Scientists closing the zap on dengue fever

In a paper published in the prestigious international journal Science on January 2, researchers from The University of Queensland have proved the effectiveness of a new way of limiting the lifespan of the type of mosquito that spreads dengue fever.

They have done it by infecting the dengue mosquito, Aedes aegypti, with a bacterium that is harmless to humans and other animals 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 laboratory of Professor Scott O'Neill, Head of 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,” Mr McMeniman said.

The 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.

Professor O'Neill said the project's next stage would be a contained field cage setting in northern Queensland.

“If that proves successful we hope to deploy this new dengue control measure in other parts of Australia, as well as Thailand and Vietnam,” Professor O'Neill said.

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.

The virus is of greatest concern in tropical parts of the developing world but - despite significant investments in insecticides and public awareness campaigns - outbreaks are not uncommon in northern Queensland. More than 50 cases have been confirmed in Cairns in northern Queensland since Nov 27, 2008.

Globally, outbreaks of dengue are becoming more common, and there are concerns that climate change will place more people at risk.

Web site: http://www.mosquitoage.org

Provided by University of Queensland