Canadian Poultry Magazine

All things considered: April 2010

Jim Knisley   

Features New Technology Production

The Antimicrobial Debate

Years ago a columnist friend interviewed the premier and then the leader of the opposition on a very controversial subject.

Years ago a columnist friend interviewed the premier and then the leader of the opposition on a very controversial subject.

Upon leaving the premier’s office he concluded that the premier was a very smart guy, with a complete understanding of the issue and a sound and sensible way to address it.


Upon leaving the leader of the opposition’s office my friend concluded that the leader of the opposition was a very smart guy, with a complete understanding of the issue and a sound and sensible way to address it.

The only problem was that these very smart people were in complete and total disagreement.

As I plowed my way through studies and reports on antimicrobial resistance and its relationship to the animal agriculture, I concluded that, except for the politically motivated fringe groups, the writers, scientists, doctors and veterinarians are all very smart people with an understanding of the issue. The collective expertise is stunning. The only problem is that they disagree.

This issue has been around for quite some time. It broke into the public, again, with two CBS News reports in early February.

It’s clear that CBS News was convinced that antimicrobial resistance is an important issue worthy of broad public discussion and debate.

If discussion and debate was the goal, they succeeded.

Unfortunately, the debate leaves much to be desired. At times, it’s as if the two (or more) sides were shuffled into separate soundproof rooms where they can see, but not hear, each other.

Lost in the din is the possibility that they may not even be addressing the same questions.

One question seems to be whether the use of low dosage antimicrobials in livestock feed helps maintain animal health and, as a consequence, results in higher quality and less expensive food for humans. The answer appears to be yes.

Another question is whether antibiotic use in agriculture has contributed to antibiotic resistance in bacteria in humans. The answer again appears to be yes with the qualifier that “the chain from cause to effect is long and complicated.”

Both sides in the debate offer, to my mind, very convincing arguments.

For example, a letter to the White House, from all the major U.S. veterinarian and livestock associations, cited a host of studies and said: “Optimal animal health and welfare leads to the production of safe, affordable and abundant food.”

It added that, “despite the unsubstantiated allegations surrounding these uses, no conclusive scientific studies have been offered demonstrating the use of antibiotics on farms contributes significantly to an increase in human resistance.”

A counterpoint is provided in a paper by David Smith, a epidemiologist with the U.S. Institutes of Health, Jonathan Dushoff from Princeton University and the National Institutes of Health, and J. Glen Morris Jr., a physician and epidemiologist at the University of Maryland School of Medicine.

They wrote, in a 2005 report, “even very rare transmission resulting from agricultural antibiotics may have a medical impact by introducing new resistant variants to the human population.”

And they say that once one of these rare transmissions from animals to humans occurs, the human-to-human transmission can be rapid.

They also clearly point out that there is a higher risk of picking up an antibiotic-resistant bacteria in a hospital than from food or from a farm. But, they say that many more people may be exposed to the low risks than the high (hospital) risk.

As a general principle, they say: “A large number of people exposed to a small risk may generate many more cases than a small number exposed to a high risk.”

However, they acknowledge the limits of science in assessing risks. “In this case, the effects of agricultural antimicrobial use on human health remain uncertain, despite extensive investigation and the effects may be unknowable, unprovable, or immeasurable by the empirical standards of experimental biology.”

They conclude that the biological complexity of the problem combined with the “intrinsic problem of knowability” makes caution a suitable response. “The assumption that plausible dangers are negligible, even when it is known that such dangers are constitutively very difficult to measure, may be more unscientific than the use of precaution.”

So, we have one group saying that the use of antimicrobials in agriculture offers clear benefits and that there are no conclusive studies demonstrating there is a problem, while others say that there may never be a conclusive study, but that doesn’t mean there isn’t a problem. In other words, very smart people with an understanding of the issue disagree.

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