Mad cow’s small impact explained?

A recent study by neuropathologist Laura Manuelidis, M.D., professor of surgery, and colleagues in Japan may offer the beginnings of a solution to an epidemiological puzzle.

In 1996, during an epidemic of bovine spongiform encephalopathy (BSE), or mad cow disease, in British cattle, some epidemiologists predicted that up to 100,000 people could contract variant Creutzfeldt-Jakob disease (vCJD), a rapidly progressing, invariably fatal neurodegenerative condition, from BSE-infected beef.

But that nightmarish scenario hasn’t yet come to pass: almost 10 years later only 151 cases of vCJD have been verified.

Manuelidis and her team reported in the October 21 issue of Science that when neuronal cell cultures were infected with either a weak or sporadic form of CJD or with agents that cause sheep scrapie, a disease similar to CJD, the cultures resisted infection by a more virulent strain of CJD agent.

The team suggests that exposure to less virulent strains of CJD may protect people against the newly evolved bovine agent.