The tangential cycle usually involves other mosquito species that will take blood from a variety of animal hosts, thereby posing a considerable threat to humans by acting as bridge vectors ( Kilpatrick et al. WNV can occasionally infect and cause disease in other vertebrate hosts, including humans and horses, but such hosts are considered tangential because they do not generate sufficient viremia to infect mosquito hosts. West Nile virus is primarily maintained in nature by transmission cycles between ornithophilic mosquitoes and passerine avian hosts. Surveillance programs attempt to monitor the distribution of vector species and reduce their populations by treating breeding sites with species-targeted larvicides. 2002) and has caused counties in almost every state to invest in municipal surveillance programs to control the mosquito populations that transmit this pathogen. Since the 1999 outbreak, WNV has spread throughout all of the eastern United States and parts of the west ( Campbell et al. 1999) and involved hundreds of cases of encephalitis and meningoencephalitis in urban areas ( Hayes 2001). An outbreak in the northeastern United States in 1999, however, was the first occurrence of the disease in the western hemisphere ( Lanciotti et al. West Nile virus (WNV), a mosquito-borne flavivirus that is indigenous to Asia, Africa, Europe, and Australia, has historically been ignored as a significant human pathogen because most cases display mild or no symptoms ( Hayes 2001). Our results support other regional studies that found WNV proliferates under drought conditions. Our study showed that certain landscape variables identified using Geographic Information Systems are valuable for predicting primary WNV vector abundance in Virginia, and that temperature along with low precipitation are strong predictors of population growth. No measure of urbanization examined in our study was correlated with Aedes albopictus abundance. restuans, and our findings implicate combined sewer overflow systems as large contributors to Culex vector populations. Urban infrastructure was positively correlated with the abundance of Culex pipiens L./ Cx. Test results of mosquito pools were compared to average site abundance from 37 sites in Henrico County, VA abundance was then examined in relation to ecological variables. Mosquitoes were collected throughout the 2005, 2006, and 2007 seasons and tested for West Nile virus (WNV) in pools of 10–50. We compared abundance of vector species between urban and suburban neighborhoods of Henrico County, VA, in relation to the following factors: temperature, precipitation, canopy cover, building footprint, and proximity to drainage infrastructure. It is currently unclear if the potential for West Nile virus transmission by mosquito vectors in the eastern United States is related to landscape or climate factors or both.
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