FEATURE ARTICLE
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
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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