coronavirus in their system that does not mean it mutates into clinical FIP. It is estimated by veterinary research professionals like, Dr. Janet Foley and Dr. Niels Pedersen of the University of California at Davis Veterinary School, that more than 90% of cats with FECV remain healthy. However, in a very small number of cases, the benign form of the coronavirus mutates which is the first step in a chain of events leading to FIP.

Most veterinarian health research experts believe FIP is not contagious. These leading researchers believe cats that are ill with FIP are not a risk to other cats and thus do not need to be isolated from other cats. However, personally, I would always err on the side of caution and isolate (quarantine) a new cat and always practice good animal husbandry (see recommendations below).

How Can an Infectious Disease Not be Contagious?

FIP is a REACTION to infection with the mutated feline enteric coronavirus (FECV). Most cats who become infected with FECV essentially get the flu and never develop anything more serious. FECV mutates into FIP in less than 1 in 300 cats. The mutated virus is not contagious to other cats.

When a Cat Dies From FIP, What is the Infection Risk to the Other Feline Housemates?

The other feline housemates likely already have the coronavirus. However, as stated above, it is HIGHLY UNLIKELY the housemate cats will develop clinical FIP. Even in instances when FIPV carriers are known to be present in a household, the chances of other cats developing clinical FIP are very rare and at best, sporadic. However, as a pet lover and cat owner, I recognize the term "highly unlikely" does not help nor make one feel better when it is your cat or kitten that becomes sick with this deadly disease.

Can I Protect my Cat from FIP?

Environmental exposure to FIP from infected cats is not a source of clinical FIP. Therefore, measures to eradicate or minimize the virus and FIP infection within a group of cohabitating cats is probably not effective. That being said, it is always a good idea in multi-cat households, shelters and rescues, and catteries to:

  • Keep the cats as healthy as possible and minimizing exposure to other infectious diseases (example: Feline Leukemia) decreases the likelihood of cats developing FIP.
  • Keep litter boxes clean and located away from food and water dishes. Feces should be scooped and disposed of on a daily basis, and the litter box should be thoroughly cleaned and disinfected regularly (once a month).
  • Prevent overcrowding, keeping cats current on vaccinations, and proper nutrition may also help to reduce the occurrence of FIP.

Additionally, there is clinical evidence suggesting the incidences of FIP are higher in places where over-crowding exists, lack of cleanliness is present (i.e., dirty and unscooped litter boxes and lack of cleaning/disinfecting), and obviously places where cats of unknown origin are housed too close together (shelters and rescues). And, yes, at some cat breeders (catteries) because of the afore-mentioned reasons.

Why Your Breeder Does Not Want Your Cat Vaccinated For FIP?

The American Association of Feline Practitioners Feline Vaccine Advisory Panel does NOT recommend the FIP vaccine. Also, vaccinating the cat with the FIP vaccine will then result in "positive" antibody titers for feline coronavirus - a "false positive" test result.

Our Experience with FIP

I am a life-long cat owner (over 50 years) and have been breeding and showing Persian cats for almost 20 years now. This amounts to (an estimate only) about 50 adult cats and 200 kittens coming into and out of my home over the combined 50 years of owning cats.

How many times have I personally had, or any of my kitten buyers had, an instance of clinical FIP? 

In almost 20 years of breeding, raising, and showing Persian cats, I have had one suspected case (but a necropsy was inconslusive) in a year old cat I owned. Additionally, during my time as a breeder, I have been notified by five different kitten buyers of suspected FIP cases. In the cases, where necropsies were done, they were inconclusive. But, it is my belief these instances were FIP. While FIP is CERTAINLY not my fault nor the fault of my kitten buyers, I now offer an FIP guarantee in our Health Guarantee.

It is VERY IMPORTANT that all cat owners and potential kitten buyers do not panic when hearing the term "FIP" and the proliferation of so much untrue and inaccurate facts contained on the internet, and even some veterinarians that do not keep up-to-date about the most current research and recommendations.

According to the most up-to-date information on FIP, my low occurrence rate of FIP is, in all probability, due to the following facts:

  • I house my Persians in small groups, (less than 4 adults). No over-crowding.
  • My adult breeding males are kept separate from all the other cats except at breeding time at which time, a male cat is only "temporarily" housed with one female at a time.
  • New arrivals are isolated for approximately six to eight weeks from our other cats.
  • If and when a cat becomes ill, it is isolated/quarantined from other cats/kittens.
  • Kittens are housed with their mom individually, or sometimes, two moms may co-parent their babies.
  • I am consistently cleaning and disinfecting our entire home, rooms where our cats may reside at any given time, "cat" room, and cat enclosures.
  • I am consistently cleaning and disinfecting litter boxes, bowls, bedding, etc.

Does this mean one of my kittens may not at some time develop FIP?

No, I cannot guarantee that. No one can, no cattery can, no shelter can, no rescue group can, (etc.). Veterinarians cannot even predict which kitten or cat will have active, clinical FIP, so how can I? All I can do is continue to keep my numbers small, keep my cats and kittens as healthy as possible, use good cleaning and disinfection practices, and feed a healthy diet – all to keep my cats (and kittens) as stress-free and healthy as possible.

Additional General Information on FIP

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