Even as a growing number of people — from consumers to scientists to physicians — expressed concerns about the overuse of antibiotics in animal feed, a new FDA report shows that farmers continued adding more drugs to their animals’ diets, and that almost every one of those antibiotics was purchased and administered without a prescription.

Antibiotics given to farm animals already account for around 80% of all antibiotics sold in the U.S., and according to the FDA’s latest report [PDF, between 2009 and 2012, the total quantity of just those antibiotics deemed medically important to humans that were sold or distributed for use in food-producing animals increased by 16%.

More than two-thirds (67%) of the medically important drugs fed to animals in 2012 were tetracyclines, which are used in humans to treat everything from urinary tract infections to chlamydia to Lyme disease, but whose use has declined because of the prevalence of drug-resistant bacteria.

Various forms of penicillin accounted for 11% of these drugs, macrolides — used to treat strep, pneumonia, staph infections and other ailments in humans — made up 7% of the drugs fed to animals, while sulfonamides (6%), aminoglycosides (3%), lincosamides (2%), and cephalosporins (less than 1%) brought up the rear of the drug train.

The FDA gives no specific reason for the jump in sales of these important antibiotics. But even if, as the drug and livestock industry now claims, these antibiotics are being used judiciously and for disease prevention, only a tiny fraction of them are actually prescribed by veterinarians.

During the same three-year time period in which sales increased by 16%, the FDA says that the percentage of medically important antimicrobials sold over-the-counter to farmers effectively remained flat at around 97%.

And the FDA data seems to call shenanigans on this “disease prevention” mantra that the industries trot out to defend their use of antibiotics. In 2012, antibiotics with a proven use for growth-promotion outsold antibiotics with only a therapeutic use by a ratio of 2.2:1.

Congresswoman Louise Slaughter from NY, a vocal opponent of the use on antibiotics in farm animals, says that the FDA report backs up warnings from the scientific community about the too-frequent use of these drugs.

“We know that the overuse of antibiotics on the farm is leading to more antibiotic resistant pathogens that threaten humans – and FDA’s own figures show that the agency’s inaction is making the problem worse,” Rep. Slaughter said in a statement. “Twenty-three thousand Americans die every year from antibiotic-resistant pathogens, and until the FDA enacts a mandatory regulation that puts human health before industry profits, Americans will continue to live under an increased threat of untreatable infection.”

“Antibiotic use in U.S. livestock is huge and continues to escalate, even while many leading meat exporting countries have halved their livestock usage,” says David Wallinga, MD, from Keep Antibiotics Working. “If the White House and the Department of Health and Human Services are serious about addressing the threat to the American public from worsening resistance, it cannot adopt a ‘wait and see’ stance. It must push the U.S. livestock sector to lead, not follow in reducing use of precious antibiotics.”

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