The mosquito species Aedes aegypti transmits viral diseases, including Zika, dengue, chikungunya, West Nile, and yellow fever, between human hosts. For most of these viral diseases, there are no vaccines and no effective medicines. So until recently, public-health officials have had to use old, low-tech approaches to controlling the mosquito vector and reducing the incidence of infections: pesticide sprays, public education about exposure (DEET, mosquito nets, and clothing that covers as much skin as possible), and control of breeding areas (water in flower pots, tires, drains, etc.).
Oxitec, a British subsidiary of the American company Intrexon, has created a new way to control Aedes aegypti. Male mosquitoes are bred in the laboratory with a specific genetic mutation that, in the absence of a certain chemical, causes their offspring to die before reaching maturity. Male mosquitoes do not bite, so their release presents no health risk, and, because their progeny die, the genetically engineered mosquitoes do not persist in the environment. Releasing the males over a period of several months causes a marked reduction in the mosquito population.
In field tests conducted in Brazil, the Cayman Islands, Malaysia, and Panama, Oxitec has shown that the release of these genetically engineered male mosquitoes has consistently reduced wild populations by more than 80 percent, and the most recent field trials show greater than 90 percent reduction. In 2014, on the basis of these field trials, Brazil’s regulatory authority approved the commercial release of these mosquitoes. Brazil approved Oxitec’s approach because the traditional approaches to mosquito control were failing to protect the country’s inhabitants from A. aegypti–borne viral diseases. The apparent association of Zika-virus infection with microcephaly in babies born to infected mothers has only added to the urgency.