Researchers have successfully infected a mosquito population with a bug that makes them unable to transmit dengue fever to humans.
The bacterium, Wolbachia pipientis, is known naturally to infect many insect species, and is able to interfere with its host's reproduction so that entire populations are infected within just a few generations.
A few years ago, researchers at Monash University, Australia, were able to block dengue infection completely in Aedes aegypti mosquitoes by infecting them with a Wolbachia strain isolated from fruit flies, says an article in ScienceNOW. But the infection halved the mosquitoes' lifespan, potentially hampering their ability to outcompete wild, uninfected counterparts.
Now, Australian and US researchers have found that a milder strain of Wolbachia — which does not affect the mosquitoes' lifespan — is still highly effective in preventing dengue transmission by the mosquitoes. When they tested the Wolbachia strain in caged mosquitoes, all of them quickly became infected with it.
The researchers then released the infected mosquitoes into the wild in two towns in northern Australia. In each town, up to 20,000 mosquitoes were released each week for ten weeks. Six weeks after the final release, they had passed the infection on to almost all of the wild mosquitoes in both towns. The study did not test whether this had any effect on the presence of dengue fever, caused by a virus which is transmitted to humans through mosquito bites.
The next step is for the researchers to carry out field tests in four endemic countries — Brazil, Indonesia, Thailand and Vietnam — to see whether the Wolbachia-infected mosquitoes can help prevent dengue transmission.
They hope to start these tests within a year. "We wanted to start in our own backyard," Scott O'Neill lead researcher, told ScienceNOW, to show that the mosquitoes are safe and avoid accusations that people in developing countries serve as guinea pigs.