Transmission-blocking activity of artesunate, chloroquine and methylene blue onPlasmodium vivaxgametocytes

Abstract

Plasmodium vivax is now the main cause of malaria outside Africa. The gametocytocidal effects of antimalarial drugs are important to reduce malaria transmissibility, particularly in low transmission settings, but they are not well characterized for P. vivax. The transmission-blocking effects of chloroquine, artesunate and methylene blue on P. vivax gametocytes were assessed. Blood specimens were collected from patients presenting with vivax malaria, incubated with or without the tested drugs, and then fed to mosquitos from a laboratory-adapted colony of Anopheles dirus (a major malaria vector in Southeast Asia). The effects on oocyst and sporozoite development were analyzed under a multi-level Bayesian model accounting for assay variability and the heterogeneity of mosquito Plasmodium-infection. Artesunate and methylene blue, but not chloroquine, exhibited potent transmission-blocking effects. This suggests that patients with vivax malaria often remain infectious to anopheline mosquitos after treatment with chloroquine. Immediate initiation of primaquine radical cure or use of artemisinin combination therapies would reduce the transmissibility of P. vivax infections.