Mathematical modeling of control strategies for the elimination of soil-transmitted helminthiases in Thailand

Soil-transmitted helminthiases, caused by soil-transmitted helminths (commonly known as intestinal worms), are considered to be neglected tropical diseases (NTDs). In Thailand, school-age children (SAC) who live in remote areas are at risk of STH. A school-based combined intervention involving test and treat (TnT) and mass drug administration (MDA) programs has been implemented as part of the national STH control program since 2002, with a target to eliminate STH in SAC by 2026. To help achieve this target, we developed an STH transmission dynamic model, calibrated it using STH infection prevalence data from Thailand, and used the model to simulate the effects of the current intervention targeting only SAC and expanded interventions that also cover preschool-age children (PSAC) and adults. We also investigated modified interventions, including biannual MDA and TnT. Our model predicted that neither the current nor a biannual TnT can achieve elimination, even with expanded target populations. However, all biannual MDA treatment scenarios showed a reduced prevalence of STH in SAC, of less than 5%, by 2026. Our model also predicted that biannual MDA targeting SAC and adults would be more effective than targeting SAC and PSAC. Our findings suggest that if community-wide biannual MDA treatment were to be included in the control program, this would be beneficial for eliminating STH in Thailand.