Tuesday, December 17, 2013

The FDA's new 'ban' on antibiotic use in animals needs more teeth

The CDC estimates that 2 million people in the US every year contract antibiotic resistant infections, and 23,000 die as a result.  Antibiotic resistant bacteria -- another on the list of looming crises we're smart enough to do something about but are doing far too little far too slowly.  So it would be good if, as reported by New York Times, the US Food and Drug Administration had announced what will be a major policy to slow down the routine overuse of antibiotics in the food supply.  But it seems unlikely.

For decades, healthy cows, pigs and chickens have been given antibiotics to maintain their health and to boost their growth, and more recently, so have farmed fish, but this is a major cause of the waning effectiveness of antibiotics. There seem to be multiple pathways leading from antibiotic use in animals to antibiotic resistance in humans.*  

Chicken house; Wikimedia Commons
 Low dose, prolonged use of antibiotics in animals creates ideal conditions for the selection and growth of antibiotic resistance.  How they spread from animals to humans is difficult to document and probably there are numerous pathways, but it does seem sometimes be possible by consumption of food carrying resistant bacteria, and indeed farm workers often harbor antibiotic resistant strains of gut bacteria that indicate they originated in animals on the farm, but so can people who eat meat or fish contaminated with resistant bacteria.  There is evidence of horizontal transfer of resistance genes, too, from bacteria most often found in animals to those that prefer human hosts.

The 'ban'
Now the FDA says it is effectively banning the use in food animals of those antibiotics that are medically important in human health, and that are used solely to enhance animal growth. A second piece of the new regulations is that a licensed veterinarian will be required to oversee antibiotic use if the grower wants to deliver these drugs to prevent illness.  The changes will become effective over the next three years.

How will it work?  The FDA is requesting that drug makers change antibiotic labels to exclude their use in animal growth promotion.  Whether they do this or not is entirely voluntary.  Given the huge vested interest drug manufacturers have in selling antibiotics to food producers -- 70-80% of antibiotics in the US are used in the food supply** -- and that farmers have in promoting fast growth in their animals, whether this will actually work is an open question, and there are many doubters. Though, the two pharmaceuticals that make the majority of antibiotics have said they will comply.

Comply or not, there are loopholes.  A food producer can claim that the same daily use of low doses of antibiotics now meant to enhance growth is required to prevent illness, which would mean it's allowed.  Thus, it's possible that nothing will change.  Many critics would much prefer that antibiotics be allowed only to treat infection, and would like to see the FDA ban the preventive use of antibiotics. 

Why we need a policy that works
It is important that we have a policy that works.  Maryn McKenna describes the dire consequences of losing antibiotics in her sobering, excellent recent piece for Wired, ("When We Lose Antibiotics, Here's Everything Else We'll Lose Too").  Not only will we lose the obvious, the ability to treat infection, but also, as she writes, we'll lose the ability to treat cancer when it requires suppressing the immune response, to do organ transplants, kidney dialysis because it relies on an implanted portal into the blood stream, many kinds of surgery, Caesarian sections will be risky, and much more.  As she points out, in the pre-antibiotic era, "one out of every nine skin infections killed" -- life will be a lot more dangerous again. 

And, clearly, the way animals are raised for food on industrial farms will also have to change.  But there are many arguments in favor of this already, even apart from the antibiotic resistance issue.  Animals raised in the kinds of crowded conditions pig or cattle or chickens are too often raised in increases their risk of illness.  And, these animals are often raised on feed that that also makes them more susceptible; smaller farms, and more humane conditions would greatly reduce the need for antibiotics.  And, as McKenna also points out, many crops depend on antibiotics as well.  When fruit or vegetable diseases now controlled with antibiotics can no longer be, that will be another major problem.

So, the FDA may be taking a desirable first step, but the stakes in public health terms are very high.  If the critics turn out to be right about the loopholes, there's a lot to lose. 

*Smith, DL et al., Animal antibiotic use has an early but important impact on the emergence of antibiotic resistance in human commensal bacteria, PNAS, 2001. 

Marshall, BM; Levy, SB., Food Animals and Antimicrobials: Impacts on Human Health, Clinical Microbiology Reviews, 2011. 
**Mellon M, Benbrook C, Benbrook K L. Hogging It: Estimates of Antimicrobial Abuse in Livestock. Cambridge, MA: Union of Concerned Scientists; 2001. 
National Research Council, Committee on Drug Use in Food Animals. The Use of Drugs in Food Animals: Benefits and Risks. Washington, DC: Natl. Acad. Press; 1999.

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