Nutrition Action Healthletter
July/August 1997 — U.S. Edition

"I can still see his expression," says Stephen Churchill's father. "It was as if he could see what was happening, but couldn't work out how he could stop it."

Churchill watched helplessly as his 19-year-old son lost his ability to feed and dress himself, as the hallucinations and panic attacks grew worse. Five months later, in May 1995, Stephen was dead -- the first known victim of V-CJD, a new form of a rare, incurable brain disease.

More than a dozen others would follow in Great Britain, including two more teenagers, a 42-year-old businessman, and a pregnant woman who delivered her baby while in a coma.

In March of 1996 the World Health Organization convened a group of experts to find out how Stephen Churchill and the other people contracted V-CJD.

The most likely explanation: They ate British beef that had been contaminated with a rare, abnormal protein.

What the popular press calls "mad cow disease" had apparently spread to humans. Could the same thing happen in the U.S.? Possibly . . . unless we change the way we feed and slaughter beef cattle.

Going Mad

To halt the spread of mad cow disease, the British government has destroyed more than a million animals. Hundreds of thousands of frozen cow carcasses are piled up in storage facilities. Mountains of cow flakes -- what's left after grinding and boiling those carcasses -- will take more than a decade to burn.

But even when the incinerators stop smoking, the mad cow crisis may not be over. The disease takes time to do its damage. Over the next several decades, hundreds -- perhaps thousands -- of people who have already eaten infected beef could die.

That's just in Great Britain. What of the thousands of potentially infected cattle -- and the animal feed that may have made them sick -- that Britain has exported to dozens of countries, including the United States and Canada?

"Mad" cows have already been identified in Canada, Denmark, France, Germany, Ireland, the Netherlands, Oman, Portugal, and Switzerland. And V-CJD, the disease in humans that may have been caused by infected cattle, has crossed the English Channel to claim a young man in France.

How did mad cow disease spread from herd to herd in Great Britain and make its way into the human food supply? The story starts with a rare disease.

Creutzfeldt-Jakob Disease (CJD)

"At least one in every million people gets Creutzfeldt-Jakob Disease (CJD) each year," says Ermias Belay, an epidemiologist and CJD expert with the Centers for Disease Control and Prevention (CDC) in Atlanta.

CJD belongs to a family of rare disorders in humans and animals called transmissible spongiform encephalopathies, or TSES: "encephalopathies" because they're diseases of the brain, "spongiform" because they leave infected brain tissue looking spongy, and "transmissible" because they can be spread, though not easily.

The other major TSEs are kuru, found in a brain-eating tribe in New Guinea; scrapie, found in sheep; and bovine spongiform encephalopathy (BSE), found in cows (see "The ABC's of BSE" below).

"CJD is a devastating disease," says Belay. "Patients become forgetful, then can't stand up and walk properly. Their legs and arms jerk uncontrollably, their speech becomes disorganized, and they have difficulty speaking and remembering what words mean. They don't even recognize their families."

More than 90 percent are dead within a year. What causes TSEs like Creutzfeldt-Jakob Disease?

"Many researchers believe that prions have something to do with it," says Belay. Prions (PREE-ons) are proteins that are found naturally on the surface of brain cells.

"In CJD, these prions flip over into an abnormal shape that the body cannot get rid of," explains Belay. "The abnormal prions accumulate in the brain cells until they begin to interfere with the cells' normal functioning and the victim becomes sick."

In about 85 percent of CJD cases, the prions mutate for no apparent reason. Another 15 percent seem to be hereditary. And less than one percent are spread from one person to another, but only under very unusual circumstances.

For example, nearly 100 people with dwarfism came down with CJD between 1975 and 1985 after they were given injections of human growth hormone (HGH). At that time, the only source of HGH was brains from human cadavers. Some, it turned out, were infected with CJD.

"The use of this hormone was discontinued as soon as the first cases were discovered," explains Belay. "Today, all human growth hormone is produced by genetic engineering, so it carries no disease."

Three other victims contracted CJD from contaminated instruments used to perform brain surgery on patients with CJD.

"Conventional sterilization doesn't destroy the abnormal prions," says Belay.

Prions may be difficult to destroy, but at least they tend to keep to their own species.

"Scrapie has been found in sheep in England for more than 300 years, and in the United States since 1947," says Joe Gibbs, acting chief of the Laboratory of Central Nervous System Studies at the National Institutes of Health (NIH). "But there's never, ever, been a shred of evidence that scrapie in sheep has caused any disease in humans."

It's not easy to spread TSEs between species . . . even in the laboratory.

To transmit BSE from a cow to a mouse, explains Paul Brown of the NIH, "requires an injection into the brain of a thousand times more infected tissue than it takes to give BSE to another cow.

