The threadlike malaria parasites enter the bloodstream and are carried to the liver where they invade liver tissue cells, transform into spores and replicate repeatedly. The spores, formed within cyst-like structures in the liver, are released into the bloodstream where they attack and destroy red blood cells. In the process, they undergo another transformation that allows a form of the parasite to attack and invade new red blood cells. The synchronized development of different stages of the parasite is responsible for the characteristic cycles of fever in infected humans. A form of the parasite periodically bursts from demolished cells and is released into the blood stream to invade new blood cells.
Different species produce different fever cycles.
Plasmodium falciparum has a forty-eight hour period between fever peaks. The process is repeated over and over until natural or acquired immunity, or antimalarial chemotherapy, or death brings the repetitive process to an end. When an anopheline mosquito takes blood from a malarious human, the parasite enters the mosquito and goes through a number of complex changes over a 14 to 21 day period. It becomes an infectious form and moves to the mosquito's salivary glands where it is ready to reinfect and complete the cycle. Many people in Africa and other areas with intense malaria transmission, carry parasites without being ill.