Thursday, March 24, 2005

# Posted 5:57 PM by Ariel David Adesnik  

DDT REDUX: Many thanks to all of you have written in with links and opinions about the relationship between DDT and malaria in the developing world, a subject about which I still have much to learn.

Before getting to the more complex issue of whether DDT can prevent malaria, I'd like to address the straightforward factual question of whether there is currently a ban on the use of DDT. Nick Kristof suggested that such a ban exists. Citing the Malaria Foundation International (MFI), Tim Lambert responded that Kristof was simply wrong. The Belmont Club (Hat tip: TB) responds, however, that MFI wouldn't be celebrating its efforts to prevent a ban unless there had been a very strong push by environmentalists to impose one.

This brings us to the issue of whether there is a sort of implicit or de facto ban on the use of DDT that results from European pressure on the developing world. Blogger CR points to this article as an example of how the EU can impose such a ban by threatening to close its markets to nations such as Uganda that want to use to DDT to stop the spread of malaria. Moreover, according to RF,
While there is no international ban on DDT use, western aid agencies often provide a large percentage of the anti-malaria budgets of many poorer nations. These agencies are opposed to using DDT for malaria prevention, probably due to bans on its use in their own countries. Without this funding to support DDT spraying, these nations can not afford it and are forced to adopt less cost effective measures encouraged by western agencies.
The reluctance of donors to fund DDT spraying is also cited as a major obstacle by Tina Rosenberg, whose NYT Magazine article on malaria and DDT seems to have influenced Nicholas Kristof.

When it comes to the issue of whether spraying is effective, I'd like to thank JZ of Africa Fighting Malaria (AFM) for sending in a long letter on this subject. As JZ points out, AFM is prominent advocate of increasing the use of DDT, so hers should not be considered an impartial opinion. JZ is still confident, however, that there is enough evidence on her side to overcome potential concerns about bias. As she points out,
DDT is a powerful spatial repellent, [and] this characteristic of it keeps mosquitoes from entering the house. Second[,] for the mosquitoes that do enter the house, DDT is a powerful contact irritant.

Anopheles mosquitoes like to hang out on the walls for a bit and groove before biting. When they come into contact with DDT, they [become] tetchy and some are so irritated by it that they will exit the house without biting. Third[,] DDT is toxic to mosquitoes, and will kill some preventing the from spreading malaria further.
JZ acknowledges that mosquitos have often developed resistance to DDT and that this is a serious challenge for disease prevention efforts. Nonetheless, DDT has scored some important victories over malaria even in recent times:
The classic example is [the] experience of South Africa in the late 1990's, where the reintroduction of DDT combined with the introduction of Coartem as a first treatment dropped malaria rates by 80% in one year in KwaZulu Natal province. South Africa's experience has been duplicated in Zambia, where an area using [indoor residual spraying] dropped malaria rates by 50% one year and another 50% the next.
Sounds good to me. But once again, I am only beginning to learn about this issue so my opinions are very much open to new arguments evidence.

For those interested in more information about malaria and DDT, reader CH recommends this article from the Washington Monthly and reader NJ says he attended an informative lecture by Paul Driessen, author of Eco-Imperialism: Green Power, Black Death.

Happy hunting.
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