New variant Creutzfeldt-Jakob disease and bovine spongiform encephalopathy.

New variant Creutzfeldt-Jakob disease (CJD) and bovine spongiform encephalopathy (BSE) are invariably fatal, subacute degenerative diseases of the brain that are classified as transmissible spongiform encephalopathies. BSE was first diagnosed in 1986 as part of an ongoing epizootic in the United Kingdom that was amplified by the feeding of rendered bovine meat-and-bone meal to young calves. As of June 1997, a total of 17 cases of new variant CJD have been reported among residents of the United Kingdom, an increase of seven cases since March 1996, when concern was first expressed about the possible emergence of new variant CJD as a novel epidemic caused by the spread of BSE to humans. Accumulating experimental and epidemiologic data support this concern and have led the CDC to support the Food and Drug Administration's efforts to modify the protein content of ruminant feed in the United States as a prudent measure to protect the health of animals and the public.