The topic of antimicrobial use in food-producing animals saw a lot of activity in 2013. During the year, the National Institute for Animal Agriculture held its third antimicrobial use symposium in as many years, the Centers for Disease Control and Prevention (CDC) released its treatise on Antibiotic Resistance Threats in the United States, 2013 (http://www.cdc.gov/drugresistance/threat-report-2013/pdf/ar-threats-2013–508.pdf), and the American Veterinary Medical Association (AVMA) began reviewing its judicious use guidelines. Additionally, the Food and Drug Administration continued to move toward a voluntary withdrawal of medically important antimicrobial growth promotants and the transition of all feed-grade antimicrobials of human importance from over-the-counter to Veterinary Feed Directive status.
To me, the CDC’s publication was the most telling. Of the 114-page document, only two pages were devoted to describing the involvement of antimicrobial use in food animals as it relates to resistance in humans. The report outlines four routes by which antimicrobials administered to food animals may harm public health: use of antibiotics in food-producing animals allows antibiotic-resistant bacteria to thrive while susceptible bacteria are suppressed or die; resistant bacteria can be transmitted from food-producing animals to humans through the food supply; resistant bacteria can cause infections in humans; and infections caused by resistant bacteria can result in adverse health consequences for humans.
The first pathway is true any time antibiotics are used. As the CDC notes earlier in the report, “simply using antibiotics creates resistance.” That’s the nature of the beast. Actually, all four statements are true, but notice the use of the word “can” in the last three. The fact that these things CAN happen doesn’t mean that they do happen or that they happen with any frequency, and even if they do happen, it doesn’t mean the consequences are of any concern.
Activist groups state that more antimicrobials are used in livestock than in humans. The higher use in livestock makes sense, given that the drugs are dosed by body weight. As the CDC report noted, “it is difficult to directly compare the amount of drugs used in food animals with the amount used in humans….” The volume of antimicrobial used is irrelevant. The interaction between the drug and the bacteria drives resistance.
The CDC spent the majority of the publication addressing the human use (or misuse) of antimicrobials. The report outlined numerous examples of inappropriate dispensing by human physicians – stating that “up to 50% of all antibiotics prescribed for people are not needed…” and describes the unnecessary dispensing of antimicrobials in physicians’ offices as “common.” The report clearly highlights the overuse and misuse of antimicrobials in human medicine as the leading cause of hazardous resistance in the human population. There is still no compelling evidence that antimicrobial use in food animals causes any significant increase of antimicrobial resistance in humans resulting in harmful antimicrobial treatment outcomes. As a matter of fact, most risk assessments place the impact of livestock antimicrobial use as negligible relative to human resistance.
While veterinary use of antimicrobials plays a less significant role in resistance in the human population, all uses of antimicrobials contribute to resistance – as correctly stated by the CDC. Therefore, we all need to strive to use antimicrobials judiciously and according to label instructions or in an extra-label manner as outlined in the Animal Medicinal Drug Use Clarification Act. Any use of feed-grade antimicrobials in a manner not described on the product label is illegal – no excuses. Any extra-label use of a prohibited antimicrobial is illegal – no excuses. Even though some of the current regulations regarding extra-label use may seem nonsensical, it is the law, and we are ethically bound to abide by the legal restrictions.
Dr Mike Apley, clinical pharmacologist at Kansas State University, recently drew our attention to a research study published in the Journal of the American Veterinary Medical Association (JAVMA). This peer-reviewed study describes the illegal extra-label use of enrofloxacin to treat otitis in dairy calves. Food and Drug Administration regulation prohibits the extra-label use of fluoroquinolones in food animals. The article makes no mention of the legality of the suggested drug use. His concern is that such publications reflect on the attitude of the profession regarding the appropriate and judicious use of antimicrobials even though JAVMA has complete autonomy from the AVMA. His question to food-animal practitioners is “how significant is this ‘subculture’ that ignores or overlooks the regulations when using antimicrobials?”
Some respondents justified the extra-label enrofloxacin use as legal, given that the product label is for the treatment of bovine respiratory disease, by making the case that the ear is part of the respiratory tract. While I suppose that may be “technically” correct, I question whether it conforms to the spirit of the law.
This example and Dr Apley’s question should give us all reason to pause and think about what we’re doing. Those of us who work with legislators, regulators, manufacturers, and activist groups have to be able to stand up for veterinarians as part of the solution, not the problem. We insist, and I continue to believe, that veterinarians are the best trained professionals to be overseeing the judicious use of antimicrobials for the health and well-being of the animals under our care, as well as the guardians of food safety and public health. The injudicious and illegal activities of a few jeopardize the ability of all of us to access the drugs we need to carry out our responsibilities. Whether you agree with the law or not, it is the law, and we are ethically, morally, and legally required to abide by it, while working to change it if necessary.