In cats that develop FIP, the first signs of illness may be hard to spot. Low energy, lethargy, reduced eating or not eating, weight loss, and fluctuating fever are commonly reported clinical signs.  

After several days to a few weeks, other symptoms typically begin to occur. FIP can be divided into ‘wet’ and ‘dry’ forms, but cats are likely to have both at different times or a mixture of both. One of the difficulties in diagnosing FIP is that the signs are not specific to FIP, with other illnesses causing similar signs.    

WET form of FIP: In this form, there is an accumulation of fluid within the belly and/or the chest. This can cause a swollen belly and breathing difficulties. The fluid accumulates because of damage to, and inflammation of, blood vessels, which causes fluid to leak from the blood into the belly or chest. The fluid tends to be thick and bright yellow in colour and contains a lot of protein. However, other diseases (including some liver diseases and cancers) can also cause a similar fluid accumulation.   

DRY form of FIP: FIP can affect any organ of the body, so other forms of FIP without fluid accumulation (often called ‘dry’ FIP) can occur. The signs will vary depending on which organ is affected. This inflammation affects the eyes with inflammation and cloudiness, and the brain with neurological signs such as loss of balance and tremors or fits but can also affect almost any tissues in the body, including the liver, kidneys, intestines, lungs, and skin.  

Once the disease develops, without treatment, most cats deteriorate rapidly, although some remain normal for several weeks.    

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 to have strange behaviour again. 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. 

As there are no signs specific to FIP, and no simple blood test to confirm a diagnosis, it is a difficult disease to diagnose.  

Your vet may perform several routine tests including blood tests, an eye exam, and imaging (x-rays and ultrasound) of the chest and belly. If any fluid has developed, taking a sample, and testing it can help with a diagnosis. Your vet may also want to take samples of any abnormal organs – for example, a needle sample of the liver, kidneys, or glands in the belly.  Occasionally, a surgical procedure is needed to remove a sample of tissue for testing.    

Treatment for FIP can vary in length. Some cats will need treatment for several days while others will need treatment for several months. Sadly, in many cases, by the time symptoms of FIP are present, the disease is very advanced, and treatment may not be possible.  

Your vet will try to stabilise your pet, which could involve fluids via a drip, nutritional support and medication. Some anti-viral drugs have been developed and are licensed in the UK, but these can be expensive, and your cat may need this medication for many months. In critically ill cats or very advanced cases of FIP, your vet might recommend putting your cat to sleep to avoid their suffering.  

A commercial FIP vaccine has been developed, however this vaccine cannot be used in kittens under 16 weeks of age, and many will already be exposed to feline coronavirus before this age. It is not currently available in the UK.  

Large groups of cats, such as those in breeding catteries, rescue centres or households with lots of cats are most at risk. But there are some sensible precautions you can take to help protect your cat from infectious diseases like feline coronavirus and reduce the risk of FIP:  

• Avoid keeping cats in large groups (ideally no more than four cats, although most cats are happiest when they're the only cat)  

• Avoid getting a cat from a home or breeder who keeps large groups of cats or multiple litters of kittens at once  

• Have at least one litter box for every two cats  

• Keep litter trays far away from food and water bowls  

• Clean your cat's food, water bowl, litter tray and the surrounding area daily  

• Keep stress in your cat to a minimum  

• Keep up with their health checks and healthcare needs  

   
Treatment of FIP is more possible than ever before, but with all treatment decisions, it is important to consider the time and cost implications. Anti-viral treatment has significant associated costs, and regular checks are required for several months including repeat blood tests and scans to monitor response. In cases where anti-viral treatment is not possible or appropriate, sadly euthanasia is recommended as the condition is otherwise incurable and patients are often very unwell. If FIP is suspected (or diagnosed) in your cat, we appreciate this can be a challenging time. Your vet will be happy to discuss the implications for you and your cat, and for any diagnostic and treatment decisions you need to make.