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VA/HSR&D Researchers Suggest Veterans Living near Pig Confinement Operations are More Susceptible to MRSA

January 30, 2014

Methicillin-resistant Staphylococcus Aureus (MRSA) bacteria can cause antibiotic-resistant infections. In 2006, VA implemented a set of procedures, including mandatory hospital admission screening to see if Veterans are carrying MRSA and, thus, would pose a risk to other patients. This study examined whether Veterans living near concentrated animal (pig) feeding operations (CAFOs) were at increased risk of screening positive for MRSA at the time of hospital admission. There are typically 19 million pigs being raised in Iowa, primarily housed in 7,000 CAFOs. Therefore, investigators identified 1,036 Veterans who were admitted to the Iowa City VA Healthcare System between 12/09 and 12/11. In addition to age and gender, patients' addresses were recorded, as well as exposure to pig CAFOs.

Results showed that 119 (6.8%) Veterans screened positive for MRSA at hospital admission, and the risk of MRSA nearly tripled for Veterans who lived within one mile of large pig CAFOs that housed more than 2,500 mature pigs or greater numbers of immature pigs. Although the exact mechanism by which residential proximity increased the risk of MRSA is unknown, findings suggest that there is potential for drug-resistant strains of S. aureus in animals to transmit to people living at close distances. However, this study did have several limitations; for example, investigators did not test the bacteria to see whether it was a strain commonly found in pig confinements or whether it might have come from other sources in the community. Also, they were unable to control for livestock contact with Veterans or people living in their households.

Findings from this study gained national attention in Wired Magazine and were recently highlighted in the Des Moines Register .


Carrel M, Schweizer M, Vaughn-Sarrazin M, Smith T, and Perencevich E. Residential proximity to large numbers of swine in feeding operations is associated with increased risk of methicillin-resistant Staphylococcus Aureus colonization at time of hospital admission in rural Iowa Veterans . Infection Control and Hospital Epidemiology February 2014;35(4):190-192.