Stopping Dengue with a Disease-Free Mosquito

Health workers sprayed the streets of Colombo, Sri Lanka, in June to kill dengue-spreading mosquitoes. New research offers a more environmentally friendly way to beat dengue

by Charleen Porter
IIP Staff Writer
25 August 2011

Washington — Introducing a particular bacterium into the reproductive cycle of the Aedes Aegypti mosquito may stop transmission of the virus that causes dengue fever in humans. A consortium involving North Carolina State University (NCSU) and several Australian institutions reports this finding in the August 25 edition of Nature.

The bacterium Wolbachia occurs naturally and is not harmful to humans. The researchers, with backing from the nonprofit organization Eliminate Dengue, infected female mosquitoes with Wolbachia. They bred those mosquitoes with Aedes Aegypti carrying dengue, and found that the bacterium blocked transmission of the dengue virus to the offspring.

Then they worked to find out how quickly this mosquito match-up might eliminate dengue in the controlled population used in the research. They found that one particular strain of Wolbachia could purge the insects of dengue within a few generations.

NCSU’s Alun Lloyd, a mathematical biologist, devised a mathematical model that helped the researchers determine how fast the cross-breeding might produce the desired results.

“This is a simple, nonchemical, nonharmful way to reduce the threat of dengue to humans,” Lloyd said in an NSCU press release. “It could have a transformative effect on the health of literally millions of people worldwide.”

An estimated 50 million people annually are affected by dengue, according to the World Health Organization (WHO). The disease induces a severe flu-like illness and can advance to potentially lethal dengue hemorrhagic fever (DHF). The disease was first identified in the 1950s amid outbreaks in the Philippines and Thailand. The disease prevalence has expanded widely in the ensuing decades in the tropical and semi-tropical regions where the mosquito vector thrives. WHO reports that in 2007 alone, nations of the Americas recorded almost 900,000 cases.

The disease now occurs naturally in the environment in more than 100 countries across many regions: Africa, the Americas, Eastern Mediterranean, South Asia, Southeast Asia and the Western Pacific. The last two regions are the most severely affected with DHF, as the disease has become a leading cause of hospitalization and death among children.

As many as 500,000 people require hospitalization each year for DHF, according to a WHO fact sheet, but, with proper treatment, death rates can be held to less than 1 percent.

Research is ongoing to develop a vaccine.

Eliminate Dengue is funded by the Foundation for the National Institutes of Health through the Bill & Melinda Gates Foundation’s Grand Challenges in Global Health initiative. The group receives further funding from the Australian government.