Studying causes of E. coli outbreaks help determine best practices
In late winter 2017, an outbreak of E. coli in both the U.S. and Canada was traced to romaine lettuce or leafy greens, causing multiple illnesses and hospitalizations and resulting in two deaths between both countries.
The outcome of subsequent investigations was inconclusive. No specific common source could be pinpointed. While warnings were issued, no recall was. It left the industry reeling and consumers confused.
In fact, growers, shippers and distributors were just starting to come back from that outbreak when another emerged in spring 2018: 210 people infected from 36 states, 96 hospitalizations — including 27 who developed a form of kidney failure — and five deaths, according to the Centers for Disease Control and Prevention. This time, epidemiologic, lab and traceback evidence — including one significant lead to a specific supplier when inmates at a prison in Nome, Alaska, were sickened — pointed to romaine lettuce from the Yuma, Arizona growing region. It was there that E. coli was found three months later in samples of water taken from a canal.
Authorities determined that the last shipments of lettuce from that region were harvested April 16, and declared the outbreak over as of June 28, 2018.
The Public Health Agency of Canada also investigated the spring outbreak. Canada saw eight cases of E. coli genetically similar to the U.S. outbreak. The source was never identified, and that investigation closed June 22.
For the industry, though, the work was just beginning. Again.
Steve Church, chairman of Church Brothers Farms in California, estimates that about 85 percent of the lettuce consumed in the U.S. and Canada is grown in California’s Monterey, Santa Cruz, San Benito and Santa Maria counties for eight months of the year (April-late November); and in California’s Imperial Valley and the Yuma, Arizona, area for the remainder.
That’s why growers there supported forming leafy greens food safety organizations after an outbreak in 2007 sickened more than 200 people. Enter the LGMA (California Leafy Greens Product Handler Marketing Agreement) and the nearly identical Arizona Leafy Greens Products Shipper Marketing Agreement. They developed a set of science-based, food-safety best practices that became standard across the industry.
“The LGMA is a volunteer organization, but once you’re signed up, it’s not voluntary,” said Church, who also chairs the LGMA advisory board. “You have to follow the metrics and the rules, and if you don’t, there are consequences.”
In 2018, the groups faced a new challenge: to address the latest outbreak based on what they knew and could learn about circumstances that led to contamination. And so they began meeting in June as the Leafy Greens Food Safety Task Force — its members representing growers, shippers, scientists, government agencies, industry associations, produce buyers, consumer advocacy groups and industry suppliers.
“They basically developed a hypothesis of what could have happened,” said Bob Whitaker, chief science and technology officer for the Produce Marketing Association. “Out of that has come recommendations that the growers are going to follow.”
Scott Horsfall, CEO of the California LGMA, expects the new requirements to be adopted with the start of the winter growing season.
What could have happened?
Looking at evidence and data, the task force came up with several scenarios that could have caused contamination. In one, Church said, a significant wind could have carried particles of manure from a concentrated animal feeding operation (CAFO).
“Some manure may have become airborne and contaminated the romaine,” Church said. “It’s one hypothesis that’s out there.”
Water could have been the culprit, possibly from the canal via irrigation or mixed with chemicals and sprayed aerially by a crop duster.
Another scenario has unusually cold temperatures causing blistering (epidermal peel) on lettuce that left it open to contamination.
“Then a wind event came — very high winds, they think, with some of these particles in the air came down on the romaine,” Church said. “Then the weather got warm, kind of like an incubator.”
Sometimes the blistering is mild and doesn’t ruin a crop and it’s harvested and shipped. Now growers know that even then, additional testing may be warranted.
“The important thing is to know that’s a potential risk area and have a plan in place,” Horsfall said. “It’s not something we had focused on in the past.”
Equipment could be another potential hazard, maybe contaminated by drift in the air and then moved to another location 20 miles away for harvest, Whitaker said.
The task force came up with changes that address issues like proximity to animal feed lots, water, equipment and traceability.
One new standard increases the distance between animal feeding areas and where crops can be grown from 400 to 1,200 feet.
“There’s basically research that indicated that E. coli could be spread by wind out to 600 feet — this was research funded by the Center for Produce Safety conducted three to four years ago,” Whitaker said. “The limitation on that is that the field ended at 600 feet, so we don’t know how far pathogens can be spread.
