Cat FIP Signs & Treatment: Vet-Reviewed Facts & FAQ
Feline infectious peritonitis (FIP) is a disease caused by a mutation of feline coronavirus (FCoV). FCoV isn't the same as COVID-19 and isn't contagious to humans. Most of the time, a cat exposed to FCoV will not get sick because only 10% of cases morph into FIP. Until recently, the prognosis for cats with FIP was grave. With no treatment available, FIP was invariably fatal.
The good news is that there are now multiple treatment options available, and although FIP is still a potentially deadly infection, cats now have a real chance of recovery.
Let’s take a closer look at the signs, diagnosis, and treatment of feline infectious peritonitis.
FIP Causes & Signs
FIP is caused by a mutation of the FCoV virus, which can occur at any time after your cat is exposed to FCoV, even years later. Strains of feline coronaviruses will usually live dormant in your cat’s stomach, but for reasons that are still not fully understood, sometimes it will morph into FIP.
Cats exposed to FCoV might have diarrhea and/or mild respiratory signs, but most times your cat’s immune system will build antibodies that will make it immune to the virus within 7–10 days after exposure. In some cases, the immune response fails, and the virus mutates into FIP. Although this can occur at any time after viral exposure, FIP is usually seen in young cats or kittens, elderly cats, or immunocompromised cats.
FIP has two distinct presentations: effusive (aka ‘wet’) FIP or non-effusive (aka ‘dry‘) FIP. Both wet and dry FIP typically share common non-specific signs such as fever, weight loss, depression, and loss of appetite.
Effusive specific signs (more common):
Non-effusive specific signs:
How Is FIP Diagnosed?
There is no simple blood test for FIP. If your cat has been exposed to feline coronaviruses, they will test positive, regardless of whether they developed immunity or not. Because of this, a FIP diagnosis requires a combination of blood tests and physical symptoms.
Studies have indicated that FIP has a relatively high misdiagnosis rate, the implications of which were even more devastating in the past when euthanasia was often recommended following an FIP diagnosis to prevent unnecessary suffering.
What Are the Treatment Options?
Until quite recently, there was no known cure for FIP, and a positive diagnosis was a death sentence. One positive development to come from the COVID-19 pandemic was the further development of a drug called Remdesivir. For several years, this injectable treatment was being used to treat cats in Australia, the UK, and Europe, but had not been approved for use in the US. Even now, Remdesivir is difficult to obtain in the United States.
In 2024, an oral formulation of the same drug, known as GS-441524, was approved by the FDA, with very promising results, providing a safe and effective treatment for this once-fatal disease. It is now widely used for the treatment of FIP, though the combination of both oral and injectable treatments may give even better results.
These medications are not a guaranteed cure, and some cats with FIP may still succumb to the disease despite treatment, but at least now there is a chance of recovery.
How to Prevent Your Cat From Developing FIP
The most challenging part of FCoV is that the method of infection and exactly how or why certain cats go on to develop FIP is still poorly understood. FCoV is ubiquitous in the environment, particularly in areas with high-density feline populations. Although FCoV is considered to be highly contagious, spread through the ingestion of infected fecal or saliva particles, FIP is not believed to be shed in the saliva or feces.
Poor nutrition, overcrowding, and stress are believed to be key factors in whether or not FCoV becomes FIP, so the best way to minimize your cat’s risks is to provide them with a high-quality, nutritionally balanced diet, take steps to reduce stress and anxiety, and be strict about food bowl, water bowl, and litter box hygiene.
Should I Vaccinate My Cat Against FIP?
The American Animal Hospital Association does not recommend vaccinating against FIP because the vaccine is only effective in seronegative cats — those that have not been exposed to FCoV — and most cats are seropositive by the age of vaccination. Cats who received this vaccine in laboratory studies developed Antibody-Dependent Enhancement at a higher rate than unvaccinated cats because their naturally occurring antibodies attacked the viral antigen introduced by the vaccine.
Essentially, in the case of the FCoV vaccine, the potential side effects far outweigh the potential benefits.
Conclusion
Feline coronavirus is common in cats, but thankfully most infections will not result in FIP. While there is still much to be discovered about this disease, FIP is no longer an automatic death sentence, and the prognosis for affected cats is far better now than it was a decade ago.
Taking care of your cat’s overall health and well-being plays a huge role in prevention because having a healthy immune system is the main way your cat can defeat FIP.
See Also:
Featured Image Credit: Maria Sbytova, Shutterstock
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Christian started writing for a local newspaper as a teenager, and he's been involved in the publishing industry for most of his adult life. Combining his love of writing with a passion for animals, he is currently the Director of Editorial at Pangolia and the Editor-in-Chief at Catster.
Christian lives in the Philippines with his wife, son, and four rescue cats: Trixie, Chloe, Sparky, and Chopper.
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