Federal officials won’t say definitively that contaminated canal water was behind this year’s deadly E. coli outbreak linked to romaine lettuce, but they are saying they “found no evidence in support of alternative explanations.” 

Another point made clear in an outbreak investigation report released yesterday puts the FDA firmly on record when it comes to antiquated shipping and receiving recordkeeping used by many in the leafy greens industry. Scott Gottlieb, commissioner for the Food and Drug Administration, issued a blunt statement calling for growers, processors and distributors to do the right thing.  

Gottlieb said what consumer groups and industry observers have been saying for months — traceback efforts to determine the specific romaine behind the outbreak were “challenging” because most of the necessary records were hand written and/or were not available electronically. Those out-of-date methods resulted in the FDA and CDC telling the public to avoid all romaine grown in the Yuma, AZ, area earlier this year because specific growers and shippers could not be identified. 

“We strongly encourage the leafy greens industry to adopt traceability best practices and state-of-the-art technologies to help assure quick and easy access to key data elements from farm to fork,” Gottlieb said.

“We also strongly encourage the leafy greens industry to explore modern approaches to standardized record keeping and the use of additional tools or labels on product packaging that could improve traceability.”

Portions of the investigation memorandum posted yesterday have been blacked out by the government. Much of the redacted information appears to be specific locations of growing fields and possibly names of romaine growers and processors.

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The E. coli O157:H7 outbreak this spring sickened 210 people across 36 states, hospitalizing 96 patients. Five people died, according to the Centers for Disease Control and Prevention. Of the laboratory-confirmed patients, 27 developed a type of kidney failure known as hemolytic uremic syndrome (HUS). It was the largest E. coli outbreak in the United States since the 2006 outbreak traced to fresh spinach.   

In a response to the FDA’s report, the CEO of the California Leafy Greens Marketing Agreement (LGMA) organization said the industry is committed to producing safe food. Members of the California group, as well as its counterpart organization in Arizona, are operating under new rules for the 2018-19 season. The changes imposed on the voluntary members include requirements for daily cleaning of equipment and increasing buffer zones between animal feedlots and fields used to grow lettuce and other fresh produce commodities.

Growers in the Yuma area began planting this season’s romaine in late August and expect to begin harvest later this month.

“The FDA report highlights areas of concern and opportunity for collaboration,” CEO Scott Horsfall wrote on the California organization’s website. “LGMA members know a lot about keeping leafy greens safe and we are continually working to improve our program so that consumers can continue to enjoy leafy greens with confidence.”

FDA Commissioner Gottlieb also stressed the need for collaboration. He thanked those in the leafy greens industry for the assistance they provided during and after the outbreak, but said “more must be done on all fronts to help prevent future foodborne illness outbreaks.” Enforcement is one of those fronts.

“The agency is taking steps to improve our response times and provide actionable information to consumers as quickly as possible,” Gottlieb wrote. 

“We are also looking at our regulatory options and considering appropriate enforcement actions against companies and farms that grow, pack, or process fresh lettuce and leafy greens under insanitary conditions.”

Toward that end, the FDA plans to undertake a temporary sampling program to collect and analyze romaine lettuce for contamination. Gottlieb promised if samples are found to be contaminated, the FDA will follow-up with leafy greens processors and their growers or suppliers to determine whether to remove the romaine from the marketplace.  

Not the first time, or the second, or the third …
Following the 2006 spinach E. coli O157:H7 outbreak that sickened at least 205 people, hospitalizing 104 and killing four, the California and Arizona leafy greens industry implemented self-imposed regulations. Those changes were inadequate, according to the FDA officials.

“FDA and our partners at CDC identified 28 foodborne illness outbreaks of Shiga-toxin producing E. coli (STEC) with a confirmed or suspected link to leafy greens in the United States between 2009 and 2017. This is a time frame that followed industry implementation of measures to address safety concerns after a large 2006 outbreak of E. coli O157:H7 caused by bagged spinach,” according to the Environmental Assessment report and accompanying memorandum released yesterday by the agency.

The apparent failure of the revised food safety protocols for the LGMA members also earned a mention in a Nov. 1 letter sent to produce industry groups and state officials in California and Arizona. Two of the FDA’s top food safety officials — Deputy Commissioner for Foods and Veterinary Medicine Stephen Ostroff, M.D., and Associate Commissioner for Regulatory Affairs Melinda K. Plaisier — sent the letter to say more revisions are needed.

“… our approaches to prevent leafy greens contamination must change to protect public health,” Ostroff and Plaisier wrote.

“The safety of raw whole and freshcut (e.g., bagged salad) leafy greens is a longstanding issue. As far back as 2004, FDA issued letters to the leafy greens industry to express our concerns about outbreaks associated with this commodity. Leafy greens are mostly consumed raw, without cooking or processing steps to eliminate microbial hazards. Therefore, the way they are grown, harvested, packed, held, processed and distributed is crucial to ensuring that contamination with pathogens is minimized.”

Canal water most likely spread bacteria
The FDA’s Environmental Assessment (EA) report says traceback identified 36 fields on 23 farms in the Yuma growing region as having supplied romaine lettuce that was potentially contaminated and consumed during the outbreak. Many of the romaine growers used water from an open canal near Wellton in Yuma County. The investigators began the environmental assessment in June, finishing their work in August.

Samples collected from a 3.5-mile stretch of the open canal were positive for the relatively rare outbreak strain of E. coli O157:H7. Investigators tested water from the Colorado River, which feeds the canal, but did not find the outbreak strain. 

“This strain of E. coli O157:H7 was not detected in any other (environmental) samples collected during this EA, although other human pathogens were found in these samples,” according to the FDA report. 

