Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study suggests surface water contaminated with salmonella more common than thought

27.02.2009
A new University of Georgia study suggests that health agencies investigating Salmonella illnesses should consider untreated surface water as a possible source of contamination.

Researchers, whose results appear in the March issue of the journal Applied and Environmental Microbiology, tested water over a one-year period in rivers and streams in a region of south Georgia known for its high rate of sporadic salmonella cases. The team found Salmonella in 79 percent of water samples, with the highest concentrations and the greatest diversity of strains in the 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. “We found our highest numbers in the summer months, and this is also the time when most people get sick.”

Lipp, who co-authored the study with former UGA graduate student Bradd Haley and Dana Cole in the Georgia Division of Public Health, said that although contaminated water used to irrigate or wash produce has been linked to several well-publicized outbreaks of salmonellosis in recent years, the environmental factors that influence Salmonella levels in natural waters are not well understood. She said understanding how Salmonella levels change in response to variables such as temperature and rainfall are critical to predicting—and ultimately preventing—the waterborne transmission of the bacteria.

The team studied streams in the upper reaches of the Suwannee River Basin, which begins in south Georgia and flows into central Florida. The study area contains a mix of forested lands, row crops, pasturelands, wetlands and small cities. The researchers chose sampling sites near a variety of those environments but found little variation in Salmonella concentrations by location. The diversity of Salmonella strains, however, 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.

Salmonella can be found in the intestinal tracts of several species of animals and in humans. The bacteria are shed in feces, but Lipp said recent data suggest that they can persist and possibly grow in water if given the right conditions. Her study found that the diversity and concentration of Salmonella increased as temperatures increased. The highest concentrations and greatest diversity of strains were found in August, the warmest month of the year. Lipp adds that her study, which was funded by the National Oceanic and Atmospheric Administration Joint Program on Climate Variability and Human Health, lends support to the idea that Salmonella illnesses could increase as a result of global warming.

Lipp notes that her study area had 58 cases of Salmonella illness per 100,000 people in 2007, the last year for which figures are available, compared to a state average of 22 cases per 100,000 people and a national average of 15 cases per 100,000 people. She said the exact mechanisms by which people in her study area are being exposed to environmental Salmonella are unclear, but the most commonly detected strain in the studied streams was among the top ten associated with human infections in the health district. The porous nature of the soil in the study area means that surface water and groundwater are prone to mixing, especially after rainfalls, and Lipp said that poorly sited wells might be a factor in many illnesses. Another possibility, especially common among children, is so called incidental exposure by which people become infected with the bacteria when playing in or near contaminated waterways.

“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.”

Sam Fahmy | University of Georgia
Further information:
http://www.uga.edu

More articles from Studies and Analyses:

nachricht Innovative genetic tests for children with developmental disorders and epilepsy
11.07.2018 | Christian-Albrechts-Universität zu Kiel

nachricht Oxygen loss in the coastal Baltic Sea is “unprecedentedly severe”
05.07.2018 | European Geosciences Union

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Global study of world's beaches shows threat to protected areas

19.07.2018 | Earth Sciences

New creepy, crawly search and rescue robot developed at Ben-Gurion U

19.07.2018 | Power and Electrical Engineering

Metal too 'gummy' to cut? Draw on it with a Sharpie or glue stick, science says

19.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>