Growing Resistance

Is agribusiness squandering one of medicine’s most potent weapons?

For years public health officials have been sounding the alarm about drug-resistant diseases, to little effect. Today some strains of tuberculosis, pneumonia, and gonorrhea are resistant to multiple antibiotics, and a few pathogens are impervious to all drugs — including what physicians refer to as “the last big guns,” powerful antibiotics like vancomycin and quinolone.

Fearing a national health crisis, an array of federal agencies, including the Centers for Disease Control and Prevention and the Food and Drug Administration (FDA), last June released the first draft of an action plan. But while the report’s suggestions for curbing overprescription and overuse of antibiotics met with broad approval, critics say it failed to tackle another problem: the use of medically important drugs as “growth promoters” in livestock. “When it comes to agriculture,” says Karen Florini, senior attorney for the New York-based advocacy organization Environmental Defense (ED), “it’s an inaction plan.”

Why the ruckus? For decades, farmers and ranchers have known that livestock, especially poultry and hogs kept in factory-farm conditions, grow faster when their food is spiked with small doses of antibiotics. As early as the 1970s, scientists warned that such “subtherapeutic” use could cause bacteria to develop resistance to the drugs and that humans were likely to ingest those microbes via contaminated meat or water. By the late 1970s the FDA advocated a ban on feeding two common drugs to livestock. But the agency withdrew its proposal amid opposition from the agricultural industry, and the practice has continued unchanged ever since. Today, estimates the Center for Science in the Public Interest, about 40 percent of the antibiotics used in the United States are fed to animals.

What has changed in the intervening years is the amount of evidence linking resistant forms of infectious disease to farming practices. In one of the most striking examples, Danish doctors in 1998 encountered patients infected with a strain of salmonella known to be resistant to five antibiotics. Typically, the pathogen is treated with one of the big guns, a form of quinolone. But in this case, the drug was significantly less effective. The infections were traced back to a herd of swine from a farm where another quinolone had been used. Tests showed that the meat carried salmonella bacteria with the same drug-resistance genes as the salmonella in the patients. In all, 25 people were afflicted. Two died.

“Acquiring genetic resistance is a natural phenomenon,” says Dr. David Wallinga, of the Institute for Agriculture and Trade Policy (IATP), a Minneapolis-based advocacy group. “Now that process is becoming highly accelerated. And if these resistant strains become widespread, there’s not much we’ll be able to do.”

The urgency of the situation was underscored last year when the General Accounting Office reported that many experts now blame growth promoters for the development of resistance in certain organisms. Outside the United States, public health officials have already taken steps to combat the problem. In 1997, the World Health Organization recommended that drugs used in human medicine not be fed to animals to promote growth. The European Union followed suit in 1998, banning the agricultural use of four major antibiotics. Sweden and Denmark did the same.

When last summer’s interagency draft plan failed to follow the European example, a number of groups, including ED, IATP, the Union of Concerned Scientists, and Physicians for Social Responsibility, mounted a protest. The organizations have called for a ban on the use of medically important antibiotics as growth promoters. But opposition to such a measure remains strong. The Department of Agriculture takes the position that more research is needed, as does the pharmaceutical industry.

Although the period for public comment on the draft plan has ended, Wallinga and others promise to push for a more stringent approach in the final plan, expected to be released next year. “These drugs are too important for human health,” he says, “to risk using them to fatten chickens.”


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