Bovine Spongiform Encephalopathy (BSE), more commonly called Mad Cow Disease, causes the afflicted cattle to tremble violently, lose coordination, and exhibit a wrenching display of uncontrolled spasms. First diagnosed in Great Britain in 1986, it has afflicted more than 150,000 British cattle so far, costing the government about $1 billion.

While the exact origin of the disease is not known, it may have spread from contaminated meat and bone meal in cattle feed. Rendering is the practice of grinding up dead animal remains to make products like bone meal. Adding bone meal to cattle feed is now banned in Britain, since infected cow tissue may then be passed to healthy cattle. While there is no test to detect the disease in a live animal that does not yet exhibit any symptoms, scientists can confirm a diagnosis after examining the brain tissue of a dead animal. Although there is no still no proof BSE is the cause, British officials fear the cattle disease may be linked to a human outbreak of a similar brain illness. It's called Creutzfeldt-Jakob Disease (CJD). Victims show signs of progressive dementia and examination of their brain tissue shows the same sponge-like holes found in cattle afflicted with BSE.

In the past, CJD was thought to be extremely rare, occurring at a rate of 1 case per million in the population, found in all parts of the world. Scientists had thought CJD was primarily restricted to older people. But when a new strain of the fatal disease (V-CJD) was identified in more than a dozen people, some of them teenagers, last year in Great Britain, it caused public health experts to look even more closely at how these diseases spread.

Experts say these types of diseases are not caused by a virus or a bacteria, but apparently by a mutant protein that is so tough, you can freeze it, burn it, even zap it with radiation and still not kill it. The fear is that the new strain was somehow linked to infected beef.

Even before the British outbreak, experts discovered that CJD could be transmitted as a result of human transplant surgery, where the tissue from potentially contaminated humans are implanted in a healthy individual for medical reasons. In New York, it was transmitted by a cornea transplant. In Switzerland, it was brain surgery. Electrodes used on a CJD victim were sterilized and implanted in two other patients. Both contracted CJD, and both died. Scientists don't know yet whether a blood transfusion can transmit CJD, but Dateline has learned that as a precaution, the American Red Cross has quarantined more than 200 million units of blood plasma products because the donors may have had CJD.

There has never been a single case of Mad Cow Disease in the U.S, according to the Department of Agriculture. They have, however, seen a similar disease in sheep. As a precaution, the FDA is considering a ban on feeding cattle and sheep remains back to cattle. The U.S. rendering industry, which makes bone meal, opposes the ban, maintaining the product isn't a threat.