Consumer advocates have been campaigning for years to curb the use of antibiotics in agriculture, citing studies that show that 70 percent of all U.S. antibiotics are administered in low doses – not to treat disease, but to promote the growth of pigs, sheep, chicken and cattle.
Low doses of antibiotics in animal feeds have been shown to boost the speed of food-to-muscle conversion by 5 percent, and can prevent the spread of disease in the tight quarters of modern factory farms.
But as early as 1963, British researchers tied the emergence of drug-resistant strains of salmonella in humans to antibiotics fed to cattle. Among the drugs routinely found in animal feed are erythromycin, penicillin and streptomycin. Critics warn that the use of antibiotics in feed at low dosages helps to breed resistant bacteria in the gut of farm animals – threatening the future of these drugs for use in animals or humans.
Major antibiotic classes such as tetracyclines and the Cipro-like fluoroquinolones have already been compromised, according to Keep Antibiotics Working, a coalition backed by environmental groups and the American Medical Association.
The stakes are high. The Union of Concerned Scientists calculated in 2001 that U.S. farm interests were using 24.6 million pounds of anti-microbials – almost 40 percent higher than industry estimates.
Ron Phillips, vice president of the Animal Health Institute, a Washington trade group for agricultural drugmakers, maintains that growth promotion accounts for only 4.5 percent of antibiotic consumption in agriculture. The rest are used to prevent, treat or control the spread of disease. “Antibiotics,” he says, “are a net positive for both animal health and human health.”
After antibiotics were banned from animal feed in Europe beginning in 1995, Phillips said, farmers there found they had to use more antibiotics to care for illnesses that cropped up in their livestock.
Keep Antibiotics Working nevertheless is pushing for a federal ban on antibiotics in feed. Introduced by Sens. Edward Kennedy, D-Mass, and Olympia Snow, R-Maine, the “Preservation of Antibiotics for Medical Treatment Act” would phase out in two years antibiotics deemed “important in human medicine.”
In response to pressure from consumer groups, McDonald’s declared four years ago its intention to phase out the purchase of meats from chicken and livestock fed the drugs to promote growth. The Food and Drug Administration in 2005 banned the use of a Cipro-like drug, Baytril, to treat bacterial infections in poultry, after drug-resistant strains of Campylobacter – a common food-poisoning organism – were found in chicken. Cases of Cipro-resistant Campylobacter were also rising in humans.
The FDA is considering an application for approval of the antibiotic cefquinome, a proposed veterinary drug that is similar to the human drug cefepime. In the fall of 2006, an FDA advisory committee recommended against approval.
“It was surprising what the committee did, because it was stacked with veterinarians and animal science people,” said Stephen Roach, director of public health programs for Keep Antibiotics Working.
“The USDA is very reluctant to say that antibiotic use causes a problem, and the FDA has traditionally been in the middle. But I feel that in the last several years, they have been more accommodating to industry,” said Roach.
A final decision on approving cefquinome is still pending.