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Saturday 15th June 2019

Malaria resistance spreads across Asia

10th April 2012

A new report has confirmed what many already feared, that the malaria parasite is becoming increasingly resistant to the latest treatments based on the traditional Chinese herb artemisia.


Researchers say they have now located resistant strains of the Plasmodium falciparum parasite, which is carried on female mosquitoes, on the Thai-Burmese border, 500 miles from where they last detected it.

They take the new evidence to mean that worldwide attempts to wipe out malaria are now "seriously compromised".

Current front-line malaria treatments have relied on artemisinin-based therapies. Artemisinin is derived from Artemisia annua, or sweet wormwood, and has been used for centuries in traditional Chinese medicine.

Writing in The Lancet, the researchers say that artemisinin-resistant P falciparum parasites were last discovered in western Cambodia in 2009.

Now, they are infecting patients several hundred miles away on the Thai-Burma border, according to a team of researchers from the Shoklo Malaria Research Unit.

Since 2001, the team has been measuring how long it takes for the parasite to clear from the blood of infected patients who are receiving artemisinin-based therapies. They say that over the nine-year period to 2010, the drug has become less and less effective, and taken longer to clear from the systems of the 3,000 patients studied.

This is a very serious development, according to research team member Francois Nosten, and will certainly compromise the idea of eliminating malaria. It will probably also mean a comeback for the killer disease.

Texas Biomedical Research Institute scientist Standwell Nkhoma said the findings could indicate a public health disaster in the making, that could result in millions of deaths.

It is unclear based on the current study whether the parasite developed its own resistance to artemisinin spontaneously, or whether the resistant parasite spread there.

If it moved, and continues to move, scientists fear that it could eventually reach sub-Saharan Africa. If it emerged spontaneously in Burma, then it could also emerge spontaneously in Africa, Nosten said.

The World Health Organisation has called in recent years for companies to stop selling pharmaceutical products that contain only artemisinin, calling for combination therapies as a way of staving off resistance.

Such therapies have made a huge contribution to a decline in malaria in many areas of the world.

Nosten said that if artemisinin was about to lose its effectiveness, much in the way that chloroquine did during the 1970s, then there were no new drugs in development to take its place, raising the spectre of untreatable malaria.

Writing in a separate paper in the journal Science, the researchers believe they have narrowed down the area of the P falciparum genome that is linked to artemisinin resistance.

According to Texas Biomed researcher Tim Anderson, it is important, if difficult, to map the geographical spread of drug resistance.

In 2010, malaria killed around 655,000 people around the world, which works out at more than one person a minute. Most of them were pregnant women and young children.

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