Natural Rickettsia infection rate in Amblyomma americanum and Dermacentor variabilis in Georgia, United States. Restricted; Files Only

Abstract

Purpose: Rickettsia prevalence in Georgia, United States is poorly understood. Amblyomma americanum ticks have the potential to be a vector for human illness due to Rickettsia spp. pathogens, and understanding the infection rate compared to Dermacentor variabilis, the vector associated with Rocky Mountain Spotted Fever transmission, is important in determining the risk of pathogen transmission to humans in Georgia.

 

Methods: Host-seeking ticks were collected using flagging methods, then pooled and DNA was extracted. Two molecular methods of detection were used, a real-time PCR and a conventional PCR both designed to test for the Rickettsia genus. 64 pools of ticks were tested using both methods, and sanger sequenced to determine the Rickettsia species found in positive ticks.

 

Results: One hundred percent of the 32 pools of A. americanum ticks tested positive for Rickettsia genus bacteria. Sequencing results from these ticks were one hundred percent Rickettsia amblyommatis. 9.38 % (three pools) of D. variabilis ticks were positive for rickettsia. Two pools was sequenced as R. amblyommatis and the other as R. montanensis. No samples were positive for R. rickettsii. The sensitivity of both tests (100%) were the same, however the specificity of the real-time PCR was 72.4% compared to the 100% of the conventional PCR.

 

Conclusions: A. americanum may be an important vector of Spotted Fever Group Rickettsiae infection in humans. The conventional PCR was a better method for detecting Rickettsia spp. in ticks, due to the occasional false positives in the real-time PCR test.

 

 

 

Table of Contents

Introduction 1

  Introduction and Rationale 1

Hypothesis 3

Significance 4

Literature Review 6

Background 6

 Previous Findings 8

 Tick Surveillance 11

Methods 13

Introduction 13

Procedures 14

 Plans for Data Analysis 19

 Ethical Considerations 20

Limitations 20

Results 21

 Overview of Results 21

Findings 21

Discussion 26

Discussion 26

 Limitations and Suggestions 28

Conclusion 29

References 30

Appendix 38

       

About this Master's Thesis

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School	Rollins School of Public Health
Department	Hubert Department of Global Health
Degree	M.P.H.
Submission	Master's Thesis
Language	English
Research Field	Biology, Microbiology Environmental Sciences Health Sciences, Public Health
Keyword	Dermacentor PCR Rickettsia Lone Star Ticks
Committee Chair / Thesis Advisor	Gonzalo Vazquez-Prokopec, Emory University

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