Transmission-Blocking Activities of Quinine, Primaquine, and Artesunate
Chotivanich K., Sattabongkot J., Udomsangpetch R., Looareesuwan S., Day NPJ., Coleman RE., White NJ.
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.