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Crushing Zika via genetically modified mosquitoes

Annetta Miller, special to

With the Olympic games under way in Zika-ravaged Brazil and the United States' first locally transmitted Zika cases now confirmed, a biotechnology company is looking to take a bite out of the Zika crisis — by deploying armies of genetically modified mosquitoes.

Oxitec, the British subsidiary of Germantown, Maryland-based Intrexon, received a green light from the Food and Drug Administration on Friday to release the GMO mosquitoes as part of an investigational field trial in Key Haven in the Florida Keys. Residents of Key Haven will vote on the trial in a nonbinding referendum scheduled for November, with final approval to reside with the Florida Keys Mosquito Control Board.

"It couldn't have come at a better time," Oxitec CEO Hadyn Parry told reporters Friday.

While the company is glad it got the regulatory green light, Florida locals are concerned there may be risks to the human population.

Friday's FDA ruling, known as a Final Finding of No Significant Impact and Final Environmental Assessment (FONSI), deemed that any toxic or allergenic effects in humans caused by the GMO mosquitoes would likely be negligible.

The Aedes aegypti mosquito, the species that transmits the Dengue virus, Chikungunya fever and Zika
William Volcov | Brazil Photo Press | LatinContent | Getty Images

The first U.S. cases of the virus attributed to local transmission were reported last week in a neighborhood in Miami. Zika has been linked to microcephaly and other birth defects, as well as the neurological disorder Guillain-Barré syndrome.

Oxitec's genetically modified mosquitoes are members of the Aedes aegypti species, which causes the Zika virus and several other infectious diseases, including dengue fever, yellow fever and chikungunya.

Since male mosquitoes do not bite, Oxitec's mosquito brigade will not be capable of spreading disease. When they mate with wild female Aedes aegypti, their offspring do not live long enough to reproduce.

Parry said the GMO mosquitoes have been deployed successfully in the Cayman Islands, Brazil and Panama, where they have reduced the population of Aedes aegypti mosquitoes by 90 percent over a period of six months.

In addition to having a self-limiting gene, the Oxitec mosquitoes carry a colored marker invisible to the naked eye. When viewed under a fluorescent light, the markers allow Oxitec to distinguish their own GMO mosquitoes from Aedes aegypti in the wild.

"We'll be focusing on operational capability, closely monitoring, counting, releasing and tracing the mosquitoes and providing quality control not only in the Zika-infected areas but in surrounding areas," he said.

If approved at the local level, the so-called "friendly" mosquitoes could be airborne by December, according to Parry.

Unintended consequences

Intrexon CEO Randal J. Kirk said Oxitec's new U.S. venture will represent a "major advance" in eradicating Zika. "It's the only proven safe, effective, environmentally sound product that can significantly achieve the reduction of the Aedes aegypti mosquito that the world so desperately needs," he said.

Not everyone greeted the prospect with such enthusiasm, however. "I am very disappointed in the FDA's decision," said Mila de Mier, a mother of three who lives near Key Haven and owns a realty company in the area. Earlier this year, de Mier launched an online petition opposing the Key Haven trial that garnered 160,000 signatures.

De Mier said she fears there could be unknown or unintended risks from genetically engineered insects and says local residents oppose Oxitec's venture. "It's very clear that the people here do not want this trial," she said. We are the subjects of a clinical trial, and we have never been asked for or given our consent. It's being forced down our throats."

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Entomologists who study genetic modification in insects say humans have little to fear from Oxitec's GMO mosquitoes, however. "I don't know anybody in the field of vector control who doesn't believe they are completely safe," said Dr. Grayson C. Brown, a mosquito expert and the director of the Public Health Entomology Laboratory at the University of Kentucky, which is not connected with the Oxitec venture.

Brown said one frequently voiced concern is that a human bitten by one of the GMO mosquitoes could be harmed by an altered gene from the insect. However, such an outcome is biologically implausible, he said. "There are millions of genes in every mosquito, and billions of humans are bitten by mosquitoes every year. There has never been an example of a mosquito gene by itself directly harming a human. After testing these mosquitoes for 14 years, no negative effects on humans or the environment has been detected."

Eradication of the Aedes aegypti mosquito in the wild would likely not harm other living things, because no other species depend solely on it for food, Brown said. Moreover, the use of genetically engineered mosquitoes has proved more ecologically friendly than pesticides, which can harm bees and other insects.

A Miami-Dade County mosquito-control inspector sprays pesticide to kill mosquitoes as the county fights to control the Zika virus outbreak in Miami on August 2, 2016.
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A larger difficulty could lie in the price tag. While Oxitec officials maintain that the cost of the technology compares favorably to the cost of pesticides, they do not publicly provide a cost breakdown. Those familiar with the technology estimate it would cost around 10 cents per mosquito to implement. Depending on the Aedes aegypti population in the area, millions of mosquitoes might have to be released to achieve proper control. That could amount to an increase of threefold to tenfold in a mosquito-control budget, says Brown. A less expensive method of Aedes aegypti control — using mosquito larvae — is in the works.

When Intrexon bought Oxitec in September 2015, Zika had not yet become a household name. The British company had been working instead on developing its genetically modified Aedes aegypti mosquito for dengue fever and other mosquito-borne diseases.

Intrexon's timing was by all accounts serendipitous. But Kirk is careful not to appear gleeful. "I cannot look at something that's causing this level of human suffering as a positive development," he said. "And it's not like we needed additional incentive to reduce the Aedes aegypti population."

In part because of the public concerns about GMOs, Oxitec's U.S. venture has taken flight slowly. FDA approval for the investigational trial took five years, even though the company had already conducted successful trials of its technology overseas.

Earlier this year, Parry spoke before the U.S. Congress about the company's Zika-fighting technology. In light of the worsening Zika crisis worldwide, he urged that an emergency approval process be instituted to speed up the government review. No such action was instituted.

But Parry continues to warn that Zika won't be the last public health crisis initiated by the Aedes aegypti. "Over the past decade, we have completely failed to control this mosquito, and it's brought dengue, it's brought chikungunya and now Zika. Today "[the Zika virus] is what's on everybody's mind. But there will be others. "

— By Annetta Miller, special to