Notes from the Field: Cyclosporiasis outbreaks in the United States in 2022
Outbreak Description
Cyclosporiasis is an intestinal infection caused by Cyclospora cayetanensis, a coccidian parasite. C. cayetanensis appears to be the only species within the Cyclospora genus to cause the illness in humans. As a foodborne illness, the CDC conducts surveillance, and monitors potential outbreaks and clusters of cases to prevent further spread. In 2022, there were multiple outbreaks of Cyclosporiasis not linked to international travel in the United States spread across 34 jurisdictions. (CDC)
Cases
The 7/27/2022 outbreak had 43 confirmed cases, while the 8/3/2022 outbreak had 84 confirmed cases. No products were linked to these outbreaks, but the CDC reported that many patients had eaten leafy greens (FDA). In the period of May 1, 2022, to October 18, 2022, there were 1,129 laboratory-confirmed cases of cyclosporiasis, but it is likely that there were more cases that went unreported or unconfirmed. Additionally, the outbreak also spread to Canada, where there were at least 84 more confirmed cases (FSN). Within the United States, there were only 74 hospitalizations as a result of cyclosporiasis. (CDC)
Organism involved
Cyclospora cayetanensis is a coccidian parasite that has only been found in humans; there are no known animal reservoirs for the disease (CDC). Many details are unknown about the parasite, including aspects of intracellular replication and development. To watch a video about cyclospora from an accredited hospital, click here.
Symptoms and signs of infection
Cyclosporiasis presents itself mainly with intestinal and digestive symptoms, including watery diarrhoea, abnormal bowel movements, loss of appetite, weight loss, stomach cramps/pain, nausea, and fatigue. Flu-like symptoms like fever, vomiting, and headache may also occur. Some infections may not cause any symptoms. Symptoms depend on a variety of factors, including age, immune status, endemicity within an area, and other unknown factors (Giangaspero, 2019). The disease is endemic to certain tropical or subtropical zones and includes such areas as Central and South America, several countries in the Middle East, the Indian subcontinent, and Southeast Asia. (Almeria, 2019)
Lifecycle
Oocysts are ingested orally via contaminated water or produce. The oocysts excyst and free the sporozoites, which attach to the small intestine and undergo asexual, then sexual reproduction. During asexual reproduction, the sporozoites develop into either type I or type II meronts (CDC,
Cama). Merozoites from type I meronts are more likely to remain in the asexual reproduction cycle, while those from type II typically move on to the sexual reproduction phase where they develop into macro- and micro-gametocytes. Finally, they develop into a zygote where they are fertilised and turn into an unsporulated oocyst. The unsporulated oocyst is shed in the stool and
contaminates the environment. After a period of time at the right temperature (22-32°C), sporulation occurs, and the newly-sporulated oocysts can contaminate produce or water, which is then ingested, and the cycle continues (CDC). There is no direct oral-faecal transmission route, as the oocysts are uninfective when passed freshly in stool.
Figure 1: Illustration of the life cycle of C. cayetanensis,
with an expanded section on its stages in humans. To view the image in another tab, click here.
Treatment Most people with a healthy immune system recover without requiring treatment, although recovery may be within a few days or a few months. Trimethoprim-sulfamethoxazole (TMP-SMX) is the primary antibiotic used to treat more severe cases, and there are currently no alternative drugs or medicines that have been proven to be effective. Anti-diarrheal medication can help alleviate some symptoms, but do not affect C. cayetanensis (CDC).
Treatment
Most people with a healthy immune system recover without requiring treatment, although recovery may be within a few days or a few months. Trimethoprim-sulfamethoxazole (TMP-SMX) is the primary antibiotic used to treat more severe cases, and there are currently no alternative drugs or medicines that have been proven to be effective. Anti-diarrheal medication can help alleviate some symptoms, but do not affect C. cayetanensis (CDC).
Diagnostics used
Cyclospora cayetanensis is hard to detect, which makes it even harder to diagnose cyclosporiasis. There are currently no validated laboratory fingerprinting methods. Cyclospora infection is most often diagnosed by examining stool specimens for oocysts.
Challenges with diagnosis
In general, attaining the oocysts is a challenge, which complicates diagnosis because diagnosis is based on finding oocysts. Examination of stool is the most common method of diagnosis. However, even symptomatic patients might not shed enough oocysts in their stool to be detectable, so multiple stool samples are often required. Additionally, the tests that are usually conducted on stool for parasitic infection can NOT detect the oocysts, so health care providers must specifically test for cyclosporiasis in order to potentially detect it (CDC). Recent reports have shown promising new developments for recovery of oocysts, which may lead to easier diagnosis.
Impact on Society and Public Health
Due to a lack of diagnoses as well as the relatively low rate of morbidity and mortality in developed nations like the United States, cyclosporiasis rarely makes the news (Ortega, 2017). Scientists consider it a neglected disease and believe that it may be more common than is currently thought, but the limited application of accurate and standardised molecular-diagnostic and molecular-epidemiology tools make it hard to properly assess how much impact this disease actually has (Giangaspero, 2019).
Epidemiology and other information In the United States, cyclosporiasis poses less of a problem, but in many developing countries, it is thought to be a leading cause of gastrointestinal disease (Almeria, 2019). It appears that the disease has seasonal resurgences, but these vary by country and are still poorly understood, which further hinders analysis of impact (Strausbaugh, 2000). Additionally, these symptoms overlap with many other diseases and are usually not life-threatening, which makes it more likely for either a misdiagnosis or dismissal of the disease entirely. Cyclospora cayetanensis is also resistant to many of the sanitisers that the food industry typically uses, allowing it to last longer on produce (Cama, 2023). The parasite’s oocysts can survive in water and soil as well as on produce.
