Fifty years ago Africa had a coherent strategy to fight malaria. It involved spraying large amounts of the pesticide dichlorodiphenyltrichloroethane, or DDT, to curb the mosquito that carries malaria. This campaign was hugely successful, but it came to a halt shortly after the 1962 publication of Rachel Carson's "Silent Spring," which described the environmental consequences of DDT running off into lakes and rivers. Malaria cases soared on the continent, except in South Africa, which continued to spray. Finally, in 1996, pressured by environmental groups, South Africa dropped DDT for a less toxic alternative. Four years later, the country was facing its first malaria epidemic in half a century.
Now the story has turned back again. South Africa resumed spraying in 2000, and malaria outbreaks declined. Health officials from South Africa and the United States helped persuade the World Health Organization to approve DDT for malaria control, saying the benefits were worth the risks. Today South Africa stands virtually alone on the continent, having gotten malaria under control again. (Zambia followed its lead with similar results.) Now the rest of the continent is coming along as well. Last year Mozambique embarked on a limited spraying campaign; health officials say they see signs of improvement. In November, Uganda will roll out a large-scale DDT regime, backed by its president, Yoweri Museveni. Tanzania and Kenya are both considering starting DDT-spraying campaigns.
The return of DDT is part of a broader recognition that controlling malaria is a high priority for Africa—and that fighting it will require all the tools health officials can muster. A wide spectrum of donor-driven initiatives and African government plans in recent years have been aimed squarely at malaria control, and some of that money is being spent on DDT programs. U.S. First Lady Laura Bush recently visited Mozambique on behalf of the $1.2 billion President's Malaria Initiative to promote, among other measures, the use of DDT in 15 African countries.
These and other malaria initiatives helped reduce the number of infant-mortality cases in Africa last year to below 10 million for the first time in decades, UNICEF reported last week. DDT will be an important tool to help further reduce the annual malaria death toll in Africa, which is now 1 million, most of them children.
Rachel Carson's claims about DDT may have been exaggerated, but scientists have changed their assessment of the risks in recent years. Whereas large-scale, indiscriminate spraying is harmful and still banned worldwide, targeted spraying in small amounts can deter mosquitoes with little effect on humans. In the past, health workers would cover entire walls with DDT; today they spray small amounts inside doorways and on other key spots in houses. The small dosages limit seepage into the water tables or soil beds.
DDT's main virtues are that it's cheap—six times cheaper than alternative pesticides—and long-lasting. One dosage can work for nine months, long enough to span peak malarial seasons in most places. "I'm thrilled about it," says Maureen Coetzee, chief of vector-control research at South Africa's National Institute for Communicable Diseases. "It's long overdue." The Gates Foundation is pouring nearly $5 million into Africa to make sure DDT and other insecticides are used properly.
That's a major challenge. Spraying too little, or in the wrong way, can foster resistance among mosquitoes. It's already happened in Ghana, Burkina Faso and other countries in west Africa, where farmers have reportedly been illegally spraying DDT on rice and cotton fields. In Nigeria, experts suspect that tons of unregulated, often homemade, chemical cocktails of uncertain quality are being used in ad hoc spraying campaigns. And in Zambia, researchers report that large amounts of pesticides are being divvied up and sold in small bottles for home use.
The WHO is also working to prevent misuse. Countries that wish to use DDT must register with the WHO, explain why they need it and issue an annual report.
Not everybody is in favor of using DDT. Some scientists believe that even small amounts in the environment can cause illness. But many former detractors say it's time to bring it back. The Environmental Defense Fund, which once promoted "Silent Spring" and helped champion the movement to ban DDT, has endorsed its limited use for malaria control. While North America and Europe were fighting malaria in recent decades, it seemed that health experts had written off Africa as too difficult. They've changed their minds on that, too.