by Kirsten Patrick, Deputy Editor, CMAJ, in Victoria, BC
Human beings are often difficult to fathom. In a lecture about the health effects (present and expected) of climate change, David Fisman, infectious disease physician and epidemiologist from the University of Toronto, pointed out that getting people to care about – and take action to reduce – climate change is tough. This is because human beings tend not to like long time horizons. We are consistently happier to have things now and make ‘payment’ later. Even when anyone with rudimentary imagination can, after being shown a little climate change data, see the likely catastrophic cost to human health of not pumping huge amounts of money into mitigating the effects of climate change NOW, we still collectively choose to do very little. The answer would seem to lie in learning how to influence deep-seated psychological desires, rather than trying to beat folks over the head with more data. Needless to say, Fisman’s lecture was scary, but he was preaching to the converted, at least with me. I was more scared when I learned about something I didn’t know a lot about: the nature of antibiotic use in animals.
Some would have us believe that rampant and indiscriminate use of antibiotics in the farming and veterinary sector is the reason we have such bad problems with antibiotic resistance. But it’s much more complex than that. According to Scott Weese of Guelph, ON, Professor at the Ontario Veterinary College and a Zoonotic Disease/Public health Microbiologist at the University of Guelph’s Centre for Public Health and Zoonoses. Weese cautioned against playing the futile cross-discipline blame game when talking about the problems facing antibiotic stewardship.
Antibiotics are widely used in animals for therapeutic indications, prophylaxis, disease control, growth promotion, and feed efficiency. Widely doesn’t cover it, though. We are talking tonnes and tonnes of antibiotics used in animals each year. Yet that doesn’t mean that the use of antibiotics in animals is always inappropriate. There are particular problems.
For one thing, there are many different groups involved in the 'veterinary’ sector, including farmers, food producers, owners and vets. So who drives or directs antibiotic use in animals? The answer is that all those stakeholders do. Economic factors drive food production, which mean that some antibiotics are preferred over others. For example, a dairy farmer will favour using a cephalosporin to treat illness in a herd because there will be no ‘milk withdrawal’ (prohibition of sale of milk for a month after treatment) as there is with other antibiotics. Farmers sometimes rely on heavy use of antibiotics as a crutch to support ‘factory farming’ and that is to be discouraged. That’s difficult to control, though, because antibiotics for animals are widely available for sale over the counter in North America.
Did you know that you can buy antibiotics for fish in a pet store? What’s more, if you want to avoid going to the vet for your sick dog you can buy fish antibiotics and then find an online tool to calculate the dose that you should give your dog! In the U.S. farmers can easily buy antibiotics for animals without limitation (as long as they use them according to label dosage). Conversely, the Canadian federal government controls the sale but, critically, not the use of antibiotics in animals. Canadian farmers can drive across the border, load up on over-the-counter antibiotics and feed them to their animals back home without fear of legal retribution. In fact the Ontario Medical Association called on the federal government to close this loophole last year.
Even the legal requirement for farmers to feed only the ‘on-label’ dose of antibiotic to animals in the U.S. is unhelpful. The ‘on-label’ dose is archaic, calculated when bugs were more sensitive to antibiotics than they are today. Farmers are forced by law, if they buy over-the-counter, to feed their animals sub-therapeutic doses of drug, which comes with its own set of problematic contributions to antibiotic resistance.
Much worse, though, is that many antibiotics marketed to farmers for animals come with claims to promote growth. Recently, however, the FDA released a list of companies and their antimicrobial products that will no longer be allowed to claim growth promotion, the administration of which will require veterinary oversight. This is welcomed by the American Veterinary Medical Association, yet the AMVA website still states that “There is little to no evidence that restricting or eliminating the use of antimicrobials in food-producing animals would improve human health or reduce the risk of antimicrobial resistance to humans”.
Scott Weese disagrees with this statement. The truth is that it is not clear, he says. Some drugs, some animals, some situations...but not all. We might balk at the sheer tonnage used, and without doubt we should try to use many fewer antibiotics in farming, but animals are different and looking only at antibiotic quantities used is not helpful. There are scant good data. There are conflicting data... conflicting claims, between bacteriae, between animal species, between drugs. What everyone seems to agree on now is that there is a need for more data – specifically good species-specific and drug-specific data that go beyond quantities of antibiotics used in animals.
We should not assume that the direction of travel of bacterial resistance is always from animals to humans. Weese described cases he had seen of companion animals picking up resistant bacterial infections from their humans, often owners who have been on long term antibiotics or who are immunocompromised. Bacterial resistance is a problem for all species and joined up efforts to control development of resistance are needed.
So what does Weese recommend? Don’t blame, either other stakeholders or poor data. Everyone can assume responsibility for good antibiotic stewardship, and everyone can be judicious with prescribing. Close legal loopholes, take growth promotion claims off labels, and collect decent epidemiological and usage data. Influence farmers to avoid using antibiotics as a crutch to support poor animal farming practice. In Canada, a federal approach to regulating antibiotic use (rather than provincial policy-making) would help to facilitate working together across medical-agricultural-farming sectors.
Yes, I hear those of you who are shouting at the screen about how people successfully farm animals for meat that is ‘antibiotic free’ … people are happy to pay a higher price for this option so why not promote antibiotic-free farming? Weese pointed out that ‘antibiotic-free’ animals are routinely pumped full of zinc to control infections. Zinc is also antimicrobial, though, and has been associated with MRSA selection. And the effect of banning prophylactic tetracycline in food animals would be a bit like squeezing a balloon. If incident infection rates increased in animals as a result, more important drug classes would need to be used for treatment.
All of which brings me back to climate change and an obvious conclusion…. IF farming animals using routine antibiotics in feed worsens the problem of development of antibiotic resistant bacterial strains – and we don’t know for sure that it does because the data aren’t generally good – and IF tightly controlling and reducing antibiotic use in animal farming would drive up the cost of meat, then wouldn’t it seem obvious to put a lot of energy into convincing humans to eat Much Less meat? ...Which would also help a lot to reduce greenhouse gas emissions…? I’m just saying.
I know. It’s not about finding logical solutions. It’s about managing and influencing deep-seated psychological fears related to lost profits, lost livelihoods, and the perceived lowering of standards-of-living.