Date of Award

January 2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Jefferson A. Vaughan

Abstract

Tick surveillance in eastern North Dakota has revealed the presence of established I. scapularis populations in fragmented forest habitats previously regarded as unsuitable for this species. Understanding I. scapularis phenology, the reservoir competency of local vertebrate hosts, and population structure of blacklegged ticks in this region is essential to determining potential human risk of Lyme disease. Tick surveys were conducted throughout North Dakota by flagging and small mammal trapping. 1,701 ticks were collected, including 297 I. scapularis exhibiting a relatively low Borrelia burgdorferi infection rate (ca. 3-5%). Seasonal abundance varied greatly among life stages, with adult I. scapularis being most common in the early summer months (May-June) and juvenile I. scapularis abundance increasing later (July-August). Nearly half of all small mammals captured were red-backed voles (Myodes gapperi), and were parasitized by immature blacklegged ticks. To determine whether voles served as reservoirs for Lyme disease F-1 voles were injected with B. burgdorferi s.s. and at 2 and 4 weeks, the voles were infested with larval deer ticks. Engorged ticks were allowed to molt to nymphs and the nymphs were re-fed on naïve laboratory mice to determine if the larval ticks got infected and, as nymphs, were able to transmit the borrelia. Analyses of the mitochondrial DNA of deer ticks collected from North Dakota revealed a high haplotype diversity (Hd=0.80), and genetic structure suggests colonization from multiple sources. Populations fit theoretical models of population expansion using multiple test statistics, indicating potential increase in human tick exposure and Lyme disease incidence.

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