FROM THE BENCH
Piecing Together Cyclospora : A Puzzle for Public Health Labs
By M Grzywinski , Population Health Sciences Department , Virginia-Maryland College of Veterinary Medicine at Virginia Tech ; R Matheson , Population Health Sciences Department , Virginia-Maryland College of Veterinary Medicine at Virginia Tech ; JC McEntire , Food Safety Strategy ; and LK Strawn , Food Science and Technology , Virginia Tech
Figure 1 . Mapping of the farm-to-fork supply chain with potential sources of contamination and key questions addressed .
Even the most well-versed professionals in infectious disease and food safety are puzzled by Cyclospora cayetanensis . Cyclospora is a human parasite that is presumed to be spread through fecal contamination , causing diarrheal disease of varying severity . Produce like raspberries , snow peas , lettuce , cilantro and basil have been involved in outbreaks of cyclosporiasis . 1 But beyond this , there is a surprising lack of concrete understanding about this sneaky pathogen , largely because research is limited due to a lack of oocysts . Public health labs have an opportunity to help solve the Cyclospora puzzle by collecting oocysts from cases and supporting academic and federal efforts to address this pathogen .
Cyclospora outbreaks tend to follow a seasonal cycle , occurring in the summer months worldwide . 1 , 2 Historically , outbreaks in the United States have been associated with international travel or imported foods . However , in recent years , there has been an apparent increase in domestically acquired cases , likely due to advances in clinical detection . 3 Despite knowing that cases will peak between May and August , public health professionals across the US are left relatively helpless when predicting and preventing illnesses . They rely solely on passive surveillance — reported cases from clinicians and public health laboratories — to understand disease patterns due to major gaps in knowledge surrounding the transmission , life cycle , genotyping and environmental detection of Cyclospora .
For example , in 2020 , Cyclospora cases plagued the midwestern US in a multistate outbreak . Cases were concentrated in Illinois and Iowa but spread as far as Massachusetts and Georgia . The outbreak was linked back to bagged salads . The US Centers for Disease Control and Prevention ( CDC ) and the US Food and Drug Administration ( FDA ) conducted thorough traceback investigations but were unable to definitively identify the specific salad component responsible for contamination . 4
The inability to identify the specific cause of this outbreak , despite the extensive expertise and diligent efforts of epidemiologists , other public health professionals , and members of the food industry indicates how problematic this pathogen is . A host of factors could have contributed to this outbreak and there are several points along the farm-to-fork supply chain where contamination could have occurred , making it challenging to pinpoint the cause ( Figure 1 ). There is also a lack of reliable environmental sampling and real-time genotyping methods for Cyclospora , limiting the genetic linkage of clinical specimens to a specific source . 5 Additionally , the sexual reproduction of the parasite allows for rapid genetic changes that make it difficult to trace . There is simply not enough information or reliable methods available to accurately and efficiently determine the source of Cyclospora outbreaks , hindering the possibility of employing targeted prevention measures . Therefore , Cyclospora continues to arise during the US summer months , affecting large numbers of individuals and the produce supply chain before disappearing without a trace .
8 LAB MATTERS Fall 2024
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