Could Mad-Cow Disease Happen Here?

Britain's horrifying experience taught us a few things, but perhaps not enough to preclude an outbreak of our own

THE recent British epidemic of mad-cow disease, and the twenty-seven cases of fatal human disease associated with it, have led to the slaughter of 3.7 million cattle and the near destruction of Great Britain's cattle industry. Observers have suggested that the outbreak was a factor in the toppling of John Major's Tory government. Mad-cow disease continues to haunt Britain, and Europe in general, even though the European Community, having made extraordinary efforts, appears to have contained the outbreak. The latest figures show that the incidence of the disease in Britain is less than a tenth what it was at the epidemic's height, when more than a thousand new cases were being diagnosed in cattle every week. Still, the pummeling of the British beef industry continues. Last December the British government banned the sale of most cuts of beef on the bone, including ribs, T-bone steaks, and oxtails. With (as of this writing) a worldwide ban on British beef exports, and a severe decline in domestic sales, the price of British beef has fallen to its lowest level in twenty years. Cattle tainted by association with the disease are quickly disposed of.

A similar epidemic in the United States would be even more catastrophic. Britain before the outbreak had roughly 10 million cows; we have more than 100 million.

Cattle and dairy farmers are at the heart of thousands of rural economies, and earn approximately $54 billion a year through meat and milk sales; more than $100 billion in additional revenue is generated by related industries and services. No wonder, then, that when the British epidemic hit the front pages, two and a half years ago, the U.S. government reacted emphatically. The Food and Drug Administration, the Centers for Disease Control and Prevention, and the United States Department of Agriculture rallied to reassure us that there was no sign of the disease in this country. Yet most of the conditions thought to have led to the epidemic in Britain also existed here. Despite official protestations to the contrary, and despite regulatory changes recently implemented, some of them still do. Given current agricultural practices, avoiding an American outbreak of this disease may be only a matter of chance. The question is, how lucky do we feel?

As those who followed the horrifying unfolding of the British epidemic will recall, mad-cow disease is one in a category of progressive neurological disorders called transmissible spongiform encephalopathies (TSE). The fatal human nervous-system disorder Creutzfeldt-Jakob disease, or CJD, is also among these, and the panic in Britain began when a new variant of this gruesome affliction was discovered in association with mad-cow disease. Many things about TSE in general, and the relationship between mad-cow disease and CJD in particular, remain unclear. But that's hardly reassuring. The chain of reasoning that should make us worry begins with the fact that the economics of our modern meat and milk industries dictate that many farm animals get food supplements derived in part from rendered animal protein. The rendered animal protein they eat may expose them to the TSE infectious agent, which is thought to have the potential to cross the species barrier between animals, even into human beings. TSE is 100 percent fatal, and in human beings takes up to thirty years to manifest symptoms. Thus if, however unintentionally, we encourage the spread of TSE infection, a great deal of damage will be done before we have visible signs of the problem.

It makes sense, then, that if we make mistakes in our efforts to prevent a new variant of CJD in this country, they be mistakes on the side of caution—perhaps a higher degree of caution than we have so far exhibited.

Economies of Scale

IN the United States, as in Britain, most dairy and cattle farmers are small entrepreneurs struggling to maintain a fading way of life. Larry Johnston, a seventy-four-year-old dairy farmer in Corvallis, Montana, has engaged in this struggle for more than thirty years.

When we met, one overcast morning in June, Johnston was crisply dressed but tired. Over breakfast he told me that he'd spent the previous six hours helping a cow to deliver its first calf. Birthing calves was not the way he'd planned to spend his retirement years, he said, but there was no way around it. His daughter and son-in-law were on vacation, and the hired help, though reliable, could not handle a difficult delivery. "We're just grateful that they show up," he said. "You can't demand professionalism at five dollars an hour."

Johnston would like to pay more, but he can't. Rummaging through a pile of papers, he found a balance sheet and ran a finger down the columns. The farm had lost $57,684.30 in the previous ten months. "My accountants tell me I have one smart choice," he said. "That's to sell this place and retire to a beach in Hawaii."

From the look of things, Johnston and his family have done just about everything to make their 112-acre operation pay, including feeding their cattle scientifically. Each cow's ration is determined using a formula that takes into account its weight, age, and milk output. This information is coded and integrated into a computer chip embedded in a blue tag that the cow wears on a necklace. Johnston walked me down to the feedlot for a demonstration. A six-month-old calf stood in a pen, its blue tag dangling. A computer read the tag, deciphered its message, and dumped precisely the amount and kind of feed the calf had coming to it. The setup reminded me of something out of The Jetsons, the science-fiction cartoon. It also looked like an extravagance—but Johnston told me otherwise. Without this precision he'd be out of business. He said that when he became a dairyman, a good milking cow gave maybe thirty-five pounds of milk a day. Today that cow, if healthy, would immediately be sold at auction and ground into hamburger and franks, as all healthy dairy cows are eventually.

