Tracking and Jumping: A Cophylogenetic Analysis of Host Switching in the Lyssaviruses Público
Rogawski, Elizabeth Tacket (2010)
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
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