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A little ammo

More and more, I run into self-proclaimed experts expounding on antimicrobial use in food animals. I don't suggest the food-animal industry doesn't have a few issues to deal with, but a large proportion of what I see is based on data the reporter/activist doesn't understand or is flat-out false.

For instance, the Union of Concerned Scientists (UCS) put out a 2001 “report” entitled “Hogging it! Estimates of Antimicrobial Abuse in Livestock.” It's still quoted to hugely inflate values for percent of animal antibiotics used for growth promotion and the percent of total U.S. antibiotic production used for growth promotion and in food animals in general.

But UCS used FDA's “green book” (a list of approved products) to find food-animal approvals and then estimated use from numbers of animals and label claims. Here's an example:

Use of oleandomycin and efrotomycin in pigs was estimated at 30 million grams/year (about 66,000 lbs.). The only catch is that, while these two drugs received U.S. approvals, they were never actually marketed. This is agenda-driven junk science at its best.

Another point to clarify when people start throwing around consumption numbers is that many antimicrobials used in food animals are in classes that have no relation to those used in human therapeutics. A 2008 press release by the Animal Health Institute (AHI) reports the volume of veterinary antibacterial ingredients (food and companion animal not differentiated) sold by AHI members in recent years. Unlike the UCS numbers, these are based on fact.

According to AHI, in 2007, a total of 27,846,292 lbs. were sold; 10,747,965 (39%) were antimicrobials with no relation to human therapeutics (ionophores Rumensin and Bovatec are examples). Almost all the unrelated compounds would be used in food animals, so this percentage would be higher if the total number was also only food animal.

In my October 2008 column, “Another change in antibiotic use is coming,” I wrote about FDA's proposed prohibition of extralabel use of cephlosporins. For beef producers, this would have affected extralabel use of ceftiofur (Naxcel, Excenel, Excede).

This proposal has been withdrawn for further consideration, which the press has largely treated as a case of FDA bowing to “factory farming.” Actually, the agency is doing its job by taking time to consider some substantive comments, and will most likely seek further input with some form of a more focused prohibition still a possibility.

It's interesting that the lead-in to the story about the withdrawal on the National Public Radio website states “FDA had planned to ban the use of a popular antibiotic from use in animal feed.” But any use of this class of compounds in the feed of food animals is already illegal since there's no approved feed label for the cephalosporins in the U.S.

What's more, using a drug in an extralabel manner requires veterinary guidance by law. The regulations are already there to ensure we make the best decisions when a veterinarian determines that extralabel use is necessary.

And have you been following methicillin-resistant Staph. aureus (MRSA) in the press? It causes skin and other infections and is spread by contact in places such as locker rooms or long-term care facilities. When Staph. aureus becomes resistant to the methicillin class of penicillins, it is resistant to all but the last-ditch antibiotics. Most articles I've read about these infections eventually end by mentioning how antibiotic use in food animals contributes to the resistance problem.

But the human MRSA outbreaks in the U.S. are different strains than those found in animals. Perhaps that human form of MRSA is proliferating due to inappropriate and unrestrained antibiotic use in humans? Naw, couldn't be.

Again, the food-animal industry isn't without fault with reference to antibiotics in relation to selected organisms. But we don't need to let the above-mentioned manure spreaders continue to operate in road gear.

Mike Apley, DVM, Ph.D., is an associate professor in clinical sciences at Kansas State University in Manhattan.