Bovine spongiform encephalopathy (BSE), commonly known as mad cow disease, is a fatal neurodegenerative disease (encephalopathy) in cattle that causes a spongy degeneration of the brain and spinal cord. BSE has a long incubation period, about 2.5 to 8 years, usually affecting adult cattle at a peak age onset of four to five years, all breeds being equally susceptible. BSE is caused by a misfolded protein—a prion. In the United Kingdom, the country worst affected by an epidemic in 1986–1998, more than 180,000 cattle were infected and 4.4 million slaughtered during the eradication program. The disease...