“Guarded optimism.” That’s the way Elston Grubaugh, general manager of the Wellton-Mohawk Irrigation and Drainage District in the eastern Yuma, AZ, growing area describes his thoughts about the current romaine lettuce season.
In 2018, an outbreak of E. coli O157:H7 infections linked to romaine lettuce grown in the Yuma area sickened 210 people and killed five. Reported in 36 states, it was the largest outbreak of E. coli O157: H7 the United States had seen in 10 years.
In their search of the source of the problem, U.S. Food and Drug Administration investigators found some water samples from an irrigation water canal in the Wellton district tested positive for the same genetic strain of E. coli that infected the people sickened or killed in the outbreak.
E. coli is the shortened name of a bacteria called Escherichia coli that is found in the environment and intestines of people and animals. In people, some strains of it can cause infections, pneumonia, and kidney failure. Some strains of E. coli aren’t dangerous to people, but others such as E. coli O157: H7 can cause fatal infections.
Ideal growing conditions
Because the Yuma growing area is blessed with a mixture of day-after-day of sunshine and Colorado River irrigation water, it is an agricultural powerhouse. In combination with Southern California, it is often referred to as the nation’s “salad bowl.” The overall area represents a $4 billion industry and provides 90 percent of the U.S. grown leafy greens distributed in the United States every year.
In a typical year, about half of the acreage in the Yuma area is used for romaine lettuce.
The Wellton-Mohawk Irrigation and Drainage District lies 45 miles along the Gila River, but the district receives water from the Colorado River at Imperial Dam. The Mohawk Main Canal is 48 miles long and the Wellton Canal is 20 miles long. The area around Yuma is dry, desert land that receives very little rain. But thanks to irrigation, roughly 230,000 acres are used to grow a variety of crops, turning the desert into a vibrant green landscape in winter.
For anyone who lives in growing areas other than the desert, the sight of the crops growing right next to the desert sand, all under a canopy of sunny blue skies, is breathtaking. The Colorado River water in the area’s irrigation canals is also beautiful — it does not look turgid — and is sometimes adorned with colorful wildflowers on its banks.
“Shock, yes it came as a shock,” said Grubaugh, referring to the 2018 outbreak. “Quite a shock. We have not had a major outbreak since the district was formed in 1951.”
The spring 2018 outbreak associated with romaine lettuce from the Yuma area effectively shut down the industry as consumers and commercial buyers, including restaurants and grocery stores, stopped buying all romaine.
It didn’t help that when the Yuma area’s growing season was done, another E. coli outbreak hit. It was traced to romaine lettuce from a farm in California. At that point, the U.S. Centers for Disease Control and Prevention went so far as to warn people not to eat any romaine at all. On top of that, the FDA called on the industry to voluntarily withdraw all romaine from the market and temporarily cease shipping.
So far so good
So far so good this year in the Yuma growing area, said Grubaugh. No reports of E. coli infections have surfaced. Yet, he also points out it was about this time in 2018 when the reports of lab-confirmed E. coli infections started.
“Like everyone else, we are hoping we won’t have a repeat this year,” he said.
He’s basing his “guarded optimism” on some changes the district and the growers have made this year.
Organizations in Arizona and California referred to as Leafy Greens Marketing Agreements, have set out requirements for their members who grow romaine and other greens.
To maintain membership, growers must use buffer zones between produce fields and animal feedlots, also referred to as concentrated animal feeding operations (CAFOs). Those buffer zones have been expanded from 400 feet to 1,200 feet. Food-safety specialist Vicki Scott of the Yuma Safe Produce Council said some growers are opting for distances greater than that. Grubaugh said he has heard that some buyers are requiring that the leafy greens fields be a full mile away from feedlots.
This change in distance was triggered by an environmental assessment of the area done by FDA and CDC, among others, that found samples of water collected in a 3.5 mile stretch of the Wellton canal contained the same E. coli O157:H7 strain that sickened outbreak victims.
The locations of where the E. coli was detected were approximately one mile upstream of the Five Rivers feedlot — which has a capacity of 120,000 cows — adjacent to it and approximately one mile downstream from it.
The FDA’s traceback investigation identified 36 growing areas on 23 farms as potential sources of the contaminated romaine consumed during the outbreak.
In 2018, investigators collected six samples from the Wellton-area feedlot — composted manure, dry manure, fresh manure, spilled fresh manure, well water, and feedlot drainage water from a retention pond. The outbreak strain was not detected in any of them.
But the report concedes the sampling was limited, especially considering how large the feedlot is, and that it has a high turnover of steers. It also points out that the limited sampling was performed after the outbreak had occurred. The first confirmed outbreak patient became sick on March 13, 2018, but the samples were not collected until early June 2018.
E. coli O157:H7 can come and go in cattle herds. And, as the report points out, “it is not possible to draw statistically valid conclusions . . . based on the number of samples collected and when they were collected relative to the outbreak.”
The investigators also failed to detect any signs of E. coli in the farm fields near the feedlot. However, they took the samples in June, well after the outbreak and more than two months after harvest around Yuma had ended. After harvest, growers routinely plow up the fields in preparation for the next crop, exposing the soil to sun, dry air, and heat that quickly kill E. coli bacteria.
