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News 3412 views 4 commentslast update:Jul 9, 2015

Study: Pig farmers more likely to carry MRSA

Swine farmers are more likely to carry multidrug-resistant Staphylococcus aureus (S. aureus), than people without current swine exposure. Commonly the most well-known form of this bug is methicillin-resistant Staphylococcus aureus (MRSA).

This was concluded by a team of researchers from the University of Iowa, Kent State University, and the National Cancer Institute in the US.

The study, published online in the journal Clinical Infectious Diseases, is the largest prospective examination of S. aureus infection in a group of livestock workers worldwide, and the first such study in the United States.

Drug-resistant strains

S. aureus is a type of bacteria commonly found on the skin as well as in the noses and throats of people and animals. About 30% of the US population carries these bacteria, which can cause a range of skin and soft tissue infections. Although most infections are minor, S. aureus can sometimes cause serious infections. Increasingly, drug-resistant strains of S. aureus are emerging, including methicillin-resistant (MRSA), tetracycline-resistant (TRSA), or multidrug-resistant (MDRSA) strains. And while previous studies have shown that certain strains of S. aureus are often associated with swine, cattle, and poultry exposure, little is known about livestock-associated staphylococcus carriage and infection in the United States.

S. aureus does not present an economic concern for swine farmers

The study authors note the research helps keep farmers safe by raising awareness about a potential health issue in swine operations. S. aureus does not present an economic concern for swine farmers since pigs generally are unaffected by staph infections. "S. aureus does not typically make pigs sick, but they can act as carriers and transmit the bacterium to farmers," says Tara Smith, corresponding author on the study.

"While carriage of S. aureus isn't itself harmful, individuals who harbour the bacterium in their nose, throat, or on their skin are at risk of developing an active staph infection, and they can also pass the bacterium to other family or community members. Individuals who may be immunocompromised, or have existing conditions such as diabetes, are especially at risk from staph infections."

More likely to carry MDRSA, TRSA, and livestock-associated S. aureus

For the study, the researchers followed a group of 1,342 Iowans, including individuals with livestock contact and a community-based comparison group, for 17 months. The participants were recruited from 53 of Iowa's 99 counties and lived in rural areas or small towns. Nose and throat swabs were collected from participants at the beginning of the study to determine if they carried S. aureus.

Participants who experienced skin infections during the study period also were assessed for S. aureus. Overall, 26% of the participants carried S. aureus. However, the investigators found that farmers with livestock exposure, particularly swine exposure, were more likely to carry MDRSA, TRSA, and livestock-associated S. aureus than those who weren't exposed to livestock.

Swine workers are also at risk of becoming infected

"Current swine workers were six times more likely to carry multidrug-resistant S. aureus than those study participants without current swine exposure," says Smith. The study is based on research that Smith, currently an associate professor at Kent State University, conducted while she was a faculty member at the UI College of Public Health. "Swine workers are also at risk of becoming infected with these organisms," Smith adds.

"One hundred and three potential S. aureus infections were reported, and included infections with livestock-associated strains of this bacterium." There currently is no method to prevent or eliminate carriage of S. aureus in animals or their human caretakers, meaning constant re-exposure and possibly transmission can occur between livestock and farm workers. Those workers can then pass staph to their family or community members.

"Iowa ranks third nationally in overall livestock production and first in swine production," notes Smith. "Transmission of staph between pigs and farmers and into the broader community could complicate efforts to control S. aureus transmission statewide, and have effects nationally due to the travel of pigs and people carrying these bacteria."

Source: Science Daily

4 comments

  • W J

    The conclusion of this, and the title, are improperly worded. The test group were confinement operations, CAFOs. It should read 'Conventional CAFO Swine Farmers Likely to Carry Drug Resistant Staph'. More specifically, it is those who are using low levels of antibiotics that are the problem. This is not showing up out on true pastured pig farms and organic farms. One more reason to avoid feeding low levels of anitbiotics.

  • Wm Tooley

    Help me out here.  30% of the US population carry S. Aureus.  In the study, 26% of the participants, many of them farmers or rural communities, carried S. Aureus.  How is this that more carriers than normal US populations?  I think what the study shows is that people with poor hygiene or farmers who haven't had the opportunity to shower since they left the barn are more likely to be carriers.  But the rest of the US population is even more likely to be carriers.  So you are more likely to come into contact in the airport or the grocery store, than on the farm or rural areas?  Does this appear to be simple 'headline grabbing' for some money spent on inconclusive resaarch?  Articles like this do no one good!  Please have your writers ask a few more questions before wasting readers time with sensationalistic, but inconclusive non-reseaarch findings!

  • Donald Skinner

    The title and 1st line do not say the same thing:
    'Farmers likely to carry resistant staph' and
    'farmers more likely to carry multi-drug resistant staph' are not the same thing.

    From this data we see 26% of the total study population carried resistant staph. We also know that farmers were 6 times more likely to carry multi-drug resistant staph.  It does not say what percentage of the farmer population carry single-drug resistant staph or what proportion of either the total/farmer population carry multi-drug resistant staph.  It could be 0.5% of that 26% for all we know.  

    I don't deny that this is an important issue farmers - and others - should be thinking about it, but I am tired of media outlets (Pig Progress included apparently) sensationalizing titles and leaving people with a skewed representation of the real issue.  Would it not be better to provide real information in a title rather than scaring people into clicking the link or worse, not clicking the link and just assuming that the majority of farmers carry resistant bacteria?

  • Vincent ter Beek

    Thank you very much for all your comments. I noticed what could have been done better - by accident we had forgotten to phrase the title more accurately. I have just done another round of editing and I hope it now looks better.

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