Term of Award

Summer 2003

Degree Name

Master of Science

Document Type and Release Option

Thesis (restricted to Georgia Southern)

Department

Department of Biology

Committee Chair

Quentin Fang

Committee Member 1

James E. Keirans

Committee Member 2

Lance A. Durden

Committee Member 3

Stephen P. Vives

Abstract

Lyme disease has become one of the most common infectious diseases that threaten public health in the U.S. The etiologic agent of Lyme disease is maintained in wildlife and transmitted to humans by bites from infected ticks. Ticks transmit numerous disease-causing agents to humans and mammals; however, the pathogen of Lyme disease is only transmitted by a group of ticks defined taxonomically within the Ixodes ricinus species complex. In the eastern U.S., Ixodes scapularis is responsible for transmission, while on the west coast, I. pacificus is the vector. In Europe, the Lyme disease agent is transmitted mainly by /. ricinus and in Asia /. persulcatus is the main vector. The aim of this study was to investigate phylogenetic relationships among species of the Ixodes ricinus complex worldwide using nucleotide sequences from mitochondrial cytochrome oxidase subunit I (mtDNA COI), and mitochondrial (mt) 16S genes. Ten species from the complex were analyzed; a 504bp fragment was amplified from the mt 16s gene and a 1080pb fragment from mtDNA COI gene. The inferred phylogeny showed that members of the Ixodes rininus complex are closely related but they do not have a monophyletic origin. Likewise, I concluded that species within the same geographic region (e.g. Palearctic/Oriental, Nearctic, Neotropical) are not sister taxa with each other. This might indicate that the ability to transmit the Lyme disease agent diverged on the different continents independently.

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