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If Genetically Modified Mosquitoes Freaked You Out, You Won't Like What's Coming

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Over the past few years, as people have been freaking out about a plan to release genetically modified mosquitoes in the Florida Keys, the company behind those mosquitoes has been quietly toiling away on another project. This week, British biotech company Oxitec announced plans for field trials of a genetically modified Mediterranean fruit fly in Western Australia. The so-called Medfly is a devastating agricultural pest, and by engineering it to produce offspring that cannot survive, Oxitec hopes to cull its numbers.

Oxitec’s mutant mosquitoes, intended to help stop the spread of Zika virus and other mosquito-borne illnesses, were just the beginning. The company envisions a world where all of the threats that insects pose are mitigated by simply engineering a species to better regulate itself.


The Medfly, a parasite of over 250 crops, is considered one of the most menacing agricultural pests in the world. It lays its eggs under the skin of fruits and vegetables, and after its offspring hatch they develop into larvae that feed on the pulp. In the 1980s, a severe Medfly infestation swept through California, devastating agricultural production and also residents, who were alarmed by the intense aerial pesticide spraying that ensued. Today, Medfly still threatens crops through throughout North America and Australia.

“Medfly is a bad pest wherever it occurs,” said David Windsor, the horticulture director of Western Australia’s Department of Agriculture and Food. “It is voracious.”


Biological methods of control have long been considered the best way to fight the Medfly. Typically, billions of male flies are radioactively sterilized in the lab and then released to mate with wild females, in order to reduce the wild population over time. Oxitec’s method is a riff on this “sterile insect technique,” using genetic engineering to sterilize male flies more precisely. While radiation spurs random mutations that—with luck—render male mosquitoes sterile, Oxitec’s Medfly is augmented with two new genes. One of those genes glows under the microscope to allow the flies to be tracked. The other, a “self-limiting” gene, causes offsprings’ developmental cycles to go haywire, ensuring they never make it to an age where they might mate.

Oxitec has already had a string of successful in-lab trials with its genetically-modified Medfly. And last week, the Western Australian government released the results of a greenhouse trial it conducted testing whether Oxitec’s engineered mosquitoes mate as well as traditional, radiation-sterilized bugs. They do. The government said it now plans to go ahead with a trial to see how Oxitec’s mutant fruit flies fare in the wild.

Environmentalists have long supported traditional sterilization as a pest-control tactic—no scary chemicals necessary. But reception to Oxitec’s adaptation of this technique has been mixed. Oxitec has worked with the USDA on field trials of a genetically-altered pink bollworm since 2006 and received little blowback. In Australia, local press heralds Oxitec’s Medflies as the potential future of agricultural pest control. In Florida, meanwhile, Oxitec’s mosquito-release plan was so controversial that it was put to a local vote. The company has been forced to find a new trial location after voters in the neighborhood slated for the trial rejected it.


In the eyes of some individuals, the mosquito project is an expression of horrifying corporate greed that treats the public as lab rats. In the agriculture sphere, where new solutions for pests are desperately needed as pesticides become ineffective or illegal, Oxitec’s technology is greeted with enthusiasm.

In Western Australia, Oxitec’s new method could be advantageous because pesticides are often ineffective (not to mention dangerous), and because in theory far fewer insects are needed to achieve the same effect as radiation sterilization. The high levels of radiation required to guarantee sterility can turn male insects into sad, unattractive mates for wild females—and if they don’t mate, the technique does little to cull their numbers. Genetic engineering may be more effective, since it doesn’t leave male mates quite so bedraggled. In the latest trial, the mating performance of Oxitec males was comparable to sterile males irradiated at low levels, and it exceeded sterile males treated with a higher dose.


It’s important to note that while the promises of GMOs are great, they do not always deliver. Recently, an extensive examination by The New York Times found that genetically-modified crops in the United States and Canada had not actually boosted crop yields or led to an overall reduction in pesticide use. It’s possible that something in the altered genetic code of male flies might act as a turnoff for female flies, reducing the effectiveness of the program, or that the new technology won’t wind up being more cost-effective in the end. In Malaysia, where Oxitec conducted trials of its mosquitoes, the country decided to not go ahead with the project after trials, citing cost.

“At the end of the day it will all be about economics: which does the job better and cheaper,” said Philip Stansly, an entomologist who studies agricultural pests at the University of Florida.


Public acceptance, he said, will also be an important factor.

“Unfortunately,” he said, “that has also been an impediment although this technology should be safer than insecticides.”


But to Oxitec at least, the future for genetic engineering seems bright. Dr. Neil Morrison, the lead on Oxitec’s Medfly project, said that the company plans to test its Medfly in other countries beyond Australia. Oxitech is also working on genetically engineering several other agricultural pests, including the Diamondback moth, Drosophila suzukii, and the Olive fly.

And earlier this year, Oxitec CEO Haydn Parry told me that the company eventually hopes to court individual consumers, too.


“I can send you eggs and you can protect your own biosphere,” Parry said.

Parry imagines selling genetically-modified insects at the garden store—perhaps I’d pick up some Oxitec mosquitoes instead of a Citronella candle to protect my garden party guests from nasty bites, or some engineered Medflies to prevent pests on my backyard vegetable garden.


Windsor said that there are still many questions to answer before Oxitec’s Medflies might be considered for commercial approval in Australia. Even before the field trial proceeds, it must first gain the approval of Australia’s Office of the Gene Technology Regulator, which could take up to a year.


“We’re interested in this technology because it offers the theoretical advantage that the male flies are fitter, meaning it will be cheaper and more efficient,” Windsor told me. “Our first question was whether these two fly populations are compatible. Our results suggest that’s the case.”

Perhaps more interesting than early results is where those results might lead.