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Environmental Health

MRSA Infection Found in Communities Near Pig Farms

Evidence of links between large-scale animal-rearing practices and human health in neighboring communities continues to accumulate.

By Stephanie Soucheray

On Oct. 18 and 19, the North Carolina Environmental Justice Network will hold its 15th annual meeting in Whitakers to discuss unsafe agricultural practices in poor, rural and black communities across the state.

Magnified view of methlycillin-resistant Staphlycoccus aureus. Image courtesy the Centers for Disease Control and Prevention.

Magnified view of methlycillin-resistant Staphlycoccus aureus (MRSA). Image courtesy the Centers for Disease Control and Prevention.

While the NCEJN has been concerned with issues such as dumping, factory farms and clean water, Executive Director Gary Grant said that this year they’ll also be discussing agricultural illness in front of a government listening panel.

There’s good reason for concern.

Last month, UNC researchers published in the online journal PLoS One the results of a study, “Livestock-Associated Methicillin and Multidrug Resistant Staphylococcus aureus Is Present among Industrial, Not Antibiotic-Free Livestock Operation Workers in North Carolina.”

They found that factory-farm workers were much more likely to have colonized MRSA (present in nasal swabs) than workers who worked on antibiotic-free farms.

Now a new study from John Hopkins University further describes the connection between factory farms and MRSA.

The study, “High-density livestock operations, crop field application of manure, and the risk of community-associated methicillin-resistant Staphylococcus aureus infection in Pennsylvania,” published this week in JAMA Internal Medicine, shows that there is an “environmental pathway” that MRSA follows in communities near high-density swine-production facilities.

hog spraying field

Aerial photo of a field near a hog CAFO on which animal waste is being sprayed, Duplin and Jones county, 2003. Photo courtesy Socially Responsible Agricultural Project, flickr creative commons

“We found that in a general population in Pennsylvania, people with a higher exposure to high-density swine production were at an increased risk of community-associated MRSA infection and skin and soft-tissue infection,” said Joan Casey, a lead author of the study. “This risk was about both the livestock operations where the animals live and about the crop fields where manure was spread.”

The John Hopkins study is the first to link factory farming to MRSA infection, not just colonization, and Casey said the UNC and JHU studies both suggest that these types of farming practices are bad for public health.

“While we did not demonstrate every step in the causal chain from farm to infection, we do believe that the association is plausible,” said Casey. “There is certainly an environmental pathway.”

Like the UNC study, the JHU study implicates the overuse of antibiotics in industrial-farmed animals as being a risk factor for MRSA. Animals are given what’s known as “sub-therapeutic” amounts of antibiotics in their feed and water supply to stave off illness, rather than to treat an acute infection. The majority of the antibiotics given to animals in these situations are not absorbed, and instead are passed through to the animal’s manure.

That manure is applied to crop fields, and neighboring residential communities, according to Casey, are at a greater risk for community-associated MRSA, health care-associated MRSA and skin and soft-tissue infections.

Casey’s study looked at 1,539 patients with community-associated MRSA, 1,335 with health care-associated MRSA, 2,895 with skin and soft-tissue infections and 2,914 healthy controls patients in a Pennsylvania health care system between 2005 and 2010.

Higher swine manure exposure meant an increased likelihood of all MRSA infections, and even just living near a high-density swine livestock operation resulted in an increased risk for community-associated MRSA.

Steve Wing, who co-authored UNC’s study, said JHU’s study further illustrated the problem with giving farm animals antibiotics.

“This is an important finding about a problem, the sub-therapeutic use of antibiotics, that’s been recognized a long time,” he said.

Gary Grant

Gary Grant of the Tillery (N.C.) People’s Clinic and the North Carolina Environmental Justice Network at a community forum in 2006. Photo courtesy of NIEHS

Wing said that the findings in the study should be a concern to people in North Carolina who live near high-density farms.

“Eastern North Carolina has the densest livestock production, but it’s also one of the poorest areas in the state,” he said.

Unlike in the JHU study, which benefited from combing a large insurance database for information on MRSA infection, many people in the Eastern part of the state are uninsured, so Wing said it would be difficult to obtain accurate information about MRSA infection rates.

He also said that while research like this is important, it often does little to change policy. The sub-therapeutic use of antibiotics has been banned in Europe for years, but a bill that would do the same in the States has failed to get passed in Congress.

“It takes a lot more involvement by the public to change policy,” said Wing. “The public is who’s affected by this.”

Grant said he’s been concerned about farming practices and community health since the early 1990s.

“In the beginning, many of these communities [where large farms are located] depended on well water, so runoff was a huge concern,” Grant said.

He said that 20 years ago, it was legal for counties to pass individual ordinances on farming practices, but the most recent General Assembly passed legislation that makes it easier for the state to override them.

Though Grant doesn’t have hard data on MRSA in North Carolina, he said sick communities do exist in rural pockets of the state.

“We are aware of it, and still trying to help communities get organized around the issue,” he said.

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