Little is known about the tick populations found within the central Appalachian/southwestern region of Virginia. The main focus of this research was to better assess local tick communities in the central Appalachian-Southwestern region of Virginia, which was addressed by determining species diversity, habitat associations, seasonal phenology, pathogen prevalence, and ecological factors that influences tick presence and abundance. A field study was conducted from June 2019 - November 2020 across 8 counties and 3 habitat types. Forested habitats exhibited greater tick species diversity than pasture and urban habitats. Each tick species was observed to be associated with particular habitats. The presence of B. burgdorferi sensu stricto (causative agent of Lyme disease), the human variant of A. phagocytophilum (causative agent of human granulocytic anaplasmosis), and Powassan virus (the causative agent of Powassan encephalitis) were detected in collected field specimens, suggesting a significant threat to public health. The detection of Powassan virus RNA in local Ixodes scapularis ticks is the first evidence of this viral pathogen within the region.
The overwintering abilities of ticks, whose populations are expanding or becoming more invasive, including Haemaphysalis longicornis, Amblyomma americanum, and Amblyomma maculatum, were examined through a combination of laboratory and field experiments. Amblyomma americanum and H. longicornis nymphal ticks had a lower supercooling temperature than adult ticks, suggesting their potential to overwinter better; A. maculatum nymphs had similar average supercooling temperatures as the other two species at nymphal stage. Via a field experiment, A. americanum, H. longicornis, and A. maculatum were subjected to natural elements of a Virginian winter in a two-factor design investigating elevation and potential insulation coverage. Elevation and insulation coverage were found to have no significant impact on the overwintering survival of H. longicornis and A. americanum. However, the life-stage of the tick was determined to be a significant factor that dictated the survival of ticks of these species. Overwintering survival of Amblyomma maculatum nymphs was influenced by insulation (proxied by leaf litter); which may be attributed to this tick's preference of drier climate. Low overwintering survival suggests that a tick may not be able to establish a permanent population within the area. / Master of Science in Life Sciences / Ticks can transmit many pathogens, bacteria or viruses that cause disease, to both humans and animals. Diseases associated with ticks can include Lyme disease, Human Anaplasmosis, Ehrlichiosis, Rocky Mountain spotted fever, as well as viral illnesses. The pathogens that cause these diseases are vectored by specific tick species. Currently, there are no published reports of tick species present within the central Appalachian/southwestern region of Virginia. A study to determine local tick populations presence and the factors influencing their maintenance in the environment was conducted. Additionally, field collected specimens were screened to assess pathogen prevalence within the region. I confirm the presence of Borrelia burgdorferi sensu stricto (causative agent for Lyme disease), Anaplasma phagocytophilum (causative agent for Human Granulocytic Anaplasmosis), and Powassan virus within Ixodes scapularis, commonly referred to as black-legged ticks. Habitat (forest, urban, pasture) was a significant influencing factor on the presence of I. scapularis, Amblyomma americanum, and Haemaphysalis longicornis (e.g., the latter species was predominantly found in pasture habitats).
Secondly, I investigated how well three sympatric tick species would overwinter within the region. Survival of a tick is heavily dependent upon their ability to withstand desiccation, obtain a blood meal from a host, mate, and reproduce. Certain ticks may be limited to certain regions based on elevation, temperature, and relative humidity. I investigated the influence of elevation and insulation coverage (presence of leaves vs. no leaves) on A. americanum (Lone star tick), H. longicornis (Asian longhorned tick), and A. maculatum (Gulf Coast tick). Elevation and insulation coverage had no significant impact on the overwintering survival of the Lone star and Asian longhorned ticks. Tick survival was mainly dictated by what life-stage they were in; Lone star ticks survived better as adult than at other life stages. Asian longhorned ticks survived better as nymphs than larva and adults. Insulation coverage influenced the overwintering survival of the Gulf Coast tick. These ticks survived better with no leaves, which may be associated with their preference of drier climates.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/104074 |
| Date | 29 June 2021 |
| Creators | Whitlow, Amanda Marie |
| Contributors | Entomology, Eastwood, Gillian, Auguste, Albert J., Schuerch, Roger, Paulson, Sally L. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Coverage | Virginia |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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