MRSA and manure
By David Manly
Oct. 8, 2013 – Living close to a farm that sprays manure may have worse implications than simply a bad smell – it could make people extremely sick, say researchers.
Scientists at Johns Hopkins University’s Bloomberg School of Public Health have found that people living near pig farms or agricultural fields have a higher likelihood of becoming infected with a deadly bacterium known as methicillin-resistant Staphylococcus aureus (also known as MRSA).
According to Joan Casey, one of the researchers who participated in the study, this study is the first of its kind to look at the risk of MRSA infection in the community due to livestock and crop operations – but previous studies have shown that a connection exists since the early 2000s. “Studies have additionally shown that about 75 per cent of the antibiotics consumed by animals ends up in their manure, [which] can contain MRSA, antibiotics and resistance genes,” said Casey. “We thought there was a possibility that high-density livestock production put people living near the operations and crop fields to which manure was applied at risk for MRSA infection.”
The researchers gathered data from hundreds of swine and dairy/veal livestock operations across Pennsylvania that spread manure on crops. They also reviewed health-care records from the Pennsylvania-based Geisinger Health System (which also helped to fund the study) and compared different groups of people: patients with MRSA (both community-associated and health-care associated MRSA), individuals with skin and soft tissue infections, and patients without an infection. Then, every patient was given an “exposure score based on the number of animals at livestock operations, on the size and amount of manure applied to crop fields, and the distance from patient’s residence to the operations or crop fields,” said Casey.
They found that people who had the highest exposure score were at an increased risk (38 per cent) of acquiring community-associated MRSA, 30 per cent more likely to get health-care associated MRSA, as well as an increased risk of skin and soft tissue infections.
“We actually found that both crop field application of manure and swine operations were associated with elevated risk,” she added.
An explanation for this trend could be due to the widespread use of antibiotics in farm animals, which could help create and spread new antibiotic-resistant bacteria and MRSA. However, more research into the disease pattern found in farms and fields, the effect from the overuse of antibiotics in farms, and the types of MRSA that are most prevalent are needed.