Such is the fear of mad cow disease, known scientifically as bovine spongiform encephalopathy, or BSE, for the way it leaves a cow's brain full of microscopic, spongelike holes. The curious ailment that has bedeviled English cattle and killed more than 80 Britons, and that has moved into continental Europe and killed a few more people, remains largely a puzzle. But there's stuff we don't know about the disease. For instance, we don't know its origin. Nor can they pinpoint with certainty what can stop the terror at the country's borders.
Most researchers think humans contract a variation of the disease by eating the same thing.
Yet that's still only a well-educated guess. The disease is linked to an altered or abnormal form of the prion protein usually found in animals. The prions work their way into the central nervous system before riddling the brain with holes. It's unclear what causes the unusual and unwelcome prions to show up. It could start out as an unpredictable and spontaneous activity in one animal that is passed on to others.