The US Food and Drug Administration (FDA)’s 2022 Summary Report on Antimicrobials Sold or Distributed for Use in Food Producing Animals has been released. It includes some good signs and some bad signs in terms of curbing antimicrobial use (AMU) in the US, but it’s clear we still have a lot of room to improve.

Here are a few highlights from the report (all referring to the US, of course):

• Antimicrobial use in food animals, based solely on sales and distribution, decreased on a mass (kg) basis by 36% since 2015 (which was the last peak in this measure of AMU).
• Antimicrobial use increased 4% from 2021-2022.

Comparing to the 2015 historical high and saying “we’re doing a great job” isn’t really a good approach. It’s useful for context, but the year-to-year increase from 2021-2022 is more of a concern, as we really should be aiming for substantial year-to-year decreases in AMU.

For any 2020-2023 data, we always need to ask the question “what was the effect of COVID-19?” We really don’t know in this case, but there could have been impacts on sales and use because of changes in animal management and access to veterinary services. So, I wouldn’t read too much into the 2021 blip; it’s not a great sign, but it’s possibly something we’ll see corrected given some time. We’ll see.

• The increases antimicrobial sales in 2022 were largely driven by increased sale of tetracyclines, the most common drug class used in livestock, and the one that is probably most ripe for reduction because of its frequent use for prophylaxis.
• Sales of penicillins decreased by 1%, while sales of aminoglycosides increased by 10%, macrolides increased by 8%, and lincosamides increased by 11% (see figure below).

This raises some concern. From an antimicrobial stewardship standpoint, we’d like to see decreases in sales and use of higher-tier drugs. Here, we’re seeing the opposite: a decrease in sales of lower-tier penicillins with increases in sales of some higher-tier drug classes.

• The swine industry was the leading consumer, accounting for 43% of total antimicrobial sales for use in animals, closely followed by cattle at 41%.
• The poultry industry continues to use relatively limited amounts of antimicrobials, with chickens accounting for 2% and turkeys for 12% of sales.

This is unsurprising, and also highlights where we can have the biggest impacts in terms of reducing AMU. It also shows how poultry farmers have lead the way by reducing AMU aggressively and voluntarily.

The graph below shows the different antimicrobial classes used in each species, which is an important consideration. It highlights the dominance of tetracyclines, particularly in swine and cattle. While massive amounts of antimicrobials are used in animals, most of the use is lower-tier drugs like tetracyclines. These drugs are still important in people, but are not as critical as other drug classes as tetracyclines are not typically key treatments for serious disease in humans. The WHO has a prioritization process to categorize different antimicrobial drug classes to help with assessments like this (and an updated version is due to be released imminently).

At the same time, we need to remember that mass isn’t everything, especially when it comes to AMU. In many ways, I’m less concerned about that big fraction of tetracyclines than I am the small fractions of cephalosporins and fluoroquinolones. The latter are important drug classes in humans, and we know that use in animals can contribute to antimicrobial resistance (AMR) in human pathogens. So that small degree of use in animals might have a disproportionate impact on AMR overall. It’s one of the reasons that crude mass-based metrics like this aren’t good a good way to set targets for AMU, but they get used because they’re the easiest to measure.

• All medically important antimicrobial were used for “therapeutic indications,” as a result of the ban of use of antimicrobials for growth promotion in 2017 (see figure below).

That’s good. Non-veterinary/non-therapeutic use of medically important antimicrobials isn’t needed, so it’s low hanging fruit when it comes to reducing AMU. However, we have to acknowledge that “therapeutic use” is a designation, not necessarily what was actually done, as there’s still massive overuse of antimicrobials in animals in situations where there’s no evidence that there would be a therapeutic effect (including prophylaxis).

Ultimately the FDA report provides some mixed signals overall. We’ll need to see how things develop over the next few years to determine if there was a COVID-19 effect on these data. Regardless, it’s abundantly clear that we still have a lot of room to improve, and we need to act now.

Zero antimicrobial use in animals isn’t a realistic goal. We need to use antimicrobials for animal health and welfare purposes, but we need to use them better.

I’d guess that a substantial amount of antimicrobials that are purchased for use in animals are actually used to “treat” people: they make the user feel better for doing something, while doing little or nothing to actually make the animal feel better in many cases. We have lots of situations where antimicrobials are needed in animals, but we still have massive overuse that needs to be eliminated.