Feline Infectious Peritonitis (FIP) is a viral disease caused by a rare mutation of a very common, and not serious, virus called Feline Coronavirus.
In infected cats, the virus spreads throughout the body and can cause a wide range of different signs including peritonitis with the accumulation of fluid in the abdomen, but in other cats, fluid may accumulate in the chest cavity.
In others, the virus may cause inflammation affecting the brain, eyes, liver, kidneys or elsewhere.
The disease is recognised as either ‘Wet’ or ‘Dry’ and some cats will have one, but many have both.
Wet FIP is when there’s an accumulation of fluid in the abdominal cavity and/or chest cavity. The cause of this is damage to, and inflammation of, blood cells which result in fluid leaking from blood into the abdomen or chest.
Dry FIP predominantly causes chronic inflammatory lesions to develop around blood vessels in many organs and other sites in the body. The inflammation affects the eyes in around 30% of cases and the brain in around 30% but can also affect almost any tissues in the body including liver, kidneys, lungs and skin. Signs include neurological disease and bleeding of the eyes.
When signs appear, they tend to get progressively worse over time and in most cases the time course for disease is rapid, with cats deteriorating to the point that euthanasia is usually required within a matter of days or weeks.
FIP can occur at any age but around 80% of cases diagnosed are in cats less than 2 years old, with many cases seen in kittens around 4 – 12 months old.
Sadly, once signs of FIP develop, it is generally an incurable and fatal disease. The best you can hope for is to relieve the symptoms to improve their quality of life, but in most cases the cat is euthanised to avoid suffering.