Geostatistical analysis to guide treatment decisions for soil-transmitted helminthiasis control in Uganda

Soil-transmitted helminth (STH) infections remain a public health problem in Uganda despite biannual national deworming campaigns implemented since the early 2000s. Recent surveys have indicated a heterogeneous STH infection prevalence, suggesting that the current blanket deworming strategy may no longer be cost-effective. This study identified infection predictors, estimated the geographic distribution of STH infection prevalence by species, and calculated deworming needs for school-age children (SAC).

Bayesian geostatistical models were applied to STH survey data (2021-2023) for each species (i.e., Ascaris lumbricoides, hookworm, and Trichuris trichiura). Climatic, environmental, and socioeconomic predictors were obtained from remote sensing sources, model-based databases, and demographic and health surveys. Prevalence was predicted on a 1 × 1 km2 grid across Uganda, and district-level estimates were used to classify each district into treatment frequency categories and to determine its deworming tablet requirements.

The national prevalence of A. lumbricoides, T. trichiura, and hookworm was estimated at 5.0% (95% Bayesian credible interval [BCI]: 0.8-11.8%), 3.5% (0.7-9.3%), and 7.2% (5.7-11.1%), respectively. The overall prevalence of any STH infection was 14.3% (9.6-21.8%). High intra-district variation in prevalence was observed. Of 146 implementation units (136 districts and 10 cities), 49 require twice-year treatment, 34 once-yearly treatment, 61 every other year treatment, and 2 had a prevalence <2%, indicating treatment suspension or event-based treatment. Approximately 17 million tablets will be needed for preventive chemotherapy aimed at SAC in 2025.

The prevalence of STH infection has declined considerably across Uganda compared to the early 2000s. However, deworming needs remain heterogeneous across districts. Through geostatistical modeling, districts were classified according to the latest World Health Organization's (WHO) treatment guidelines. This approach optimizes treatment distribution and allows for prioritization of populations with the greatest needs. We estimated that tablet requirements are approximately 40% lower compared to the current twice-a-year deworming regimen, which contributes towards WHO's goal of halving the number of tablets required for preventive chemotherapy by 2030.