By finding a microbial 'mosquito net', scientists have made new progress in the fight against mosquito-borne disease like dengue fever and Chikungunya.
Earlier this year, researchers showed that they could cut the lives of disease-carrying mosquitoes in half by infecting them with a bacterium they took from fruit flies.
And now, in a new report, the researchers have suggested that the Wolbachia bacteria also makes the mosquitoes more resistant to infection by viruses that are a growing threat to humans, including those responsible for dengue fever and Chikungunya.
Once infected with Wolbachia, Aedes aegypti mosquitoes also become less suitable as hosts for a form of malaria parasite that infects birds, said Scott O'Neill of The University of Queensland.
"This might be very powerful in reducing pathogen transmission by Aedes aegypti to humans, particularly for dengue and Chikungunya. Together with the previously described life-shortening effects, the results suggest we might be able to have a major impact on disease," said O'Neill.
But this would be possible if the researchers could show that the Wolbachia infection can invade natural mosquito populations, he added, a question his team is working on right now.
Wolbachia is already rampant in nature- the bacterium is estimated to infect up to 60 percent of all insect species.
"We are currently conducting a series of experiments in contained outdoor greenhouse settings that are examining the ability of the Wolbachia infection to spread into natural mosquito populations. If these prove successful, we hope to move to open field testing within the next one to two years," he said.
The idea would be to seed the natural mosquito population with Wolbachia by releasing mosquitoes that had been purposefully infected in the laboratory.
Wolbachia bacteria have a good 'trick' to help ensure their spread, explained O'Neill.
They are responsible for a developmental defect that makes the would-be offspring of pairings between infected male mosquitoes and uninfected females inviable.
Since the bacteria is passed from mothers to their offspring, that means that infected females can actually have a reproductive advantage over uninfected ones, encouraging Wolbachia's spread from one generation to the next.
While the researchers don't yet know exactly how Wolbachia protects the insects from human disease-causing viruses, but they do have some evidence to suggest that the bacterial symbiont primes the insects' immune system.
Wolbachia may also outcompete the virus by limiting resources such as fatty acids inside the mosquitoes.
Even if the strategy works in a natural setting, there's a chance the mosquitoes or the viruses could become resistant to Wolbachia's influence over time.
"We can predict from evolutionary theory that selection will push the system in the direction of resistance, but we do not know the speed with which this might occur. Even if it was effective for a few decades it might have a major impact on human disease," said O'Neill.
The study has been published in the latest issue of Cell.