Not surprisingly, no consensus was reached on how to best deal with issues associated with antibiotic use and antibiotic resistance. But all angles were hashed out by a bevy of presenters from universities, associations and government during a National Institute for Animal Agriculture (NIAA)-staged symposium in late October.

What is apparent is that antibiotic use in food-producing animals is a complex issue that perplexes many experts and raises the hackles of social activists. Meanwhile, rates of antimicrobial resistance (AMR) continue to escalate globally.

Scott Hurd, DVM, associate professor of Iowa State University’s College of Veterinary Medicine, attempted to inject some reason into the “Antibiotic Use in Food Animals: A Dialogue for a Common Purpose” symposium.

The presence of an AMR hazard creates concern, but concern is not a risk, he says in the opening address to the crowd of 150 participants. Rather, human health risk requires sufficient exposure that will result in actual harm. The risk of AMR is not easily achieved, Hurd points out. Three steps in a chain of events must all fall into place:

• AMR bacteria are selected in the food animal as a result of antimicrobial use;

• Humans ingest sufficient AMR bacteria present in the relevant food product from treated animals; and

• Disease results, which causes the patient to seek medical care and treatment with an antibiotic to which the bacteria is resistant, and that produces an adverse health outcome.

“Acceptable risk is difficult to determine, but should include public benefits of alternative practice,” Hurd says. The food industry employs numerous risk-management interventions along the food chain, intended to minimize and contain AMR foodborne bacteria to ensure public health and food safety.

How Antibiotics Help

Judicious use of antibiotics helps produce safe, nutritious food at a reasonable price and prevents disease, resulting in improvement in animal and human health.

“Antibiotics are one of the technological tools that can be used to ensure affordable food,” states Tom Shryock, senior research advisor of Microbiology, Elanco Animal Health.

He points out that public concern over antibiotic use in food animals has caused a conundrum for veterinarians. They swear to protect animal health and welfare and relieve animal suffering, but also to prevent it. That can require the use of antibiotics in food animals.

Clarifying Antibiotic Resistance

Three messages became clear from the speakers regarding antibiotic resistance:

• Using an antibiotic — or using more of it — won’t always cause antibiotic resistance to occur or increase from current levels. Likewise, using less of an antibiotic or stopping use won’t always cause resistance to that antibiotic to disappear or decrease from current levels.

• Concerns about antibiotic resistance are used as ammunition to fuel other agendas, and the arguments assume a vacuum in which no new drugs are developed.

• Much is still unknown in the human-health community about why antibiotic resistance occurs. As such, antibiotic use in animal agriculture and in the human population should be used as sparingly as possible.

“Antibiotic use in animal agriculture is not a black-and-white issue. If it was an easy issue to understand and explain, we would have solved it a long time ago. That said, we in animal agriculture need to get in the same boat and row together — across species,” states Mike Lormore, DVM, director of Dairy Veterinary Operations for Pfizer Animal Health.

It’s important for the animal agriculture industry to build trust with consumers by demonstrating a consistent message on food safety and providing them with information regarding on-farm production practices, Lormore says. Messages to consumers should focus on four key facts:

1.         Farm animals are under the care of licensed veterinarians.

2.         Vaccines are used to protect animals from various illnesses.

3.         Sick animals are treated with medicines, including antibiotics, to restore health and offer safeguards to ensure the safety of meat and milk.

4.         If an antibiotic is used to treat sick animals, then the meat or dairy products are not allowed to enter the food supply until the medicine has sufficiently cleared the animal’s system.

To prevent unsafe antibiotic residues in foods of animal origin, the various sectors of the livestock industry follow best practices in disease prevention and treatment. In the swine industry, multi-phase, all-in, all-out management practices have been coupled with advanced diagnostics and responsible antibiotic use practices as part of the industry’s Pork Quality Assurance (PQA) Plus program to improve strategic disease prevention, says Paul Ruen, DVM, Fairmont (MN) Veterinary Clinic and president of the American Association of Swine Veterinarians.

