Feline infectious peritonitis in cats


  • Feline Infectious Peritonitis (FIP) is an uncommon but serious disease caused by feline coronavirus.
  • Feline coronavirus is not the same virus as Covid-19 and cannot spread to humans.
  • Feline coronavirus is common in cats in the UK - most cats that have it remain healthy but a small number develop FIP.
  • Cats who are young, live with lots of other cats, and who have recently been stressed are at a higher risk of developing FIP.
  • Feline coronavirus mostly spreads in faeces (poo), so having enough litter trays and cleaning them regularly can help to prevent spread.
  • Early signs of FIP are vague and can include eating less, weight loss, low energy, and diarrhoea. Later signs of FIP can include a swollen tummy, tremors and seizures.
  • FIP can be difficult to diagnose as there isn’t one test that will confirm the infection.
  • Until recently, FIP was fatal for most cats but a new anti-viral treatment means vets now have a better chance of successfully treating it.

What is feline coronavirus and FIP in cats?

Feline Infectious Peritonitis (FIP) is a serious disease caused by feline coronavirus (FCoV). Feline coronavirus is common in cats in the UK but most cats that have it remain healthy, or just have a mild tummy upset such as diarrhoea. In a very small number of cats that have feline coronavirus, FIP can develop when the feline coronavirus mutates (changes into a new form) and the cat’s immune system reacts in a certain way.

Feline coronavirus is not the same virus as Covid-19 and cannot spread to humans.

Cats of all ages and any breed can develop FIP but there may be a higher risk if your cat:

  • Is young - less than 2 years old.
  • Is kept with lots of other cats for example a breeding colony or rescue centre.
  • Has recently had a stressful event for example adoption, staying at a cattery, moving to a new house, breeding, spending time in a rescue, respiratory disease, or the introduction of a new cat into your house.
  • Is a pedigree breed for example British Short Hair or Ragdoll.

How does feline coronavirus infection spread?

Feline coronavirus spreads in faeces  (poo) and less commonly in saliva. This means it is most likely to spread if multiple cats are sharing the same litter tray. It can also spread on food bowls, when cats groom each other and possibly through sneezing. Most cats shed the virus in their faeces  for a few months and then stop. A small number of cats continue to shed the virus for their whole life.

Symptoms of FIP in cats

The early signs of FIP are vague - you may just notice your cat being generally ‘unwell’. This may happen suddenly or ‘wax and wane’, which means it happens on and off over a period of time, with your cat having good and bad days. Early symptoms include:

It is important to remember many of the symptoms above are common and could be caused by many conditions other than FIP. As the infection continues, it turns into a wet or dry form of FIP.  Sometimes a mixed form involving both forms can develop.

Wet form (most common):

Dry form:

  • Neurological symptoms for example loss of balance, tremors, blindness, seizures
  • Yellow gums (jaundice)
  • Lumps in the abdomen (tummy) as organs get bigger
  • Uveitis – inflammation in the eye. The eye may be cloudy, your cat may paw at their eye, avoid bright light, keep it shut or squint.
  • Blood in the eye

It’s important to contact your vet for an appointment straight away, if your cat shows any of these symptoms.

Brown and white cat lying in the shade on a pavement with a swollen tummy


Feline infectious peritonitis can be very hard to diagnose. There are lots of other illnesses that have similar symptoms and there isn’t one specific test that will confirm a diagnosis of FIP.  

Your vet may need to do a combination of blood tests, scans and take a fluid sample from your cat’s tummy or chest if they are suspicious of FIP. Tests on this fluid can sometimes confirm FIP if alongside this, your cat also has the typical symptoms of FIP and changes on their blood tests. However, sometimes a diagnosis can only be made after testing a sample of tissue (from surgery) or after your cat has passed away by doing a post mortem.


Sadly, without treatment, most cats will die within days or weeks of diagnosis of FIP.  A new anti-viral drug is available from vets in the UK, which can be used to successfully treat cats with FIP. However, it is expensive and needs to be given for a long time.

