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Abstract

The malaria disease is transmitted by a unicellular parasite that heavily relies on motility throughout its life cycle. We present different modelling approaches to the migration of the most motile form of the malaria parasite, the sporozoite, which is injected into the host skin by a mosquito. Their bent, elongated geometry shapes their trajectories. We first develop a geometrical model for the migration of a single sporozoite in the presence of obstacles. This enables us to trace the complex trajectories observed in vivo back to the structural features of both parasite and environment. Our second model shows that sporozoites can collectively organise in stable whirl-like structures, as observed experimentally in the salivary glands of malaria-infected mosquitos. Thirdly, we adopt a microscopic viewpoint linking the experimentally observed adhesion dynamics of gliding sporozoites with the presence of translational and rotational stochastic friction. Finally, we connect the propulsion system of sporozoites with mechanical cell deformations. Analysing experimental time series of sporozoite speed and curvature we can quantitatively distinguish the components of the gliding machinery. Overall, our physical models explain many essential features of gliding sporozoites and provide predictions that motivate novel experiments.