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R.I.P., DDT: Now, how to bury malaria?


After the publication of Rachel Carson's explosive book Silent Spring in 1962 launched the environmentalist movement, DDT - a demonstrably, even uniquely, effective anti-mosquito agent - was banned in the 1970s, The ban may well have brought the bald eagle back from the brink of extinction.

It may not have been so kind to people. Malaria, caused by a mosquito-borne parasite, made a steady comeback in many parts of the world where it had been on the road to eradication. (In 2006 the World Health Organization, in a major policy shift, once again backed DDT's use for eliminating the scourge.)

A flurry of studies and commentaries (1, 2, 3, 4, 5, 6) on the current global malaria situation were published in The Lancet today. That situation is not pretty.

Because malaria has by and large been eliminated in developed countries, we don't think about it much. Think about this: the disease kills more than 860,000 people annually. And that's a drop in the bucket compared with the estimated 247 million - million! - separate cases contracted every year by living, breathing human beings, more often than not children.

At this moment, the closest thing to an effective malaria vaccine is still in development and appears to be only 50 percent effective. Better than nothing, but not great.

DDT is not mouth-wash. Sprayed in excess, as it was back in the early post-war years, it piles up and disrupts the environment. Used carefully, it has no equal as a pesticide. At this point, of course, a heavyweight DDT offensive against malaria-carrying mosquitoes is unlikely to fly very far or very fast.

But, back in 1990, Stanford immunologist Leon Rosenberg, PhD, who died in July of this year, had an unconventional idea for ridding humanity of the malaria parasite:

Because this organism undergoes numerous changes in the course of its life cycle, the development of a malaria vaccine is a challenge. Rosenberg's concept was to produce a vaccine not against malaria, but against the mosquitoes carrying it. Injecting ground-up ticks into cattle had been shown to raise a strong enough immunological response in the ruminants to be lethal to ticks; Rosenberg reasoned that the same procedure - injecting humans with ground-up mosquitoes - would produce an analogous result. While this wouldn't prevent contracting malaria from a mosquito that carried it, it would - by killing the mosquito - stop it from infecting anyone else. Such a vaccine, were enough people to receive it, could over the long run substantially reduce the transmission of the disease to humans. Rosenberg, however, was unable to corral the enormous resources necessary to test and develop such a vaccine, and the idea went unfulfilled.

Maybe it's time to take that idea seriously.

Photo by Wellcome Images

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