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What is mad cow disease?

Mad cow disease, or bovine spongiform encephalopathy (BSE), is a transmissible, slowly progressive, degenerative, and fatal disease affecting the central nervous system of adult cattle. The USDA tests some 20,000 animals every year for this disease.

Researchers believe that the infectious agent that causes mad cow disease is a protein normally found on cell surfaces, called a prion. For reasons still unknown, this protein becomes altered to become disease producing.

Does cooking food kill the prion that causes mad cow disease?

Common methods to eliminate disease-causing organisms in food, like heat, do not affect prions. Also, prions only seem to live in nervous system tissue.

Does mad cow disease affect humans?

A human version of mad cow disease called variant Creutzfeldt-Jakob disease (vCJD) is believed to be caused by eating nerve tissue, such as brain and spinal cord, from cattle infected with mad cow disease. For this reason, the USDA requires that all nervous system materials be removed from cattle that are unable to walk -- an indication that there may be a neurological problem. These cow products do not enter the U.S. food supply. The USDA believes this practice effectively safeguards U.S. public health from vCJD.

According to the CDC, no cases of vCJD have been identified in the U.S.

Having said that, it is important to clarify the differences between variant CJD and another form of the disease, referred to as classic CJD. Classic CJD occurs each year at a rate of 1 to 2 cases per 1 million people throughout the world, including in the U.S. and other countries where mad cow disease has never occurred. It is not linked to the consumption of nerve tissue from mad cow disease-affected cattle -- both vegetarians and meat eaters have died from classic CJD.

What are the symptoms of vCJD?

The disease affects all age groups and is very hard to diagnose until it has nearly run its course. In its early stages, people have symptoms related to the nervous system, like dementia and jerking muscle movements. But only in advanced stages of the disease can brain abnormalities be detected by X-ray or MRI (magnetic resonance imaging).

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