In this pet care education article, our guest contributor, Dr. Tegan Hunt, Veterinarian, will explain how your vet will diagnose and treat Feline Infectious Peritonitis:

As always, this information is published to increase your awareness and education as a pet owner so that you can seek treatment from your veterinarian as soon as possible. This article is not a substitute for a visit to the vet. Your Vet is in the best position to make an appropriate diagnosis and prescribe the necessary treatment.  



Feline (Cat) Infectious Peritonitis

Feline (cat) infectious peritonitis, or FIP, is a disease that is found around the world and can occur in both domestic and wild cats. The disease occurs after infection with a virulent (extremely severe) feline coronavirus that then mutates, leading to multisystemic disease (affects many organs).



What causes Feline Infectious Peritonitis?

Cat or Feline infectious peritonitis (FIP) is caused by a very common feline coronavirus (FCoV). The FCoV infects the intestinal tract and is then shed in the feces. Infected cats typically don’t show symptoms or they develop mild diarrhea that is self-limiting (resolves by itself). However, in some cats, the virus mutates and this causes the avirulent coronavirus (not harmful or causing infection) to become the virulent (severe and harmful) form (FIPV) that causes FIP.

How is FIP transmitted?

Infection with FCoV and transmission of FIP from one cat to another occurs through the fecal-oral (poo to mouth) route. For example, another cat sharing the litter box with an infected cat.

How does FIP develop?

FIP is believed to be an immune-mediated disease that develops when the FIP virus attracts antibodies and infects white blood cells (macrophages and monocytes). These infected cells then carry the virus throughout the body, allowing the mutated virus to enter many of the host’s tissues (including organs).

As a result of this, an intense inflammatory response develops and an increased vascular permeability occurs (the ability for cells to pass through a membrane). Immune complexes form and contribute to vessel damage and vasculitis (vessel inflammation). It is this interaction between the body’s own immune system and the virus that is responsible for the disease.

In order for your vet to diagnose and treat Feline Infectious Peritonitis, they will need to check for various symptoms and run clinical diagnostic tests.


Healthy, happy pets are our passion and all the cats shown on this page are well and content.

What are the symptoms of FIP?

There are two main forms of FIP and each form has clinical signs that your vet will look for.

The Effusive or Wet Form

The effusive or so-called ‘wet’ form of FIP is generally an acute form (sudden and severe) that develops 4-6 weeks after a stressful event (e.g. moving your cat to a new home, surgery, arrival at an animal shelter). This is the more rapidly progressing form.

Clinical signs include fever, anorexia (loss of appetite for food), weight loss and lethargy (lack of energy). A typical feature of wet feline infectious peritonitis is the leakage of proteins and the accumulation of fluid in body cavities, like the abdomen, or the chest, or both of these.

The Non-Effusive or Dry Form

The non-effusive or so-called ‘dry’ form of FIP occurs after an incubation period that can vary from months to years.
The clinical signs from dry FIP arise from granuloma formation (a mass of granulation tissue, typically produced in response to infection, inflammation, or the presence of a foreign substance) in organs. Your cat may present with clinical signs that include chronic weight loss, depression, anemia, and a persistent fever.


Ongoing cat care and regular health checks are important to keep our feline friends healthy, like these cats.

How do you treat FIP

There is currently no cure or effective way to treat Feline Infectious Peritonitis and FIP is classified as a terminal disease.

Current treatment is supportive and FIP can be managed to a certain extent with good nursing care and nutrition. This supportive care may also include hospitalisation, fluid therapy, electrolyte corrections, draining accumulated fluids, and blood transfusions.

Treatment with medications is also aimed at alleviating the inflammatory response of the disease. Cats with FIP are often treated with corticosteroids (e.g. prednisolone), cytotoxic drugs (e.g. cyclophosphamide), antiemetics, appetite stimulants and antibiotics (if secondary infection occurs).

Some treatments can potentially lead to short-term improvements in a small percentage of cats.

Monitoring and prognosis

Cats with FIP should have frequent veterinary revisits and revisions. Red blood cells, globulins, and A:G ratio is repeatedly evaluated and can serve as indicators of the patient’s health. The prognosis for cats with FIP is poor. Supportive therapy may help prolong survival time, but over time the cat will succumb to FIP. Cats with effusive FIP may only survive for days to weeks. Cats with non-effusive FIP may survive for weeks to months and sometimes longer.

Ongoing research

At this time, there is research being performed to try and find other immunosuppressive drugs that could slow down the progress of the disease. There is also a current investigation into antivirals that may prevent or slow down the virus from replicating. However, these are still being assessed through diligent studies surrounding their efficacy and potential side effects and they are not approved for veterinary use.

While your vet can diagnose and treat Feline Infectious Peritonitis to a point, the terminal nature of this disease really means that prevention is the priority. 


Your cat care efforts will hopefully be rewarded with plenty of purrs and boops.

Prevention of Feline Infectious Peritonitis

In order to prevent Feline Infectious Peritonitis, it is important to keep cats as healthy as possible.

  • Reduce their exposure to infectious agents. Frequent cleaning of litter boxes is important.
  • Minimise stressful environments or stressful changes.
  • Avoid overcrowding
  • Keep cat(s) up to date with vaccinations, and
  • Provide good nutrition.

Good animal husbandry and appropriate care help decrease the occurrence of FIP.


More about Dr. Tegan Hunt, BVSc.

Tegan practices as an Emergency Veterinarian in Brisbane, Australia. She is passionate about all things related to animals and has a special interest in educating pet owners. You can follow her work on Instagram at dr.teganadel_ vet and on Chocolate for Dogs as well as her YouTube Channel: Chocolate for Dogs.

If you enjoyed this article on how to diagnose and treat Feline Infectious Peritonitis then you may also like to read more blogs by Tegan:

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