The outbreak of bovine spongiform encephalopathy (BSE) or "mad cow disease" in the United Kingdom and continental Europe continues to concern beef and dairy producers and the general public in the United States. This concern has increased recently because of the continued spread of the disease on the European continent and the development of a similar disease that has appeared in people, mostly in the U.K. The new disease known as variant Creutzfeldt-Jakob disease (vCJD) appears to be more closely related to BSE in its pathology than to traditional CJD. It is therefore assumed that vCJD has crossed the species barrier from cattle to Man.

BSE and CJD are prion diseases, a group of rapidly progressive, fatal, untreatable neurodegenerative syndromes characterized by the accumulation in the brain of a protease-resistant protein that is...