Preliminary Findings from Cyclospora Outbreak Associated with Romaine Lettuce in 2018

A Blue Ribbon Panel was put together to investigate the 2018 cyclospora outbreak associated with Romaine lettuce.   Little is know about this parasite and the goal of the panel was to focus on root-cause assessment, preventive measures/controls, collaborative approach, and testing validation.  "Although several outbreaks attributed to C. cayetanensis occurred during 2018 that were linked to fresh produce — particularly multi-commodity vegetable trays, cilantro, and others — this working group focused initial attention on the outbreak associated with a romaine lettuce mix."

Cyclospora is a human-specfic parasite that has been problematic in RTE produce such as lettuce (2018), veggie trays (2018), raspberries, and cilantro.  Cyclospora is spread by people ingesting food or water that was contaminated with feces from an infected individual.

For this case, "Outbreak investigative evidence, epidemiology, trace-back, and secondary on-farm investigative follow-up strongly indicated raw material contamination to a domestic production source in California"

While the report provides a pretty broad list in the root cause analysis, the recommendations for preventive controls focus on key elements:

"Recommendations

• Source protection for agricultural water should emphasize protection against human fecal contamination.
• Because humans appear to be the primary reservoir for C. cayetanensis, surveillance of diarrheal illness among workers involved in propagation and harvesting of fresh produce should be conducted, and workers with diarrheal illnesses be tested for C. cayetanensis and other enteric infections.
• Equipment used in propagation and harvesting of fresh produce should be maintained and cleaned to prevent C. cayetanensis transmission.
• Prevention measures need to account for the extrinsic maturation period of C. cayetanensis. This should include awareness of events and activities in the field at least 1 to 2 weeks before harvest, or at the time of harvest with regard to water, equipment, or environmental materials that were contaminated 1 to 2 weeks earlier."

The report also provides a summary of why control measures for STEC (pathogenic E. coli are different than for Cyclospora.

"Although industry-wide efforts to prevent contamination of romaine lettuce by pathogenic bacteria focus on the use of agricultural water, several key features of C. cayetanensis differ from STEC and need to be addressed in preventing Cyclospora transmission.

• Cyclospora is more resistant to routine chemical disinfection processes than STEC. Thus, water testing and treatment targeted to control STEC may not be adequate to control C. cayetanensis
• Water source protection is focused on animal reservoirs, primarily cattle, whereas C. cayetanensis is not known to have an animal reservoir hosts. Though animals may ingest C. cayetanensis oocysts and mechanically spread them through their feces, they are not known to become infected or to amplify the number of oocysts. Thus, prevention of human fecal contamination appears to be the primary need for water source protection.
• C. cayetanensis appears to require at least 1 to 2 weeks under favorable environmental conditions to become infectious. This lengthy extrinsic maturation period must be taken into account when considering the possibility and plausibility of fresh produce becoming contaminated through various means and for the oocysts (if not already infective when the produce becomes contaminated) to have sufficient time, under favorable conditions, to become infective by the time that the contaminated produce is consumed."

There were additional recommendations made on surveillance and testing.

https://www.freshexpress.com/sites/default/files/brp_interim_report_6.5.19-final.2_2.pdf
Interim Report:
Blue-Ribbon Panel on the Prevention of Foodborne Cyclospora Outbreaks
June 5, 2019


Abstract
In the spring and summer of 2018, Fresh Express and other fresh produce suppliers were linked to a Cyclospora cayetanensis outbreak — with U.S.-grown fresh produce samples testing positive for the parasite. To address this issue, Fresh Express formed the Blue-Ribbon Panel on the Prevention of Foodborne Cyclospora Outbreaks, comprising scientists with deep expertise in the biology of the organism, food safety, outbreak response, and public health. The panel was charged with studying the parasite and identifying controls to limit further C. cayetanensis–associated outbreaks. After a November 2018 in-person meeting, the Blue-Ribbon Panel formed four working groups that continued to work on C. cayetanensis specific issues related to root-cause assessment, preventive measures/controls, collaborative approach, and testing validation over the next several months. This report contains the working groups' preliminary findings, recommendations, and continuing priorities to more effectively prevent and control C. cayetanensis outbreaks going forward.