Emerging Vectors in the Culex pipiens Complex

Abstract

In the Old World, some mosquitoes in the Culex pipiens complex are excellent enzootic vectors of West Nile virus, circulating the virus among birds, whereas others bite mainly humans and other mammals. Here we show that, in northern Europe, such forms differing in behavior and physiology have unique microsatellite fingerprints with no evidence of gene flow between them, as would be expected from distinct species. In the United States, however, hybrids between these forms are ubiquitous. Such hybrids between human-biters and bird-biters may be the bridge vectors contributing to the unprecedented severity and range of the West Nile virus epidemic in North America.

Genetic Differences BetweenCulex pipiensf. molestus andCulex pipiens pipiens(Diptera: Culicidae) in New York

“…p. pipiens. Alternatively, microsatellite data generated by Fonseca et al (2004) supports a hypothesis that Cx. p. pipiens and Cx.…”

“…pipiens f. molestus by using infrared spectrometry. Recently Fonseca et al (2004) reported unique microsatellite signatures among worldwide populations of Cx. p. pipiens and Cx.…”

Evolutionary history of a mosquito endosymbiont revealed through mitochondrial hitchhiking

“…ND4 sequences from Culex restuans (Baltimore Co., MD) and Culex tarsalis (Kern Co., CA) were obtained as out group taxa and deposited in GenBank under accession numbers AY788866-AY788867. Primer sequences and PCR conditions were as stated by Gorrochotegui-Escalante et al (2000). Amplified fragments were separated, purified and sequenced as described above.…”

“…Both subspecies have a global distribution and complicated population structure. For example, in North America and Asia extensive gene flow occurs between subspecies (Tabachnick & Powell 1983;Urbanelli et al 1997;Fonseca et al 2004), whereas in some parts of Africa gene flow between subspecies is partial (Urbanelli et al 1985(Urbanelli et al , 1995 or restricted ( Jupp 1978;Cornel et al 2003). Depending on location, members of this complex can be important vectors of nematodes that cause lymphatic filariasis and arboviruses such as St Louis encephalitis, West Nile and Rift Valley fever viruses (Hoogstraal et al 1979;Krida et al 1998;Day 2001;Nasci et al 2001;Fonseca et al 2004).…”

“…Mitochondrial DNA sequences have been shown to be useful markers for studying the structure of medically important insect populations such as mosquitoes, tsetse flies (Glossina morsitans) and sand flies (Phlebotomus papatasi; Gorrochotegui-Escalante et al 2000;Krafsur et al 2000;Donnell et al 2001;Krafsur et al 2001;Gorrochotegui-Escalante et al 2002;Parvizi et al 2003;Marquez et al 2004). Patterns of mitochondrial variability can be confounded, however, by the spread of maternally inherited symbionts such as Wolbachia (Turelli & Hoffmann 1999;Hurst & Jiggins 2005).…”