Feline Infectious Peritonitis Study Guide

Overview and Clinical Importance

Feline infectious peritonitis (FIP) is one of the most important infectious diseases and causes of death in cats, particularly in young cats under 2 years of age. FIP develops when a ubiquitous feline enteric coronavirus (FECV) undergoes mutation within an infected cat, transforming into the virulent feline infectious peritonitis virus (FIPV). This mutation enables the virus to infect macrophages and disseminate systemically, triggering a severe immune-mediated pyogranulomatous vasculitis.

Approximately 5-12% of cats infected with FCoV will develop clinical FIP. The disease was historically considered universally fatal; however, recent advances in antiviral therapy with nucleoside analogues (GS-441524, remdesivir) have revolutionized treatment, with survival rates now exceeding 80-90% in treated cats.

Etiology and Pathogenesis

The Feline Coronavirus

Feline coronavirus (FCoV) is an enveloped, positive-sense, single-stranded RNA virus belonging to the order Nidovirales, family Coronaviridae, genus Alphacoronavirus. Two biotypes exist: the avirulent feline enteric coronavirus (FECV) and the virulent feline infectious peritonitis virus (FIPV). These biotypes cannot be distinguished morphologically or serologically.