Aedes aegypti mosquitoes will be released in March and April on an island in Guangdong province in a trial to sterilize mosquitoes that transmit diseases like dengue fever.

When a male mosquito designed to carry the Wolbachia bacteria mates with a female, sterile eggs are produced that do not hatch, according to Xi Zhiyong, director of the Sun Yat-sen University-Michigan State University Joint Center of Vector Control for Tropical Diseases.

Wolbachia can be found in 60 percent of insects, including butterflies, dragonflies and fruit flies, but it has the special effect of sterility on the Aedes aegypti mosquito, previous studies have found.

"By reducing the population of Aedes aegypti mosquitoes, the transmission of dengue fever could be curbed," Xi said.

Dengue fever is spread via bites from female mosquitoes. The males do not bite. The fever has hit Guangdong particularly hard this year, with more than 42,000 cases reported by Nov 2.

The provincial capital of Guangzhou has been hit the hardest, while the disease has been reported in 20 out of 21 prefecture-level cities throughout the province.

According to Xi, the Wolbachia-carrying mosquitoes will be released first on Shazai Island, in the Nansha district of Guangzhou.

The island is relatively unpopulated so is less bothered by mosquitoes and insects from outside, he said. "That helps with evaluating the efficacy of the method."

To achieve the best outcome, "five Wolbachia-carrying male mosquitoes should be released for each common male mosquito on the island," he added.

Although local residents will witness a sharp increase in the mosquito population in March and April, the scheduled release time, they should not be alarmed.

"There is no reason to worry, as they don't bite at all," Xi said, expressing gratitude for the tolerance and support from residents of the island.

"Our mosquitoes do more good rather than harm and the method, compared with chemicals and pesticide, has no impact on the environment," he said. "Pesticides kills pests but at the same time good insects."

Over time, pests can become resistant to the pesticides. In addition to Shazai Island, the mosquitoes will be released in Jiangmen, Guangdong province, and Hainan province, in further trials.

"It's expected that the trials will be expanded to other parts of the country if they have a promising outcome," he said.

Previously, Wolbachia-carrying mosquitoes have been released in countries including Brazil, Australia, Indonesia and Vietnam to reduce the mosquito population and prevent mosquito-borne diseases.

shanjuan@chinadaily.com.cn

(China Daily USA 11/10/2014 page4)