Wildlife and Tick Responses to Forest Management: Prevalence of Tick-Borne Pathogens and Implications for One Health

摘要

In the United States human cases of tick-borne diseases have more than doubled over the past 15 years. This trend is expected to increase as medically important tick species and their host(s) expand in geographic range largely mediated by anthropogenic environmental disturbance, particularly land use change. The goal of this study was to evaluate the effects of land use change as it relates to forest management in the forms of prescribed fire and thinning on tick and small mammal communities, their associated microhabitat(s), and prevalence of tick-borne pathogens within a mixed hardwood/pine forest ecosystem. I also surveyed Sus scrofa for ticks and their associated pathogens to determine the role of a nonnative invasive wildlife host in influencing tick-borne disease risk within the study area evaluated. This project consisted of a control-impact, complete block design with a 2 x 3 factorial arrangement with three thinning levels applied (no thin, heavy thin, and light thin) and two burn applications (burn and no burn) resulting in six treatments with controls included (no thin and no burn) replicated three times resulting in a total of 18 research stands. From 1 June to 30 August, 2016–2019, I collected 50,736 ticks via drag sampling, 893 ticks from 54 hunter harvested Sus scrofa, and one tick from 269 live trapped small mammals at the William B. Bankhead National Forest, Alabama, US. Tick samples were comprised primarily of Amblyomma americanum, followed by Dermacentor variabilis, Amblyomma maculatum, Ixodes scapularis, and Rhipicephalus sanguineus. Using molecular methods, I identified presence of Rickettsia spp., Rickettsia amblyommatis, Rickettsia montanensis, Rickettsia parkeri, Candidatus Rickettsia andeanae, Ehrlichia chaffeensis, and Heartland Virus. I detected a significant interaction effect of burn with thin on A. americanum abundance with total adult counts decreasing in light thin with burn stands and total nymph counts decreasing in heavy thin with burn as well as light thin with burn stands. In addition, I found lower prevalence of Rickettsia spp. in ticks collected from light thin with burn stands as compared to ticks from heavy thin with burn and control stands. This study shows that prescribed burning in combination with thinning is not only an effective tool for managing A. americanum populations, but also potentially infection prevalence of Rickettsia spp. within mixed pine/hardwood forests in the southeastern US and therefore, has significant implications for human, animal, and forest health.