“We need to look at research going forward for developing models to gain a better understanding of what the best distances are.”
California goes one step farther, expanding the buffer zone to one mile when there are concentrated CAFOs of 80,000 or more animals. Arizona expects more rigorous risk assessments to be in place in those scenarios as well.
When it comes to water, there’s going to be new emphasis on hazard analysis of water sources, especially when it comes to “if they’re using open water sources like canals that could be susceptible to contamination either through runoff from animal feeding operations or from wind,” said Whitaker, who predicts use of disinfectants in irrigation water will increase.
“There are some companies already doing that,” he said. “There’s been a great deal of activity looking at the best ways to do that and how to do that.”
Teressa Lopez, administrator of the Arizona leafy greens group, said the canal that tested positive for E. coli has been cleaned and is subject to ongoing maintenance.
“They’ve done further testing and have not found that strain of E. coli, but going into the season, we still don’t know if that was necessarily the source of contamination,” she said. “It could have also been the result of getting contaminated the same way the product did.”
As for equipment, Horsfall said a daily sanitation requirement will now be in place for equipment and food contact surfaces.
“We’ve always required that they have a plan — a schedule — but in the past, we didn’t say how often it had to be,” he said. “So the feeling is given wind conditions, and some other things, it has to be at least daily.”
And sometimes, the traceability chain gets broken. Now metrics language will require the identification of all lot data from product that goes into the food supply.
While growers, shippers and distributors generally do maintain such data, Whitaker said, the chain can be broken at points down the line where recordkeeping may not be as consistent.
“The system is set up to work, but not everybody’s on the system,” Church said.
The industry is also working with the Food and Drug Administration to improve communication and “to try and determine what kind of information is most helpful to them,” Whitaker said.
“The other side of this is you can inundate the system with information, so we’ve got to find out what they need,” he added.
“Nothing’s definitive about … what caused the outbreak, but these are all steps designed to be more protective and more cautionary and will help protect public health,” Horsfall said.
The work continues
And the process of trying to ensure against another outbreak is not finished. Whitaker said one of the ongoing efforts involves continuing to share information and learn from the FDA and CDC “to create stronger linkages … so we can be more efficient when there is an outbreak.
“We need to learn from them — the results, the data they’re generating from these investigations,” he said. “At the same time, they need to learn from us — our products, processes, how products move through the supply chain.”
Church believes there will be more product testing by the FDA. Lopez said leaders are looking at ways to strengthen guidance on raw product sampling.
“We’re also looking at … standardizing that,” she said. “Currently different companies may be doing different things.”
And expect more collaboration between the livestock and produce industries.
“There’s been a lot more communication between the produce industry and cattlemen’s industry,” Horsfall said. “There are things we’re learning about steps they’re already taking in terms of protecting public health in terms of runoff and things like that.”
In fact, California-based growers are taking point on what Western Growers Senior Vice President, Strategic Planning, Science and Technology Hank Giclas said is to continue working with the livestock industry to “fill in some of the information gaps.”
“We hosted the cattlemen on a webinar recently when they presented to the fresh produce industry the controls that are in place and who oversees them and what the rationale behind that was,” Giclas said. “The produce industry had a chance to ask and answer questions, and we’re still sort of pursuing what else we can do together.”
The hope is to actually identify livestock operations in close proximity to farms growing produce and recruit both to work together and allow researchers on site to collect data during the growing season, Giclas said.
The company is also working on developing resources to help growers conduct the more robust risk assessments now required.
“There’s probably a list of about half a dozen other resources we’re trying to develop for the industry that will go hand in glove with the new requirements and the metrics,” he said.
The FDA is working on an environmental assessment related to the outbreak. Public Affairs Specialist Brittany Behm said she hopes it will be released soon.
Meanwhile, Church acknowledges that many questions remain. As long as that is the case, the industry can’t rest.
“We feel very sorry for the people it’s affected,” he said. “Our families eat our products out of the same fields that we grow and ship.
“We’re not in the business to hurt people. We’re in the business to provide healthy products for people so they can live healthy lives.”