Itchy from mosquito bites?
Scientists have wiped out the entire population of mosquitoes on two islands in southern China, using a radical technique to make the males infertile.
The study, published in the journal Nature, could transform the fight against a range of deadly diseases carried by mosquitoes.
Over nearly two years, scientists released more than 200 million specially bred male Asian tiger mosquitoes on the Shazai and Dadaosha islands in the delta to the south of Guangzhou, the area with the highest number of dengue fever cases in China.
The mosquitoes, also known as Aedes albopictus, had been exposed to short bursts of gamma radiation and 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.
This, combined with the sheer weight of numbers of the infertile mosquitoes, was intended to tip the evolutionary balance by ensuring that the females’ eggs, if any were laid at all, would not hatch.
By the end of the experiment, the native mosquito populations on the islands had vanished completely.
The scientists did find a few individual mosquitoes still living on the islands, but genetic analysis suggested their origins lay elsewhere and that they had probably been carried there by cars or ships.
Asian tiger mosquitoes are so named because of their distinctive white stripes. They can transmit a range of diseases, including the Zika and West Nile viruses as well as dengue fever.
Even so, many islanders were initially skeptical about the project. They felt uncomfortable about having so many mosquitoes into their neighborhood, even if they didn’t bite.
But by the end of the experiment, opinion polls showed that almost all the locals supported, or at least did not oppose, the project after the number of bites recorded fell by more than 96%.
“In the past there were so many mosquitoes we dared not stay outside in late afternoon. Now mosquitoes can barely be seen, and those few remaining rarely bite,” a Shazai restaurant owner surnamed Li said in a phone interview.
“The technology is a miracle. We used to be sceptics. Now we are fans.”
The ecological impact of this mosquito-killing project poses a dilemma for scientists. Photo: AP/LM Otero
The government-run mosquito-breeding facility in the southern province of Guangdong can produce 10 million modified males a week, but the ecological impact of this project poses a dilemma for scientists.
Mosquito larvae is an important food source food fish, while the fully grown insects serve as prey for birds.
But a survey conducted by Nature in 2010 suggested that most biologists would prefer to see mosquitoes wiped out completely because they carried a lot of deadly diseases.
They kill more than 700,000 people around the globe each year, according to some studies, which makes them the most deadly creatures of all for humans.
STEPHEN CHEN
Stephen is a contributor to Inkstone. He covers science and its impact on society, as well as the environment, military, geopolitics and business for the South China Morning Post. |
