Seasonal population dynamics and microhabitat determinants of Oncomelania hupensis lindoensis in cocoa plantations and rice paddies in Central Sulawesi, Indonesia: Implications for precision snail control

Vollständiger Abstract

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Background and Aim: Schistosomiasis japonica remains endemic in Central Sulawesi, Indonesia, despite sustained control efforts. Oncomelania hupensis lindoensis, the sole intermediate host of Schistosoma japonicum in Indonesia, persists in agricultural environments where ecological conditions may influence transmission. However, longitudinal evidence on its seasonal population dynamics and microhabitat determinants remains limited. This study aimed to characterize seasonal changes in O. h. lindoensis populations and identify habitat and environmental factors associated with snail abundance in cocoa plantations and rice paddies in Napu Valley, Central Sulawesi. Materials and Methods: A 12-month longitudinal observational study was conducted from January to December 2025 in four villages in Napu Valley. Cocoa plantations and rice paddies were each stratified into three habitat subtypes, with six sampling points per subtype, yielding 36 sampling sites. Snail populations were monitored monthly, and environmental parameters, including air, water, and soil temperatures, relative humidity, rainfall, water pH, and soil pH, were recorded. Vegetation and diatom communities were characterized using the Shannon–Wiener diversity index. Collected snails were examined for S. japonicum cercariae. Associations between snail density and environmental variables were evaluated statistically. Results: Snail density increased from January, peaked in June, and subsequently declined in both habitat types. Cocoa plantations supported higher densities during January–June, whereas rice paddies had comparatively higher densities during July–December. Snail density differed significantly among cocoa plantation subtypes (Kruskal–Wallis H = 13.84, p < 0.001), with higher populations in habitats characterized by moderate vegetation cover and stable water sources; no significant difference occurred among rice paddy subtypes (p = 0.270). Cocoa plantations showed greater vegetation (1.82 vs. 1.67) and diatom (1.95 vs. 1.68) diversity. None of the measured climatic variables was significantly correlated with snail density (all p > 0.05). Among 2,847 examined snails, 68 were cercaria-positive (2.39%), with the highest infection rate recorded in June (4.12%). Conclusion: O. h. lindoensis populations exhibit distinct seasonal and habitat-specific dynamics in Napu Valley. The concurrence of peak snail density and cercarial infection in June identifies a critical period for intensified surveillance, while persistence across both agricultural habitats supports integrated, habitat-targeted environmental management. These findings provide an ecological basis for more precisely timed snail control within One Health-oriented schistosomiasis elimination programs in Indonesia. Keywords: cercarial infection, habitat ecology, Oncomelania hupensis lindoensis, One Health, population dynamics, Schistosoma japonicum, schistosomiasis, snail control.