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Mad Cow Disease Found In California: What Are The Risks To Humans?

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The United States Department of Agriculture has just confirmed the country's fourth case of mad cow disease, according to news reports.

The case was a dairy cow in central California, Reuters reported.

However, HuffPost Food reported that the cow had not entered the food chain so humans are safe in terms of consuming dairy products or beef.

According to the USDA statement:

It was never presented for slaughter for human consumption, so at no time presented a risk to the food supply or human health. Additionally, milk does not transmit BSE.

While the prospect of mad cow disease in America is scary, Cornell expert Martin Wiedmann said that the discovery of the cow is actually a testament to how good the testing for mad cow is in the U.S.

"The natural reaction is that it's a problem [they found this cow], but really they did a lot of testing and we were able to prevent this animal [from entering the food system] through testing," Wiedmann told HuffPost. Wiedmann is a professor of food science and a doctor of veterinary medicine, and is also the director of the Cornell Milk Quality Improvement Program.

Mad cow disease is also known as bovine spongiform encephalopathy, or BSE. It is a neurological disease that occurs when a prion protein damages the brains of cattle, according to the Centers for Disease Control and Prevention.

The CDC reported that there have been 22 cases of mad cow disease in North America up until February 2011, with three cases in the U.S. and 19 cases in Canada.

Mad cow disease is potentially dangerous for humans because it is linked with a human form of the disease called variant Creutzfeldt-Jakob disease (vCJD); evidence is strong that humans may develop the disease by eating meat from cows that had mad cow disease, according to the World Health Organization. There have also been four cases linked with blood transfusion, though the symptoms didn't manifest until years after the transfusion, according to the WHO.

There is a "relatively good link" between mad cow disease and variant Creutzfeldt-Jakob disease, Wiedmann said, though it's not 100 percent guaranteed that if a person eats the meat he or she will develop vCJD. And especially with this newly discovered single case of mad cow disease in the U.S., "the risk is excessively low, close to nil."

Variant Creutzfeldt-Jakob disease causes a degeneration of the brain, and a person may first notice signs of it by experiencing depression, anxiety and painful senses. As the disease progresses, it causes symptoms like problems with walking and causing involuntary movements, according to the WHO, and when a person is about to die from the disease, it causes muteness and immobility.

Variant Creutzfeldt-Jakob disease is not the same disease as classic CJD; classic Creutzfeldt-Jakob disease, which is also a prion disease, is not at all linked to mad cow disease, the CDC reported.

Classic CJD often occurs just on its own, with about one case occurring for every million people each year in the U.S., according to the CDC. The risk of this form of the disease increases as people get older. (For more on classic CJD, click here.)

For example, the CDC reported that the median death age for variant CJD is 28, while it's 68 for people with classic CJD.

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