The Truth About FIP In Cats

Feline infectious peritonitis (FIP) is a fatal, incurable disease that affects cats. It is caused by Feline Infectious Peritonitis Virus (FIPV), which is a mutation of Feline Enteric Coronavirus (FECV) – (Feline coronavirus FCoV).

Many shelters and veterinarians routinely “euthanize” all cats who test positive for FIP even if the cat doesn’t show any sign of illness. This is so wrong!

Infection with coronavirus is actually very common in cats, but most of the time it does not cause any problems, other than perhaps mild self-limiting diarrhea but not all the time. FIP occurs when the cat’s immune system reacts inappropriately to feline coronavirus (FCoV) infection. FIP is the name of the disease, FCoV (sometimes called feline enteric coronavirus, FECV) is the name of the virus. The vast majority of cats simply become infected, shed FCoV for some months, mount a successful immune response, eliminate the virus and live happily ever after. However, for reasons that are not fully understood, instead of clearing FCoV infection, an unfortunate few cats develop FIP.

FCoV is shed in the secretions and excretions of infected cats. Feces and oropharyngeal secretions are the most likely sources of infectious virus. Dried virus in a 21 degrees C (70o F) environment can remain infectious for at least six weeks. Fortunately, FCoV is readily destroyed by most common disinfectants and detergents and thorough cleaning will substantially reduce the concentration of infectious virus.

Nearly every veterinary diagnostic laboratory offers a “FIP test” to veterinarians. This test is simply a test to measure the presence of antibodies against coronaviruses. These coronavirus-specific antibodies are present in 80-90% of cats in catteries, and in 10-50% of cats in single-cat households. The presence of antibodies in the blood stream DOES NOT mean that the cat has FIP. Only 5-10% of coronavirus-infected cats can develop FIP in a cattery setting, and the incidence is much less in a single-cat household.

According to James Richards, DVM, former director of the Cornell Feline Health Center at Cornell University’s College of Veterinary Medicine, some cats can’t mount an effective immune response when exposed to FCoV because they may too young, too old, too stressed or ill from some other disease to have an adequate immune response.

“FIP develops when a usually harmless strain of FCoV mutates in the cat in a way that gives the virus the ability to replicate itself in some of the cat’s white cells. When the immune system mounts a defense against the invaded white cells, which are themselves infection-fighting cells, the immune system ends up damaging its own protective cells and tissues,” says Dr. Richards. The result is an intense inflammatory reaction in the tissues where the virus-infected cells reside, which causes damage to multiple systems at once and ultimately leads to death.

In an affected cat, the virus spreads throughout the body and can cause a wide range of different signs (including peritonitis with the accumulation of fluid in the abdomen, but in other cats fluid may accumulate in the chest cavity; in others the virus may cause inflammation affecting the brain, eyes, liver, kidneys or elsewhere).

A vaccine to prevent FIP is available, but considerable controversy surrounds its ability to prevent disease.

Prof. Neils Pedersen once famously said that more cats had died of FIP tests than of the disease.

Please SHARE to raise awareness: A healthy cat should NEVER be euthanized because of a positive test for feline coronavirus – even if the test has been mis-named a FIP test!