In a twist on fighting fire with fire, researchers are exploring ways to fight mosquito-borne illness with mosquitoes.

New research published last week in the PLoS Pathogens journal discovered that the Wolbachia bacterium can inhibit dengue viruses from replicating in mosquitoes. The research was conducted by scientists at Michigan State University.

Dengue fever, also known as break-bone fever, threatens 2.5 billion people -- 40 percent of the world's population -- and affects up to 100 million people every year, according to the Centers for Disease Control and Prevention. There is currently no vaccine or treatment for the virus, of which there are four different strains.
About 28 percent of mosquito species carry the Wolbachia bacteria, but the primary source of dengue are the Aedes aegypti species, which do not have the promising bacteria, explains researcher and professor of medical entomology Zhiyong Xi.

Xi began looking at the Wolbachia bacteria about 10 years ago because he saw its potential to control dengue.

"One of the most important points is that the bacteria [used to control dengue] should be able to spread into a wider population," he says. "This [Wolbachia] bacterium has this function."

The scientists studied a strain of the bacteria that makes the mosquitoes live slightly longer than normal, about one week longer, Xi says. This allows the mosquitoes extra time to mate and pass on the virus-fighting bacteria.

A similar, separate study in Australia looked at another strain of the Wolbachia bacteria and found that a particular strain decreased longevity, killing the mosquitoes before it could spread the "good" bacteria.

Based on a mathematical model, Xi prefers that the mosquitoes live longer in order to spread the bacteria to the population.

"Basically, we want mosquitoes to be modified so they will not host the virus," he explains. "These bacteria will have to spread as fast as possible to the entire population....If mosquitoes live shorter lives, the bacteria cannot be spread....If it can't spread, you cannot use this bacterium for dengue control."

An independent report had similar findings with another type of Wolbachia, called popcorn. This was found to inhibit several pathogens, including dengue, chikungunya (fever) and plasmodium (malaria). These findings suggest that Wolbachia may "induce a general killing mechanism in the host or influence common host factors or networks that are required for a variety of parasites," according to Xi's report.

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