According to the environmental assessment report, because the Yuma region’s growing season had already ended weeks before the assessment began, there were no leafy greens available for testing by the outbreak investigation team.
Grubaugh said one of FDA’s theories is that shallow groundwater from the feedlot was contaminated. “As we pumped the groundwater, did it somehow contaminate the irrigation canal?” he said.
However, samples collected from the feedlot’s wells and from adjacent district drainage wells didn’t show E. coli.
Grubaugh also said canal repairs after the outbreak investigation may have been a step toward one solution. The district hopes to draw down the canal again this year for additional concrete repair work.
“We would like to take the canal out of service for a few days to see if it makes any difference, he said.
In August 2018, investigators with the environmental assessment team returned to the Yuma growing area and took additional ground water and irrigation canal water samples. The sampling sites included the three Wellton irrigation canal sites that tested positive in June. None of the samples collected in August were positive for the outbreak pathogen.
What about wildlife?
Wild animals can contaminate growing fields with E. coli from their fecal droppings. That’s why farmworkers and farm managers are trained to be on the alert for signs of wildlife intrusion.
In the case of the fields next to the irrigation canals, that can be a problem, especially since the irrigation canals are not covered and because most farm fields are not fenced to keep out deer and other four-legged animals.
“We don’t hide the fact that the open channel canals are exposed to Mother Nature,” Grubaugh said. “There’s no secret that we have wildlife here. But we take whatever steps we can.”
As for the Pacific Flyway, which is a migratory route for more than 1 billion birds annually, there’s not much any irrigation district with open canals can do.
“We can’t stop the birds,” he said.
Then there are the deer, which for the most part live in the desert immediately around the fresh produce fields and generally would prefer to stay there rather than to venture into the open fields. But that isn’t the case during a dry year. The lush fields and irrigation water lure them in. The district has put up some fencing to try to keep them out, and the Game and Fish Department has put water stations in the desert for the deer. Many of the growers have also put up fencing around their fields.
Fortunately, this growing season has been a wet one, said Grubaugh, which is good because the deer prefer to stay in their natural territory.
Humans, weather and water
One of the problems the district runs into is typical for rural areas in any part of the country.
“We have people dumping trash along the canals,” Grubaugh said, pointing out that the district’s “ditch riders” immediately report circumstances like that when they see them and the trash is removed.
During this past year’s growing season, freezing temperatures in February, followed by strong winds, damaged some of the Yuma-area romaine, tearing some of the leaves. Torn leaves emit nutrients that E. coli migrates toward — if there are any E. coli on the plants. From there, the bacteria can make their way into the leaves.
The water district operates two canal systems: an irrigation water canal system that delivers Colorado River water from Imperial Dam to Wellton-area farms and a saltwater canal system used to discharge saline groundwater from the Wellton valley to the Cienega de Santa Clara through the Main Outlet Drain.
During the outbreak investigation, the environmental assessment team discovered shallow groundwater can be diverted into the district’s irrigation canals at two locations.
The outbreak strain was detected in a district irrigation canal sample that was collected immediately downstream from one of these shallow groundwater discharges into the Wellton irrigation canal.
“We’re an old-style district,” Grubaugh said. “We still have ditch riders who patrol the canals. Their job is to report anything they see that might be a problem.”
Like the rest of the district’s employees, the ditch riders go through intensive food safety training.
“If anyone sees something that shouldn’t be there, they report it,” Grubaugh said.
Those in the produce industry continue to hope the steps leafy greens growers are taking will prevent another outbreak. However, Grubaugh said it’s not been a real strong romaine market this year.
“Our overall acreage is down,” he said.
And while Grubaugh says the district has good communication with the feedlot, some growers have said they’d like to have better communication with it.
The feedlot owners did not respond to questions from Food Safety News.
Meanwhile, the FDA investigators have returned to the Yuma area to test harvested produce at processing and cooling operations.
The Arizona and California Leafy Greens Marketing Agreements, the Produce Marketing Association, the United Fresh Produce Association, Western Growers and other business groups in the produce industry have teamed up to form a Leafy Greens Food Safety, Task Force.
According to a news release from the task force, its goal is “to sharpen our food safety systems through the entire supply chain . . . and to prevent such a tragedy from occurring in the future.” Some of that involved having growers use technological ways to track where their lettuce is harvested and shipped so that traceback of where it came from and went to can happen more quickly. That way outbreak investigators can get relevant information sooner.
California and Arizona produce more than 50 billion servings of leafy greens every year for consumption in the United States.
Why so long?
Grubaugh said that while the outbreak shocked him, what also shocked him was to read about how the district figured in the outbreak in the newspapers.
“We were disappointed that the CDC and FDA weren’t more forthcoming,” he said. “We didn’t learn about it until we read it in the paper.
“One of our criticisms is the amount of time it took them to get here and to react. Certainly, the district was disappointed that it didn’t know what was going on. Here’s something that shuts down the market, and there’s no attempt to differentiate where the lettuce came from.”
The mystery remains
When all is said and done, Grubaugh said “even now, no one knows the source of the outbreak.” He’s not alone in that assessment.
“The outstanding question is, ‘What is going on?’ ” said Mary Coppola vice president marketing and communications for the United Fresh Produce Association in an earlier interview with a reporter.
“There is something going on . . . We don’t know what it is.”
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