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Our mosquitoes are pests; this type is a grim reaper.
O death, where is thy sting? Far too often it comes at the end of a mosquito’s proboscis. The worst mosquito-borne disease, malaria, infects about 400 million people worldwide each year (90 percent in sub-Saharan Africa) and kills about 1.3 million of them. Compare that to the histrionics we’ve suffered over avian flu, which as of 2 April had infected 25 people and killed 12 this year. Or SARS, which killed 774 people worldwide before petering out.
Unfortunately a useful vaccine is way off and environmentalists have befriended the mosquitoes by opposing spraying with DDT, practically comparing its use to that of Zyklon B at Auschwitz. ”These people are totally prepared to sacrifice millions if not billions of poor people for their idea of a world more in tuned with nature ” says Don Roberts, professor of tropical public heath at the Uniformed Services University of the Health Sciences in Bethesda, Maryland. And while DDT advocates are finally making gains, it’s bed nets that are politically correct – if not particularly effective.
So it’s great that scientists at the Malaria Research Institute at Johns Hopkins University in Maryland have genetically built a better mosquito, which is to say that it still bites and leaves an itchy welt but cannot spread malaria. The idea is that large numbers of engineered mosquitoes would be released in malaria-ridden areas so they could interbreed with wild ones. Over time more and more of the mosquito population would carry the new trait.
This is not a new concept. Various types of harmful male insects are irradiated to make them sterile, and then released to interbreed with fertile bugs and thereby reduce the overall population. The problem with sterilization, though, is that it often weakens the insect and gives fertile wild competitors the advantage in breeding.
But these biotech mosquitoes actually have a breeding advantage. Mosquitoes infected with the malaria parasite, Plasmodium, don’t die from it but are weakened. The engineered ones, being immune, can drink their natural cousins under the table. ”When fed on Plasmodium-infected blood, the transgenic malaria-resistant mosquitoes had a significant fitness advantage over wild-type, ” the researchers remarked in the Proceedings of the National Academy of Sciences.
Thus, in an experiment in which the engineered mosquitoes began as 50 percent of the laboratory population, over the course of nine generations (several months) they grew to become 70 percent of the population.
Richard Tren, director of the group Africa Fighting Malaria, with offices in both South African and Washington, D.C., nevertheless cautions against over-enthusiasm.
The mosquito work ”is great research, ” he told me, but notes that what works beautifully in the lab may not work in the field for reasons we can’t even guess at now. Further, he observes, ”The research was done on a mosquito mostly found in Southeast Asia, Anopheles stephensi, and not in the more aggressive sub-Saharan African mosquito that spreads malaria called Anopheles gambiae. ” He also worries about whether it would be possible to introduce a large enough number of the engineered mosquitoes to squeeze out the natural population.
But his greatest fear is that people ”will get the idea this is a magic bullet. ” Even if all goes well, it may not be ready for prime time for ten years or more – or to measure it another way, 13 million deaths.
People used to run behind DDT fogging machines. Now they sit in front of the tube stuffing their faces. Guess which is more dangerous?
Tren calls for a holistic approach in fighting the disease. That includes full rehabilitation of DDT; spraying it everywhere malaria is endemic.
”We’re inching towards a vaccine, ” he told me, one that also will be genetically engineered. But he notes malaria vaccine research has been going on for many decades and ”it seems like we’re always just seven years away. ” Says Tren, ”During the time we’re waiting on this mosquito research it could be distracting from things that are already proved. This is a really complex disease and we need a range of interventions. ”
Don Roberts agrees. The engineered mosquito ”is interesting research and an advancement of the science, ” he says. But among the problems is that even within anopheles gambiae there are an almost infinite genetic variety of mosquitoes. ”A population of mosquitoes is a result of evolutionary force, ” he told me. ”Just go downstream and you’ll find a population that is different. ”
He supports the biotech mosquito and vaccine research but says the emphasis for now must be insecticides, to include DDT but not to exclude developing others that may be far more effective. DDT makes for a great repellent when sprayed on house walls, he explains, but is actually not very toxic – exactly the opposite of what green groups would have us think.
”If you look at the amount of money going into a vaccine, it’s probably in the billions ” Roberts says. ”Look into what’s gone in to drugs to treat malaria and that’s probably in the tens of billions. Then there’s the environmentalist fight against DDT, which has probably also consumed billions of dollars, ” he notes. ”But how much is being spent on an insecticide that would be less controversial and yet could be more effective at killing mosquitoes than DDT? Zero. ”
He adds, ”For me, it’s a failure that’s almost breathtaking. ”
So bring on the mosquito research and vaccine research. But for now and in the indefinite future the best weapon we have against this vicious mass-murderer of a disease is old-fashioned insecticide. Low-tech works now and we cannot afford to wait.