Mad Cow Disease

prion

prion (prē´ŏn), abnormal form of a protein found in mammals, believed to cause a group of diseases known as prion diseases or transmissible spongiform encephalopathies. Well-known prion diseases are Creutzfeldt-Jakob disease (CJD) and kuru in humans, scrapie in sheep, bovine spongiform encephalopathy (BSE), also called "mad cow disease," in cattle, and chronic wasting disease in deer and elk (wapiti). There is no effective treatment for any prion disease.

Sometimes taking more than 30 years to display symptoms, the diseases slowly attack brain tissue, often leaving spongelike holes. They are characterized by accumulations of prions, abnormal forms of a protein called prion protein. Unlike viruses or bacteria, prions contain no genetic material and have no known ability to reproduce themselves. Normal prion proteins occur naturally in brain tissue. Prions differ in shape from normal prion proteins due to misfolding, and are not susceptible to enzymes that normally break down proteins. In the brain, prions appear to increase their number by directly converting normal prion proteins.

Prion diseases have both infectious and hereditary components. The gene that codes for prion proteins can mutate and be passed on to the next generation. Most of the diseases also can be acquired directly by infection with prions, but unlike other infectious agents, prions provoke no immune response. Most prion diseases, however, are not highly transmissable; chronic wasting disease is the exception because infected deer that have not developed the disease shed prions from lymph tissue in their intestines, contaminating the soil and plants on which other deer graze with the prions in their feces.

An epidemic of BSE in Great Britain that was diagnosed in 1986 and infected some 178,000 cows appears to have been caused by a protein feed supplement that contained rendered remains of scrapie-infected sheep brains. In 1996 a suspicion that BSE had been transmitted to humans who died of a variant of CJD in Britain caused a scientific and economic furor as the European Union imposed a ban (1996) on the export of British beef, which was partially lifted in 1999 and fully lifted in 2006. The U.S. Dept. of Agriculture banned the import of cattle and many cattle byproducts from most European nations because of BSE. Instances of BSE in cattle have also occurred in many other European countries, Canada, the United States, and Japan, but the vast majority of cases occurred in Britain in the 1980s. There is now compelling evidence that BSE is the same disease as variant CJD (vCJD), which has killed less than 200 people, but it is not yet known exactly how the disease is passed from animals to humans.

The idea of disease-causing protein particles was first put forward in 1981 by Stanley B. Prusiner, the neurologist who coined the term prion (from proteinaceous infectious particle). The prion theory was controversial from the beginning, and although scientific evidence for the existence of such infectious particles has increased, an exact causal link between prions and the diseases they are believed to cause remains to be established. Critics believe that these diseases are caused by unidentified viruses.

The Columbia Encyclopedia, 6th ed. Copyright© 2014, The Columbia University Press.

Selected full-text books and articles on this topic

How the Cows Turned Mad
Maxime Schwartz; Edward Schneider.
University of California Press, 2003
Microbe: Are We Ready for the Next Plague?
Alan P. Zelicoff; Michael Bellomo.
American Management Association, 2005
Librarian’s tip: Chap. 5 "Shards of Glass in the Brain: Bovine Spongiform Encephalopathy (Mad Cow)"
The U.S./EU Beef Controversy and a Proposed Framework for Resolving Standards Disputes in International Trade
Taylor, Charles R.; Walsh, Michael G.; Lee, Christopher.
The Journal of Consumer Affairs, Vol. 37, No. 1, Summer 2003
Agencies Work to Corral Mad Cow Disease
Bren, Linda.
FDA Consumer, Vol. 38, No. 3, May-June 2004
Mad Cow Is the Symptom
.
The Progressive, Vol. 68, No. 2, February 2004
BSE, Risk and the Communication of Uncertainty: A Review of Lord Phillips' Report from the BSE Inquiry (UK). (Review Essay/Revue Critique)
Jones, Kevin E.
Canadian Journal of Sociology, Vol. 26, No. 4, Fall 2001
Where's the Beef? Mad Cows and the Blight of the SPS Agreement
Thomas, Ryan David.
Vanderbilt Journal of Transnational Law, Vol. 32, No. 2, March 1999
Controversies in Food and Nutrition
Myrna Chandler Goldstein; Mark A. Goldstein.
Greenwood Press, 2002
Librarian’s tip: "Mad Cow Disease" begins on p. 86
The European Union and Health Policy
Ed Randall.
St. Martin's Press, 2000
Librarian’s tip: Chap. 6 "BSE, Health Policy and Risk in the EU"
Viruses, Plagues, and History
Michael B. A. Oldstone.
Oxford University Press, 2000
Librarian’s tip: Chap. 13 "Mad Cow Disease and Englishmen: Spongiform Encephalopathies -- Virus or Prion Disease?"
Food in Global History
Raymond Grew.
Westview Press, 1999
Librarian’s tip: Chap. 11 "The 'Mad Cow' Crisis: A Global Perspective"
Spoiled: The Dangerous Truth about a Food Chain Gone Haywire
Nicols Fox.
Basic Books, 1997
Librarian’s tip: Chap. 11 "The Madness behind Mad Cows"
How to Prevent Mad Cow Disease. (Feature)
Dunne, Fintan; Ankomah, Baffour.
New African, April 2001
The Trembling Mountain: A Personal Account of Kuru, Cannibals, and Mad Cow Disease
Robert Klitzman.
Plenum Trade, 1998
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