January 2, 2004 Philadelphia Inquirer by Faye Flam

While odds remain remote _ only 153 people in Europe have contracted the disease since it appeared in 1995 _ it is not the numbers that terrify people but the harrowing trajectory of the disease, the way it eats away at the brain.

There is no way to prevent the onset, no test for exposure, no way to test blood, and no cure.

The so-called prions that cause mad cow disease are neither viruses nor bacteria but simply errant protein molecules. Prions survive cooking and digestion, and seem to hide out in the body for 10 years or longer before growing in pockets in the brain.

Some researchers have compared mad cow to the disease in Michael Crichton's "The Andromeda Strain," noting that fictional agent was a nonliving crystal. Prions can't multiply because they aren't alive, but once they get into the brain, they convert healthy proteins into their deadly shape. Once the disease takes hold, the pockets of bad prions expand and turn the brain into a spongy texture, which is why the cow version of the disease is called bovine spongiform encephalopathy.

People who get the disease may harbor the prions for years before they begin to have psychological problems _ bizarre behavior, depression or anxiety, as well as sensation problems such as pins and needles. They lose their coordination, become paralyzed, and die within a few months.

"Each case is a major tragedy," said Lawrence Schonberger, an epidemiologist at the Centers for Disease Control and Prevention in Atlanta. It happens mostly to young people _ in their teens and 20s.

All are thought to have gotten the disease from eating meat products that contain the brain or spinal cord from infected animals _ parts that have found their way into hamburgers, hot dogs and luncheon meats in Europe, but that do not generally get into the food supply here. Last month, scientists reported that a Briton died of vCJD more than six years after he received a blood transfusion from an infected donor.

British farmers first reported this strange cattle disease in 1985, after which it took several years for scientists to figure out how it was spreading _ through a form of forced cow-cannibalism in which the remains of cattle were turned into "meat and bone meal" and fed back to other cattle. Dead cattle and other farm animals and even road kill could be "rendered" _ cooked at a high heat that was apparently not high enough.

The prevailing theory holds that the epidemic started when sheep carrying a related disease called scrapie were rendered and turned into cattle feed. Then the practice of feeding dead cattle back to cattle could have fanned the flames.

The disease continued to spread among cattle until Britain had more than 100,000 confirmed cases. Then the disease sprang up in France, Germany and elsewhere in Europe.

Experts say there is a reason the epidemic hit Britain and not the United States. Although the United States once fed rendered cow remains back to cows, meat-based meals always made up a much smaller fraction of the diet of American cattle, which are fattened primarily with grain.

Also, the epidemic had a chance to mushroom in Britain for several years before the government banned the use of rendered cow for cow food. The United States started a similar feed ban in 1997 before any known cases had emerged. "It's a big safety net we have here," said Judd Aiken, a researcher at the University of Wisconsin who studies mad cow disease.

The Washington state mad cow was more than six years old, so it could have picked up the disease before the food ban was put in place. Cattle incubate the disease from three to six years, experts say. Still, its presence suggests that other infected cows have already been slaughtered and eaten.

It was not until 1995 that the first human cases began to crop up in Britain. It wasn't clear at first whether the bizarre neurologic disease was related to mad cow, but scientists quickly discovered the prions could jump species when researchers fed infected cow brains to laboratory animals. As more British people got sick and died, "we had to change our tune," Aiken said.

Further experiments show that the disease is transmitted from eating material from the brain and spinal cord of infected animals, which had been working its way into hamburgers, hot dogs and lunch meats in Britain. Muscle meat in animals does not transmit the disease.

A few years ago, some epidemiologists estimated Britain would see thousands of cases by now, rather than the slow, steady trickle observed so far.

How many more people die from the disease depends on the incubation time. If the mad cow prions tend to lurk unnoticed for 20 years or longer, then many more cases could emerge. The pattern over the last few years suggests a shorter average incubation time and a tiny epidemic that has hit its peak, the CDC's Schonberger said.

The United States should still do what it can to increase surveillance and protection, he said. "I don't want people having to face that kind of uncertainty."

The Washington state cow was traced to a farm in Alberta, the same Canadian province where an infected cow turned up in May. Although investigators cannot conclusively link the two cases, the proximity suggests that a farm or farms in Alberta were inadvertently feeding cows infectious material.

The food may have become contaminated because a few cattle were still sent from Britain to North America through the late 1980s, Aiken said. Those infected British cows may have been killed and turned into meat and bone meal fed to other cows. "Clearly there was potential in the 1980s for the disease from Great Britain to end up in the U.S.," he said.

Some argue that other cows must have eaten the same feed and become infected. Biostatisticians have estimated that more than 1,000 cattle are infected, but others say the testing of 20,000 cattle a year is designed to catch the disease if it affects one cow in a million. That would mean of the 35 million cows slaughtered every year, no more than about 35 are likely infected.

Although hamburger from the one infected cow could have reached eight states and Guam and many people probably ate the meat before it was recalled, officials with the U.S. Department of Agriculture say it is very unlikely any of that beef was contaminated. The beef came from about 10,000 pounds of meat from the infected cow and from 19 other cows slaughtered Dec. 9 at Vern's Moses Lake Meat Co. in Moses Lake, Wash.

An additional concern surfaced last month when scientists announced the first documented case in which a patient contracted the disease after receiving a transfusion. That suggests that if the disease has jumped to even a few people and those people have given blood, it could spread to many more through the blood supply.

Paul Brown, a prion expert at the National Institutes of Health, said he thought it was unlikely the blood supply was tainted. Currently, people who have lived for more than three months in Britain and longer periods in Europe are barred from giving blood, precautions that Brown said were prudent considering the circumstances.

But people are much less likely to harbor the disease in the United States, he said, because the meat industry tries not to include the brain and spinal cord with processed meats. True, he said, the process of slaughtering cattle can still contaminate meat with nervous-system material and so the risk from eating meat is not zero, but he considers it too remote to warrant a change in policy.

Others have objected to the use of animal products to feed herbivorous cattle, whether from other cows or from pigs or chickens. But that's part of the economic value of cattle, said Paul Morley, a veterinarian from Colorado State University. He said cattle took materials we don't want _ vegetable scraps, hay, dead animals _ and convert them into products we love _ quarter-pounders and cheesesteaks.

"They are remarkable animals."