Challenges of Preventing Leafy Green Outbreaks

Cyclospora outbreaks since the 1990s have had high attack rates. “This suggests that contamination doesn’t occur sporadically, and that there’s a much more widely disseminated source for the parasite,” Dr. Osterholm says.

The parasite must live seven to 14 days outside of the human body to mature and be capable of infecting other humans. “If a parasite is excreted in a human stool, for example, it requires that time period to pass before it becomes infectious,” he says.

Given this information, the panel is looking to determine potential sources and preventive controls, including if water can spread Cyclospora. Dr. Osterholm surmises that water used for irrigation or spraying could be the culprit. Perhaps water could become contaminated from septic systems leaking into water sources.

“We need to make sure that there’s no intentional or unintentional release of human fecal material into waterways,” Dr. Osterholm says. “A number of actions could be implemented to reduce the potential for Cyclospora to enter water and to prevent water that contains the parasite from being used on plants. Because the parasite is highly resistant to chlorination, the chemical can’t be used to help solve the problem.”

On April 19, the California Leafy Greens Marketing Agreement (LGMA) Board adopted more stringent requirements designed to reduce risks related to water used in growing leafy greens. The updates include specific directives such as no longer allowing the use of untreated surface water for overhead irrigation of leafy greens prior to harvesting, says April Ward, MSc, communications director, California LGMA, Sacramento, Calif.

The new standards are in direct response to FDA investigations of last year’s E. coli outbreak involving romaine lettuce. Clues pointed to irrigation water from sources such as canals and reservoirs as a possible cause.

California LGMA devised the new water metrics by working closely with Western Growers, who coordinated a working group, and Arizona LGMA. The organizations looked at water sources and how they’re being used in production. “It’s unlikely that water from deep wells could be contaminated with human pathogens because the Earth provides an effective filtration process to eliminate bacteria,” says Dr. Whitaker. “Well water can therefore be used without fear of cross-contamination, provided the delivery system is well maintained and inspected.

“But surface waters such as ponds or canals are more likely to be impacted by runoff from pasture lands or animal operations, wild animals, wind-blown dust, or even septic systems—making it necessary that they’re evaluated and perhaps treated with disinfectants to manage potential pathogen contamination,” Dr. Whitaker continues.

“LGMA’s program has always required growers to test their water because it can carry pathogens,” Ward says. “But the new requirements include additional safeguards that ensure farmers categorize the water source and consider how and when water is applied to a crop; conduct testing to ensure water is safe for the intended use; and sanitize water if necessary.”

The new metrics will become part of mandatory government audits that comprise the LGMA’s food safety system. The LGMA will also begin an education and outreach effort to ensure that all members of the leafy greens community understand how to comply with the new standards, Ward says.

Other Efforts to Ensure Safety

Many other groups and organizations are also committed to improving leafy green safety. The CEOs of the United Fresh Produce Association and the Produce Marketing Association are co-leading a Romaine Task Force that includes a diverse group of industry thought leaders, FDA, CDC, trade groups, public interest groups, and academic scientists throughout the supply chain.

Following the 2018 outbreaks involving romaine, the task force is tackling key issues around produce labeling to allow consumers to know where their romaine was grown, permit supply chain-wide traceability, explore science-related issues around agricultural water and root cause analysis, and identify and prioritize improvements in the investigative process, Dr. Miller says.