Monitoring Plasmodium falciparum chloroquine resistance in Yunnan Province, China, 1981-2006.

The emergence and spread of drug resistant malaria parasites are an important factor contributing to the global resurgence of malaria, demonstrating the essence of drug resistance surveillance in endemic areas. In the malarious border regions of Yunnan Province, China, we have selected three study sites to monitor in vitro and in vivo resistance of Plasmodium falciparum parasites to chloroquine (CQ) from 1981 to 2006. In vitro studies using the microtest clearly showed high degree of CQ resistance in the early 1980s, when CQ was replaced by artemether monotherapy for falciparum malaria.

[Fluctuation in the resistance of Plasmodium falciparum to chloroquine in China].

Objective: To investigate whether chloroquine-resistance of Plasmodium falciparum had changed after stopping or reducing the use of chloroquine as an antimalarial in Hainan and Yunnan provinces.

Methods: WHO standard in vitro microtest and 4-week in vivo test were used, assays were carried out in different time after stopping or reducing the use of chloroquine.

Results: In vitro test in Hainan indicated that the rate of chloroquine-resistant P.

Changes in susceptibility of Plasmodium falciparum to artesunate in vitro in Yunnan Province, China.

We investigated changes in the susceptibility of Plasmodium falciparum to artesunate in vitro using Rieckmann's microtest in Yunnan Province, China, during the period 1988 to 1999. Longitudinal surveillance studies in 1988, 1992 and 1999 revealed that the IC50s were 6.2, 7.