Erythrocytic Phase: Released merozoites invade red blood cells (erythrocytes), where they develop into trophozoites. After a period of growth, the trophozoites divide and develop, eventually forming 8-24 merozoites in each red blood cell. When this process is complete, the host red blood cells rupture, releasing mature merozoites. The symptoms associated with malaria occur at this
point. The merozoites then invade fresh erythrocytes and another generation of parasites develops in the same manner. This process occurs repeatedly during the course of infection and is called eryrthrocytic schizogony. The length of this development cycle differs according to the species of parasite, varying from 48 hours in vivax, ovale, and falciparum malaria, to 72 hours in P. malariae infections. In the early stages of infection there is no characteristic periodicity as groups of parasites develop at different times. The febrile episodes
caused are inconsistent. Later, the erythrocytic schizogony development cycle becomes synchronized, and the febrile paroxysms become more consistent. Some merozoites differentiate into sexual forms (female macrogametocytes, male microgametocytes) and develop in invaded red blood cells.
point. The merozoites then invade fresh erythrocytes and another generation of parasites develops in the same manner. This process occurs repeatedly during the course of infection and is called eryrthrocytic schizogony. The length of this development cycle differs according to the species of parasite, varying from 48 hours in vivax, ovale, and falciparum malaria, to 72 hours in P. malariae infections. In the early stages of infection there is no characteristic periodicity as groups of parasites develop at different times. The febrile episodes
caused are inconsistent. Later, the erythrocytic schizogony development cycle becomes synchronized, and the febrile paroxysms become more consistent. Some merozoites differentiate into sexual forms (female macrogametocytes, male microgametocytes) and develop in invaded red blood cells.
Vector Phase: Anopheles mosquitoes feeding on infected hosts ingest sexual forms developing in red blood cells. The 7 female macrogametocytes and male microgametocytes mature in the mosquito’s stomach and combine forming a zygote that undergoes mitosis. The products of mitosis are ookinetes, which force themselves between the epithelial cells to the outer surface of the stomach, and form into small spheres called oocysts. The oocysts enlarge as the nucleus divides, eventually rupturing and releasingthousands of motile sporozoites into the body cavity. The sporozoites migrate to the salivary glands, making the female mosquito infective.
The vector phase of the life cycle, called sporogony, is complete in 8 to 35 days depending on species and environmental conditions.
The vector phase of the life cycle, called sporogony, is complete in 8 to 35 days depending on species and environmental conditions.
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