Malaria lifecycle
we know that Malaria is a mosquito borne disease caused by protozoan parasite of Plasmodium species particulary
- P.vivax
- P.falciparum
- P.malariae
- P.ovale.
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To complete the life cycle Plasmodium spp require 2 phases including,
- Asexual (schizogony)
- Sexual(sporogony)
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When we talk about human malaria the asexual stages occur in Human ,while sexual stages occur in Anopheles mosquito. Again this asexual phase can be divided in to 2 stages
- Exo erytrocytic stage( Hepatic stage)
- Erythrocytic cycle
Therefor, in human ,the parasite grow and multiply first in liver cells and then attack the RBCs. These blood stages of parasite are responsible for the symptoms of Malaria.
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Infected Anopheles mosquito contain sporozoits, a form of parasite in their salivary gland. When they bite a human, they inject saliva together with the sporozoits, which first migrate to the liver and start hepatic phase of the schizogony.
Sporozoits infect the hepatocytes & Mature in to schizonts. Then it will, rupture and realase merozoites
(Here, there is a special case in P.vivax(Benign tertian) and P.ovale (Ovale tertian). Some of schizonts can become a dormant stage called hypnozoits and persist in liver. Later they become active and cause relapses by invading blood stream)
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After this liver schizogony, the merozoites infect RBCs and begin Erythrocytic cycle Merozoites , become ring shape tropozoites and then mature in to schizonts within RBCs.
Mature schizonts then rupture and release merozoites in to blood stream
 This merozoites can attack uninfected /infected RBCs and then occur in cyclic manner. Some of this stages differentiate in to male and female gametocytes( also we call as , microgametocytes and macro gametocytes).
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When an Anopheles mosquito obtain a blood meal, it ingest this gametocytes as well. In the stomach of the mosquito, microgamatocyte become microgamates and macrogametocyte become macrogamate. One of this microgamate penetrate the macrogamate , generate zygote. This zygote become motile and elongated giving rise to ookinate, which invade the mid gut wall. Ookinate in mid gut wall Develop in to oocysts. Oocysts develop and release sporozoites which find their place in salivary gland of mosquito.
When mosquito take a blood meal from human, it inoculate sporozoites in to the blood and this initiate a new cycle.
As a summery, Malaria lifecycle …
- Asexual life stage (schizogony) occurs in human
- Sexual life stages (sporogony) occurs in Anopheles mosquito
- Malariya Infective stage is sporozoites
- Diagnostic stages are immature trophozite or ring stage , Mature trophozite , Schizont & Gamatozite.
- Hypnozoites (dormant stage) only occurs in ovale and P.vivax
- Symptoms of malaria are caused by ruptured merozoites in blood
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