Life Cycle of Plasmodium
When an infected female anopheles mosquito bites, the parasites are injected into the human body through the saliva of the mosquito. On an average 5 to 10 uni-nucleated sporozoites are injected. Within 30 minutes these sporozoites migrate to the liver and invade hepatocytes (liver cells) and develop into schizonts.
The schizonts multiply in the liver cells until there is no space left. Within one week of entering the liver cell, mature liver stage schizonts rupture spilling merozoites into the blood stream. Their numbers could range between 10,000 and 40,000. These merozoites in the blood stream invade circulating erythrocytes and develop into a trophozoite, secreting proteins that form knobs on the erythrocyte membrane. With the help of these knobs it attaches itself to the capillary wall affecting the microcirculation. On maturity the erythrocyte ruptures and 8 to 32 merozoites spill out from each one which in turn invade other erythrocytes which have been unaffected till now.
The entire process of the merozoite invading the erythrocyte to maturity to ultimate rupture of erythrocyte takes approximately 48 hours. This is one asexual life cycle of the schizont. The symptoms of malaria – chills – fever – sweating – along with nausea, vomiting and headache occur during the blood stage.
If left untreated it may lead to severe anaemia, convulsion, coma and ultimately death. Some erythrocytic-stage parasites develop into sexual stage parasites called gametocytes. The bite of another female anopheles mosquito takes in these gametocytes along with its blood meal and the process of transmission to another human is repeated.