Transmissible spongiform encephalopathies
in animals and humans are caused by an
unconventional virus or prion. These
conditions include scrapie in sheep, bovine
spongiform encephalopathy in cattle and Creutzfeldt Jacob
disease in humans. It is commonly
accepted that BSE was first caused in the
United Kingdom when cattle were fed
carcass meal from scrapie-infected sheep. It
is also accepted that humans contracted the
non-classic form of CJD after consuming
cattle meat, in particular nerve tissue.