Year of Graduation

2020

Document Type

Thesis

Major

Biology

Directing Professor

Elizabeth Gleim

Abstract

Ixodes scapularis, or the blacklegged tick, is the primary vector of Borrelia burgdorferi. This pathogen is the causative agent of Lyme disease, the most common vector-transmitted disease in the United States. Although I. scapularis is distributed throughout the eastern U.S., Lyme disease is only considered endemic in the northeastern region of the country. Prior to 2007, Lyme disease was uncommon in Virginia, but since then cases of Lyme disease have increased dramatically with a hotspot forming in the Roanoke-Blacksburg area. The purpose of the current study was to determine whether B. burgdorferi prevalence and the genetic structure of I. scapularis populations in Southwest Virginia are unique from other regions of the state. By testing for Borrelia spp., we also determined whether B. miyamotoi, a newly-emerging pathogen, is present in the region. A phylogenetic analysis using the 16S mitochondrial rRNA gene was completed with I. scapularis nymphs and adults (n=48) from four sites in southwestern Virginia. Borrelia spp. testing of I. scapularis nymphs (n=291) was also done via nested polymerase chain reaction (PCR). Genetic analysis demonstrated that all I. scapularis fell within the American clade, primarily associated with northern populations of I. scapularis, and yielded 16 different haplotypes, 9 of which were unique within this analysis. These findings suggest expansion of American clade ticks from the northeastern United States into Virginia. Meanwhile, there was an overall B. burgdorferi prevalence of 4.5%, which is lower than what has been previously reported in Lyme endemic areas. Interestingly, one nymph tested positive for B. miyamotoi, which is the first published report of B. miyamotoi in I. scapularis in southwestern Virginia. Overall, this study provided evidence indicating that the southern front of Lyme disease is expanding, and gave valuable insights into Lyme disease ecology in an emerging hotspot in southwestern Virginia.

Download

Share

COinS