The Contribution of Culex pipiens Complex Mosquitoes to Transmission and Persistence of West Nile Virus in North America

ArticleinJournal of the American Mosquito Control Association 28(4 Suppl):137-51 · December 2012with27 Reads
DOI: 10.2987/8756-971X-28.4s.137 · Source: PubMed
Mosquitoes within the Culex pipiens complex have been implicated as major vectors of West Nile virus (WNV) in North America due to their seasonal abundance, vector competence and high field infection rates. However, the role of Cx. p. pipiens complex mosquitoes in enzootic amplification of WNV among avian hosts and epidemic transmission to humans varies throughout its geographical distribution. In the northeastern United States, Cx. p. pipiens is recognized as the primary enzootic vector responsible for amplification of virus among wild bird populations. However, because this mosquito is strongly ornithophilic, its role in transmission to humans appears to be more limited in this region. In the north central and Mid-Atlantic States by contrast, Cx. p. pipiens shows an increased affinity for human hosts and has been incriminated as a key bridge vector. In southern regions of the United States, Culex p. quinquefasciatus are more opportunistic feeders, and are thought to be principal enzootic and epidemic vectors. In western regions of the United States where Culex tarsalis predominates, especially in rural areas, Cx. p. pipiens and Cx. p. quinquefasciatus play roles that are more limited and are recognized as secondary vectors. In the southwestern United States Cx. p. quinquefasciatus also appears to be the predominant vector in urban habitats, but only a secondary vector in more rural environs. The direct involvement of Cx. p. pipiens form molestus in WNV transmission is largely unknown, but human-biting Cx. p. pipiens are more likely to have a probability of genetic ancestry with Cx. p. pipiens form molestus. The detection of WNV from overwintering populations of diapausing Cx. p. pipiens and non-diapausing Cx. p. quinquefaciatus and their role in local overwintering of WNV are addressed.
    • "To calibrate our infection assay, we used laboratory strains of C. pipiens biotype molestus and C. quinquefasciatus. C. pipiens biotype molestus has been described as a WNV vector in Israel [26] , and C. quinquefasciatus was described by several studies from North America as a competent vector for WNV [14,27, 28]. For the analysis of disseminating infection, frozen mosquitoes were beheaded under a dissection microscope and the body and head were separately homogenized in medium. "
    [Show abstract] [Hide abstract] ABSTRACT: West Nile virus (WNV), a Flavivirus with an avian primary host, is already widespread in Europe and might also pose an infection risk to Germany, should competent mosquito vectors be present. Therefore, we analysed the ability of WNV to infect German Culex mosquitoes with special emphasis on field collected specimens of Culex torrentium and Culex pipiens biotype pipiens. We collected egg rafts of Culex mosquitoes over two subsequent seasons at two geographically distinct sampling areas in Germany and differentiated the samples by molecular methods. Adult females, reared from the various egg rafts, were challenged with WNV by feeding of artificial blood meals. WNV infection was confirmed by real-time RT-PCR and virus titration. The results showed that field collected C. pipiens biotype pipiens and C. torrentium mosquitoes native to Germany are susceptible to WNV infection at 25°C as well as 18°C incubation temperature. C. torrentium mosquitoes, which have not been established as WNV vector so far, were the most permissive species tested with maximum infection rates of 96% at 25°C. Furthermore, a disseminating infection was found in up to 94% of tested C. pipiens biotype pipiens and 100% of C. torrentium. Considering geographical variation of susceptibility, C. pipiens biotype pipiens mosquitoes from Southern Germany were more susceptible to WNV infection than corresponding populations from Northern Germany. All in all, we observed high infection and dissemination rates even at a low average ambient temperature of 18°C. The high susceptibility of German Culex populations for WNV indicates that an enzootic transmission cycle in Germany could be possible.
    Full-text · Article · Dec 2016
    • "The Cx. pipiens complex is viewed as a questionable point in mosquito taxonomy, because species (or forms) are indistinguishable morphologically and can be separated only by molecular analysis [5, 6] or details of behavioral and physiological characteristics [7]. In terms of geographic distribution, Cx. quinquefasciatus differs from Cx. pipiens in that the former is most prevalent in tropical and sub-tropical areas [8, 9]. In the southern United States, Cx. quinquefasciatus is the primary vector of Saint Louis encephalitis virus and West Nile virus [10][11][12]. "
    [Show abstract] [Hide abstract] ABSTRACT: Rapid emergence of most vector-borne diseases (VBDs) may be associated with range expansion of vector populations. Culex quinquefasciatus Say 1823 is a potential vector of West Nile virus, Saint Louis encephalitis virus, and lymphatic filariasis. We estimated the potential distribution of Cx. quinquefasciatus under both current and future climate conditions. The present potential distribution of Cx. quinquefasciatus showed high suitability across low-latitude parts of the world, reflecting the current distribution of the species. Suitable conditions were identified also in narrow zones of North Africa and Western Europe. Model transfers to future conditions showed a potential distribution similar to that under present-day conditions, although with higher suitability in southern Australia. Highest stability with changing climate was between 30°S and 30°N. The areas present high agreement among diverse climate models as regards distributional potential in the future, but differed in anticipating potential for distribution in North and Central Africa, southern Asia, central USA, and southeastern Europe. Highest disparity in model predictions across representative concentration pathways (RCPs) was in Saudi Arabia and Europe. The model predictions allow anticipation of changing distributional potential of the species in coming decades.
    Full-text · Article · Oct 2016
    • "Culex pipiens mosquitoes play an important role in the transmission of pathogens of significant public and veterinary health importance. They are the primary vectors of the Saint Louis Encephalitis in the USA and the West Nile Virus (WNV, Flaviviridae, Flavivirus) in Europe and the USA [1][2][3]. WNV is normally maintained through a bird-mosquito cycle but can be spread to a wide range of incidental hosts, such as horses and humans, where it causes severe neurological disorders [4,5]. Culex pipiens is one of the main vectors of the zoonotic filarial agents Dirofilaria immitis (heartworm) and Dirofilaria repens (subcutaneous filarial worm) [6][7][8]. "
    [Show abstract] [Hide abstract] ABSTRACT: Culex pipiens is an important vector of pathogens of substantial medical and veterinary importance such as Dirofilaria immitis and Dirofilaria repens or the West Nile Virus. The control of these mosquitoes is therefore essential to control the transmission of mosquito-borne agents to humans and animals. A combination of dinotefuran, permethrin and pyriproxyfen (Vectra® 3D) has already shown its efficacy against Aedes aegypti. The aim of this study was to confirm the efficacy of this combination in repelling and killing another species of mosquito, Culex pipiens, after a single topical application to dogs.
    Full-text · Article · Jul 2016
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