"Our top milkers give up to a hundred and thirty pounds of milk a day," Johnston said. "We feed the best alfalfa we can buy, from Townsend, Montana, or Mud Lake, Idaho, or eastern Washington State. A company representative [from Purina Mills] works out the formula depending on the quality of our hay. And we have a special high-power supplement for the high-producing cows."

Johnston had paid $69,581.57 for feed supplements in the previous ten months alone, but he figured it was money well spent. Without the supplements, he said, milk production would slow down and his balance sheet would look even worse. He has seen a lot of farms go under. From 1987 to 1996 the number of milk-cow operations in the United States dropped by 44 percent, and the number of cows by 11 percent, while milk production increased by eight percent. Breeding, hormones, and drugs have made America's dairy cows veritable milk machines—hungry machines. I asked Johnston for a look at the supplement, and he took me to a side barn, where a pile of it spilled out from under a blue tarp. It looked like rabbit food and smelled vaguely of grain and dung. I asked him what was in the stuff, and he said that he wasn't sure but he knew why I was asking. "You want to know if I'm feeding cow to my cows," he said. "Truth is, I don't know."

A call to Johnston's supplier, Bill Shine, who at the time was the local district manager for Purina Mills, determined that the feed was custom-made for Johnston's cows, of soybeans and canola, animal fats, meat-and-bone meal, and blood meal. Shine didn't seem to know whether the meat-and-bone meal came from cows, but he did say that "regulatory issues" would prevent the inclusion of beef in cattle feed in the future. Two months after my visit to Johnston the U.S. Food and Drug Administration banned the practice of feeding to cattle or sheep almost anything containing the meat, bone, or fat of mammals other than pigs and horses (exceptions made because the FDA contends that these animals don't get TSE). Some observers are skeptical of this ruling, in part because the FDA has allotted the equivalent of only seventeen full-time inspectors to 14,000 facilities involved in feed production and rendering—the process by which animal by-products, such as meat, bone, and fat, are melted down and separated. Another objection is that the feeding of cows' blood to cattle continues to be permitted. Although TSE in human beings has not been shown to be transmitted by blood, evidence of TSE has been found in the blood of experimentally infected animals.

The skeptics argue, too, that there is no way to prove that the species barrier cannot be surmounted, and the current rules allow even animals known to be infected with TSE to be fed to pigs and chickens, which can in turn be fed to us. Or they may be fed to cattle and sheep. A study published in April in the scientific journal Nature found that TSE from one species can be carried by another species without making the carrier sick. The authors concluded that "the results presented here would strongly favour a decision to stop feeding ruminant-derived products to all animal species"—in particular, "domestic animals such as poultry which are raised for human consumption."

American dairy farmers have fed their herds supplements containing fat, bone meal, and blood and meat protein for fifty years or more. Larry Chase, an associate professor of dairy-cattle nutrition at Cornell University, says that cows fed on grass, hay, alfalfa, and other forage produce just ten to fifty pounds of milk a day, and that "you can't get a reasonable amount of milk without supplement." Protein supplements can be made from almost any organic material, including corn and soybeans. They may also contain rendered animal by-products. When I called him, Chase took a minute to check the commodities market and found that animal by-products were going for about the same price as soybeans that day. Since animal products deliver more protein per ounce than vegetable products do, it's no surprise that many farmers have turned to animal-based food supplements. "The amount of rendered animal protein produced in this country is staggering," Chase said. "And from what I understand, ten to fifteen percent of it goes into cows"—an estimate that he believes holds true today.

Feeding cow to cow may sound bizarre, but from a nutritional standpoint it makes perfect sense. Richard Race, a research veterinarian at the National Institutes of Health's Rocky Mountain Laboratories, in Hamilton, Montana, explains that animal protein is more complete than most vegetable proteins, and that the best protein an animal can eat, metabolically speaking, is derived from the tissues of its own species. "Theoretically, the best protein for a dog is dog, for a cat is cat, and for a cow is cow," he says. "For that matter, the best protein for humans is human." Donald Beermann, a professor of animal science at Cornell, observes that feeding animal protein to cows significantly accelerates their rate of growth. And, he says, animal activists are wrong when they claim that cows are strict vegetarians. "It's not uncommon for a cow giving birth in the field to eat its placenta," he says. "Makes sense. Nature is not in the practice of wasting valuable nutrients."

