Epidemiology and risk factors of soil-transmitted nematode-schistosome co-occurrence: An analysis of the global burden of disease study

Objective Soil-transmitted nematode (STN) infections and schistosomiasis frequently co-occur in endemic regions, imposing substantial combined health burdens. This study aimed to characterize the global co-occurrence patterns, long-term trajectories, and key risk factors of STN-schistosome co-occurrence using Global Burden of Disease (GBD) data. Methods We analyzed GBD 1990–2021 data from 69 countries and territories with available STN infections and schistosomiasis prevalence data. Co-occurrence patterns were classified into consistent, schistosomiasis-dominant, and STN infection-dominant regions based on global prevalence quartiles. Group-based trajectory modeling (GBTM) and similarity network clustering identified long-term evolutionary trajectories and epidemiological clusters. Negative binomial regression and population-attributable fraction (PAF) analysis quantified associations between 22 risk factors and disease burden. Results Global co-occurrence patterns remained stable over 32 years, with 68.1% of countries and territories showing concordant high or low burdens of both diseases. GBTM identified three distinct trajectories for each disease, with sub-Saharan Africa dominating high-burden groups. Similarity network clustering partitioned countries into six epidemiological clusters, ranging from persistently high co-burden to near-eliminated schistosomiasis with low STN prevalence. Key shared drivers included inadequate water, sanitation, and hygiene (WASH) factors, while nutritional deficiencies (iron deficiency, child growth failure) were specific risk factors for STN infections, particularly in co-endemic regions (PAF = 19.08% and 8.82%, respectively). Both high and low temperatures exerted protective effects against both infections. Conclusion STN-schistosome co-occurrence exhibits distinct global epidemiological clusters with heterogeneous drivers. Integrated control strategies should combine WASH improvements, preventive chemotherapy, and targeted nutritional interventions, especially in co-endemic regions, to align with the WHO 2021–2030 Neglected Tropical Diseases Roadmap and accelerate elimination efforts.