Environmental factors impacting the risk of produce becoming contaminated in the Yuma growing region of Arizona are the subject of a new study.
University of Arizona (UA) Cooperative Extension scientists are partnering with the U.S. Food and Drug Administration, Yuma growers, local irrigation districts, and the Arizona Department of Agriculture on a multi-year study of growing practices and the environment in the Yuma produce growing region.
The study follows the deadly 2018 E. coli O157: H7 outbreak linked to romaine lettuce grown in the region.
The outbreak sickened at least 210 people and killed five. The romaine lettuce was the source of the largest outbreak of E. coli O157: H7 seen in the United States in 10 years. It included reports from 36 states.
Inquiries into just how the romaine became contaminated with bacteria usually associated with bovine intestines have been underway since the outbreak.
FDA investigators found irrigation water samples from a canal in the Wellton district that tested positive for the same genetic strain of E. coli that infected the outbreak patients.
One mile upstream from the tainted canal is the Five Rivers Feedlot, with a capacity of 120,000 cattle. FDA’s traceback investigation found 36 growing areas on 23 farms that were potential sources of the contaminated romaine during the outbreak.
The new study, announced by UA Cooperative Extension, “comes in order to provide recommendations toward enhanced food safety after the 2018 outbreak of E. coliO157: H7 linked to romaine lettuce grown in the (Yuma) area.”
The previous environmental assessment, conducted from June through August 2018 by FDA and other state partners, narrowed the scope of the outbreak. However, according to UA Cooperative Extension Service, the specific origin, environmental distribution, and potential reservoirs of the outbreak remain unknown.
As part of the new study, UA researchers will work with the FDA, the Arizona Leafy Green Marketing Agreement participants, and the Wellton Mohawk Irrigation and Drainage District to:
- Assess potential sources of microbial contamination in the growing region; and
- Examine the prevalence and persistence of pathogens in the ecosystem and effect that temporal fluctuations from season to season might have on the microorganisms of public health significance that they may be in or near the growing environment.
The researchers will use critical findings to provide recommendations to Yuma growers on best management practices to enhance food safety in the region.
UA’s extension assistants, students and staff will be collecting and examining samples from the environment such as surface water, canal sediment, and dust, according to Channah Rock, UA professor and extension specialist.
“The team will also be collecting scat samples to assess the impact that animal intrusion and native wildlife in the area may have on the growing environment,” Rock said.
Collaborators say the findings from the study will contribute new information on how various environmental influences on bacterial persistence and distribution in the Yuma agricultural region impact the risk of produce becoming contaminated, leading to improved growing and harvesting practices to prevent or mitigate those risks, and ultimately enhancing the safety of produce grown in the region.
“While production of safe food is paramount to growers of leafy greens, outbreaks still occur,” Rock said. “Because of the commitment of local Yuma produce industry to food safety, we’re able to work side-by-side to find solutions, enhance food safety, and ultimately protect public health.”
The Yuma growing region is part of the Arizona/California area known for producing $4 billion of leafy greens annually, or about 90 percent of the country’s leafy greens. The Wellton-Mohawk Irrigation and Drainage District runs along the Gila River, eventually making it to the Imperial Dam. The Mohawk Main Canal is 48 miles long while the Wellton Canal is 20 miles long.
The district pours 230,000 acre-feet of irrigation water on a variety of crops, turning the desert green.
Growers are participants in the Leafy Green Marketing Agreement that since the outbreak has imposed larger buffers between crops and feedlots. The buffers were expanded to 1,200 feet, up from 400 feet before the outbreak. Some growers are opting for larger buffers.
Water from a 3.5-mile segment of the Wellton canal was contaminated with the outbreak strain of E. coli O157: H7, according to the earlier study by FDA and the federal Centers for Disease Control and Prevention.
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