The recent epidemic of Mad Cow disease, bovine spongiform encephalopathy, along with the recent death of a Canadian man by Creutzfeld-Jacob disease, has brought the discussion of prions back to the forefront of medical research. Prions, or spongiform encephalopathies, are small proteinacious infectious particles that resist inactivation by procedures which affect nucleic acids. It is a near certainty that prions do not have a nucleic acid genome though it is still disputed. The discovery that prions, a protein, can be infectious without any connection to a virus or nucleic acid was quite a shock.

Prion diseases are found in most mammals, including humans. These diseases include scrapie, in sheep, TME, transmissible mink encephalopathy, BSE, bovine spongiform encephalopathy, in cows as well as a few in humans; kuru, alpers syndrome, and the most troubling, Creutzfeld-Jacob disease, CJD.

The first prion disease discovered was scrapie, in sheep. Scrapie has...