Genome Of West Nile Mosquito Decoded By International Team Of Scientists

The genome, or DNA code of the mosquito (Culex pipens quinquefasciatus) that transmits West Nile virus has been decoded by scientists from various countries, an article published in Science reveals. The mosquito also transmits the St. Louis encephalitis virus as well as the tiny worm which causes elephantiasis.

Researchers from 39 universities in the USA and Europe reported in two separate papers published in the journal Science that they had mapped the DNA of the Southern House Mosquito (Culex pipens quinquefasciatus), all the 18,883 genes.

Co-author, Stephen Higgs, a professor at the University of Texas Medical Branch at Galveston (UTMB), said:

Culex pipiens quinquefasciatus is the most widely distributed mosquito in the world, and in terms of disease transmission to humans it’s one of the three most important mosquito species. This work gives us a terrific platform to improve our understanding of the dynamics of infection, which has to be done if we’re going to find ways to interrupt disease transmission.

Higgs had identified the genome of the malaria-transmitting mosquito Anopheles gambiae, which was published in 2002, and the yellow-fever and dengue fever transmitting mosquito Aedes aegypti, which was published in 2007.

Co-author, UTMB assistant professor Dana Vanlandingham, said:

This is really exciting for us, because we can finally perform experiments that we’ve wanted to do for seven or eight years. Our basic question is why do certain mosquito species transmit a particular virus and other mosquito species do not? Why don’t they all carry all the viruses? We don’t know, but now we have three different systems for comparative studies to investigate interactions between viruses and mosquitoes.

By identifying all the 18,883 genes of the mosquito that transmits West Nile virus, scientists will have greater insight into what determines its behavior and how its immune system reacts to bacterial, viral and parasitical infections.

Higgs said:

Culex quinquefasciatus is the main vector* for West Nile – it’s common here along the Gulf Coast of Texas, but closely related species are found all over the country, and it bites both birds and humans. There have been about a million human infections with West Nile in the United States and, presumably, hundreds of millions of bird infections. Almost every one of those infections was started by a mosquito bite.

*Vector – in medicine a vector means a carrier. For example, in malaria the mosquito is the vector; it carries and transfers the infectious agent (Plasmodium), injecting it with a bite.

The Texas Department of State Health Services informs that 24 human cases of West Nile virus infection have been reported in the state this year, and two deaths.

Ever since the West Nile virus got into the USA in 1999, scientists have been trying to understand the relationship between West Nile and (Culex pipens quinquefasciatus).

Vanlandingham said:

For years we’ve been looking at the interaction of viruses and mosquito gene expression in other mosquito species infected with various viruses, because those were the only systems that were available. We’ve been able to see some parts of the Culex West Nile virus picture, but we haven’t had the appropriate tools for detailed genetic studies. This work will provide the base for a lot of people to investigate mosquito-borne pathogens, from multiple angles.