Life Cycle of malarial parasite ::
The life cycles of different species of human malarial parasites are similar The stages can described as follows
Asexual Cycle ::
Pre-erythrocytic Schizogony :: When an infected female mosquito bites for blood meal sporozoites are injected with the salivary fluid before the blood is sucked up The salivary thread is injected to prevent clotting of the blood at the site of the puncture From the blood stream they first go to the liver cells (pre-erythrocytic schizogony ) and than again invade circulating RBC (erythrocytic schizogony )
Erythrocytic Schizogony is also the asexual development of the parasites In red blood cell the parasites pass through various stages such as trophozoite schizont and merozoite The first stage is the ring form of trophozoite with a small ring of cytoplasm The parasite multiplies at the cost of the red blood cell Afully matured trophozoite fills up the greater part of the RBC At this stage its chromatin is divided into number of cells known as schizont Later RBCs are ruptured and merozoites (tiny malarial parasites ) are liberated At this stage various clinical symptoms are observed The period between the bite of the infected mosquito injecting sporozoites and the development of clinical symptoms in man is termed as Incubation period This period is usually of 10-14 days
Exo-erythrocytic phase :: The merozoites thus liberated may infect fresh red blood cells and may infect other liver cells where they multiply and liberate metacryptozoites The infection of fresh liver cells by cryptozoites or merozoites is exo- erythrocytic form (EEP) phase
Gametogony :: Some of the merozoites undergo meiotic division and form male or female gametes male gametes are termed as microgamets and female gametes are terned as macrogametes Male and female gametes do not combine in the host but when a female anopheles mosquito bites such a person a number of such gametocytes are ingested along with the other a sexual forms of the parasite by the mosquito Gametocytes reach the stomach of the mosquito and form macrogamete and microgamete They unite and thus fertilization takes place and zygote is formed A cyst is formed around the zygote which is called an oocyst Thus the phase of gametogony starts in human body and is completed in the body of the mosquito
Sporogony :: The oocysts thus formed in the stomach of mosquito undergo various changes and finally elongated bodies called sporozoites are formed These sporozoites are liberated into esophagus of mosquito from where they reach the salivary glands when mosquito bites a healthy person sporozoites are injected and that s how the life cycle continues
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