Nutrition Action Healthletter - How Now, Mad Cow?



	June 2001 — U.S. Edition


	Twenty-one-year-old Clare Tomkins became uncharacter- istically depressed after a holiday with her fiancé. Twenty-four-year-old Donna McIntyre suffered from violent mood swings and slurred speech. Victims of variant Creutzfeldt-Jakob Disease (vCJD) are often misdiagnosed with depression or paranoia. But then they start to lose their ability to walk or keep their balance. They see double. Their memories evaporate. They slowly waste away—a 22-year-old French victim identified only as Arnaud was down to 77 pounds. Mercifully, many of them end up unaware of their condition. But there are exceptions. “Am I dying?” Donna McIntyre asked her parents in a rare moment of lucidity. She was. VCJD spares no one. Variant Creutzfeldt-Jakob Disease is caused by rogue proteins called prions. So is mad cow disease. And the connection between the two is spreading fear and panic across the globe. Why do some people who eat BSE-infected meat develop variant Creutzfeldt-Jakob Disease while others don’t seem to? To find out, scientists have tested tissue samples from 76 of the 101 people who have died from vCJD. Remarkably, all 76 “were homozygous for methionine at codon 129 on the prion protein gene,” as the National Institutes of Health’s Paul Brown puts it. Translation: they inherited from each of their parents a gene that substitutes one amino acid (methionine) for another (valine) in one portion of the prion protein that the gene tells the body to make. For some reason, “the methionine form of the protein seems to make people more susceptible to vCJD,” says Brown. Four out of every ten people inherit a copy of the gene from each of their parents. It’s always possible that people who don’t have two copies of the gene also develop vCJD, but that “it just takes them longer to become ill,” cautions Brown. The mad cow epidemic in the United Kingdom appears to have peaked (although the number of human vCJD cases hasn’t). At its worst, in early 1993, veterinarians were diagnosing about 1,000 new cases each week, mostly in Great Britain. Now, it’s down to less than 30 cases a week in the UK and to less than ten a week in the rest of Europe, to which Britain exported contaminated feed until 1996. Part of the reason for the decline: the British government has destroyed more than four million cows, many of them healthy, to prevent new outbreaks. (It has also destroyed hundreds of thousands of animals to halt the spread of foot-and-mouth disease, which poses no threat to humans.) Is it safe to eat meat in Europe? Your odds of contracting variant Creutzfeldt-Jakob Disease (vCJD) from eating a serving of British beef is about one in ten billion, says the U.S. Centers for Disease Control and Prevention. You’d have the same chance of getting sick from eating at McDonald’s if only one of the ten billion or so hamburgers it has sold since it opened in 1955 were infected. If that still ruins your appetite, steer clear of beef entirely when you travel (milk, cheese, and other dairy foods are fine). If you are going to eat beef, stay away from burgers, hot dogs, and sausages, which are more likely to be contaminated with infected nervous-system tissue than boneless steaks, roasts, and other whole cuts. Cuts like the T-bone, porterhouse, standing rib roast, prime rib with bone, bone-in rib steak, and (if they contain bone) chuck blade roast and loin may contain tiny nerves called dorsal root ganglia, which are infectious if they come from a cow with BSE. And don’t assume that you’re out of danger if you’re traveling outside of Europe. For well over a decade, England exported its tainted animal feed to more than 70 countries. Some scientists believe that the next epidemic of mad cow disease—and the next wave of human vCJD victims—could occur in places like Russia and Asia, which have few if any safeguards. So far, cattle with mad cow disease have turned up in Belgium, Denmark, France, Germany, Great Britain, Ireland, Italy, Liechtenstein, Luxembourg, the Netherlands, Portugal, Spain, and Switzerland.

They’re disoriented, irritable, apprehensive, and unable to stand or walk properly. You can see why the British press called them “mad cows” in 1986, when the first cases of the mysterious ailment surfaced. And the name has stuck. In part, that’s because “bovine spongiform encephalopathy” (BSE) is a mouthful. But mad cow also conjures up the mysterious nature of the frightening new disease.

The fear crystalized in the spring of 1996, when British health officials identified ten people with a new and devastating brain affliction. It seemed to resemble Creutzfeldt-Jakob Disease (CJD), a rare, invariably fatal neurological condition.

