Two weeks ago, I broke the news of a new FDA report that estimated for the first time the amount of antibiotics sold in the United States every year for use in agriculture: 28.8 million pounds.

That long-awaited report didn’t answer a crucial question: What volume of antibiotics are sold in the United States each year for human use. It’s a crucial question because, in answer to concerns about antibiotic resistance arising on farms, the answer has always been that human medicine is equally culpable because it uses similar volumes of antibiotics.

The only research that has attempted to answer that question is contained in a decade-old report by the Union of Concerned Scientists that put the proportion of antibiotics going to animals at 70 percent of the U.S. total.

That UCS report and estimate are a decade old not because no one has cared about the topic, but because accurate updated figures have been so hard to get. So we owe a special holiday thank-you to the researchers at the Center for a Livable Future, who decided the release of the FDA report justified another attempt to get the numbers straight. They succeeded.

The proportion of antibiotics sold in the United States each year that go to animals turns out to be not 70 percent, but rather 80 percent. Here’s CLF’s Ralph Loglisci, who got the confirmatory numbers from the FDA:

In accordance with a 2008 amendment to the Animal Drug User Fee Act, for the first time the FDA released last week an annual amount of antimicrobial drugs sold and distributed for use in food animals. The grand total for 2009 is 13.1 million kilograms or 28.8 million pounds. I … contacted the FDA for an estimate of the volume of antibiotics sold for human use in 2009. This is what a spokesperson told me:

“Our Office of Surveillance and Epidemiology just finished an analysis based on IMS Health data. Sales data in kilograms sold for selected antibacterial drugs were obtained as a surrogate of human antibacterial drug use in the U.S. market. Approximately 3.3 million kilograms of antibacterial drugs were sold in year 2009. OSE states that all data in this analysis have been cleared for public use by IMS Health, IMS National Sales Perspectives™.”

3.3 million kilograms is a little over 7 million pounds. As far as I can determine, this is the first time the FDA has made data on estimates of human usage public.

At its blog, CLF lays out the math for each major drug class as sold for animal use and human use, with a long discussion of the significance of the different drug classes. Here’s the CLF table summing up the math, but please go over to CLF’s blog for its discussion.

Most important to note: Most of the drugs used in animal agriculture and in human medicine are functionally identical. That’s one reason why the overuse of antibiotics in animals is such a concern: When organisms become resistant on the farm to drugs used on livestock, they are becoming resistant to the exact same drugs used in humans. (One major drug category used in animals, ionophores, do not have a direct human analog. But use of them on farms is still a concern, because resistance factors can move freely between species of bacteria. That’s a discussion for another day.)

Loglisci’s conclusion is also worth underlining:

The next battle, which industry has already begun, is defining what non-therapeutic use will constitute. Producers are already claiming that the use of antibiotics for growth promotion has decreased, maintaining current low-dose usage is aimed at disease prevention. Regardless, all low-dose usage of antibiotics can lead to a significant increase in antibiotic resistance.

Image: Flickr/Epsos

This afternoon, the Food and Drug Administration posted without fanfare a report that many people have been waiting a long time for: Its first-ever estimate of the amount of antibiotics sold for use in food animals in the United States.

And the number is: almost 29 million pounds in 2009.

That’s a lot.

Is it more or less than was expected? It’s almost impossible to say. Estimates of the amount of antibiotics given to food animals in the United States are ferociously contested and plagued by squishy definitions and category creep. In 2000, the Animal Health Institute, which represents veterinary drug manufacturers, put total use at 17.8 million pounds. In 2001, the Union of Concerned Scientists, which campaigns (among other issues) to dial back use of agricultural antibiotics, estimated that 24.6 million pounds per year are used only for “non-therapeutic purposes” — that is, to make animals grow to market weight faster and to prevent them catching diseases in the close quarters of confinement agriculture.

The reason why antibiotic use on farms is a concern, of course, is because such use stimulates the emergence of drug-resistant organisms that move off the farm in animals, in groundwater, in dust, on the wind and in the systems and on the clothes of those who work there, and makes new resistance factors available to be swapped among bacteria. (For much more about that, see these three posts and this long archive at my former blog.)

