Is the way we raise our food giving us MRSA?

Dutch scientists have also traced the spread of one relatively new strain of MRSA from pig farms out into the community, specifically to a nurse who had treated one infected patient, the son of a veterinarian who worked mostly with pigs.

The newest study, the first evidence of MRSA in food animals in North America, concerns the discovery of pigs in Canada, the single largest exporter of pork to the United States and the sole country from which the U.S. imported live pigs last year. "Unfortunately there aren't good surveys for resistance in food animals in the United States," Marcus Zervos, head of infectious diseases at Detroit's Henry Ford Hospital, told Salon. "But it's thought that since the MRSA strain is in pigs in Canada, it is likely in pigs in the United States also, because there's international movement of pigs from Canada to the United States."

The study's authors surveyed 285 pigs of three different age groups from 20 pig farms in southwest Ontario. Twenty-five percent of the pigs, they found, were colonized -- that is, carrying the bacteria, but not necessarily infected by it -- with MRSA. In all, 45 percent of the farms had at least one colonized pig, and 20 percent of the farmers themselves were colonized. There was no non-pig-farmer control group in this study, but that's much higher than previously reported colonization rates for the general population, and there was a significant association between the presence of MRSA-colonized pigs on a given farm and MRSA colonization in the farmers who worked there. "The role of antibiotics in agriculture on the emergence of MRSA is completely unknown at this point. It will be hard to objectively evaluate as well," Scott Weese, one of the study's coauthors, told Salon via e-mail. "It is clear that antibiotic use is an important factor in the epidemiology of MRSA in humans and some animal species, and it is reasonable to assume the same in pigs, but we don't have enough information yet to say anything definitive."

MRSA has also been found in pigs in Denmark, the second-largest exporter of pork to the United States. And MRSA has been found not just in living animals but in small concentrations in the food chain as well: in pig meat in the Netherlands as well as in milk in South Korea, mozzarella in Italy, and chicken in Japan.

There is as yet no smoking gun to link animals to the strains implicated in the current MRSA scare, which are different from the antibiotic-resistant MRSA strains attributed to pigs so far. To be fair, any number of factors could have triggered the changes in MRSA's epidemiology, especially because MRSA (like the normal Staph aureus) is very easily spread, most often without ever making its hosts sick. Dr. Fred Angulo, chief medical epidemiologist for the Centers for Disease Control's Foodborne Disease Active Surveillance Network, says it could be that livestock are not the source of the so-called super staph. But it's also possible, he says, that they are. "It's possible that MRSA could be present in pigs and then occasionally be transmitted to humans and then occasionally get into a hospital and create these new strains." Angulo says the matter needs to be explored. The failure thus far to find a smoking gun could also simply be because there is currently so little data on the subject.

Scientists in the United States are just beginning to consider studying the relationship between MRSA and agriculture. Observers with whom Salon spoke -- even those who tend toward activism -- largely blamed this on institutional problems within the United States' food-safety structure, not on Bush administration policy. Simply put, there isn't money available to study MRSA, and if money were to be put aside for that purpose, it would have to be taken away from some other important area of interest.

"There are billions of dollars at stake here, and there's an entrenched way of growing animals that ensures that they will get sick and therefore need to be treated, so it's not at all hard to imagine why folks who want to pursue the public interest are going to run into resistance," says Margaret Mellon, a molecular biologist who specializes in agriculture issues for the Union of Concerned Scientists. "The public health infrastructure in this country, regardless of this issue, is really quite badly off ... They don't have much political clout, whereas something like the NIH, which leads directly to the production of drugs, which leads directly to billions of dollars for the private sector, could not be better funded."

Beyond a lack of resources to study the problem, there's the problem of cooperation. If you're a scientist who wants to determine whether farms in the United States could be reservoirs of MRSA, the farm has to let you collect the proof. As Peter Thorne, the director of the Environmental Health Sciences Research Center at the University of Iowa, points out, that's sometimes easier said than done. "One of the problems has been, in the U.S. anyway, that many of the studies we would like to do to look at the role of industrialized livestock production on people's health require the cooperation of the industry. And that's been a challenge for academicians," says Thorne, who has done research on MRSA in the Netherlands. "We can still go to family farms -- those that remain -- although very few now are raising livestock, because they can't compete."

The scientific method has, in effect, been turned against itself. Scientists are loath to make definitive pronouncements on anything until every possible controlled study has been conducted. In the vacuum left by that failure to truly know, scientists' hedging can be exploited by anyone with a desire to do so. In this case, both big agriculture and big pharma have a profound interest in doing just that.

"Unfortunately, it remains one of the most controversial areas in medicine," Henry Ford's Zervos says. "There are many of us who believe that the scientific evidence is very clear, that it shows the risk of giving the antibiotic to the animal, and the resulting resistance that can make its way into people ... But many people, to be completely open about it, have self-motivating interest in this. It's a big business for the pharmaceutical industry. People don't want to change. Scientists, even, don't want to influence grants that they have from pharmaceutical industry sponsors."

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