Declining artesunate-mefloquine efficacy against falciparum malaria on the Cambodia-Thailand border

Abstract

Resistance to many antimalaria drugs developed on the Cambodia-Thailand border long before developing elsewhere. Because antimalaria resistance is now a global problem, artemisinin-based combination therapies (ACTs) are the first-line therapies in most malaria-endemic countries. However, recent clinical and molecular studies suggest the emergence of ACT-resistant Plasmodium falciparum infections in the Cambodia-Thailand border area, where standard ACT is artesunate and mefloquine. These ACT failures might be caused by high-level mefloquine resistance because mefloquine was used for monotherapy long before the introduction of ACT. This observation raises 2 questions. First, how can existing P. falciparum-resistant strains be controlled? Second, how can the evolution of new ACT- resistant strains be avoided elsewhere, e.g., in Africa? Enforcement of rational drug use and improved diagnostic capacity are among the measures needed to avoid and contain ACT resistance.

Figure

Map of the Cambodia–Thailand border showing the town of Pailin, Cambodia, and the provinces of Chanthaburi and Trat, Thailand; the areas are collectively known as the epicenter of drug-resistant malaria.