Pet Factsheets

Feline Infectious Peritonitis (FIP)

Hearing that your cat has Feline Infectious Peritonitis (FIP) is one of the worst bits of news you can get from your vet. The disease is almost always fatal although treatments can make your cat's remaining time more comfortable. If you have more than one cat in your home, taking sensible precautions and following your vet's advice can help to reduce the risk that your other cats will be affected.

What is FIP?

The disease is caused by a virus, feline coronavirus (FCoV), which is often found in healthy cats and usually causes no major health problems. However, in some cats it causes serious disease. The disease has two different forms. The more common form is called 'wet ' or 'effusive' FIP, where blood vessels leak protein-rich fluid into body cavities. Most commonly this fluid accumulates in the abdomen, causing it to swell leading to a 'pregnant' appearance. Fluid accumulations may also occur in the chest, causing life-threatening breathing problems. The less common form of the disease is 'dry' or 'non-effusive' FIP in which inflammatory nodules develop in the cat's internal organs and can cause a wide variety of clinical signs.

Except in rare cases, wet FIP is fatal within about five weeks of diagnosis (often within two weeks). The dry form is equally deadly but affected cats may survive for a few months. This situation may change as newer drugs become available but at time of writing the experimental drugs showing promise are not commercially available (March 2019).

Will my cat 'catch' FIP?

FIP does not spread between cats but FCoV, that can trigger disease, is highly infectious. Infection with FCoV is very common, particularly in cats from rescue shelters, breeding catteries and other large multicat households. FCoV is mostly spread in faeces (droppings / poo), but can also be found in saliva. FIP develops as a result of viral mutations within individual cats.

The greater the viral burden within a household and the greater the viral turnover within an individual cat, the more likely that FIP with occur. Only about one in a hundred cats is likely to go down with the disease but the risk is much higher where several cats live together such as in a breeding cattery or rescue centre. Overcrowding and other stressful factors can increase the risk of disease developing.

The most vulnerable cats are those with weak defences against infectious diseases, eg kittens, elderly cats and those already suffering from some other condition. Some pedigree breeds (eg Birman, Bengals and Rexes) appear to be affected more often than ordinary domestic ‘moggies’ in some studies.

How does my vet know my cat has FIP?

In its early stages, FIP causes a variety of clinical signs which are common to many other diseases, eg weight loss, lethargy, a dull coat, diarrhoea, poor appetite and fever, as well as FIP and may not be present in every case. In cats with the ‘wet’ form of FIP, fluid may build up in your cat's abdomen (causing swelling of the tummy) or chest (causing difficulty in breathing). In cats with the ‘dry’ form of FIP, your cat's eyes or nervous system may be damaged causing a change in the colour of the eye, blindness, wobbliness when walking, tremors and even seizures.

There is no reliable blood test to show that your cat has FIP. Blood tests may indicate that your cat is fighting an infection and that your cat has been infected with the virus that can trigger FIP. Where fluid has built up in the chest or abdomen these can be sampled and analysed; in some cases these can give a strong suggestion of FIP or even confirm infection. In many cases the only sure method of diagnosis is to take a tissue sample from one of the internal organs – but invasive sampling may cause discomfort and can be costly. Tissue sampling is often done after the cat has died to confirm the cause of death as FIP.

Can I catch FIP?

There is no evidence that FIP can cause any disease in humans or other animals such as dogs. Rarely it can affect big cats such as Cheetahs in zoos or in the wild.

What can be done to treat my cat?

Medicines such as steroids and vitamins are often given to make your cat feel better, but they do not tackle the disease itself. With careful treatment you may be able to keep your cat healthier for a little longer. Interferon (a powerful drug that suppresses immune reactions) may be helpful in some cats but is expensive and generally does not provide much increase in life beyond the use of steroids. Polyprenyl immunostimulant has been used to treat cats with the ‘dry’ form of FIP (it is of no benefit in the ‘wet’ form of FIP), but data to supports its use is limited.

Recently anti-viral drugs have been trialled in cats with FIP with some success. However, at this time (March 2019) these trials are closed and this medication is not available anywhere in the world.

How can I stop my other cats catching the disease?

The causative virus (FCoV) is spread in saliva, phlegm and in faeces. Most cats that contract the virus are able to clear infection. Some of these cats may continue to carry the virus and are a source of infection for other cats. A cat with suspected FIP should be kept indoors in a separate room, to avoid direct contact with other cats. It should have its own feeding bowl and litter tray and these must be cleaned every few days.

The virus only survives a couple of months outside the cat and it can be killed using a dilute solution of household bleach (about five tablespoons of bleach in a gallon of water). Use this to clean the feeding bowls, litter trays etc. and to wipe down room surfaces. Remember that this is caustic – so wear gloves, skin and eye protection. Ensure that surfaces are rinsed clean before allowing the cat to contact them.

Can my cat be vaccinated against FIP?

An FIP vaccine has been developed in the US and some parts of Europe. It is not available in the UK. Vets disagree on how effective it is in preventing FIP, and it is not currently recommended by Feline Specialists in either America or Europe.