But unlike CJD, which seldom strikes those under age 50, the newly christened variant Creutzfeldt-Jakob Disease (vCJD) was turning up in young men and women. While it often started with leg pain and difficulty walking, the progressive brain damage eventually left them hallucinating, their memories destroyed, unable to see, speak, or feed themselves. Within a year or two, it left them dead. In 1996, vCJD killed ten people; last year it killed 27. Just over 100 people have died from the disease, all of them in Europe. No one knows how many more are already infected and will develop vCJD, which may take five to ten years to emerge.


	BSE in cows and vCJD in humans are both caused by prions gone awry. The brains of all mammals (including humans) contain harmless proteins called prions (pronounced PREE-ons). In BSE and vCJD, infectious, deformed prions somehow induce harmless prions to become deformed. Scientists aren’t certain how deformed prions do their damage. One possibility: as the prions accumulate in the brain, brain cells start to die, leaving holes where thoughts and emotions, speech and coordination once resided. It’s no coincidence that the disease in cattle resembles the disease in humans. “The evidence is now quite strong that exposure to cattle with BSE causes vCJD in people,” says Ermias Belay of the Centers for Disease Control and Prevention (CDC) in Atlanta. And that raises an unsettling question: Even though no cases of mad cow disease or human vCJD have ever been discovered here, how susceptible is the beef-loving, barbecuing, meat-and-potatoes, McDonald’s-on-every-corner United States? On the surface, the news is good. Since 1990, the U.S. Department of Agriculture (USDA) has analyzed the brains of more than 12,000 cattle, most of them chosen because they showed signs of neurological disease or other health problems before they died. “Not a single case of BSE has ever been detected in any of those animals,” says Linda Detwiler, a veterinarian who heads the USDA’s anti-BSE efforts. “Beef produced in the U.S. is free from BSE, so consumers shouldn’t worry,” says Paul Brown, an epidemiologist at the National Institute of Neurological Disorders and Stroke. Brown chairs a panel that advises the Food and Drug Administration on BSE. Some of the credit goes to the USDA’s 1989 ban on importing ruminants (cattle, sheep, and goats) and most ruminant by-products from the United Kingdom. (Ruminants have several stomachs, which allows them to regurgitate their food and chew it a second time.) The ban has been gradually extended to cover all of Europe. In Great Britain, “the first cows with BSE probably got it from eating sheep with scrapie,” says Will Hueston, Chair of Veterinary Medicine at the Virginia-Maryland Regional College of Veterinary Medicine in College Park, Maryland. Scrapie (pronounced SCRAY-pee) is a disease that has afflicted sheep, especially in the United Kingdom, for more than 300 years. Like BSE, it’s caused by prions. We don’t think of farm animals eating other animals, but eat them they do...usually in the form of meat-and-bonemeal protein supplements, which are made by rendering (boiling and grinding up) the carcasses of sheep, cattle, pigs, poultry, road kill, whatever. Just about anything not removed at the slaughterhouse—bones, brains, internal organs—goes into the renderer’s pot. It would have been easy for infected brain tissue from sheep with scrapie to have gotten into a meat-and-bonemeal supplement that was fed to cattle.


