|
|||||||
|
|
The year 2000 was a time of plague for the South African town of Ndumo, on the border of Mozambique. That March, while the world was focused on AIDS, more than 7,000 people came to the local health clinic with malaria. Today, malaria has all but vanished in Ndumo. As malaria surges once again in Africa, victories are few. But South Africa is beating the disease with a simple remedy: spraying the inside walls of houses in affected regions once a year. Several insecticides can be used, but South Africa has chosen the most effective one. It lasts twice as long as the alternatives. It repels mosquitoes in addition to killing them, which delays the onset of pesticide-resistance. It costs a quarter as much as the next cheapest insecticide. It is DDT. To Americans, DDT is simply a killer. Ask Americans over 40 to name the most dangerous chemical they know, and chances are that they will say DDT. Dichloro-diphenyl-trichloroethane was banned in the United States in 1972. The chemical was once sprayed in huge quantities over cities and fields of cotton and other crops. Its persistence in the ecosystem, where it builds up to kill birds and fish, has become a symbol of the dangers of playing God with nature, an icon of human arrogance. Countries throughout the world have signed a treaty promising to phase out its use. Yet what really merits outrage about DDT today is not that South Africa still uses it, as do about five other countries for routine malaria control and about 10 more for emergencies. It is that dozens more do not. Malaria is a disease Westerners no longer have to think about. Independent malariologists believe it kills two million people a year, mainly children under 5 and 90 percent of them in Africa. Until it was overtaken by AIDS in 1999, it was Africa's leading killer. One in 20 African children dies of malaria, and many of those who survive are brain-damaged. Each year, 300 to 500 million people worldwide get malaria. During the rainy season in some parts of Africa, entire villages of people lie in bed, shivering with fever, too weak to stand or eat. Many spend a good part of the year incapacitated, which cripples African economies. A commission of the World Health Organization found that malaria alone shrinks the economy in countries where it is most endemic by 20 percent over 15 years. There is currently no vaccine. While travelers to malarial regions can take prophylactic medicines, these drugs are too toxic for long-term use for residents. Yet DDT, the very insecticide that eradicated malaria in developed nations, has been essentially deactivated as a malaria-control tool today. The paradox is that sprayed in tiny quantities inside houses -- the only way anyone proposes to use it today -- DDT is most likely not harmful to people or the environment. Certainly, the possible harm from DDT is vastly outweighed by its ability to save children's lives. Part of the reason for DDT's marginalization is that its delivery method, house spraying, doesn't work everywhere. Insecticide sprayed inside houses repels mosquitoes -- and kills those that do make it indoors and perch on walls -- for several months. Since most mosquitoes bite at night, when people are likely to be indoors, the spray reduces the number of times people are bitten. If around 80 percent of houses are covered, spraying protects everyone, as the bites that take place will be from mosquitoes less likely to have bitten an infected person. But house spraying is only effective against mosquitoes that bite indoors -- not all do. It also requires a government capable of organizing, training and equipping sprayers, which is beyond the reach of some countries. Even when spraying is possible, though, developed nations don't want to pay for it. Instead, the malaria establishment in developed nations promotes the use of insecticide-treated nets that people can buy to hang over their beds. Treated bed nets are indeed a useful tool for controlling malaria. But they have significant limitations, and one reason malaria has surged is that they have essentially become the only tool promoted by Western donors. Today, westerners with no memory of malaria often assume it has always been only a tropical disease. But malaria was once found as far north as Boston and Montreal. Oliver Cromwell died of malaria, and Shakespeare alludes to it (as ''ague'') in eight plays. Malaria no longer afflicts the United States, Canada and Northern Europe in part because of changes in living habits -- the shift to cities, better sanitation, window screens. But another major reason was DDT, sprayed from airplanes over American cities and towns while children played outside. In Southern Europe, Latin America and Asia, DDT played an even more prominent role in controlling malaria. A malaria-eradication campaign with DDT began nearly worldwide in the 1950's. When it started, India was losing 800,000 people every year to malaria. By the late 1960's, deaths in India were approaching zero. In Sri Lanka, then called Ceylon, 2.8 million cases of malaria per year fell to 17. In 1970, the National Academy of Sciences wrote in a report that ''to only a few chemicals does man owe as great a debt as to DDT'' and credited the insecticide, perhaps with some exaggeration, with saving half a billion lives. From the 1940's to the late 1960's, indoor house spraying with DDT was tested all over Africa. It was least effective in the lowland savannas of West Africa, but even partly successful programs provided considerable health improvements. And in other parts of Africa, DDT reduced the infant mortality rate by half and in some places wiped out malaria completely. The move away from DDT in the 60's and 70's led to a resurgence of malaria in various countries -- Sri Lanka, Madagascar, Swaziland, South Africa and Belize, to cite a few; those countries that then returned to DDT saw their epidemics controlled. In