Geni Wren When looking at how antimicrobials are used in animals and humans, it’s important to carefully look at the differences between the groups.
Speaking to more than 170 participants at the National Institute for Animal Agriculture’s 2012 Antibiotic Symposium in Columbus, Ohio this week, Ron DeHaven, DVM, MS, American Veterinary Medical Association (AVMA) executive vice president, broke antibiotic use into three categories.
For companion animals, DeHaven explained that most antimicrobial use is exclusively under a veterinary-client-patient relationship.
In food animals, some antibiotics can be used over-the-counter as per their approved labels, in feed or water, or added by a feed mill or producer to feed as directed by the FDA on the label. Antibiotics for food animals can also be used under the Veterinary Feed Directive (VFD) and are prescription only (currently only florfenicol and tilmicosin are approved for this use). DeHaven noted that OTC medically-important antimicrobials may also be moved under a VFD designation.
The third use for food animals is under a prescription by a veterinarian.
Differences in human/food-animal use
In humans, antimicrobials can be used for treatment or prevention, and the physician determines the indication, route, dose, frequency and duration. “There are no restrictions on extralabel or off-label use of human antimicrobials,” DeHaven said.
In food animals, however, only drugs approved for specific indications, and under specific dose, duration, frequency and route of administration can be used, and extralabel uses are heavily regulated.
Controversy and complexity
DeHaven noted that one of the concerns is the reservoir or source of antimicrobial resistance. “There is no clear scientific evidence of how and to what extent such exposure of antimicrobial resistant pathogens affects human health,” he said. “There is no hard evidence that connects human infection with resistant bacteria caused by use of antimicrobials in food animals. There is no evidence that restricting or limiting antimicrobial use in food animals will improve human health or reduce the risk of antimicrobial resistance.”
Benefits vs. risk
We use antimicrobials in food animals because of the numerous benefits to human and animal health. Antimicrobial use improves animal welfare by preventing, controlling and treating disease. It enhances food safety because “Healthy animals produce safer food,” DeHaven said.