According to a new University of Georgia (UGA) study health agencies investigating Salmonella illnesses should consider untreated surface water as a possible source of contamination.
The study appears in journal Applied and Environmental Microbiology. For the study, researchers tested rivers and streams in a region of south Georgia over a one-year period, finding Salmonella in a surprisingly high 79 percent of water samples. Higher concentrations and greater diversity of types of salmonella were found in summer and after rainfall.
“Streams are not routinely tested for Salmonella, and our finding is an indication that many more could be contaminated than people realize,” said Erin Lipp, associate professor in the UGA College of Public Health and co-author of the study. “We found our highest numbers in the summer months, and this is also the time when most people get sick.”
The team studied a variety of environments, such as forested lands, row crops, pasturelands, wetlands and small cities. The diversity of Salmonella strains was highest near a farm containing cattle and a pivot irrigation system, suggesting that close proximity to livestock and agriculture increase the risk of contamination. The researchers also found a strong and direct correlation between rainfall for the two days preceding sample collection and the concentration of Salmonella, suggesting that runoff contributes to the contamination.
According to Lipp, the environmental factors that influence Salmonella levels in natural waters are not well understood,even though contaminated water used to irrigate or wash produce has been linked to several well-publicized outbreaks of salmonellosis.
“Understanding the environmental factors that contribute to salmonella illnesses can guide our efforts to educate people about how they can avoid being sickened through the proper construction and maintenance of wells, basic hygiene such as hand washing and good food safety practices,” Lipp said. “We also have the potential to decrease the likelihood of larger outbreaks related to produce, because in many cases contaminated irrigation water, and not the produce itself, may be the cause of the outbreak.”
Applied and Environmental Microbiology
University of Georgia