Does giving antibiotics to animals hurt humans?
They've enabled doctors to cure deadly bacterial diseases like tuberculosis, typhoid fever and meningitis.
The FDA approved the use of antibiotics in livestock in the 1950s after studies showed that animals that got the drugs in their feed put on more weight in less time than animals on a traditional diet.
For example, pigs that got an antibiotic were shown to need 10 to 15 percent less feed to reach the same weight as pigs on regular diets. Since feed can account for as much as 70 percent of total animal production costs, the discovery was a windfall for farmers.
It meant they could produce more meat for less money, resulting in fatter profits.
But by the 1970s, researchers began warning regulators that routine use of antibiotics was contributing to a surge in drug-resistant germs, or superbugs, that render antibiotics powerless against deadly infections. Professor Stuart Levy of Tufts University conducted the first study in 1976 showing highly-resistant e. coli E. coli bacteria could pass from chickens to farm workers who worked with the animals in just a few weeks.
The study contributed to the FDA's decision to ban nonmedical use of penicillin and tetracycline in farm animals a year later. But farmers and drugmakers pushed back, and the FDA rule was never enforced.
"Why did no one act on it? Because there was a strong lobby," said Levy, who is co-founder and president of the Alliance for Prudent Use of Antibiotics, a nonprofit advocacy group that favors restrictions on the drugs. "They said, 'Well, show us the deaths. Show us the real problem. Otherwise, this isn't so terrible."
But it's difficult to link the overuse of antibiotics to deaths. It's tough to find the source of bacteria-resistant germs, which can spread from animals to humans through a number of ways, including undercooked meat and drinking water contaminated by animal waste.
And bacteria mutate when passing between species, meaning that the same strain of drug-resistant bacteria in chicken can take on a different form once it enters the human body.
While the issue mostly was tabled in the U.S., it was gaining momentum elsewhere in the world. In 1999, the European Union backed a ban on penicillin and other human antibiotics for growth in farm animals.
Within four years, the use of antibiotics on animals fell 36 percent in Denmark, 45 percent in Norway and 69 percent in Sweden. Levy, the Tufts University professor, and his colleagues had hoped that the EU's ban would bolster the case for restricting the use of antibiotics in the U.S.
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