Africa: Scientists Crack Mosquito Code

Scientists have released the draft sequence of the genome of Aedes aegypti, the mosquito that spreads dengue fever, yellow fever and chikungunya.

The sequence is published online today (17 May) in the journal Science.

The genetic information could ultimately help control mosquito populations and the spread of disease, say the scientists.

"We expect that the genome sequence will accelerate basic research in the mosquito biology, particularly the ability of A. aegypti to transmit yellow fever, dengue and chikungunya," Vishvanath Nene from the US-based Institute for Genomics Research and author on the study told SciDev.Net.

The authors write that the genome sequence of A. aegypti represents a "significant technical achievement" that will throw light on the interactions at the molecular level between the mosquitoes and the pathogens they spread.

For example, the researchers expect it will help identify the genetic code of the receptors in A. aegypti's gut that the dengue virus attaches to.

The researchers were able to compare the A. aegypti genome with that of Anopheles gambiae, the mosquito that transmits malaria.

Nene says scientists can now begin to address questions such as why does A. gambiae transmit the malaria pathogen and A. aegypti the yellow fever, dengue and chikungunya pathogens.

Genetic differences may also explain their blood feeding preferences, the kind of hosts they seek and individual abilities to transmit certain pathogens.

Nene's team also compared the A. aegypti genome with that of the fruit fly Drosophila melanogaster and say the differences could shed light on which genes and gene activities are specific to mosquitoes. They hope this will allow them to identify potential target genes to use in mosquito control.

In addition, information about the genes that control sex determination means that mosquito sex ratios could be manipulated, which may be useful for population control.

According to the World Health Organization, there are 50 million cases of dengue fever each year. Yellow fever is a major problem in Africa and South America, with over 200,000 cases each year, and 30,000 deaths.

Outbreaks of chikungunya have been reported in Gabon, India, the Maldives, Pakistan and Sri Lanka, with 1.25 million cases in India alone in 2006.

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