Blinded samples of milk will likely be used to determine whether inappropriate antimicrobial residues are a substantial problem in milk from dairies previously found to have violative residues in tissues from culled cows.
Dr. William T. Flynn, deputy director for science policy in the Food and Drug Administration, said milk samples are already screened for the presence of beta-lactam antimicrobials, but milk is not routinely tested for the presence of other antimicrobials commonly administered to dairy cows. The agency is considering conducting a blinded sample survey, using a test that detects the presence of 26 drugs.
The survey should allow the agency to "gather the information we need to try to determine to what extent is this a problem and, if it is, what do we need to do to try to help address it," Dr. Flynn said. Measures to address the problem could include expanding investigations of dairies with tissue violations to include milk sample collection and expanding milk screening to identify other drug residues.
Dr. Flynn made the comments during a presentation at the annual conference of the American Association of Bovine Practitioners Sept. 22-24 in St. Louis. He noted that two-thirds of the illegal antimicrobial residues found and reported by the Department of Agriculture's Food Safety and Inspection Service come from culled dairy cattle.
Antimicrobial use, antimicrobial resistance, and drug residues were topics of a series of lectures on food safety during the AABP meeting. Dr. John Fetrow of Mahtomedi, Minn., said in his presentation on treatment protocols, for example, that veterinarians need to pay close attention to antimicrobial use by dairy clients, especially in animals that might be culled. Veterinarians should establish drug use protocols on dairies that include elements such as disease definitions, treatment protocols, and time line estimates, he said.
Dr. Sheryl Gow, a veterinary epidemiologist with the Public Health Agency of Canada, expects antimicrobial resistance will also remain a global concern and that use of these drugs by veterinarians will be increasingly scrutinized. Dr. Paul S. Morley, a professor at Colorado State University, said he expects some middle ground is emerging in the debate over the effects of antimicrobial use in animals on bacterial resistance in humans.
"It's not as bad as some people say, but it's certainly not (having) no effect, in my opinion," he said.
Dr. Morley said the dangers of using antimicrobials are more insidious than the dangers of using anesthetics, for which overuse has immediate and obvious effects. He encouraged veterinarians to more often ask themselves whether they could use antimicrobials that are in categories considered to be less important for use in human medicine.