Chinese Scientists Develop Biological Weapons Against Disease-Ridden Mosquitoes

Chinese scientists deployed more than 200 million genetically modified (GM) sterile male mosquitoes to wipe-out the entire population of dengue fever-carrying mosquitoes on two islands in southern China in a stunning success for genetic modification first talked about in the West in the 1940s.

Today, GM mosquitoes developed over decades of research in university laboratories are being used to combat mosquito-borne pathogens -- including viruses such as dengue and Zika -- in many countries. Huge progress is also being made in using GM mosquitoes to combat malaria, the world’s most devastating mosquito-borne disease.

Malaria, which is carried by the aedes family of mosquitoes, still infect more than 700 million people annually. More than one million of these people die from malaria.

The project in China that begun two years ago, saw the release of more than 200 million GM male Asian tiger mosquitoes on Shazai and Dadaosha islands in the delta to the south of Guangzhou city. This area has the highest number of dengue fever cases in China.

The GM mosquitoes, Aedes albopictus, were exposed to short bursts of gamma radiation. They also received three artificially induced infections from three different species of Wolbachia, a parasitic microorganism, to make them infertile.

The males were also fed with sugar in the hope of making them bigger and stronger, and therefore more attractive to female mosquitoes during the mating season.

These steps combined with the sheer numbers of the infertile mosquitoes was intended to tip the evolutionary balance by ensuring the females’ eggs -- if any were laid at all -- would not hatch. And that’s what happened.

Chinese researchers let loose more than 140 million GM male mosquitoes on the 3 square kilometer-long Shazai island. The number of mosquitoes released equated to 72,000 mosquitoes for every one of the island’s 2,000 residents. Only female mosquitoes bite. Males are only used for sexual reproduction.

At the end of the two-year experiment, the native mosquito populations of Aedes albopictus on the two islands had been eliminated.

Scientists later found a few individual mosquitoes alive on the islands, but genetic analysis suggested their origins lay elsewhere and they had probably been carried there by cars or ships.

The study detailing this experiment was published in the latest edition of the journal Nature. The research was led by Prof. Xi Zhiyong from the Sun Yat-sen University-Michigan State University Joint Center of Vector Control for Tropical Diseases, with official support from the Guangzhou Center for Disease Control and Prevention.

Dengue Aedes aegypti mosquitoes are seen at the Laboratory of Entomology and Ecology of the Dengue Branch of the U.S. Centers for Disease Control and Prevention in San Juan, March 6, 2016. Picture taken March 6, 2016. REUTERS/Alvin Baez

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