Functional illiteracy burden in soil-transmitted helminth (STH) endemic regions of the Philippines: An ecological study and geographical prediction for 2017.

Background Soil-transmitted helminth (STH) infections remain highly endemic across the Philippines, and are believed to be important contributors to delayed cognitive development of school-aged children. Identification of communities where children are at risk of functional illiteracy is important for the attainment of Sustainable Development Goals target for literacy. We aimed to quantify the associations between the spatial variation of STH infections and functional literacy indicators adjusting for other important contributors, and identify priority areas in the Philippines in need of interventions. Methodology/Principal findings We used data from 11,313 school-aged children on functional literacy indicators collected in 2008. Nested fixed-effects multinomial regression models were built to determine associations between STH endemicity and geographical distribution of functional literacy, adjusting for demographics, household level variables, and the prevalence of malaria. Bayesian multinomial geostatistical models were built to geographically predict the prevalence of each level of functional literacy. The number of school-aged children belonging to each of the functional literacy indicator classes was forecast for 2017. We estimated 4.20% of functional illiteracy burden among school-aged children in Mindanao might be averted by preventing T. trichiura infections. Areas predicted with the highest prevalence of functional illiteracy were observed in localised areas of the eastern region of the Visayas, and the south-eastern portion of Mindanao. Conclusions/Significance The study demonstrates significant geographical variation in burden of functional illiteracy in school-aged children associated with STH infections suggesting that targeted helminth control could potentially promote the development of cognitive function of school-aged children in the Philippines. The benefits of a spatially targeted strategy should be tested by future studies. Author summary While previous studies in the Philippines indicated an association between STH infection and cognitive development measured by memory and school performance, the contribution of STH infections on the overall functional illiteracy burden in the Philippines is unknown. This study presents the first use of geographical risk models of functional literacy adjusted for a wide array of probable confounders to uncover the associations with STH infections. This study also explores how the application of spatial epidemiology in mapping functional illiteracy provides an evaluation-planning tool for the design and implementation of STH-associated morbidity control intervention strategies, estimating the number of school-aged children with functional illiteracy associated with STH infections, and the number of interventions needed in the Philippines.