Transmission-Blocking Activities of Quinine, Primaquine, and Artesunate
Chotivanich K., Sattabongkot J., Udomsangpetch R., Looareesuwan S., Day NPJ., Coleman RE., White NJ.
<jats:title>ABSTRACT</jats:title> <jats:p>The infectivity of <jats:italic>Plasmodium falciparum</jats:italic> gametocytes after exposure in vitro to quinine, artesunate, and primaquine was assessed in <jats:italic>Anopheles dirus</jats:italic>, a major vector of malaria in Southeast Asia. Mature gametocytes (stage 5) of a Thai isolate of <jats:italic>P. falciparum</jats:italic> were exposed to the drugs for 24 h in vitro before membrane feeding to <jats:italic>A. dirus</jats:italic>. 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<jats:sub>50</jats:sub>, and EC<jats:sub>90</jats:sub>, 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<jats:sub>50</jats:sub> of quinine, 642 (111) ng/ml; EC<jats:sub>50</jats:sub> of primaquine, 181 (23) ng/ml; EC<jats:sub>90</jats:sub> of quinine, 816 (96) ng/ml; EC<jats:sub>90</jats:sub> of primaquine, 543 (43) ng/ml. Artesunate both prevents the maturation of immature <jats:italic>P. falciparum</jats:italic> gametocytes and reduces the transmission potential of mature gametocytes. Both of these effects may contribute to reducing malaria transmission.</jats:p>