Adjusting to reduced drug access, use
Dr. Mike Apley thinks judicious use and stewardship are needed to help ensure antimicrobials remain useful in 30 to 40 years.
“True stewardship is the hard, hard work of evaluating how we promote health without having to use an antibiotic,” he said.
Dr. Apley, a professor of production medicine and clinical pharmacology at Kansas State University, said antimicrobial resistance is a concern, and new antimicrobial classes are likely to be reserved for use in human medicine, rather than be approved for use in livestock. Veterinarians can help maintain the value of antimicrobials already approved for use in livestock by helping to find ways to use smaller volumes of the drugs when they are needed and by identifying alternatives, he said.
Dr. Apley delivered one of a series of lectures Feb. 29 at the American Association of Swine Veterinarians annual meeting in New Orleans on pending changes in antimicrobial availability and oversight, disease concerns following those changes, and effective medical care.
By December, antimicrobials used in human medicine will become unavailable for uses in water or feed to promote livestock growth or otherwise improve production, and they will be available only with prescriptions or veterinary feed directives, which are similar to prescriptions. The Food and Drug Administration has called for those changes and indicated all pharmaceutical companies that sell affected products have agreed to comply.
Preventing disease
Dr. Jessica Risser, a veterinarian at Pennsylvania-based Country View Family Farms, said raising a portion of the company’s pigs without antimicrobials has required adaptation. She talks with a farm nutritionist to address or prevent health challenges, works to improve sanitation in barns, and, when considering feed additives, examines whether they have proven benefits in pigs rather than only in other species.
Vaccination practices, nutrition, husbandry, water quality, farm employee engagement, ventilation, and food safety risks need additional assessment when antimicrobials are removed from production, she said.
Dr. Laura Bruner, a practitioner at the Swine Vet Center in St. Peter, Minnesota, suggested eradicating porcine reproductive and respiratory syndrome and mycoplasmosis to reduce antimicrobial use. PRRS is caused by a virus, but antimicrobials are administered to combat secondary infections common among PRRS-infected pigs.
One of Dr. Bruner’s clients eradicated mycoplasmosis among 31,000 sows, after which death rates decreased, the pigs gained weight more quickly, and antimicrobial use declined. She said Mycoplasma infection results in a substantial use of antimicrobials and is a complicating factor when pigs become infected with PRRS virus or influenza virus.
In a Q&A session after the presentations, Dr. Soren Spandet Thielsen of Naestued, Denmark, questioned the wisdom of removing only some production antimicrobial uses on the basis of prohibitions pending for the end of this year rather than also eliminating production uses of drugs considered unimportant for human medicine and unaffected by current regulatory changes. He sees the partial removal as prolonging a painful transition toward an inevitable requirement to eliminate production uses of all antimicrobials on farms.
He elaborated later by email that, given trends across Europe, he expects uses of any antimicrobial in livestock feed or water in the U.S. eventually will require a laboratory-confirmed diagnosis.
Dr. Thielsen also noted that, when growth-promotion uses of antimicrobials were prohibited in Denmark, veterinarians encountered increased numbers of infections with pathogens that had been suppressed. These included acute infections with bacteria such as Lawsonia intracellularis, Brachyspira pilosicoli, and Escherichia coli.
Refining, overseeing use
Veterinarians should search for evidence indicating which antimicrobial treatments will be effective and contribute their own evidence collected from treatment results, according to Dr. Locke A. Karriker, director of Iowa State University’s Swine Medicine Education Center. He warned that antimicrobial use decisions should be based on which drugs will be most effective and safest for the food supply rather than on which would be the easiest alternatives.
The veterinary profession also could reduce antimicrobial exposure by studying the relationships between treatment durations and outcomes, Dr. Apley said.
“Our durations of therapy have been rather arbitrary, and I think we can reduce them,” he said.
In a panel discussion after the lectures, Dr. Apley acknowledged that federal law prohibits extralabel use of antimicrobials in feed, including a treatment duration outside lower limits established on many drug labels. But veterinarians could work with drug companies to determine shorter treatment durations for antimicrobials in the hope the companies may be motivated to seek altered drug approvals that could reduce the risk of drug resistance development.
Dr. Paul D. Ruen, a partner in Fairmont Veterinary Clinic in Fairmont, Minnesota, recommended that veterinarians embrace regulators’ desire for increased veterinarian oversight of antimicrobial administration, which he thinks will provide opportunities to improve relationships with clients, regulators, and the public. Veterinarians also need to consider how they will deliver antimicrobials in an efficient and timely manner once many drugs now available over the counter require veterinary feed directives for purchase.
One pork industry representative predicted that reduced access to antimicrobials will be a problem for pork producers in rural areas. Dr. Jennifer Koeman, director of producer and public health for the National Pork Board, said her organization is trying to educate pork producers and encourage them to talk to veterinarians about which antimicrobials will require veterinary feed directives for use.
Dr. Ruen said he has “fired” two clients he could not trust to use medical products as directed. Veterinarians need to do what is right for pigs and is legal, and not just avoid residues, he said.
The FDA has given veterinarians the ball in terms of antimicrobial stewardship, Dr. Apley said. They will be judged on antimicrobial uses and justifications for those uses, and the veterinary profession should improve collection and analysis of data that can be used for further study, he said.
“With the VFD changes, we’re not only going to be responsible for, essentially, all antibiotic use in food animals,” Dr. Apley said. “We’re now accountable for them.”
Related JAVMA content:
Changes coming in antimicrobial use, availability (Jan. 1, 2015)
Antimicrobial sales rise despite pending changes (Feb. 15, 2016)