Hydropower dams as modifiers of Opisthorchiasis spread in river networks

Waterborne and water-related diseases are strongly shaped by ecohydrological and human factors that control the spatial connectivity of freshwater systems. Hydropower dams profoundly modify this connectivity, altering flow regimes, fragmenting aquatic habitats, and reshaping interactions among hosts and pathogens. Yet, the implications of dam-induced connectivity changes for disease transmission remain largely overlooked in assessments of hydropower sustainability.

Here, we investigate how hydropower infrastructure affects the transmission dynamics of Opisthorchis viverrini, a parasitic liver fluke endemic to Southeast Asia. The parasite’s complex life cycle involves freshwater snails and cyprinid migratory fish as intermediate hosts, and piscivorous mammals, including humans, as definitive hosts. Because all hosts depend on aquatic habitats and disperse through river networks, alterations of hydrological connectivity can fundamentally reshape transmission pathways.

We extended a spatially explicit metacommunity model of O. viverrini transmission to include the effects of dams on fish movement and snail habitat availability within a realistic river network. Dams reduce fish migration and fragment river corridors, limiting parasite dispersal, while reservoirs create favorable conditions for snail proliferation that may enhance local transmission. Using Monte Carlo simulations, we vary both the location of the initial infection and the fish passability of existing dams to explore the trade-offs between restoring river connectivity for ecosystem conservation and limiting disease spread.

Our results show that the spatial configuration of dams strongly governs these dynamics. Reservoirs shape transmission pathways, creating zones where infections may either amplify or remain contained. Explicit representation of reservoirs allows identification of critical network nodes, where localized infection could trigger widespread propagation, providing a quantitative basis to prioritizing targeted monitoring, prevention, or intervention campaigns. Importantly, our analysis highlights a key trade-off: increasing dam passability  to enhance river connectivity—for example, through fish ladders—supports natural capital and biodiversity but can also weaken hydrological barriers that otherwise limit pathogen spread.

These findings illustrate how hydropower management decisions can simultaneously affect ecological integrity and human health. Incorporating disease ecology into river management and infrastructure planning is therefore essential to fully assess the trade-offs between energy production, ecosystem integrity, and human health in regulated water systems.