An Interview About Antibiotics and Agriculture

Since I'm off to Woods Hole to give a lecture about antibiotic resistance, I thought this interview from the old site with Dr. Henrik C. Wegener about antibiotics and agriculture would be appropriate.

In looking through some things at work, I came across this interview with Henrik C. Wegener, Ph.D., Director of the WHO Collaborating Centre for Antimicrobial Research and Foodborne Pathogens and the Danish Institute for Food and Veterinary Research about antibiotics and agriculture. It's from 2004, but it's still pretty good (it's interesting how, on the internet, once something gets past two weeks, it's considered old, regardless of whether it's two weeks or two years old). The interview in the original can be found here(warning: it's a pdf). Italics are mine.

In 1998, when Denmark began banning antibiotic growth promoters from poultry and swine production, the world took notice. Four years later, a World Health Organization international review panel report deemed the bold national intervention a success, with "no serious negative effects," both in terms of economics and animal illness. According to the panel, "The program has ... been very beneficial in reducing antimicrobial resistance in important food animal reservoirs. This reduces the threat of resistance to public health. From a precautionary point of view, Denmark's program of antimicrobial growth promoter termination appears to have achieved its desired public health goal."1

One of the leaders in Denmark's long campaign to reduce animal antimicrobials and protect human health has been Henrik Wegener, head of the Department of Epidemiology and Risk Assessment at the Danish Institute for Food and Veterinary Research. A veterinarian and microbiologist, Wegener had the right credentials to persuade animal producers that they needed to change their medicating ways. "It helped in getting the message across to those who needed to act -- in this context, the veterinarians and farmers," he said. "When medical doctors tell veterinarians what they should do, the vets say, 'Oh, you're always blaming us for everything.' But when the message came from their own ranks, it was not just, 'This is wrong because of public health,' but rather, 'This is wrong because of public health -- and by the way, you don't need those drugs.'"

Q: How much did Denmark reduce total antibiotic usage in farm animals, and how much did antibiotic resistance in the animals decrease as a result?

A: In this country, the reduction in total antibiotic use was 54%. In terms of reducing resistance, it depends on what you look at. In poultry, it's striking how marked the effect has been. When you look at vancomycin- resistant enterococci that had been selected for by the use of avoparcin as a growth promoter, we came from a situation where 70-80% of the flocks had VRE [vancomycin resistant enterococci]; all of the live birds in those flocks more or less carried vancomycin-resistant enterococci. Today, we are down to just a few percent. When avoparcin [Mad Biologist: an anologue of vancomycin] use went down, another drug, virginiamycin -- which is closely related to Synercid and promotes resistance -- was used instead. Synercid resistant enterococci peaked at about the same level, but now they're coming down too, a 75-80% reduction.

Q: Industry critics claim there aren't enough data to prove a link between use of animal antibiotics and human disease -- though industry also seems to keep and control that data. What do you say to industry critics who argue that the numbers aren't there?

A:We are never willing to accept that you first have to create a lot of dead people before you intervene, in order to see if you have fewer dead people later on. From our perspective, this is first and foremost preventive action. It is not acceptable to sit and wait for the next MRSA, or any other major epidemic of a bad nosocomial clone. When we saw VRE [vancomycin resistant enterococci] starting to go around the world, and we knew we did not yet have the problem in our hospitals, we intervened by banning growth promoters -- and I would say this is actually the right time to intervene. Because once resistant organisms have established themselves in hospitals, they don't need growth promoters anymore to get established. The growth promoter sows the seeds, and doctors commit their own misuse and abuse of antibiotics, creating a really big problem.

Q: Have Denmark or the European Union -- which banned certain growth promoters even earlier -- followed up with human data?

A: Germany, the Netherlands, and Belgium have all shown reductions in the human carrier rate in the population after they stopped the use of growth promoters. It's certainly more than 50%. It has been shown beyond reasonable scientific doubt that carriage of VRE in the gut is a risk factor for VRE infection, if you go to a hospital and undergo treatment and so on. In Denmark, we have had fewer healthy people in the community who carry VRE in their guts since we stopped using growth promoters. That is my public health endpoint. If we start using a lot of vancomycin -- which we are likely to do because MRSA is suddenly on the increase in countries where it had not been very prominent in the past -- then those individuals will be at a lower risk of getting a VRE infection.

Q: How replicable is Denmark's experience, both in rich and poor nations?

A: In most nations, if we look at poultry production, the problems would probably be the same. Whether you look at rich or poor nations, intensive animal production is much more similar than is the quality of life for the populations between those nations. Animal production in Mexico or Africa or Laos adheres to the same industrial philosophy, and uses animals that are genetically similar.

In the U.S., the volume of therapeutic drugs being used alongside growth promoters is many, many times more than it is in Denmark, which does not use growth promoters. I think the U.S. is using more than sufficient quantities of therapeutic drugs to prevent the few small problems that Denmark has seen. The U.S. would probably not see any problems at all if it took out the growth promoter component -- because there are so many drugs going around already.

Q: Looking at antimicrobials and farm animals, what problems on the horizon worry you?
A: Most of the growth promoter issues here have been about gram positives: vancomycin-resistant and Synercid-resistant enterococci. What worries me are the gram negatives. E. coli and Salmonella are becoming resistant to last-generation cephalosporins and quinolones. What we are trying to put in place -- and have put in place for the fluoroquinolones -- is a policy that says that there are some therapeutic drugs that are so important for humans, where the link between use in animals and resistant infections in humans is so clear, that we are going to put additional restrictions on the therapeutic use of those drugs in animals. Vets here can only prescribe a fluoroquinolone for a farm animal where there is a documented need -- that is, if there are no alternatives, which is extremely rare. As a result, we have found a major reduction in quinolone usage and also a reduction in resistance in E. coli and Campylobacter. We are always acting early. We do not cover the well after the baby has fallen in.

Reference:
1. World Health Organization "Impacts of antimicrobial growth promoter termination in Denmark" 2002.