Malaria

Antimalarial drug efficacy and drug resistance

Antimalarial drug resistance hinders malaria control and is therefore a major public health problem. Tracking of evolving antimalarial drug efficacy patterns is essential for proper management of clinical cases and to determine thresholds for revising national malaria treatment policies.

An example: battling malaria drug resistance along the Thai-Cambodian border

WHO has regularly updated the protocol for assessing the therapeutic efficacy (also known as in vivo testing) of antimalarial drugs. Due to longer follow-up, genotyping to distinguish reinfection and recrudescence has become mandatory. WHO has developed software programmes, designed to facilitate data collection and analysis and to improve their quality. WHO is compiling in a database the results of therapeutic tests performed from 1996 onwards and the results classified by country or by drug are regularly updated.

To confirm antimalarial drug resistance other tools are needed such as in vitro sensitivity assay, studies of gene mutations or gene amplification associated with parasite resistance and/or measurement of antimalarial drug concentration. The most commonly used methods for the antimalarial in vitro testing are the in vitro micro-test Mark III, the isotopic test, the drug sensitivity assay based on the measurement of HRP2/or pLDH/ in an enzyme-linked immunosorbent assay (ELISA) and SYBER green test. Molecular markers of P. falciparum resistance are available for only a few drugs (chloroquine, mefloquine, pyrimethamine, cycloguanil, sulfadoxine, atovaquone), while for others they are not yet determined.