Prevalence and associated risk factors of intestinal parasites among schoolchildren in rural Ecuador, with emphasis on the molecular diversity of Giardia duodenalis, Blastocystis sp. and Enterocytozoon bieneusi

Authors: TAPIA-VELOZ, ESTEPHANY - University Of Valencia; GOZALBO, MONICA - University Of Valencia; GUILLEN, MARISA - University Of Valencia; DASHTI, ALEJANDRO - Instituto De Salud Carlos Iii; BAILO, BEGOÑA - Instituto De Salud Carlos Iii; KOSTER, PAMELA - Instituto De Salud Carlos Iii; Santin-Duran, Monica; CARMENA, DAVID - Instituto De Salud Carlos Iii; TRELIS, MARIA - University Of Valencia

Submitted to: PLOS Neglected Tropical Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/27/2023
Publication Date: 5/24/2023
Citation: Tapia-Veloz, E., Gozalbo, M., Guillen, M., Dashti, A., Bailo, B., Koster, P.C., Santin, M., Carmena, D., Trelis, M. 2023. Prevalence and associated risk factors of intestinal parasites among schoolchildren in rural Ecuador, with emphasis on the molecular diversity of Giardia duodenalis, Blastocystis sp. and Enterocytozoon bieneusi. PLOS Neglected Tropical Diseases. 17(5). Article e0011339. https://doi.org/10.1371/journal.pntd.0011339.
DOI: https://doi.org/10.1371/journal.pntd.0011339

Interpretive Summary: Intestinal parasitic infections remain a public health concern in poor-resource areas in Ecuador, primarily affecting pediatric populations. Our results indicate that mass drug administration programs targeting intestinal helminths, including soil-transmitted helminth, are insufficient to effectively control the spreading and perpetuation of these pathogens in deprived communities. These interventions must be complemented with measures directed to improve household quality and living conditions, sanitation, and health education for schoolchildren and their families. Together with access to safe drinking water, these measures are necessary to reduce infections with soil-transmitted helminth and gastrointestinal protists in poor communities in Ecuador. Under the One Health approach, more research should be conducted to ascertain to which extent the animal reservoirs (livestock, wildlife) and contaminated environmental (water, soil, grass) contribute to the burden of human disease caused by intestinal parasites. Data presented here expand our knowledge on the epidemiology and risk factor associated with parasite transmission that will be useful to other scientists, and public health agencies in understanding epidemiology of gastrointestinal parasites.

Technical Abstract: Background Intestinal helminths, including Soil-Transmitted Helminth (STH), and Gastrointestinal Protist (GP) infections are major contributors to the global burden of disease, particularly in low-income countries such Ecuador. Their epidemiology in these settings is largely unknown. Methodology This prospective cross-sectional study investigates the carriage of intestinal helminths, including STH, and GP in asymptomatic schoolchildren (3'11 years) in the Chimborazo and Guayas provinces, Ecuador. Single stool samples (n = 372) and epidemiological questionnaires on demographics and potential risk factors were collected from participating schoolchildren. Conventional microscopy examination was used as screening method, and molecular (PCR and Sanger sequencing) assays were used to further investigate the epidemiology of some GP. A multivariate logistic regression analysis was used to evaluate the strength of the association of suspected risk factors with the presence of helminths and GP. Principal Findings At least one intestinal parasite species was observed by microscopy in 63.2% (235/372) of the participating schoolchildren. Enterobius vermicularis (16.7%, 62/372; 95% CI: 13.0–20.9) and Blastocystis sp. (39.2%, 146/372; 95% CI: 34.2–44.2) were the most prevalent among helminths and GP, respectively. Assemblages A (50.0%), B (37.5%) and A+B (12.5%) were detected within Giardia duodenalis and ST3 (28.6%), ST1 and ST2 (26.2% each), and ST4 (14.3%) within Blastocystis sp. Three genotypes, two known (A: 66.7%; KB-1: 16.7%) and a novel (HhEcEb1, 16.7%) were identified within Enterocytozoon bieneusi. Municipality of origin, household overcrowding, and poor sanitation and personal hygiene habits were risk factors for childhood intestinal parasites colonization. Conclusions/Significance Despite massive government drug administration programs, STH and GP infection remain a public health concern in paediatric populations living in poor-resource settings. Molecular analytical methods are required to better understand the epidemiology of these intestinal parasites. This study provides novel information on the occurrence of Blastocystis sp. and E. bieneusi genetic variants circulating in Ecuadorian human populations.