China fights dengue fever by releasing sterile mosquitoes

In a new approach to fighting dengue fever, the southern Chinese metropolis of Guangzhou has released sterile mosquitoes as part of its defense strategy. Guangzhou, located in a subtropical region, experiences long periods of hot and humid weather, creating an ideal environment for dengue transmission. In the city, autumn began on November 18 this year, ending a long summer that lasted 240 days.

From April to November every year, millions of “modified” mosquitoes are released into Xiashi Village to combat the serious infectious disease. They are male Aedes albopictus mosquitoes infected with the Wolbachia bacteria, which makes them sterile.

Traditional disinfection methods target adult mosquitoes, larvae and pupae, but mosquito eggs can remain dormant in breeding sites for long periods, making them difficult to eliminate, explained Qian Wei, a researcher on the Chinese team that first adopted the use of this technique.

Male Aedes albopictus mosquitoes, infected with Wolbachia and sterilized by Qian’s team, are mass-produced and screened at a factory in Guangzhou. Once released, they mate with wild female mosquitoes – resulting in eggs that do not incubate. Because male mosquitoes don’t bite or suck blood, they can be released for a long period, reducing the Aedes albopictus population and preventing the spread of dengue fever, Qian said.

Xiashi Village was the inaugural test site for this biological control method. Zhu Jieyong, director of the village committee, said the village’s proximity to hills and rivers creates favorable conditions for mosquito breeding, which has resulted in dozens of dengue cases annually in the past. In 2018, the village invited Qian’s team to conduct a test.

“We release mosquitoes once or twice a week in the village, approximately one million males at a time,” Qian recalled. They primarily used drones to release mosquitoes and deployed mosquito traps in an effort to better understand population structure and monitor their density.

The team also monitored neighboring villages as control areas to compare and analyze the effects of releasing sterile mosquitoes. Continuous monitoring and data analysis have shown a significant decrease in Aedes albopictus mosquitoes – with control rates reaching 98%.

According to Zhu, since these tests began, the village has not needed to hire professionals to spray pesticides, thus providing a safer, healthier and more environmentally friendly living space for local residents. During the last seven years, not a single dengue case has been reported in the village.