Evaluating short-term changes in helminth burdens using sequential community-based surveys in Rwanda

Despite sustained national mass drug administration (MDA) efforts, soil-transmitted helminths (STHs) and Schistosomiasis (SCH) remain endemic in Rwanda, suggesting that elimination requires granular planning and interventions. This study aimed to evaluate short-term changes in infection prevalence and intensity at selected sentinel sites and assess risk factors associated with persistent transmission. A community-based cross-sectional survey was conducted twelve months after a baseline survey and two rounds of national MDA. Parasitological, sociodemographic and household water, sanitation, and hygiene (WaSH) data were analysed for 2,515 participants across ecologically diverse sentinel sites. Hookworm was the most prevalent STH, particularly among adults, while Ascaris lumbricoides predominated in school-aged children. Overall hookworm prevalence declined from 12.6% to 6.6%, yet total parasite infection (PI) prevalence rose slightly from 15.0% to 17.1%. Schistosomiasis prevalence was low by microscopy but substantially higher by Circulating Cathodic Antigen (CCA). Unimproved drinking water sources, use of untreated human excreta as fertilizer, and increasing age were associated with higher odds of infection. Protective factors included adequate household water storage, longer workplace duration, and literacy. While MDA has stabilized average infection levels, persistent hotspots driven by ecological, occupational, and behavioral factors continue to undermine elimination efforts. Integrated strategies, tailored to community characteristics, are essential to interrupt transmission and advance toward national elimination goals.