By the time investigators were on the scene in the growing area, the romaine fields had been tilled in preparation for future use, making soil sampling virtually useless. However, they visited farms that potentially shipped contaminated romaine and, when appropriate, sampled those fields and adjacent areas.

During interviews, though, investigators began to suspect contaminated water as the most likely vector for the deadly E. coli.

“… based on interviews with growers and pesticide applicators, plausible explanations include direct application of irrigation canal water to the lettuce crop or the use of irrigation canal water to dilute crop protection chemicals applied to the lettuce crops through both aerial and land-based spray applications,” according to the environmental assessment report.

Growers and industry representatives have repeatedly said the contamination could have been the result of a perfect storm of unusual weather conditions. The FDA report says a freeze in late February likely led to damage of some portion of the romaine crop, which “may have rendered it more susceptible to microbial contamination.” Overall, though, the FDA soundly debunked the weather theory. 

 “Growers suggested weather events in the Yuma growing region may have contributed to crop contamination. The (environmental assessment) team considered the possibility that leaf freeze damage and dew on romaine leaves created conditions favorable for windborne contamination of the crop with dust carrying the outbreak strain of E. coli O157:H7,” the FDA report says.

“While this type of STEC contamination has been demonstrated (Berry et. al, 2015), it does not explain the presence of the outbreak strain in a free-flowing irrigation canal months later when there was little wind in the region.”

Feedlot probable origin of the E. coli
Investigators say there are some factors that point to a 100,000-head feedlot next to the romaine growing area as the most likely source of the E. coli bacteria that was found in the canal water.

For example, the timing of the illnesses, which began in early March, suggests the outbreak strain may have been present in the irrigation canal months before the investigators collected water samples. Or, the outbreak strain may have been repeatedly introduced into the irrigation canal along the 3.5-mile stretch where the samples were collected.   

“A large concentrated animal feeding operation (CAFO) is located adjacent to this stretch of the irrigation canal. The EA team did not identify an obvious route for contamination of the irrigation canal from this facility; in addition, the limited number of samples collected at the CAFO also did not yield the outbreak strain,” the FDA reported 

“Other possible explanations for how the irrigation canal became contaminated are possible, but the EA team found no evidence in support of alternative explanations.”

Some people outside government and industry have speculated the E. coli came from human sources, such as field workers. That wasn’t the case, according to the investigators, who specifically state human beings are not “chronic carriers” of the pathogenic serotypes of the bacteria.

However, the intestinal tracts of ruminant animals such as cattle are “well-established reservoirs for E. coli O157:H7,” according to the FDA report.

“Various fresh water sources, including municipal well, and recreational water, have been the source of E. coli O157:H7 infections in humans, as has contact with colonized animals at farms or petting zoos. However, most E. coli O157:H7 infections in humans occur from consuming contaminated food.”   

Also supporting the theory that the canal water was contaminated by the feedlot was the discovery that sections of the Wellton irrigation canal are unlined. Groundwater could be seeping into the canal in those sections. Shallow ground water is also pumped directly into the irrigation canal at two locations, according to the FDA report.

“Based upon Bureau of Reclamation hydrologic data, including a Bureau of Reclamation Wellton Area Groundwater Map, the EA team determined that ground water under the Wellton-area CAFO most likely flows from the southeast towards the northwest,” the FDA reported.

“This roughly aligns with groundwater flowing from the CAFO area toward the unlined sections of the Wellton irrigation canal that are upstream of the CAFO in terms of irrigation canal flow.”

Bureau of Reclamation staff told FDA the section of canal is not lined because “ground water upwelling damaged the previous cement lining.” 

The Yuma growing area includes fields in California’s Imperial Valley, according to the FDA. In July investigators collected and tested water from three irrigation canals there that serve Imperial County farms that were identified during the outbreak traceback efforts.

“… all three of these irrigation canals have CAFOs near them. Six strains of E. coli O157:H7, each genetically distinct from each other, were detected at one canal water site (Spruce Main Delivery 49/50) in Imperial Valley, although none match the outbreak strain,” the FDA reported. 

FDA recommendations

  • Assure that all agricultural water (water that directly contacts the harvestable portion of the crop) used by growers is safe and adequate for its intended use (including agricultural water used for application of crop protection chemicals);
  • Assess and mitigate risks related to land uses near or adjacent to growing fields that may contaminate agricultural water or leafy greens crops directly (e.g. nearby cattle operations or dairy farms, manure or composting facility);
  • Verify that food safety procedures, policies and practices, including supplier controls for fresh-cut processors, are developed and consistently implemented on farms (both domestic and foreign) and in fresh-cut produce manufacturing/processing food facilities to minimize the potential for contamination and/or spread of human pathogens;
  • When a foodborne pathogen is identified in the growing or processing environment, in agricultural inputs (e.g., agricultural water), in raw agricultural commodities or in fresh-cut ready-to-eat produce, a root cause analysis should be performed to determine the likely source of the contamination, if prevention measures have failed, and whether additional measures are needed to prevent a reoccurrence; and
  • Local in-depth knowledge and actions are critical in helping resolve potential routes of contamination of leafy greens in the Yuma growing region, including Imperial County and Yuma County moving forward. FDA urges other government and non-government entities, produce growers and trade associations in Yuma and Imperial Counties to further explore possible source(s) and route(s) of contamination associated with the outbreak pathogen and with other foodborne pathogens of public health significance. This information is critical to developing and implementing short- and long-term remediation measures to reduce the potential for another outbreak associated with leafy greens or other fresh produce commodities.

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