Mosquitoes are one of the deadliest animals in the world, but it’s only the females that pose a threat to people. While female mosquitoes feed on blood to support reproduction, male mosquitoes don’t bite, and thus don’t spread deadly diseases such as malaria and dengue fever.
One way researchers hope to reduce the spread of mosquito-borne diseases is by reducing the number of female mosquitoes. Researchers at Virginia Tech have identified the gene responsible for determining sex in Aedes aegypti, the species of mosquito that spreads the viruses causing dengue, yellow fever, and chikungunya. They injected this genetic switch, called Nix, into mosquito embryos, causing two-thirds of the female mosquitoes to develop male genitalia. When they removed Nix, the male mosquitoes developed female genitals.
“We’re not there yet, but the ultimate goal is to be able to establish transgenic lines that express Nix in genetic females to convert them to harmless males,” Virginia Tech entomologist Zach Adelman said in a press statement.
However, this wouldn’t mean the end of every female mosquito on Earth. Only select mosquito species are vectors for disease; most are harmless. For instance, in Thailand, out of 450 identified mosquito species, only 10 carry the viruses that spread diseases among humans. Geneticists can test to see if specific mosquitoes are infected, and could target only those for the sex-change treatment.