The New York Times magazine did an exhaustive feature on DDT and malaria control a few years ago. The full article is here.

Some facts in the article contradict assumptions some commenters have been making. For example, bed nets only protect against mosquitos if they've been sprayed with insecticide. It's the insecticide, not the net, that's important. Further, the cost of spraying DDT is about $1.70 per person per year, not $12.

"Just make a vaccine!" is a cry we've been hearing for many years, and it's an easy one to make, because it devolves effort from an involved and activist citizenry to a few scientists in labs. Consciences clear, environmentalists can move on. The only real solution to the malaria problem will come with the elimination of the species of mosquitos that carry the disease. Olivia Judson has proposed such a scheme involving "knockout" genes that would induce fatal defects in mosquitos after the genes became widely prevalent in those populations. Another proposal involves irradiating male mosquitos to render them infertile, and then airdropping them in malaria-prone regions. Since female mosquitos only mate once (even if the mating is unsuccessful), the number of larvae forestalled by this is enormous, and could lead to extinction very quickly. Mosquitos have killed more humans than all the wars in all of history. We drive thousands of species to extinction each year accidentally; I'd judge it a tough argument that we can't eliminate one particularly deadly species on purpose.

And now that I've contributed that much serious input, let me just say that if we'd disregarded Rachel Carson's warnings about a "Silent Spring," we'd have been spared the threat of both malaria and avian flu. A silent spring is a disease-free one.

The application of DDT in combination with other forms of vector control is imperative in saving lives in the future but it is highly unlikely that the malaria mosquito can be led to extinction. The correct approach ought to be the reduction in the number of mosquitoes to such a level that there is a break in transmission of the parasite. The pursuit of the extinction of mosquito may be tempting as a decisive solution but the odds are that it is virtually unattainable.

1. Although sterile insect techniques (SIT) can be a very useful tool in controlling certain types of pests, they never lead to complete extinction.

2. There are four different malaria parasites with vastly different lethalities -- the type of malaria endemic in Sub-Saharan Africa is deadliest to chldren under the age of five but actually doesn't kill many adults (though it makes them quite sick, and repeatedly). This is not to deny the tremendous human toll of the disease; it is only to point out that it is hard to say exactly how many lives are lost (or saved) without specifying exactly which strain of parasite one is discussing.

3. A reasonable estimate of the material cost of IRS (interior residual spraying) vs. LLN (long-lasting insecticide treated nets) was included in a relatively recent Ugandan Ministry of Health report. That report estimated the 6-month material cost of DDT at around $2 per household, while the cost of a LLN (which lasts about 4 to 5 years) was about $6. IRS needs to be repeated every 6 months, and the cited cost is only for the insecticide itself and does not include the cost of spraying. It is generally acknowledged that the logistical cost of arranging an army of sprayers who can visit an area twice a year is considerable. The distribution cost of a LLN is quite a bit lower: basically, an entire truckload of LLNs can be delivered by one man while that same man with a sprayer can cover about eight dwellings per day. IRS can be especially effective when malaria is episodic and short-term protection (for, say, one season) is needed in order to "break" an epidemic. WHO has always supported this particular use of IRS. In Africa, LLNs work especially well because even one net in a household can be targeted to the children under age five.

I am not inconsistent on the question of whether the WHO has changed their position. Here is my comment from your previous post:

The WHO (World Health Organization not WTO) recently decided to place more emphasis on DDT spraying but has always supported its use and in any case DDT is not a magic bullet against malaria.

I don't understand how you could read that as an assertion that there had been no change in their position on DDT.

I am glad that that you have corrected some of your errors but I am perplexed that you continue to claim that "opposition to DDT spraying by many organizations caused a very large number of needless deaths from malaria." In fact, restrictions on spraying DDT have, on net, saved many lives by preventing the development of resistance to DDT.

As for the economics of malaria control interventions,the most up-to-date analysis I am aware of was conducted by the Disease Control Project. They found that the cost per DALY (Disability-Adjusted Life Year) was $11 for deltamethrin-treated nets, $9 for DDT in areas of seasonal transmission of malaria and $18 for DDT in areas of constant transmission. There are some large uncertainities on these numbers, but they certainly suggest that the best policy is nets in areas of constant transmission and DDT in areas of seasonal transmission, which was the WHO's previous policy. The new policy of DDT everywhere seems to lack scientific support. The new policy was adopted for political reasons (to get the support of the US), not scientific ones.

Milk for free cites Tina Rosenberg's NYT article "What the World Needs Now Is DDT". Unfortunately the article is inaccurate and misleading.

What the world needs now is not DDT but money to combat malaria. It doesn’t matter that much whether it is spent on bed nets or spraying with DDT or other insecticides—they all work and the costs don’t differ that much (and DDT isn’t necessarily the cheapest solution). Rosenberg makes it look like that all that is preventing malaria from being controlled is environmentalists’ prejudices against malaria and that just isn’t true.

The concept of Food Triggers in health science is not new. Simply put, a food trigger can be any food that causes or triggers a reaction or change in the body.

When it's malaria, it's Africa! So we better leave these old fashion approaches. We will never solve the African problem with DDT or even a vaccine without a political change in Africa. I am from Angola and there they say malaria is a problem of urbanism! In fact, those who live in "slum villages" are more likely to get ill than those who live in better places. Personally i believe DDT could solve part of the problem, but better governance is the key, because malaria is really simple to be treated and avoided.