Creutzfeldt-Jakob disease (CJD) is a rare, degenerative brain disorder. Symptoms usually start around age 60. Memory problems, behavior changes, vision problems, and poor muscle coordination progress quickly to dementia, coma, and death. Most patients die within a year.
The three main categories of CJD are
Sporadic CJD, which occurs for no known reason
Hereditary CJD, which runs in families
Acquired CJD, which occurs from contact with infected tissue, usually during a medical procedure
Cattle can get a disease related to CJD called bovine spongiform encephalopathy (BSE) or "mad cow disease." There is concern that people can get a variant of CJD from eating beef from an infected animal, but there is no direct proof to support this.
NIH: National Institute of Neurological Disorders and Stroke