Recently an experimental test has been developed to test asymptomatic animals for presence of the agent. Transmissible mink encephalopathy was first observed in the United States in 1947 is a rare disease of farm raised mink. Since then, it has been reported in the Canada, Finland, Germany, and the former Soviet Union. Clinical signs of the disease are changes in behavior, incoordination, jerking of hind limbs, circling, compulsive chewing, and clenching of the teeth. Cases were seen at several mink ranches in Wisconsin, Minnesota, and Idaho.
Epidemiological studies suggest that contaminated feed is a likely source.
Since 1993 the USDA Animal Plant Health Inspection Service has examined the brains of over 8,400 downer cattle for BSE or other TSE and has not found a single case. Since 1981, less than 200 cases have been documented. Cases have occurred in both free ranging animals as well as in farmed elk and other confined herds of deer or elk. The disease is characterized by chronic weight loss leading to death. Behavioral changes such as decreased interactions with other animals, listlessness, repetitive walking in set patterns, and in elk, hyperexcitability and nervousness are seen also.