South-East Asia Regional Conference on Epidemiology

Antimalarial drug resistance: a potential global
emergency
Charles Delacollette
Malaria resistance to the globally-promoted artemisinin-based combination therapies (ACTs),
which is emerging in the Mekong region, is a potential global emergency. Epidemiological data
provided by Mekong countries to WHO show that malaria and many other communicable diseases
are more common on international borders (1). Effectively controlling diseases and other threats on
international borders remains a challenge for many reasons, one of them being that some of these
countries are not at peace with each other. A decline in the therapeutic efficacy of all antimalaria drugs
has been observed in this region starting with chloroquine, then sulfadoxine-pyrimethamine (SP),
mefloquine, and now ACTs (2). Prediction-efficacy monitoring is being carried out for informing
policy-makers. There is a constant need to identify alternative therapies to existing ones which are
seriously failing.
This year is the sixtieth anniversary of intensified malaria control in Thailand. In this country,
the antimalarial drug policy has changed several times – from chloroquine to SP to quinine and
tetracycline to mefloquine, and, from 1995 to date, to ACT. Based on growing evidence that the
currently-recommended ACT is failing in Thailand, a change to more efficient and preferably coformulated
therapies has to be considered (3).
There is recent evidence from molecular markers that parasite strains resistant to chloroquine and
SP spread from <strong>Asia</strong> to Africa. The fear is that the same scenario could happen with falciparum
strains showing growing tolerance to artemisinins. First cases showing resistance to chloroquine
occurred in1957 in <strong>Asia</strong> and Latin America. Molecular biologists have identified genetic
markers of resistance to chloroquine and SP in Africa similar to those in <strong>Asia</strong> while looking
back at blood samples kept in laboratories all over the world. They were able to trace the last
60-years’ history of malaria parasite genes everywhere in the world (4,5). What has happened with
chloroquine and SP could similarly happen with antimalarial medicines that national programmes
are currently promoting in the Mekong region. That is why WHO has set up its regional sentinel site
surveillance network to monitor the therapeutic efficacy of antimalarial drugs promoted as first-line
drugs. As a matter of principle, all policy-makers should formulate a policy based on strong evidence.
The first thing that has to be done is to convince researchers and national programme managers that
they have to use the same methodology to measure resistance. That is why sites have been set up
where the therapeutic efficacy of any drug, preferably by using similar techniques, can be carried
out. Technical support, including training and funds, are provided to help them implement the socalled
WHO standardized in vivo protocol (6). This is not so simple, at least for those working at the
programmatic decision level, who are not necessarily researchers.