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Tracking and Jumping: A Cophylogenetic Analysis of Host Switching in the Lyssaviruses

Rogawski, Elizabeth Tacket (2010)
Honors Thesis (70 pages)
Committee Chair / Thesis Adviser: Real, Leslie
Committee Members: De Roode, Jacobus ; Waller, Lance
Research Fields: Biology, General; Biology, Bioinformatics; Biology, Ecology
Keywords: lyssavirus; host switching; cophylogeny; geographic overlap; genetic distance
Program: College Honors Program, Biology
Permanent url: http://pid.emory.edu/ark:/25593/7qxrh

Abstract

Host switching, in which an infection by a pathogen in a novel host results in sustained transmission, is an infrequent phenomenon yet is responsible for viral zoonoses that have caused many emerging infectious diseases in humans. RNA viruses of the Lyssavirus genus, including the Rabies virus, are found in bat host reservoirs, and the frequency and risk factors for host switching among these associations have not yet been characterized. Since the lyssaviruses diverged after their hosts speciated, a history of cospeciation can be rejected, and instead this study distinguishes between host tracking, in which host and pathogen divergences are tied to each other, and host jumping, which describes switches that are not constrained by host phylogeny. The study aims to identify host jumps in lyssavirus history and to characterize the influence of genetic and geographic distance between hosts as determinants of successful host jumping. Lyssavirus and bat host phylogenies were generated in BEAST v1.5.2, and host jumps were identified in TreeMap v2.02β. Genetic distances between hosts and overlap of geographic bat ranges for identified host jumps were then compared to the same distances for random pairings of hosts. Eight host jumps were identified to explain the current host-virus associations. Genetic similarity between donor and recipient hosts does not appear to constrain successful host jumping. Host jumps occurred between both closely related and more distantly related hosts, and the genetic distances between hosts of identified jumps were not significantly smaller than those for random pairings of hosts. Conversely, host jumps were more common between hosts with greater overlapping ranges, and hosts involved in jumps generally shared similar foraging and roosting habitats. While genetic similarity may also have an impact, these results suggest that geographic proximity to new hosts and the number and intensity of contacts between bat species are the driving factors in host jumping events.

Table of Contents

Introduction -- Emerging Zoonotic Diseases -- Host Switching -- Cophylogenetics and Cospeciation -- Computational Methods -- Lyssaviruses -- Bat Hosts -- Objectives -- Hypotheses -- Aim 1: Reconstruction Analysis -- Aim 2: Genetic Distance Analysis -- Aim 3: Geographic distance Analysis -- Methods -- Results -- Phylogenetic Analysis -- Reconstruction Analysis -- Genetic Distance Analysis -- Geographic Distance Analysis -- Discussion -- Future Directions -- Conclusion -- Appendix A -- Appendix B -- References

Files

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