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Mad-Cow Disease in Cattle and Human Beings

Bovine spongiform encephalopathy provides a case study in how to manage risks while still learning the facts

Paul Brown

Figure 1. Mad-cow disease . . .Click to Enlarge Image

In December 2003, the U.S. Department of Agriculture discovered a case of bovine spongiform encephalopathy (BSE), often called mad-cow disease, in a dairy cow from Washington state. The news was more than a little disturbing to the American cattle industry. The mad-cow scare had previously devastated the cattle business in the few countries where BSE had been reported, especially Great Britain and Canada. The Canadian cattle industry has yet to recover from the discovery of BSE in a single cow on an Alberta farm in May of last year. A 400-kilogram cow that used to fetch 500 Canadian dollars on the open market now sells for as little as 79 Canadian cents—less than the price of a fast-food burger.

The economic fallout is, of course, a consequence of the discovery in 1996 that mad-cow disease could cross the species barrier to inflict human beings with variant Creutzfeldt-Jakob disease (vCJD). This disease is characterized by a progression of psychiatric and neurological symptoms that culminate in death, usually a year or two after the onset of the first indications of illness. As of May 2000, a total of 155 cases of vCJD had been identified: 144 in Great Britain (where the outbreak began), 6 in France, 1 in Ireland, and 1 in Italy. Additional single victims in Hong Kong, Canada and the U.S. were infected in the U.K., where they had been residing during the years of peak risk, in the late 1980s or early 1990s. The extraordinary commercial and public-health consequences of BSE, as well as the near-global distribution of products derived from cattle, have generated a considerable amount of attention from industry, government and the general public. As a result, there is a daunting volume of information—not all of it reliable—surrounding the nature of mad-cow disease. I will here attempt to distill the essence of what we know about the disease, especially with respect to its consequences for human and animal welfare in North America.

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