Retrospective evaluation of an integrated molecular-epidemiological approach to cyclosporiasis outbreak investigations – United States, 2021

Abstract

Cyclosporiasis results from an infection of the small intestine by Cyclospora parasites after ingestion of contaminated food or water, often leading to gastrointestinal distress. Recent developments in temporally linking genetically related Cyclospora isolates demonstrated effectiveness in supporting epidemiological investigations. We used ‘temporal-genetic clusters’ (TGCs) to investigate reported cyclosporiasis cases in the United States during the 2021 peak-period (1 May – 31 August 2021). Our approach split 655 genotyped isolates into 55 genetic clusters and 31 TGCs. We linked two large multi-state epidemiological clusters (Epidemiologic Cluster 1 [n = 136 cases, 54 genotyped] and Epidemiologic Cluster 2 [n = 42 cases, 15 genotyped]) to consumption of lettuce varieties; however, product traceback did not identify a specific product for either cluster due to the lack of detailed product information. To evaluate the utility of TGCs, we performed a retrospective case study comparing investigation outcomes of outbreaks first detected using epidemiological methods with those of the same outbreaks had TGCs been used to first detect them. Our study results indicate that adjustments to routine epidemiological approaches could link additional cases to epidemiological clusters of cyclosporiasis. Overall, we show that CDC’s integrated genotyping and epidemiological investigations provide valuable insights into cyclosporiasis outbreaks in the United States.

Food and Drinking Water as Sources of Pathogenic Protozoans: An Update

“…The number of cases and outbreaks of waterborne and foodborne protozoan infections published for each pathogen since 2019 are shown in Figure 2. [8,9,19,35,122,123,[131][132][133]142,143,154,157,[168][169][170]172,173,191,193,195,196,[198][199][200][201]209,226,233,237,[239][240][241][242][243]255,256,260,268,269,273,274,280,282,286]. Outbreaks are only shown for Cryptosporidium species.…”

“…In the USA, outbreaks of cyclosporiasis linked to berries, cilantro, basil, and, more recently, ready-to-eat bagged salads have been documented since the 1990s and have affected thousands of individuals annually in the past decade [237]. The first outbreak was reported in Chicago and was possibly linked to a hospital water supply [242]. From 2018 to 2022 annual summertime outbreaks became regular in people with no recent international travel history [235,243].…”

“…Ten of these were associated with epidemiological clusters. Two of these were multistate and were linked to lettuce from a single brand, and to lettuce not associated with a brand, respectively, as inferred by isolate typing and patient interviews [242].…”

Field study of parasitic contamination of fruits, vegetables and leafy greens in the Ecuadorian Andes

“…The situation is aggravated by cases of parasite resistance to certain chemical and physical inactivating agents ( Ramos et al, 2013 ). This underlines the ability of parasites to persist and survive along the food chain, facilitating their transmission to humans, even far from the site of production ( Dixon, 2016 ; Caradonna et al, 2017 ; Barlaam et al, 2021 , 2022 ; Temesgen et al 2022 ; Ahart et al, 2023 ).…”

Evaluation of the Increased Genetic Resolution and Utility for Source Tracking of a Recently Developed Method for Genotyping Cyclospora cayetanensis

“…The eight discriminatory targets, two located in the mitochondrial genome and six in the nuclear genome, were previously described [15][16][17]. The eight loci MLST genotyping scheme has been applied to fecal specimens associated with major C. cayetanensis outbreaks in the United States [18][19][20] and cyclosporiasis illnesses in Canada [21]. Although this approach has been useful, it has been recognized that the genetic discriminatory power is limited and that additional targets containing phylogenetically informative single-nucleotide polymorphisms (SNPs) are needed to better resolve genetic clusters [21][22][23].…”