Genetically Modified Pests: The Controversial Release of Suicide Mosquitoes

By Rafaela von Bredow

Part 2: Exploring the Potential Dangers

Photo Gallery: Self-Destructive Mosquitoes Photos
AP

The findings of a study published in the renowned scientific journal PLoS Neglected Tropical Diseases on Tuesday could well make life even more difficult for Oxitec. The paper was written by Guy Reeves and his colleagues. The 39-year-old Briton with curly blond locks is a researcher at the Max Planck Institute for Evolutionary Biology in Plön, northern Germany.

The geneticist has searched through scientific journals, permit applications and regulations. His findings, reviewed and approved by his peers, primarily reveal one thing: The Grand Cayman experiment wasn't an exception; a mere oversight by muddle-headed scientists that somehow forgot to inform the local population adequately on their way from the lab to the field.

"Whatever happened in the Caymans is quite likely to be used as a model for releases in your community, wherever you live in the world," Reeves suggests.

Through the Back Door

In other words, the approach used in the Caymans was well thought out, as if a small group of ambitious biotech managers were trying to introduce a completely new technology through the back door. There are a number of factors that helped them in their endeavor:

  • The novelty of the technology, which makes it harder for regulatory authorities to assess the risks associated with the field trials;
  • The desperation of countries with a high prevalence of dengue, whose willingness to take risks is therefore all the greater;
  • The fact that there are no drugs or approved vaccines yet, and conventional methods for combating mosquitoes -- for instance insecticides -- are insufficient in tackling the problem. Every new weapon is therefore welcome;
  • Good contacts to decision-makers at US approval bodies, whose assessments of risk are valued by experts in other countries.

And it is quite possible that Luke Alphey's lab-tweaked creatures will indeed prove to be a blessing for humanity, especially in countries plagued by dengue. The way these creatures precipitate their own demise is extremely ingenious.

Ever since the 1950s, male pests have typically been sterilized by exposing them to radioactivity, and then released to mate with females in the wild. Today a similar effect is created by inserting malevolent genes. Alphey has given his yellow-fever mosquitoes genetic material that the males pass onto their offspring when they mate with wild females. This genetic material could be called a "suicide gene" because the protein it produces poisons the larvae. As a result, the hosts gradually wipe themselves out.

According to Oxitec, this suicide system works not only in the lab, but also in the field, as the trials on Grand Cayman proved. Eighty mating waves with the lab-manipulated males over a period of 11 weeks allegedly reduced the local mosquito population by 80 percent.

Unknown Consequences

And the potential risks? These are only now coming to light in full, partly thanks to the efforts of Guy Reeves.

The problem is that genetically-modified female mosquitoes can still bite humans. This means the protein which kills their own larvae might be injected into humans when the mosquitoes suck their prey's blood, with unknown consequences for the human organism.

However Luke Alphey has a plausible-sounding set of arguments to allay such fears. "We only release males," he says. What's more, he claims the protein isn't produced in the salivary glands, so it isn't in the female mosquito's saliva in the first place. Being bitten by Oxitec's mosquitoes is therefore allegedly just like being bitten by "normal mosquitoes."

It does indeed seem unlikely that the lab animals could cause damage. Nonetheless Alphey admits his technique isn't perfect yet, and GM females may therefore also be released accidentally. And we have to take him at his word that the larva-killing protein definitely can't be injected into the human blood stream. Unfortunately, like so much else, he can offer not peer-reviewed scientific proof.

Alphey says Oxitec spoke to people on Grand Cayman, and that the locals didn't express concern about being bitten by GM mosquitoes. He claims the islanders hadn't even asked him about it. "It's not really for us to tell them what their concerns should be," he says.

Fundamental Questions

It is precisely this attitude -- this lack of openness -- that isn't exactly making Oxitec many friends. Guy Reeves says: "One has to answer these fundamental questions that most people will have before releasing the animals."

The geneticist doesn't think Oxitec's techniques are "particularly risky" either. He simply wants more transparency. "Companies shouldn't keep scientifically important facts secret where human health and environmental safety are concerned," he says.

Reeves himself is working on even riskier techniques, ones that could permanently change the genetic makeup of entire insect populations. That's why he so vehemently opposes Oxitec's rash field trials: He believes they could trigger a public backlash against this relatively promising new approach, thereby halting research into genetic modification of pests before it really gets off the ground.

He's not alone in his concerns. "If the end result is that this technology isn't accepted, then I've spent the last 20 years conducting research for nothing," says Ernst Wimmer, a developmental biologist at Germany's Göttingen University and one of the pioneers in this field. Nevertheless he says he understands Oxitec's secrecy: "We know about the opponents to genetic engineering, who have destroyed entire experimental crops after they were announced. That, of course, doesn't help us make progress either."

Translated from the German by Jan Liebelt

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