Bovine spongiform encephalopathy: a neuropathological perspective.

The occurrence of bovine spongiform encephalopathy (BSE), recognition that it is a new scrapie-like disease epidemic in domestic cattle in the United Kingdom and concern of a remote zoonotic potential has, in four years, produced a plethora of documented information. While much of this information has been communicated outwith the scientific literature, this review attempts to summarise, from a neuropathological viewpoint, the main findings to emerge. The initial studies established the nosological homology of BSE with the subacute spongiform encephalopathies or "prion" diseases of animals and man. Epidemiological data are consistent with an extended common source epidemic originating from an abrupt change, commencing in 1981-82, in the exposure of domestic cattle to a scrapie-like agent in meat and bone meal incorporated into commercial animal feedstuffs. It is currently proposed that the method of production of meat and bone meal has contributed vital factors to the change in exposure. Invariability of the distribution pattern of vacuolar pathology in the natural disease and on primary transmission to cattle suggests a uniformity of the pathogenesis of BSE. Studies in mice suggest uniformity also of the biological properties of different BSE isolates but indicate that the properties differ from those of sheep scrapie isolates. Human health risks, although perceived to be negligible, have been addressed by various strategies including statutory measures and long term monitoring.