London: Malaria parasites in western
Cambodia have become resistant to artemisinin-based therapies,
the first-line treatment for malaria, according to a study by
Oxford University researchers.
The study, conducted by the university`s experts based
in Thailand, has been published in the New England Journal of
Medicine.
Signs of artemisinin resistance have been reported in
the region, but this new research is the first detailed study
of the problem, a university release said.
Resistance to the drugs could eventually render them
obsolete, putting millions of lives at risk.
Professor Nick White, co-author of the study, believes
the implications of the findings are potentially huge,
"Artemisinins are essential weapons in our war against
malaria. If they become ineffective, we have no immediate
replacement. The consequences could be devastating.
Elimination of malaria will not be possible and millions of
lives could be lost."
Malaria kills more than a million people each year,
mainly young children and pregnant women. It is caused by
malaria parasites, which are injected into the bloodstream by
infected mosquitoes. The most deadly form, Plasmodium
falciparum, is responsible for nine out of ten deaths from
malaria.
Artemisinin is the most effective anti-malarial drug
so far. Artemisinin derivatives have the advantage over other
anti-malarial drugs, such as chloroquine and mefloquine, in
having few side effects and – until now – malaria parasites
had no resistance against it.
Although the drugs – most commonly in the form of the
derivative artesunate – can be used on their own as a
monotherapy, fears over the possible development of resistance
mean that they are usually given in conjunction with one or
more other drugs.
These artemisinin-based combination therapies (ACTs)
are now recommended by the WHO as the first-line treatment for
uncomplicated falciparum malaria in all endemic countries.
The researchers studied 40 patients in Pailin, western
Cambodia, and 40 patients in Wang Pha, north-western Thailand.
Each was given either the artemisinin-derivative artesunate or
a combination of artesunate and mefloquine.
On average, patients in Thailand were clear of
parasites in 48 hours; in western Cambodia this took 84 hours
– in other words, it took almost twice as long to clear the
parasites in Cambodia as it did in Thailand.
Out of the 20 patients treated solely with artesunate
in each country, there were recurrences of the infection in
six patients in western Cambodia compared to just one person
in Thailand. Of the 20 patients treated with the combination
therapy, infection recurred in two patients in Cambodia
compared to one in Thailand. These results again suggest that
artemisinin was less effective on the Cambodian parasites.
Bureau Report