Urogenital Schistosomiasis Among Pre-School and School-Age Children During a Community-Based Control Programme in the Lake Chad Basin: Implications for Preventive Chemotherapy and Integrated Control

Background Urogenital schistosomiasis control programmes have traditionally focused preventive chemotherapy (PC) on school-aged children (SAC, 5 -14 years). However, the burden of infection among pre-school-aged children (Pre-SAC) and the extent to which infection patterns differ from those of adults remain poorly documented in the Lake Chad Basin. This study presents a secondary analysis of routinely collected programme data from the Dawa Mobile Health schistosomiasis control programme to characterise the burden, age distribution, and determinants of urogenital schistosomiasis among children and adolescents (1 - 20 years) in the Ngouri Health District, Chad. Methods We conducted a retrospective cross-sectional secondary analysis of routinely collected data collected during a community-based schistosomiasis control programme implemented in the Ngouri Health District, Lac Province, Chad, between February 2024 and April 2025. All individuals screened during routine programme activities were eligible for inclusion. Children and adolescents aged 1- 20 years (n = 1,946) constituted the primary population of interest, while adults aged [≥]21 years (n = 2,570) served as a comparison group. Urogenital schistosomiasis was diagnosed by urine membrane filtration, with infection defined as the detection of at least one Schistosoma haematobium egg per 10 mL of urine. Multivariable logistic regression was used to identify factors independently associated with infection among children and adolescents. Results Among 4,516 programme participants, children and adolescents represented 43.1% of those screened and accounted for 43.9% of the 880 confirmed infections. During programme implementation, the observed prevalence was 19.8% (95% CI: 18.1 - 21.7%) among children and adolescents, 18.2% (95% CI: 14.7 - 22.2%) among Pre-SAC (1 - 10 years), and 20.3% (95% CI: 18.3 - 22.4%) among SAC (11 - 20 years), with no significant difference compared with adults (19.2%; p = 0.633). Both child age groups remained within the WHO moderate-endemicity category, indicating continued eligibility for annual preventive chemotherapy. In multivariable analysis, neither age subgroup, sex, education level nor occupation was independently associated with infection (all p > 0.05), suggesting broadly distributed community exposure. Conclusions Pre-school-aged children experienced a burden of urogenital schistosomiasis comparable to that of school-aged children and adults in this agro-pastoral setting. Although the reported prevalence reflects infection observed during programme implementation rather than baseline district prevalence, moderate endemicity persisted after 15 months of community-based screening and treatment, supporting the continuation of community-wide preventive chemotherapy, including Pre-SAC. These findings also suggest that chemotherapy alone may be insufficient to interrupt transmission and highlight the need to complement treatment with strengthened WASH interventions and adaptive surveillance strategies capable of identifying persistent transmission hotspots. Keywords: Schistosoma haematobium; urogenital schistosomiasis; pre-school-aged children; school-aged children; preventive chemotherapy; mass drug administration; community-based control; Lake Chad; Chad; Dawa Mobile Health.