Mad cow disease, also called bovine spongiform encephalopathy, is a disease found in cattle that causes progressive brain damage in the cattle. It may also affect goats and sheep. New variant CJD, called nvCJD, is a disease that causes the same type of progressive brain damage in humans. NvCJD may actually be the human form of mad cow disease.

What is going on in the body?

Both mad cow disease and nvCJD are believed to be caused by prions. Prions are a modified form of a protein found on normal cell surfaces. Both diseases cause a build up of prions in the brain. The increase in prions causes brain injury and degeneration The same type of prion may cause both mad cow disease and nvCJD.

What are the causes and risks of the disease?

There is a strong link between mad cow disease and the nvCJD. Most experts believe that this new variant CJD is the human form of mad cow disease. It is believed that the abnormal prion is spread from infected cattle to humans when the person eats meat or beef products. Milk and dairy products from infected cattle don't appear to carry the same risk.

At present, infected cattle are found mostly in Europe, especially in Great Britain. Even there, the risk of getting nvCJD from infected beef is only about 1 case in 10 billion servings of beef. nvCJD has been seen most often in younger people.