Mad Meat

We're just starting to learn how 'mad cow' diseases move through the food chain and what they can do to us.

THE CHANGES IN KEN JOHNSTON were so minor that at first they were easy to brush away. Peggy Johnston first noticed last January that her husband was coming home unusually tired after working at the Sundance Golf Course they owned in Spokane. She also noticed he'd become uncharacteristically irritable and easily depressed, but she reasoned that the hard, physical work of maintaining the golf course through the winter's harsh ice storms had simply taken a toll on her husband of 38 years.

Then his golf game started to go. Ken had been a golf pro before they'd bought the Sundance and he was serious about his game. When they vacationed in Hawaii at the end of January, though, "he wasn't playing like he normally does," says Peggy. "He was all over the place."

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By May, the fatigue had deepened, and Ken abandoned his four-day-a-week swimming regimen. One day, after playing poorly at the Spokane Country Club, he told Peggy he was giving up the game he loved. "I can't hold onto the club," he complained. In fact, he was having trouble controlling his entire left arm. Ken's moods worsened. He became easily frightened, even paranoid. "I couldn't figure out what was going on," says Peggy, her voice raw with grief. "It was so subtle I didn't realize how bad it was." Figuring her husband would eventually snap out of his funk, she looked forward to a June trip with her church group for some much-needed relaxation. On the morning she was due to leave, Ken came to her, terrified and crying, and pleaded with her not to go. "There's something terribly wrong with me," he said. "I don't know what it is, but I think there's something eating my brain."

There was. He soon developed double vision that progressed to blindness. His body became wracked with tremors. He had trouble walking and even performing simple tasks like getting himself dressed. Dementia settled over him like a new skin. He saw snakes appear out of the air and believed himself to be a captain in command of a large boat. "He was lying in bed one night and he said, 'Can you see the stars?' It was the smoke detector," says Peggy. "I could still find him in there, but most of the time he was lost."

Finally, one day in August, he complained of a sore throat and simply stopped swallowing. At age 59, Ken Johnston was dead from Creutzfeldt-Jakob Disease (Croytz-felt Yawk-ohb), or CJD. This rare but inevitably fatal neurological disease riddles its victims' brains with microscopic holes and scar tissue, creating a spongy consistency in brain tissues. Undetectable until symptoms emerge, it is also incurable.

Tragic as Ken Johnston's death was, it was not extraordinary in a purely statistical sense. CJD kills at an annual rate of about one to two deaths per million people—more often, in fact than rabies. Washington state usually sees about five such deaths each year, according to the Department of Health. The condition is thought to arise from a genetic quirk, inherited in about 15 percent of the cases and occurring randomly in the rest.

In that respect, Creutzfeldt-Jakob is apparently a piece of the human condition. But unlike any other known genetic disease, CJD can also be infectious under the right circumstances. In the 1980s, British farmers unwittingly created those conditions by feeding diseased animals to dairy and beef cattle, creating an epidemic of bovine spongiform encephalopathy (BSE), or mad cow disease, a bovine version of CJD. The disease subsequently jumped to humans, killing 23 young Britons and a French citizen. Scientists have since raised the grim specter of a continent-wide brain-wasting plague whose victims could range into the millions.

In America, mad cow disease recently enjoyed publicity from the lawsuit Texas cattle ranchers pressed against talk show host Oprah Winfrey—who had the bad taste to badmouth burgers on a 1996 show—but it is generally not considered a domestic public-health threat. Aside from Oprah's tribulations, the media

ignore it. The government and livestock industry reassure us that mad cow disease isn't here.

If that turns out to be true, chalk it up to very good luck. For years, the US employed virtually the same rendering and feeding practices that precipitated the UK crisis. Although the federal government recently instituted new animal feed rules to prevent an American outbreak, the loopholes are large enough to drive through a herd of mad cows—or perhaps a pack of deranged pigs.

CREUTZFELDT-JAKOB DISEASE is a member of a family of mysterious diseases known as transmissible spongiform encephalopathies (TSEs). Spongiform disease has been recognized for centuries in sheep, as scrapie, while CJD was first diagnosed in humans in 1920. For decades, scientists considered CJD a hereditary condition and one that largely struck people over 60 years old. In the 1960s, however, that view began to change. Carleton Gajdusek, an American virologist who'd been studying a CJD epidemic among New Guinea cannibals, linked the outbreak to cannibalism. He later demonstrated that CJD could be experimentally transmitted to monkeys, and won the 1976 Nobel Prize in Medicine for his research.

