Sales and distribution of medically important antimicrobial drugs used in US livestock rose 16% from 2023 to 2024 but is still 27% lower than peak sales in 2015, according to the newest report from the Food and Drug Administration’s (FDA’s) Center for Veterinary Medicine.
The increase is a departure from the generally stable annual sales and distribution data reported to the FDA since 2017. For reference, last year’s report showed a 2% decline in sales.
“Sales volume may fluctuate over time in response to various factors, including changing animal health needs, changes in animal populations, and changes in animal production practices,” the news release said. “It is important to note that antimicrobial sales data do not necessarily reflect how much of the drugs are ultimately used in animals, only the volume that is sold.”
Medically important drugs are monitored because they are also used in human medicine.
Overuse of medically important antibiotics in livestock contributes to a reservoir of antibiotic-resistant bacteria, which threatens both animal and human health. This issue has been acknowledged by both US and international health organizations as a critical component of efforts to address rising rates of antimicrobial resistance (AMR).
Over two-thirds of antibiotics were tetracyclines
Sales of aminoglycoside antibiotics jumped 37% from 2023 to 2024. Tetracyclines, which make up the largest volume of domestic sales, increased 20%, followed by lincosamides (11%), and macrolides, which comprise the second-largest volume (1%). Penicillins, which represent the third-largest volume, fell 14%.
Of all antibiotics sold, 69% were tetracyclines, 8% were macrolides, 7% each were penicillins and aminoglycosides, 5% sulfonamides, 3% lincosamides, and 1% for cephalosporins, and less than 1% for fluoroquinolones.
“In terms of [medically important] drug classes, the increases were pretty widespread and all are troubling,” Steven Roach, director of the Safe & Healthy Food Program at Food Animal Concerns Trust (FACT), told CIDRAP News.
About 43% of antibiotics were sold for use in swine, 41% for cattle, 11% for turkeys, 4% for chickens, and 2% for other or unspecified species. By antibiotic class, 79% of cephalosporins, 60% of aminoglycocides, 42% of tetracyclines, and 38% of sulfonamides were meant for cattle. Roughly 89% of lincosamides and 45% of macrolides were intended for swine, and 81% of penicillins were sold for use in turkeys.
“In terms of species, the increases were across the board, with the largest increases in chicken but cattle and pigs still account for most use by far,” Roach said. “The poultry industry claims the rise in chicken is largely due to secondary infections linked to avian metapneumovirus but acknowledges the limited efficacy of the antibiotics. It is hard to see how this could account for the almost 80% rise in use.”
After all over-the-counter animal antibiotics were pulled from the market between 2022 and 2023, sales dropped to zero.
Macrolides led the number of medically important drug applications (27), trailed by tetracyclines (26), sulfonamides (17), and aminoglycocides (15). Tetracyclines made up 58% of drugs delivered through feed and 11% of those delivered through water.
“At FACT, we attribute it to a failure to put in place common sense steps such as eliminating antibiotic use in animals without diagnosed bacterial infection and failure to set targets for reduction in antibiotic use either by the meat industry or the federal government,” Roach said.
More intense antibiotic use
The report also features an interactive chart on 2024 biomass-adjusted sales data, which adjusts raw annual antibiotic sales data to account for the total mass (the estimated population multiplied by the average weight) of each animal species that may have received those drugs. Animal biomass adjustment gives context to antibiotic sales data by accounting for the size and makeup of animal populations, which can change from year to year.
That chart shows biomass-adjusted sales, which indicate the intensity of antibiotic use in livestock, rose for several antibiotic classes in 2024 after falling in several categories in 2023. Biomass-adjusted sales of aminoglycosides, amphenicols, cephalosporins, fluoroquinolones, lincosamides, sulfonamides, and tetracyclines all rose in 2024.
“Sales for use in cattle has stayed about the same, but cattle numbers are down the last three years resulting in more intensity of use,” Roach said. Roach said biomass-adjusted sales for use in pigs have consistently increased, outpacing increases in herd size.
“Turkey sales until last year had creeped up a little and then last year jumped a lot,” he added. “Chicken had consistently dropped year after year until the huge reversal last year. So, I would characterize sales outside of chicken creeping up until last year when they all rapidly increased.”
The FDA has produced the report each year since 2008, when legislation was enacted to require sponsors of approved or conditionally approved applications for new animal drugs with an antibiotic as an active ingredient to inform the FDA of the amount of each antibiotic in each drug.
