Humans contract the malaria parasite when bitten by a female anopheles mosquito, like the one pictured here. The parasite then begins the human stage of its lifecycle.

Credit: CDC

University of Oklahoma biochemistry professor Jun Li found a protein critical to malaria's life cycle by collecting data from mosquitoes in Africa, and blood from people infected with malaria.

Credit: Jun Li, University of Oklahoma

The malaria parasite life cycle involves two hosts, illustrated in this chart from the Centers for Disease Control and Prevention. During a blood meal, a malaria-infected female Anopheles mosquito inoculates sporozoites into the human host. Those sporozoites infect liver cells. From there, the parasite matures, multiplies and invades the bloodstream (some strains can persist in the liver and cause relapses by invading the bloodstream weeks, or even years later). When another female Anopheles mosquito bites the infected human, it ingests malaria gametocyctes, beginning the mosquito stages of the parasite's life. Li's virus would make an infected human a "dead end" for the disease, so that any mosquitoes that bite that person would not be able to spread it.

Credit: CDC

This thin human blood smear primarily shows the P. falciparum malaria parasite in its gametocyte form--which, when ingested by a mosquito during a blood meal, starts the mosquito stages of the parasite's life, allowing it to spread. Also seen are trophozoites of the parasite.

Credit: CDC

This thin human blood smear primarily contains gametocytes of P. falciparum. The gametocyte in the upper right is undergoing exflagellation, a process that normally occurs in the mid-gut of the mosquito host. However, it may be observed in human blood specimens when there is a delay in processing the blood.

Credit: CDC