Mad Cow Disease

The Death Toll Rises

In 1995, Stephen Churchill, the 19-year-old son of a fire inspector, became the first Briton to die of variant Creutzfeldt-Jakob Disease (vCJD, the form of CJD that has been linked to mad cow disease). The first signs were a gradual deterioration of Churchill’s college grades, accompanied by depression and dizziness, followed by a loss of coordination and balance. "About four months before he died, he started to stagger," says his mother, Dorothy Churchill. "It brought back memories of seeing the cows we had seen on the news. I mentioned it to somebody, and then I dismissed it because it seemed a ridiculous idea."

Stephen Churchill had visited his aunt’s farm every year for eight years, coming into contact with cows and drinking unpasteurized milk. Only a few months after Churchill died, 29-year-old Michelle Bowen, who had worked at a butcher’s shop when she was a teenager, also died from vCJD.

Illustration by Todd M. Coe

In the five years since the British government concluded that people were dying from exposure to mad cow disease, fewer than 100 people have died from vCJD. This statistic may not seem terribly alarming, but public health officials familiar with the long incubation period of this class of diseases are far from complacent. According to an analysis published in the January-February 2001 issue of the Centers for Disease Control and Prevention’s Emerging Infectious Diseases, which was written by leading researchers from both the United Kingdom and the U.S., the death toll may eventually surpass 100,000.

"Much of the lingering uncertainty about the extent of the vCJD outbreak is attributable to the fact that the incubation period of vCJD is unknown," say the researchers, who include Paul Brown of the U.S. National Institutes of Health, Robert Will of England’s National Creutzfeldt-Jakob Disease Surveillance Unit and Linda Detwiler of the USDA. "If the average incubation period is 10 to 15 years," they say, "the earliest patients with vCJD would have been infected in the early 1980s, when BSE [Bovine Spongiform Encephalopathy] was still silently incubating in small but increasing numbers of cattle. If, however, the average incubation period of vCJD is five to 10 years, the earliest human infections would have begun in the mid- to late 1980s, when exposure to BSE was maximal. Depending on assumptions about the incubation period and other variables, the total extent of the outbreak could range from fewer than one hundred to hundreds of thousands of cases."

This broad range of uncertainty has actually narrowed since 1996, when scientists first discovered that mad cow disease had jumped species and was beginning to kill people. Back then, scientists estimated that the eventual human death toll would be somewhere between a few dozen and a few million. By tracking the rate of increase of the epidemic over the course of the past five years, they have been able to narrow the range significantly, but it will still be several years before anyone has an accurate estimate of the number of people infected.