Drug Resistance in the Asia-Pacific

Resistance of Plasmodium falciparum to various malaria drugs is a major problem in the Asia-Pacific region. In some countries Plasmodium vivax has also developed resistance but only to chloroquine.

Some drugs used commonly until recently to treat falciparum malaria (chloroquine and sulfadoxine-pyrimethamine) are now reported to be ineffective in all malarious countries in the region. In recent years resistance to artemisinin (the most effective malaria treatment compound that we currently have) has emerged in the Greater Mekong Sub-region. Here multi-drug resistant falciparum malaria has now emerged, with parasites that are tolerant to chloroquine, sulfadoxine-pyrimethamine, artemisinin-based drugs and others.

Resistance to malaria drugs can be found at varying levels and low levels of resistance may not impact on control. Artemisinin and its derivatives, are not used alone for the treatment of uncomplicated malaria. They are typically combined with a partner drug, creating what is known as artemisinin-based combination therapy (ACT). Currently the level of artemisinin resistance means that ACT treatment can still be effective in these areas provided the partner drug is efficacious. However there is a real and serious risk that drug resistance will worsen and spread further within the region, as well as beyond. Intense efforts by the global malaria control community are underway to attempt to halt the spread of these resistant parasites and to delay emergence of resistance elsewhere. A small focus of ACT resistance has already emerged on the Thai-Cambodia border and extreme efforts are now underway to eliminate the disease in this area. Region-wide elimination efforts are also gathering pace.

In some countries in the region (Indonesia, Papua New Guinea and India) vivax malaria has been found to be resistant to chloroquine. A further concern for the vivax strain of malaria is that primaquine (the drug used to effect a ‘radical’ cure of vivax malaria, destroying the dormant stages in the liver to avoid later recurrence of the disease) appears to be less effective in Oceania.