Transmissible mink encephalopathy (TME) is a rare, progressive, and fatal neurologic disease of mink caused by prion infection. It has been associated with 60%–90% mortality on a given farm. It is thought to be transmitted orally. The incubation period is 6–12 months. Infected mink may initially have problems swallowing or eating, and they later develop hyperexcitability and compulsive self-biting. Mink may scatter feces in their pen, carry their tails up over their backs, and, late in the course of the disease, may become uncoordinated and somnolent. Death typically ensues within 2–8 weeks after onset of clinical signs. There are no gross lesions; histologic lesions of the brain include neuronal vacuolation and spongiform encephalopathy of the gray matter. Definitive diagnosis is made via identification of prions by immunohistochemistry evaluation. No antemortem diagnostic test is available.
The TME prion closely resembles an atypical bovine spongiform encephalopathy (BSE) prion and is thought to be associated with feeding mink prion-contaminated meat or offal, likely from nonambulatory or dead cattle. Cooking or rendering does not destroy the infectious particles. Disinfection of potentially contaminated surfaces is difficult because prions are resistant to ultraviolet light and most disinfectants. Organic debris must be removed prior to decontamination with 1–2N sodium hydroxide or sodium hypochlorite (20,000 ppm Cl) solutions, and surfaces should ideally be exposed to disinfectants for several hours or overnight. There is no vaccine or treatment available. In some countries, TME is a reportable disease.