One may well ask, then, why most mammals approach cannibalism as, at best, a last resort. Why, for example, don't competing males kill and eat one another, and why don't most mammals eat their dead? Scientists can only speculate that such behavior bodes ill for a species' long-term survival. Disease spreads more easily within than among species, and a species that eats its own has a higher risk of being killed off by disease. Cannibalism also amplifies levels of infectious organisms, concentrating and increasing their presence in the environment and spurring their chances of hurdling the species barrier and moving into another, related species. A microbe that normally infects sheep fed repeatedly to, for example, cows may mutate in order to accommodate to its new host, thereby becoming the agent of a cow disease. This is why the Food and Drug Administration has banned the feeding of most mammals to cows or sheep and other ruminants and has stipulated that feed derived from ruminants bear the warning label "Do not feed to cattle or other ruminants." Rendered products of cow and sheep carcasses will, however, continue to be manufactured and labeled as feed for hogs, chickens, and other farm animals—a practice forbidden in Europe in 1996, when it became clear that material labeled pig or chicken feed was finding its way into cows and sheep. Gloria Dunnavan, the director of the Division of Compliance at the FDA's Center for Veterinary Medicine, says that although the agency is looking for 100 percent compliance on the regulation, it is not 100 percent optimistic. "We've developed an enforcement strategy, but it's been quite a challenge," she says. "Not a lot of people in the rendering and feed industry are used to seeing an FDA presence. But the groundwork is being laid, and to date we've received a lot of cooperation from the industry."

In his 1978 book Rendering: The Invisible Industry, Frank Burnham, the editor of Render magazine, described his business as having been "almost invisible for more than 150 years quietly doing its thing on the back streets of America." Indeed, today it is very difficult for a journalist to gain entrance to a rendering plant, but a clandestinely made videotape of a sampling of plants, which was provided to me by the Government Accountability Project, a public-interest law firm in Washington, D.C., portrays a series of altogether unsavory places where dead cats and dogs, road kill, the occasional circus animal, and the diseased carcasses of farm animals are mixed into a ghastly, belching stew.

Swift and Company, the Chicago meatpacker, was the first to mass-manufacture rendered protein and fat as animal feed, at the turn of the century, but the use of such feed really took off in Britain during the Second World War, when it became difficult to import vegetable feeds from abroad. In Britain cows were fed as much as four pounds of rendered protein a day, but in the United States, where soybeans and other vegetable proteins were plentiful, the use of rendered animal protein as feed was far less common. By the mid-1970s, however, the price of vegetable protein in the United States had risen to the point that rendered animal protein became an increasingly popular cattle feed—though never as popular as it was in Britain.

Then the energy crises hit, and the rendering industry sought to process material at lower temperatures and, in England, with smaller amounts of costly and dangerous petroleum-based solvents (solvents are not used in the United States). What it came up with was a vacuum system—a neat trick that those who recall fifth-grade science class will understand immediately. Heating water in a vacuum allows it to boil at lower temperatures. The vacuum system, though it is effective for rendering, unfortunately does not destroy all bacteria or viruses or, for that matter, the infectious agent associated with mad-cow disease. A study published in The Veterinary Record in December of 1995 reported that when neurological tissue infected with mad-cow agent was put through this process, the level of infectivity showed no reduction after rendering, whereas the old-fashioned high-temperature method reduced infectivity significantly. According to sources in the rendering industry and at the USDA, low-temperature rendering without solvents could well have led to the mad-cow outbreak in Britain, and it certainly has the potential to spread infection in the United States if the disease occurs here.

"Before the 1970s there was a reduction in infectious material by at least a factor of a hundred using the standard rendering system," a scientific consultant told me. "But the new low-temperature systems did nothing to reduce infection. In England sixty to seventy percent of rendering plants switched to the low-temperature system by the early 1980s. And in the United States anywhere from one quarter to one third of all rendering plants still use the low-temperature process."

This consultant, who declined to be named, warned that low-temperature rendering combined with the American practice of putting diseased animals into the rendering cycle was a potential threat to the public health. Although a voluntary ban has been instituted on rendering the carcasses of animals condemned for signs of neurological disease, critics worry that such a thing cannot be completely effective—especially because many animals are not examined by a veterinarian before being rendered. "If there's one industry within agriculture or food production that needs regulating in this country, it's the rendering industry," the consultant said. "The number-one World Health Organization recommendation to prevent the spread of TSE was a ban on the use in the food cycle of animals that show signs of TSE disease. Yet the FDA completely missed that recommendation, and TSE-diseased animals can still be in there. If you're going to process animal materials, you need minimum processing conditions—for example, a standard of temperature that will kill all infectious agents. And I don't see them doing that at all."

Presented by

Ellen Ruppel Shell is the co-director of the Graduate Program in Science Journalism at Boston University. She is the author of Cheap: The High Cost of Discount Culture.

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