Aug 8, 2018 addendum: updated versions of the CARSS report are available here:



The 2017 Canadian Antimicrobial Resistance Surveillance System (CARSS) report was just released, and as always it contains a lot of data (up to and including 2016). Some are interesting, some are concerning, some are encouraging.

I’m not going to try to distill a 90 page report into a quick blog post, so I’ll cover a few part separately. Let’s start with the Antimicrobial Use in Animals section. Here are some highlights (and some comments):

In 2016, ~1 million kgs of medically important antimicrobials (MIAs) were distributed for sale in Canada.

  • This misses some antibiotics that get used via certain regulatory loopholes, but those are being closed soon and this number is probably a pretty good overall estimate.
  • The great news is this is 14% lower than 2007 and 17% lower than 2015

600,000 kg of ionophores and chemical coccidiostats were also distributed in 2016.

  • These drug categories are often lumped in with other antimicrobials (sometimes to make things look scarier) but they are irrelevant from antibiotic-resistance and public health standpoints because they are not used or even related to any drugs used in human medicine. So, it’s good to see them separated out (and to essentially ignore them).

99% of antimicrobials used in animals were intended for use in food animals, based on weight (kg).

  • This is always hard to interpret and sometimes leads people to think that companion animal use is irrelevant. We have to be a bit wary focusing just on kilogram data (1 kg of antibiotic treats a lot more Chihuahuas than cattle). The main antibiotic classes used in companion animals were cephalosporins, beta-lactams and trimethoprim-sulfa – all drug classes of high importance.
  • What this shows to me is that we can have a huge impact on overall use by focusing on food animals. However, the drugs that are used in pets are often the same as those used for serious infections in people, and we share bacteria more readily with our pets. So this number shouldn’t be taken as an indication to ignore them.

Fluoroquinolone use decreased by 56% from 2015 to 2016.

  • Wow. That’s great, since this is one of the biggest classes we’re worried about. They’re important drugs (for both humans and some animal species) but are prone to overuse.

Antibiotics intended for use in feed accounted for 76% of the overall volume of antimicrobials distributed. At the opposite end of the spectrum, intramammary drugs (used for mastitis in cattle) accounted for <1%.

When everything is put together, based on weight, 78% of antimicrobials distributed or sold in 2016 were for food animals, 20% were for humans, 1% for crops and 1% for companion animals.

  • Again, be somewhat wary of these crude numbers.  Remember that the relevance of a kg of tetracycline is probably much, much less than a kg of a fluoroquinolone, and that there are approximately 19 times more animals in Canada (excluding farmed fish) than humans (also based on weight).  Still, these data provide some idea of how we use antimicrobials in this country and they give us numbers for comparison over time. (The 2nd figure below is an interesting one to think about.)

Some people will take these numbers and use them to spin certain agendas. However, we’re better off using them as the basis for more surveillance, more interventions and more research to reduce and improve use of antibiotics in Canada, whatever species they go into (including humans).