Veterinarians want data, targets for antimicrobial use

Lecturers describe continued pressure over drug use following regulatory change
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Veterinarians in North America and Europe are under pressure to reduce antimicrobial administration on swine farms.

Determining which uses are judicious and measuring outcomes are difficult, according to speakers at a March 3-6 meeting of the American Association of Swine Veterinarians in San Diego. They described challenges related to collecting data that could be used to set policy and link changes in antimicrobial use with outcomes in prevalence of drug resistance, as well as those related to policymaking swayed more by opinion than research.

Dr. Mark White, an independent pig veterinary consultant, clinician, and president of the Pig Veterinary Society of the British Veterinary Association, said he has attended years of hostile meetings of other groups on antimicrobial use and questions on which ones are appropriate. He noted that public figures in medicine and politics, in Europe and the U.S., have warned of a post-antimicrobial apocalypse, nightmare bacteria, and deaths by common infections.

At a policy level, the debate has shifted from a scientific one to a sociopolitical one, he said.

"We've got to reduce, we've got to refine, we've got to replace the use of antibiotics in farm animals," he said.

For swine veterinarians, those changes need to occur while preserving pig health, Dr. White said.

"Whatever we're going to do—reducing, refining, replacing, using antibiotics more responsibly—that's another term that's thrown about—but the bottom line is reducing how much we use," he said. "We will have to do that without damaging pig health and welfare, without damaging productivity, and, obviously, without damaging the supply chain."

Precise data needed

Dr. Peter Davies, a professor of veterinary population medicine at the University of Minnesota College of Veterinary Medicine, said the available data on antimicrobial sales in the U.S. and other countries provide no indication whether uses of those drugs are appropriate. But they do provide fodder for misinformation, particularly by allowing what he said are inappropriate comparisons across countries and species.

To illustrate that drug administration can reflect a difference in risk rather than overuse, he noted that antimalarial drug use is higher among people in Uganda than those in Finland. Reducing drug use is an intervention, not an outcome, he said.

Dr. Michael D. Apley, president of the American Association of Bovine Practitioners and a professor of production medicine and clinical pharmacology at Kansas State University College of Veterinary Medicine, said gathering current and granular data ideal for monitoring antimicrobial use would be resource-intensive. But such monitoring could support antimicrobial stewardship in veterinary medicine.

He wants data that show the volume and potency of antimicrobials administered, how many animals were exposed, the duration of administration, and the reasons for use.

How antimicrobial administration is measured will affect changes enacted by legislatures and regulators, Dr. Apley said. Retailers also will use product differences to distinguish themselves.

Dr. Davies described his involvement in a Food and Drug Administration–funded, five-year project to collect data on antimicrobial administration in the poultry and swine industries and evaluate means for analyzing, reporting, and summarizing the data. He noted that Dr. Apley is leading a project collecting similar data on cattle industries.

The poultry and swine data project started in September 2016 with a long-term goal of creating platforms for consistent, sustained on-farm data collection, the project abstract states. Drug stewardship programs need on-farm antimicrobial use data that describe the intensity of use and improve knowledge about indications and administration methods for specific antimicrobial compounds, it states.

The project team has collected data from nine pork production systems and expects data from one more, and those companies constitute about 20 percent of the industry, by sow population, Dr. Davies said. A report on data from 2016 and 2017 may become available this fall.

He expects gathering additional voluntary information on how and why drugs are used, rather than only what drugs are used, will be challenging but important.

In meeting proceedings, Dr. Davies wrote that current debate over prevention uses of antimicrobials are an obvious next step in the discussion of benefits and risks of antimicrobial administration.

"I would argue that prevention as currently practiced in the US industry involves both appropriate and inappropriate ABU," he wrote, abbreviating antibiotic use. "It is a challenge to our profession to understand and communicate the difference, and that there likely is no ‘one size fits all' answer."

The conversation must include animal health and welfare, he wrote.

Dr. White said veterinarians in Europe need to work with clients to improve health, whether through pathogen elimination, biosecurity, changes in pig transportation, vaccine use, shifts in employee attitudes, or other adjustments to practices.

Low and inconsistent margins in the U.K. pork industry have supported fears of removing access to cheap feed-based medication, he said. But producers are finding "courage to cut" antimicrobial use and see whether, for example, weaning pigs need antimicrobials that have been a staple of their diets.

Success will require a global approach, he said.

"As far as I'm concerned as a veterinarian, our aim is to improve health, and the antibiotic reduction will come from there," he said. "We are not looking for reduction for reduction's sake."

Regulatory effects minimal, so far

When the AASV met in early March, livestock industries had been living 14 months with reduced access to antimicrobials and fewer approved uses. The FDA had removed approvals for livestock production uses of antimicrobials that are shared with human medicine and required veterinarian oversight of remaining uses in feed, effective Jan. 1, 2017. Growth promotion and feed efficiency are examples of the now-prohibited uses of affected drugs.

Agency officials removed or modified hundreds of drug approvals under agreements made with pharmaceutical companies and the threat of administrative action against any that resisted.

The changes affected almost 60 percent of the volume, by weight, of antimicrobials sold for use in livestock. Among antimicrobials the FDA deems to be medically important, the changes in over-the-counter availability alone affected 96 percent of the volume sold.

FDA data indicate 31 percent of the volume of medically important antimicrobials sold for use in livestock was intended only for therapeutic indications.

Dr. Elizabeth Wagstrom, chief veterinarian for the National Pork Producers Council, said in an interview after the 2018 AASV meeting that the pork industry prepared in the three years between when the FDA announced plans to change antimicrobial use and when they were implemented in January 2017. Swine producers have been able to maintain the status quo for swine health, and continued availability of antimicrobials for disease prevention uses contributed to that success, she said.

Whether the volume of antimicrobials administered has changed is difficult to say, Dr. Wagstrom said. She noted that the NPPC is working with Dr. Davies on a data collection project that would allow comparison, and the council has supported an antimicrobial use survey. But the most recent available data, the FDA's national antimicrobial sales data, cover sales in 2016. She noted that antimicrobial sales in that year already were lower than in 2015.

Domestic sales figures published by the FDA in December 2017 support Dr. Wagstrom's statements on overall antimicrobial sales for use in livestock, although any species-specific data in the report relate only to 2016 sales.

The overall weight of antimicrobials sold for use in livestock declined about 10 percent from 2015 to 2016. When only counting drugs considered important for human medicine—and affected by the changes in use and availability—the decrease is 14 percent.

Three-quarters of that decline was from a decrease in sales of tetracycline, which accounts for most of the volume of drugs considered important for use in human medicine.

Among antimicrobials shared with human medicine, about 96 percent of the volume intended for use in livestock in 2016 were shipped to be available over the counter, according to FDA data. All uses of those drugs have required a prescription or veterinary feed directive since January 2017.

Dr. Tom Burkgren, AASV executive director, said after the meeting several veterinarians indicated to him the changes in antimicrobial use and availability had little impact outside the need to plan to write more VFDs. But he heard some smaller swine producers had challenges because—astounding to him—they were unaware of the then-new VFD requirements.

He did not remember hearing of any health effects of the change, but he said it may be too early to say whether any will emerge. And he said that veterinarians are getting into some barns that had lacked veterinary services when more drugs were available over the counter.

Related JAVMA content:

Drug changes not affecting pig health, so far (May 1, 2017)