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Dissertation Low Temperature Effects On DISSERTATION LOW TEMPERATURE EFFECTS ON THE TRANSCRIPTOME OF YERSINIA PESTIS AND ITS TRANSMISSIBILITY BY OROPSYLLA MONTANA FLEAS Submitted by Shanna K. Williams Department of Microbiology, Immunology & Pathology In partial fulfillment of the requirements For the Degree of Doctor of Philosophy Colorado State University Fort Collins, Colorado Spring 2016 Doctoral Committee: Advisor: Brad Borlee Co-Advisor: Scott Bearden Ken Gage Mark Stenglein Shawn Archibeque Copyright by Shanna K. Williams All Rights Reserved ABSTRACT LOW TEMPERATURE EFFECTS ON THE TRANSCRIPTOME OF YERSINIA PESTIS AND ITS TRANSMISSIBILITY BY OROPSYLLA MONTANA FLEAS Yersinia pestis, the causative agent of plague, is primarily a rodent-associated, flea-borne zoonosis. Transmission to humans is mediated most commonly by the flea vector, Oropsylla montana, and occurs predominantly in the Southwestern United States. In these studies, we hypothesized that Y. pestis-infected O. montana fleas held at temperatures as low as 6ºC could serve as reservoirs of the plague bacillus during the winter months in temperate regions with endemic plague foci. With few exceptions, previous studies showed O. montana to be an inefficient vector at transmitting Y. pestis at 22-23C particularly when such fleas were fed on susceptible hosts more than a few days after ingesting an infectious blood meal. We examined whether holding fleas at sub-ambient temperatures (for purposes of these studies, ambient temperature is defined as 23C) affected the transmissibility of Y. pestis by this vector. Colony- reared O. montana fleas were given an infectious blood meal containing a virulent Y. pestis strain (CO96-3188), and potentially infected fleas were maintained at different temperatures (6ºC, 10C, 15C, or 23ºC). Transmission efficiencies were tested by allowing groups of ~15 infectious fleas to feed on each of seven naïve CD-1 mice on days 1-4, 7, 10, 14, 17, and 21, 28, 35, and 42 post infection (p.i.). Fleas held at 6ºC, 10C and 15C were able to effectively transmit at every time point p.i. The percentage of transmission to naïve mice by fleas maintained at low temperatures was higher than for fleas maintained at 23ºC and indicates that ii O. montana fleas efficiently transmit Y. pestis at low temperatures. Moreover, bacterial loads of flea cohorts maintained at temperatures of 6ºC, 10ºC and 15ºC were statistically higher than fleas maintained at 23ºC. In addition, whole transcriptomes of Y. pestis bacteria grown at 6ºC, 10C, 15C and 23ºC were analyzed to assess differential gene expression at each temperature to identify genes which may contribute to an increase in virulence or survivability of the plague pathogen at the lower temperatures when compared to ambient temperature. This is the first comprehensive study to demonstrate efficient transmission of Y. pestis by O. montana fleas maintained at temperatures as low as 6ºC. Our findings further contribute to the understanding of plague ecology in temperate climates by providing support for the hypothesis that Y. pestis is able to overwinter within the flea gut and potentially cause infection during the following transmission season. The findings also might hold implications for explaining the focality of plague in tropical regions where plague occurs in cooler environments, primarily located at higher elevations. iii ACKNOWLEDGEMENTS Foremost, I would like to express my sincere gratitude to Dr. Ken Gage and Dr. Scott Bearden for allowing me the opportunity to work in your lab while pursuing my doctorate. In addition to Dr. Gage and Dr. Bearden, I also would like to thank everyone on my committee: Dr. Brad Borlee, Dr. Mark Stenglein, and Dr. Shawn Archibeque for their encouragement, insightful comments, and guidance. My sincere thanks also goes to John Montenieri, who has been an essential part of my research studies, and always provided comic relief and constant support. I also want to thank my fellow lab mates and colleagues Sarah Maes, Tammi Johnson, Karen Boegler and Christine Graham for their assistance, discussions, and for all of the fun over the last few years. Finally, I would like to thank my family and all of my friends for the constant support and encouragement. Without each and every one of the aforementioned, it would never have been possible for me to undergo such a very difficult, but highly rewarding time in my life. I greatly appreciate everything you all have done for me. Thank you all very much. iv TABLE OF CONTENTS ABSTRACT ...................................................................................................................................ii ACKNOWLEDGEMENTS............................................................................................................iv LIST OF TABLES.........................................................................................................................vii LIST OF FIGURES .....................................................................................................................viii 1. CHAPTER 1- Literature Review-Yersinia pestis Transmission and Disease.............................................................................................................................................1 2. CHAPTER 1.1-Histoical Background and Yersinia pestis pandemics..........................