Scrapie is a fatal, egenerative disease that affects the nervous systems of sheep and goats. It is one of several transmissible spongiform encephalopathies (TSEs), which are related to bovine spongiform encephalopathy (BSE or "mad cow disease") and chronic wasting disease of deer. Like other spongiform encephalopathies, scrapie is caused by a prion. Scrapie has been known since the 18th century (1732) and does not appear to be transmittable to humans.