Measuring how much antimicrobial medication is given to food animals is key to understanding how to slow antimicrobial resistance, when dangerous microbes get so used to antimicrobials that they evolve stronger defenses against them. However, measuring the actual antimicrobial use in animals on a large scale is still a logistical challenge. Because data on antimicrobial sales for use in food animals are easier to obtain, they are frequently used at the national levels as proxies for antimicrobial use. In a first-of-its-kind study published recently in the Journal of Antimicrobial Chemotherapy, scientists at the Cornell University College of Veterinary Medicine analyzed four different measurement methods used across the globe in the hopes of steering governing groups toward a more unified system. The study was supported by The Pew Charitable Trusts.
Each governing group used similar equations to calculate how many veterinary antimicrobials were sold for use in food animals each year—but with a few key differences, and no one method was a silver bullet, said Renata Ivanek, associate professor of population medicine and diagnostic sciences. "Our study will aid the global action against antimicrobial resistance," Ivanek said.
Ivanek and Dr. Ece Bulut, post-doctoral fellow in Ivanek's lab, looked at methods used by the FDA, the European Surveillance of Veterinary Antimicrobial Consumption (ESVAC), the Public Health Agency of Canada (PHAC) and the World Organization for Animal Health (OIE); using each one with U.S.-specific antimicrobial sales and livestock data. "We are grateful to the experts at the FDA, ESVAC, PHAC and OIE for help with details about their methods," Ivanek said.
Overall, the scientists found that the FDA's method had a higher level of detail when estimating the total animal weight in a country, while the OIE's method was easier to use and apply to many countries around the world, with the two other methods falling roughly in between the FDA's high level of resolution and the OIE's ease of comparability.
Each method employs a similar formula: The total kilograms of antimicrobial sales in a year for a food-producing animal species in a country is divided by total weight of all animals of that species (i.e., biomass) present in a year. The resulting number is the total amount of antimicrobial sales per kilogram of animal weight in a year.
All four methods use national antimicrobial sales, animal population data and average weight of animals in a country for their calculations for estimating weight-adjusted antimicrobial sales per animal category.
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