Although the Nobel committee recognized the importance of Gajdusek's discoveries, few in England considered the implications when an epidemic of spongiform encephalopathies cropped up in British cattle in 1985. Infected cows grew nervous and agitated, often becoming aggressive, and thus inspiring the affliction's nickname, "mad cow disease." The barmy bovines deteriorated in the space of weeks, developing difficulty walking, then ultimately falling, unable to rise again.

By 1989, the British government had traced the BSE epidemic to rendered animal feed. In the UK, as in the US, the inedible portions of cattle—up to 40 percent of the animal—sheep, and other "waste" animals are sent to rendering plants where they are cooked and ground down to meat and bone meal, blood meal, tallow, and gelatin. Most of the animal protein is recycled into a scab-colored, granular protein supplement used to grow bigger, fatter cows, chickens, and pigs.

The government-appointed Southwood Committee, which investigated the outbreak, concluded that scrapie, which had been endemic in Britain since the 1700s, had somehow survived the rendering process to infect cattle. Many top TSE scientists, however, believe the disease arose from rendered bovine protein in cattle feed—from cow cannibalism, in other words. The UK began destroying infected herds and banned the sale of the most infective parts of the animal: the brains, spinal cord, and organs. The Southwood Committee's 1989 report concluded hopefully that culling infected herds would stop the epidemic and that there was no danger to humans from eating British beef. The report's authors noted, however, that "if our assessments of these likelihoods are incorrect, the implication would be extremely serious."

They were "incorrect" on a spectacular scale. The BSE epidemic continued to spread even after the slaughter of diseased cattle. By 1993, more than 80,000 cattle were infected, and 800 cows were falling ill each week. The disease spread to house cats and zoo animals through contaminated feed. Then young people, some as young as 15, started exhibiting strange neurological symptoms reminiscent of CJD, the disease of the elderly. One by one, their illnesses progressed inexorably to death.

Autopsied brain tissues revealed the microscopic holes and scar tissue indicative of CJD, though the pattern of damage looked more like the cattle version of the disease. Further testing revealed molecular markers linking the new human disease to the bovine spongiform encephalopathy raging in British cattle. The unthinkable had happened. On March 20, 1996, British Health Minister Stephen Dorrell told a stunned Parliament that 10 young Britons had died from a new variant of CJD (nvCJD), which they'd likely contracted from infected beef.

The magnitude of the British disaster is hard to grasp. Though only 24 victims have been identified to date, millions upon millions were exposed to large doses of the BSE agent, including tourists and US military personnel stationed in Europe at the time. Hamburgers—which, in the UK at the time, contained cattle brain for filler—are the most likely source of exposure. However, beef and dairy products cannot be ruled out. Nor can a prodigious assembly of other everyday consumer items, from candy to pharmaceuticals to cosmetics, that contain rendered cow in one form or another. Given the long incubation period for TSEs, from 10 to 40 years, it will be at least a decade before scientists can assess the true size of the epidemic. So far, epidemiological predictions, as the medical journal TheLancet puts it, range from "zero to millions."

"It is impossible to predict the size of the epidemic," says John Collinge, one of England's leading TSE researchers. "It may only involve hundreds, but it could be Europe-wide and become a disaster of biblical proportions."

In a March 1996 worst-case scenario, TheLondon Observer imagined a chain of government-run euthanasia clinics in the year 2016, helping 500 Britons a week die with dignity before the disease takes that from them.

THE BRITISH MAD COW CRISIS put an exclamation point on 40 years of TSE research. Originally, TSE appeared to be an exotic disease, posing little threat to those of us who don't dine on our neighbors. In the last three decades, though, the disease has crept progressively closer to industrial society. Hundreds of CJD cases have occurred through "high-tech, neo-cannibalism," as Carleton Gajdusek calls it, spreading the disease through contaminated tissue and organ transplants and human growth hormone. Last November, the Food and Drug Administration's TSE Advisory Panel learned that blood may carry the infective agent for CJD, raising a potential threat to the blood supply.