Your vet may recommend the following treatments:

  • Anti-viral medication: Most cats will improve within days after starting treatment, but sometimes symptoms can get worse before they get better. The treatment usually lasts at least 12 weeks and often involves injections, tablets, or a liquid, which may be given in a combination. Your vet will decide what your cat needs, depending on what form of FIP they have, how ill they are and how they respond to the treatment. Your cat will need to be closely monitored by your vet during the treatment as it is important for them to be weighed regularly to ensure they are still getting the correct dose, and they may need blood and urine (wee) tests. Black market medicines are available, however as they are not regulated their contents and safety are unknown. Our vets strongly advise getting all medications from your vet to ensure they are on the correct dose and being monitored closely. A small number of cats may not respond to FIP treatment and relapse of FIP after the treatment has finished is possible but uncommon.
  • Steroids: Can improve quality of life but for a limited time and unfortunately won’t cure the disease.
  • Supportive treatment:
    • A fluid drip if your cat is dehydrated
    • Medication to increase appetite
    • Fluid can be drained from the tummy or chest to relieve pressure but this is rarely done as it builds up very quickly again
    • Eye drops if their eyes are affected
    • Anti-seizure medications

A cat with suspected or confirmed FIP should be kept indoors, completely separate from other cats. They should have their own food bowls, water bowls and litter tray and these must be cleaned daily.

Sadly, if your cat is suffering with FIP and treatment isn’t helping or isn’t an option due to cost, it may be kinder to put them to sleep. Without anti-viral treatment, most cases of FIP will be fatal.


There is currently no FIP vaccination in the UK and no way to prevent the feline coronavirus mutating into FIP.

Your cat is at a higher risk if they live with lots of other cats as they are more likely to be in a stressful situation and feline coronavirus can spread more easily. To help prevent FIP in your cat:

  • Avoid overcrowding – ideally no more than 4 cats in a household
  • Have enough litter trays - one for each cat plus one extra
  • Practice good hygiene – clean poo from litter trays daily as this is the main source of feline coronavirus and keep litter trays separate from feeding areas
  • Avoid stressful situations if possible such as rehoming, catteries or breeding
  • Do not breed from cats that have had more than one litter where kittens have had FIP as this may be as a result of a genetic link

In most cases, cats that have been in contact with a cat that has had FIP will not get the disease.


Without treatment, if your cat has been diagnosed with wet FIP, they will sadly pass away often within 2 weeks of diagnosis. If your cat has been diagnosed with dry FIP, your cat may survive a few months.

The outlook with anti-viral medication is good. Although the course of treatment is long and can be expensive, most cats who receive treatment will make a full recovery.

If your cat's quality of life is poor and treatment has not helped or isn’t an option due to cost, euthanasia may be the kindest option.

When to contact your vet

Contact your vet if your cat is showing any of the symptoms of FIP or feline coronavirus. If your cat has been previously diagnosed with FIP and seems ‘out-of-sorts’ have them checked as soon as possible. Similarly, if your cat has been in contact with or is related to a cat that has had FIP and they seem unwell, contact your vet straight away.

You know your cat best. If they don’t have the symptoms listed above, but you are still concerned it’s always best to contact your vet.


Treatment for feline infectious peritonitis (FIP) can become very expensive, so it’s important to speak openly with your vet about the cost of treatment, your finances, and what you think is right for your cat.

Consider insuring your cat as soon as you get them, before any signs of illness start, to ensure you have financial support to care for them.


Do I have to get medication from my vet for my cat that has been diagnosed with FIP?

Our vets strongly advise getting all medications from your vet to ensure they are on the correct dose and being monitored closely. Black market medicines are available, however as they are not regulated their contents and safety are unknown.

Can I vaccinate my cat against FIP?

There is no vaccine for FIP currently available in the UK. There is a FIP vaccine in the USA and some parts of Europe. It is given to cats over 16 weeks old, which may be too late to protect kittens if they are in a house where the virus is already present. Most adult cats will already have been exposed to the feline coronavirus and thus have some immunity.

Can I catch FIP?

There is no evidence that FIP can cause disease in humans or other animals. It can affect big cats such as cheetahs in zoos or in the wild.

Can my cat infect another cat with FIP?

It is rare for a cat with FIP to directly infect another cat with FIP because FIP virus particles don’t easily shed and spread to other cats. Unlike feline coronavirus which does spread, but usually doesn’t cause disease.

Published: November 2023

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Written by vets and vet nurses. This advice is for UK pets only. Illustrations by Samantha Elmhurst.