Southeast Asia is the first place where resistance has emerged in malaria parasites to artemisinin-based drugs. Currently the most effective treatments for malaria worldwide are drugs derived from artemisinin used in combination with other drugs. The use of two different drugs together aims to ensure that parasites resistant to one drug are killed by the other, before they can spread. The spread of artemisinin resistance from Asia to Africa and beyond would be a devastating setback to the global progress achieved so far in malaria control and elimination efforts.
Development of antimalarial drug resistance in Plasmodium falciparum, the species of malaria parasite responsible for the majority of malaria deaths, is not new. Since the late 1950s, resistance to chloroquine developed in two regions - South America and Southeast Asia - and is now widespread throughout the world. Resistance of P. falciparum to other antimalarial drugs including sulfadoxine-pyrimethamine (Fansidar) and mefloquine followed within a few years of their introduction.
In the 1990s, artemisinin-based combination therapy (ACT) was pioneered to respond to the growing spread of malaria drug resistance. The use of ACTs, along with increased investment in effort and funds to ensure broad access to effective malaria interventions, has resulted in exceptional progress being made in the fight against malaria around the world.
However, recent evidence has suggested declining efficacy of artemisinin-based derivatives when used alone and not in combination with other effective antimalarials, particularly on the Thai-Cambodian border. Studies on the efficacy of antimalarial drugs have demonstrated a significant delay in the time it takes to clear the parasite from patients in the border area. More recently, this alarming trend has also been detected among patients in neighbouring countries through routine drug resistance monitoring sites. This has prompted the World Health Organization (WHO) and partners to develop an inter-country strategy to contain the spread of artemisinin resistance in the region.
It should be noted that the genetic molecular marker for artemisinin resistance has not yet been identified. At present, the delayed parasite clearance detected among some patients on the third day following treatment is perhaps only an early warning sign and serving as an indication of the emergence of artemisinin resistance.
For more information on Malaria Consortium's work around drug resistance, please read our Project Brief.