Sydney: Scientists can now vanquish the dengue-carrying mosquito that infects up to 100 million people and kills more than 20,000 every year.

University of Queensland (UQ) researchers have done it by infecting the mosquito, Aedes aegypti, with a bacterium that is harmless to humans but halves Aedes' lifespan.

This has the potential to greatly reduce dengue because only old mosquitoes are effective at transmitting the virus to humans.

The scientists' success is critical to the progress of a $10 million project funded by the Bill and Melinda Gates Foundation and may lead to a new, safe and cheap way of curtailing dengue fever.

Carried out in the lab of Scott O'Neill, who heads UQ's School of Biological Sciences, the experiment's focus was painstaking work with the Aedes mosquito and Wolbachia, a bacterium that occurs naturally in fruit flies.

PhD student Conor McMeniman used super-fine needles to manually inject 10,000 mosquito embryos with Wolbachia, and encouraged the surviving mosquitoes to feed on his own blood.

"We ended up having to inject thousands of embryos to achieve success, but it was well and truly worth it in the end," McMeniman said.

Researchers have shown that Wolbachia halves mosquitoes' lifespan, which can be up to 30 days in the field. This dramatically curtailed their potential to spread dengue fever, without preventing the hereditary transmission of the bacterium.

There is no vaccine or cure for dengue fever, which is a painful and debilitating disease also known as 'breakbone fever'. Dengue haemorrhagic fever can be lethal, said a UQ release.

The virus is of greatest concern in tropical parts of the developing world. Despite significant investments in insecticides and public awareness campaigns, outbreaks are common.

Globally, outbreaks of dengue are becoming more common, and there are concerns that climate change will place more people at risk as it increases the mosquitos' range.

These findings were published in the international journal Science. IANS