Feline infectious peritonitis (FIP) is a viral disease of cats caused by certain strains of a virus called the feline coronavirus. FIP appears to be more common in cats that live in multi-cat households, shelters, or catteries, and cats that are stressed due to re-homing, have recently had surgery, or have concurrent infections may also be more susceptible to developing FIP. Genetic factors are also thought to contribute to the development of FIP.

There are two major forms of FIP: an effusive, or “wet” form and a noneffusive, or “dry” form. Regardless of which form they ultimately progress to develop, cats infected with FIPV usually first develop nonspecific signs of disease such as loss of appetite, weight loss, depression, and fever. The signs of effusive form of FIP usually develop and progress relatively rapidly and include development of the above-mentioned non-specific signs combined with the accumulation of fluid in body cavities, including the abdomen and the thorax (chest cavity) . Affected cats may develop a pot-bellied appearance due to fluid accumulation in the abdomen, and if the fluid accumulation is excessive, it may become difficult for a cat to breathe normally. The dry form of FIP causes infection and inflammatory lesions around the blood vessels in a cat’s body, which can affect the brain, liver, kidneys, lungs, and skin. This form often causes the cat to have seizures and move in an abnormal or uncoordinated way. In some cases, cats will also have excessive thirst and urination, vomiting, weight loss, and jaundice.

The diagnosis of FIP can be challenging to make, especially in cats without fluid build-up, and may require a combination of multiple types of tests. A vaccine is available to help prevent FIP, but it will not prevent infection in cats that have already been exposed to the virus[[4]](https://www.merckvetmanual.com/cat-owners/disorders-affecting-multiple-body-systems-of-cats/feline...