Feline Infectious Peritonitis (FIP) is a common disease in cats caused by Feline Coronavirus. The infection normally causes a mild intestinal disease, which may either be asymptomatic or cause temporary diarrhoea.
In general, cats don’t usually catch the mutated form of the virus directly. FECV is the form that is transmitted between animals, usually through the saliva or faeces of an infected cat, either via grooming or contact with contaminated objects such as feeding bowls, litter trays or bedding. Once FECV infection has become established, mutated forms (FIPV) may arise during viral replication.
Cats that live in close proximity to each other, especially in catteries, are much more likely to be exposed to FECV, and are also more likely to go on to develop FIP because there is simply more virus replicating in their systems. Certain genetic lines of cats are also more susceptible. Typically, young cats from about 6-months to 2-years of age tend to get FIP, although cats of any age can contract the disease.
In some cats FECV can mutate to a form called Feline Infectious Peritonitis Virus (FIPV), which can infect certain white blood cells. The virus then spreads throughout different organs within these white blood cells.
Normally, the body mounts an immune response to eliminate viral infections. Some cats can fight this mutated form before signs become apparent. The immune systems of other cats seems unable to kill the virus and it is, in fact, this inflammatory reaction that actually creates damage to the body’s tissues and causes the signs seen with FIP.
FIP exists in two clinical forms. The ‘wet’ form is characterised by fluid accumulation in the abdomen and/or the chest, and is the most common form of the disease. The ‘dry’ form is caused by inflammation in various body systems. Many cats have a combination of the two forms. The disease, particularly the wet form, may progress over a few days, or it may wax and wane for many weeks.
Typical signs of the wet form are swelling of the belly and/or breathing difficulties, as the respective body cavities fill with fluid.
Signs of the dry form are weight loss, anorexia, fever and depression.
Depending on which organ systems are involved other signs can include jaundice, vomiting and diarrhoea, dehydration, excessive drinking and urination, inflammation in the eyes, or neurological signs.
How is FIP diagnosed?
The diagnosis of wet form FIP is fairly straightforward because of the classic yellow sticky fluid that accumulates.
The dry form, however, can mimic many other diseases and can be challenging to diagnose.
Normal blood tests may show increased protein in the blood, or changes to white cell counts, which are suggestive of FIP, but these can also be seen i many other inflammatory diseases.
There are various treatments for FIP which can be attempted but, to date, none have been conclusively effective in treating the disease. Currently, FIP remains an ultimately fatal condition. There is also no effective vaccine available to prevent FIP.