Life Cycle of Plasmodium Malariae

The single-celled Plasmodium parasite causes malaria. Plasmodium occurs in four types, each of which causes a different kind of malaria: Plasmodium falciparum causes malignant malaria, which is the most deadly variety; Plasmodium vivax, Plasmodium ovale and Plasmodium malariae ("P. malariae") are all more benign, with P. malariae being the least malevolent form. P. malariae infection presents as chronic flu-like symptoms, including fever, fatigue and diarrhea. Malaria treatment includes a drug called primaquine to prevent relapse of the more serious versions of the disease. Chloroquine is more often used to treat P. malariae infection.

A Mosquito Bites A Human

• The P. malariae life cycle begins with the female Anopheles mosquito, which is the only organism that can transmit the malaria parasite. When such a mosquito bites an uninfected human it releases P. malariae parasites (called sporozoites at this stage) from its saliva into the human's bloodstream.

The Malaria Parasite Reproduces in the Liver

• The sporozoites move to the human's liver cells. Over the next 72 hours, the sporozoites mature and reproduce into merozoites or "daughter parasites."

The Parasite Spreads to the Blood

• Now the merozoites can move into the infected human's bloodstream and invade the red blood cells. The merozoites grow and reproduce asexually inside the red blood cells, eventually causing the cells to rupture and release even more merozoites into the blood stream. During this phase, the merozoites are known as "blood-stage parasites." Most merozoites continue to reproduce this way, infecting and rupturing more and more of the human's blood cells. This is when the infected human begins to experience the initial symptoms of malaria, such as fever and chills. But not all merozoites simply reproduce: a small percentage differentiates into male and female gametocytes.

Another Mosquito Bites the Infected Human

• Now another female Anopheles mosquito bites this infected human and ingests the male and female gametocytes, which then travel to the mosquito's intestines and reproduce in the midgut. Eventually the gametocytes form into a cyst, in which new sporozoites form.

The Life Cycle Begins Again

• After approximately 10 to 18 days, the sporozoites are sufficiently mature to be infective, which means they can now cause a malaria infection. At this point the sporozoites move to the mosquito's salivary glands and wait for the mosquito to bite an uninfected human. The female Anopheles mosquito bites an uninfected human and the life cycle begins again.