Species-specific drivers of West Nile virus transmission in urban environments Open Access

Abstract

Heterogeneity, specifically biological variation, is an inherent component of pathogen transmission systems. Transmission variability arises due to differences in an individual’s ability to acquire and transmit a pathogen (i.e. pathogen competence) and the probability infected individuals encounters susceptible individuals. For vector-borne pathogens, competence varies among host and vector species, and the composition of host and vector communities strongly influences the rate at which pathogens are transmitted among individuals. Because species community composition varies across the spatiotemporal landscape, species-specific drivers of transmission can vary from region to region.

The objective of my dissertation is to quantify vector and host species-level transmission heterogeneities and then link these dynamics across species using West Nile virus (WNv) as a model system. West Nile virus is a mosquito-borne, zoonotic pathogen that is transmitted by mosquito vectors in the Culex genus among birds. I specifically use a combination of experimental, field surveillance, and modeling approaches to quantify connections in WNv transmission by two Culex spp., Culex restuans and Culex quinquefasciatus, and the diverse bird species communities upon which these two vectors feed. In Chapter 1, I use field surveillance of WNv in Atlanta, GA coupled with modeling techniques to show that climate and the availability of susceptible hosts mediate the likelihood that Cx. restuans and Cx. quinquefasciatus are efficient vectors of WNv. In Chapter 2, I use long term sero-surveys of wild birds in Chicago, IL and Atlanta, GA to quantify the variability of WNv incidence across sampled species. In Chapter 3, I extend results from Chapter 2 and use blood feeding experiments to show that the feeding behaviors of Cx. quinquefasciatus are a function of the availability of certain host species. Finally, in Chapter 4 I use an applied approach to show that targeted larvicide applications in road-side catch basins are insufficient to control WNv at local scales. All though each chapter addresses an important component of heterogeneity in the WNv transmission system, further research is needed to determine the extent to which the intensity of WNv transmission in the enzootic cycle translates to the risk of human WNv-incidence.

Table of Contents

Introduction                                                                                                                1-7

            References                                                                                                      8-15

Chapter 1                                                                                                                    16-51               Introduction                                                                                                    16-18

            Materials and Methods                                                                                   19-24

            Results                                                                                                            24-27

            Discussion                                                                                                       28-31

            References                                                                                                      32-36

            Tables and Figures                                                                                          37-43  

                        Table 1                                                                                                37

                        Table 2                                                                                                38

                        Table 3                                                                                                39

                        Figure Legends                                                                                   40

                                    Figure 1                                                                                   41

                                    Figure 2                                                                                   42

                                    Figure 3                                                                                   43

            Supplemental Materials                                                                                  44-51

                        S. Table 1                                                                                            44

                        S. Table 2                                                                                            45

                        S. Table 3                                                                                            46

                        S. Figure Legends                                                                               47

                                    S. Figure 1                                                                              48

                                    S. Figure 2                                                                              49

                                    S. Figure 3                                                                              50

                                    S. Figure 4                                                                              51

Chapter 2                                                                                                                    52-102

            Introduction                                                                                                    52-54   Materials and Methods                                                                                   54-58

            Results                                                                                                            58-61

            Discussion                                                                                                       61-66

            References                                                                                                      67-74  

Tables and Figures                                                                                          75-84

                        Table 1                                                                                                75

                        Table 2                                                                                                76

                        Figure Legends                                                                                   77-78

                                    Figure 1                                                                                   79

                                    Figure 2                                                                                   80

                                    Figure 3                                                                                   81

                                    Figure 4                                                                                   82

                                    Figure 5                                                                                   83

                                    Figure 6                                                                                   84

            Supplemental Materials                                                                                  85-102

                        S. List 1                                                                                               85-87

                        S. Table 1                                                                                            88

                        S. Table 2                                                                                            89

                        S. Table 3                                                                                            90

                        S. Table 4                                                                                            91

                        S. Figure Legends                                                                               92-93

                                    S. Figure 1                                                                              94

                                    S. Figure 2                                                                              95

                                    S. Figure 3                                                                              96

                                    S. Figure 4                                                                              97

                                    S. Figure 5                                                                              98

                                    S. Figure 6                                                                              99

                                    S. Figure 7                                                                              100

                                    S. Figure 8                                                                              101

                                    S. Figure 9                                                                              102

Chapter 3                                                                                                                    103-127          

            Introduction                                                                                                    103-105

            Materials and Methods                                                                                   105-110

            Results                                                                                                            111-112

            Discussion                                                                                                       112-115

            References                                                                                                      116-120

            Tables and Figures                                                                                          121-127

                        Table 1                                                                                                121     

                        Figure Legends                                                                                   122-123

                                    Figure 1                                                                                   124

                                    Figure 2                                                                                   125

                                    Figure 3                                                                                   126

                                    Figure 4                                                                                   127

Chapter 4                                                                                                                    128-152          

            Introduction                                                                                                    128-129

            Materials and Methods                                                                                   130-134

            Results                                                                                                            134-136

            Discussion                                                                                                       136-139

            References                                                                                                      140-144

Tables and Figures                                                                                          145-152

                        Table 1                                                                                                145

                        Table 2                                                                                                146

                        Table 3                                                                                                147

                        Table 4                                                                                                148

            Figure Legends                                                                                               149

                        Figure 1                                                                                               150

                        Figure 2                                                                                               151

                        Figure 3                                                                                               152     

Conclusions                                                                                                                153-157

References                                                                                                      158-160          

About this Dissertation

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• Permission granted by the author to include this thesis or dissertation in this repository. All rights reserved by the author. Please contact the author for information regarding the reproduction and use of this thesis or dissertation.

School	Laney Graduate School
Department	Biological and Biomedical Sciences
Subfield / Discipline	Population Biology, Ecology & Evolution
Degree	Ph.D.
Submission	Dissertation
Language	English
Research Field	Health Sciences, Public Health Biology, Entomology Biology, Ecology
Keyword	northern cardinal heterogeniety Culex quinquefasciatus vectorial capacity urban ecology
Committee Chair / Thesis Advisor	Vazquez Prokopec, Gonzalo, Emory University
Committee Members	Mead, Daniel, University of Georgia Kitron, Uriel, Emory University Morran, Levi, Emory University Waller, Lance, Emory University

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