A decay-adjusted spatio-temporal model to account for the impact of mass drug administration on neglected tropical disease prevalence

Abstract Prevalence surveys are routinely used to monitor the effectiveness of mass drug administration (MDA) programmes for controlling Neglected Tropical Diseases (NTDs). We propose a decay-adjusted spatio-temporal (DAST) model that explicitly accounts for the time-varying impact of MDA on NTD prevalence, providing a flexible and interpretable framework for estimating intervention effects from sparse survey data. Using case studies on soil-transmitted helminths and lymphatic filariasis, we show that DAST offers a practical alternative to standard geostatistical models when the objective includes quantifying MDA impact and supporting short-term programmatic forecasting. We also discuss extensions and identifiability challenges, advocating for data-driven parsimony over complexity in settings where the available data are too sparse to support the estimation of highly parameterized models.