While one source has been identified in the cyclosporiasis outbreak in Michigan and surrounding states, the investigation is continuing as there are likely several concurrent outbreaks occurring. FDA CORE’s current outbreak table lists two other Cyclospora investigations, in addition to the outbreak associated with iceberg lettuce.
FDA’s traceback investigation of the cyclosporiasis outbreak identified a single supplier, Taylor Farms de Mexico, that provided shredded iceberg lettuce used by Taco Bell locations as well as Marketside brand shredded lettuce and iceberg salad. But a re-review of an FDA sample result that was initially positive was later determined to be a false positive.
However, with the epidemiologic and traceback data showing that the farm’s lettuce was contaminated with Cyclospora, the company has voluntarily stopped receiving product from the implicated lot, suspended distribution of the iceberg lettuce from Central Mexico, notified its customers, and is continuing to work with the FDA, CDC, and state authorities on the investigation and recall. It’s important to remember that product recently sampled by the FDA is not the same product that would have been consumed in June when the majority of the cases were exposed and subsequently became ill. This is always a challenge during traceback investigations associated with produce; often the contaminated product has been consumed and is no longer available for testing, and product that is tested later likely came from a different farm or source.
Cyclospora investigations are complex because of the unusual life cycle of Cyclospora cayetanensis, which must mature before it becomes infectious, causing a significant delay in symptom onset. Additionally, whole genome sequencing (WGS), which is typically used to investigate other outbreaks, does not work with Cyclospora, as the stool samples do not typically yield enough DNA and the parasite is difficult to culture for WGS to link cases.
TAG will continue to follow this outbreak and provide information to our TAG newsletter readers (to which you can subscribe here). For more information on cyclosporiasis and cyclospora controls, see TAG’s additional articles on:
- What Is Cyclospora and Why Is It Such a Problem?
- Grower Considerations for Cyclospora Prevention and Control
- Cyclosporiasis Fact Sheet
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