Malaria is a disease caused by parasites of the genus Plasmodium, transmitted through the bites of female anopheles flies. Plasmodium falciparum causes severe malaria with undulating high fever (malaria tropica).The life cycle of plasmodium falciparum is shown in the image. File:630px-Plasmodium lifecycle PHIL 3405 lores.jpg
Lifecycle
In humans
Infection in humans begin with the bite of a female Anopheles mosquito. Anopheles gambiae is the one that is most prevalent in Africa.
The infective stage called sporozoites released from the salivary glands enters into the blood stream during feeding.The immune system clears the sporozoites in 30 minutes but a few enters the liver cells called Hypnozoites.
Liver stage or exo-erytrocytic schizogony
After entering the liver the parasite gets transformed into Trophozoite. This process is called shizogony.
Blood stage or erythrocytic schizogony
After entering the RBC they are called merozoites.With in the erythrocyte the parasite metabolism depends on the digestion of hemoglobin.The clinical features of malaria like fever, anemia and neurological symptoms appear during this particular stage.
In mosquito
Within the mosquito midgut, the female gamete maturation process entails slight morphological changes, becoming more enlarged and spherical.
The male gametocyte undergoes a rapid nuclear division within 15 minutes, producing eight flagellated microgametes by a process called Exflagellation. The flagellated microgamete fertilizes the female macrogamete to produce a diploid cell called a zygote.
The zygote then develops into an ookinete. The ookinete is a motile cell, capable of invading other organs of the mosquito. It traverses the peritrophic membrane of the mosquito midgut and crosses the midgut epithelium. Once through the epithelium, the ookinete enters the basal lamina, and settles to an immotile oocyst.
For several days, the oocyst undergoes 10 to 11 rounds of cell division to create a syncytial cell (sporoblast) containing thousands of nuclei. Meiosis takes place inside the sporoblast to produce over 3,000 haploid daughter cells called sporozoites on the surface of the mother cell.
Immature sporozoites break through the oocyst wall into the haemolymph. They migrate to the mosquito salivary glands where they undergo further development and become infective to humans.
Complications
Life threatening complications of malaria include:
Severe infection of the brain(cerebral malaria) which presents with seizures, confusion, and tiredness leading to coma.
Fluid in the lungs(pulmonary edema).
Kidney failure.
Aplastic anemia.
Prognosis
Most patients with uncomplicated malaria will improve rapidly within 48hrs when treatment is initiated early.However P falciparum carries a poor prognosis if left untreated.
