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Antibiotic use in livestock contributes to MRSA’s menace February 22, 2010

Posted by Gretchen Giannelli in Environmental Health, Global Health, Occupational Health, Prevention.

Recently, CBS’s Katie Couric highlighted a public health problem that keeps resurfacing —the use of antibiotics in livestock to promote growth and the link to antimicrobial resistance in humans.  The well-documented two-part story focused in part on farmers who have contracted life threatening infections such as MRSA (methicillin resistant staphylococcus aureus) by working with chickens and pigs  dosed with antibiotics which have, in turn, become breeding grounds for super drug resistant bacteria.

MRSA is one of the most common types of antimicrobial resistant bacterial infections, but there are many others such as E Coli, Salmonella and Campylobacter, which are monitored by Centers for Disease Control and Prevention (CDC). These bacterial diseases can be transmitted from animals to humans by different types of exposures including physical contact, and in air, water, and food and are called zoonotic diseases. The report did not discuss the most common ways humans acquire MRSA, such as in hospital settings, or that a new type of MRSA called C-MRSA is increasingly being found in community settings such as athletic facilities.

According to the CBS report:

Drug resistant infections have sky-rocketed over the past two decades, killing an estimated 70,000 Americans last year alone. It’s an emerging health crisis that scientists say is caused not only by the overuse of antibiotics in humans, but in livestock as well.

Couric found one farming community in Arkansas where 37 poultry workers who contracted MRSA multiple times had filed a lawsuit.  She also interviewed farmers who defend the widespread practice of using antibiotics in livestock saying that people want cheap meat and that antibiotic use makes this possible by preventing disease and making the animals grow larger, faster. The veterinarian for the National Pork Board defended the practice as safe and said animals would get sick otherwise. However, FDA’s Joshua Sharfstein claimed that “antibiotic use on farms does pose a risk to humans”.

Couric also interviewed farmers who gave up antibiotic use many years ago and report that their animals remain healthy since they are well treated and well nourished and that costs have increased minimally to about 5 cents more per pound. Farmers say just keeping livestock healthy eliminates the need for growth promoters.  Applegate Farms, one of the interviewees, has excellent antibiotic free meats at Trader Joes.

It was appropriate for Couric to provide some comparison to Europe in her report since they banned all non medical use of antibiotics in livestock in 2006. In part two, dubbed “The Danish Experiment,”  Couric reports from a Danish farm in which farmers explain that no antibiotics are used in their pig feed as it is not needed to keep them healthy. A dozen years ago European reports began showing evidence that antibiotic use was contributing to antibiotic resistance in humans . The Danes were the first in Europe to ban the use of antibiotics and saw a drop in antibiotic resistance. Their pigs are given space to grow, which acts as a natural growth promoter, and not using antibiotics has increased the cost of meat  by only pennies on the pound.  These results led to the final ban for all of Europe in 2006.

When I visited the website for the European Antimicrobial Surveillance System called EARSS I read in a 2008 pdf that labs reporting to EARSS had decreasing numbers of MRSA isolates. The document reads ” This is the first time that EARSS is able to report an improvement for MRSA in Europe….”  Could this drop be as a result of the 2006 ban on antibiotics as growth promoters in livestock? Might this indicate that if the US followed in Europe’s footsteps and imposed a ban we could see fairly immediate drops in MRSA incidence?

Surveillance on antibiotic use in animals and humans, as well as disease reporting of antimicrobial disease outbreaks  must be improved, something Joshua Sharfstein mentioned in the interview with Couric, and where she might  have delved deeper . Most people are unaware that we have no real numbers on the amounts of antibiotics that are used in livestock since these are kept under wrap by both the agricultural and pharmaceutical industries.  We don’t know how much is dosed in food or water and we also don’t have adequate measures of how much the animals metabolize and release into water on feedlots, which has implications for waterborne exposure to humans. Researchers have estimated 70% of all antibiotics are used in farm animals, but until we have the numbers we cannot accurately assess risk.

The report barely touched on legislative efforts, but did offer a link on the CBS website to pending legislation called the “Preservation of Antibiotics for Medical Treatment Act” (PAMTA) sponsored by Congresswoman Louise Slaughter (NY).  There was no mention of the long history of multiple stakeholder support for a ban and multiple legislative attempts which have languished. Groups such as The American Medical Association,  The American Academy of Pediatrics, and The Infectious Diseases Society of America all support a ban.

The FDA has stated it supports restricted use of antibiotics in livestock, and has already demonstrated that it follows an evidence based approach with regard to antibiotic use in animals  contributing to increased disease risk in humans.  In 2000 the agency indicated that it was revoking the use of fluoroquinolone in chickens due to increasing rates of antibiotic resistant campylobacter infections in humans, but it took five years to get pushed through Congress due to challenges from the industries. The fluoroquinolone battle underscores the powerful influence of the agricultural and pharmaceutical industries and indicates this war on drugs may not be so easily won.



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