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Zika Virus Outbreak

FDA Says Test of Genetically Modified Mosquitoes Is Safe

Image: Genetically modified Aedes Aegypti mosquito pupae emerge

Genetically modified Aedes aegypti mosquito pupae emerge, engineered by Oxitec. The company says its dud mosquitoes reduced the number of mosquito larvae by 80 percent in one small Brazilian city. Oxitec

It's probably safe to test genetically modified mosquitoes in Key West, the Food and Drug Administration said Friday, but it's asking for public opinion before formally approving such an experiment.

It's likely to get an earful. The American public has strong opinions about genetically modified anything, and a quarter of those asked in a recent poll by the University of Pennsylvania's Annenberg Public Policy Center said they thought genetically engineered mosquitoes had actually spread Zika virus in Brazil.

The World Health Organization, Centers for Disease Control and Prevention and other experts say that's impossible, and say it's the natural Aedes aegypti mosquitoes that are spreading it by biting people.

"By allowing the trial, the FDA will be signaling that science and evidence-based practices should prevail over the hysteria and irrationality long associated with genetically modified organisms," said Dr. Zachary Adelman, Associate Professor, Department of Entomology at Virginia Tech University.

A British-based company called Oxitec is developing the mosquitoes to fight dengue, a painful and potentially deadly virus that circulates in many countries around the world and which is especially bad in Brazil.

The same Aedes aegypti mosquitoes that spread dengue also carry the chikungunya virus, the yellow fever virus and Zika.

Related: Top Doctors Call for Money to Fight Zika

Now that Zika is poised to spread across almost all of Latin America and the Caribbean, causing birth defects and perhaps also paralyzing nerve conditions in adults, the pressure to control mosquitoes is even stronger.

Oxitec genetically alters male Aedes mosquitoes so that any offspring they father don't develop properly. The genetically modified males mate with the females, which lay dud eggs.

"A male OX513A mosquito released by Oxitec is essentially a flying non-chemical 'insecticide' that seeks out and targets Aedes aegypti females and their offspring," said David O'Brochta, an entomologist at the University of Maryland.

"These mosquitoes do not persist in the environment and all mosquitoes with Oxitec's mosquito-killing gene die."

Oxitec has been seeking permission to test their mosquitoes in the Florida Keys, where dengue and other viruses could also take hold in the mosquito populations.

The company says the GM mosquitoes would be safer for the environment and for people than the wide use of insecticides, which can kill bees and other beneficial insects.

The FDA says Oxitec's environmental safety assessment looks good.

"FDA found that the probability that the release of OX513A male mosquitoes would result in toxic or allergenic effects in humans or other animals is negligible based on the sponsor's draft environmental assessment," the agency said in a statement released Friday.

"Almost all of the OX513A mosquitoes released for the investigational field trial will be male, and male mosquitoes do not bite humans or other animals. They are therefore not expected to have any direct impacts on human or animal health," the FDA added.

And it's unlikely any human or animal bitten by a female modified mosquito could somehow be exposed to the altered genes, the FDA said.

Oxitec, which is owned by Maryland-based Intrexon Corporation, tested its mosquitoes in the small Brazilian city of Piracicaba and said the reduced the number of mosquito larvae by 80 percent in one area.

Now they want to test them in Florida. "The proposed investigational field trial would be carried out in Key Haven, Monroe County, Florida under Oxitec's supervision in conjunction with the Florida Keys Mosquito Control District," the FDA said.

The FDA is opening the plan up for 30 days of public comment. There is already local opposition.

The Florida Keys Environmental Coalition wants to try a different approach, using mosquitoes infected with bacteria that limit their ability to transmit viruses.

"Oxitec has exploited the fear surrounding Zika very effectively," Barry Wray, who leads the group, told The Associated Press.

"When you start looking at the quantity of mosquitoes they need to continuously provide, in order to keep problems under control, the numbers are astounding. So is the money required!"

The Annenberg survey showed there's a lot of mistrust and confusion about GM mosquitoes and genetically modified organisms (GMOs) in general. When asked whether scientists have shown that GM mosquitoes caused the Zika virus outbreak, 24 percent said it was true, 24 percent said it false and 44 percent said scientists are not sure.

"Asked if GM mosquitoes could minimize the spread of the Zika virus, 28 percent said that was true, 10 percent said that was false and 55 percent said scientists are not sure," Annenberg said.

After people were told that the GM mosquitoes would produce offspring that die before they mature, 43 percent of those polled said they would favor using the mosquitoes to control Zika and 33 percent said they would oppose it.

Most experts agree that genetically modified mosquitoes alone are not going to destroy mosquito populations. Aedes species of mosquitoes only travel a few hundred feet in their lifetimes and only live a few days. It would require huge numbers of the dud dad mosquitoes to have a large effect.

The WHO advocates using a combination of mosquito control measures, including GM mosquitoes but also those infected with bacteria to make them less likely to carry disease, mosquitoes sterilized by radiation, as well as the use of insecticides, draining water, installing screens and educating the public.

Mosquitoes carry many different viruses. The most common is dengue, which threatens 40 percent of the world's population and which infects close to 400 million people each year. It kills about one in every 2,000 people infected, according to the CDC.

Most experts also agree that wiping out Aedes populations would not have a bad effect on south Florida. The Aedes aegypti species is not native to the Americas and was likely carried in by traders in the 17th century.