"Tick"-et to Success: Unraveling the Ecology of Host-Tick Interactions in Small Mammals

Restricted (Penn State Only)
- Author:
- Brown, Jessica
- Graduate Program:
- Ecology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- February 21, 2024
- Committee Members:
- Jason Kaye, Program Head/Chair
Isabella Cattadori, Major Field Member
Erika Machtinger, Chair & Dissertation Advisor
Carolyn Mahan, Outside Unit Member
Pierre Chuard, Special Member
Jacob Werner, Outside Field Member - Keywords:
- rodent
host
parasite
coevolution
disease
Ixodes scapularis
tick - Abstract:
- Mammals have been subjected to parasitism for millions of years, and parasites are dependent on their hosts for survival. Coevolution has driven the development of traits in hosts and parasites. The evolution of host-parasite relationships is highly nuanced, and model systems can increase our broader understanding of the ecological concepts that drive host-parasite interaction and evolution, especially as we face a changing world driven by anthropogenic and natural causes. Lyme disease, or Lyme borreliosis, is the most commonly diagnosed vector-borne disease in the United States. Rodents commonly serve as hosts for blacklegged ticks (Ixodes scapularis) and as competent reservoirs for Borrelia burgdorferi, the causative agent of Lyme disease. Not all hosts are equally capable of infecting naïve ticks, nor are all hosts studied equally. Despite being regularly parasitized by blacklegged ticks, other common mammalian hosts of blacklegged ticks are typically not the focus of tick ecology or control studies. Most studies focused on blacklegged ticks' hosts are focused solely on white-footed mice (Peromyscus leucopus) and/or white-tailed deer (Odocoileus virginianus). Two additional species of small mammals whose distributions commonly overlap with that of the white-footed mouse and blacklegged tick are the meadow vole (Microtus pennsylvanicus) and the southern red-backed vole (Clethrionomys gapperi). While they are hosts of juvenile life stages of blacklegged ticks and can be infected with B. burgdorferi, the body of literature focusing on tick associations with either host is minimal. Observing naturally occurring differences in tick burdens among the three aforementioned rodent host species led to inquiries regarding potential drivers of this phenomenon, including potential behavioral and immune-mediated defense mechanisms. Additionally, this work provides a unique opportunity to assess how sympatric hosts with varying historical relationships with blacklegged ticks respond to the presence of a parasite as its range continually expands through North America. This dissertation assessed the relationship between blacklegged ticks and individuals of all three rodent species from colonies established from wild-caught individuals studied in the field. The objective of this work was to address knowledge gaps in our understanding of how hosts respond to blacklegged tick attachment, specifically in how they use behavioral and immunological defenses to prevent parasitism. Ultimately, the defensive mechanisms used by each host in response to parasitism differed; white-footed mice exhibited no notable defensive mechanisms, meadow voles used behavioral defenses, and southern red-backed voles seemed to develop immunological resistance. As our climate continues to change, organisms are continually adapting. The takeaways from this work have the potential to be extrapolated to other systems and increase our ability to form predictions related to emerging or re-emerging pathogens.