GM Mosquito Could Fight Malaria

qw0ntum writes "The BBC is reporting that a genetically modified (GM) variety of mosquitoes could be effective in combating the spread of malaria to humans. These GM insects carry a gene that prevents them from being infected by the malaria parasite and has the added benefit of providing a fitness advantage to the mosquitoes. From the article: 'In the laboratory, equal numbers of genetically modified and ordinary wild-type mosquitoes were allowed to feed on malaria-infected mice. As they reproduced, more of the GM, or transgenic, mosquitoes survived. According to the researchers, whose results appear in Proceedings of the National Academy of Sciences journal, after nine generations, 70% of the insects belonged to the malaria-resistant strain. [...] The modified mosquitoes had a higher survival rate and laid more eggs.' This has major implications for the billions of people living in areas with endemic malaria. The question in my mind, though, is what effects on the ecosystems of these areas will replacing an organism low on the food chain with a GM version? Between the news we saw last week and biomagnification, could this wind up substituting one problem for another?"

Comments

One should pay attention to adaptation

[Ichoran]

The PNAS study shows an additional effect that isn't quite covered by the blurb above: heterozygous mosquitos (those with only one copy of the gene) are more fit than homozygous mosquitos (those with two copies). This means that there is pressure to retain a large number of heterozygous individuals, which means there will be a mixed population of transgenic and non-transgenic mosquitos. While this might help humans in the short run (a smaller fraction of the mosquitos you're bitten by would carry Plasmodium, the malaria parasite), in the long run it pretty much guarantees that people will still get malaria, and the malaria parasite will have lots of opportunities to develop resistance to the introduced gene.

So it's a nice idea--and it would be more effective than releasing low-fitness transgenic mosquitos--but it's not quite there yet.

As to fears of biomagnification, mosquitos generally don't deal with stress by producing toxic compounds (unlike plants, who only have that option), and the transgenic protein is a protein and hence digestable. So it's very unlikely that there would be anything to magnify. Instead of worrying about creating toxic mosquitos, we should make sure that when we actually hit Plasmodium with drugs and modified mosquitos and so on, that we make things so difficult for it that it really devastates its population. Otherwise, we're just conducting a transgenic-mosquito-resistant Plasmodium breeding experiment. (Plasmodium has already developed at least some resistance to most common anti-malarial drugs).

Better mosquitoes

[Mark_MF-WN]

Well, the USA has already been doing the next best thing -- eradicating certain insect species by engineering worse versions. There are about a dozen noxious parasites that were wiped out in most of North and South America by introducing (literally) millions of sterilized males into the ecosystem for a few years in a row. The sterile males grow larger and healthier than their virile counterparts (on account of not needing to produce any sperm), and so females breed with them preferentially. It's extraordinarily effective. Ever seen a screw-worm fly infection? Extinctions aren't always a bad thing... Actually, I think that's why the USA no longer has any native reservoirs of Malaria. I know that the American southeast is theoretically an ideal Malaria-zone, and did indeed have Malarial reservoirs a few centuries ago.

The only reason it hasn't been applied to malarial mosquitoes in Asia and Africa is that there are something like two dozen species to deal with, and each one would require its own entire eradication program and on a much larger scale (it turns out that Asia is really big). That's what's cool about this idea -- it's a slightly more subtle variant of what the US has been doing for decades now. It's just more targetted -- eliminating the particular genes that allows malaria to be carried rather than the entire insect. And it avoids the need to breed millions or billions of the bugs yourself and releasing them every year -- the insects do it all for you, as long as the new alleles really are favourable.

Very clever -- IF it actually works. Goodness knows the people in the third-world don't need to have Malaria keep kicking them while they're down. Any chance to reduce the size of Malaria's bootprint is definitely worth a serious look.