WHO cracks down on new malaria resistance

A malaria patient in Thailand Copyright: Flickr/.ash

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Urgent measures are being taken by the WHO along the Thai-Cambodia border in response to the first signs of resistance to the antimalarial wonder drug artemisinin.

Fears about a full outbreak of the resistant malaria are so great that US$22.5 million will be spent on high-quality drugs and bednets for affected provinces, as well as research and improved case management.

"Before, we were warning people that there could be an emergence of artemisinin resistance. Now there is artemisinin resistance … the tone [of our warning] has changed," Pascal Ringwald, malaria coordinator at the WHO, told SciDev.Net.

The WHO has been concerned since 2005, when artemisinin effectiveness at the border was found to be deficient.  

Many people in the area have been using artemisinin alone, rather than in artemisinin combination therapies (ACTs) as recommended. Using artemisinin alone encourages the parasite to adapt to, and eventually overcome, the activity of the single drug.

The WHO is unsure what has triggered the resistance and some of the money will fund research to address this issue.

"There are some gaps in our knowledge," says Ringwald. "For instance, we do not know yet what is the [genetic] mutation that occurs in parasites with regards to artemisinin resistance."

"Many people talk about elimination and eradication, and ACTs are one of the effective weapons we have. We have not yet lost this weapon but we’re detecting a problem — it’s like a car that cannot reach maximum speed." ACTs are effective in more than 90 per cent of cases but we will "completely lose this weapon" if resistance spreads, he adds.

The most important preventative measure, says the WHO, is using combination therapies. Countries must ban the use of artemisinin monotherapies, and ensure that only good-quality drugs are used. Vector control must also be strengthened; ensuring that coverage with bednets and hammock nets.  

This is not the first time that resistance to antimalarial drugs has occurred along the Thai-Cambodia border — resistance to chloroquine developed in the 1950s, followed by sulfadoxine-pyrimethamine and mefloquine.

Ringwald says the current outbreak of resistance has been detected early enough, but without action a serious problem could emerge.

"At this stage, the chances of success depend on whether or not the resistance has already spread beyond the border. If it is limited to [the border city] Pailin and the Pailin area, the chances of success are very high. If not … we can’t begin to imagine how big a problem it will be."

The funds, given by the Bill and Melinda Gates Foundation, were announced by the WHO last week (25 February).

A separate group published a paper in PLoS ONE last week (23 February) providing evidence of "small but significant increases in parasite tolerance" to artemisinin on the Thai-Myanmar border. The authors advocate close monitoring to check for the emergence of resistance.