While the TSE threat is clearly no longer a problem solely of Stone Age tribes, modern medicine is still struggling to unravel its mysteries. "It is the first and only disease I know that is transmissible experimentally and occurs genetically," says Dr. Clarence Gibbs, who helped Carleton Gajdusek establish the US research effort in the 1960s and now directs the National Institutes of Health's TSE research. The enigmatic pathogen can withstand intense heat, boiling, freezing, drying, and radiation that would kill most known viruses and bacteria. The infectious agent doesn't appear to carry nucleic acid, the DNA or RNA that viruses use to replicate, and it is at least 100 times smaller than the smallest known virus. And yet, it can spread a disease that one relative of a British victim bitterly characterized as something not even Satan could dream up.

At the heart of the mysterious illness is a rogue protein, a normal body component that "undergoes some sort of a transformation and becomes pathogenic for the host," says Dr. Gibbs. The protein, dubbed a prion (rhymes with "neon") by University of California­San Francisco neurologist Stanley Prusiner, is ubiquitous, shared by yeast, humans, and likely everything in between. According to Prusiner's prion theory, which won him the 1997 Nobel Prize in Medicine, a random shift in the prion's molecular structure creates a lethal "seed" protein that can't be destroyed by the body and that single-mindedly converts healthy prions to the pathogenic form. In this fashion, the abnormal prion kick-starts a slow-motion domino effect, loading the brain with sticky protein deposits. As brain cells are smothered and die, they leave tiny holes and scar tissue that cause the brain's progressive dissipation. Abnormal prions from one host can also convince healthy prions in other hosts to convert to the diseased state, spreading the illness.

Human cannibalism is the most efficient way to start a human TSE epidemic, but it's not the only way. Prions are strikingly similar from species to species, enabling a TSE-infected animal to pass the disease to humans. All things being equal, the risk of finding a TSE on your plate would normally be very small. Making cannibals out of animals on a large-scale, though, ratchets up the risk considerably.

THE RECYCLING OF UNUSED animal parts into animal feed became widespread in the United States in the 1980s, according to John Stauber, a food industry watchdog and co-author of Mad Cow, USA (Common Courage Press, 1997). Currently, about 4 billion pounds of inedible animal parts are rendered each year, says Tom Cook of the National Renderers Association. The "raw product" comes from slaughterhouses, dead pets, roadkill, and restaurant grease. Roughly one-third of the rendered meat and bone product goes to pet food, another third to chicken farms, while 20 percent fattens pigs, and the rest is consumed by beef and dairy cattle.

The news that recycling animal corpses could produce an epidemic of fatal brain-wasting disease compelled the United States Department of Agriculture (USDA) in 1990 to assess the risks of BSE afflicting domestic cattle. The agency learned that rendering practices in the US and UK were virtually identical, raising the risk of transmitting the disease through animal cannibalism. In 1991, the USDA's Animal and Plant Health Inspection Service (APHIS) broached the possibility of a ban on using sheep and cattle in ruminant feed, but demurred because the "cost to the livestock and rendering industries would be substantial." It wasn't until October 1997, more than a year after the risks to humans became obvious, that the Food and Drug Administration (FDA) banned ruminant-to-ruminant feeding (though cow tallow and blood can still be fed to cows). "We'd been looking at this all along," says John Honstead of the FDA, explaining the decision's timing, "Once there was a known risk to people [following the British announcement], that was a factor in the feed-ban decision."

Government officials are quick to point out that the feed ban is preventive medicine. "In the US, we've found no evidence of BSE, or any TSEs in cattle," says Linda Detwiler, director of APHIS's BSE program. Since 1992, the agency has examined more than 6,000 brains of cattle suffering neurological symptoms. All the brains checked negative for BSE. "We remain confident that we don't have the disease here," says Gary Weber of the National Cattlemen's Beef Association. Weber argues that feeding animals on their own species isn't enough to develop an epidemic. "You have to have [the disease present] first."

Not all scientists are reassured. Dr. Gibbs of the NIH argues that sporadic TSEs probably occur at the rate of one to two per million in all mammals, just as in humans. If true, that would put the annual incidence of spontaneous cattle TSEs at somewhere between 100 to 200 per year in the US. Though Gibbs commends the USDA's monitoring program, "how many cow brains [out of a cattle population of 100 million] do you have to examine [to be statistically valid]?" he asks. Since US cattle are slaughtered at a younger age than their UK counterparts, it's possible that we may be killing the cows before they go mad.

