No wonder Europe is terrified of bovine spongiform encephalopathy (BSE), better known as mad-cow disease. The illness started attacking British cattle in the mid-1980s. Then it crossed the species barrier; a human version of BSE has killed more than 80 Britons since 1995. Then it leaped across the Irish Sea and the English Channel, afflicting cows in 12 European nations. Last week Italy confirmed its first cases. Late last year, it hit Spain and Germany. Earlier this month, the German ministers of health and agriculture resigned in disgrace when their assurances that German beef was safe proved false. A handful of human deaths have been reported in France and Ireland--so far.
And now the U.S. is beginning to panic as well. Last week a U.S. Food and Drug Administration advisory panel recommended that anyone who had lived in France, Portugal or Ireland for a total of 10 years since 1980 be prohibited from donating blood (rules adopted last year excluded anyone who had lived in Britain for six months between 1980 and 1996). The American Red Cross, meanwhile, urged the FDA to apply the six-month rule to all of Western Europe--which would cut the supply of donors 5% or so--even though there's no evidence that the disease can be transmitted through blood in the first place.
Is all of this really necessary? Probably not, say experts. For while the British were taken by surprise by the appearance of a new disease, and other European nations were slow to adopt strict precautions, Americans have, by a combination of luck and early preventive action, dodged this deadly bullet.
The first bit of luck came in the 1950s, when the U.S. banned imports of British goats and sheep. Reason: a flock of British sheep had a degenerative brain disease called scrapie. Scrapie is harmless to humans, it turns out, and generally harmless to cattle as well, even when infected sheep tissues are injected directly into a cow's brain. But scientists believe some sheep carcasses, ground up to add to British cattle feed, carried an unusual form of the disease that did manage to infect cows. That variant, renamed BSE, began to show up in British herds in the 1980s, eventually afflicting nearly 200,000 animals.
By 1995, the first cases appeared in humans; the disease was re-christened yet again as a "new variant Creutzfeldt-Jakob disease" (VCJD) because it resembled an existing illness whose cause is unknown. The new disease was probably caused by eating beef containing brain or spinal tissue from mad cows, since human cases invariably turned up in countries with BSE problems.
But the U.S. imported fewer than 500 cows from the British Isles in the 1980s, of which just 32 entered the food chain. By the end of the decade, the U.S. had prohibited the import of live cows and sheep from Britain, along with many animal products and rendered animal proteins.
As a result, not one cow in America has so far been found to have BSE--and the U.S. Department of Agriculture has an aggressive plan to find, quarantine and destroy any if they appear. "Even if you do eat beef from an infected cow," says Michael Scott, a molecular biologist at the University of California, San Francisco, who has studied the disease in cattle and humans, "you have a very low risk of contracting VCJD."
No one is quite sure why. That's because much about the disease remains a mystery. Scientists like Scott are convinced it's carried not by a virus or a bacterium but by a rogue protein called a prion (see diagram). Unfortunately, prions can't be detected in a blood or tissue test; only their brain-riddling effect is apparent, and then usually just on autopsy. They can't be destroyed, moreover, by cooking or even by radiation. So if the BSE prion somehow did manage to enter the U.S. food supply, it might cause at least a few deaths before anyone could stop it.
With the U.S. government's stringent import regulations, the BSE prion is unlikely to come from Europe, even without the new blood-donation rules (which, given supply shortages, many experts suspect will end up costing more lives than they could possibly save). Direct transmission from one person to another is considered highly unlikely.