Park Size and Trail Environment Influence the Seasonal Transmission Risk of Tick-Borne Pathogens in Nashville Metropolitan Area Parks, Tennessee.

Abstract

We identified tick and tick-borne pathogen presence across 24 Nashville Metropolitan Area parks and evaluated factors that influence their occurrence. Parks were categorized by size (small, medium, large, and extra-large; n = 6 per group) and drag sampled during spring, summer, and fall from June 2020 to June 2021. Drag transects were equally distributed between trails and forested areas. A total of 25,081 ticks were collected, with Amblyomma americanum (A. americanum) constituting 99.5% of collections, followed by Dermacentor variabilis (D. variabilis), Amblyomma maculatum (A. maculatum), and Ixodes scapularis (I. scapularis). Adult and nymphal ticks were screened for pathogens, which consisted of seven bacterial and two viral species. In A. americanum (n = 375 pools), we identified Ehrlichia chaffeensis in 15 pools, as well as Ehrlichia ewingii and Panola Mountain Ehrlichia in 14 pools. In A. maculatum (n = 8 pools), we identified Rickettsia parkeri in three pools. Amblyomma americanum and D. variabilis adult and nymph collections were highest in the summer, A. maculatum collection was highest in the spring, and I. scapularis collection was highest in the fall. Large parks supported the highest aggregate tick densities across all life stages-adults (0.42 ticks/100 m2), nymphs (1.33 ticks/100 m2), and larvae (111.42 ticks/100 m2). Additionally, nymph abundance was significantly greater in forested areas (14.3 ± 3.01) compared with trails (3.98 ± 0.56) across all park size categories. Our findings indicate that seasonal patterns in tick abundance are influenced by park size and that the maintenance of well-defined trails can help to mitigate the risk of exposure to ticks and their associated pathogens during peak activity seasons in urban park environments.