FDA clears way for gene-altered mosquito

A mosquito genetically modified to produce offspring that can’t reproduce is one step closer to being tested in a field trial in the U.S., as part of efforts to stop the spread of the Zika virus and other mosquito-borne diseases.

The Food & Drug Administration concluded earlier this month that a planned field trial in Key Haven, Fla., of the OX513A Aedes aegypti mosquito developed by England-based biotech company Oxitec “will not result in significant impacts on the environment.”

Oxitec is working with the Florida Keys Mosquito Control District to conduct the experiment. The company cannot legally release its genetically modified mosquitoes, however, until FDA gives a final goahead. First, though, FDA will review public comments on the company’s environmental assessment, which was released with the agency’s finding of no significant impact. It could be several months before FDA makes a final determination.

“The A. aegypti mosquito represents a significant threat to human health and in many countries has been spreading Zika, dengue, and chikungunya viruses,” says Oxitec CEO Hadyn Parry. “This mosquito is nonnative to the U.S. and difficult to control, with the best available methods only able to reduce the population by up to 50%,” he notes.

Offspring from Oxitec’s OX513A mosquitoes die before reaching adulthood, thus reducing the population of this species. The company intends to release only male Oxitec mosquitoes, which do not bite, to mate with wild A. aegypti females.

The OX513A mosquitoes have been tested in trials in Brazil, Panama, and the Cayman Islands, with promising results. In each case, the A. aegypti population was reduced by more than 90%, Oxitec claims. This, it says, is “an exceptional level of control compared to conventional methods, such as insecticides.”

But some critics argue that FDA is not the appropriate federal agency to assess environmental effects. It is doing so because, in the U.S., genetically modified animals are regulated by FDA as new animal drugs. Deliberately altering the traits of a mosquito to suppress its population is “not something we should do lightly,” says Kevin Esvelt, a biochemist and leader of the Sculpting Evolution Group at Massachusetts Institute of Technology. “There might be unexpected ecological side effects,” he warns.

Esvelt has expertise in developing technologies such as RNA-guided CRISPR gene drive, which can be used to alter the traits of wild populations. “At this stage we know so little about Zika that I am uncomfortable talking about the potential to use gene drive against these mosquitoes because of Zika. We just don’t know enough.” —BRITT ERICKSON

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