Infecting Mosquitoes With Contagious Gonad-Attacking Bacteria Could Block Dengue Fever

The fight against mosquito-borne Dengue fever is ongoing in more than 100 countries all over the world, but in Australia...

By Clay Dillow | Published Aug 25, 2011 10:08 PM EDT

Science

The fight against mosquito-borne Dengue fever is ongoing in more than 100 countries all over the world, but in Australia the gloves are off and researchers are going right for the gonads. Using a bacterial parasite known as Wolbachia, researchers have found a way to block out Dengue in mosquitoes, making it impossible for them to transmit it to humans.

Wolbachia comes in several flavors–almost all of which manifest themselves in the gonads as well as other organs–but the particular one researchers have identified here has a unique property: when an infected male mates with an uninfected female, the female dies. And when an infected male mates with an infected female, the offspring live–but they all carry the Wolbachia infection with them, ensuring its further spread through a population.

This, of course, solves a major problem with mosquito control. Spraying insects with insecticides helps them to develop resistance to poisons. And biological agents that kill them off don’t proliferate within the population, so the solution is temporary–the next season, new mosquitoes move in and it’s back to square one.

But the Wolbachia-infected mosquitoes go on to live long and fruitful lives, spreading the infection to their offspring as they go. And the bacterial infection has a key trait: it’s really bad at sharing. Where Wolbachia takes hold, it is loathe to give up ground to other infections–like Dengue. Other infectious things, including viruses, just don’t grow well where Wolbachia has already put down roots.

That’s good news. Even better, the researchers have already taken their strain of Wolbachia for a test-drive in two Australian towns. In one town, the infection rate among mosquito populations was nearly total. In the other, it topped 90 percent. There’s plenty more that needs to be learned about Wolbachia and its expression before it can be rolled out more widely–like whether or not the infection will pick up again after the dry season in which mosquito mating behaviors and populations change drastically. But given that Dengue fever touches 50 million people a year, it’s a promising start.