Modern afflictions like DVT, CJD and heart disease grab the medical headlines, but they are fleabites in the global disease league compared with the tropical pestilence, malaria. This scourge of the Indian subcontinent and Africa, caused by a microscopic parasite in the blood and spread by mosquitoes, was first described in Indian texts of 1600BC and has seen off as many as half of all humans.
Medical science held the disease in check in the 20th century, yet still there is neither vaccine nor a fully effective treatment, and it kills about a million a year, including a few business travellers. And because of global warming, carrier mosquitoes are moving into Europe. Thankfully, international researchers led by the Institute of Genomic Research in Maryland, US, have just completed the six-year task of mapping the genomes of both parasite and carrier, a breakthrough that could bring a range of potent new treatments.
THE CHALLENGE: Four species of parasite cause malaria, the most deadly of them Plasmodium falciparum, and 10 or more species of Anopheles mosquito spread the plasmodium by biting humans. Parasites are pumped into the human bloodstream with the mosquito's saliva. Once there, they move to the liver to recuperate and multiply before migrating to the vital oxygen-transporting red blood cells (see picture). These become so full of propagating plasmodium that they burst, causing fever and maybe death. A patient surviving the first crisis can suffer recurrent debilitating attacks for years.
Quinine - an extract of the bark of the cinchona tree - was the first anti-malarial treatment. It didn't work well and had an uncomfortable side effect - explorer David Livingstone (who died of malaria in 1876 despite taking quinine) described it as 'the most constipating drug'.
Nor are newer treatments like chloroquine and mefloquine fully effective; their widespread use means resistance builds quickly.
THE SOLUTION: Swamp-drainage schemes have reduced mosquito breeding grounds, and insecticides keep Anopheles under control in more populous regions.
But there are now super-mosies that are immune to most toxic sprays.
Enter the scientists with their map of the inner workings of both Anopheles gambiae and P falciparum. The parasite's 5,300 genes should provide many targets for new drugs to act on, making a vaccine possible in the long term. The mosquito's 14,000 genes are expected to yield opportunities for designer insecticides that kill only a few species. The grandest scheme is to replace infected wild mosquitoes with populations genetically altered to prevent them from transmitting the disease, a strategy that offers huge potential rewards. Those malarial biters could soon find themselves bit.