Presidents message — July and Augut, 1999

Greetings from Raleigh, North Carolina. By the time you read this message, I am hopeful that some degree of profitability will have returned to swine production. Agricultural economists have analyzed sow slaughter numbers and estimate that a modest liquidation of breeding swine has occurred. In addition, the accelerated buy-out of swine herds quarantined due to infection with pseudorabies virus (Aujeszky’s disease) has slightly increased breeding herd liquidation. This offers a potential short-term increase in price for live pigs due to the decrease in supply. The long term remains clouded, however, and depends on producer intentions and other factors, such as slaughter capacity.

Dr. Tom Burkgren, Executive Director of the AASP, and members of the Pharmaceutical Issues Committee, met with me in Kansas City, Missouri. This meeting had two objectives:

• to attend a stakeholder’s meeting sponsored by the Food and Drug Administration’s Center for Veterinary Medicine (FDA-CVM), and
• to develop guidelines for prudent antibiotic use in swine production.

The importance of these meetings cannot be overstated. The issue is the future of antibiotics that are available for use in swine practice and production. In addition, the availability of new antibiotics for use in livestock production is affected. The FDA-CVM is seeking input from all interested parties as it prepares a framework document, entitled "A proposed framework for evaluating and assuring the human safety of the microbial effects of antimicrobial new animal drugs intended for use in food-producing animals." Specifically, the proposed framework document states that "evidence of increasing resistance to antimicrobial drug treatment in bacteria that infect humans has raised questions about the role that antimicrobial drug use in food-producing animals plays in the emergence of antimicrobial drug resistant bacteria." At this time the framework is not law, but in the near future, the FDA-CVM will publish in the federal register the results of a risk assessment study. These results will be used to assess the resistance that develops after antimicrobial use on specific pathogenic and nonpathogenic bacteria. This will lead to the framework document being promulgated into law to protect the public health.

The framework as proposed contains five components:

1. assessing the effect of proposed uses on human pathogen load;
2. assessing the safety of proposed animal uses of drugs according to their importance in human medicine and the potential human exposure to resistant bacteria acquired from food-producing animals that are human pathogens or that can transfer their resistance to human pathogens;
3. assessing pre-approval data showing that the degree of resistance transfer from proposed uses of drugs, if any, will be safe;
4. establishing "resistance" and "monitoring" thresholds to ensure approved uses do not result in resistance development in animals or transfer to humans above the established levels; and
5. establishing post-approval studies and monitoring.

Other concepts in the framework include pathogen load and resistance.

With respect to resistance, the FDA-CVM believes that evaluating the human health impact of the development of resistant bacteria from antimicrobial drugs used in food-producing animals depends primarily upon:

• the importance of the drug or drug class in human medicine, and
• the potential human exposure to resistant bacteria acquired from food-producing animals that are human pathogens or that can transfer their resistance to human pathogens.

These two factors expand the definition of human health impact to include the most important classes of drugs used in human health; for example, the fluoroquinolone class of compounds. Other classes might include the cephalosporins, tetracyclines, the macrolides, and the penicillins. Drugs in these classes make up many of the drugs currently available for use today. The document goes on to further define three categories of drugs in regard to their importance for human medicine, to evaluate the potential exposure to humans, and to define microbial safety and a safe or "threshold" level of antibiotic resistance development.

The framework proposes both drug pre-approval and post-approval monitoring of the development of antibiotic resistance. After the lengthy and costly approval and licensing process for new drugs, the development of resistance to that drug will be monitored. If antibiotic resistance develops above the designated threshold level, the drug will be declared unsafe and will be withdrawn from use. The uncertainty for return on investment may discourage pharmaceutical companies from investing in new drug research and development. The end result will be a lack of new drugs approved for use in food animals.

Many questions remain unanswered, but one thing is certain: this issue is not transient. It is a global issue. It is a public health issue. It is certainly a media issue. Every member of the AASP should strive to become informed about the development of antibiotic resistance. Although the framework document will be revised, ultimately in the not-too-distant future, it will become law.

Dr. John Waddell, Chairman, and the other members of the Pharmaceutical Issues Committee of the AASP are producing drug use guidelines for swine practice. These guidelines are intended to help practitioners define the appropriate use of antibiotics in accordance with the intent of the Animal Drug Availability Act (ADAA). These guidelines will not offset the intent of the framework document discussed above, but they are the AASP’s response to the need to better define drug use to minimize antimicrobial resistance development.

I hope to have seen many of you at the World Pork Expo in Des Moines by the time you read this message.

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