Title page for ETD etd-11132006-190148

Type of Document Dissertation
Author Gruszynski, Karen Ruth
Author's Email Address karengdvm@msn.com
URN etd-11132006-190148
Title The Epidemiology of West Nile Virus in Louisiana
Degree Doctor of Philosophy (Ph.D.)
Department Pathobiological Sciences (Veterinary Medical Sciences)
Advisory Committee
Advisor Name Title
John B Malone Committee Chair
Alma Roy Committee Member
Lane Foil Committee Member
Mark A Mitchell Committee Member
Ray Ferrell Dean's Representative
  • reptile
  • prnt
  • serosurvey
  • arbovirus
  • model
  • geographic information systems
  • bird
Date of Defense 2006-05-11
Availability unrestricted
West Nile virus (WNV), a member of the genus Flavivirus transmitted by mosquitoes, first appeared in the New York in 1999. Within five years WNV was detected throughout the contiguous 48 states causing disease in reservoirs and accidental hosts alike. In Louisiana, WNV was first detected in 2001 with one human case, ten equine cases, and six dead birds reported. The introduction of WNV into Louisiana presented an unique opportunity to observe an emerging disease unfold, so a study was launched to gain insight into the epidemiology of WNV in Louisiana.

The first component, an environmental predictive model for West Nile virus, was developed using geographic information systems and remote sensing in relationship to the prevalence of human cases and the percent of WNV positive dead birds by parish for 2002 and 2003. Linear regression analysis showed a 13 variable model with environmental and human factors for the 2003 human dataset to be the best model. This model was able to explain 74% of the variation in human WNV prevalence by parish. The results of the model along with one-way chi-square analysis of categorical variables indicated largely urban cycle when the mosquito-bird transmission cycle reaches high levels as the main mode of WNV transmission with spillover to humans, and other accidental hosts.

A serosurvey of wild birds in East Baton Rouge Parish was conducted from November 2002 to October 2004. A total of 1287 samples were tested by the plaque reduction neutralization test. Overall, 222/1287 (17.25%; CI: 15.19-19.31) tested positive. Species, location, sex, age, and monthly differences were detected. The study identified Northern cardinals (Cardinalis cardninalis) as a statistically significant host for WNV in Louisiana.

Mediterranean house geckos (Hemidactylus turcicus) were assessed as a potential reservoir for West Nile virus. Geckos were inoculated orally with West Nile virus and a field study was conducted to determine the prevalence of WNV in naturally infected geckos. Results obtained through virus culture and RT-PCR indicated that geckos could become infected with an oral inoculation of WNV, but that naturally infected geckos do not produce high enough viremias to act as a reservoir.

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