Turns Out Fighting Mosquitoes With Mosquitoes Actually Works

In the Brazilian city of Indaiatuba, an effort is underway to eliminate these pests before they have a chance to spread illness. The weapon: more Aedes aegypti mosquitoes—but ones genetically engineered to kill their own kind. Made by British biotechnology firm Oxitec, the mosquitoes seem to be working. The modified mosquitoes carry a synthetic self-limiting gene that prevents female offspring from surviving. This is important, because only the females bite and transmit disease. In a new study, scientists at the company showed that their engineered insects were able to slash the local population of Aedes aegypti by up to 96 percent over 11 months in the neighborhoods where they were released. “This is an area with high levels of Aedes aegypti, and they periodically have outbreaks of dengue,” says Nathan Rose, head of malaria programs at Oxitec. In fact, this summer the Brazilian Ministry of Health reported that dengue fever was continuing to spread in all five regions of the country. Between January 1 and May 31, Brazil had more than 1.1 million cases—an increase of 198 percent compared to the same period in 2021. In those five months, the disease, which causes high fever, rash, and muscle and joint pain, killed 504 people. For the study, which was conducted in 2018 and 2019, the company chose four densely populated neighborhoods with high levels of Aedes aegypti. In two, scientists released a “dose” of 100 male mosquitoes per resident per week. In the others, they cranked that up to 500.

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