THE VICTORY AGAINST DENGUE IS COMING UP AT LAST???

[Reproduced from "Creatology", a blog of Gozde Zorlu, published in SCIENTIFIC AMERICAN]
Every year, 50-100 million people are infected with the dengue fever virus, which is transmitted to humans through the bites of female Aedes aegypti mosquitoes, mainly in South East Asia and South America. With no vaccine and no specific treatment, serious complications arise in around 500, 000 cases and 22, 000 deaths. It is a leading cause of hospitalisation and death among young children and it can place a considerable financial strain on middle to low income families in developing world countries.

So the development of a new control to stop the virus comes as welcome news. Two studies published in Nature show that the spread of dengue fever through a wild mosquito population could be prevented by infecting mosquitoes with a common bacterium called Wolbachia pipientis.

“The presence of the Wolbachia in the mosquito completely blocks the ability of the dengue virus to be able to grow. If it can’t grow in the mosquito, then it can’t be transmitted between people,” said Scott O’Neill, co author of the studies, from the University of Queensland, Australia.

In the first study, the researchers transferred a strain of the Wolbachia bacteria from fruit flies to mosquitoes. They discovered that the bacteria inhibited the growth of the dengue fever virus and had very little effect on the mosquito otherwise in terms of health and lifespan.

The next stage of the research involved the release of 300, 000 mosquitoes infected with the bacteria into the wild in two remote towns in Australia. After five weeks, the researchers found that almost all of the wild mosquitoes were infected with the bacteria.

“There has been intense interest in developing and disseminating mosquitoes that cannot transmit dengue, but the roadblock to this approach has been that mosquitoes modified to resist dengue tend to have lower fitness than wild type mosquitoes and to die out when mixed with wild type mosquito,” said Kathryn Hanley, an associate professor of biology, who was not involved in either study, from the New Mexico State University, USA.

“In this context, the development of a Wolbachia strain that both limits dengue transmission and spreads through a natural population is extremely significant,” she said.

It is uncertain how the Wolbachia is able to suppress the virus but the researchers believe that the bacteria might boost the immune system of the mosquito to help it to fight off the virus or that the bacteria competes for key molecules, such as fatty acids, that the virus needs to replicate. “The jury is still out on which of those two mechanism is critical, or it might be a combination of both,” said O’Neill.
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The researchers hope to test the new approach in endemic countries, such as, Vietnam, Thailand, Indonesia and Brazil over the next year.

[More about this can be seen in http://blogs.scientificamerican.com/creatology/2011/08/27/the-fight-against-dengue-fever-continues/]