Fig. 1. : Plasmodium bottlenecks in the mosquito host. Shortly after ingesting an infectious blood meal, Plasmodium gametocytes are activated within the Anopheles midgut resulting in the emergence of male and female gametes. Following fertilisation, the resulting zygote differentiates into a motile ookinete. The ookinete must then penetrate the peritrophic matrix that completely surrounds the blood meal and invade the midgut epithelium. After traversal, ookinetes attach to the basal surface of the epithelium and differentiate into sessile oocysts that grow and produce thousands of sporozoites over an approximate two-week period. Upon maturation, sporozoites are released into the haemolymph from where they invade the salivary glands. The cycle is completed when the mosquito feeds on a new host and delivers sporozoites with the saliva. The illustration indicates development time, approximate parasite numbers during each stage of development (yellow bar) and the timing of anti-Plasmodium responses (bottom).