Document Type

Thesis - University Access Only

Award Date

2009

Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

First Advisor

Michael. B. Hildreth

Abstract

West Nile virus (WNv) first appeared in the United States in 1999 , and since that time it has spread throughout most of the states and become the leading cause of arboviral encephalitis . In subsequent years, WNv has remained endemic in varying proportions in most regions of the United States. Since its appearance in 2002 in the northern Great Plains region, this region has experienced the highest cumulative incidence of West Nile virus neuroinvasive disease (WNND) cases. The state of South Dakota has had the highest cumulative incidence of WNND and the highest median annual WNND incidence at the state level for much of this time. In South Dakota, WNv surveillance has produced the following three distinct datasets over multiple years: 1) the types and number of mosquitoes trapped at various collection sites using a carbon dioxide-baited light trap, 2) the number of WNv positive mosquito pools based upon PCR analysis, and 3) the number of human WNv cases reported and confirmed by the South Dakota Department of Health. Using historical data, temporal patterns of mosquito activity affecting WNv transmission were analyzed. Mosquito collections were used in the following ways: 1) the mosquito fauna of South Dakota was defined and compared to previous studies, 2) seasonal temporal patterns of Cu/ex tarsalis population dynamics were characterized over multiple years , and 3) the diel patterns of host-seeking activity for the most prevalent mosquito species were described. WNv mosquito pool data were used in the following ways : 1) the vector competencies of mosquito species in South Dakota were compared, and 2) minimum infection rates (MIR) and vector indexes were calculated. Human WNv cases data were used to define the WNv transmission period. Finally, the three datasets were used together in the following ways: I) yearly temporal correlations with human WNv cases using Cx. tarsalis abundance and positive pool numbers were measured and , 2) capabilities o f Cx. tarsalis abundance and positive pool numbers at different time periods within a WNv season to predict the total human WNv cases during a current year. Results of this study have produced information useful from mosquito control, public health, and scientific perspectives that can be incorporated into current WNv prevention strategies.

Library of Congress Subject Headings

West Nile virus -- South Dakota
Mosquitoes as carriers of disease -- South Dakota

Publisher

South Dakota State University

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Rights Statement

In Copyright