A Conversation on Cyclospora with Samir Assar, Socrates Trujillo, and Alexandre da Silva
Cyclosporiasis is a foodborne intestinal illness caused by the parasite Cyclospora cayetanensis (C. cayetanensis). According to the Centers for Disease Control and Prevention (CDC), there have been roughly 4,600 reported domestically acquired cases of cyclosporiasis over the last three years. Yet, this is a relatively new pathogen of concern in the U.S. and what we understand about this parasite continues to evolve. Cyclosporiasis outbreaks pose unique laboratory, traceback, epidemiological and prevention challenges that are unlike foodborne outbreaks caused by bacterial pathogens.
Rising case numbers and the emergence of C. cayetanensis in domestically grown produce prompted the FDA to bring together multidisciplinary experts to form the Cyclospora Task Force in 2019. In July 2021, the FDA Cyclospora Task Force released the Cyclospora Prevention, Response and Research Action Plan for reducing the public health burden of foodborne cyclosporiasis in the United States caused by C. cayetanensis in both domestically grown and imported produce. This action plan focused on three main areas: improving prevention, enhancing response activities, and filling knowledge gaps.
In a conversation, Samir Assar, Ph. D, Director of the Division of Produce Safety (DPS), at CFSAN’s Office of Food Safety, Socrates Trujillo, Ph.D, Acting Director of the Division of Virulence Assessment (DVA) at CFSAN’s Office of Applied Research and Safety Assessment (OARSA), and Alexandre (Alex) da Silva, Ph.D, Senior Biomedical Research and Biomedical Product Assessment Service (SBRBPAS) Expert discuss the FDA’s efforts to fight Cyclospora outbreaks, some of actions that the agency has taken, and the importance of working with stakeholders to address this public health issue.
What is Cyclospora and what makes it so different from the causes of other foodborne diseases?
Alex: C. cayetanensis is a parasite that is spread through the contamination of food or water with human feces and its life cycle resembles other parasites that reproduce sexually. In some cases, it may take up to two weeks before a person feels sick, due to either the immune system of the affected individuals or potential previous exposure to the parasite. By that time the implicated product may already be off shelves, which impacts sampling to support outbreak investigation efforts. Also, C. cayetanensis does not multiply outside the host. This creates a significant challenge when using microbiological methods for detection and characterization in food or environmental samples. To make it even more challenging, no systems exist to grow this parasite in vitro or in vivo and there are no practical approaches to determine its viability on samples. Altogether this makes C. cayetanensis very different from bacterial foodborne pathogens.
What was the purpose of creating the Cyclospora Task Force and action plan?
Samir: Prior to 2018, infections caused by C. cayetanensis had been rising but were thought to stem only from internationally sourced produce. The FDA used increased surveillance activities and import alerts, while also developing better methods for detecting the parasite in food and water to address this. However, when we found the parasite in domestically grown produce, we recognized that we needed more tools and expertise. So, we formed the Cyclospora Task Force to bring together a diverse group of skillsets and experts that could collectively identify actions and approaches to help minimize contamination and illness caused by C. cayetanensis.
The task force released the Cyclospora Prevention, Response, and Research Action Plan in July 2021. This plan lays out our vision and the actions we need to take to get there. It also acknowledges that we still need to learn more about the prevalence and behaviors of C. cayetanensis in order to make meaningful progress on the prevention and response front.
What has the task force been working on?
Alex: Because C. cayetanensis is so different from bacterial pathogens, we’ve focused a lot of our efforts on just trying to better understand this unique parasite and how it behaves. This information will help us to close some of our existing knowledge gaps, and one of the tools we used to do that is sampling. The FDA has completed several sampling assignments across the U.S. that included produce and environmental samples, such as surface water. Sampling assignments are critical for improving our prevention and outbreak response. As part of continuous efforts to protect U.S. consumers, the FDA increased the seasonal surveillance sampling of imported fresh herbs that have been implicated in past cyclosporiasis outbreaks. The samples collected are analyzed for human fecal pathogens including C. cayetanensis; if the product sample is positive such that the product appears adulterated, entry of the product into the United States is refused after a process that allows the importer to provide evidence supporting admission. The FDA is also planning sampling projects domestically to help identify seasonal patterns of produce contamination, and the relationship to seasonal outbreaks, such as cyclosporiasis outbreaks.
