Syndey, Feb 20 (IANS): A key discovery related to young malaria parasites' lower sensitivity to drugs could turn the tide against the global scourge, say researchers.

The University of Melbourne researchers have shown for the first time that fledgling malaria parasites (Plasmodium falciparum) are more than 100 times less sensitive to artemisinin-based drugs, the last line of defence against malaria, which kills a person every minute.

Artemisinin (ART) saves millions of lives each year but it is still not clear exactly how it works, the journal Publication of the National Academy of Science reports.

The team led by professor Leann Tilley and Nectarios Klonis, biochemists and molecular biologists at Melbourne, developed a new approach to examine how the parasite responds to drugs. This is important because the parasite takes two days to reach maturity in each cycle but the drug only remains in the bloodstream for a few hours.

"We were surprised to find that juvenile parasites were up to 100 times less sensitive to the drug than mature parasites, and that in some strains the juvenile parasites showed a particularly high degree of resistance," said Tilley, according to a Melbourne statement.

In order to survive in the human body, the parasite must inhabit red blood cells for part of its life cycle. To do this, it first digests the cell contents including the haemoglobin protein which carries oxygen in blood.

"We found that the parasite is most susceptible to drug treatment when it is digesting haemoglobin, suggesting that a breakdown product, possibly the haemoglobin pigment, is activating ART to unleash its killing properties," Klonis said.

The lower drug sensitivity of juvenile parasites was first suspected when the team studied the parasite's digestive system using a revolutionary 3D imaging technique called electron tomography at the Melbourne's Bio21 Institute.