Transmissible mink encephalopathy (TME) is a progressive and fatal neurodegenerative disease that affects ranched mink (Neovison (Mustela) vison). Most or all of the adult animals on a ranch may be affected, and once an animal becomes symptomatic, death is inevitable. This disease is still poorly understood. It is very rare, with only a few outbreaks reported in the U.S. and other countries. Outbreaks seem to result from feeding contaminated food containing prions to mink; however, the origin of these prions is unknown. Recent evidence suggests they might be an atypical variant of the bovine spongiform encephalopathy (BSE) agent.