A male GMO mosquito passes along a lethal gene that kills his offspring
Field trials in Central and South America show promising results
Anti-GMO reaction in Key West, Florida, stopped a field trial there
Editor’s Note: This is part three in a four-part series about the efforts to stop or slow the spread of Zika virus though the use of modified and engineered mosquitoes. See all four pieces here.
OX513A may soon be a household name in the fight against Zika in Florida.
No, he’s not a new member of the Star Wars cast. OX513A is a male Aedes aegypti mosquito, genetically engineered to pass along a lethal gene to wild females that makes the females’ offspring die. He’s the product of Oxitec, a small biotechnology company launched by Oxford University professors in 2002, now owned by global biotech giant Intrexon.
And depending on the outcome of public comments to the FDA, OX513A could make his first appearance in Florida later this year as part of a trial, testing his ability to fight Zika-carrying mosquitos in Florida.
OX513A is a mutated version of a “sterile” mosquito. Other sterile insects are created by a method called SIT, short for sterile insect technique, where the males are sterilized by gamma rays before being introduced into the wild to interfere with mosquito baby-making.
But not OX513A. This male is created by injecting very small amounts of synthetic DNA into thousands of mosquito eggs until finally one of the eggs accepts the DNA into its genome, creating two genes. One is a lethal gene, synthesized from E. coli and the herpes simplex virus. It’s lethal because it creates a protein called tTAV which interferes with a cell’s activity, killing the infected mosquito before it can reach adulthood.
But wait – if OX513A is infected with a lethal gene, how can he grow up to mate with wild females? Because he’s also fed an antidote, tetracycline, as he’s being raised.
“Every single one of these mosquitoes is going to die as larvae unless you go out of your way to save it,” explained Oxitec CEO Hadyn Parry. “So you use tetracycline in the water to rescue that generation. Then that generation will grow to adults, they’ll lay more eggs, and the larvae would die, except you’ll feed them with some antidote, in which case they live again. So this is a fail-safe system for every generation.”
The second synthetic gene, based on DNA from coral, implants a fluorescent red marker in OX513A so researchers can more easily track him.
“The color marker is absolutely essential,” said Parry. “And that’s because you want to know how many males you need to release in a town. By looking at the red color in the larvae, you can see how you’re doing in controlling the population, which areas need more males, which areas need less males.”
Oxitec has field tested OX513A in the Cayman Islands, Panama and Brazil, and claims a large success rate with each release. For example, in the Cayman Islands in 2010, said Parry, a small release of males created an 80% reduction in the disease-carrying population. Another trial in an urban area of Brazil reduced the Aedes aegypti by 95%. Oxitec recently announced an agreement with Brazilian officials to build a mosquito-breeding factory in Piracicaba, which they say will protect more than 300,000 people.
Newsflash! Mutant mosquitoes threaten the Conch Republic!
But in the United States, OX513A had another hurdle to overcome: public concern about genetically modified creatures. Here’s what happened in Key West, Florida, also known as the Conch Republic.
In 2009 and 2010, local outbreaks of dengue fever (which, like Zika, is spread by the Aedes aegypti) left the Florida Keys Mosquito Control District desperate for new options. Despite an avalanche of effort – from aerial, truck and backpack spraying to the use of mosquito-eating fish – local control efforts to contain the Aedes aegypti with larvicide and pesticide had been largely ineffective. Costly too. Even though Aedes aegypti is only 1% of its mosquito population, Florida Keys Mosquito Control budgets more than $1 million a year, a full tenth of its total funding, to fighting it.
So in 2012, the district reached out to Oxitec for help. But when word spread, public backlash was swift: More than 100,000 people signed a Change.org petition against the proposal; that number has grown to more than 160,000 today. Public relations campaigns reminding Floridians that OX513A doesn’t bite because he’s male and feeds only on nectar didn’t completely solve the problem. Media reports quoted angry residents refusing to be treated as “guinea pigs” for the “superbug” or “Robo-Frankenstein” mosquito.
But Oxitec’s Parry feels that Zika could be a game changer. “The threat of Zika is so great, I think that it will change the paradigm here,” Parry said. “I do think you can always get the people who are against genetic engineering for whatever reason. But I think the big majority of people will want to go ahead.”
A recent national survey by Purdue University proves his point. Researchers found 78% of respondents would support the introduction of genetically modified mosquitoes into the United States to curb the spread of Zika.
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Parry’s belief will soon be put to the test. The FDA has released the results of their environmental assessment of OX513A: there is negligible risk that this GMO mosquito will do anything other than what he was created to do: mate with wild females and pass on his lethal gene. There is a thirty day period for public comment.