Schistosomiasis parasite enhance transmission rates via interfacial swimming

Authors: Melanie Hannebelle, Ian Ho, Alassane N’diaye, Manu Prakash

Link: https://www.biorxiv.org/content/10.1101/2025.05.13.653683v1.abstract

Abstract: Schistosomiasis is a disease of poverty that affects over 240 million people worldwide despite an ecological paradox: cercariae larvae are short-lived (12 hours), sparse in the water body, and entrained by flows exceeding their swimming speeds - conditions that should limit host-finding. We resolve this paradox by demonstrating that cercariae utilize a physics-based strategy: they actively accumulate at the air-water interface, transforming inefficient three-dimensional search into effective two-dimensional exploration, increasing host-encounter efficiency by a thousand fold. Our biophysical models demonstrate that this behavior emerges from weight-asymmetric morphology, enabling an embodied algorithm for surface-seeking swimming modes without complex neural control. Surface-swimming cercariae benefit from near-zero vertical flows near the surface, allowing them to remain there while exploiting wind-driven currents for long-distance dispersal. We identify the air-water interface as a critical transmission micro-habitat, suggesting new physical intervention strategies targeting this interface to mitigate transmission of this highly infectious disease.