Two studies published in The Lancet and
Science last week show a worrying increase in resistance of the malaria
parasite at the Thai-Myanmar border.
Two
studies, reported in The Lancet and Science last week, places the spotlight on
malarial resistance at the Thai-Myanmar border.
The
studies, both funded by the Wellcome Trust and the U.S. National Institutes of
Health, follow reports in 2009 of the emergence of Artemisinin-resistant
malaria parasites in western Cambodia, 800 km away from the Thai-Myanmar border
where the new cases of resistance have been observed.
According
to the World Malaria Report 2011, malaria claimed an estimated 655,000 lives in
2010, mainly young children and pregnant women. The disease is caused by
parasites that are injected into the bloodstream by infected mosquitoes.
The
declining efficacy of Artemisinin drugs, currently the frontline treatment
recommended by the World Health Organization (WHO) for the most deadly species
of the malaria parasite, Plasmodium falciparum, raises concern that resistance
might spread to India and then Africa, making elimination of the disease
impossible.
The
Lancet study was carried out over the ten years from 2001 to 2010 by
researchers at the Shoklo Malaria Research Unit on the border of Thailand and
Myanmar, part of the Wellcome Trust-Mahidol University-Oxford Tropical Medicine
Research Program.
They
measured how long it took to clear parasites from the bloodstream in 3,202
patients with falciparum malaria using oral Artesunate-containing medications.
Over
the decade, the average time taken to reduce the number of parasites in the
blood by a half, known as the ‘parasite clearance half-life,’ increased from
2.6 hours in 2001 to 3.7 hours in 2010, a clear sign that the drugs were
becoming less effective.
Of
greater concern, the proportion of infections that were slow-clearing, those
with a half-life of more than 6.2 hours, increased over the decade from six in
1,000 to 200 in 1,000.
Compelling
evidence that the decline in the parasite clearance rates was due to genetic
changes in the parasites was found on examination of their genetic make-up.
“We
have now seen the emergence of malaria resistant to our best drugs, and these
resistant parasites are not confined to western Cambodia,” said Professor
François Nosten, Director of the Shoklo Malaria Research Unit.
“This
is very worrying indeed and suggests that we are in a race against time to
control malaria in these regions before drug resistance worsens and develops
and spreads further.”
The
effect of that happening could be devastating, Nosten said, as malaria already
kills hundreds of thousands of people a year. Should the drugs become
ineffective, this figure will rise dramatically, he warned.
“If we
can identify the genetic determinants of Artemisinin resistance, we should be
able to confirm potential cases of resistance more rapidly,” said the leader of
the genetics studies in both papers, Dr. Tim Anderson from the Texas Biomedical
Research Institute.
The
team has already identified the genome region that harbors a number of
potential genes that may drive Artemisinin resistance. Finding the precise gene
location for Artemisinin resistance could be critically important for limiting
further spread of resistance, Anderson said.
The
articles can be found at:
Rebecca
Lim
AsianScientist
Source: Wellcome
Trust.
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