Malaria parasite in red blood cell. Light micrograph of a red blood cell (erythrocyte) infected with a Plasmodim vivax protozoan. This parasite causes recurring malaria in humans. This is the mature schizont stage of the protozoan's life cycle, during which it reproduces asexually. New merozoites, which when released will further develop into male and female gametocytes, are seen in the cell. P. vivax is transmitted to humans via the bite of an infected female Anopheles sp. mosquito. Symptoms include fever and headache, which can proceed to coma and death. Wright's stain.