The science and politics of DDT
Arguments about DDT have been going on for a long time in the blogosphere and similar circles. These debates typically involve a confusion between two unrelated issues
* The bogus story, popular in rightwing circles, in which the US ban on agricultural use of DDT, inspired by Rachel Carson, is morphed into a global ban on DDT, bringing to an end a previously successful compaign to eradicate malaria
* The real disputes, among malaria experts, about the relative merits of insecticide-treated bednets and spraying of house walls, and of DDT and alternative insecticides.
Now the two have coincided in the real world, with effects that may or may not be good. WHO recently appointed Arata Kochi as head of its malaria program. Kochi, who previously worked on the Stop TB initiative, has a reputation as a headkicker, but also as someone who gets things done. It’s worth noting that, while this kind of reputation is sometimes well-earned, there are often cases where the supposed accomplishments turn out be ephemeral or non-existent (remember ‘Chainsaw Al’ Dunlap, for example?).
Kochi has decided to shake up the ‘malaria community’ and an obvious line of attack is to line up with those among its critics who favor a bigger role for DDT. He’s just made a big announcement of a shift in favor of DDT, coinciding with the resignation of the WHO’s leading expert on insecticide spraying.
Reading the announcement and the NYT closely, the change in reality is much less than in rhetoric. Of the 17 African countries that now use interior spraying, 10 already use DDT, and it will almost certainly turn out that some of those who don’t have good reasons for choosing other pesticides (resistance, or harm to helpful insects that prey on pests in roofs for example).
And the substantive change in WHO guidance is much less dramatic than the rhetoric would suggest. WHO is now recommending the use of indoor residual spraying (IRS) not only in epidemic areas [as in the past] but also in areas with constant and high malaria transmission, including throughout Africa.
It’s far from clear that the change is backed up by a scientific analysis of the relative cost-effectiveness of the options. But, as with all the fads and fashions in areas like this, cost-effectiveness is not necessarily the most relevant criterion. The US appears willing to put in a substantial amount of extra money, and the US wants to push DDT. So, it’s probably better to please the donors, than make a stand on the science and risk losing the money.