title: Transmission-blocking activities of quinine, primaquine, and artesunate.
abstract: The infectivity of Plasmodium falciparum gametocytes after exposure in vitro to quinine, artesunate, and primaquine was assessed in Anopheles dirus, a major vector of malaria in Southeast Asia. Mature gametocytes (stage 5) of a Thai isolate of P. falciparum were exposed to the drugs for 24 h in vitro before membrane feeding to A. dirus. After 10 days, the mosquito midguts were dissected and the oocysts were counted. In this system, artesunate showed the most potent transmission-blocking activity; the mean (standard deviation [SD]) 50% and 90% effective concentrations (EC(50), and EC(90), respectively, in nanograms per milliliter) were 0.1 (0.02) and 0.4 (0.15), respectively. Transmission-blocking activity of quinine and primaquine was observed at relatively high concentrations (SDs): EC(50) of quinine, 642 (111) ng/ml; EC(50) of primaquine, 181 (23) ng/ml; EC(90) of quinine, 816 (96) ng/ml; EC(90) of primaquine, 543 (43) ng/ml. Artesunate both prevents the maturation of immature P. falciparum gametocytes and reduces the transmission potential of mature gametocytes. Both of these effects may contribute to reducing malaria transmission.
authors.affiliation: Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
authors.forename: Kesinee
authors.initials: K
authors.lastname: Chotivanich
authors.forename: Jetsumon
authors.initials: J
authors.lastname: Sattabongkot
authors.forename: Rachanee
authors.initials: R
authors.lastname: Udomsangpetch
authors.forename: Sornchai
authors.initials: S
authors.lastname: Looareesuwan
authors.forename: Nicholas P J
authors.initials: NP
authors.lastname: Day
authors.forename: Russell E
authors.initials: RE
authors.lastname: Coleman
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: White
mesh_terms: D000818:Animals; D000852:Anopheles / Q000469:parasitology; D000962:Antimalarials / Q000494:pharmacology / Q000627:therapeutic use*; D037621:Artemisinins / Q000494:pharmacology / Q000627:therapeutic use*; D000077332:Artesunate; D004199:Disease Vectors; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008018:Life Cycle Stages; D010270:Parasite Egg Count; D010963:Plasmodium falciparum / Q000254:growth & development* / Q000302:isolation & purification; D011319:Primaquine / Q000494:pharmacology / Q000627:therapeutic use*; D011803:Quinine / Q000494:pharmacology / Q000627:therapeutic use*; D012717:Sesquiterpenes / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: D000962:Antimalarials; D037621:Artemisinins; D012717:Sesquiterpenes; D000077332:Artesunate; D011803:Quinine; D011319:Primaquine