Creutzfeldt-Jakob disease (CJD) is a brain wasting disease. The best evidence is that it is caused by a malformed protein that interferes with the repair and operation of existing brain tissue. It appears to be related to Mad Cow disease and scrapie, both of which cause similar symptoms in cows and sheep respectively. Brains of Creutzfeldt patients on autopsy are riddled with holes. Also see Kuru, a disease endemic to cannibalistic headhunters that appears to be transmitted by the same mechanism and has similar symptoms, as well as the same prognosis.