Cyclosporiasis on the Rise. What Is and Can Be Done

The number of domestically acquired cases of cyclosporiasis in the U.S. has been increasing in recent years, with more than 2,000 confirmed cases reported in the most recent outbreak, which is causing Cyclospora cayetanensis (C. cayetanensis) to become a significant cause for concern. Historically, the intestinal illness has been associated with travel to places where Cyclospora is endemic, but domestic cases are now on the rise. In addition to the 2,000 of 2023 for which no source has been identified, roughly 3,000 cases of domestically acquired cyclosporiasis have been reported within the last three years traced to both domestic and imported produce. Additionally statistics show that the rise goes back even further with cyclosporiasis cases having increased about three-fold since 2016, with cases often linked to the consumption of leafy herbs and ready-to-eat salads

It is such numbers that led to FDA’s creation of the Cyclospora Task Force in 2019, comprising multidisciplinary experts across FDA and CDC with the goal of reducing the public health burden of foodborne illness caused by C. cayetanensis in produce. Among the actions set by the Task Force strategic plan was the charge to develop a report to improve the understanding of C. cayetanensis; its sources and routes of contamination; prevalence; and produce control measures based on available science. The charge was answered by the National Advisory Committee on Microbiological Criteria for Foods (NACMCF) which has now published a report addressing questions posed by the Task Force and providing recommendations.

Citing awareness of the factors that can contribute to C. cayetanensis contamination of produce as key to developing effective detection, prevention, and management strategies, the Task Force made four major recommendations, summarized below:

1. To facilitate future research and identification and validation of control strategies, a practical method of propagating C. cayetanensis oocysts under laboratory settings should be developed.
2. Because of the limited availability of C. cayetanensis oocysts, research with surrogates (specifically Eimeria) can provide some information on persistence in the production environment and identification of control strategies.
3. Method development for the detection of C. cayetanensis should:
4. Include “the evaluation of multiple genetic targets representing different regions of the genome.”
5. Have any modifications to current molecular methods thoroughly validated for impacts on specificity before being used on food or environmental samples.
6. Be designed to be robust, reproducible, and tolerant of minor modifications in the methodologies without sacrificing specificity or sensitivity.
7. To help prevent human transmission, preventive measures should center around clear sanitation guidelines, ensuring on-site capacity for implementing sanitation protocols (i.e., readily accessible hand washing stations with soap, etc.) and periodic training of the employees.

While it is essential that research continue and detection methods be improved, we see the fourth point as the most applicable to food industry producers at this time. Although the precise ways that food and water become contaminated with Cyclospora are not well understood, fecal contamination from symptomatic or asymptomatic carriers is the only known source because humans are the only known reservoir and are an essential host for its lifecycle. So, as with Hepatitis A or Norovirus personal hygiene and sanitation at every step of the food chain is and will be a critical aspect of its control, regardless of any new detection and control measures found. Thus, a first step in preventing transmission is for those who are sick to stay home, and for businesses to ensure all employees are well trained on personal hygiene and handwashing – and follow through in practice.