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Mad Cow Disease
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Cause and Transmission (Epidemiology): Mad Cow Disease, officially known as Bovine spongiform encephalopathy (BSE), is a progressive neurological disorder of cattle that results from infection by a prion proteins. Since 1996, evidence has been increasing showing a relationship between BSE, or "mad cow disease", and a related disease in humans, called new variant Creutzfeldt-Jakob disease (nvCJD). Both disorders are fatal brain diseases with long incubation periods (measured in years), and are caused by prion proteins. Cattle get this disease when they consume ground-up sheep parts as part of their feed. Sheep get a related disease called scrapies that is caused by prions, and it is believed that the prions then enter cows and penetrate the blood-brain barrier. When humans ingest the prions from the infected cattle meat, the prions can enter their bodies and penetrate the blood-brain barrier. Each time the prion enters a different species, it is believed that it changes slightly so it can then infect that species. How It Affects the Body (Pathogenesis): Prions, when they get close to nerve cells in the brain, cause changes in the conformation of the cell membrane proteins. These altered receptor proteins, as well as the prions, can cause these same conformational changes in other cells. This new conformation is insoluble to digestive enzymes, so the body does not destroy them. Eventually, there is an accumulation of insoluble prion complexes in the brain tissue, which causes slow degeneration of the central nervous system. The result is dementia and degeneration of the brain, which eventually leads to death. Though there have been as many as 100 deaths in Great Britain as a result of humans consuming BSE-infected beef products, there have been no reported cases in the United States. The U.S. has made great efforts to prevent the importation of BSE-infected cattle or beef products, and extensive surveillance has been done to prevent its entry and/or spread in the U.S.
Have a little fun: check out these fun sites poking a little fun at this serious disease.
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