Chinese scientists have successfully reduced mosquito numbers in tropical islands near Guangzhou City in southern China with the use of low-level radiation and bacteria.
A series of experiments using the radiation-based sterile insect technique or SIT was able to almost eliminate the field population of invasive mosquitoes Aedes albopictus or Asian tiger mosquitoes in Shazai and Dadaosha islands.
SIT is a form of insect birth control that uses radiation to sterilize male insects, which are later released to mate with wild females. These insects do not produce any offspring, resulting in the decline of insect population over time.
This technique has been used for over 60 years to suppress agricultural pests such as the Mediterranean fruit fly. It was only recently that it has been adopted for use to control the breeding of mosquitoes.
Sterile And Infertile Mosquitoes
The objective of the field trial is to suppress insects that spread Zika, dengue, West Nile virus, Chikungunya, and other diseases. The female mosquitoes were sterilized with low-level radiation while the specially bred adult male mosquitoes received infections from three different species of Wolbachia, a parasitic microorganism, to make them infertile.
Both male and female mosquitoes were released during the peek mating season of 2016 and 2017. Over 200 million mass-reared adult mosquitoes were released, and the end result nearly eliminated the entire female mosquito population on the two islands.
"Here we show that combining incompatible and sterile insect techniques enables near elimination of field populations of the world’s most invasive mosquito species, Aedes albopictus," the authors said in their abstract of the study published in the Nature International Journal Of Science.
China's Mosquito Factory
Xi Zhiyong, one of the researchers and a professor at the Sun Yat-sen University-Michigan State University Joint Centre of Vector Control for Tropical Diseases ran a mosquito factory in southern China where he previously attempted to use sterilized male mosquitoes to mate with unaltered females. The government-supported mosquito-breeding facility can produce 10 million bred males per week.
“Our study predicts that the overall future costs of a fully operational intervention using this environmentally friendly approach will be around $108 annually,” said Xi.
He added that the technique is cost-effective as compared with other mosquito control strategies.
The positive results of the field trial in Guangzhou developed into a broad international collaboration with disease-endemic countries including Singapore and Mexico. China plans to test the technique in larger urban areas using sterile male mosquitoes.
Asian tiger mosquitoes are daytime-biting mosquitoes that can be distinguished through their prominent single white stripe on the center of their head and back.
