Feline spongiform encephalopathy (FSE) is a neurodegenerative disease, caused by a prion, that affects members of the cat family. Once the clinical signs appear, this disease is invariably fatal. FSE is caused by the same agent that is responsible for bovine spongiform encephalopathy (BSE) in cattle. BSE was first reported in the 1980s, when it caused an explosive epidemic among cattle in the U.K. This disease eventually spread to many other countries. FSE was first reported in 1990, and was apparently transmitted to individual cats in BSE-contaminated food. As the BSE epidemic has declined, and controls have been placed on feeding high-risk bovine tissues to animals, FSE has become increasingly rare. However, this disease has a long incubation period and occasional cases may still occur in housecats and zoo animals.