Prevalence of Schistosoma mansoni and S. haematobium in snail intermediate hosts in East Africa: a systematic review and meta-analysis of studies published between 2020 and 2025

In East Africa, schistosomiasis remains a serious neglected tropical disease transmitted by infected freshwater snails of the genera Bulinus and Biomphalaria . To direct integrated control actions in line with the WHO 2030 roadmap, current, region-specific data on the prevalence of schistosome infection in snails is crucial. A systematic review and meta-analysis were conducted following PRISMA 2020 guidelines to estimate the prevalence of Schistosoma mansoni and S. haematobium infections in intermediate host snails in East Africa. Five electronic databases were searched for studies published between January 2020 and December 2025; this window refers to the date of publication only, and the snail sampling periods of the included studies ranged from 2009 to 2025. Study-level proportions were stabilised with the Freeman-Tukey double-arcsine transformation and pooled using a DerSimonian-Laird random-effects model in Stata 17 (metaprop), with exact binomial confidence intervals for individual estimates. Subgroup analyses and meta-regression were performed to explore sources of heterogeneity by country, snail genus, parasite species, study design, diagnostic method, and publication year. Seventeen studies contributed 27 datasets, and 72,473 freshwater snails were included. The overall pooled prevalence was 8.88% (95% CI: 5.61–12.14), but heterogeneity was extreme (I²=100%, p < 0.001). Because DerSimonian-Laird weights become almost equal under such heterogeneity, this value approximates the unweighted mean of the 27 dataset proportions rather than a sample-weighted regional prevalence (crude prevalence 1,615/72,473 = 2.23%), and subgroup estimates are therefore emphasised in preference to the overall pooled figure. Infection prevalence was significantly higher in Biomphalaria snails (13.44%) than in Bulinus snails (2.24%) and for S. mansoni compared with S. haematobium ( p < 0.001). Ethiopia reported the highest pooled prevalence (16.79%). Estimates also differed by diagnostic approach, but not in the direction usually reported: cercarial shedding alone yielded 9.98% (95% CI 9.01–10.95), PCR alone 10.83% (95% CI 6.10-15.55), and shedding combined with PCR 3.35% (95% CI 1.13–5.57), and in meta-regression, PCR alone did not differ significantly from shedding alone. The PCR-alone stratum comprised four datasets from a single Ugandan study of snails collected in 2009–2010 and is fully confounded with country, host genus, and sampling period. Exploratory meta-regression identified snail genus, parasite species, country and diagnostic method as correlates of between-study variability, but residual heterogeneity remained at I²=100% in every model, so these associations are hypothesis-generating only. Infected intermediate host snails, especially Biomphalaria species that contain S. mansoni , remained infected across the East African sites covered by the included studies. Because sampling periods span 2009–2025 and are unevenly distributed across countries, host general and diagnostic methods, these estimates describe the published evidence base rather than a uniform picture of current transmission. These results highlight the critical need for coordinated site-specific strategies that combine mass medicine delivery with targeted snail removal, molecular xenomonitoring, environmental management, and sensitive snail surveillance to accomplish schistosomiasis elimination goals by 2030.