FIP or Feline Infectious Peritonitis

If you are a cat owner, or you are looking for a new kitten you need to know about FIP, how to spot the warning signs and how to avoid it.

FIP and feline coronavirus

FIP is the abbreviation used for Feline Infectious Peritonitis. FIP is a horrible illness that affects cats every year, and it is poorly understood at the moment. Thankfully, FIP is relatively rare and there are many things we can do as breeders and cat owners to reduce our risks.  

What is FIP?

FIP occurs worldwide in domestic and wild cats. There are two types of FIP: wet, or effusive FIP and dry, or non-effusive FIP.

Please be cautious:

  • it is estimated that up to 80% of FIP cases are misdiagnosed!
  • A positive feline coronavirus result is not a diagnosis of FIP. Even a very high titre for feline coronavirus is not a diagnosis of FIP.
  • There are other illnesses, including cancer and Bovine TB, that have exactly the same symptoms as FIP.
  • So it is essential to have a diagnosis confirmed by a specialist centre, not just by your local vet.
  • if you treat a cat for FIP when they actually have another condition it will have a seriously detrimental effect on their health.

What causes FIP?

FIP is caused by a complex and multiple mutation of Feline Coronavirus within the affected cat's body. This is not covid-19: feline coronavirus has been around for many decades. 

It is estimated that 60-90+% of cats are exposed to Feline Coronavirus at some point in their lives. Of these cats:

  • Around 90% will fully recover, although it usually takes around 3-7 years.
  • 5% will recover but continue to shed feline coronavirus in their feces permanently, which means that they can infect other cats in their environment with coronavirus
  • In the remaining 5% of cats, a complex chain of events occurs which causes feline coronavirus to mutate into FIP, or Feline Infectious Peritonitis. This mutation appears to happen differently in every cat. When it mutates it has a systemic effect on the cat, affecting the cat’s entire system, including their immune system. What exactly causes the mutation is not yet known, although several risk factors are suspected of contributing to the process. It is a complex process that has only recently begun to be understood.
  • It is estimated by Dr Pederson that some 40% of the entire cat population are shedding coronavirus at any given time.
  • For FIP to develop, at least three separate mutations/processes have to occur within the affected cat's body. 
  • This means that FIP is not contagious. Feline coronavirus is, but coronavirus on its own does not equal FIP. 
  • A cat that is never infected with feline coronavirus will never develop FIP. 

All of our adult cats have tested negative for feline coronavirus.

You can read more about Feline Coronavirus here.

FIP and Feline Coronavirus feline infectious peritonitis
Feline Coronavirus and FIP

FIP: treating FIP

2018 update: there is now a potential treatment path for some cats diagnosed with FIP! 

2020 update: there is a new antiviral drug available that has apparently cured many cats of FIP. It is expensive and must be administered early, but it appears to be highly effective. 

The earlier FIP is diagnosed and the treatment path is started, the better the outcome for the cat. Niels Pederson, an American researcher, has successfully cured some cats of FIP.

  • This is cutting edge veterinary science and the treatment is still experimental: it is not guaranteed to be a success, but it is the only treatment path that has had any success so far.
  • Previous treatment involved a cocktail of:
    • good nutrition
    • antibiotics
    • anti-inflammatories
    • immune suppressants
    • cortico-steroids
    • vitamins
    • the new treatment is: one or two new anti-viral drugs that were initially developed for human use. These drugs are still being commercially developed and are not widely available but seem to able to be imported from America by your vet. Please note: the drugs only work if they are given to your cat very early on in the disease, before the damage caused is too great.
    • read more about FIP treatment

If you suspect your cat has FIP, or if your local vet has told you that your cat has FIP, you need to contact an FIP specialist to have the diagnosis confirmed and to get the treatment path designed to fit your cat's needs.

FIP Risk Factors: avoiding FIP

Clearly, it is far better to avoid FIP altogether. It is thought that there are multiple factors that may significantly increase the chances that feline coronavirus will mutate into FIP:

  • The strain/variety of feline coronavirus (there are multiple versions of the virus and it is thought that some may be more virulent and more likely to mutate than others)

  • Stress: feline immune systems are highly affected by stress, so any stress to the cat can cause the immune system to temporarily weaken which, it is thought, can contribute to allowing FIP to develop.

  • Overcrowding: overcrowding increases the risks of FIP in multiple ways:

    • It cases cats to become stressed. Cats are not meant to live in large groups. In the wild, only lionesses live and work in packs. All other cats lead largely solitary lives. Overcrowding forces cats to share their territory with far more cats than they would naturally choose to. This leads to social stress, too many scents, over-stimulation, bullying, territorial issues and a whole load of unhappiness and distress.

    • Overcrowded cats are almost certain to be sharing a litter tray, making it impossible to keep the litter tray clean

    • It also provides multiple hosts for feline coronavirus, and many other infectious conditions. This means that the risk of each cat becoming infected is very high. It also means that any cat who clears the infection is likely to become re-infected very quickly. Worse than that, because of the speed at which the virus will be replicating itself in all of the hosts present, it is far more likely to develop into a virulent and dangerous strain of feline coronavirus. These virulent strains are thought to be much more likely to mutate into FIP.

    • Additionally, overcrowded cats will also be at risk of other conditions, like Tritichomonas Foetus, Giardia, ringworm, campylobacter, e-coli etc. Any cats with multiple conditions and illnesses will be under much more stress and therefore much more likely to develop FIP.

