Term of Award

Spring 2001

Degree Name

Master of Science

Document Type and Release Option

Thesis (restricted to Georgia Southern)

Department

Department of Biology

Committee Chair

Quentin Q. Fang

Committee Member 1

Lance A. Durden

Committee Member 2

William S. Irby

Committee Member 3

Oscar J. Pung

Committee Member 4

John Averett

Abstract

Wolbachia spp. are intracellular endosymbionts that have been reported from many arthropods and nematodes. However, there is little known of Wolbachia from either ticks or fleas. This is the first report of Wolbachia within the lone star tick, Amblyomma americanum. Samples from the coastal region of Georgia were collected and screened individually for infection with Wolbachia utilizing nested polymerase chain reaction (PCR) amplification targeting a fragment of the 16S rRNA gene. The average prevalence of Wolbachia within the sampled A. americanum was 11%. This indicates the presence of Wolbachia within the ticks; however, wsp and ftsZ primers, which were used in the literature for determination of known strains of Wolbachia, failed to amplify our 16S positive samples. Phylogenetic analysis was run on the 16S sequences obtained, indicating that the amplified organisms do indeed belong in the genus Wolbachia. Phylogenetic analyses showed that this Wolbachia is different from previously reported tick endosymbionts. In addition to the initial survey, one mainland location was selected to test the temporal spread of Wolbachia within the tick population. The infection rate ofticks in this location is compared between the years (1998 and 2000). This comparison showed that the infection rate of Wolbachia significantly decreased over two years within A. americanum at this location. This data is contrary to many previous reports that Wolbachia quickly spread within populations of other arthropods.

This is also the first extensive report of Wolbachia within the order Siphonaptera (fleas). Wolbachia were found within natural populations of three different families of fleas. The fleas in which Wolbachia have been found occurred in five different species with varying prevalence: 21% (126 of 604) in Ctenocephalides felis; 7% (2 of 28) in Ctenocephalides canus; 25% (2 of 8) in Polygenus gwynni; 80% 12 of 15) in Orcopeas howardi, 94% 240 of 255) in Pulex simulans; and 24% 24 of 101) in Echidnophaga gallinacea. Wolbachia were detected by PCR amplification utilizing a new 16S rDNA specific primer designed in our lab. Confirmation of Wolbachia infection utilizing wsp and ftsZ primers was inconclusive depending upon flea host species. However, phylogenetic analysis of the 16S gene indicated that the fleas were infected with Wolbachia.

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