Anti-plasmodial Property Of Moringa Oleifera Seed Extract On Swiss Mice

Figure 2.1 Life Cycles of Malaria Parasites (WHO, 2013).
Over a period of 7–12 days, the sporozoites grow in to schizonts and can develop up to 30,000 merozoites, which rupture the hepatocytes (WHO, 2013; Ricardo et al., 2014). Alternatively, some vivax and ovale sporozoites turn into hypnozoites, a form that can remain dormant in the liver for months or years and cause relapses in infected people (Greenwood et al., 2005; Walker et al., 2010). Interestingly, recurrence of falciparum malaria was reported in patients some years after leaving an endemic area. It tells that at least occasionally falciparum has a dormant stage (Greenwood et al. 2008; Szmitko et al., 2008; Theunissen et al., 2009; Poilane et al., 2009). Then, the asexual erythrocyte cycle begins, with the merozoites invading the RBC to grow by consuming hemoglobin. The parasites can multiply 10 times every 2 days, destroying RBCs and infecting new cells throughout the body. Within the host RBC, the parasite undergoes development from the early ring stage to late trophozoite and then, after mitotic divisions, to the schizont stage, which contains 6–32 merozoites, depending on the parasite species (UNICEF, 2000; Jiraprapa, 2002). When the erythrocytic schizont ruptures, the released merozoites continue the life cycle by invading other RBCs until it is brought under control. Cyclical fevers are typically happening shortly before or at the time of RBC lysis as schizonts rupture to release new infectious merozoites. This occurs every 48 h in tertian malaria (vivax, ovale and falciparum), and every 72 h in quartan malaria (malariae) infection. During this repeated cycle, some merozoites differentiate into male and female sexual forms known aserythrocytic gametocytes with one nucleus and then awaiting the arrival of a blood-seeking female Anopheles mosquito (Jiraprapa, 2002; NIAID, 2007). Intake of gametocytes by the mosquito induces gametogenesis. The flagellated forms of microgametes, formed by a process known as exflagellation, penetrate or fertilize the macrogametes generating zygotes. The zygotes changed into ookinetes and then become a round oocyst. Inside the oocyst, the nucleus divides repeatedly, with the formation of a large number of sporozoites and enlargement of the oocyst. The time necessary for the development of the sporozoites is about 8–15 days (WHO, 2013).