Malarial blood cell. Coloured scanning electron micrograph (SEM) of a freeze fractured red blood cell (erythrocyte, brown) infected with a Plasmodium falciparum protozoan (red). This is the merozoite stage of the protozoan parasite. It invades red blood cells after the sporozoite stage is injected into the blood by an Anopheles mosquito. The merozoites replicate and destroy the red blood cell, causing anaemia. They may then invade more red blood cells, causing the severe cyclic fevers of malaria. The infected red blood cells are misshapen and can clot to block blood vessels.