Public still waiting for answers in romaine lettuce E. coli outbreak

The extensive romaine recall of 2018 is a testament to the difficulties in pinpointing tainted produce

Public still waiting for answers in romaine lettuce E. coli outbreak

We are often reminded that nature, not mankind, controls the universe.

There is no shortage of examples: draconian fires and floods linked to climate change and tragedies such as the influenza virus in the early 20th century that killed millions. We also see people’s reluctance to prevent the damage nature asserts even though appropriate tools are at hand or could be developed. In this category we might include personal reluctance to use free influenza vaccine or development of effective vaccines against diseases like African swine fever because of an outdated slash-and-burn regulatory decree.

Although the present struggle in Canada and the U.S. with E. coli contamination of romaine lettuce seems smaller in scale than Paradise, California, being decimated by fire, or the billions of dollars lost to floods along the east coast, answers to the Shiga toxin-producing E. coli (E. coli O157: H7) outbreaks in Canada and the United States remain obscure. Despite one-and-a-half years of investigation, there are no definitive answers as to why life-threatening infections associated with irrigated romaine lettuce persist and why steps taken to eliminate risk are little more than taking romaine off produce shelves.

The multi-state outbreak of E. coli from the U.S. is genetically similar to the strain that affected Canadians and is genetically related to the E. coli that caused similar outbreaks over the last 18 months. Investigators are quite certain ill people on both sides of the border share a common source of infection. The Public Health Agency of Canada has identified romaine lettuce as the source, but it notes the cause of contamination has not been identified with certainty.

The primary job of animal health and public health organizations is to launch disease investigations that provide answers to sources of infection and provide direction in eliminating them. Their work then moves toward developing and evaluating strategies to prevent future outbreaks. An important element throughout the entire process is addressing public concerns. Important pieces were missed along the entire journey of the romaine lettuce contamination.

As late as November 20, 2018, federal health officials in the U.S. could only warn people not to eat romaine lettuce anywhere in the country. Although federal investigators in the U.S. identified a central California farm they believe responsible for the latest E. coli outbreak, as of December 29, 2018, they were unwilling to declare the danger as over.

The extensive romaine recall of 2018 is a testament to the difficulties in pinpointing tainted produce from thousands of farms across the country. Despite availability of modern genome sequencing at local, state and federal levels, a great deal of time is still spent incorporating low-tech investigative methods like individual interviews to determine clusters of illness and collecting soil and water samples at suspected farms and processing plants for culture.

Roughly 30 million meals a day in the U.S. contain romaine lettuce, approximately 30 percent of lettuce consumption. By the second week of November, just days before U.S. Thanksgiving, E. coli O157:H7 appeared in laboratory samples submitted from 11 states from California to New Hampshire. A vast surveillance network known as PulseNet helps identify genetic fingerprints of the outbreak strain of E. coli. By early December, investigators were relatively certain they had found the source, a family farm in Santa Barbara County. Out of an abundance of caution, federal health authorities in Canada and the U.S. advised consumers not to eat romaine lettuce regardless of its origin. An advisory remains on romaine originating from several central, coastal California counties, such as Monterey, San Benito and Santa Barbara. Canada’s Public Health Agency followed suit.

On his blog, Dr. Doug Powell, food scientist previously associated with Kansas State College of Veterinary Medicine in the department of diagnostic medicine and pathobiology, commented that the produce industry needs a “self-reckoning.” He goes on to quote Candice Choi, an Associated Press journalist covering food health.

Choi wrote that the “produce industry is confronting the failure of its own safety measures in preventing contaminations.” She adds that this fall’s E. coli outbreak follows one last spring that killed five people and sickened more than 200. The year before, an outbreak sickened 25 and killed one.

“No deaths have been reported in the latest outbreak, but the dozens of illnesses highlight the challenge of eliminating risk for vegetables grown in open fields and eaten raw, the role of nearby cattle operations that produce huge volumes of manure and the delay of stricter federal food safety regulations,” Choi wrote.

One contested requirement is testing irrigation water for E. coli. The produce industry said such tests wouldn’t necessarily help prevent outbreaks so the Food and Drug Administration put the testing on hold, Choi reported. Just recently they implemented other regulations on sanitation for workers and equipment.

We’ve been saying the same thing for over 20 years, Powell concludes.

There are many ways lettuce can be contaminated with E. coli: in the field through contaminated water or manure; during harvest; during transportation and storage; at a grocery store; or in the home through cross-contamination from raw meat or poultry.

Dan Flynn, Food Safety News, on July 13, 2018, wrote: “Two weeks ago as the public was told that canal water was the likely source of the E. coli O157: H7 that caused the national outbreak involving romaine lettuce, growers in the region were told what they could immediately… do about it.

Recommended practices include treating water used for overhead irrigation and avoiding irrigation water that tests positive for E. coli O157:H7 for dust abatement or crops, Flynn added.

Flynn then quoted from a Produce Council statement: “To date, CDC analysis of samples taken from canal water in the region has identified the presence of E. coli O157: H7 with the same genetic fingerprint as the outbreak strain. We have identified additional strains of Shiga-toxin producing E. coli in water and in soil samples, but at this time, the samples from the canal water are the only matches to the outbreak strain.”

Why this investigation took so long to identify the potential source of infection is still open to question. Hard and fast measures needed to prevent a repeat are still missing other than a sweeping alert like the one issued on November 20, 2018, warning people not to eat romaine lettuce anywhere in the country.

The authors of Animal Health at the Crossroads (National Academic Press, 2005), identified gaps in the animal health framework such as:

  • Co-ordination between groups within the animal and public health frameworks.
  • Missing tools for preventing, detecting and diagnosing animal disease.
  • Impaired ability to address risk.
  • Education and training.
  • Improving awareness of the economic, social, and human health effects of animal diseases.

The gaps identified by the various authors are far from new and lead me to question if the animal health and public health industries and our emergency response capabilities have stagnated. Vulnerability sits at the doorstep of complacency. Apologies for the lack of communication by both industry and public health investigators and their recommendations to prevent further outbreaks, if forthcoming, will remain awkward at best.

Dr. Ron Clarke is a consulting veterinarian living in Alberta.

About the author


Dr. Ron Clarke

Dr. Ron Clarke prepares this column on behalf of the Western Canadian Association of Bovine Practitioners. Suggestions for future articles can be sent to Canadian Cattlemen ([email protected]) or WCABP ([email protected]).



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