John Tierney at the NY Times has a blog on a topic I wanted to introduce but I figured people might want to just check out his blog here.
In case people did not see it, scientists at Johns Hopkins just announced they had created a mosquito strain that is resistant to infection by Plasmodium and thus does not transit malaria (it is a mouse model so they do not have this for humans at this point). The key to their study is that their mosquito is healthy, whereas previous attempts to create mosquitoes that are resistant to malaria infection have been sick. Thus, the hope is that with healthy mosquitoes, they can be introduced into a population and the resistance gene will spread rather than be wiped out by negative selection.
I really love this research area because it truly is an applied use of evolutionary biology and population genetics. If you want some gene (natural or unnatural) to spread through the mosquitoes of the world, you have to understand evolution in general and for mosquitoes in particular. Plus, there are many possible ways to do this --- and it is interesting to see the research in different ways. For example, there are some projects to try to introduce particular Wolbachia strains into mosquito populations. Wolbachia would serve as a sort of birth control for mosquitoes.
The most problemmatic part of the current study unfortunately is not the science per se. It relates to the fact that the way they made the mosquitoes resistant was through genetic engineering, not breeding. And such a GMO mosquito carries all the same fears and issues as GMO foods. The key question is - suppose they can create a version of mosquito that will do the same thing for human malaria - should such GMO mosquitoes be released? And if they are released, will Europe and Asia all of a sudden create an uproar? And if you were offered to bowls of soup, one that a non GMO mosquito was in and one that the GMO was in, which would you eat?
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Just got this press release by email. I am sick of receiving dozens of unsolicited press releases, especially those in topics not related ...
I'd have no problem with it, but I'd imagine lots of people would. After all, "golden rice" (the more nutritious strain of rice that could help fight malnutrition in the third world) has been held back for the simple reason that it's genetically engineered.
ReplyDeleteI think many people conflate technology with goals. Certainly many companies, such as Monsanto, hope to use genetic engineering to make profits even at the expense of consumers and farmers, but there's no reason why genetic engineering couldn't be used for more socially constructive goals like ending malaria and malnutrition. It's no different from computers; computers can be used to aid a police state find and jail dissidents, but they can also be used as tools of democracy.
Hi Jonathan. Nice blog. I like the 'in your soup' paragraph overall, but I thought a quick comment appropriate. The 'birth control' approach mentioned in your article is non-transgenic. The sterility is caused by naturally occurring bacteria that are moved artificially between mosquitoes.
ReplyDeleteSorry - yes I meant to say that about your project. Yet another reason I like it.
ReplyDeleteI used to work on malaria in a previous life and this approach has been kicking around for years. Something similar was done to wipeout screwworm, a veterinary pest, in the southern U.S. decades ago -- they irradiated male flies to make them sterile and released them so that they would compete with normal, fertile males and cause the population to crash.
ReplyDeleteAnyway... I think the other problem that this idea tripped over is that the population dynamics of mosquitoes is such that the strategy just doesn't work out as well as it did with the screwworm fly.
Ironically, there are very good ways to control mosquitoes (DDT spraying of houses, treating or removing water sources, window screens, bednets) but they all require funding and more important, the logistical/organizational capacity to put them into effect.
Well, theoretically the Wolbachia thing is different (Dobson would be better able to say why). The Wolbachia are better than irradiation, because they can spread into the population and therefore be an infectious form of sterility.
ReplyDeleteThere's more about this in today's Science: www.sciencemag.org/cgi/content/abstract/1138595
ReplyDeleteThere's an extra issue with GM mosquitoes, in that one of the main concerns about GM technology is that transgenes will spread to wild populations.
Unlike crop plants, this is exactly what's intended for mozzies, so you'd expect anti-GM types to be even more hostile. But because the anti-GM movement is so much weaker in the developing world, where presumably these would be used, I wouldn't expect this to be such an issue.
Another thing is whether a biotech company would invest in creating an insect that you could release, presumably in small quantities, and then leave to its own devices. Perhaps only someone like the WHO would back a project like that.
And finally, there's the question of whether it would work. If I remember rightly, in the 1970s people tried to control Aedes aegyptii (yellow fever) mosquitoes by developing insects with female-killing, driving sex chromosomes. But the mosquito turned out to have already evolved supressors to this - because these elements are an omnipresent fact of evolutionary life.
This is all discussed in 'Genes in conflict' by Robert Trivers and Austin Burt. But I haven't got it in front of me right now.
Cool. Here is there abstract
ReplyDelete"One proposed strategy for controlling the transmission of insect-borne pathogens utilizes a drive mechanism to ensure the rapid spread of transgenes conferring disease refractoriness throughout wild populations. Here we report the creation of maternal-effect selfish genetic elements in Drosophila that drive population replacement and are resistant to recombination-mediated dissociation of drive and disease refractoriness functions. These selfish elements utilize microRNA-mediated silencing of a maternally-expressed gene essential for embryogenesis, coupled with early zygotic expression of a rescuing transgene."