…..1 3. CHAPTER 1.2-Y. pestis General Characteristics and Etiology….......................................6 4. CHAPTER 1.3- Plague as a Bioterrorism Agent.................................................................9 5. CHAPTER 1.4-Y. pestis Evolution from Y. pseudotuberculosis.......................................11 6. CHAPTER 1.5- Y. pestis Life Cycle..................................................................................14 7. CHAPTER 1.6- Y. pestis Reservoirs..................................................................................17 8. CHAPTER 1.6.1- Mammalian Hosts.................................................................................17 9. CHAPTER 1.6.2- Other Potential Reservoirs....................................................................19 10. CHAPTER 1.7- Y. pestis and fleas....................................................................................19 11. CHAPTER 1.8- Oropsylla montana..................................................................................24 12. CHAPTER 1.9- Flea (Insect) Immunity............................................................................25 13. CHAPTER 1.10- Y. pestis Transmission Mechanisms......................................................28 14. CHAPTER 1.11- Y. pestis Transmission Factors..............................................................30 15. CHAPTER 1.12- Y. pestis Virulence and Pathogenesis....................................................32 16. CHAPTER 1.13- Y. pestis Geographic Distribution and Incidence..................................37 17. CHAPTER 1.14- Y. pestis Clinical Disease Features........................................................41 18. CHAPTER 1.15- Y. pestis Diagnosis and Treatment........................................................43 19. CHAPTER 1.16- Y. pestis Surveillance and Control.........................................................49 20. CHAPTER 1.16.1- Plague Surveillance. ..........................................................................50 21. CHAPTER 1.16.2- Plague Control....................................................................................51 22. CHAPTER 1.17- Animal Models Used in Plague Research.............................................55 23. CHAPTER 1.17.1- Invertebrate Models for Studying Plague Transmission Factors…...55 24. CHAPTER 1.17.2- Mammalian Models to Study Plague Virulence and Pathogenesis....58 25. CHAPTER1.17.2A- Mouse Model....................................................................................58 26. CHAPTER 1.17.2B- Guinea Pig Model............................................................................61 27. CHAPTER 1.17.2C- Rat Model........................................................................................62 28. CHAPTER 1.17.3- Non-Human Primate (NHPs) Model..................................................64 29. CHAPTER 1.17.3A- Rhesus Macaques Model.....................…………...……….............64 30. CHAPTER 1.17.3B- African Green Monkey Model.........................................................65 31. CHAPTER 1.17.3C- Cynomolgus Macaques Model…….................................................66 32. CHAPTER 1.18- Detection Assays Used for Y. pestis Identification in Animals and Fleas………….……………………………………………………….67 33. CHAPTER 1.18.1- Rodents and Other Animal Populations.............................................67 34. CHAPTER 1.18.2- Detection of Y. pestis in Fleas............................................................68 35. CHAPTER 1.19- Next Generation Sequencing (NGS) for Transcriptomics Analysis.....69 36. CHAPTER 1 References.........................................................................................................72 v 37. CHAPTER 2- Effects of Low Temperature Flea Maintenance on the Transmissibility of Yersinia pestis by Oropsylla montana.........................................................................................121 38. CHAPTER 2.1- Introduction...........................................................................................122 39. CHAPTER 2.2- Materials and Methods..........................................................................126 40. CHAPTER 2.3- Results...................................................................................................131
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