May 2016
A monthly series reporting to the produce industry on CPS research projects


University of Arizona researchers team on ways to improve water quality assessments

A pair of University of Arizona researchers who have been co-investigators on each others' projects in the past have teamed up once again on two Center for Produce Safety-funded efforts.

Dr. Kelly Bright, an associate research professor with the College of Agriculture and Life Sciences, is leading the project titled "Enteric viruses as new indicators of human and cattle fecal contamination of irrigation waters." Dr. Marc Verhougstraete, an assistant professor in the College of Public Health, is co-investigator.

Verhougstraete is leading the project titled "Optimal strategies for monitoring irrigation water quality and the development of guidelines for the irrigation of food crops." And Bright is co-investigator.

"Marc and I work really well together," she said of their collaborations.

Key Take-Aways
  • Specific viruses may be more accurate indicators of fecal contamination of irrigation water than E. coli.
  • Because viruses are host-specific, they also can provide clues about the contamination source.
  • A user-friendly bilingual pamphlet that highlights five key water monitoring strategies is nearing publication.
  • Intended for the Southwest, the strategies are based on earlier work that analyzed more than 1,300 water samples.
Bright is building on earlier CPS-funded research led by Dr. Channah Rock, a University of Arizona water quality specialist, that examined three commonly used detection methods for assessing E. coli contamination of irrigation water.

"We found all three had high false-positive and high false-negative results, which obviously is troublesome. So there is a need for a much more accurate method," Bright said.

She said the current E. coli assessment methods were developed for use in drinking water systems and may not be appropriate for irrigation water from surface supplies.

Instead, Bright is examining whether the presence of specific viruses may give a more accurate picture of fecal contamination, which could improve our understanding of produce contamination.

Testing methods that use polymerase chain reaction, or PCR, can help researchers identify the types of viruses as well as the quantity of virus particles in a known measure of water.

Viruses are usually host-specific, so cattle viruses typically infect cattle, and human viruses infect humans. Viruses also cannot reproduce without a host.

This knowledge comes in handy when seeking a contamination source, Bright said. "When you find cattle viruses in water, you can reasonably assume that the contamination came from cattle feces," she said.

Should Bright find certain viruses are better indicators of fecal contamination, then commercial laboratories that already test water samples for growers could offer the new PCR tests, as long as the procedures were standardized.

"It's something that I think some growers could do, and it's definitely something that commercial labs could do," she said.

Collaborating with her are Dr. Lisa Casanova, an assistant professor in the School of Public Health, Georgia State University, and Dr. Laura Suppes, an assistant professor with the Environmental Health Program, University of Wisconsin, Eau-Claire. The two are collecting water samples in their respective states and sending Bright virus-laden water filters for analysis.

"We want to assess water of different quality from different parts of the U.S. because, obviously, the water and conditions in Georgia are not going to be the same as in the Southwest," she said. "We're trying to have at least representative samples from those areas so we can see if there are differences in the environment and how those conditions might affect which viruses we find and also their numbers."

Dr. Brandon Iker, a former University of Arizona post-doctoral researcher who now works in private industry, will assist with final data analysis, Bright said.

A bilingual, user-friendly pamphlet

Verhougstraete is finishing work on a bilingual pamphlet that outlines five key water sampling strategies for producers in the Southwest. The guidelines are designed to aid in reducing the risks of produce contamination from contaminated surface irrigation water.

Once completed, the straightforward brochure can be distributed to growers and their employees.
The strategies are based on earlier CPS-funded work that involved collecting and analyzing more than 1,300 water samples from irrigation canals within the Yuma Irrigation Water District for total coliforms, E. coli, pH, turbidity, temperature, conductivity and salinity.

"We looked at all of the different environmental parameters that were impacting water quality in the Southwest," he said. "The weather in the Southwest is predominately very sunny and dry, so I'm not comfortable that our samples are representative of, say, the Midwest."

Verhougstraete already has finished a draft pamphlet in English, but he said the challenge is having it accurately translated into Spanish so it can reach the broadest audience possible.

Bright is one year into her two-year project and plans to present a background on the research and describe her work to date at the CPS Research Symposium, June 28-29, in Seattle.

Verhougstraete, on the other hand, recently completed his one-year project. At the Symposium, he plans to share his research results and how they were incorporated into the user-friendly pamphlet designed for the produce industry.

CPS Research Symposium
About CPS
The Center for Produce Safety (CPS) is focused exclusively on providing the produce industry and government with open access to the actionable information needed to continually enhance the safety of produce.  Established by public and private partnership at the University of California, Davis, initial funding for CPS was provided by the California Department of Food and Agriculture, the University of California, Produce Marketing Association and Taylor Farms.  Ongoing administrative costs are covered by the Produce Marketing Association, enabling industry and public funds to go exclusively to research. 

Enhancing produce safety through  research, outreach and education
For more information:
Center for Produce Safety
Phone:  530-554-9706

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