	“The cattle got BSE from this feed,” says Hueston, “and then their remains were recycled as meat-and-bonemeal, which infected more cattle.” Could the same thing happen here? All it may take is one infected sheep or cow or one contaminated batch of animal feed. The government has set up several “firewalls” to keep mad cow disease out. One protects cattle from BSE; another prevents people from getting sick if the first one fails. So far, both seem to be working, but both have gaps in them. In 1997, the FDA prohibited animal-feed mills from mixing meat-and-bonemeal made from rendered cows and sheep into feed for cows or sheep. (The supplements can be fed to pigs and poultry, because they don’t get BSE-like diseases from food.) But that ban isn’t foolproof. In 1998 and 1999, the FDA inspected 63 plants that render both ruminants (cattle and sheep) and non-ruminants (pigs and poultry). Ten of them had no system in place to keep the two apart. Thirty-seven of the 300 feed mills that handle both ruminant and non-ruminant meat-and-bonemeal also had no system to keep them apart. The problem made headlines last January, when a Texas feedlot inadvertently fed meat-and-bonemeal intended for pigs and poultry to more than 1,200 cattle. A clerk at Purina Mills in St. Louis had mistakenly mixed the supplement into the company’s cattle feed. Although the meal was produced from BSE-free cattle, Purina Mills purchased the animals and turned them into pig and poultry feed. The FDA’s inspection results were a real eye-opener for the rendering and feed industries, which are scrambling to police themselves before the Feds step in. Or before Ronald McDonald does. The restaurant chain that buys more beef than any other has been stung by sharply lower sales at its European outlets. It doesn’t want to see the same happen here. So McDonald’s has told its U.S. suppliers to document that their cattle haven’t been fed meat-and-bonemeal made from cows or sheep. “The U.S. has always been BSE-free,” says McDonald’s spokesman Walt Riker. “McDonald’s has the world’s biggest shopping cart, and we try to use that leverage for good.” When McDonald’s talks, the beef industry listens. “We’re calling for the complete removal of ruminant-derived meat-and-bonemeal from those plants that make feed for cattle,” says Richard Sellers of the American Feed Industry Association, which represents nearly 700 feed companies. “That should prevent the accidental mixing of the two kinds of feed.” “We’ve already set up an independent third-party certification program to verify that our members are following all FDA regulations about the proper labeling of their products,” adds Sellers. The rendering industry is doing likewise. “On April 1, we began to have outside inspectors verify that renderers are following all government regulations,” says Tom Cook of the National Renderers Association. Another potential breach in the BSE firewall has already been plugged. Up until 1998, many slaughterhouses stunned their cattle with an air-injection rifle before killing them. The explosive blast of air to the head often scattered brain tissue throughout the carcass (see July/August 1997, cover story). In cows with BSE, brain tissue is highly infectious. “The beef industry has eliminated air-injection stunning because of the potential for contamination,” says Janet Riley of the American Meat Institute, an industry group. “No one is even manufacturing the equipment any more.” Prions mostly infect an animal’s brain and spinal cord, not its meat. So how did 101 people (so far) in Europe become infected with vCJD? “Most likely from eating inexpensive beef products that contained mechanically separated meat,” says the NIH’s Paul Brown. “Mechanically separated meat is a paste produced by compressing carcasses, much like a used car is crushed into a dense block of metal,” he explains. The British meat industry used this extruded paste, which could have included spinal cords, in hot dogs, sausages, and burgers. “So, while a filet mignon was safe to eat,“ says Brown, “a hot dog made with mechanically separated meat was not at all safe.” This year, the European Union banned mechanically separated meat made from cattle and sheep, though as of April the ban hadn’t fully taken effect. Unfortunately, the U.S. hasn’t done the same. Mechanically separated beef—spinal cords and all—is still allowed here, though it’s hard to get a handle on how common it is. “In the U.S., mechanically separated beef is rarely used any more,” says Janet Riley of the American Meat Institute. “The machinery was expensive and there were too many restrictions on how the product could be used,” adds the USDA’s Bob Brewer. Yet neither the AMI nor the USDA can say how much—if any—mechanically separated beef Americans eat each year. The good news: Any food that contains mechanically separated beef has to say so on the label. The bad news: There are no labels when you eat out. So it’s possible that hot dogs, sausages, hamburgers, and some other restaurant foods made with ground meat could contain spinal cord tissue. If mad cow disease ever shows up in the U.S., that could spell trouble. Many U.S. meat processors have switched from mechanically separated beef to advanced meat recovery (AMR), which also extrudes meat from carcasses under pressure, but without crushing the bones. That alone makes it less risky than mechanically separated beef. More than 60 percent of cattle are now processed using AMR, which has a huge competitive advantage over mechanically separated meat. It’s not a paste, and labels don’t have to identify it. AMR meat often ends up in hamburgers, hot dogs, sausages, and the meat in pizza toppings and taco fillings. Companies are supposed to