Continuing my World Antimicrobial Resistance (AMR) Awareness Week series, let’s talk about antimicrobial prophylaxis in animals.

If you asked random people on the street “Should antibiotics be given to healthy animals?” I’d expect the answer to be a resounding no. But, as with most things related to AMR, the answer is not as simple as it seems.

Prophylaxis (or “preventive treatment”) is a very broad categorization of antimicrobial use (AMU) that lacks a consistent definition, but a  a consistent component of most definitions is administration of antimicrobials to healthy animals that are deemed (rightly or wrongly) to be at increased risk of bacterial infection, where prophylaxis is assumed (rightly or wrongly) to be able to reduce the risk of disease.

Prophylaxis encompasses a large percentage of the antibiotic use in animals, particularly in food animals. Prophylactic antimicrobials are massively overused, often (for various reasons) when they’re not needed, and not uncommonly as a crutch to compensate for poor management or husbandry practices that increase the risk of disease.


Is there any role for antimicrobial prophylaxis in animals?

When we talk about prophylaxis at international interdisciplinary tables, there’s very often an attitude of “Just stop using antimicrobials prophylactically in healthy animals. Next topic.” I understand that, because at face value, it makes no sense to use antimicrobials in healthy animals.

But… there are some buts. Not all prophylactic use of antimicrobials is the same. Most of it can likely be stopped or reduced, but some is necessary. Appropriate prophylaxis applied in a targeted manner in high-risk situations for bacterial infections (that can’t necessarily be prevented through other means) can reduce animal illness, death and welfare concerns. It can also potentially decrease overall AMU if it prevents the need for therapeutic courses of antimicrobials later on (which may require more use of higher tier drugs for a longer time).

However, with large scale use, use that is poorly targeted, use that is not based on proper risk assessment, and when antimicrobials are used in lieu of improvements in animal management and preventive medicine, prophylaxis is harder to justify.

Accordingly, efforts to assess, reduce and optimize prophylaxis are warranted, but complete cessation of it isn’t going to be practical or necessarily beneficial overall.

When someone thinks about antimicrobial prophylaxis in animals, they probably think about a large barn with thousands of animals that are getting treated en masse. That’s just one example though. There are different types of prophylaxis, with different risks and benefits, including scenarios such as:

  1. Administration of antimicrobials to a group of animals in a routine manner because of a high endemic rate of a specific disease in the group.
  2. Administration of antimicrobials to a group of animals in response to a specific, defined disease threat that is known to be mitigated through a targeted prophylactic course of antimicrobials.
  3. Administration of antimicrobials to a group of animals as a routine practice for most or all animals at a high-risk stage of life or production (e.g. tetracycline treatment of pigs at the time of weaning to prevent post-weaning diarrhea, intramammary antibiotic treatment of dairy cattle at the end of lactation).
  4. Administration of antimicrobials to a specific individual animal at a specific and well defined high risk time.

#1 can be addressed through other means or may not be useful at all. It’s often done because that’s the way it’s been done, not because there’s any evidence it’s needed. This type of prophylaxis would be the top priority to phase out.

#2 might be addressed reasonably through prophylaxis, but it also might be better addressed through management changes, vaccination and other approaches. Prophylaxis might be needed in the short term as other measure are implemented.

#3 would need more investigation since it’s such a wide area, but there could be substantial decreases, if not total replacement of antimicrobial use. It might require non-antimicrobial treatments, vaccination, changes in management and (most of all) behavioural change (the human brain being the biggest barrier to better antimicrobial stewardship in most situations).

#4 is necessary in many situations. We overuse antimicrobials in this scenario, but there are some situations where the benefits of a short course (or single dose) of antimicrobials greatly outweighs the risks, particularly for high risk surgical procedures.

Prophylaxis absolutely needs to be a focus for antimicrobial stewardship strategies in animals (and humans). However, we can’t just say “stop it” – we should be aiming to massively reduce but not completely eliminate it.

We also can’t say “change it all now.” We could have a massive impact on prophylaxis immediately with no disruption to animal health or production, since much prophylactic use is unnecessary. However, to achieve further decreases without adverse animal health and welfare impacts, we need to improve animal management, infection control, access to veterinary care, access to vaccines and alternatives, and support (logistical, technical, financial) to make these necessary changes. That’s particularly true when we look at the issue internationally. A farmer in a low/middle income country can’t make massive changes without support, or we’re going to run into serious food security and economic issues. This is why we have to step up and do more than say “just stop it.” Yes, we need to provide motivation and pressure, and we need to have some degree of regulation. But, we need to provide support so we can massively reduce the misuse and overuse of prophylactic antimicrobials. It’s feasible, but it’s not as simple as the sound-bite approach to AMR might have people think.