Variation in tick host preference and its epidemiological impact
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Tick-borne pathogens pose a significant health risk to humans and wildlife. The complex interactions between ticks and their hosts make management of tick-borne pathogens particularly challenging. Many of the most common species of ticks feed on a wide variety of hosts, but transmit pathogens that are only capable of infecting a narrow range of susceptible host species. Prior research has focused on understanding which tick hosts are capable of serving as pathogen reservoir hosts by carrying and transmitting tick- borne pathogens. However, relatively little attention has been given to studying how ticks choose their hosts. Host choice is of particular importance to the epidemiology of tick- borne pathogens when not all hosts are pathogen reservoirs. My dissertation research investigates the nature of host choice and its impact on disease prevalence in two tick species with similar life histories and host ranges: the lone star tick (Amblyomma americanum) and the American dog tick (Dermacentor variabilis). I conducted an experiment to demonstrate that lone star ticks can respond to host scent. Certain host scents, including those from some individual opossums and raccoons, are attractive to ticks. Proximity to scent also influences tick movement. I also looked for evidence that American dog tick populations are genetically structured by host species identity, and found that certain tick genotypes correlate with host species. This suggests that these ticks may have heritable host preferences that influence their feeding behaviors. Finally, I used a mathematical model to predict disease transmission probability and lone star tick preference for reservoir hosts. I considered hypothetical wildlife communities with different reservoir host relative abundances, and found that changes in relative abundance influence both disease transmission probability and tick host preference estimates. The model also suggests that lone star ticks must parasitize reservoir hosts more frequently when those hosts are less common. These results highlight the importance of host choice and host community composition as determinants of tick-borne disease prevalence.