Infection cuts mosquitoes' lives short

By Pauline Askin

SYDNEY (Reuters) - Infecting mosquitoes with a common bacteria can cut their lives short and reduce the likelihood they will transmit dengue and other diseases, Australian researchers reported on Friday.

They genetically engineered bacteria known as Wolbachia so they would infect the Aedes aegypti mosquito species that carry the dengue virus, and found infected mosquitoes lived half as long as uninfected mosquitoes.

This could reduce the chances they will transmit the virus to people, as the virus takes about two weeks to mature and become infectious inside a mosquito's body, they report in Friday's issue of the journal Science.

"Dengue virus and the disease it causes is only transmitted to humans by the older female Aedes aegypti mosquito," said Scott O'Neill, head of University of Queensland's School of Biological Science.

"If we can introduced this into populations it should move the management of dengue fever from an outbreak management paradigm to a prevention paradigm," O'Neill said in a telephone interview.

Wolbachia bacteria, which occur naturally in fruit flies, allowed the mosquito to live long enough to reproduce and spread to its young, but not to mature to the stage when it is capable of transmitting dengue.

There is no vaccine or cure for dengue fever, which is a painful and debilitating disease also known as breakbone fever. When it takes on a hemorrhagic form it can kill, and dengue kills 22,000 people a year.

"Dengue around the world is getting worse now. We are seeing more and more activity around the world including Australia," said O'Neill.

His team hopes to infect a caged population of mosquitoes in Australia's tropical Queensland state. More than 50 cases of dengue have been confirmed in northern Queensland since November.

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

"Ultimately we would like to see if it could be applied to other diseases transmission systems like malaria, which we are currently working on as well," he said.

The researchers now need to show that Wolbachia will spread naturally among mosquitoes the way they do among fruit flies, Andrew Read and Matthew Thomas of Pennsylvania State University said in a commentary.

And then it is possible that dengue viruses would evolve the ability to multiply more quickly inside a mosquito's body, they noted.

(Reporting by Pauline Askin; editing by Maggie Fox and Mohammad Zargham)