Modifying the genes of mosquitoes can transform these pests into a weapon capable of fighting disease. Zika, dengue and chikungunya are all viral diseases spread by the yellow fever mosquito, Aedes aegypti. Because there are no cures for these viruses, health officials are eager to find new methods to slow their spread. Genetically engineered mosquitoes are being studied as a tool for this reason.
Scientists are modifying the genome of A. aegypti mosquitoes by inserting a gene into the insect that prevents its offspring from surviving to adulthood. This gene, tTAV (tetracycline repressible transactivator variant), makes a non-toxic protein that essentially ties up the machinery inside the insect’s cells, so that genes key to survival are not expressed and the insect dies.
The process works by inserting the tTAV gene variant into male mosquitos, which do not bite or transmit disease. In the rearing facilities where these insects are kept, an antidote of tetracycline (an antibiotic) is given to the mosquitoes to turn off the tTAV gene and prevent it from producing the protein responsible for eventually killing the insect. In the presence of tetracycline, the insects survive and reproduce in the rearing facility; however, when the males are released into the wild, their offspring cannot access the antibiotic and they die before becoming adults. The idea is to release large numbers of these male mosquitoes repeatedly over time, so they mate with wild females and reduce the wild population. As populations of these mosquitoes decline, so does the threat of disease.
Oxitec, the biotechnology company responsible for creating these genetically engineered mosquitoes, has received regulatory approvals for open field trials. So far trials have taken place in the Cayman Islands, Panama, Brazil and Malaysia and projects are currently ongoing in Brazil and Grand Cayman. Field releases of the genetically engineered mosquitoes have reduced populations of A. aegypti mosquitoes by up to 90 percent at test sites over a period of six months.
In 2016, a trial was planned for the Florida Keys, but it was delayed several times
and never happened after strong voter opposition. Plans for a future release of
the mosquitoes in the United States are currently awaiting approval from the U.S.
Environmental Protection Agency.
Last Reviewed: April 2018