More & stronger warnings about antibiotic use by factory farmers
From ANIMAL PEOPLE, November/December 2013
BALTIMORE, BEIJING, BOSTON, SEATTLE, TORONTO––No one is trying to raise healthier crows by feeding them antibiotics, yet Tufts University researcher Julie Ellis has discovered antibiotic-resistant bacteria in crow guano in four states. “We’ve documented human-derived drug resistance where it shouldn’t be––in wildlife and the environment. But we know very little about how this may impact public health,” Ellis told Environmental Health News staff writer Lindsey Konkel. Genes for antibiotic resistance have also been found in gulls, foxes, frogs, sharks, whales, insects, and sand and coastal water samples from California and Washington, Konkel noted. “Microbes connect the planet. The danger is that we are entering a post-antibiotic era in which even our last-line drugs won’t work and routine infections can become life-threatening,” said George Washington University professor of environmental and occupational health Lance Price. Ellis revealed her findings from crow guano six weeks after a 114-page report from the Centers for Disease Control & Prevention concluded that antibiotic-resistant bacteria infect about two million Americans per year, killing at least 23,000. The report evaluated infections from 17 drug-resistant bacteria and one fungus. “Much antibiotic use in animals is unnecessary and inappropriate and makes everyone less safe,” the CDCP report said. The CDCP study appeared only days before Donald Low, M.D., 68, died of a brain tumor on September 18, 2013 in Toronto. An expert on antibiotic-resistant streptococcus bacteria, Low headed a Canadian government advisory committee that warned in August 2002 that routine use of antibiotics in animal agriculture could incubate antibiotic-resistant disease. The committee recommended that antibiotic use in livestock should be restricted to treating actual infections, and that antibiotics should not be given routinely to prevent infections that might inhibit rapid growth to slaughter weight. The committee recommendations drew worldwide news coverage, but at the political level the influence of agribusiness ensured that they went ignored.
CRE & MRSA kill
Agribusiness has continued to kill similar warnings, including on repeated occasions from CDCP director Tom Friedan, M.D., who has diplomatically avoided addressing the role of antibiotics in agriculture while warning about antibiotic resistance. Already, “Our strongest antibiotics don’t work and patients are left with potentially untreatable infections,” Friedan told a media conference on March 5, 2013. Friedan specifically cited the spread of Carbapenem-Resistant Enterobacteriaceae. Causing about 600 human deaths per year, CRE has now been identified in 4% of the hospitals in the U.S. and 18% of the hospitals providing specialty care. Of the 37 forms of CRE known when Friedan spoke, fifteen had been discovered in the preceding nine months. Congressional Representative Louise Slaughter, of Rochester, New York, on March 17, 2013 cited a different antibiotic-resistant bacterium in appealing to U.S. Food & Drug Administration commissioner Margaret Hamburg to unilaterally use her authority to restrict the use of antibiotics in livestock. Slaughter, the only microbiologist in Congress, called to Hamburg’s attention a study published in the journal EMBO Molecular Medicine whose authors used genetic markers to identify the passage of methicillin-resistant Staphylococcus aureus, called MRSA, from livestock to humans. “Currently, MRSA kills more Americans each year than HIV/AIDS,” said Slaughter. “The extreme overuse of antibiotics in livestock is endangering human health. Eighty percent of all antibiotics sold in the U.S. are sold for agricultural use. Most often, these antibiotics are distributed at sub-therapeutic levels to healthy animals as a way to compensate for crowded and unsanitary living conditions or to promote growth. Any effort to stop the growth of antibiotic-resistant bacteria must address the overuse of antibiotics in food-animals.” Earlier, Slaughter introduced into Congress a proposed “Preservation of Antibiotics for Medical Treatment Act.” Though endorsed by the World Health Organization, American Medical Association, National Academy of Sciences, and more than 450 other organizations, the bill failed to advance even to a committee hearing. British researchers in December 2012 reported finding MRSA in bulk milk tanks from five widely separated dairy farms, indicating that the antibiotic resistant bacteria may be ubiquitous among the British milking herd. “Although pasteurisation of milk should ensure that MRSA will not enter the food chain, our finding of MRSA in dairy cattle has clear public health implications,” they summarized in Center for Infectious Disease Research & Policy News. “Workers on dairy farms, or individuals with regular contact with dairy cows, are likely to have a higher risk of colonization or infection.” A study by Johns Hopkins Bloomberg School of Public Health researchers published on September 16, 2013 reinforced the British findings. Approximately 11% of MRSA infections, the Johns Hopkins researchers found, could be attributed to exposure crop fields fertilized with pig manure. The study appeared in the Journal of the American Medical Association online periodical JAVA Internal Medicine.
The science, simplified
University of Washington microbiologist and immunologist Marilyn C. Roberts outlined the science of the problem as a guest columnist for the Seattle Times. “Worldwide, the livestock industry consumes approximately twice the amount of antibiotics as are prescribed for humans, usually administered in food and water to the entire herd or flock,” Roberts explained. “This practice employs smaller concentrations of antibiotics than are typically used to treat bacterial infections. Low concentrations of antibiotics, whether in animals or people, kill the susceptible bacteria, but select for bacteria that survive because of genetic changes. This leads to the selection of antibiotic-resistant and multidrug-resistant bacteria, also known as superbugs. “The FDA began to limit the use of penicillin and tetracycline in animal feed as growth promoters 35 years ago,” Roberts continued, “but the U.S. House and Senate budget committees passed resolutions against the ban.” By contrast, Roberts wrote, “Europe banned antibiotics as growth promoters in 2006. In Denmark, antibiotic usage dropped 50 to 60% in livestock production. Denmark also prohibits veterinarians from profiting from the sale of antibiotics to farmers, which is a practice that continues in the United States. The Danes found no negative impact on production or feed quantities used. Danish pork production has increased.”
National Public Radio reporter Dan Charles explored how that happened on February 11, 2013. Antibiotics “used to deliver a boost in growth, but that effect has disappeared in recent years or declined greatly,” Charles began. “Researchers think the antibiotics used to work by suppressing low-grade infections. In recent years, however, pork producers have found ways to accomplish the same thing through improved hygiene. This has occurred even while swine operations grow. As a result, the drugs have become largely superfluous––yet many farmers still use them.” Sixty years ago, explained Kansas State University swine nutrition specialist Steve Dritz, administering prophylactic antibiotics was found to accelerate the growth rates of pigs, poultry, and cattle by up to 15%. Beginning about 20 years ago, however, factory farming began transitioning to an approach called multisite production. “Previously, pigs were born and raised in one barn or in several barns close together,” Charles summarized. “Infections could easily pass from one generation to the next. Under the new system, when piglets are weaned, they move to a whole different place. That new site is carefully scrubbed and free of disease.” Each group of pigs remains together from weaning to slaughter, and is kept isolated from all other pigs. Workers moving from one barn to another must change their boots and clothing. Dritz did research establishing that multisite production keeps pigs as healthy and promotes rapid growth as effectively as antibiotic use, but found, Charles reported, that U.S. farmers and agricultural veterinarians are reluctant to quit dosing livestock with antibiotics. Partly this is from fear of losing a perceived competitive edge, and partly, Dritz suggested, just from reluctance to change an established method. ––Merritt Clifton