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Public Radio's Environmental News Magazine (follow us on Google News)

Antibiotics, Livestock, and the Rise of Superbugs

Air Date: Week of

(United States Geological Survey)

Antibiotics are among our strongest defenses against infection and disease. But there's growing evidence that how we use the drugs in livestock could threaten the effectiveness of the medication in people. The vast majority of the antibiotics sold in the U.S. are given to livestock in low doses to promote growth. This might be creating superbugs: bacteria immune to the antibiotics people depend on. Living on Earth investigates.


GELLERMAN: It's Living On Earth, I'm Bruce Gellerman.

Last August, the giant food processing company Cargill voluntarily recalled 36 million pounds of contaminated ground turkey. The Associated Press had the story.

[AP REPORTER: This meat packaging plant in Springdale, Arkansas could be responsible for a nationwide outbreak of salmonella that has killed one person and sickened 77 others. The Agriculture Department and CDC say it’s one of the largest meat recalls ever, spawned from a dangerous strain of salmonella that’s resistant to some common antibiotics. ]

GELLERMAN: The salmonella bacteria was resistant to four kinds of antibiotics commonly used to treat poultry and people. But where the drug resistant bacteria came from, nobody really knows. It could have come from turkey farms, the processing plant, or someplace in between, though there’s growing evidence we created this deadly problem.

For more than 60 years, we’ve been feeding the animals we raise for food on a steady diet of antibiotics. It started by accident. Farmers were testing a newly discovered antibiotic called streptomycin. They found that even healthy animals, fed low doses of the antibiotic, grew fatter faster. And what had been an experiment has become common practice.

Today it’s estimated 80 percent of the antibiotics sold in the United States aren’t used to treat people, they’re bought by farmers. And 90 percent of the antibiotics they buy aren’t used to treat sick animals. The drugs are used to fatten their livestock. Dr. Gail Hansen is a veterinarian with the Pew Campaign on Human Health and Industrial Farming.

HANSEN: Every time you use an antibiotic, you can be potentially selecting for resistance. So that old saying of ‘whatever doesn’t kill you makes you stronger’ works for bacteria, too.

GELLERMAN: How does an antibiotic help an animal grow faster?

HANSEN: That is sort of the 64 million dollar question, I guess. There’s not been a lot of good, definitive studies on it. And, in fact, some of the times when they do studies and they have laboratory conditions, they can’t get that to happen. We do know that back in the 50s and 60s, when they first discovered that this was happening, they found that the animals grew better, sort of, the dirtier the farm was.

GELLERMAN: Dr. Hansen says farmers who feed small amounts of antibiotics - so called sub-therapeutic doses - to their healthy animals, can crowd and confine their livestock, saving space.

Denmark banned the practice back in 1995. The nation is the second largest exporter of pork products in the world and officials feared the use of sub-therapeutic antibiotics could breed superbugs - resistant to the drugs we use to fight infections in people.

Studies since the Danish ban demonstrate the prevalence of resistant bacteria has declined in food animals and retail meat, but only occasionally is there a decline in resistant bacteria in people. It’s perplexing. Here in the United States, though, Dr. Hansen says, studies show we’ve got a growing problem.

HANSEN: Our physicians are finding that they are running out of antibiotics to use, and that’s being found all over. And, we’re coming to a point where they’re…what’s being termed a post-antibiotic era - where the antibiotics that we have on hand aren’t working. And, as I said before, we have not a lot of new antibiotics coming down the pipeline.

GELLERMAN: According to the Infectious Disease Society of America, antibiotic resistant infections costs the U.S. healthcare system as much as 34 billion dollars a year and cause tens of thousands of deaths.

The Food and Drug Administration knows we’ve got a problem. Last year, the FDA came out with draft guidelines calling on farmers to voluntarily reduce the use of antibiotics in animal production. The FDA wouldn’t speak to us before the guidelines are completed, but here’s their spokesperson back in 2010:

FDA SPOKESPERSON: Misuse and overuse of these drugs contribute to a rapid development of resistance. FDA believes that using medically important antimicrobial drugs for production purposes is not in the interest of protecting and promoting the public health.

