This image is of the malaria life cycle and the sites of action of recommended chemoprophylactic drugs. The diagram depicts three cycles, two that take place in the human host and one that takes place in the mosquito host. There are 12 sequential stages shown across the three cycles with arrows indicating direction.
The first cycle is the Exo-erythocytic cycle or human liver stages. First, a malaria-infected female anopheline mosquito takes a blood meal from a human and inoculates sporozoites into the human host. The diagram displays the letter “i” in this first step to indicate that this is the infective stage of malaria. Second, the sporozoites infect liver cells. Third, the infected liver cells mature into schizonts. Fourth, the schizonts rupture and release merozoites.
This leads into the second cycle, the erythrocytic cycle or human blood stages. In the fifth step of the life cycle, the merozoites infect red blood cells. Six, the ring stage trophozoites mature into schizonts, which rupture releasing merozoites. Seventh, some parasites differentiate into sexual erythrocytic stages (gametocytes). The diagram displays the letter “d” during the human blood stage, or erythocytic cycle, to indicate that this is the diagnostic stage of malaria.
This leads into the third cycle, the sporogonic cycle or mosquito stages. In the eighth step of the life cycle, an anopheles mosquito takes a blood meal from a human host and ingests the gametocyctes. Ninth, the microgametes enter the macrogametes. Tenth, this generates zygotes, which become ookinetes. Eleventh, the ookinetes develop into oocysts. Twelfth, the oocysts rupture and release sporozoites, which brings the cycle back to the first step of the life cycle where the mosquito infects a human host by taking a blood meal.
The diagram also depicts which drugs are appropriate for each stage of the malaria life cycle. In the human liver stage, atovaquone/proguanil and primaquine can be used. In the human blood stages, chloroquine, doxycycline and mefloquine can be used. In the mosquito stage, primaquine can be used. Refer to the following text for a further description of the drugs used.