Dissertation
UNDERSTANDING THE INTER-EPIZOOTIC CYCLE OF PLAGUE: THE ROLE OF AMOEBA AS AN ENVIRONMENTAL RESERVOIR FOR YERSINIA PESTIS
Doctor of Philosophy (PhD), Washington State University
01/2017
Handle:
https://hdl.handle.net/2376/111111
Abstract
Plague is a flea-borne rodent-associated zoonotic disease caused by Yersinia pestis. The disease composes sylvatic cycles defined by epizootics with high rodent mortalities, punctuated by inter-epizootic periods when the bacterium quiescently persists in an unknown reservoir. My research focusses on understanding if free-living amoeba (FLA) can serve as an alternate reservoir host that supports the quiescent life stage of Y. pestis and its subsequent recrudescence to activate plague epizootics.
In Chapter One as a proof of principle we investigated the interaction between Y. pestis and a laboratory strain of the ubiquitous soil FLA, Acanthamoeba castellanii. We demonstrated that during co-culture with amoeba, representative Y. pestis strains of epidemic biovars are phagocytized and able to survive within amoeba vacuoles for at least five days. There are two key mechanisms that facilitate the ability of Y. pestis to survive within amoeba. One is the PhoP global stress response transcriptional regulator protein which we demonstrate is essential for survival in amoeba. The other is that Y. pestis subverts intracellular digestion by residing in spacious vacuoles that remain separated from the lysosomal compartment. This evidence for prolonged survival and subversion of intracellular digestion of Y. pestis within a FLA suggest that protozoa may serve as a protective soil reservoir for Y. pestis.
In Chapter Two, bacterivorous FLA isolated from prairie dog burrows located at an established plague foci in Colorado USA were tested for the ability to support prolonged survival of Y. pestis. Here FLA were isolated from burrow soils and one isolate was cultured and taxonomically characterized as a novel Acanthamoeba castellanii isolate of the T4 genotype. This new FLA isolate was demonstrated to support Y. pestis survival within distinct vacuoles for up to a maximal testing period of four days.
My research sheds new light on how plague may persist during inter-epizootic periods and then re-emerge to cause epizootics. The possibility that amoeba harbor Y. pestis in the environment should likely be considered in conceptualization of improved approaches to understand risk and re-emergence of the plague.
Metrics
26 File views/ downloads
57 Record Views
Details
- Title
- UNDERSTANDING THE INTER-EPIZOOTIC CYCLE OF PLAGUE: THE ROLE OF AMOEBA AS AN ENVIRONMENTAL RESERVOIR FOR YERSINIA PESTIS
- Creators
- Javier Antonio Benavides-Montaño
- Contributors
- Viveka Vadyvaloo (Advisor)Leigh Knodler (Committee Member)Jean Celli (Committee Member)Douglas R Call (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- College of Veterinary Medicine
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 87
- Identifiers
- 99900581718501842
- Language
- English
- Resource Type
- Dissertation