Death By Mosquito

DARLENE A. MURAWSKI / PETER ARNOLD
THE CULPRIT: The female mosquito needs blood to produce eggs. It transmits malaria parasites when it bites again

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The full three-day course of treatment with artemisinin-based combination therapy costs from $1 to $10 a person, depending on whether it is purchased in the public or private sector. Unfortunately, that's at least 10 times the price of current, albeit ineffective, treatment programs. Most impoverished African governments simply cannot afford to foot the entire bill for combination therapy and the training required to give it, and the same holds true for the majority of their private citizens, many of whom already spend a third of their income on malaria treatment.

Although nearly every developed country and most major international aid organizations have said they are ready to help finance artemisinin-based treatment in Africa, that support has not always been forthcoming. Some health experts believe a report on artemisinin-containing therapy due out from the U.S. Institute of Medicine this week will dissolve any lingering reluctance.

And what about prevention? Many African countries are working to sell or distribute low-cost insecticide-impregnated mosquito nets. These function as traps for mosquitoes, which are attracted by the carbon dioxide that sleepers exhale and are then killed by the insecticide. The nets are portable, so they can be taken along by their owners if they need to move. In villages where at least 80% of pregnant women and children under age 5 sleep beneath insecticide-impregnated mosquito nets, the rate of illness for all residents has dropped dramatically. Unfortunately, only 1% or 2% of people in malarial zones sleep under mosquito nets. Also, most nets need to be retreated every six months, and they are less effective in areas where anopheles mosquitoes bite all day long instead of just at night.

A more controversial but nonetheless effective method of reducing transmission is to spray DDT inside huts and other buildings. Intriguingly, DDT is often better at repelling mosquitoes than killing them. This requires much less pesticide than was once sprayed on crops and swamps. Indeed, if DDT had been used only for medicinal purposes, it might never have acquired its toxic reputation. An international antipesticide treaty that took effect last May makes an exception for the use of DDT in malarial areas, but some health experts are worried that the bureaucratic headache of applying for an exemption will limit the effectiveness of DDT.

Recent experience in South Africa shows just how well DDT can work. In 1996 the South African government, under pressure from international and domestic environmental groups, decided to phase out its use of DDT in residential spraying and rely instead on pesticides containing pyrethroid chemicals. Unfortunately, it turned out that many anopheles mosquitoes in South Africa were resistant to pyrethroids. The number of cases of malaria, which had been hovering between 8,000 and 13,000 a year, grew steadily worse, and by the year 2000 it had reached 64,000 cases, with 423 deaths. When the government reintroduced DDT spraying in the middle of that year, the results were dramatic. The number of cases fell almost immediately. By the end of 2001, when doctors began treating their patients with Coartem, a single, multidrug pill that includes an artemisinin derivative, the number of cases had been cut in half. In 2003 the number of deaths was down to 146.