Global efforts to eradicate malaria have long relied heavily on DDT, short for dichloro-diphenyl-trichloro ethane. But this powerful chemical was banned decades ago in the United States and many other countries in response to concerns about its overuse in agriculture, and its potential toxic effects on humans and wildlife. Renewed support from global health agencies is helping to put DDT back in the battle against malaria.
Most experts agree: DDT is the most effective weapon in the war against malaria. It is cheap, it repels and kills mosquitoes quickly, and it is long lasting.
But use of DDT was curtailed by a ban in the United States in 1972. More recently it was targeted for phase-out under the United Nations Convention on Persistent Organic Pollutants in 2001.
While DDT was never fully outlawed, its use throughout the world has been greatly limited by the refusal of large donor agencies and development groups to purchase the insecticide.
But the increasing human toll of malaria has changed the mood of the international community. One million people die of the disease each year. Ninety percent of the 300-500 million annual cases are in Africa, where its prevalence in some countries is greater than HIV/AIDS.
In May of this year, the United States Agency for International Development endorsed DDT for malaria control, following the lead of the UN's World Health Organization. Dr. Shiva Marugasampillay, with WHO's Global Malaria program, says insecticide spraying with DDT has proven both effective and safe in several African countries.
"Countries like Namibia, which is using DDT, Botswana, Zimbabwe. At the moment Mozambique has started again and also Zambia. Another country that has shown tremendous success is Eritrea. Recently Kenya has started indoor residual house spraying again and also Uganda, although all of them are not necessarily using DDT."
Dr. Marugasampillay says these successes have helped guide the new WHO policy, which is based on scientific studies and advice from government and health officials. "The main focus of the recommendations is to re-look at indoor residual house spraying as a tool for malaria control and the use of DDT as appropriate among other chemicals," he says, adding the WHO also recommends "developing new chemicals that we could use to substitute for DDT."
The change in U.S. policy allows government aid agencies to support international programs that use DDT. According to Don Roberts, professor of tropical public health with the U.S. Armed Services' University of the Health Sciences that's an important break with the past. "I think that is a very good message. I think that it is a constructive message and I think that use of U.S. taxpayer money for that is way overdue. And I believe that it will save lives and think that it will greatly reduce the amount of disease in countries that choose to use it."
While environmental groups led the fight to ban DDT in the United States and phase out its use globally, activists like Ed Hopkins with the Sierra Club's Environmental Quality Program do not oppose the use of DDT to fight malaria. "We think that it is important to protect the health of people in the developing world. So if there are no better alternatives than DDT, we support the controlled use of that chemical."
Other critics fear DDT will be misused, difficult to monitor and pose a threat to wildlife and the environment. WHO's Shiva Marugasampillay disagrees. "The whole import and production is now a very licensed and controlled situation," he says. "When you are actually importing DDT in a country it can only be imported by the national public health agency, and it will only be delivered through the public health agency or others which the public health agency will supervise and in that way it will be highly controlled."
Dr. Marugasampillay says indoor spraying is an important strategy in the campaign against malaria. But he adds that the success of that campaign will also depend on whether countries have strong, well-organized public health systems to safely and effectively manage the use of DDT.