Is Malaria becoming more drug-resistant?

Yes

Two-drug combinations of an artemisinin compound (e.g. artesunate, artemether, dihydoartemisinin) plus a partner drug (e.g. mefloquine, piperaquine, lumefantrine) were introduced in the 1990s and early 2000s to try to overcome the problem of rapid resistance emergence in Plasmodium falciparum, which is the cause of most of the world’s malaria. This was very successful until around 2008-9 when scientists noticed that it took longer for the malaria parasite to be cleared from the blood in patients in Cambodia with the disease, related to decreased responsiveness to artemisinin. They were still cured eventually though. However since then resistance of the parasite to at least 2 of the partner drugs commonly used (mefloquine and piperaquine) has followed.

Studies of patients with malaria in Cambodia, Vietnam and Thailand have shown increasing numbers of treatment failures in people treated with standard combination therapies. This is very concerning because there are no new agents ready to replace the failing treatments. The problem seems to be confined to Southeast Asia at present but it is proving difficult to contain. If artemisinin resistance emerges in Africa and combination treatments start to fail there the prospects for successful containment are very limited and this could allow malaria to get out of control (~190 million of the estimated 207 million cases of malaria caused by P.falciparum in 2016 were in Sub-Saharan Africa). If this was to happen one of the likely outcomes would be a sharp increase in the number of child deaths from malaria (which is already high at >440,000 a year).

What can be done?

Different strategies which are being proposed are:

1.    Intensify malaria control efforts to try and bring down the global burden e.g. improve access to insecticide treated bednets, malaria diagnosis and treatments. One way this is done is to appoint villagers as health workers who are capable of making the diagnosis in their communities with rapid kits and provide quality-assured medicine free-of charge.

2.    Try to eliminate malaria from areas of artemisinin resistance. This can be done using the approaches described in (1). A reduction in malaria can be achieved more quickly with complementary strategies such as identifying communities where the malaria burden is higher and asking them if they are willing to all take malaria treatment (known as mass drug administration). This approach is taken because in malaria-endemic countries some people are carrying a low number of malaria parasites in their blood without any symptoms.

3.    Develop new medicines and vaccines. New compounds are being developed but they won’t be available for a few years.

4. Change the way we use the drugs we have e.g. by giving longer courses or by increasing the number of drugs used in a combination to treat malaria from two to either three or four in the hope this will overcome this problem of resistance development (HIV and TB are both treated with three or four drug combinations)