Expert Q&A

Curbing Antibiotic Overuse in Animals

by David Tuller, DrPH  

Maryn McKenna is an investigative journalist who specializes in infectious diseases, global health, and food policy. She is the author of two critically acclaimed books, Superbug (about methicillin-resistant Staphylococcus aureus, or MRSA) and Beating Back the Devil (about the “disease detectives” at the CDC’s Epidemic Intelligence Service). She has written for The New York Times Magazine, Wired, National Geographic, Scientific American, Slate, Nature, The Atlantic, The Guardian, and other publications, and is a senior fellow at the Schuster Institute for Investigative Journalism at Brandeis University.

McKenna’s reporting on infectious diseases led to her growing awareness of the crisis of antibiotic resistance. Her 2015 TED talk on the issue, "What Do We Do When Antibiotics Don't Work Any More?" has been viewed more than 1.5 million times. Her most recent book, Big Chicken: The Incredible Story of How Antibiotics Created Modern Agriculture and Changed the Way the World Eats, was published in September 2017. According to the journal Nature, “this superb scientific expose … skewers the use of growth-promoting antibiotics in chicken feed.” We spoke with McKenna about the history of antibiotic use in agriculture and what is being done to curb their overuse today.

Maryn, what got you started on investigating the impact of the use of antibiotics in livestock?

As a journalist, whether as a newspaper reporter or freelancer, I’ve always worked in public health. I got interested in antibiotic resistance about ten years ago when I was hanging out with people from the CDC and hearing how much of a concern that was. I spent a couple of years digging into how it emerged, and I came across the statistic that in the U.S., in an average year, we sell four times as much antibiotics for use in livestock as for use in people. And I couldn’t make any sense of that. Because how could we be in a situation where we were trying to preserve antibiotics for use in people and yet also be using them so freely in animals? So I decided to try to understand how both those things could be happening at the same time, and that journey led me to writing this book.

How are antibiotics used in livestock production right now?

There are three ways that antibiotics are used in agriculture. As with people, they’re used to treat sick animals and get them well—no one is opposed to that use of antibiotics, including people who are concerned about antibiotic resistance. There is the use of antibiotics for prevention or prophylaxis—to keep animals from getting sick. And then there is the use of antibiotics for growth promotion.

Why did you call the book Big Chicken?

I live in Georgia, which is the heart of chicken production in the U.S. There’s also a restaurant here, an old Kentucky Fried Chicken that everyone refers to as “The Big Chicken.” So the title is kind of a nod to Georgia. But also, poultry are essential to the evolution of farm antibiotic use, because they were the first animals to be fed antibiotics as growth promoters. The scientist who came up with this idea happened to be a biologist whose expertise was in the dietary needs of chickens. He was working for one of the early antibiotics producers and was asked to come up with a feed supplement, and he decided to try leftovers from the process of manufacturing antibiotics. When antibiotics are made, after the growth of the organism is exhausted, you strain off the brine and you’re left with a sticky mass of dead bacteria and leftover carbs that the bacteria didn’t eat. This leftover growth medium contains tiny doses of antibiotics. And it turned out to be an effective growth promoter.

When did that approach start?

We have to go back to World War II, when two things were happening at once. First, the war brought antibiotics onto the international stage. Penicillin was developed in 1941 and rolled out across battlefields in 1943. It saved lots of lives, so there was huge enthusiasm for antibiotics. In that period, there was also a profound change in how we made food. With millions of soldiers to feed and a guaranteed market for protein, there was a giant increase in the infrastructure for growing food because the government had to buy provisions for all the military personnel that it was sending around the world.

As that guaranteed market went away with the end of the war, there was overcapacity in meat production. In order to solve that problem without having the industry collapse, producers switched to growing animals on cheaper feed. To keep the animals healthy, they needed supplements to boost the cheap feed’s nutrition, so suddenly there’s this pressure to find feed supplements. Out of that pursuit, this scientist at the antibiotics maker decided to try the leftover growth medium from the manufacturing process.

And then what happened?

Growth promotion was immediately incredibly popular. The antibiotics company first started selling the dry growth medium, then they started selling the drained-off brine. In his memoirs, the scientist who started this wrote that they started selling railroad tank-car loads full of it. Farmers started demanding the product, and senators started calling and asking why their constituents couldn’t get it. The other antibiotics makers followed very quickly doing the same thing.

Almost immediately when this process started, there were warnings—veterinarians who worked in the first company warned the biologists not to sell these products because antibiotic resistance would result. They were ignored. Antibiotic-resistant foodborne illnesses had never existed before, but the first cases of these appeared in the mid-1950s.

What is the current impact of all this antibiotic use in livestock production?

Antibiotic resistance is pretty universally considered a grave global crisis. It’s been called that by the CDC, by its equivalents in the U.K. and the E.U. The United Nations has called it the “greatest and most urgent global risk.” What fuels antibiotic resistance is misusing and overusing these drugs. We do that much more in agriculture than we do in humans, and all of that is fueling the rise of resistant bacteria.

What about the idea that this is also contributing to the human obesity epidemic?

That is argued over a lot. It’s been shown that low-dosing in mice can have an obesogenic effect. We don’t know if that translates to humans. But it’s a pretty provocative conjecture. One aspect that is not discussed much is that when we take antibiotics some percentage goes through our bodies without being broken down, so we pee out a certain amount of it. Those antibiotics survive sewage treatment. They also survive in plants. One contention is that we are exposed to enough low doses of antibiotics in the environment that it could be having growth-promoter effects on us. This is an emerging field of research.

Where are we in terms of curbing the overuse of antibiotics?

In Europe, there’s been a ban on growth promoters since 2006. The U.S. has just created something similar that went into effect in January 2017. Most of the developing world has no such controls and meat production and sales are growing there rapidly. So that’s a real concern.

In addition, there is no ban anywhere on prophylactic use of antibiotics. In the new U.S. rules, prophylactic antibiotics are supposed to be under the control of veterinarians, but there’s data from Europe to show that doesn’t necessarily curb sales. So as the use of antibiotics as growth promoters becomes illegal, there is concern that meat producers will use the same amount of antibiotics but for prophylactic use instead.

Can you say more about the impact so far of the ban on growth promoters in the U.S.?

There isn’t very much federal data on agricultural antibiotic use. The data set tracks only sales of drugs, not uses. And in addition to being an imprecise measure, it is slow. The reports arrive 12 months after the end of the year they contain data on. Thus the most recent data set contained the data from 2016, the last year before the U.S. ban went into effect. That said, the data in that report did look good. Though the ban was not yet active, sales of all farm antibiotics went down 10 percent between 2015 and 2016. Let’s hope that trend continues.

How about the announcements from fast-food makers that they won’t serve chicken treated with antibiotics? Is that a real promise or is it public relations?

The moves by fast-food chains to serve antibiotic-free meat, mostly chicken so far, have come because of decisions by chicken producers to raise antibiotic-free birds. That is a real development, not spin, and it has changed the industry. A significant portion of the U.S. poultry production is now ABF (antibiotic free) or NAE (no antibiotics ever). The challenge will be whether the pork and cattle industries can follow chicken. Those are more complicated, longer-lived animals that get moved around more in their lifetimes, and thus are more exposed to disease risks. Taking them antibiotic-free will be challenging, but it must be done.

This opinion does not necessarily reflect the views of the UC Berkeley School of Public Health or of the Editorial Board at BerkeleyWellness.com.