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Malaria life cycle illustration.
Credit: NIAID

Life Cycle of the Malaria Parasite

  1. A female Anopheles mosquito carrying malaria-causing parasites feeds on a human and injects the parasites in the form of sporozoites into the bloodstream. The sporozoites travel to the liver and invade liver cells.
  2. Over 5-16 days*, the sporozoites grow, divide, and produce tens of thousands of haploid forms, called merozoites, per liver cell. Some malaria parasite species also produce hypnozoites in the liver that remain dormant for extended periods, causing relapses weeks or months later.
  3. The merozoites exit the liver cells and re-enter the bloodstream, beginning a cycle of invasion of red blood cells, known as asexual replication. In the red blood cells they develop into mature schizonts, which rupture, releasing newly formed merozoites that then reinvade other red blood cells. This cycle of invasion and cell rupture repeats every 1-3 days* and can result in thousands of parasite-infected red blood cells in the host bloodstream, leading to illness and complications of malaria that can last for months if not treated.
  4. Some of the merozoite-infected blood cells leave the cycle of asexual replication. Instead of replicating, the merozoites in these cells develop into sexual forms of the parasite, called male and female gametocytes. In some malaria species, young gametocytes sequester in the bone marrow and some organs while late stage (stage V) gametocytes, circulate in the bloodstream.
  5. When a mosquito bites an infected human, it ingests the gametocytes. In the mosquito midgut, the infected human red blood cells burst, releasing the gametocytes, which develop further into mature sexual forms called gametes. Male and female gametes fuse to form diploid zygotes, which develop into actively moving ookinetes that burrow through the mosquito midgut wall and form oocysts on the other side.
  6. Growth and division of each oocyst produces thousands of active haploid forms called sporozoites. After 8-15 days*, the oocyst bursts, releasing sporozoites into the body cavity of the mosquito, from which they travel to and invade the mosquito salivary glands. The cycle of human infection re-starts when the mosquito takes a blood meal, injecting the sporozoites from its salivary glands into the human bloodstream.

* Time-frame depends on the malaria parasite species.


Diploid: Cells containing a full set of chromosomes.
Gametes: Reproductive elements, male and female.
Gametocytes: Precursors of the sexual forms of the malaria parasite, which differentiate into either male or female gametes within the stomach of the mosquito.
Haploid: Cells containing a half set of chromosomes.
Hypnozoite: The form of the malaria parasite that remains dormant in the liver.
Merozoite: The form of the malaria parasite that invades red blood cells.
Oocyst: A stage of the malaria parasite within the mosquito which is produced when male and female gametes combine.
Ookinete: The actively moving zygote of the malarial organism that penetrates the mosquito stomach to form an oocyst under the outer gut lining.
Schizont: The mature form of the malaria parasite within red blood cells that ruptures and releases merozoites.
Sporozoite: The infectious actively moving form of the malaria parasite, which is injected into people by mosquitoes.
Zygote: The diploid cell resulting from union of a male and a female gamete.

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Last Updated January 04, 2016