Plasmodium Life cycle Plasmodium species that infect humans Until recently, there were four plasmodium species that were considered responsible for malaria disease in humans: Transmission routes The main mode of transmission of the disease is by bites from infected Anopheles mosquitoes that have previously had a blood meal from an individual with parasitemia.
Less common routes of transmission are via infected blood transfusion, transplantation, infected needles, and from a mother to her fetus during pregnancy. Plasmodium life cycle The life cycle Figure 1 is almost the same for all the five species that infect humans and follows
Sporozoites asexual marriage stages: I ifection of a human with sporozoites II reproduction III sexual reproduction The two first stages take place exclusively into the human body, while the third one starts in the human body and is completed into the mosquito organism.
Plasmodium life cycle Source: Open Course Ware The human infection begins when an infected female anopheles mosquito bites a person and injects infected with sporozoites saliva into the blood circulation. That is
Sporozoites asexual marriage first life stage of plasmodium stage of infection. The next stage in malaria life cycle is the one of asexual reproduction that is divided into different phases: Within only 60 minutes after the parasites inoculation, sporozoites find their way through blood circulation to their first target, the liver.
The sporozoites enter the liver cells and start dividing leading to schizonts creation in 6- 7 days. Each schizont gives birth Sporozoites asexual marriage thousands of merozoites exoerythrocytic schizogony that are then released into the blood stream marking the end of the exoerythrocytic phase of the asexual reproductive stage.
It is worth mentioning that, concerning P. The exoerythrocytic phase is "Sporozoites asexual marriage" pathogenic and does not produce symptoms or signs of the disease. Its duration is not the same for all parasite species. Merozoites released into the blood stream, are directed towards their second target, the red blood cells RBCs.
As they invade into the cells, they mark the beginning of the erythrocytic phase. The first stage after invasion is a ring stage that evolves into a trophozoite.
The trophozoites are not able to digest the haem so they convert it in haemozoine and digest the globin that is
Sporozoites asexual marriage as a source of aminoacids for their reproduction. The next cellular stage is the erythrocytic schizont initially immature and then mature schizont.
Each mature schizont gives birth to new generation merozoites erythrocytic schizogony that, after RBCs rupture, are released in the blood stream in order to invade other RBCs. This is when parasitaemia occurs and cinical manifestations appear.
The liver phase occurs only once while the erythrocytic phase undergoes multiple cycles; the merozoites release after each cycle creates the febrile waves. A second scenario into the RBCs is the parasite differentiation into male Sporozoites asexual marriage female gametocytes that is a non pathogenic form of parasite.
The gametocytes, then, mature and become microgametes Sporozoites asexual marriage and macrogametes female during a process known as gametogenesis. The time needed for the gametocytes to mature differs for each plasmodium species: In the mosquito gut, the microgamete "Sporozoites asexual marriage" divides three times producing eight nuclei; each nucleus fertilizes a macrogamete forming a zygote.
The zygote, after the fusion of nuclei and the fertilization, becomes the so- called ookinete. The ookinete, then, penetrates the midgut wall of the mosquito, where it encysts into a formation called oocyst. Inside the oocyst, the ookinete nucleus divides to produce thousands of sporozoites sporogony.