Harvesting disease

December 03, 2007

The best way to concoct a deadly microbe may not be in a secret lab but out in the open - on a farm.

Half a century after farmers began including low-level doses of antibiotics in the feed they provide to their animals in the belief that it speeds growth, drug-resistant strains of several common germs that afflict humans have blossomed. The chicken business has been the most notorious (and the big producers are taking steps to address it). But there are other suspect animals on the farm, and similar remedies are in order.

Now comes news, from a study reported in the Canadian Medical Association Journal, that a sampling of pig farms in Canada found a quarter of all swine to be infected with MRSA, or methicillin-resistant Staphylococcus aureus. This is the bug that caused such a scare this fall in the U.S., leading schools to shut down and killing students in Virginia and New York. It was associated with the hospitalization of 280,000 Americans in 2005, according to a new study published in Emerging Infectious Diseases.

The pigs may have contracted MRSA (which doesn't make them sick) from humans, but it is also entirely possible that MRSA arose among the pigs through the use of feed with antibiotics at a less than therapeutic level. Either way, though, it appears that pig farms might be a major reservoir of this dangerous illness. In this country, no one is testing them for it. Pork producers have proposed a private-industry program, but surely this is a matter for public health authorities.

And, for now at least, the widespread use of antibiotics in animal feed has to be considered suspect until proved otherwise. It's asking for trouble - and it doesn't appear to help growth the way farmers think it does.

A study this year by researchers at the Johns Hopkins Bloomberg School of Public Health found that the addition of antibiotics to chicken feed is not cost-effective. It reduces the value of a chicken, when all costs are considered, by nearly a penny, they reported.

Four of the largest chicken producers in this country, including Perdue, have moved to eliminate casual use of antibiotics. (Tyson, the No. 1 producer, is currently involved in an argument with the government over what constitutes an antibiotic.) This still leaves nearly 6 billion broilers being fed antibiotics throughout their lives, plus millions of pigs and cows - and that's too many.

A bill before Congress would phase out the use of antibiotics in animal feed over the next two years. It has widespread support from medical organizations, and for good reason: It's the right thing to do.

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