Scientists use bacteria to stop dengue virus spread

Researchers in Australia have discovered that injecting the Wolbachia bacteria into mosquitoes can block them from transmitting the dengue virus, a disease that kills 20,000 people annually.  
Professor Scott O'Neill and his colleagues also found that female mosquitoes infected with the bacteria passed the bug easily to their offspring, making them all dengue-free. They said that by releasing such mosquitoes out into the wild, the spread of dengue to humans may be reduced, Reuters reports.
"The main feature we saw was their ability to reduce dengue transmission," O'Neill, the science faculty dean at Monash University, said, according to Reuters. "It almost completely abolished dengue virus in the body of the mosquito."
In the experiment, O'Neill and his colleagues injected the bacteria into over 2,500 embryos of Aedes aegypti mosquitoes that can spread dengue fever. After hatching, the mosquitoes were treated to bloodmeal laced with the dengue virus. None picked up the virus.
"The (Wolbachia) bacteria doesn't spread environmentally, it gets passed on from mother to children through the eggs," O'Neill said, according to Reuters. "When an infected male mates with an uninfected female, all her eggs die. That gives an indirect benefit to the females with Wolbachia because when they mate with infected males, their eggs hatch normally ... all their eggs have Wolbachia in them so Wolbachia gets more and more common with every generation."
O'Neill said that there were two theories as to why the Wolbachia was able to block dengue uptake - the bacteria boosts the immune system of the mosquito and also competes with the dengue for food inside the mosquito, making it more difficult for the virus to replicate.
O'Neill's team released close to 299,000 infected mosquitoes in January at over 370 sites in northeastern Australia, Reuters reports. The bacteria spread into the wild mosquito population successfully, with their offspring also infected over a three month period. The team is seeking approval to release such infected mosquitoes into dengue-endemic sites as well.
Over 50 million people in more than 100 countries fall sick and 20,000 die each year from dengue fever. There is no specific treatment or vaccine for the disease.