A cheap and effective treatment for malaria could be widely available within a decade after scientists genetically engineered a form of yeast to produce a key component of the drug used to fight the disease.

The advance by a research team in the United States should dramatically reduce the cost of manufacturing artemisinin, the most effective therapy for the world’s second most deadly infectious disease.

While artemisinin combination therapies (ACTs), in which it is given in combination with older anti-malarial drugs, are recommended by the World Health Organisation as the best way of fighting malaria, their cost places them beyond the means of many of the developing countries where the disease is most prevalent.

The production of artemisinin requires an acid that is extracted from the sweet wormwood plant, Artemisia annua, which is grown in China. The raw material is expensive, which puts the cost of a course of ACT at about $2.40 (£1.37) per person.

By producing artemisinic acid, the key precursor of artemisnin, artifically from genetically modified yeast or bacteria, researchers hope they will eventually be able to reduce this to as little as 25 cents (14p) per dose, making it far more widely available in poor countries.

Malaria kills more people each year than any other infection except HIV/Aids, with an annual death toll estimated at between one million and 2.7 million. It infects between 300 million and 500 million people a year, chiefly in Africa, and 2.2 billion people — a third of the world’s population — are at risk of contracting it.

The new strain of yeast has been engineered by a team led by Jay Keasling, Professor of Bioengineering at the University of California, Berkeley, which two years ago discovered it was possible to modify microbes to make artemisinic acid.

The yeast, details of which are published today in the journal Nature is an efficient producer of the acid yet, and should allow scientists to sidestep expensive laboratory processes currently needed to synthesise artemisinin.

While the scientists do not believe it will be possible to make artemisinin itself in microbes, making the precursor is almost as good, they said. All the artimisinin drugs currently on the market are made from the precursor acid.

"This is probably as close to artemisinin as we are going to get in microbes," Professor Keasing said. "The rest is going to be done by chemistry. This was our highest hurdle, what kept me up at night. Now that we’ve got all the parts, I feel it’s just a matter of time before we have a microbe ready for scale-up to production."

The gene inserted in the yeast was identifed in Artemisia annua as the one responsible for making artemisinic acid, by Dae-Kyun Ro of the Berkeley team. Professor Keasling said: "We reached our goal early, thanks to a number of miracles. The first gene Dae-Kyun isolated was the right one, the gene was functional in yeast, the gene’s enzyme did in one step what we thought took three enzymes, and the artemisinic acid it produced didn’t interfere much with the cell."

It is likely to take between five and ten years to develop the yeast as a large-scale producer of artemisinic acid, chiefly because the amount it makes is still relatively small. The work, which also involves Amyris Biotechnologies, a California-based company, is supported by a $43 million (£24.5m) grant from the Bill and Melinda Gates Foundation.

Victoria Hale, chief executive of the Institute of OneWorld Health, a non-profit pharmaceutical company that will now start testing the new product, said: "The team at UC Berkeley has done a great job moving this important project forward. We still have a long way to go, but this puts us one step closer to a low-cost treatment for malaria."

Other groups of scientists are also working on an entirely synthetic drug called OZ227, which is based on artemisinin’s action and could also be mass-produced at low cost.

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