Socrates: We’re also updating the existing microbiological methods and building on a genotyping method that the CDC developed for clinical samples. This will allow us to be able to genetically characterize C. cayetanensis found in fresh produce and mixed-type foods, such as fresh salsa or guacamole, or environmental samples, such as soil and water. Hopefully these technological advancements will help us to speed up our response activities and conduct more timely root cause investigations into how contamination may have occurred, which will contribute a wealth of knowledge to our understanding of this parasite.
Samir: In addition to enhancing microbiological methods, we supported our stakeholders and partners by developing a farm investigation questionnaire that investigators can use to document conditions and collect data during outbreak investigations and sampling assignments. We’ve also produced eight webinars to educate U.S. farmers and our stakeholders on the background information, risk assessment and preventive measures for C. cayetanensis, provided training for the FDA and state investigators, and worked with the National Advisory Committee on Microbiological Criteria for Foods on a charge document to address knowledge gaps of C. cayetanensis and guide the prioritization of Cyclospora research.
We also worked with the CDC to compile data summarizing all the cyclosporiasis outbreaks in the U.S. from 2013 to 2020 that was then published in an article for Food Safety Magazine . This article provides specific details about the related outbreak investigations, describes the results from the FDA’s sampling efforts, and explains some of the challenges that both the FDA and CDC face when taking action to reduce the public health burden caused by cyclosporiasis.
We encourage everyone to visit the FDA’s Cyclospora Prevention, Response and Research Action Plan web page to see a complete list of actions that our team has taken to address cyclosporiasis outbreaks.
What’s next for the task force?
Alex: Of course, we will continue our efforts to carry out the FDA’s vision through our Cyclospora action plan and work with stakeholders to fill existing knowledge gaps. We also want to partner with the Center for Produce Safety and other stakeholders to improve strategies for preventing produce contamination at the farm level. In addition to developing the next generation of rapid, streamlined and inexpensive methods that could, for instance, monitor for the presence of C. cayetanensis in agricultural water. improve strategies for preventing produce contamination at the farm level.
Socrates: Gaining a better understanding of the prevalence of C. cayetanensis in the U.S. and understanding transmission trends. C. cayetanensis is a parasite that appears to be distributed unevenly in food and water sources, sometimes in low concentrations and perhaps seasonally, thus making it difficult to understand how prevalent the contamination might be. Further, this often difficult to find parasite cannot be grown in a laboratory, unlike bacteria such as E. coli and Salmonella. Meeting these challenges will require cooperation across the food safety system.
Samir: There is a lot we’re still learning about how C. cayetanensis contamination occurs, how it survives and persists in the environment, and why we only seem to see a seasonal pattern of outbreaks. These knowledge gaps hamper our ability to develop more effective methods to disrupt the parasitic life cycle and the contamination process. It’s critical that we continue to work with our stakeholders to share data and research that will contribute much-needed information we can all benefit from. We know that states, academia, and industry are also doing this research, and by working together, we can better understand, prevent, and respond to Cyclospora.
Any other thoughts?
Alex: We know that this is an important public health issue, and that’s at the heart of everything we do here at the FDA. It’s almost like working with puzzle pieces. It takes time but each piece brings you that much closer to solving the overall puzzle. Plus, we’ve been fortunate to have help from our state, local, industry, and federal partners who are all committed to finding solutions to this issue.
To learn more about Cyclospora and the FDA’s prevention, response and research efforts, visit our Cyclospora and the Cyclospora Prevention, Response and Research Action Plan webpages.