"We're counting on this species barrier to help protect us," says Brown, who chairs the Food and Drug Administration's TSE Advisory Panel.

But the barrier may have been breached.

The Empire Strikes Back

In March of 1996, scientists reported that ten people in Great Britain had been diagnosed with a new form of Creutzfeldt-Jakob Disease called V-CJD ("V" for "variant"). Its brain lesions more closely resembled those of cow BSE than those of human CJD.

"Nobody knows for certain how they got the new disease," says the CDC's Belay. "But evidence is accumulating every day that it was from eating meat from cattle that were infected with BSE."

How did the cattle become infected?

"Around 1980, several changes occurred in the way the British produced a meat-and-bone-meal protein supplement for cattle," says Don Franco, director of scientific affairs for the U.S. National Renderers Association. The supplement is made from, among other things, slaughterhouse waste, dead pets, and road kill -- diseased animals as well as healthy ones.

"Because energy was in short supply and the use of solvents was discontinued for safety reasons," says Franco, "the animal tissues weren't rendered to as high a temperature or for as long as they had been in the past."

Those changes may have allowed enough disease-causing prions to survive. "They could have come from the brains of either sheep with scrapie or cows with spontaneous BSE that went into the mix," says Franco. (BSE may occur naturally, speculate some researchers, in about one out of every million animals.)

Some of the cows that ate the tainted feed developed BSE. When those cows were slaughtered, some of their body parts were rendered into animal feed, which infected more cows.

And while scientists haven't been able to prove it yet, many believe that Stephen Churchill and the other victims in Great Britain may have gotten the variant form of Creutzfeldt-Jakob Disease after they ate meat from the tainted cows. But they're not sure.

"Everybody's waiting for the completion of a study that's comparing the 'strain' of prion or other agent found in the V-CJD victims with the 'strain' found in cattle with BSE, " explains U.S. Department of Agriculture (USDA) senior veterinarian Linda Detwiler. Results are expected later this summer.


Don't know your BSE from your TSE? Here's a little help.

  • AMR (Advanced Meat Recovery) A process in which steel cylinders remove an additional 1 and a half pounds of meat from each cow carcass. Ground beef and processed meats can contain up to ten percent AMR meat.

  • Mad Cow Disease. A popular name for BSE. Cows with the disease often stagger around before they die.

  • Prions (PREE-ons). 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.

  • TSE (transmissible spongiform encephalopathy). A group of incurable diseases in which brain tissue slowly turns to spongy matter. It includes:
BSE (bovine spongiform encephalopathy). 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.

CJD (Creutzfeldt-Jakob Disease). The rare disorder kills about 250 people a year in the U.S.

Kuru. Scientists discovered in the 1960s that the disease spread among New Guinea tribespeople who ate the brains of dead relatives.

Scrapie (SCRAY-pee). It's found in sheep. Scientists believe it has never caused death in humans.

V-CJD (Variant Creutzfeldt-Jakob Disease) A new form of CJD that has killed 16 people in Great Britain and France. Although scientists haven't been able to prove it yet, the victims may have contracted V-CJD after they ate beef infected with BSE. V-JCD has never been detected in the U.S.

Jumping the Firewall

Scientists and public health officials in the U.S. are scrambling to keep BSE out of this country.

In 1989, the USDA banned the import of live cattle and most beef products from Great Britain and other countries where BSE exists.

But some of the cows were already out of the barn.

Between 1981 and 1989, the U.S. imported 496 cows from Great Britain. "We've tracked down 464 of them, and not one has shown signs of BSE," says the USDA's Detwiler. The others have probably died of old age by now, she adds.

"We've also examined the brains of 5,700 sick cows from 48 states and Puerto Rico and haven't found a single case of BSE," says Detwiler.

"I think it's essential for everybody to know that the USDA is looking, and that we're all ready to jump when it happens . . . if it happens," says the NIH's Joe Gibbs.

So far, it hasn't.

"We have people who have spent their careers trying to find BSE and haven't succeeded," says Will Hueston, associate dean of the Virginia-Maryland College of Veterinary Medicine in College Park, Maryland. Hueston used to run the USDA's BSE surveillance program.

"You can't just hide BSE if a cow's got it," he adds.

What about BSE-like diseases in other animals that could get into the food supply?

"None have been found in either poultry or pigs," says the NIH's Paul Brown. "Pigs can get BSE, but only by having diseased brain matter injected directly into their brains."

As for sheep: While they do have scrapie, "we have far less of it than the English do," says the Renderers Association's Franco. What's more, says Franco, since 1989 the U.S. rendering industry has voluntarily banned the use of sheep brains to make animal feed.

And in 1996, just nine days after Great Britain disclosed the possible link between BSE in cows and V-CJD in humans, the U.S. meat industry said that it would stop giving cows the same kind of meat-and-bone meal that might have caused BSE to spread in Great Britain.

