The World Organization for Animal Health Health (WOAH, formerly the OIE) has issues a call to countries to live up to their commitments to phase out the use of antimicrobials for growth promotion in animals. This is low-hanging fruit in terms of antimicrobial stewardship that you’d think would have been addressed by now, but is still an issue in some countries (but was phased out in the US in 2017 and in Canada in 2018).

Let’s review some of the language and terminology around how antimicrobials are used:

In animals, antimicrobials can used to treat existing clinical infections (therapy), to prevent infections in high-risk situations (prophylaxis), and to treat animals that are at high risk of already being infected but are not yet sick (metaphylaxis). Those are all considered veterinary uses for antimicrobials, and they’re all justifiable under the right circumstances (though there are still concerns about overuse, particularly with metaphylaxis and prophylaxis).

Unfortunately, antimicrobials are also still used in some places to promote growth of food-producing animals. That kind of use has nothing to do with prevention or treatment of disease. Instead antimicrobials are used in these cases to alter the intestinal microbial populations of the animals, which can result in better growth rates. From a production standpoint, that can be good, but it increases the risk of antimicrobial resistance developing, which can impact animals, humans and the environment.

Another key term is “medically important” antimicrobials, which are those that are the same drug or in the same drug class as antimicrobials used in humans.  If resistance to these drugs develops through their use in animals, that could pose risks to humans. So we definitely do not want medically important antimicrobials used simply for promoting animal growth; they need to be reserved for when they’re really needed (in either animals or people).

The World Health Organization (WHO) categorizes all antimicrobials as either medically important or not medically important, and classifies the medically important antimicrobials into different priority levels (a revision of this classification will be released soon). Pretty much all of the antimicrobials that are used for treatment, prevention or metaphylaxis in animals are medically important, and some of these are also used for growth promotion. There are also various not-medically important drugs that are used for growth promotion. Resistance concerns regarding the use of the latter are low, but not zero, as there’s still potentially an environmental impact (pretty much completely unknown at this point), and we can rarely say there’s absolutely no risk of cross-resistance or co-selection of resistance to an unrelated medically important drug.

In 2016, WOAH member states agreed to stop the use of “highest priority critically important antimicrobials” (HPCIAs) for growth promotion in animals and phase out the use of all antimicrobials for growth promotion “in the absence of a risk analysis.

What’s happened since then? Not enough:

  • 20% of member countries still report the use of antimicrobials for growth promotion in livestock.
  • It’s estimated that 76% of those countries have not done a risk analysis to try to identify risks and justify their antimicrobial use.
  • At least 50% of these countries have no regulatory framework to regulate use of antimicrobials for growth promotion.
  • In some countries, antimicrobial-containing feeds are not labelled, so farmers and veterinarians may not always know that they are feeding antimicrobials to their livestock (which raises a variety of issues)
  • 11% of member countries reported still using HPCIAs for growth promotion in livestock. This includes the use of colistin, an ol antimicrobial that’s become a drug of last resort for some life-threatening, highly drug-resistant infections in people. That’s a big concern.

Phasing out antimicrobials for growth promotion should be a no-brainer, particularly phasing out such use of medically important antimicrobials. WOAH’s new statement is pretty clear:

WOAH calls on its Members to restrict the use of antimicrobials solely to veterinary medical use and to actively engage in dialogue with the concerned parties to achieve a total ban on the use of antimicrobials as growth promoters, starting with those that are critically important for human health.”

Is improving animal production important? Yes, particularly in developing countries. Yet, there are better and more sustainable ways to do that than feeding animals antimicrobials for no other reason than improving their growth.