Malaria, a scourge of much of the developing world, kills some 2.7m people every year, most of them children under five and pregnant women, while up to 500m become ill, cannot work and need care.
A few decades ago, world health specialists talked of eradicating malaria. Now they talk only of trying to regain control. Malaria is endemic in more than half the world's countries. In the time it takes to name the disease, 10 children will contract it and begin fighting for their lives. One child in four who dies in Africa has succumbed to malaria.
DDT has a bad name. It is a pesticide that damages the environment and has been widely used in agriculture. Since Rachel Carson exposed its depredations in her book Silent Spring in 1962, environmentalists have campaigned to curb its use. In the west they have been successful.
But in the developing world it has saved millions of lives. Sprayed inside houses, it kills or more often repels the mosquitoes whose bite transmits malaria, and it is cheap. Specialists argue that it does not migrate out of doors, and if we lose it through a global ban in 2007 millions who could have been protected will die.
It is a head-on clash between first world environmentalists, who insist that DDT must go for the health of the planet and that alternatives will and must be found, and the malaria specialists, who say that until alternatives are in place that are as cheap and effective it would be catastrophic to ban it.
What will happen is clear, say the doctors. Under pressure from the west, which has no malaria, and amid worries about damage to human health from DDT, some developing nations have stopped or cut down on its use. Their sickness and death toll from malaria has risen. Effective alternatives have not been put in place, being too complex or, usually, too expensive.
The World Wide Fund for Nature, at the forefront of the campaign to ban DDT, talks about environmental management and biological control instead of pesticides, citing examples in India, Tanzania, Mexico and the Philippines.
But even these small-scale projects have run into difficulties -- apart from in Tanzania, where bed nets are sprayed with synthetic pyrethroids. This sort of alternative might be acceptable to all, but pyrethroids are up to three times more expensive than DDT, although on bed nets they are used in smaller quantities, and projects to provide sprayed nets for large numbers of people are inevitably more complex than spraying house walls.
Don Roberts, professor of tropical public health at the uniformed university of health sciences in Bethesda, Maryland, cites what happened in Belize under pressure from the US to abandon DDT. "They stopped in the late 1980s to early 1990s, and malaria rates spiralled out of control, peaking in 1994 ... In 1995 they started using DDT again and have brought disease rates down three years in a row."
Two years ago, in the journal Emerging Infectious Diseases, he showed that Ecuador, which increased its DDT spraying while others cut down, was the only one of 11 malaria-endemic South American countries to have reduced its detection rate. With organized DDT house spraying, malaria in urban areas of the Amazon basin largely disappeared, but it is again becoming a big health problem.
Sense of balance
Professor Roberts does not like the confrontation with the environmental lobby. "We're all concerned about the environment,"he said. "This is not limited to a few who want to get rid of DDT. But environmental issues have to be treated with a sense of balance." If this were the battle to eliminate DDT from agriculture, he would be applauding. Is it feasible to get alternative malarial control measures in place before 2007? "Absolutely not," he said.
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