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, more than 180,000 cattle were infected and 4.4 million slaughtered during the eradication program.