Malaria:Life cycle of Plasmodium

MALARIA:LIFE CYCLE OF PLASMODIUM 1. When a female Anopheles mosquito penetrates human skin to obtain a blood meal,it injects saliva mixed with anticoagulant. 2. If the mosquito is infected with Plasmodium,it will also inject elongated sporozoites(motile,spindle-shaped asexual cells)into the blood stream of its victim. 3. The sporozoites travel to the liver where they enter liver cells and rapidly divide asexually.This asexual division,which is called schizogony,generates the next life cycle form,called merozoites. 4. The released merozoites invade other liver cells and enter the host’s bloodstream,where they invade erythrocytes. 5. Once inside the erythrocyte,the merozoite begins to enlarge as a uninucleate cell termed a ring trophozoite.The trophozoite ‘s nucleus then divides asexually to producea schizont which contains several nuclei. 6. The schizont then divides and produces mononucleated merozoites. 7. The erythrocyte ruptures and releases toxins throughout the body of the host,bringing about the well-known cycle of fever and chills that is characteristic of malaria. 8. Plasmodium enters a sexual phase when some merozoites in the erythrocytes develop into gametocytes,cells capable of producing both male and female gametes.Erythrocytes containing gametocytes do not rupture 9. Gametocytes are incapable of producing gametes within their human hosts and do so only when they are extracted from an infected human by a mosquito. 10. Within the gut of the mosquito, the gametocytes form male and female gametes. 11. The resultant diploid zygotes develop within the mosquito’s intestinal walls and ultimately differentiate into oocysts. 12. Within the oocysts,repeated mitotic divisions take place,producing large numbers of sporozoites. 13. These sporozoites migrate to the salivary glands of the mosquito, and from there are injected by the mosquito into the bloodstream of a human ,thus starting the life cycle of the parasite again. What are the different stages of the parasite's life cycle? This small single-cell organism has three to four different forms. Each form is specialised in living in a certain place.  The gametocyte is the form that infects the mosquito and reproduces itself, as if it were both sexes. When the mosquito has sucked blood containing gametocytes, these pass into the salivary glands of the mosquito, where they develop into a new form, the sporozoite. The infection can then move on. P.vivax P.falciparum  The sporozoite can be passed on to man when the mosquito bites, injecting its saliva into the tiny blood vessels. The sporozoite travels with the blood to the liver and enters the liver cells. In the liver some of the sporozoites divide (tachysporozoites) and become thousands of merozoites.  The merozoites are released from the liver to the blood where they are taken up by the red blood corpuscles. Some of these turn into ring-formed trophozoites that split again to form schizonts.  Schizonts burst the red blood corpuscles at a certain moment, releasing the merozoites. This release coincides with the violent rises in temperature during the attacks seen in malaria. Hepatic schizont is actively dividing, multinucleated, parasite form in hepatocytes; produces no inflammatory response. Erythrocytic schizont: multinucleated stage in a RBC resulting from asexual multiplication of trophozoite. Each schizont contains a species determined number of meroziotes P.vivax P.falciparum The trophozoites that are left over during division can, in the course of the next day, develop into the sexual form, the gametocyte, which can be taken up by a blood-sucking mosquito and start another cycle. Trophozoite are metabolically active form of the malaria parasite living within the RBC; sometimes called the ring form. P.vivax P.ovale P.falciparum The incubation period (time from infection to development of the disease) is usually about 10 to 15 days. This period can be much longer depending on whether any antimalarial medication has been taken. Plasmodium ovale and Plasmodium vivax can produce a dormant form, a hypnozoite, that can cause relapses of the disease months and even years after the original disease (relapsing malaria) because it's dormant in the liver cells. This is why it's important after these infections to be treated with primaquine to kill the liver stages. (Primaquine cannot be used by people with a condition called G6PD-deficiency.)