Abstract
Introduction. Creutzfeldt-Jakob disease (CJD) belongs to a group of human and animal diseases, distinguished from each other by differences in their clinical and neuropathological presentation or aetiology, but known collectively as the prion diseases. Prion diseases are unique amongst transmissible diseases in that the transmissible agent does not appear to contain any nucleic acid and the only protein known to be associated with infectivity is host-coded. Prion disease is endemic in certain species, notably humans and sheep. It has also appeared in epidemic form in humans: for example, amongst tribal peoples of Papua New Guinea, where the disease is known as kuru, and in Western societies as a consequence of iatrogenic misadventure. Epidemic prion disease also occurs in animals: for example, in cattle [as the current epidemic of BSE (bovine spongiform encephalopathy) in Britain (Wells & Wilesmith, 1995)] and in farmed mink (Marsh, 1992).