New technology is tackling outbreaks of illness from bagged salads containing a parasite called Cyclospora cayetanensis. The new method has been developed and validated by the US Food and Administration (FDA) to sample for Cyclospora in agricultural water for the first time in a field investigation as a preventative measure. However, the FDA reports there is still much to be done to swiften traceability to the source amid repeated outbreaks. The microscopic parasite causes an intestinal illness caused by the consumption of contaminated food, mainly fresh produce, or contaminated water. Through speedier tracing times and collaboration with the Centers for Disease Control CDC and industry, the FDA aims to reduce or eliminate Cyclospora outbreaks.

“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 modernized food traceability capabilities,” says Frank Yiannas, Deputy Commissioner for Food Policy and Response. 

In the most recent outbreak, CDC has reported 690 cases across 13 states, with 37 hospitalizations and no deaths. onsets of illness range from May 11, 2020 to July 20, 2020. Salads made by Fresh Express and containing iceberg lettuce, red cabbage and carrots were identified as the food vehicle responsible for the outbreaks. The FDA has previously issued a recall on the Fresh Express salad bags after consumers began to fall ill. 

The number of reported cases of Cyclospora typically rises during May through August. Although CDC conducts surveillance for cyclosporiasis year-round, during the spring and summer months CDC conducts enhanced surveillance for cases of domestically acquired illness. 

“Even as our agencies continue to respond to the COVID-19 public health crisis, teams of experts from the FDA and the CDC have continued to respond to a threat of a different kind – a nationwide outbreak of Cyclospora illnesses. This [new] method was used in our current investigation and may be instrumental in our efforts to better understand the dispersion of the parasite in the environment, which could help prevent future outbreaks,” continues Yiannas.

Traceback of cases with the strongest sources of information, such as shopper card info, revealed that 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.

The traceback investigation was “time-consuming but critical,” reports the FDA. In this instance, in the wake of traceback and collaboration with the retailers to recall products, the 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.

The detection of the parasite in surface waters near wher the product was grown once again puts a spotlight on the importance of managing the quality of irrigation water used to grow ready-to-eat crops. “We are working closely with our colleagues at the Florida Department of Agriculture and Consumer Services to investigate this issue further to prevent future occurrences,” he adds. 

Inconclusive evidence
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 wher 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 products. 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 has been unable to determine if the Cyclospora detected in the canal is a genetic match to the clinical cases, therefore, there is currently not enough evidence to conclusively determine the cause of this outbreak.

Developing new testing methods
The FDA has developed new ways to detect the parasite that have been employed in this outbreak investigation, developing and validating new methods to test for Cyclospora in produce and agricultural water. The first of these new methods was used in 2018 to confirm the parasite’s presence in a salad mix product tied to an outbreak that sickened hundreds of people. 

In July 2019, the FDA made its second major advancement in Cyclospora detection, completing studies that resulted in a novel, validated method to test agricultural water for the presence of the parasite. These new methods were developed by the Foodborne Parasitology Research Program that the FDA established in 2014 in the Center for Food Safety and Applied Nutrition, in part to break the cycle of recurring Cyclospora outbreaks.

“In identifying clinical cases of Cyclospora, assisting in providing traceback records and completing investigations in processing facilities and growing fields, our state partners’ work has proven essential to this investigation,” notes Yiannas. 

One example of coordinated collaboration is the CDC’s piloting of a genotyping tool to help identify cases of the parasitic illness that might be linked to a common source.