Bovine spongiform encephalopathy (BSE), commonly known as "mad cow disease," is a fatal disease that strikes the nervous system of cattle. Currently, no vaccine or treatment exists to treat BSE, and affected animals display a variety of neurological symptoms before they die (think of television reports showing cows having trouble standing up).
An animal with outward symptoms of BSE may survive for 2 weeks to 6 months, though it may have carried the disease for up to 8 years. BSE has an incubation period (the time between infection and development of symptoms) ranging from 30 months to 8 years, which is a long time for a disease to remain undetected.
BSE is a disease that only cows develop; however, it is related to a "brain-wasting" disease that affects humans, called Creutzfeldt-Jakob disease (CJD). CJD occurs due to a spontaneous genetic mutation that occurs in one in every million individuals. In 1996, another form of CJD was identified and has since been named "variant CJD" (vCJD). This variant form of CJD has been linked to the consumption of meat products infected with BSE.