Life cycle stages of Plasmodium falciparum, the agent of Malaria tropica. 1 The female? Anopheles injects sporozoites which enter liver cells via the bloodstream. 2, 3 Schizonts develop numerous merozoites (3) which after rupture of the host cell leave the liver and enter erythrocytes. 4 Merozoite directly after penetration (so-called signet-ring stage) ± this stage is very small (1/5 of the red blood cell's diameter) and is the only stage found in blood cell smears of patients. 5±8 Schizonts, which are blocked within capillaries (e.g. of the brain), give rise to several merozoites (6) which invade other red blood cells and again become schizonts (5) or develop into male or female banana-shaped gamonts (7 a,b) which are taken up by another engorging mosquito (8). 9±16 the processes in the mosquito are described in Fig. 2. E, erythrocyte; H, skin surface; N, nucleus; NH, nucleus of host cell; PV,?parasitophorous vacuole; R, remnants of the erythrocyte.
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