Brazil has opened its first-ever, large-scale genetically modified mosquito farm in an effort to reduce the incidence of dengue fever.

The mosquitoes are a genetically modified (GM) version of the Aedes aegypti, the species responsible for transmitting the dengue virus to humans. The farm was inaugurated early last week and is expected to produce millions of GM insects each month.

Scientists at the British-based Oxitec developed a method of shortening the lifespan of the mosquitoes and reducing mosquito populations by, essentially, sterilizing them. The mosquitoes are engineered to need the antibiotic tetracycline to develop beyond adolescence. Male mosquitoes in the laboratory are given the antibiotic to reach adulthood and then released into the wild to breed with wild females. The larvae, unable to access tetracycline, die before they are fully-grown. After a few days, both the offspring and the released males are dead.

Small-scale trials of the method have shown some success in the Grand Cayman Islands, Brazil and Malaysia. After the introduction of the GM mosquitoes into the environment, A. aegypti populations were reduced to between 75 to 90 percent, compared to similar areas where the mosquitoes were not released.

Scientists are calling it a victory in the fight against dengue.

"From a scientific point of view and an environmental sustainability point of view, we think we have a really good solution to the problem," said CEO of Oxitec, Hadyn Parry.

It is easy to see why researchers are excited about the results. Dengue fever is a public health nightmare. The mosquitoes that transmit the virus feed during the day, making it difficult to kill them effectively with insecticide and the use of bed nets ineffective. The insects also lay their eggs in clean, still water, often in urban areas. There is no effective vaccine or cure, only limited treatment options, and it is widespread – affecting between 50 and 100 million people each year worldwide.

The primary method of managing dengue has been through mosquito control. The use of GM mosquitoes could help eliminate the A. aegypti at a lower cost than current methods and without using as many chemicals, effectively saving endemic countries billions of dollars each year.

Oxitec estimates that apart from the cost of startup ­­– production facilities, equipment and training – its method would cost less than $10 per person per year, making it more feasible for poorer countries to fight rising rates of dengue.  

"This is not a rich man's tool; there's no point in protecting a rich man's mansion," Parry said. "You want to protect a community so it's got to be cheap."

But not everyone is thrilled about the idea.

A mothers group out of Key West, a proposed location for the release of the GM mosquitoes, has come out vehemently opposed to it. 

“If something goes wrong the consequences could be catastrophic, not only for humans but also the whole ecosystem, said Mila de Mier, a Key West resident told the Guardian. “I don’t want my family being used as laboratory rats for this.”

De Mier started a petition on the social movement website in opposition to Oxitec that has now collected roughly 100,000 signatures.

The primary concern, de Mier said, was the uncertainty and lack of scientific data regarding potential the GM mosquitoes will pose long-term harm to Key West’s ecosystem and its inhabitants.

She and others who oppose the research also point out the potential risk of females being released along with the males, the possibility that the gene will mutate, and any unforeseen potential negative effects it might have on the area’s insects and wildlife.

Researchers, however, dismiss these concerns.

"We are not putting an advantage into these mosquitoes; we are putting in a disadvantage, sterility, which is the biggest disadvantage you can have," Parry said. "You are not spreading your gene down generations because each one is sterile – it dies out. They do not out cross and mate with other species. So you are not spreading your gene laterally or downward."

Additionally, the mosquitoes have been bred in the laboratory for roughly a decade with “no signs of mutations or changes in performance,” according to the Florida Keys Mosquito Control District.

Researchers also point out that there is already an effort to eliminate A. aegypti by spraying insecticide and that the U.S. Department of Agriculture has found Oxitec’s method to be “environmentally preferable” to currently available alternatives because of the lower impact it has on the environment.

The A. aegypti are considered invasive in Key West, originating in Africa – thus the name aegypti – and thought to have been brought over on slave ships. They have only been in the area for a period of about 200 years and are not a true part of the native ecosystem.

De Mier and her cohort in Key West aren’t the only skeptics. Earlier this year, Germany’s Max Planck Institute for Evolutionary Biology looked at information from Oxitec’s trials in Malaysia and Grand Cayman, and accused the company of having a lack of transparency. Its findings suggest "deficits in the scientific quality of regulatory documents and a general absence of accurate experimental descriptions available before releases start."

For now, the city of Key West has decided to delay any release of the Oxitec mosquitoes until more information is available regarding their potential impact on the local environment.

If Oxitec’s method does prove successful in Brazil, it’s possible that the technology could be used to combat other similar zoonotic diseases. The company said that has already tested the method with malaria-carrying Anopheles mosquitoes. But in order to do that, the research needs to gain more support and a return on investment.

"We could have outdoor trials in five years' time," Parry said. "We have transformed it, modified it. It can be done – it's only a question of time and money. Our plan is to prove it works in dengue and then people will be willing to invest the money for the next stages."


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