Feline infectious peritonitis (FIP) is caused by feline coronavirus (FCoV). The Winn Foundation funded a survey of 129 cats naturally exposed to FCoV in the UK (1996-1999) and 18 lifelong carrier cats were identified. Four of these carrier cats died, one with FIP, and a 5th cat has recently had a tumor removed from her large intestine. In this project pathological samples from these cats will be examined for evidence of virus, to elucidate exactly where FCoV persists in healthy carrier cats, compared with cats that develop FIP. This will give us a greater understanding of how FIP develops and how the virus causes a persistent infection. The latter is important because carrier cats are a likely source of FCoV for other cats in the population and once we understand how the virus persists it might be possible to find a way to eliminate it from carrier cats in a way that does not endanger the carriers themselves.