Assessment of Integrated Mosquito Management and Ecology of Culex Mosquitoes in the Urban Southwest

Abstract

Culex species mosquitoes are responsible for the transmission of West Nile virus (WNV) and other encephalitic viruses within the United States. In Arizona, Culex quinquefasciatus and Culex tarsalis are the principal vectors of WNV and St. Louis encephalitis (SLEV). This research examines the desert ecology of these mosquitoes in the context of vector control. Specifically, the study examines how human land-use and vector control activities influence both mosquito abundance and WNV and SLEV presence. Chapter 1 investigates the efficacy of larvicide applications to public drainage features. Chapter 2 analyzes the relationship between land-use and female mosquito density and virus presence. Chapter 3 assesses the susceptibility of Cx. quinquefasciatus adults to the insecticides commonly used for WNV prevention in Maricopa County, Arizona which is home to the Phoenix metropolitan area. We found that dry well drainage features are an important habitat for Cx. quinquefasciatus mosquitoes, but standard larvicide application techniques have limited efficacy due to the water depth. Suspending either of the larvicides Altosid or Bti/Ls at the same water level as the mosquito immatures caused significant reduction on viable larvae. There are many significant associations in adult Cx. quinquefasciatus and Cx. tarsalis density with designated land use throughout the greater Phoenix area. Notably, land areas designated as agriculture and active open space were positively associated with mosquito density, while single and multi-family residential areas, golf courses, and vacant space were negatively associated. The odds of finding virus-infected mosquito pools were higher residential areas, agriculture, and active open space land use categories and lower in industrial, commercial, and business areas, golf courses, inactive open space areas, and vacant areas. Pyrethroid class adulticides have been used exclusively in Maricopa County for mosquito control purposes. Mosquito immatures were collected from six different 1-mile square blocks within the cities of Chandler and Gilbert, Arizona, near Phoenix. Immatures were raised until adults and then tested using the CDC bottle bioassay against active ingredients in insecticides used for mosquito control by Maricopa County. All mosquitoes demonstrated exceedingly high levels of resistance to all insecticides tested. The research in this dissertation provides meaningful data on Culex mosquito ecology and control in the desert southwest. This information can be used by vector control agencies to improve mosquito surveillance and control.