ABSTRACT West Nile virus (WNV) is a zoonotic flavivirus that causes disease in both humans and animals. It is maintained and amplified in nature through a cycle of adult female mosquitoes blood-feeding on birds that amplify the virus. In California, one of the key vectors of the virus is Culex tarsalis, a mosquito found primarily in rural areas. The abundance of this species is driven, in part, by climatic conditions that vary at several scales, including temperature and the availability of water. In addition, warm temperatures shorten the incubation period for WNV in mosquitoes, thus increasing transmission efficiency. For my dissertation project, Chapter 1 characterizes the responses of Cx. tarsalis abundance to seasonal climate variation by retrospectively analyzing long-term statewide trapping data from 1966-2001, showing that climate responses vary at a range of scales, from the individual trap level to broader regional effects. Chapter 2 uses a blend of laboratory experiments and statistical modeling to compare the incubation period of recent WNV strains in Cx. tarsalis to the North American founding strain, finding that recent WNV evolution has not favored accelerated incubation. Chapter 3 considers whether realistic daily temperature variation alters transmission of WNV compared to the constant-temperature treatments typically applied in other laboratory studies. I considered a range of temperature scenarios reflecting seasonal patterns in a hyperendemic focus for WNV, with the general findings that WNV transmission is a function of mean temperatures, but mosquito behaviors that affect their exposure to ambient temperatures have important implications for transmission. As a whole, these research findings can be used by mosquito control and public health agencies to assess transmission risk and understand how climate drives WNV emergence.
|Advisor:||Barker, Christopher M.|
|Commitee:||Kass, Philip H., Reisen, William K.|
|School:||University of California, Davis|
|School Location:||United States -- California|
|Source:||DAI-B 77/08(E), Dissertation Abstracts International|
|Keywords:||Arbovirus, Climate, Culex tarsalis, Extrinsic incubation, Model, West nile virus|
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