The mosquito bites back.

Traces the history of the use of DDT for controlling malarial mosquitoes. Once thought to be a solution to the malaria problem, it became apparent that DDT was a danger to the environment. The mosquito became resistant to it and as DDT had killed its predators, the malarial mosquito became a greater problem than it had been before the use of DDT. Another result of belief in DDT was that research on anti- malarial drugs declined. With the parasite's growing resistance to existing drugs, scientists are investigating wormwood, a long-standing Chinese treatment for malaria. Pictures: Mosquito biting; blood vessels; parasites in blood; mosquito's mouth; scientist with mosquitoes on arm; spraying DDT; malaria parasite. Male mosquitos cannot bite; they live on nectar. The females seek prey to bite about twice during their life cycle, when they need a blood meal because it is time to produce eggs. 200 million people suffer from malaria; over 1 million die every year. The malaria parasite evades anti-malarial drugs by mutating, thus becoming immune to them. In 1955 the WHO announced that DDT (developed in the U.S. during WW2 to save soldiers from insect-borne diseases) was the miracle substance for dealing with malaria-carrying mosquitoes. Spraying with DDT seemed a better course of prevention than attempting to drain every breeding site of the malarial mosquito; but this chemical killed all other insects, including those that prey on the mosquito. The effectiveness of DDT continued for 13 years in the tropics, especially S.E. Asia. Malaria seemed to be disappearing. By the 1960s, however, questions were raised about the safety of pouring so much poison into the environment and by 1970 the mosquito had developed resistance to DDT. It was aided in its return by land development in S.E. Asia, where forest clearance resulted in pools of water forming in open land. Mosquitoes flourished in this ideal breeding environment, especially as their predators had been eliminated by DDT. Belief in DDT resulted in almost twice as much malaria as before and because of its apparent success, work on anti- malarials declined. The only remaining effective drug was chloraquin, and the mosquito has developed immunity to that. Now, scientists are investigating wormwood, used for 2000 years by the Chinese as an anti-malarial