GELLERMAN: Now, the FDA has the authority to restrict the use of individual antibiotics and that’s what they did in 2005 when it ordered farmers to stop using the powerful antibiotic Cipro. Yet, despite the agency’s call for farmers to voluntary limit the use of the drugs, sales of agricultural antibiotics continue to rise.

But Dr. Liz Wagstrom, lead veterinarian with the National Pork Producers Council, thinks the FDA’s voluntary scheme is a solution in search of a problem.

WAGSTROM: Bottom line is though, we’ve got numerous peer-reviewed risk assessments that show that the risks to public health is vanishingly small.

GELLERMAN: But, sub-therapeutic doses, that suggests that you’re treating healthy animals that don’t need a therapy.

WAGSTROM: So, what we found out from many experiments when people have tried to take away those low doses of antibiotics, is that they truly are acting to improve the health of the animals, rather than just miraculously causing faster growth. And so, these animals are growing faster because they truly become and are healthier. If we phase out or ban growth promotion, there will be animal health consequences. We will have animals get sick and die, and likely not improve public health.

GELLERMAN: But according to the Centers for Disease Control and Prevention, the public’s health is under threat. Dr. Tom Chiller is associate director for Epidemiologic Science in the CDC’s division of Foodborne, Waterborne and Environmental Diseases.

CHILLER: There’s unrefutable evidence that using antibiotics in animals creates resistant bacteria in those animals. And we also know that some of those outbreaks and the people who get sick, get sick with resistant bacteria. The link is harder to establish because, as you can see, we need to be able to go from the farm to the fork, so to speak.

GELLERMAN: So, Dr. Chiller, to your mind, is the use of sub-therapeutic levels of antibiotics in animals - is that a threat to the public’s health?

CHILLER: Well, again, I think that the emergence of resistant bacteria is clearly a threat to the public’s health. And, I think that using antibiotics, misusing antibiotics or using antibiotics in non-judicious ways, is going to contribute to the development of that resistance.

GELLERMAN: So, I guess the question is, is the feeding of antibiotics to farm animals a judicious use of these drugs?

CHILLER: Yeah, that’s a good question - I mean, I think that … lets put it this way: we support the use of antibiotics in veterinary medicine to treat, control and prevent infections…

GELLERMAN: You’re stopping short because I don’t hear you saying ‘to grow animals faster.’

CHILLER: Yes. We don’t support the idea that an antibiotic should be used for anything but controlling, preventing and treating infections. And that’s what we need to reserve these drugs for and we feel strongly that that’s what they should be used for.

GELLERMAN: Judicious use of antibiotics. It comes down to how you define that term. But we can’t make an objective determination because we simply don’t have the data. That’s the conclusion of a recent Congressional investigation. The Government Accountability Office studied the FDA’s efforts to get farmers to limit the use of antibiotics voluntarily.

And Lisa Shames, director for Food Safety and Agriculture with the GAO, says there are big gaps, because government officials only gather sales data not information on how the drugs are used on farms.

SHAMES: What we’re looking for is more specificity in the data - for example what species are getting the antibiotics. We’re also looking for the use of the antibiotics - are they being used to treat a disease or are they being used simply to promote the growth of the animal? And these gaps really minimize our understanding of the relationship between the use of antibiotics in food animals and resistance in humans.

GELLERMAN: Meanwhile, in the absence of hard data, school kids in Chicago will soon be eating chicken drumsticks from birds raised without antibiotics. The Chicago Public School System, the nation’s third largest, has announced it’s going to start serving antibiotic-free chicken. But it will only be able to get a quarter of what it wants. The demand is high and there’s not enough drug-free chicken to go around.



The FDA’s 2010 announcement – Draft Guidance on the Judicious Use of Medically Important Antimicrobials in Food-Producing Animals.

Pew Commission Report on Farm Animal Production

CDC’s National Antimicrobial Resistance Monitoring System (NARMS)

U.S. Government Accountability Office report on Antibiotic Resistance.

*****Listen to a longer interview with Tom Chiller of the CDC****


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