Blue Cross blog

Feline infectious peritonitis is a rare but fatal disease affecting cats. Blue Cross chief vet Caroline Reay has more information on the condition and what causes it…

Microbes are everywhere, yet only some people and pets get sick whilst others stay healthy. The reasons have eluded medics for centuries.

Sometimes it’s actually the body’s attempts to stave off infection that produces life-threatening disease. This is what happens when a cat develops the nasty illness called feline infectious peritonitis (FIP).

FIP is caused by a common virus, called feline coronavirus, which usually causes a mild illness such as a sniffle or diarrhoea.

But sometimes it causes a serious and incurable condition from which, sadly, the cat doesn’t recover.

Causes of FIP

We don’t know why this happens – possibly coronaviruses mutate during infection to a nastier dangerous form.

There’s some genetic susceptibility (it’s more common in pedigree cats) and stress seems to be a factor. Stress is often caused by other cats so it’s more common when lots of cats live together.

Signs of FIP

Signs really vary because they are the consequence of immune reactions which can happen anywhere in the body, but they include fits, jaundice, staggering or a swollen belly filled with fluid to name a few.

Diagnosing FIP

Diagnosis is difficult because many cats are infected with relatively harmless coronaviruses which causes antibodies to develop.

Where coronavirus escalates to FIP this antibody production seems to surge out of control (but not always).

Detecting antibodies may just mean that the cat has had the “normal” coronavirus at some point. It doesn’t necessarily mean FIP.

For diagnosis vets use a checklist of symptoms and blood changes with antibody levels to provide evidence of exposure. But detectable antibodies do not mean your cat has FIP.

You can buy kittens which are free from coronaviruses. Provided they are tested at over 10 weeks of age with a good quality test, then antibody negative kittens are infection-free.

But they are still vulnerable to infection, so if you are going to let your cat outdoors testing may not be worthwhile.

FIP is relatively rare, only occurring in less than one per cent of cats seen by vets.

If you are worried or are thinking of buying a pedigree kitten, vet Dr Diane Addie has an excellent website on FIP and it’s well worth taking a look.

Other sources include the Feline Advisory Bureau, Winn Feline Foundation and Cornell Cat Health Center.