Plasmodium falciparum gametocytes: their longevity and infectivity.

The longevity and infectivity of isolated populations of Plasmodium falciparum gametocytes were studied. Following chloroquine treatment gametocyte numbers fell with a constant rate of loss over a period of 16-24 days; the populations had a half-life of 2-4 days. The sex ratio stayed constant throughout at 4 female: 1 male. The ability of the microgametocytes to exflagellate and the infectivity of the population to mosquitoes persisted for 3 weeks. Antibodies to the gametocytes were detected but not in every patient studied. It was concluded that the gametocytes of P. falciparum are both long-lived and show persistent infectivity to mosquitoes. They can stimulate antibody production but the immune response appears to play no part in their elimination, which probably takes place in the spleen as a part of the normal process of removing old, damaged and malformed red cells.