Background
Lyme disease (LD) incidence is increasing globally, driven by changes to habitat and human-vector interactions. Effective prevention relies on local and individual-level understanding of risk and ecosystem interactions. Despite frequent exposure to tick habitats, little is known about tick bites and LD risk among hill, trail, and mountain runners. This study aimed to evaluate the period prevalence of tick bites and incidence of LD in hill runners in Scotland, UK and examine preventive behaviours.

Methods
A cross-sectional retrospective survey of Scottish hill runners was conducted in June-July 2024. Hill runners aged 18+ resident in Scotland for the 12 months preceding the survey were eligible. Period prevalence was calculated as the proportion of hill runners with at least one self-reported tick bite in the 12 months preceding the survey. Treated suspected LD incidence was calculated for all study participants and those registered in competitive hill races. Multiple logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) of having a tick bite, for variables including age, sex, running hours per week, proportion of running that is hill running, other outdoor activity hours per week, frequency of insect repellent use, full leg and arm cover use, and full body tick checks.

Results
212 hill runners (56.1% male) completed the survey. Period prevalence of at least one tick bite was 82.5% (95%CI 76.76-87.40). Incidence of treated suspected LD for the 212 study participants was 4245.3 per 100,000 (95%CI 1941.21-8058.87), and the minimum estimate in 4668 registered competitive hill racers was 150.0 per 100,000 per year (95%CI 60.29-309.97). Most hill runners reported never/infrequently wearing full leg cover (67.9%), arm cover (58.0%), or using insect repellent (74.5%). Regularly/almost always conducting a tick check was associated with higher odds of at least one tick bite (OR 8.52, 95%CI 3.29-22.90, p<0.001), whereas regularly/almost always wearing full leg cover was associated with lower odds (OR 0.35, 95%CI 0.13-0.89, p=0.029), versus never/infrequently.

Conclusions
A high reported period prevalence of tick bites and incidence of treated suspected LD among surveyed hill runners in Scotland aligned with the low adherence to tick bite prevention behaviours in this population. Improving adherence with leg cover recommendations may lower the risk of tick bites. Raising awareness of tick bite risk and prevention may benefit hill runners internationally as the sport grows.