A hearing before a congressional subcommittee this summer looked at the extent to which antimicrobial use in animal agriculture may be contributing to the ineffectiveness of antimicrobial drugs used in human medicine.
It was the third hearing before the House Energy and Commerce Committee's Subcommittee on Health on the overall threat of antimicrobial resistance to public health—an issue that's been called one of the greatest health care challenges of modern time.
Dr. Christine Hoang, AVMA Scientific Activities Division assistant
director, tells a House subcommittee that veterinarians share
the same concerns about antimicrobial resistance as do their
human health counterparts.
This latest hearing, held July 14, brought together physicians and veterinarians who offered conflicting analyses of the degree to which they believe resistant pathogens are moving through the food supply.
Henry A. Waxman, chairman of the Energy and Commerce Committee, called "overprescribing" of antimicrobials a standard practice in U.S. animal agriculture. "(A)nimals regularly are fed these drugs—not to treat any illness at all—but simply to promote growth," he said.
"There appears to be universal agreement on yet another point: The key to reducing antibiotic resistance is to reduce the use of antibiotics," Waxman added.
The controversy over antimicrobial use in livestock is not new, but the issue has been heating up this summer. In June the Food and Drug Administration issued a draft guidance aimed at curbing drug use in food animals if the drugs are important to human medicine. The agency also recommends expanding veterinary oversight of antimicrobial use in animal agriculture (see JAVMA, Aug. 1, 2010).
Ali S. Khan, MD, who in addition to being the assistant surgeon general is acting deputy director of the National Center for Emerging and Zoonotic Infectious Diseases at the Centers for Disease Control and Prevention, told the subcommittee the CDC supports the FDA's approach because antimicrobials should be limited to protecting human and animal health.
"Purposes other than the protection of animal or human health should not be considered judicious use," Dr. Khan said.
The veterinary profession itself continues to be heavily engaged in the debate over the judicious use of antimicrobials. As of press time in July, members of the AVMA House of Delegates were expected to vote later that month on whether to consider two resolutions dealing with antimicrobials when they convened in Atlanta for the HOD's regular annual session.
Following last summer's HOD session, and at the direction of delegates, the AVMA convened an Antimicrobial Use Task Force that, in its recently released executive summary, stated: "The issues surrounding antimicrobial use in veterinary medicine are multifaceted, involving highly complex information as well as a multitude of scientific unknowns."
Dr. Christine Hoang, an assistant director of the AVMA Scientific Activities Division, reiterated this conclusion for the Health Subcommittee at the hearing and cautioned against a rush to restrict the use of antimicrobials in animal agriculture.
"Our members share the same concerns as our human health counterparts," Dr. Hoang said. "Yet we also have additional concerns that must be considered—impacts on animal health and welfare and even negative impacts on human health that are often unrealized."
Dr. Hoang noted a two-decades-old study that concluded human health hazards from growth-promotant uses could not be proved or disproved. Moreover, there is no agreement over the acceptable degree of risk to humans associated with the use of antimicrobials in food animals.
Countries that have banned growth-promotant uses of the drugs, most notably Denmark, have seen significant increases in the therapeutic use of antimicrobials, Dr. Hoang told the subcommittee. In addition, therapeutic drug use has increased as the prevalence of animal diseases has risen, and there's no clear evidence public health is enhanced when the drugs are used only for clinical illness.
"Veterinarians are trained medical professionals with the ability to predict disease conditions and recommend appropriate therapy," she said. "Those uses should not be considered injudicious nor banned as routine use. If a disease is predictable and can be prevented, it is incumbent upon the veterinarian to initiate appropriate therapy to prevent animal pain and suffering."
Dr. Gail R. Hansen of Pew Charitable Trusts' Human Health and Industrial Farming Campaign told subcommittee members that the routine, nontherapeutic use of antimicrobials in livestock has spurred generations of resistant bacteria that are causing life-threatening illnesses once easily treatable with antimicrobials.
A former AVMA Congressional Science Fellow, Dr. Hansen called on Congress not to wait for new FDA regulation but to instead pass the Preservation of Antibiotics for Medical Treatment Act, which is currently before the House Subcommittee on Health as well as in the Senate.
With a stated purpose of reducing antimicrobial-resistant bacteria, PAMTA (H.R. 1549/S. 619) would prohibit approvals for certain uses of any new animal drug for food-producing animals if the drug is already used in human medicine. Additionally, an animal drug would be removed from the market within two years of the law's enactment if the drug is also used in human medicine and unless certain safety requirements are met.
The AVMA says the requirement for reasonable certainty of no harm is extremely difficult to prove, however, and opposes the legislation because it would result in increased animal disease and death without assurance of improving human health.