Gazette: Genetically-engineered mosquitoes | The Body of Evidence

Gazette: Genetically-engineered mosquitoes

With Chris on a much deserved vacation (during which he is not at all reading echocardiograms over a slow Internet connection), I thought I would share with you his latest opinion piece published in the Montreal Gazette. As always, I would invite you to read the comments at the end of the article to familiarize yourself with the types of arguments made by people who oppose genetic modifications (but who seem perfectly fine with genetically-engineered bacteria producing insulin). Click on the link below to access the Gazette website, or read the article below. -- Jonathan

Mosquitoes are the most lethal creatures on the planet. They kill millions of people every year by spreading diseases like dengue, yellow fever and malaria. Now mosquitoes (specifically the Aedes aegyptii mosquito) are spreading the Zika virus, which the World Health Organization says will infect three million to four million people by the end of this year. Mosquitoes are not a summertime annoyance; they are a major public health problem. Kill mosquitoes, and you save lives.

You can use larvicides to kill them before they grow up into blood-sucking adults, but the mosquitoes develop resistance after a while. You can use the mosquitofish, Gambusia afiniis, which will happily devour any mosquito larvae it finds. Problem is they will devour everything else, too, and can become invasive pests wherever they are introduced. Or you can fight fire with fire and get mosquitoes to kill mosquitoes.

Oxitech, a British biotech company, has developed a genetically modified mosquito; the second genetically modified animal to come into being (the first being the genetically modified salmon last year). The United States Food and Drug Administration has approved the genetically modified Aedes aegypti for a field test in the Florida Keys, where the Zika virus has spread into the U.S.

The mosquito works like this. Researchers inserted a gene into the mosquito's DNA that produces a protein called tetracycline transcriptional activator variant (tTAV). The tTAV blocks DNA transcription so that cells can't function properly. The mosquito dies because of a fatal flaw in its DNA.

When these mosquitoes are released into the wild, they breed with native mosquitoes and produce genetically flawed offspring that don't survive to maturity. Therefore, no new generation and no new mosquitoes. No mosquitoes means no spread of Zika.

There is concern that these genetically modified mosquitoes will bite humans and transfer dangerous genes to people. This would make a great movie plot, but it can't happen in real life.

When mosquitoes bite you, they can transfer bacteria or viruses into your blood stream. That's how you get diseases like malaria, dengue or chikungunya. But mosquitoes don't transfer DNA. The issue has been studied in both humans and animals, and mosquito bites are not a vector for DNA transfer.

Think about it: You've been bitten hundreds if not thousands of times by mosquitoes, and yet you have no mosquito DNA in you. Nor do mosquitoes have any human DNA. If DNA were transferrable via mosquito bites, you would think some would have made its way into our genome over the millennia mosquitoes have been feasting on our blood.

However, the point is moot because the mosquitoes modified by Oxitech don't bite humans. Only female mosquitoes bite humans, and these genetically modified mosquitoes are all males. Problem solved.

There is always the concern that these genetically modified mosquitoes will have some unforeseen effects on the environment. But they have been studied and compared to the unmodified mosquito and found be identical in terms of number of eggs laid, the egg-hatching rate, larval survivorship and many other parameters. They won't spread across the planet (the mosquito does poorly in temperatures under 15°C, which is why Zika likely won't affect Canadians unless they travel to warmer climates).

Also, these mosquitoes are not some new invention. They were developed in 2002 to fight dengue fever, but have now been repurposed because of the Zika outbreak. They have been subject to field trials in Brazil, the Cayman Islands and Panama and studied for more than a decade.

But most importantly, these are not super mosquitoes. They are regular mosquitoes with a programmed genetic defect. Their only goal is to mate with the native female mosquitoes to produce genetically flawed offspring that won't survive long enough spread Zika to pregnant women.

To date, Zika has caused more than 1,800 confirmed birth defects (with another 3,000 suspected). That number - not genetically modified mosquitoes - should make us scared.