Antimicrobial sales decline on farms
In 2017, livestock industries bought one-third less of antimicrobials in the same drug classes as those given to people.
The amount, by weight, of those drugs sold for use in livestock dropped 33 percent from 2016, a single-year difference of 6 million pounds, according to a Food and Drug Administration report published in December 2018. Sales of those drugs also dropped 14 percent from 2015 to 2016, for a two-year decline of 43 percent.
Ron Phillips is vice president for legislative and public affairs for the Animal Health Institute, a pharmaceutical trade organization. He said various factors affect sales and use volumes, totals of which can differ. But he said the decline in sales reflects efforts to use those drugs only where needed.
Leah Wilkinson, vice president of public policy and education for the American Feed Industry Association, provided a statement saying that the reductions in drug sales likely were related to the FDA's changes regarding drug approvals in 2016 and to the public's demand for reduced use of antimicrobials in food-producing animals.
In December 2016, FDA officials removed all over-the-counter access to antimicrobials that are both used in human medicine and given to livestock in feed or water. Use of those drugs for production purposes, such as growth promotion, was also eliminated. Those drugs now can be given only with veterinarian approval for disease-related reasons.
FDA officials were unavailable to talk about the report in late December and early January, when federal agencies furloughed workers as a result of the government shutdown.
Sales, use differ
In December 2013, FDA officials proposed revising hundreds of approved drug applications to end what they saw as improper drug uses that contributed to drug resistance. The affected drug makers agreed under the threat of regulatory proceedings.
The changes affected drugs the agency lists as "medically important" because of their usefulness in human medicine. December's report indicates the decrease in sales of those drugs coincided with a 5 percent drop in sales of agriculture-use antimicrobials that are considered medically unimportant, especially ionophore-class drugs.
FDA officials also announced in 2018 plans to require prescriptions to access the remaining medically important antimicrobials available over the counter, now about 5 percent of all such drugs, and develop recommended treatment times for those drugs for which guidance is absent.
A year ago, AVMA leaders enacted a policy that says veterinarians can preserve effectiveness and availability of antimicrobial drugs through oversight of drug use and responsible decisions. The policy, "Antimicrobial Stewardship Definition and Core Principles," states that stewardship involves disease prevention and management as well as drug use that is evidence-based, sparing, and completed with evaluating outcomes.
Dr. Michael Costin, assistant director of the AVMA Division of Animal and Public Health, said that, in 2019, the AVMA Committee on Antimicrobials will monitor Federal Register notices related to the FDA's strategy on antimicrobials and prepare positions and responses.
Dr. Michael Apley, a professor of pharmacology at Kansas State University and immediate past president of the American Association of Bovine Practitioners, cautioned that many factors could contribute to declines in antimicrobial sales, among them differences in animal health and population sizes. But he also heard from cattle veterinarians that the drug approval changes had led to discussions with clients about when drugs can and should be used, and he had expected to see a decrease in tetracycline sales.
Tetracycline drugs have made up the bulk of medically important antimicrobials sold in agriculture since the FDA began collecting data in 2009. That remained true in 2017 despite a 40 percent drop in sales since 2016, a difference of more than 5 million pounds.
Dr. Apley also said the data provide no indication how changes in antimicrobial use affected animal welfare. If animals are receiving less antimicrobials, he wants to know how that is changing illness and death rates.
Phillips, of AHI, said that, while the sales decrease is evidence of the impact of judicious use, efforts to improve use should continue. He expects an FDA report this year will provide some analysis of drug resistance surveillance, sales data, and use information.
Effects on resistance unknown
Reports from the Department of Agriculture's National Agricultural Statistics Service show drug sales declined even though populations and production were stable across major livestock industries. From 2016-17, NASS data show slight rises in cattle inventories, milk production, milk produced per cow, beef production, swine inventories, pork production, layer hen populations, egg production, broiler chicks hatched, and chicken meat production, while the number of turkeys declined about 0.5 percent and turkey meat production was unchanged.
At the same time, the FDA data show the amounts of medically important antimicrobials sold for use in cattle and swine each dropped 35 percent, the volume sold for use in turkeys dropped 11 percent, and the amount used in chickens dropped 47 percent.
Consumer Reports' advocacy division, formerly Consumers Union, published a statement that the sales report shows that FDA oversight and market pressures are curbing misuse of critical medications. The organization called on beef and pork industries to further reduce administration and preserve drug effectiveness.
Jean Halloran, director of food policy initiatives for Consumer Reports, said in an interview that the sales declines in the beef and pork industries were better than expected. In the chicken industry, companies had pledged to reduce use and she was pleased the sales data bore out those promises.
She expressed hope the improvements made in the chicken industry will be replicated in the turkey, cattle, and swine industries.
Dr. Suzanne Dougherty, executive vice president of the American Association of Avian Pathologists, said knowing which species received a drug is difficult even without considering extralabel use.
While drug administration likely decreased, she said the amount of reduction and its causes are difficult to attribute. The sales data likely are influenced by sales of meat from birds raised without antibiotics, removal of growth promotion–use antimicrobials, and implementation of veterinary feed directives, she said.
"We are concerned about antimicrobial resistance, and we would like to see data if the reduction of antimicrobial use is improving any of the resistance," Dr. Dougherty said.
Asked whether changes in health could contribute to the difference in sales, Dr. Dougherty said poultry industries continue improving management of their birds to reduce disease, but she knew of no specific and substantial health or disease changes that would influence the antimicrobial sales. She said poultry veterinarians are cautious to use medically important antimicrobials only when necessary.
Dr. Harry Snelson, communications director of the American Association of Swine Veterinarians, said it's always good to see a decline in antimicrobial sales.
"Certainly, as veterinarians, what we're interested in is how these products are actually used on the farm—and are there on-farm use practices that could contribute to increased antimicrobial resistance in the animal or human population?" Dr. Snelson said. "And what we want to know is how to identify those practices and alter those practices to minimize the risk of antimicrobial resistance."
The AASV supports efforts at the USDA, for example, to examine administration practices on farms, he said.
Dr. Snelson shared others' caution about extrapolating sales data. But he also said the decrease in sales reflects responses to drug stewardship policies published by AASV and other veterinary groups, as well as the restrictions mandated by the FDA.
"Obviously, if there's fewer products sold, it's likely there's fewer products actually being used," Dr. Snelson said.
But how a product is used—rather than how much is used—is connected with resistance development and animal health, he said.
"Do you have adequate diagnostics in place to make the appropriate antimicrobial selections, and are those antimicrobials applied in a judicious and responsible use manner?" he said.
Related JAVMA content:
FDA may change drug uses in 5-year plan (Dec. 1, 2018)
AVMA defines stewardship, judicious use (March 1, 2018)
Changes coming in antimicrobial use, availability (Jan. 1, 2015)
FDA restricting antimicrobial uses in livestock (Jan. 15, 2014)