AsianScientist (Aug. 25, 2011) – The spread of dengue fever in northern Australia may be controlled by a bacterium that infects mosquitoes that harbor the virus, Australian and US researchers report today in two papers published in the journal Nature.
The result grew out of work more than 20 years ago by population biologist Michael Turelli, professor of evolution and ecology at UC Davis, and Ary Hoffmann, now at the University of Melbourne, Australia, among the co-authors on the paper.
Dengue fever is caused by four virus strains spread by the mosquito Aedes aegypti. The disease causes high fever and has been called “breakbone fever” because of the joint aches and muscle pains it causes.
Dengue viruses can also cause a potentially fatal disease, dengue hemorrhagic fever, in people who have previously been infected with a different strain of the virus.
Dengue viruses are found throughout the tropics and subtropics and appear annually in northern Australia. The researchers released mosquitoes infected with the bacterial parasite Wolbachia, which suppresses the virus, and now report that the Wolbachia parasite spreads rapidly through the wild mosquito population.
“The results show we can completely transform local populations in a few months,” Turelli said.
Wolbachia is transmitted by female mosquitoes to their offspring. A pair of infected mosquitoes produce slightly fewer eggs than an uninfected couple, but when an infected male mosquito mates with an uninfected female, she produces no eggs at all. That provides a big reproductive advantage to the spread of Wolbachia-infected mosquitoes, generation by generation.
“It’s natural selection on steroids,” Turelli said.
It turns out that Wolbachia also suppresses various other microbes living in the same mosquito – including the dengue virus. As these virus-resistant mosquitoes spread through the wild population, dengue transmission should dry up.
Turelli and Hoffmann first described what turned out to be Wolbachia spreading among Drosophila flies in California’s Central Valley in 1991, and Barton developed much of the relevant mathematics in the late 1970s while trying to understand the genetics of grasshoppers in the French Alps. That basic research by Turelli, Hoffman and Barton provides the biological and mathematical basis for the dengue control strategy.
“At the time, none of us expected that this original research might contribute to human health. This is very exciting, once-in-a-lifetime opportunity,” Turelli said. “We never thought this would turn into an eradication project.”
The Gates Foundation is providing further funding to support release of infected mosquitoes in Australia, Vietnam, and Thailand.
The articles can be found at:
Source: University of California – Davis.
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#Australia #Australian Research Council #Bacteria #Bill and Melinda Gates Foundation #Dengue #James Cook University #Monash University #National Health and Medical Research Council Australia #Queensland Institute of Medical Research #Thailand #University of Melbourne #University of Queensland #Vietnam