Sunday, October 30, 2011

Successful Application of Sterile Insect Technique to Aedes Aegypti Mosquitoes, But Concerns Raised Over Public Reception

Today, the New York Times reported on the publication of a paper in the journal Nature Biotechnology that reports success in the release of large numbers of effectively sterile, male mosquitoes in the Cayman Islands to control the population of the Aedes Aegypti mosquito. Using genetic modification to make the male mosquitoes and any subsequent offspring dependent on doses of tetracycline, researchers working for the company Oxitec hoped that their modified crop would compete with natural males and give rise to a generation of new mosquitoes that would die before birth. Since female mosquitoes only mate once, this technique has to potential to seriously curtail mosquito population and, by association, the risk of spreading diseases such as dengue that use these mosquitoes as vectors.
The same technique has already been used successfully in multiple cases to limit or even eradicate entire insect populations, such as the screw-fly in most of North America. Those cases relied instead on ionizing radiation to sterilize males and/or female flies with the rest of the protocol unchanged. Unfortunately, such techniques can't be applied here since irradiated flies maintain their ability to compete with natural males, something not seen in Aedes aegypti mosquitoes. Indeed, researchers were pleased to attain a 50% competition rate in the studies conducted so far, with the release of enough males to approximate 16 % of the total population having the lethal gene resulting in 10% of larva dying in one example.
Unfortunately, numbers like this form one point of possible controversy. Like with the screw-fly program, an eventual program to eradicate or seriously control the mosquito will have to rely on 'over-kill', with tremendous amounts of modified mosquitoes being released. Given a 3.5% rate of offspring mutating to survive the presence of the gene and a 0.5% rate of females accidentally released alongside the males, programs such as this carry the risk of unintentionally making the situation worse if major errors occur. What may influence public perception the most is that this program involves “genetic modification” and the introduction of vast numbers of modified organisms into the environment. Even if similar programs have been performed with incredible success for decades, these projects needs to be handled with care, lest a public backlash prevent the control of such a deadly pest.

New York Times Article:
Concerns Are Raised About Genetically Modified Mosquitoes
Sterile Insect Technique:
Screwworm Eradication in North and Central America(1987)

-Zachary Herrera

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