Mosquito parasite may help fight dengue fever

May 01, 2009
mosquito
A female mosquito of the Culicidae family (Culiseta longiareolata). Image: Wikipedia

Dengue fever is a terrible viral disease blighting many of the world's tropical regions. Carried by mosquitoes, such as Aedes aegypti, 40% of the world's population is believed to be at risk from the infection. What is more, previous exposure to other strains of the fever does not confer protection. In fact, subsequent infections are significantly worse, and can result in fatal dengue haemorrhagic fever.

The lack of a functioning vaccine forced Scott O'Neill and Elizabeth McGraw to look for a more creative form of defence. Knowing that a parasite, Wolbachia pipientis, shortens the lifespan of host insects and could restrict dengue fever transmission by killing the insects before they can pass the infection on, O'Neill and his team successfully infected Ae. aegypti with a strain of the Wolbachia bacterium and shortened the mosquitoes' lifespan.

But before insects carrying the bacterium can be released into the environment, the O'Neill and McGraw teams have to convince international governments that mosquitoes carrying the Wolbachia parasite could successfully limit transmission of the virus. McGraw and O'Neill had to find out how the bacterium affects the mosquito's physiology and behaviour and publish their results in the on May 1 2009.

Knowing that Wolbachia slows down some insects' activity and speeds up others, the team decided to test how the parasite affects Ae. aegypti as they age and the infection takes hold. Working with uninfected and infected mosquitoes produced by Conor McMeniman, Oliver Evans and Eric Caragata used a system designed by Craig Williams to film the activities of male and female mosquitoes as they aged to find how the bacteria affected the insects' activity levels. According to McGraw, the experiments generated a huge amount of video data, so Evans teamed up with Megan Woolfit and David Green to pipe the data to a cluster of workstations to track the insects' movements and analyse their activity levels.

After a year of experimental design, data collection and analysis, it was clear that the infected mosquitoes were more active than the uninfected insects. Most surprisingly, as the mosquitoes aged and the infection took hold, it did not increase their activity levels further.

Having found that the insects became more active in response to their bacterial lodgers, Craig Franklin joined the team to help measure the insects' CO2 production to find how their metabolic rates respond to the parasite. Again, the insects' metabolic rates were higher than those of the uninfected mosquitoes.

So why are the infected insects more active than the uninfected insects? McGraw says there are three possible explanations; the insects are living fast and dying young; the insects are hungrier and consume more energy in their constant search for food; or the bacteria somehow affect the insects' tissues to change their behaviour and increase their metabolic rate. McGraw suspects that the last explanation is the most likely.

Having shown that the activity levels of Wolbachia infected mosquitoes respond to the bacterium, McGraw and O'Neill are continuing to test how the infection affects the insects' biting behaviour and whether a Wolbachia infection can become established in Ae. aegypti populations to limit their lifespans. Ultimately, McGraw and O'Neill hope to release infected into afflicted regions of the world to limit dengue fever transmission, but only once they are sure that the will do no harm to the environment.

More information: Evans, O., Caragata, E. P., McMeniman, C. J., Woolfit, M., Green, D. C., Williams, C. R., Franklin, C. E., O'Neill, S. L. and McGraw, E. A. (2009). Increased locomotor activity and metabolism of Aedes aegypti infected with a life-shortening strain of Wolbachia pipientis J. Exp. Biol. 212, 1436-1441. jeb.biologists.org

Source: The Company of Biologists (news : web)

Explore further: Fighting bacteria—with viruses

add to favorites email to friend print save as pdf

Related Stories

Scientists closing the zap on dengue fever

Jan 01, 2009

(PhysOrg.com) -- A mosquito-borne virus that each year harms up to 100 million people and kills more than 20,000 is a step closer to being controlled after a breakthrough by Queensland scientists.

Taking the sting out of insect disease

Oct 31, 2008

(PhysOrg.com) -- University of Queensland researchers have made a discovery that could open up a new front in the fight against insect-transmitted diseases.

Recommended for you

Fighting bacteria—with viruses

Jul 24, 2014

Research published today in PLOS Pathogens reveals how viruses called bacteriophages destroy the bacterium Clostridium difficile (C. diff), which is becoming a serious problem in hospitals and healthcare institutes, due to its re ...

Atomic structure of key muscle component revealed

Jul 24, 2014

Actin is the most abundant protein in the body, and when you look more closely at its fundamental role in life, it's easy to see why. It is the basis of most movement in the body, and all cells and components ...

Brand new technology detects probiotic organisms in food

Jul 23, 2014

In the food industr, ity is very important to ensure the quality and safety of products consumed by the population to improve their properties and reduce foodborne illness. Therefore, a team of Mexican researchers ...

Protein evolution follows a modular principle

Jul 23, 2014

Proteins impart shape and stability to cells, drive metabolic processes and transmit signals. To perform these manifold tasks, they fold into complex three-dimensional shapes. Scientists at the Max Planck ...

User comments : 0