Gibbs points to studies by the late Dr. Richard Marsh as strong circumstantial evidence that there is a domestic strain of cattle TSE that is significantly different from the British disease. Marsh traced several TSE outbreaks on US mink farms to feed made from "downer cows"—a "garbage can" category of cattle crippled by a multitude of conditions. He then infected healthy cows with the diseased mink brains, but they didn't display the typical "mad cow" symptoms used to diagnose British cows. Marsh's experimental bovines simply collapsed and were unable to get up. Examination of the dead cows' brain tissue revealed a different pattern of spongiform lesions than the English mad cow disease. "This is going to complicate our efforts at surveillance and testing for BSE in this country," Marsh said before his death last year.

There are as many as 100,000 "downer cows" in the US each year, an incidence that Dr. Marsh argued could mask the occurrence of TSE disease in US cattle. And although the feed ban has liberated cattle from cannibalism, today's cattle have only been cannibal-free since October (assuming full industry compliance—state and federal agencies have yet to implement feed-rule inspection programs). It will be several years before all the beef coming to market has been free of exposure to ruminant protein.

COW PROTEIN ASIDE, serious doubts remain about the effectiveness of the new feed rules. "It's a very narrow ban," says John Stauber, who notes that the rules still allow pigs, horses, and chickens to be fed on their own species under the assumption that these non-ruminants are not susceptible to TSE disease. That's a "grandiose assumption," according to Dr. Gibbs. "Since other mammalian species tested have the prion protein, they should in fact have their own spongiform encephalopathy."

A 1979 outbreak of a brain-wasting disease among more than 100 pigs at a New York packing plant suggests that bad prions afflict porkers, too. Recently examined slides of the diseased pig brains suggested a mad pig disease, although a firm conclusion was precluded by the limited samples saved from the outbreak. The FDA doesn't buy the mad pig diagnosis, arguing that the hogs likely suffered a more benign condition known as water deprivation/salt toxicity. "[The pigs] had some spongiform lesions," acknowledges Dr. Honstead, "but it was never shown to be transmissible." Honstead also points out that no one has ever observed pigs developing TSEs in natural conditions.

"Most commercial pigs are slaughtered at the age of 6 months, long before the pigs would [show symptoms]," argues Michael Hansen, a research associate at the Consumers Union, which has been advocating a tougher feed ban. Epidemiological studies have also suggested a disturbing link between pork consumption—primarily of hog brains—and Creutzfeldt-Jakob disease. Scientists have been able to experimentally transmit BSE to pigs, another indication they are susceptible to the disease. While similar efforts have failed with chickens, they, too, have prions and so are at least theoretically susceptible to prion disease. "It's a cannibal disease," says Stauber. "That's a no-brainer. If you keep feeding the dead of one species back to those animals, they'll develop it." And rendered pigs, chickens, and horses can be fed back to cows under the feed rules, opening a door for TSEs from those species to infect cattle.

Even more unsettling, the feed rules allow known TSE-infected animals to be used in feed for pigs, chickens, and farmed fish as well as pet food, opening the door even wider. In contrast, the European Union recently banned the use of any mammalian protein in animal feed, a measure the NIH's TSE advisory panel originally recommended to the FDA.

Without a full-fledged TSE epidemic on our hands, the FDA feels there is room to be more selective. "In Europe, in the face of the epidemic, they've banned everything," says Honstead. "Here, we're trying to reduce risk."

What no one can determine with any certainty, though, is the effectiveness of different levels of prevention short of a total ban on mammal protein in animal feed. Despite more than 40 years of research, the science on TSEs and prions is an open and largely unwritten book. "Given that there's a lot of the science that we don't know about the disease and how it's transmitted, the question is how careful we should be," says Jean Halloran of the Consumers Union.

For the time being, we'll dally with partial bans and uncertain risk reduction while the price of not being careful enough is slowly tallied in England. There, the unleashed prions are silently burrowing their way through the brains of an unknown number of future victims. An unappetizing thought if ever there was one.

Related Links:

The Official Mad Cow Disease Homepage

http://mad-cow.org/

 
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