Human Health and Antibiotics

Elanco’s Shryock reminds that antibiotic resistance is a natural biological phenomenon that was around long before the era of antimicrobial therapy. Resistance to penicillin in some strains of staphylococci was found almost immediately after introduction of the drug in 1946. In the late 1940s, resistance to streptomycin, chloramphenicol and the tetracyclines was noted soon after their introduction.

Presence of AMR bacteria is not exclusive to the farm and is found in groundwater, ocean trenches, wild animals and even in 30,000-year-old permafrost.

“Additionally, there is no known connection between several drug-resistant human pathogens and food-producing and/or companion animals. Some drug-resistant infections in humans are a result of extensive use in humans, since the antibiotics in question have never been approved for use in food-producing animals,” Shryock explains.

Antimicrobial resistance is not a predictable occurrence, because it results from complex interactions among three factors:

• Antibiotic class;

• Specific pathogen; and

• Potential host population.

Managing the biological factors around antimicrobial resistance has been described as volatile, uncertain, complex and ambiguous, making resistance all but impossible to predict, Shryock says. “Blanket approaches to minimize resistance development and dissemination are simply unable to effectively solve each and every antibiotic/pathogen/host combination,” he adds.

Conference speakers agreed that resistance to antimicrobials is an evolving process that occurs both in the presence and absence of antimicrobial use in both human and animal populations. There’s no doubt, however, that it’s imperative that antibiotics be used judiciously in animal agriculture and public health sectors.

To manage antimicrobial resistance requires a multi-disciplinary approach with proper controls, surveillance systems, further research, increased drug development and more education.

Despite pressures to restrict antibiotic use to address antibiotic resistance, no conclusive evidence exists as to the primary factors that cause antibiotic resistance, the speakers
concurred.

What’s needed is robust research and development investment to commercialize new antimicrobials, Shryock says.

The reality, however, is that the changing global landscape of antibiotic use restrictions has undermined the value of new product development, adds Scott Brown, senior director of Metabolism and Safety for Pfizer Animal Health. The speed of change of the regulatory and political landscapes is moving faster than product development can move. Consequently, these actions will reduce the ability of veterinarians to treat and control animal diseases over the next 10-15 years, he predicts.

Regulatory Role

In recent years, the Food and Drug Administration (FDA) has issued two documents dealing with the current debate on the future of animal antibiotics, according to William Flynn, DVM, deputy director for Science Policy:

• Document 152 provides a process to assess resistance risks and a pathway for approving new animal drugs.

• Document 209 recommends limiting the use of medically important antimicrobial drugs to those uses that are considered necessary for assuring public health (treat, control or prevent disease) and should include veterinary involvement.

The latter document recommends that steps be taken to phase out the growth-promotion use of medically important drugs, Flynn says. “In response to the concern that eliminating growth-promotion use of certain drugs may lead to an increase in animal disease, FDA proposes that changes be phased in over time to minimize impacts and assure that animal health needs continue to be met,” he adds.

Flynn explains that FDA’s proposed strategy is to implement the recommended changes through a voluntary approach over a number of years to provide adequate transition, while reducing adverse impacts on human health and industry.

Such changes in restrictions on animal antibiotics can have unintended consequences, however. After certain antibiotics were banned in Denmark, more livestock became sick and required greater use of therapeutic antibiotics, Hurd says. “Further, the elimination of antibiotics at the health-maintenance level in Denmark has not led to a substantial impact on the incidence of antibiotic-resistant foodborne illness in humans, based on information gathered from the U.S. General Accounting Office and the Danish Integrated Antimicrobial Resistance Monitoring and Research Program (www.danmap.org),” he says.

To find out more about the symposium and the white paper released by the National Institute for Animal Agriculture, go to www.animalagriculture.org or call (719) 538-8843.