What is FIP?

Feline infectious peritonitis (FIP) is an important viral disease caused by certain strains of feline coronavirus.  Most strains of feline coronavirus are found in the gut and do not cause serious disease. However, in some cases the coronavirus mutates and is able to spread throughout the body causing more severe disease called FIP. There are two forms of FIP – ‘wet’ and ‘dry’ – and each cause different clinical signs that include fluid accumulation in the abdomen or chest, and inflammation in various organs around the body. FIP is most common in cats that are under two years of age.

Importantly, the coronaviruses that affect cats are different to the coronavirus that causes Covid-19 in people. The coronavirus that causes FIP in cats cannot infect humans.

How is FIP spread by cats?

Coronavirus infections in cats are very common, and most are self-limiting and not serious, just causing some mild diarrhoea or no symptoms at all. It is shed in the faeces and infects other cats through ingestion (e.g. licking and grooming).

Whether or not the cat will develop FIP depends on both the coronavirus - whether it mutates and is then able to infect white blood cells - and also the immune response of the cat. Some can clear this mutated virus and do not develop FIP, while others produce a less effective immune response and so go on to develop signs of FIP.

What are the symptoms of FIP in cats?

The clinical signs of FIP are variable and depend on the type of FIP. Early signs of both ‘wet’ and ‘dry’ forms normally include fever, lethargy and loss of appetite.

Clinical signs of ‘wet’ (effusive) FIP include:

• Abdominal distension due to fluid accumulation
• Breathing difficulties due to fluid accumulation in the chest

Clinical signs of ‘dry’ (non-effusive) FIP include:

• Weight loss
• Problems with the eyes
• Balance problems
• Jaundice

How is FIP in cats diagnosed?

The vet may be suspicious of FIP based on the clinical history and physical examination, but it can be difficult to definitively diagnose as no single test is available. Diagnosis is normally based on a combination of compatible clinical signs, blood tests, fluid analysis in the case of ‘wet’ FIP and biopsies. Sadly, the disease is often only diagnosed for certain at post-mortem.

Can FIP in cats be treated?

Unfortunately not, FIP is incurable and most cats are euthanised soon after diagnosis.

Can I prevent FIP in cats?

No. There is currently no coronavirus or FIP vaccination available in the UK and there is no way of knowing whether a cat infected with a feline coronavirus will go on to develop FIP. Most will clear the infection and not develop FIP, but reducing stress in the environment and household can help to increase the chances of this happening. It can also help to keep the litter tray clean and to keep food and water bowls away from the litter tray.