  • Shared litter trays: feline coronavirus is transmitted between cats via the fecal-oral route. Basically it is a stomach bug for cats. The virus enters the body through the mouth and leaves in the feces, hoping to find another host. If a healthy cat shares a litter tray with an infected cat, the healthy cat will become infected with feline coronavirus almost immediately. Coronavirus can live in fecal matter for 8 weeks or more, so a shared litter tray is an absolute no-no!

  • Poor hygiene: given that coronavirus is a stomach bug, the need for good hygiene is clear. Dirty litter trays, cat towers, carpets and toys provide a breeding ground for coronavirus.

  • The age of infection: cats who are very young or very old when they are initially infected with feline coronavirus are thought to be at higher risk of developing FIP. That being said, cats of any age can develop FIP. If a cat is going to develop FIP, it usually happens within one year of the cat becoming infected with feline coronavirus, but this is not always the case.

  • Genetics: it is thought that some cats may be more genetically susceptible to developing or resisting FIP, although this has not been scientifically proven. As a result of this, it is advisable not to repeat any mating that has sired a kitten that has developed FIP. This genetic link has not been proven. 

  • Inbreeding: inbreeding reduces genetic diversity and this can weaken the immune system when it is done to the extreme.

What we do to reduce the risk of FIP

All of our cats have tested negative for feline coronavirus.

Our main aim is to raise healthy kittens. We therefore do everything we can reasonably think of to ensure that our kittens are as healthy as they possibly can be when they leave us. If ever we were not satisfied that a kitten was healthy, we would keep them with us until we were (thankfully this has never happened yet).

We want our kittens to be free from all infectious conditions, parasites, viruses and other nasties. Fortunately, excellent husbandry and hygiene are equally helpful in preventing all of these horrible illnesses, including Feline Coronavirus.

The first step in achieving this is to understand what infectious conditions can affect cats and kittens. Once we understand what can affect them, and how these things work, we can then work to reduce our risks.

Feline coronavirus is a minute and highly infectious virus. It can survive on clothes for 8 weeks. It can survive normal wash cycles, although a 60C wash will kill it. Feline coronavirus can be brought into your home on your clothes, or on a visitor’s clothes. It is therefore impossible to absolutely guarantee that any home is completely free from feline coronavirus, but it is possible to hugely reduce your risks.

The biggest risk factors for Feline Coronavirus and FIP (and a whole load of other nasty conditions) are overcrowding, large groups of cats sharing litter trays and food and water bowls, and poor hygiene. Unfortunately many breeding households and cat shelters suffer from all of those factors because they simply do not have the time, the space or the financial resources required to avoid them.

In order to reduce our risks we take the following approach:

  • We test our adult cats for feline coronavirus and all have tested negative. This has been achieved through careful husbandry, hygiene and nutrition. 

  • We completely empty and clean our cats’ litter trays every day and use a veterinary strength anti-viral that will kill Feline Coronavirus, along with most of the other nasties

  • Our cats are never kept in crowded conditions

  • Our kittens only ever have contact with their own littermates and their own mum

How to avoid kittens at high risk of Coronavirus and FIP

Choose a breeder who has tested their cats for feline coronavirus. This gives you the only real chance of avoiding heartbreak. If you cannot find a breeder who is testing their cats for feline coronavirus, then consider the following points: 

  • Make sure that your kitten has come from a household or cat rescue where their cats do not share litter trays, food or water bowls. This is absolutely vital.

  • Check that cats and kittens are not kept in crowded conditions and that the kittens only have contact with their own littermates and their own mum

  • Make sure that litter trays are completely changed and cleaned every day. Just scooping the litter tray is not sufficient at all, because it will leave the virus in the surrounding litter. Viruses are microscopic organisms - they can’t be scooped out!

  • Ask the breeder or cat shelter about Coronavirus and FIP. They should know about it in detail and they should be able to tell you a whole host of steps they take to reduce the risks. If they don’t know much about it, don’t want to talk about it, or look a bit awkward when you raise it, move on and keep looking.

  • Be warned: if you look up the policies of some of the biggest cat rescues, they advise their staff not to mention coronavirus, even when there has been a recent FIP death at the shelter!

  • It will take time to find a breeder or cat rescue that you are happy with. When you do find one, be prepared to wait for a kitten. Do not rush into it….you will almost certainly regret it if you do.

  • The prevailing attitude is that feline coronavirus is endemic in the cat population and there is therefore nothing that can be done about FIP. We disagree with this: these conditions are endemic in the cat population but there are things we can do about them! Not all breeders/cat rescues accept these conditions as ‘normal’. Make sure you get your kitten from someone who is aware of these conditions, does not accept them as normal, and is actively taking steps to combat them.

  • There can never be any guarantee that a kitten will never develop FIP. Even if a kitten is free from coronavirus when you collect them, they may come into contact with it at some point in their life, and they could then develop FIP. But, whilst we cannot control everything, there are many things that we can do to reduce our risks, and it is important that we all take those steps.

Other conditions to be aware of when choosing your kitten:

  • Feline Coronavirus

  • Tritichomonas foetus

  • Giardia

  • Cryptosporidium

  • Campylobacter and other bacterial infections (kittens fed raw meat are at very high risk!)

  • Bovine TB - a risk of raw feeding, with the same symptoms as FIP

  • Feline herpes virus

  • Chlamydia


  • FIV

  • Feline Enteritis/cat flu

All of these conditions are infectious conditions and multi-cat and breeding households are all at high risk. We will deal with each of these conditions in later articles.

To understand more about Feline Coronavirus, its symptoms, diagnosis and management, read our article on Feline Coronavirus.

More about our approach...