Mexico in the 1980's, malaria cases rose and fell with the quantity of DDT sprayed. Donald Roberts, a professor at the Uniformed Services University of the Health Sciences in Bethesda, Md., has argued that when Latin America stopped using DDT in the 1980's, malaria immediately rose, leading to more than a million extra cases a year. The one country that continued to beat malaria was Ecuador, the one country that kept using DDT. In the few countries where it is used today, DDT is no longer sprayed from airplanes, and no country admits to using it as an insecticide for crops -- although there are probably cases where it is diverted for agricultural use. Its only legitimate use is inside houses. Roberts said that the quantities used for house spraying are so small that Guyana, to take one example, could protect every single citizen of its malarious zones with the same amount of DDT once used to spray 1,000 acres of cotton. ''The negative environmental effects of DDT use that led to its banning were due to massive, widespread agricultural use,'' says a fact sheet published by Usaid (no fan of the chemical). ''Spraying limited amounts of DDT inside houses is considered unlikely to have major negative environmental impact.'' What about DDT's impact on the people inside the houses? The most serious evidence of DDT's harm to humans are a few studies showing that higher levels of DDE (the form DDT takes when it metabolizes) in a mother's blood is associated with premature birth and shorter duration of breast-feeding. But other studies have found no such associations. There was suspicion that DDT causes breast cancer, but study after study has found no connection. In general, DDT is feared for its effect on the environment, not on humans. It has been used on such a huge scale over the last 50 years that it is reasonable to think that if it had any serious effect on human health, we would know it by now. Public opinion is so firm on DDT that even officials who know it can be employed safely dare not recommend its use. The significant issue is whether or not it can be used even in ways that are probably not causing environmental, animal or human damage when there is a general feeling by the public and environmental community that this is a nasty product. You'd have to explain to everybody why this is really O.K. and safe every time you do it, so you go with the alternative that everyone is comfortable with. People get upset about DDT and merrily go and recommend an insecticide that is much more toxic. The lack of political interest in malaria has been a very important factor in the decline of house spraying and rise of bed nets. Bed nets follow the fashion in development assistance today: bypass the government and work through private sector, nongovernmental groups and with the affected people themselves. People can buy nets in a store for $2 to $10, or their subsidized or even free distribution can be integrated into other health programs, like vaccination days. Bed nets are an exciting and important form of mosquito control. But they have major drawbacks. Even a few dollars is still too much money. People surveyed in rural Africa about what they would like to buy listed a bed net as only the sixth product on their wish list. The first three were a bicycle, a radio and, most heartbreakingly, a plastic bucket. The price is also kept artificially high because most countries, shamefully, still tax bed nets. And until nets with long-lasting insecticide can be widely distributed, bed nets need regular retreatment. It is insecticide that protects, not the net, and the insecticide wears off without people knowing it. Both bed nets and house spraying can be effective, and studies comparing costs differ on which is cheaper. For the world malaria establishment, however, one huge difference is that with house spraying, the central government -- and therefore donors -- bear the cost. Financing repeated rounds of spraying, donors argue, is not sustainable. Mozambique is now doing house spraying successfully and cheaply without a national army of sprayers and a fleet of S.U.V.'s. Mozambique hires a few people in each community and gives them two weeks of training and the materials they need. Those sprayers then walk from house to house, spraying each one twice a year. It helps save on transport costs, and the fact that sprayers come from the community makes it a lot more credible in terms of people accepting what is done in their households. Mozambique, because it depends on Western donors, uses a more expensive insecticide. But if it used DDT, it could protect people for $1.70 per person per year. There are other ways to control mosquitoes. Parts of India, for example, are having success stocking mosquito-breeding ponds with guppies, who eat mosquito larvae. But India's ingenious strategy would not work in Africa, where mosquitoes breed in cattle hoofprints during the rainy season. Malaria must be more than simply a line item in the health budget. Malaria kills tourism and foreign investment. It greatly reduces human intelligence and productivity and lessens agricultural yields. Against these costs, a nation's business sectors and economic ministries should willingly join the fight -- and donors must begin to think of malaria control as an unusually cost-effective antipoverty program. South Africa's success is inspiring another look at DDT around the continent. Uganda, Kenya and other places are now examining whether it could work in their nations. If it could, donors should encourage it. DDT is a victim of its success, having so thoroughly eliminated malaria in wealthy nations that we forget why we once needed it. But malaria kills Africans today. Those worried about the arrogance of playing God should realize that we have forged an instrument of salvation, and we choose to hide it under our robes.
What the World Needs Now Is DDT
Are
multivitamins a Must?
|
