ABSTRACT
Transmissible spongiform encephalopathies (TSEs) of humans and animals are relatively rare neurodegenerative diseases (1-4). Scrapie, a TSE in sheep, is the oldest-known member of this family and was first described over 200 years ago (5). Another TSE found in the United States and Canada, chronic wasting disease, has been described in mule deer (6) and then later in Rocky Mountain elk (7). The recent outbreak of a TSE in cattle, bovine spongiform encephalopathy (BSE), in the United Kingdom has caused considerable concern because of the transmission to humans (8,9).
