Packaged salads linked to illness outbreak in the US

While health agencies around the world respond to the COVID-19 public health crisis, experts from the US FDA and the Centers for Disease Control and Prevention (CDC) are also busy responding to a threat of a different kind. A multi-state outbreak of Cyclospora illnesses.

Cyclospora cayetanensis is a parasite that is so small it can only be seen with a microscope. It causes an intestinal illness called cyclosporiasis from the consumption of contaminated food, mainly fresh produce, or contaminated water.

Identifying the source

A new method developed and validated by the FDA was used to sample for Cyclospora in agricultural water, for the first time in a field investigation. This method was used in the agency’s current investigation and may be instrumental in its efforts to better understand the dispersion of the parasite in the environment, which could help prevent future outbreaks.

In this outbreak in the US, CDC reported 690 cases across 13 states, with 37 hospitalisations and no deaths. Onsets of illness ranged from 11 May 2020 to 20 July 2020.

Traceback of cases revealed the bagged salad codes most likely to have resulted in illness contained iceberg lettuce from California and red cabbage from Florida. “The FDA evaluated and investigated each of the ingredients in the bagged salads, identifying red cabbage from Florida and iceberg lettuce from California as those most likely in the bagged salads consumed by people who became ill. Traceback investigations are time-consuming work but are critical. In this instance, in the wake of traceback and collaboration with the retailers to recall product, FDA identified a noticeable decline in illnesses that matched the time period in which cabbage sourcing shifted from Florida to another area, providing a possible clue in the investigation,” said Frank Yiannas, Deputy Commissioner for Food Policy and Response in the US FDA statement.

“Environmental sampling detected the presence of Cyclospora in the surface water of a canal near a farm suspected of being a source of the red cabbage. Two samples collected to the north and south of where the farm accessed canal water for seepage irrigation were found to be positive for Cyclospora cayetanensis.”

The farm that supplied red cabbage was no longer in production at the conclusion of the growing season, so it was not possible to sample product. Additionally, the farms growing iceberg lettuce in California were investigated and all of the samples collected in California were negative for Cyclospora. Given the emerging nature of genetic typing methodologies for this parasite, the FDA was unable to determine if the Cyclospora detected in the canal was a genetic match to the clinical cases. Therefore, there was not enough evidence to conclusively determine the cause of this outbreak.

Enhancing traceability to improve safety

“While we as public health agencies have gotten better at detecting foodborne illnesses due to Cyclospora, our ability to trace contaminated foods back to their source has lagged, and once again, our ability to trace has been a challenge in this investigation, due in part to the lack of modernised food traceability capabilities,” the US FDA statement continued.

The agency, however, highlighted that the detection of the parasite in surface waters near the product puts a spotlight on the importance of managing the quality of irrigation water used to grow ready-to-eat crops.

“These findings further emphasise the importance of industry’s role in ensuring that irrigation water is safe to be used on produce. Under the FDA’s recently released New Era of Smarter Food Safety Blueprint, we’ll continue to remain laser focused on prevention. In the coming months, we will be issuing a proposed rule that will aid in achieving our goal of enhancing traceability to greatly reduce the time it takes to identify the origin of a contaminated food or ingredient tied to a recall and/or outbreak.”

The agency also aims to revise certain agricultural water requirements to address practical implementation challenges while protecting public health. “We also plan to advance detection techniques that will help us pinpoint sources of Cyclospora outbreaks and to continue our research around water treatments for this parasite.

“We believe the entire fresh produce supply chain from farm to fork can do better and we look forward to continuing our work with our public health partners, growers, processors, distributors and retailers in our shared efforts to protect consumers.”

Image credit: ©stock.adobe.com/au/annapustynnikova