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

Center for Vector Biology & Zoonotic Diseases, The Connecticut Agricultural Experiment Station, 123 Huntington Street, New Haven, CT 06511, USA.
Journal of the American Mosquito Control Association (Impact Factor: 0.95). 12/2012; 28(4 Suppl):137-51. 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.

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    • "Culex species are the major vector of West Nile Virus disease in the United States. In the southeast U.S., about 65% of WNV positive Culex mosquito pools reported to CDC from 1999 to 2010 have been obtained from Culex quinquefasciatus (Andreadis, 2012). In the state of Georgia, and especially in Atlanta a noticeable amount of human cases, viremic blood donors and WNV positive mosquitos reported in 2012 to Georgia Department of Public Health reported. "
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    ABSTRACT: Culex quinquefasciatus, the southern house mosquito, is widely distributed in the southeast United States and has increased the West Nile Virus positive mosquito pools. Especially Georgia and Atlanta area, has been a hotspot of WNV incidence in 2012 with 117 WNV human cases, 6 deaths and 125 WNV positive mosquitos reported by Georgia Department of Public Health. To control mosquito populations and to prevent the disease, understanding this vector–environment relationship is essential. Climatic variability is an important driver of inter-annual WNV transmission risk. To describe the variations in abundance over time and to investigate the correlation between climate forces and inter-annual and seasonal variation of WNV transmission risk, cross-correlation maps (CCMs) were developed for four weeks moving average data from the central north part of the State of Georgia (GA). Using this method, the key antecedent environmental conditions, their timings, and durations were identified which can help improve the ability of developing predictive models of vector abundances. The interval lags with the highest correlation value were selected and were fed into the Poisson regression model and also to Artificial Neural Network (ANN) model for the prediction purposes. In addition, Culex vector abundance 1 to 3 weeks prior to the events were added to both models as predictors. Results of the CCMs and the regression model revealed that cold late winter and early spring decreased mosquito population. Also higher than normal moisture in spring favored Culex mosquitoes carrying WNV in summer. The ANN model predicted the seasonal cycle of mosquito abundance fairly accurately. This model can be used for planning of mosquito control strategies and simulation of mosquito borne diseases by considering climate data as the main driver of WNV risk.
    Full-text · Conference Paper · May 2015
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    • "vectors to mammalian hosts (Andreadis 2012). In Austria, WNV (lineage 2) was detected for the first time in 2008 in birds of prey (Wodak et al. 2011) and was later isolated from Cx. pipiens (Bakonyi et al. 2013). "
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    ABSTRACT: Mosquitoes (Diptera: Culicidae) are important vectors for a wide range of pathogenic organisms. As large parts of the human population in developed countries live in cities, the occurrence of vector-borne diseases in urban areas is of particular interest for epidemiologists and public health authorities. In this study, we investigated the mosquito occurrence in the city of Vienna, Austria, in order to estimate the risk of transmission of mosquito-borne diseases. Mosquitoes were captured using different sampling techniques at 17 sites in the city of Vienna. Species belonging to the Culex pipiens complex (78.8 %) were most abundant, followed by Coquillettidia richiardii (10.2 %), Anopheles plumbeus (5.4 %), Aedes vexans (3.8 %), and Ochlerotatus sticticus (0.7 %). Individuals of the Cx. pipiens complex were found at 80.2 % of the trap sites, while 58.8 % of the trap sites were positive for Cq. richiardii and Ae. vexans. Oc. sticticus was captured at 35.3 % of the sites, and An. plumbeus only at 23.5 % of the trap sites. Cx. pipiens complex is known to be a potent vector and pathogens like West Nile virus (WNV), Usutu virus (USUV), Tahyna virus (TAHV), Sindbis virus (SINV), Plasmodium sp., and Dirofilaria repens can be transmitted by this species. Cq. richiardii is a known vector species for Batai virus (BATV), SINV, TAHV, and WNV, while Ae. vexans can transmit TAHV, USUV, WNV, and Dirofilaria repens. An. plumbeus and Oc. sticticus seem to play only a minor role in the transmission of vector-borne diseases in Vienna. WNV, which is already wide-spread in Europe, is likely to be the highest threat in Vienna as it can be transmitted by several of the most common species, has already been shown to pose a higher risk in cities, and has the possibility to cause severe illness.
    Full-text · Article · Dec 2014 · Parasitology Research
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    • "In conclusion, the results of this study provide useful data on the effect of temperature and sex on adult longevity of Cx. pipiens f. pipiens and consequently contribute to our understanding of the presence/absence of WNV under cool/warm conditions. Knowledge of the critical temperatures Cx. pipiens f. pipiens is very useful for determining the climate conditions that affect its spread northward and into higher elevations in terms of climate change and for predicting its large epidemiological impact (Andreadis 2012). However, for a more accurate evaluation of the impact of temperature on insect distribution , spreading, and biology in terms of WNV transmission, additional work is needed on other biological parameters, such as larval density, fecundity, population dynamics, larval diet, etc., preferably under field conditions. "
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    ABSTRACT: The common house mosquito, Culex pipiens (Diptera: Culicidae), which is considered the primary bridge vector of West Nile Virus (WNV) to humans, is a wide spread insect pest with medical importance and consists of two distinct bioforms, Cx. pipiens f. pipiens and Cx. pipiens f. molestus. Here, we consider the adult lifespan of male and female Cx. pipiens f. pipiens under controlled conditions at five constant temperature regimes (15, 20, 25, 27.5, and 30 °C). Our results show that adult longevity was affected by temperature, as it significantly decreased with increase in temperature. At the highest tested temperature, mean adult longevity did not exceed 12 days for both sexes and thus makes impossible the risk of WNV transmission. On the other hand at the lowest temperature, longevity was extremely high with some individuals surviving up to 129 and 132 days, males and females, respectively, and thus enable them to function as potential vectors of WNV for a prolonged period of time. As far as sex is concerned, adult females displayed a 1.2–1.4-fold longer longevity compared to the male ones. However, this difference was significant only at the lowest and highest tested temperature regime. This information is useful in determining the critical temperatures which may affect the distribution of Cx. pipiens and consequently the risk of WNV transmission. Moreover, the effect of environmental temperature should be considered when evaluating the abun-dance of these species.
    Full-text · Article · Sep 2014 · Parasitology Research
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