Microscopy detection and genotyping of intestinal parasites in schoolchildren of Corinto (Chinandega, Nicaragua): A cross-sectional study

Authors: COMAS, JACKLYN - University Of Valencia; PAVON, ALEYDA - National Autonomous University Of Nicaragua Unan At Leon; DASHTI, ALEJANDRO - National Center For Microbiology, The Institute Of Health Carlos Iii; KOSTER, PAMELA - National Center For Microbiology, The Institute Of Health Carlos Iii; SANCHEZ, SERGIO - National Center For Microbiology, The Institute Of Health Carlos Iii; Santin, Monica; TOLEDO, RAFAEL - University Of Valencia; ESTEBAN, JOSE - University Of Valencia; CARMENA, DAVID - National Center For Microbiology, The Institute Of Health Carlos Iii; MUNOZ-ANTOLI, CARLA - University Of Valencia

Submitted to: Journal of Parasitic Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/8/2025
Publication Date: 12/20/2025
Citation: Comas-Murillo, J., Pavon, A., Dashti, A., Koster, P.C., Sanchez, S., Santin, M., Toledo, R., Esteban, J.G., Carmena, D., Munoz-Antoli, C. 2025. Microscopy detection and genotyping of intestinal parasites in schoolchildren of Corinto (Chinandega, Nicaragua): a cross-sectional study. Journal of Parasitic Diseases. https://doi.org/10.1007/s12639-025-01893-1.
DOI: https://doi.org/10.1007/s12639-025-01893-1

Interpretive Summary: Food and waterborne pathogens responsible for diarrheal illness cause significant morbidity and mortality in low- and middle-income countries, including those in Central America. Surveys investigating the occurrence and molecular diversity of these pathogens are needed to fully understand their epidemiology and public health impact in endemic areas. In this study, microscopy was used to determine the occurrence of intestinal protist and helminth parasites in apparently healthy children in Nicaragua. Molecular (PCR and Sanger sequencing) methods were used for genotyping purposes. Over 70% of the children were positive to at least one parasite species. Blastocystis was the most prevalent intestinal protist parasite found followed by Giardia duodenalis, Endolimax nana, and Entamoeba coli. The helminths, Trichuris trichiura and Ascaris lumbricoides. Moleclar analysis identified, four subtypes of Blastocystis (ST1, ST2, ST3, and ST7); two assemblages for G. duodenalis (A and B); and one species of Cryptosporidium (Cryptosporidium hominis). These findings underscore the urgent need for sustainable public health interventions to address the burden of parasitic infections in the region. Further surveillance studies are essential to accurately assess the true impact of these diseases. This information will be useful to other scientists, medical professionals, veterinarians, and public health agencies to better understand transmission, zoonotic potential, and public health importance of diarrhoea-causing intestinal protists.

Technical Abstract: Background: Intestinal parasitic infections cause significant morbidity and mortality in low- and middle-income countries, including those in Central America and the Caribbean. Surveys investigating the occurrence and molecular diversity of these pathogens are needed to fully understand their epidemiology and public health impact in endemic areas. Methods: This is a prospective cross-sectional study assessing the prevalence of intestinal protist and helminth parasites in apparently healthy children (1'13 years) in Corinto Municipality (Chinandega Department, Nicaragua) during January 2023. We collected single stool samples (n = 88) and epidemiological questionnaires on demographics, behavioural habits, drinking water and toilet access from participating children. Microscopy (Kato-Katz, modified formalin/ethyl acetate concentration, and modified Ziehl-Neelsen) methods were used for the initial screening of the samples. Molecular (PCR and Sanger sequencing) methods were used in selected samples for confirmatory and genotyping purposes. Basic statistical analyses were carried out to assess the association of the gathered variables with an increased likelihood of infection by the investigated intestinal parasites. Results: Among protists, Blastocystis was the most prevalent intestinal parasite found (30.7%, 95% CI: 21.3–41.4), followed by Giardia duodenalis (22.7%, 95% CI: 14.5–32.9), Endolimax nana (20.5%, 95% CI: 12.6–30.4), and the commensal Entamoeba coli (18.2%, 95% CI: 10.8–27.8). Other protists including Entamoeba hartmanni, Entamoeba dispar, Chilomastix mesnili, Cryptosporidium spp., and Dientamoeba fragilis were identified at prevalences lower than 5%. Cystoisospora belli, Entamoeba histolytica, and the microsporidia Enterocytozoon bieneusi and Encephalitozoon spp. were not detected. Among helminths, Trichuris trichiura was more prevalently found (14.8%, 95% CI: 8.1–23.9) than Ascaris lumbricoides (2.3%, 95% CI: 0.3–8.0). Molecular analyses revealed the presence of subtypes ST1 (60.9%), ST2 and ST3 (17.4% each), and ST7 (4.3%) within Blastocystis, and assemblages B (60.0%) and A (40.0%) within G. duodenalis. Cryptosporidium hominis was identified in one of the two Cryptosporidium-positive samples. Conclusions: Intestinal parasite infections remain a major public health concern in Nicaragua despite previous efforts to reduce their impact, such as mass anthelmintic administration interventions. The burden of these diseases underscores the need for sustainable public health interventions and targeted investment, measures that can make a significant impact on the health status and wellbeing of the affected communities.