NEW YORK — A serious debate is raging over the use of DDT to combat malaria. As one of the world’s most serious tropical diseases, malaria kills more than a million people a year — most of them young children. To a great extent, success in controlling malaria is owed to the use of DDT in spraying houses and thus repelling the mosquito carrier of the parasite responsible for the disease.
Insistence on the part of some industrialized countries and environmentalist organizations not to fund those projects that fight malaria using DDT will do more harm than good. Unless this policy is reversed and projects using DDT continue to be funded, malaria will cause thousands of deaths that could have been prevented.
Most deaths by malaria occur in sub-Saharan Africa, where the disease is responsible for one in five of all children’s deaths. Malaria is also responsible for between 300 million and 500 million cases of acute illness in Africa, Asia and the Americas.
In Asia, a high risk of malaria exists in rural areas of Myanmar, Cambodia, Indonesia, Laos, Malaysia, Philippines, Vietnam and Thailand. Although the disease was eradicated in North Korea, it has made a resurgence in recent years. WHO estimates that as many as 300,000 North Koreans were infected with malaria in 2001.
Women are particularly vulnerable to malaria during pregnancy, when the disease can lead to serious anemia, miscarriages and the birth of premature, low-birth-weight babies.
In addition, malaria imposes significant economic costs, directly through health-care costs and indirectly through lost productivity.
According to Jeffrey Sachs, a development economist at Harvard University, sub-Saharan Africa could be a third richer today had the disease been eradicated in 1965. Since the 1960s, it is estimated that malaria has slowed economic growth in highly infected areas by 1.3 percent per year.
Over the years, several WHO experts have shown that DDT is the most cost-effective and time-tested tool to fight malaria. According to WHO reports, DDT has been responsible for freeing 32 percent of the world’s population from the risk of malaria. Also, because of its low cost, it is affordable to local governments of poor areas in developing countries, where it causes most harm.
DDT is not risk free. It was banned because of environmental and health effects when farmers used it to spray crops. It has been linked to hormone disruption, decreased fertility, suppression of the immune system and abnormalities in the nervous system. Because levels of DDT and its metabolites in humans are highest in breast milk and in the placenta, it poses special risks for the fetus and the nursing infant. It is unlikely, though, that the small amounts used in house-spraying causes serious effects either on human health or on the environment.
DDT’s negative effects tend to appear when spraying crops; they don’t happen as easily when DDT is used in house-spraying, which requires much smaller amounts of the insecticide. According to Amir Attaran, Ph.D., a researcher at Harvard University, the volume of DDT used to protect the entire high-risk population of Guyana for a year is equivalent to what a farmer might use to spray a single field of cotton.
Although there are alternatives to the use of DDT, such as compounds called pyrethroids, they are four times more expensive and less effective. There are also some indications that malarial mosquitoes are becoming resistant to pyrethroids. A study by John P. Grieco published in the Journal of Vector Ecology found that deltamethrin — an insecticide from this group regarded as the leading alternative — doesn’t come close to matching DDT’s performance.
During the 1950s and 1960s, the widespread use of DDT almost eliminated malaria in several developing countries and, by 1970, had saved an estimated 500 million lives. Now, however, of the approximately 100 countries where malaria is endemic, only 23 employ DDT to fight the disease.
When DDT-spraying stops, the number of malaria cases rises dramatically, as happened in South Africa, where the number of cases rose by 150 percent.
In several countries throughout the world, malaria is undergoing a massive resurgence, which makes it more urgent to implement effective actions, particularly since the creation of a vaccine against it is still proving elusive.
There are presently no cost-effective methods for the environmental management of malaria control, so there is no practical sense in promoting their application. Although finding a totally safe insecticide to deal with the malaria problem would be the ideal situation, until that happens DDT should continue to be used.
Says Richard Tren, director of Africa Fighting Malaria, “Donors need to decide whether they are going to save lives or simply do what is politically correct.”
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