Discussion
The prevalence of B. burgdorferi ss, together with the presence of B. miyamotoi and A. phagocytophilum identified in adult and nymphal blacklegged ticks, highlights the increasing tickborne disease risk in southwestern North Carolina. The prevalence of B. burgdorferi ss identified in adult blacklegged ticks collected in Biltmore Forest is similar to the prevalence in the mid-Atlantic, upper Midwest, and Northeast, where it is endemic (5). Previously reported B. burgdorferi infection prevalences among Ix. scapularis collected from public lands in Buncombe County, where Biltmore Forest is located, range from 13% to 17% in nymphs to 25% in adults; because ticks were collected exclusively from residential areas in this study, the high infection prevalence identified in this report suggests higher potential for human disease than that identified in previous studies (6). However, surveys in neighboring South Carolina counties found low prevalence of infection with B. burgdorferi among Ix. scapularis, suggesting that the Biltmore Forest study area represents the leading edge of southward expansion of northern populations of Ix. scapularis (7). In addition, capture of host-seeking Ix. scapularis nymphs in this study indicates the presence of northern clade ticks in this southeast state (8).
These findings might represent the farthest south that human-associated variant A. phagocytophilum and B. miyamotoi have been identified in Ix. scapularis populations (9) and highlight the potential for pathogen transmission in a new geographic area. Given that both A. phagocytophilum and B. miyamotoi can cause severe clinical disease, efforts to raise awareness in this region are needed, both to help guide clinicians’ diagnostic decisions and to encourage self-protective measures such as use of insect repellent and protective clothing (e.g., long pants and tall socks).
Limitations
The findings in this report are subject to at least five limitations. First, specimen collection began shortly after Hurricane Helene, which resulted in ecological destruction in western North Carolina. Without comparable data from before the storm, it is unclear how this hurricane might have affected regional tick populations. Second, because tick collection occurred during 1–3 days each month, collections were subject to variable environmental and weather conditions that might have affected the presence or absence of host-seeking ticks on the day of collection. This timeframe limits the ability to characterize the temporal presence of ticks in the study area. Third, a relatively small area of the town was dragged for ticks, limiting the ability to determine tick densities. Fourth, because the survey achieved a relatively low response rate of 12.5%, the results carry a heightened risk for selection bias. Thus, the results of this survey reflect a small subset of the population of Biltmore Forest and might not be representative of the entire community. Finally, because the majority of human tickborne disease cases were identified through self-report, these data are subject to potential misclassification.
Implications for Public Health Practice
Given the high pathogen prevalence of B. burgdorferi ss in Ix. scapularis, as well as the identification of B. miyamotoi and A. phagocytophilum, increased clinical suspicion for human disease attributable to these pathogens among those who live in or visit this region is warranted. A public health alert for health care providers who have a high likelihood of encountering patients with exposure to tickborne disease (e.g. primary care, urgent care, and infectious disease practitioners), many of whom do not have experience with the diagnosis and management of Lyme and other tickborne diseases (10), could help disseminate this new information. Expansion of Ix. scapularis surveillance and associated pathogen testing in the broader southeastern United States is also warranted. Education for the public to prevent tick bites includes wearing appropriate protective clothing, using Environmental Protection Agency–registered insect repellents, and checking the body for ticks after spending time outdoors. Guidance for preventing tickborne disease can be found online.
