Altered Mosquitoes May Save Humans From Malaria

A study released this week shows progress in the development of a malaria-resistant mosquito. Robert Siegel talks with David O'Brochta, professor of biosystems research at the University of Maryland. O'Brochta studies the transmission of human disease through insects.

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MICHELE NORRIS, host:

From NPR News, this is ALL THINGS CONSIDERED. I'm Michele Norris.

ROBERT SIEGEL, host:

And I'm Robert Siegel.

Malaria kills hundreds of thousands, perhaps a few million people a year, most of them children in Sub-Saharan Africa. It's a disease caused by a parasite that migrates from host to host via mosquito. The mosquito bites one person or animal with malaria, takes the parasite on board, flies off to another victim, bites and implants the parasite, which proceeds to multiply like crazy, sickening if not killing its victims.

Malaria has been plaguing us so long no fewer than four Nobel Prizes have been given for research about it, one as early as 1902. Well, now insect geneticists at Johns Hopkins University have come up with a modest step toward a genetic solution. In the past, these scientists have developed a genetically modified malaria resistant mosquito, and now they've shown that that mosquito is a hardy mosquito.

David O'Brochta is professor at the University of Maryland's Biotechnology Institute. And Dr. O'Brochta, what's so important about finding that this genetically modified malaria-resistant mosquito is a strong mosquito?

Dr. DAVID O'BROCHTA (Biotechnology, University of Maryland's): What these investigations have shown is that when we make those modifications with the mosquito, we're actually not making the mosquitoes worse off by these genetic modifications, but we're actually making them better off in some ways.

SIEGEL: So that if at some point such mosquitoes were let loose in nature, they would actually thrive and multiply and become dominant in the population of mosquitoes?

Dr. O'BROCHTA: The basic idea is that the kinds of changes that insect geneticists are trying to make in mosquitoes could actually help propel the use of these changes into nature and not slow them down. And that's one of things that insect geneticists has been worried about, is that the genetic changes they've been making in the laboratory, although they might confer certain characteristics on the mosquito that are desirable, like being resistant to malaria, those genetic changes may actually weigh the insect down, if you will, with changes that would make it difficult to get those genetic changes out into nature to all the mosquitoes out into a population.

SIEGEL: Now as scientists genetically work on redesigning the mosquito, we assume the mosquito is still going to bite people. This particular mosquito work, I gather, was done with a malaria strain that affects mice, not humans. But it would still bite animals or people. Would still take on board the parasite or would it never ingest it? What's different after the mosquito is modified?

Dr. O'BROCHTA: Mosquitoes aren't just flying syringes for malaria transmission. The parasite actually goes through a rather elaborate developmental cycle within the mosquito. And the changes that these investigators have made result in that development of the parasite being completely blocked. So the changes they've made in the mosquito actually result in the parasites being killed within the mosquito. They've essentially immunized the mosquitoes against malaria.

SIEGEL: And in order to effectively immunize a human population, one way to go about doing that is to be immunized all the mosquitoes against it.

Dr. O'BROCHTA: Well, because malaria is so dependent upon the mosquito for its transmission there are a number of ways one can think about attacking it as a problem. One could think about preventing people from getting bitten by the mosquitoes, and we do that. We could think about giving people drugs to kill the parasites within the humans. Or we could think about focusing on the mosquito. And certainly we've done this in the past. We've tried to kill mosquitoes with insecticides, tried to break that transmission cycle.

Genetically modifying them is a way which doesn't think about removing the mosquitoes from the environment, but just changing them in a way which is most important to humans, and that is the thing no longer become disease transmitters.

SIEGEL: Well, Professor O'Brochta, thank you very much for talking with us about it.

Dr. O'BROCHTA: You're quite welcome.

SIEGEL: David O'Brochta, professor at the University of Maryland's Biotechnology Institute.

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