Bovine practitioners weigh role in drug residues, antimicrobial resistance
Evolving drug regulations and public health concerns mean that bovine practitioners should be even more careful to use pharmaceuticals legally and judiciously, according to speakers at the recent conference of the American Association of Bovine Practitioners.
Two of the general sessions at the AABP meeting focused on pressing pharmaceutical issues in the beef and dairy industries. The sessions addressed the regulation and responsibilities of bovine practitioners relevant to drug residues in meat and milk, prescriptions and distribution, and antimicrobial resistance.
Drug residues
Dr. D. Dee Griffin, University of Nebraska feedlot veterinarian and professor, opened the sessions by speaking about drug residues in bovine practice.
Dr. Griffin summarized relevant data from the U.S. Department of Agriculture's National Residue Program for 2007, noting that violative drug residues were most common in culled dairy cows. Overall, meat inspectors found violative residues in fewer than 1 percent of almost 150,000 samples from high-risk food animals, such as animals with signs of disease.
About a third of the violative residues came from veterinary prescription drugs—particularly flunixin meglumine and sulfonamide antimicrobials—rather than over-the-counter drugs, Dr. Griffin said.
The Food and Drug Administration issued a reminder in 2007 that the agency has approved intravenous administration of flunixin meglumine, but not intramuscular administration of the drug, partly to prevent violative residues. One option to help prevent violative antimicrobial residues in cattle is to test urine for microbial inhibition, Dr. Griffin added, although the tests are not perfect.
"Don't sell a cow with a residue," Dr. Griffin said. "Bottom line, people buy what they trust."
Prescriptions, distribution
Two pharmacists and two veterinarians discussed federal and state regulations regarding veterinary prescriptions and drug distribution.
The first speaker was Shirley Arck, PharmD, a member of the Kansas State Board of Pharmacy and administrator of Kansas State University's veterinary hospital. Dr. Arck said stakeholders who want to have a say in drug regulations need to make their messages clear, concise, compelling, and comprehensively researched. Even better is for stakeholders to reach consensus.
"As a regulator, that's what I want to see," Dr. Arck said. "If there's consensus among the stakeholders, if you have a compelling argument, we're ready to help you."
Big issues facing regulators include drug counterfeiting and abuse, Dr. Arck said, and programs to control these problems can affect veterinarians. New federal regulations to combat counterfeiting require pedigrees to accompany human-label prescription drugs through the distribution chain, documenting transactions from the manufacturer onward. States are creating programs to track prescription drugs with abuse potential, such as controlled substances.
Elaine Lust, PharmD, consultant for Professional Veterinary Products in Omaha, Neb., spoke about state licensing of wholesale drug distributors. Dr. Lust noted that veterinarians usually do not need a pharmacy license to dispense drugs incident to their practice, but they generally need a distributor license to sell prescription drugs to anyone other than a client.
Dr. Lust said the Verified Accredited Wholesale Distributors program, through the National Association of Boards of Pharmacy, provides a way for regulators and practitioners to identify drug distributors that are compliant with federal and state rules.
"No two states are alike," Dr. Lust said. "If differences or exemptions exist in prescription drugs when they're particularly used in food animals, your wholesale distributor should know the rules and regs in the state where they are physically located as well as every state where they are shipping on your behalf."
Regarding the effect of food animal production on antimicrobial resistance: "I don't believe that we're a major driver of the problem. I don't believe we're a completely zero driver of the problem.
–DR. MICHAEL D. APLEY, PROFESSOR OF PRODUCTION MEDICINE AND CLINICAL PHARMACOLOGY, KANSAS STATE UNIVERSITY COLLEGE OF VETERINARY MEDICINE
Dr. Michael D. Apley, a professor of production medicine and clinical pharmacology at Kansas State University's veterinary college, discussed the role of veterinary prescriptions and drug distribution in antimicrobial resistance.
Dr. Apley said food animal practitioners should be aware that Congress is considering the Preservation of Antibiotics for Medical Treatment Act, which would restrict use of certain drugs in food animals in an effort to stem antimicrobial resistance.
"I don't believe that we're a major driver of the problem," he said. Then he added, "I don't believe we're a completely zero driver of the problem."
State veterinary boards need to enforce existing regulations that affect judicious antimicrobial use, Dr. Apley said, by revoking the licenses of practitioners who write prescriptions without a valid veterinarian-client-patient relationship. Practitioners also should ask pharmacy boards to crack down on irresponsible drug distributors.
Dr. Neal Bataller, director of the Division of Compliance at the FDA Center for Veterinary Medicine, gave an overview of federal legislation and enforcement tools relevant to veterinary prescriptions.
"Our mission is to make sure that you have in your hands and producers utilize drugs that are safe and effective—they work and they don't do any unintended harm towards the animal," Dr. Bataller said. "The other thing we do, too, is to make sure that feed and human food are safe and wholesome, without contaminants in them, such as drug residues."
The Animal Medicinal Drug Use Clarification Act allows extralabel drug use in animals only with a valid VCPR, Dr. Bataller noted. The FDA has prohibited extralabel use of certain drugs in food animals, recently seeking to ban extralabel use of cephalosporins.
Dr. Bataller said FDA enforcement tools to address violative drug residues and other issues include inspections, warning letters, seizures, injunctions, and prosecutions.
Antimicrobial resistance
Dr. H. Morgan Scott, an epidemiology professor at the K-State veterinary college, spoke on sociologic issues and scientific progress in mitigating antimicrobial resistance.
Resistant microbes spread differently in human populations than in cattle herds, Dr. Scott noted. Human patients go from the community to the hospital and then back to the community. Beef cattle go from the original herd to the feedlot to the slaughterhouse.
"The bacterial populations in the animals are dead at the end of the feeding cycle, and nothing is returned to the community," Dr. Scott said, affording opportunities to stem antimicrobial resistance.
Dr. Scott presented results from a survey of feedlot veterinarians and operators that measured opinions regarding antimicrobial use. Few respondents felt that antimicrobial use in feedlots poses a risk to public health. Most of the veterinarians had concerns about preventive use, however, in comparison with a minority of operators.
Feedlot veterinarians and operators will follow voluntary guidelines on antimicrobial use only if they think others will comply, Dr. Scott said, because feedlots that limit antimicrobial use could be at a competitive disadvantage.
Dr. Scott said changing the microbial ecology of a feedlot is another approach to mitigating antimicrobial resistance. He presented results of a survey of feedlot operators regarding willingness to change management practices that influence microbial ecology. Respondents were willing to outsource chronically ill cattle or cull the animals sooner and to increase turnover in the sick pen.
"It's worth being proactive and being able to state that we know that there are management practices that work to reduce resistance, or at least reduce its progression, and others that may help to mitigate," Dr. Scott said.