remove the animals’ brains and spinal cords before putting the carcasses through the AMR machinery, but getting out all of the spinal cord isn’t easy. “It requires special tools and skills,” says Glenn Schmidt, a meat scientist at Colorado State University. “The workers have to reach down to the neck region of the carcass to remove the spinal cord by scraping or suction, and sometimes they don’t get all of it.” Sometimes is right. Since 1996, USDA surveys have turned up spinal cord tissue in four of 70 samples of AMR meat. That worries the U.S. beef industry, which has seen its European counterpart decimated by the mad cow scare. The National Cattlemen’s Beef Association has hired Schmidt to test the meat produced at the eight major AMR plants. “We’re finding that some companies are succeeding at keeping spinal cord tissue out, while other companies are still working toward that goal,” says Schmidt. The only way to guarantee that AMR meat is free of nervous-system tissue is to require meat processors to remove the entire spinal column (bones and all), not just the spinal cord, before sending cattle carcasses through their machinery (see “Making Meat Safe,”). Click on image for larger view What’s the risk of getting variant Creutzfeldt-Jakob Disease from eating meat? Beef is safe to eat in countries where the cattle don’t have BSE. In countries where BSE has been found, it’s safe to eat boneless steaks, roasts, and other muscle meats (see “When You Travel,”). But you’d be smart to avoid processed meats like burgers, sausages, and the meat toppings on pizzas. (McDonald’s, Burger King, and Wendy’s, the three chains we contacted, say that they have never used advanced meat recovery or mechanically separated meat in any of their outlets in the U.S. or abroad.) Pork and poultry are safe, even in countries where cattle have BSE. “We can produce a BSE-like disease in pigs in the lab by injecting infected tissue into their brains,” says the National Institutes of Health’s Paul Brown, “but not by putting it into their food.” Poultry don’t seem to get BSE-like diseases. Fish and shellfish caught in the wild are safe, even in countries where cattle have BSE. Farm-raised fish should also be okay, since they’re mostly fed fish meal and soybean meal, neither of which carries infectious prions. Lamb and mutton are safe, even in countries where cattle have BSE. “There’s never been any evidence that humans can get a brain disease from eating the meat from sheep or goats with scrapie,” says Paul Brown. Dairy products are safe, even if they come from cows with BSE. Milk and other dairy products don’t carry infectious prions. Game meat like wild elk and deer can suffer from “chronic wasting disease,” which occurs naturally and belongs to the same family of prion diseases as scrapie, BSE, CJD, and vCJD. “No cases of humans getting a brain disease from eating wild game with chronic wasting disease have ever been documented,” says the NIH’s Paul Brown. Still, he adds, “you’d have to be crazy to eat the brain of a wild animal.” Gelatin is an animal protein that comes from the hides and bones of cows and pigs. It’s what makes Jell-O gel and gummy bears soft and pliable. It’s used as a thickener in some yogurts, ice creams, and other foods. And it’s in the capsules, gel caps, and coatings of many over-the-counter supplements and prescription drugs. Is gelatin infectious if it’s made from animals that have mad cow disease? Probably not. Skin and hides don’t seem to carry any risk, while bones have a “low infectivity” (because they contain bone marrow), according to the World Health Organization. In 1997 the FDA prohibited gelatin manufacturers from using hides and bones from cows with any signs of neurological disease. “Many confectioners do not use beef gelatin,” says Susan Smith of the National Confectioners Association. “But some do.” (You can’t tell from the label.) “We use mostly pork gelatin to make our Jell-O,” says Claire Regan of Kraft Foods. Few if any scientists see a problem. “Gelatin is off my radar screen,” concludes BSE expert Will Hueston of the Virginia-Maryland Regional College of Veterinary Medicine. Vaccines are often made using cattle by-products that could be infectious. But there is no evidence that any of the world’s 101 cases of variant Creutzfeldt-Jakob Disease were caused by contaminated vaccines. Nevertheless, in 1993 the FDA asked vaccine manufacturers to stop importing animal products from countries “where BSE is known to exist or may exist.” Last year the government learned that five vaccine-makers hadn’t complied and ordered them to do so. Clearly, the benefits of vaccination outweigh a risk that the government considers “theoretical and remote.” Glandular supplements are often made from animal parts that could be infectious. Nature’s Plus Ultra Male, for example, contains cow tissue from the brain, eyes, pituitary, and spleen. The major supplement-makers say that they’re complying with a 1993 FDA request that they not use cow tissue from countries where BSE exists or may exist. “We’ve found that almost all of our suppliers use only domestic cattle as sources, and that those that do import bovine-derived materials do so from non-European countries,” says Phillip Harvey of the industry’s National Nutritional Foods Association. That’s based on a NNFA survey of its members. But the FDA has no system in place to monitor what companies actually put into their supplements. Our advice: avoid any supplements that contain animal brains, eyes, or glands, especially since there’s little evidence that they work. Click here for links to the most useful Web sites with information on mad cow disease.

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