A Wasting Disease That Eats Up the Brain, Causing Death
They call it “mad cow” disease, but its scientific name is bovine spongiform encephalopathy. In elk and deer, it is called wasting disease. And when it is transmitted to humans, it is called variant Creutzfeldt-Jakob disease.
But whatever the name, it is a lethal infection that eats up the brain, producing first severe mental impairment, then a loss of bodily functions and, ultimately, death.
It is not an infection in the normal sense because it is not caused by a virus, a bacterium or some parasite. Rather, most scientists believe, it is caused by an unusual protein called a prion (pronounced PRY-on or PREE-on).
These small proteins damage brain cells, producing characteristic holes that make the brain look like a sponge. More important, when they come into contact with a healthy form of the same protein -- one that has a slightly different three-dimensional conformation -- they somehow induce it to convert into a prion as well. And when these altered proteins are transmitted from one animal to another via blood or through ingestion of infected proteins, they transmit the disease.
A small number of scientists have resisted this theory, arguing that there must be some other, more conventional agent involved in spreading the disease. But a variety of laboratory experiments have proved the theory so convincingly that neurologist Stanley Prusiner of UC San Francisco was awarded the Nobel Prize for Physiology or Medicine for its discovery.
The first evidence for the disease was discovered in the early part of the 20th century among the South Fore people of New Guinea, who suffered a devastating brain disease called kuru. Half a century of research showed that kuru -- which ultimately proved to be Creutzfeldt-Jakob disease -- was spread through the tribe because of the ritualistic practice of eating the brains of the dead.
Creutzfeldt-Jakob disease itself can occur spontaneously as a result of gene mutations. About 20 Californians develop it each year. So far, there is no evidence that these victims transmit the disease to other people.
The disease came to the world’s attention in 1985 when British farmhands noticed that a Holstein cow began to stagger, head-butt other cattle and shy away from humans. They called it “mad cow” disease, but researchers adopted the more formal name of bovine spongiform encephalopathy, or BSE.
Eventually, British researchers concluded that BSE was caused by the now-outlawed practice of supplementing the dairy cattle’s feed with ground-up sheep infected with a related disease called scrapie.
Over the next decade and a half, Britain destroyed 3.7 million cattle in an only partially successful effort to eradicate the disease. Ultimately, however, it spread throughout Europe. Earlier this year, it was found in a single cow in Canada, and now it apparently has come to the U.S.
The disease can occasionally be transmitted from cattle to humans, where it is known as variant Creutzfeldt-Jakob disease, or vCJD. To date, there have been about 150 such cases, most of them in England, but a few in France, Italy, Ireland, Canada and the United States.
There is no treatment or cure for the disease. Prusiner’s team reported two years ago that the antimalarial drug quinacrine seemed to retard its progress in mice, but subsequent trials in humans showed no benefit.
A related ailment called chronic wasting disease has recently been moving through herds of deer and elk in the West, spread via saliva and feces. Hunters have been encouraged to thin the herds to limit the spread of the disease, but have been warned not to eat the meat.
