Bovine spongiform encephalopathy (BSE), more commonly known as mad cow disease, first emerged in Great Britain in the late 70s. However, it wasn't identified until 1986. By the mid-90s, BSE was infecting thousands of cows annually in Britain. The disease was spread through animal feed, which contained animal byproducts.
In 1996, the E.U. banned exports of British beef and feed, and millions of British cows were destroyed. Around the same time, scientists postulated that BSE could be spread to humans by eating infected beef. The human form of BSE--a new variant Creutzfeldt-Jakob disease (vCJD)--is a brain-wasting illness that ultimately kills its victim. There is no cure for vCJD.