Scientists worry about the overuse of antibiotics in people, but it’s our chickens, cows and pigs that are consuming the bulk of the germ-fighting drugs, a new study says. That concerns some epidemiologists who fear the practice could lead to a proliferation of super-resistant bacteria.
In a report released today, the Union of Concerned Scientists, an advocacy group focused on science and technology, estimates that livestock are fed eight times more antibiotics than people consume. By lacing livestock food and water with antibiotics, the scientists argue, animals become hosts to drug-resistant bacteria. Those hearty bacteria can then be passed on to humans who eat their meat or who come in contact with their waste.
“The excessive use of antibiotics by the livestock industry is sobering,” said Charles Benbrook, an economist and co-author of the report about the amount of antibiotics used by the livestock industry. “Feeding antibiotics to animals from birth to slaughter may modestly improve meat industry profits, but it puts everyone’s health at risk.”
Conflicting Figures on Livestock Consumption
According to the report, 25 million pounds of antibiotics — or roughly 70 percent — of total U.S. antibiotic production are fed to animals to promote growth and disease resistance. That use has climbed from 16 million pounds in the mid-1980s to 25 million pounds today, according to the study’s authors. By comparison, humans consume only 3 million pounds of antibiotics a year.
Livestock industry representatives claim such figures are inflated. A study recently released by the Animal Health Institute, an industry group, stated that antibiotic use in the livestock industry was 17.8 million pounds — or about 50 percent less than the estimates by the UCS.
“We think their figures are greatly over-calculated,” says Carole duBois, vice president of public affairs at the Animal Health Institute. “Their estimates are based on indirect data ours are directly from the manufacturers of the product.”
Livestock producers also argue use of the drugs is legitimate for providing safe and affordable meat and poultry. And duBois says many of the drugs the UCS lists in their report are used exclusively in animals and therefore have little impact on humans.
“Use of these drugs prevents and treats disease in animals and a healthy supply of meat and poultry is good for people,” she says.
Tracing the Problem
Still, scientists who authored the new report point to Europe, where several antimicrobials that are important in human medicine are banned from use in agriculture. These medicines include penicillins, tetracyclines and streptogramins. Authors of the UCS report say the U.S. livestock industry uses about 13.5 million pounds of such drugs for healthy cows, pigs and livestock every year.
By sharing human antimicrobials with livestock, researchers fear the medicines will be rendered ineffective for people as new, medicine-resistant strains of bacteria develop in livestock.
So far evidence that the problem exists is thin. University of Illinois microbiologist Abigail Salyers says she only knows of one case of people dying when an antibiotic, also used in agriculture, failed to work. The 1999 case occurred during an outbreak of salmonella in Europe and was mentioned in the New England Journal of Medicine.
But Salyers says that researchers have only recently developed the means to trace the origins of disease through DNA fingerprinting.
“There are now ways of fingerprinting certain strains of bacteria that make it possible to trace cases,” says Salyers. “But people have just started looking. The fact that there’s one known case, doesn’t mean it’s the only case.”
Poultry Drugs Already Banned
Last October, the Food and Drug Administration announced plans to ban two antibiotics used by poultry farmers. The antibiotics, known as fluoroquinolones have been available to people since 1986 and are often prescribed for dire gastrointestinal illnesses. The same drugs have been fed to turkeys and chickens since the mid-1990s but now companies will need to challenge the FDA ruling in order sell them for livestock.
Margaret Mellon, director of the Food and Environment Program at UCS says her group is not necessarily arguing for immediate bans of antibiotic use in livestock, but for increased monitoring. Her group argues the government should require all companies selling antibiotics for livestock to file annual reports about the quantity of drugs sold.
“The public has been flying blind,” she said. “The government should act now to collect the needed data. The price of complacency could set us back to an era where untreatable infectious diseases are regrettably commonplace.”