BALTIMORE, Md. – People who live near livestock or livestock operations may have an increased risk of acquiring Methicillin-resistant Staphylococcus Aureus (MRSA), according to a new study. The findings were published in the November issue of Emerging Infectious Diseases.
In the study, researchers compared livestock density, place of residence and existing information on risk factors. Analysis of the data found that regional density of livestock is a risk factor for nasal carriage of livestock-associated MRSA for persons with and without direct contact with livestock. Leading the study was an international team of researchers from the Johns Hopkins Bloomberg School of Public Health, the Dutch Institute for Public Health and the Environment (RIVM) and VU Univ. Medical Center in Amsterdam, the Netherlands.
“In the Netherlands LA-MRSA was first found in 2003 and was initially almost exclusively found in persons with direct contact to livestock," said Jan Kluytmans, MD, Ph.D., co-author of the study. "In recent years LA-MRSA is found with increasing frequency in community-dwelling individuals with no known contact with livestock. It is important to determine the routes of transmission outside of the farms since this may have important consequences for public health.”
Researchers found that as the density of veal calves, pigs, or cattle doubles in a specific area, the odds of carrying livestock associated MRSA (LA-MRSA) increases between 24 percent and 77 percent, depending on the animal.
"These results challenge us to understand how these exposures could be occurring,” said Beth Feingold, Ph.D., MPH, MESc, lead author of the study. “This work has potential policy implications for MRSA surveillance in countries with a substantial percentage of total MRSA cases being livestock-associated MRSA.
"Controlling the spread of livestock-associated MRSA requires attention to community members in animal-dense regions who are otherwise unaffiliated with livestock farming,” she added.
They study's authors believe their findings may have implications for Americans because of the volume of pig farms in the US.
“Swine production is a significant industry in the Netherlands, but its density and scale are much less than in the United States," said Ellen Silbergeld, a study co-author. "Future work should investigate the relationship between intensive livestock operations in the US and exposures to drug-resistant microbes including MRSA.”
Staphylococcus aureus can cause illnesses in humans that range from minor to life-threatening infections of the skin, bloodstream, and respiratory, urinary and surgical sites, according to the Centers for Disease Control in Atlanta.
MRSA is resistant to penicillin and certain other first-line antibiotics, and it is commonly a skin infection, according to CDC. Nasal carriage of MRSA staph bacteria is associated with increased risk of eventual infection, although it is not an indication of actual infection.