A bacterium can stop dengue viruses from replicating in the mosquitoes, scientists at Michigan State University have discovered.
Dengue fever - caused by a virus transmitted by mosquitoes - threatens 2.5 billion people each year and there is no vaccine or treatment.
The new finding, therefore, holds significance.
"In nature, about 28 percent of mosquito species harbor Wolbachia bacteria, but the mosquitoes that are the primary transmitters of dengue, Aedes aegypti, have no Wolbachia in them," said Zhiyong Xi, MSU assistant professor of entomology and study author.
"We found that Wolbachia is able to stop the dengue virus from replicating. If there is no virus in the mosquito, it can't spread to people, so disease transmission can be blocked," Xi added.
In earlier work, Xi and colleagues introduced the Wolbachia bacterium into Aedes aegypti mosquitoes by injecting embryos with this parasite. They have maintained the bacterium in the mosquitoes in the lab for nearly six years because it is passed from mothers to offspring.
When a Wolbachia-infected male mates with an uninfected female, the bacterium causes a reproductive abnormality that triggers early embryo death. Wolbachia doesn't affect embryo development when a female contains the same Wolbachia as a male, so the bacterium can spread quickly, infecting an entire mosquito population.
The Wolbachia bacterium can't be passed from mosquitoes to humans.
Another report with similar results was recently published by Australian researchers, though the groups used different strains of the Wolbachia bacterium.
"The strain we used has a 100 percent maternal transmission rate and causes the mosquitoes to live slightly longer. The strain the Australian researchers used causes the mosquitoes to die a bit sooner. There are advantages to both," Xi said.
"The longer the mosquitoes live, the more likely they are to pass on the Wolbachia infection to their offspring and infect the entire population in a shorter timeframe. But if the mosquitoes die earlier, they can't bite people and transmit the dengue virus.
"In both instances, the results demonstrate the potential using the Wolbachia bacterium as a control method for dengue virus," Xi added.
Xi and colleagues are now working to understand how the Wolbachia bacterium stops the dengue virus from replicating in mosquitoes.
"Only when we know the mechanisms underlying Wolbachia-mediated viral interference, will we will be able to why it's happening and further improve the efficiency of the viral interference," he said.
The research has been published in the April 1 issue of the journal PLoS Pathogens.