Summary
Cyclosporiasis is a neglected parasitic disease that can cause various gastrointestinal symptoms like diarrhoea, weight loss, and other abnormal bowel movements. There is evidence to suggest that there have been many more outbreaks not just in the US, but across the globe. Analysis and detection of this disease is hindered by a lack of information about many of its characteristics and an inability to efficiently detect the disease although progress has been made in this area with the advent of new technologies and methods that can isolate the parasite for genomic analysis (Riner, 2007).
Further Questions for Consideration
Are there any other possible treatments or preventatives for cyclosporiasis? Are they necessary, or should this be treated like Norovirus or other gastrointestinal “bugs”?
What are cyclosporiasis’ impacts in third-world countries and how can we more effectively understand them, especially since cyclosporiasis is a neglected disease?
References
Almeria S, Cinar HN, Dubey JP. Cyclospora cayetanensis and Cyclosporiasis: An Update. Microorganisms. 2019; 7(9):317. [accessed 2023 Feb 23].
This source is from a medical/scientific journal and provides detailed information about the pathogen that causes cyclosporiasis, as well as epidemiological information about who it affects and why. This source in particular delves into how the pathogen reproduces and how outbreaks are increasing in developed countries despite hygiene and food safety practices.
Cama, Vitaliano A. Ortega, Ynes R. Cyclospora cayetanensis, Reference Module in Food Science, Elsevier, 2023, ISBN 9780081005965,
(https://www.sciencedirect.com/science/article/pii/B978012822521900054X) This is a recent source from a reference collection for food science, and provides an in-depth and comprehensive “index” of sorts about C. cayetanensis, including control, detection, epidemiology, treatment, and genotyping.
CDC. Domestically Acquired Cases of Cyclosporiasis — United States, May–August 2022. 2022 Oct 20. CDC; [accessed 2023 Feb 23].
https://www.cdc.gov/parasites/cyclosporiasis/outbreaks/2022/seasonal/index.html This source talks about the specific outbreak of cyclosporiasis from May to August and comes from an official US government website. It includes graphs and previous updates about the outbreak, and will provide me with a general overview of the outbreak as well as links leading to more specific details.
FDA. 2022 Jul 25. FDA Shares Updates on Cyclospora Prevention and Research Efforts. FDA; [accessed 2023 Feb 23].
https://www.fda.gov/food/cfsan-constituent-updates/fda-shares-updates-cyclospora prevention-and-research-efforts
This source is from the official government organisation of the FDA, and is an overview of the agency’s guidelines and updates on preventing cyclosporiasis, which is a foodborne illness. This source also features several links to follow to other official government websites or otherwise accredited sources.
Giangaspero A, Gasser RB. Human cyclosporiasis. The Lancet Infectious Diseases. 2019;19(7).[accessed 2023 Feb 23]. https://doi.org/10.1016/S1473-3099(18)30789-8 This source is from a medical journal and discusses how cyclosporiasis in particular is a neglected disease in developing and developed countries. It discusses the biological aspects of
the pathogen(s), including non-human hosts, and looks at the progress in sequencing its genome as a way to test for and prevent further outbreaks and infections.
Riner, Diana K. Mullin, Andrew S. et al. Enhanced concentration and isolation of Cyclospora cayetanensis oocysts from human fecal samples, Journal of Microbiological Methods, Volume 71, Issue 1, 2007, Pages 75-77, ISSN 0167-7012,
(https://www.sciencedirect.com/science/article/pii/S0167701207002503)
This source is from a medical journal focusing on microbiological methods, and details methods of testing for and sampling C. cayetanesis oocysts from faecal samples. The process detailed within this article leads to greater recovery of oocysts, which makes diagnosis of cyclosporiasis easier. It also features a comparative chart with different solutions used to recover oocysts.
Strausbaugh, Larry J. Herwaldt, Barbara L. Cyclospora cayetanensis: A Review, Focusing on the Outbreaks of Cyclosporiasis in the 1990s. Clinical Infectious Diseases. 2000; 4 (1040-1057). [accessed 2023 Feb 23]. https://doi.org/10.1086/314051
This is an older source from a medical journal and is a retrospective on the cyclosporiasis outbreaks of the 1990s. In conjunction with other, more recent sources, this can help understand how testing and prevention has changed from the past, and if there are any particular advances that were more effective than others.
News Desk. 2022 Jul 11. Non-travel methods investigated as mystery Cyclospora outbreak spreads to Canada. Food Safety News. [accessed 2022 Feb 22]. https://www.foodsafetynews.com/2022/07/non-travel-methods-investigated-as-myst ery-cyclospora-outbreak-spreads-to-canada/
This is an article from a news outlet focused on food safety, with the article itself focusing on how a mystery outbreak of cyclosporiasis has potentially spread to Canada and how officials are responding.
Ortega Ynés R. Robertson, L. J. (2017). Cyclospora cayetanensis as a foodborne pathogen. Springer. This is a book that provides a comprehensive overview of cyclosporiasis and provides information about documented outbreaks, regional patterns, and statistics. It also provides information about possible future challenges in regards to cyclosporiasis.