The FDA’s estimate comes as the agency has been moving to curb agricultural antibiotic use after years of non-action. Today’s report, which is very short — basically a table and a bunch of footnotes — is the direct result of a 2008 amendment to the Animal Drug User Fee Act of 2003, which required manufacturers to report yearly on sales of agricultural antimicrobials. (Here’s an FDA Q&A on the report background.)

More important, though, today’s report dovetails with the FDA’s new effort to curb antibiotic use in agriculture, which Commissioner Dr. Margaret Hamburg said in October would involve “very serious scrutiny.” (Video here.) The main instrument of that effort is a “draft guidance” that the FDA opened for public comment over the summer, “The Judicious Use of Medically Important Antimicrobial Drugs in Food-Producing Animals” (pdf here). The point of that guidance is to ask agriculture to voluntarily withdraw from use the ag drugs that are functionally identical to drugs that are important in human medicine — because if bacteria become resistant to those drugs when they are used in animals, that newly derived resistance will also affect humans, making common diseases difficult or impossible to treat.

In addition to the volume figure, the real value of today’s brief report may be simply to make clear just what antibiotics are used in agriculture. Take a look at the report table at right, which lists the animal drugs used by amount sold within drug classes. (Note that the amounts are given in kilograms.) It lists:

Aminoglycosides: Human versions include streptomycin and amikacin.

Cephalosporins:  Human versions include Keflex and Rocephin.

Lincosamides: Human versions include clindamycin.

Macrolides: Human versions include erythromycin.

Sulfas: Human versions include half of the very common drug combos Bactrim and Septra.

Penicillins and tetracyclines: Yup, just what they sound like.

“NIR”: That’s FDA shorthand for “not independently reported” because they have few manufacturers or make up a small portion of the market. Among them are fluoroquinolones. Human versions: Cipro and Levaquin.

There’s much more to be said about the issue of antibiotic use in agriculture, especially because the lone piece of legislation addressing it, the Preservation of Antibiotics for Medical Treatment Act, is currently in lame-duck limbo. This report is an important piece of data for the ongoing debate.

Update: I asked some experts in the field to comment on the release of this data. Dr. David Wallinga, director of the Food and Health program at the Institute for Agriculture and Trade Policy in Minneapolis (also William T. Grant Foundation Distinguished Fellow in Food Systems and Public Health at the University of Minnesota School of Public Health) replied:

Clearly, antibiotic use in animal agriculture is huge, and as the FDA and CDC and WHO all agree, much of it is unnecessary. Data collection is important. But, because resistant bugs quickly adapt, we can’t afford to wait for data to take action to reduce antibiotic use wherever possible. That includes routine uses of antibiotics for cattle developing liver abscesses because they’re force-fed grain rather than grass, as well as antibiotics used to make animals get fatter faster.

Update 2: A day after the release of this report, Rep. Louise Slaughter (D-NY), author of PAMTA and a public-health microbiologist, commented on the data — and also said she’ll be reintroducing the legislation again in the next Congress in January.

This report illustrates the overuse of antibiotics in food animal production and makes a strong case for some common-sense limits on antibiotic use. We are putting millions of pounds of antibiotics into the food supply unnecessarily every year. This cannot continue and it’s my hope that these new data from the FDA will encourage even more members of Congress to join me next year when I reintroduce this legislation.  Moreover, the FDA must move fast to issue strong regulations on antibiotic usage in agriculture.

Update 3: Tom Philpott, senior food and agriculture writer at Grist — and a farmer, so he knows the territory — covered the FDA report and this post in a very kind and typically forthright post of his own.

Update 4: Helena Botttemiller, ace food-policy reporter for Food Safety News, covers this as well, noting how little mainstream media interest there has been. Any opinions why?

Cite: 2009 Summary Report on Antimicrobials Sold or Distributed for Use in Food-Producing Animals, FDA, Dec. 9, 2010

Image via Flickr user net_efekt under CC