The FDA has taken things a step further. It has announced a ban on feeding rendered mammals to cows, sheep, and goats.

"This will build a firewall around our meat supply," says Gary Weber of the National Cattlemen's Beef Association. "It will be a gangbusters of a protection," seconds the NIH's Brown.

But only if it's enforced. In 1993, the FDA estimated that as many as half of all U.S. renderers were not complying with their voluntary ban on including sheep brains in animal feed.

"Today we have about 90 percent compliance," estimates the rendering industry's Don Franco. But no one's checking. And 90 percent compliance means ten percent noncompliance.

"The new regulation definitely needs a verification process to make certain it's being followed," says former USDA official Will Hueston.

It may need more than that.

Simply Stunning

"If BSE should occur in the US," says Will Hueston, "then the most sensible thing we can do is to make sure we don't have a system that can spread it into the human food supply."

Easier said than done. The animal tissues most likely to transmit BSE are the brain and the spinal cord. "We should keep these out of the food chain," says the NIH's Joe Gibbs.

But the way we slaughter and extract meat from cattle may do just the opposite.

Meat processors can add animal brains to foods like hot dogs and luncheon meats, but "nobody does, to our knowledge, in part because the texture isn't suitable," says Janet Riley of the American Meat Institute, a trade association of meat processors. If brains are added, they've got to appear in the ingredient list.

Brains have other ways of getting into the food supply, though.

According to disturbing new research from Texas A&M University and the Canadian government, cattle brain tissue can end up scattered throughout the carcass during slaughtering.

In some plants, the first step in slaughtering a cow is to stun it with a pneumatic gun. "The force is so explosive that it splatters brain tissue into the cow's blood vessels," says Graham Clarke, Chief of Red Meat Inspection for Canada's Food Inspection Agency.

"Our research shows that it's possible that microscopic particles of brain matter can be circulated to the lungs, liver, and maybe other sites," reports Tam Garland, a research veterinarian at Texas A&M. The Canadian government has found the same.

"That's not surprising," says Garland, "because it has long been known that the same thing happens in humans who suffer head traumas.

"Brain tissue could, in theory, circulate anywhere," she adds. That includes the cow's muscles, which are turned into steaks and burgers.

"The implications are frightening," says Garland.

"My gut feeling is that the cattle industry will eventually have to change the way it slaughters cattle as a result of Garland's research," says Will Hueston.

Human deboners remove all the meat they can as each cow carcass goes whizzing by on the production line. What they can't easily cut away ends up at AMR plants, where metal cylinders rub another 1 and a half pounds per carcass off the bones. Why bother? Because it boosts the yield by as much as 300 million pounds a year.

Up to ten percent of your next hamburger or slice of bologna could have come from an AMR plant. And you'll never know. Foods that contain AMR meat don't have to say so on the label.

The problem is that any tissue that's on or near the bones -- including parts of the spinal cord -- can end up in the mix.

"Most AMR plants voluntarily remove spinal cords before processing, " says the American Meat Institute's Janet Riley. But last year, in response to complaints from consumer groups (including CSPI), the USDA surveyed seven AMR plants in the U.S. The Feds found bits of spinal cord in two out of 11 meat samples.

The USDA has warned AMR plants not to include any spinal cord tissue in their meat. Inspectors have been instructed to send any suspect AMR meat to a USDA lab for testing.

"Let's Do It Properly"

Most scientists and public health experts agree that the U.S. food supply isn't in imminent danger. BSE hasn't been detected in our cow herds. No similar diseases occur naturally in poultry or pigs. Scrapie is confined to sheep. And "we are sitting on a well-documented contingency plan" to prevent the spread of BSE if it shows up, says the NIH's Joe Gibbs.

But we need to close the loopholes.

"If we've learned anything from the British," says Gibbs, "it's that rendering is not the way to provide food supplements for cattle and other species, because rendering was obviously the cause of the BSE outbreak in England.

"We also learned that the brain and spinal cord are infectious, and that we should keep them out of the food chain.

"If we're going to do this thing, let's do it properly. Even if there is a very low risk, let's try to reduce it as much as possible."

The Bottom Line

  • Scientists have never detected "mad cow disease" (BSE) in cattle in the U.S.
  • To prevent BSE from spreading through the food supply in case infected cows turn up here, the FDA has announced a ban on the feeding of rendered mammals to cows and sheep.
  • To prevent the spread of brain tissue when cows are slaughtered, the USDA should look for alternative, humane approaches to stunning.
  • To keep BSE out of ground beef and processed meat, the USDA should make sure that meat from advanced meat recovery (AMR) systems is free of spinal cord tissue.

Nutrition Action Healthletter