Figure 5

Life cycle of Plasmodium falciparum. The human host harbouring sexually immature parasite is marked using red arrows. Here the parasite multiplies asexually in the liver (exoerythrocytic schizogony) and in red blood cells (erythrocytic schizogony). The sporozoites that invade the liver become trophozoites, divide and develop into a liver schizont. These contain thousands of nuclei. The resulting merozoites infect blood cells and turn into trophozoites. These develop into schizonts with 8–32 nuclei which are released when the erythrocytes burst and can re-infect new erythrocytes. Erythrocytes that contain other stages stick to the endothelial cells of the blood capillaries, escaping destruction in the spleen, allowing gametocytes to be produced. The cycle in the mosquito which harbours sexually mature parasites is shown in blue. Here the sexually differentiated gametocytes change into gametes in the mosquito's gut, where fertilisation of the macrogamete occurs. Large oocysts, containing up to 10,000 sporozoites, develop on the outer surface of the gut wall. When they burst the sporozoites enter the mosquito's hemolymph, and ultimately reach the salivary glands.