Prevalence and Risk Factors of Soil-Transmitted Helminth Infections on Koh Yao Islands, Southern Thailand: A Community-Based Cross-Sectional Survey

Background: Soil-transmitted helminth (STH) infections are a recognized public health challenge, particularly in rural and island settings. Despite the implementation of national control programs, epidemiological data from geographically isolated communities remain limited. In this study, we aimed to determine the prevalence of STH infections and identify associated risk factors among adults in Koh Yao Islands, southern Thailand. Methods: A community-based cross-sectional survey was conducted in three subdistricts of Koh Yao, Phang Nga Province, from January to September 2024. Demographic data and information on potential risk factors were collected using structured questionnaires. Stool specimens were analyzed using the formalin–ethyl acetate concentration technique and the modified Kato–Katz method. Associations were assessed using univariate and multivariate logistic regression analyses. Results: A total of 241 adults participated in the study, with females accounting for 68.9% and males for 31.1%. The overall prevalence of STH infections was 2.49%, with hookworms and Trichuris trichiura identified as the predominant species. All infected individuals had an educational level lower than a bachelor’s degree. Univariate analysis showed that participants who did not use hygienic toilets at home had a significantly higher likelihood of developing STH than those who did (crude odds ratio = 46.80; 95% confidence interval [CI]: 2.55–859.00; p = 0.010). Multivariable logistic regression analysis confirmed that the absence of hygienic toilet use at home was independently associated with STH infection (adjusted odds ratio = 30.69; 95% CI: 1.17–804.65; p = 0.040). Conclusions: This study documents low overall prevalence of STH infections in the study area, with hookworms and T. trichiura as the predominant organisms. These findings support continued targeted public health measures, including periodic deworming and health education initiatives, to strengthen hygiene practices, particularly in high-risk populations. Future investigations should incorporate environmental assessments and longitudinal monitoring to evaluate the durability of current control strategies.