Assessment of susceptibility of Plasmodium falciparum to chloroquine, quinine, mefloquine, sulfadoxine-pyrimethamine and artemisinin in southern VietNam

Resistance to antimalarial chemotherapy is a major concern for malaria cont rol in Viet Nam. In this study undertaken in 1998, 65 patients with uncompl icated Plasmodium falciparum malaria were monitored for 28 days after compl etion of a 5-day treatment course with artemisinin. Overall 36-9% (24/65) o f patients had recurrent parasitaemia during the surveillance period. P. fa lciparum isolates were tested for sensitivity in vitro to chloroquine, mefl oquine, quinine, sulfadoxine-pyrimethamine and results were compared to tho se from a similar study in 1995, Increased parasite sensitivity to sulfadox ine-pyrimethamine, chloroquine and quinine was demonstrated, with significa ntly lower mean EC50 and EC99 values in 1998 compared to 1995. Parasite sen sitivity to mefloquine did not differ significantly in the 2 surveys. Isola tes were also tested for sensitivity in vitro to artemisinin in the 1998 su rvey. The mean EC50 was 0.03 mu mol/L and the EC99 was 0.94 mu mol/L. Paras ite sensitivity to artemisinin will need to be monitored in view of its inc reasing use in Viet Nam.