Mad Cow Disease . Cows with the disease often stagger around before they die. Proteins that are found naturally on the surface of nerve cells. If they become defective, they can kill the nerve cells. Scientists believe that abnormal prions cause TSEs.
Prions are nearly impossible to destroy.
They can survive temperatures used to sterilize medical equipment. A group of incurable diseases in which brain tissue slowly turns to spongy matter. In Great Britain, BSE spread among cow herds when diseased animals were rendered into cow feed. Sixteen people died after they apparently ate meat from tainted cows. The rare disorder kills about 250 people a year in the U.S. Kuru .