Mad cow disease is an incurable, fatal brain disease that affects cattle and possibly some other animals, such as goats and sheep. The medical name for mad cow disease is bovine spongiform encephalopathy (pronounced: bo-vine spun-jih-form en-seh-fah-la-puh-thee), or BSE for short. It's called mad cow disease because it affects a cow's nervous system, causing a cow to act strangely and lose control of its ability to do normal things, such as walk.
Only certain animals can get BSE — people don't actually get mad cow disease. However, experts have found a link between BSE and a rare brain condition that affects people, called variant Creutzfeldt-Jakob disease (CJD). Researchers believe that people who eat beef from cows that have BSE are at risk of developing a form of CJD.
CJD is caused by an abnormal type of protein in the brain called a prion. When people have CJD, cells in the brain die until the brain eventually has a "sponge-like" appearance. During this time, people with the disease gradually lose control of their mental and physical capabilities.
To date, very few people have been diagnosed with the form of CJD that's been linked to mad cow disease. By November 2006, only 200 cases of this rare condition had been reported worldwide. Of these, most were identified in Britain. Several of the people diagnosed with the disease outside Britain — including two cases in the United States — had a history of exposure in Britain or in a country where government officials reported BSE. Experts believe that the people got CJD after eating beef products from cows that had BSE.
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