Efficacy of tick sampling methods in urban parks.

Abstract

Amblyomma americanum (Lone star ticks) are parasites and vectors of diseases, including Ehrlichiosis. Questions remain about how an urban environment affects the host-seeking behavior of A. americanum across different life stages and thus the efficacy of different sampling methods. We sought to compare the efficacy of different sampling methods on A. americanum ticks in urban parks during the fall season and explore how the urban heat island (UHI) effect may impact each method’s efficacy. We hypothesized that, where the UHI effect is weaker near the city’s periphery, the CO2 trapping method would collect more A. americanum adults and nymphs because they can sense CO2 and walk multiple meters a day in the field, whereas the flagging method would collect more A. americanum larvae because they have a more limited dispersal ability and a tendency to quest vertically. We also hypothesized that, where the UHI effect is stronger near city center, hot, dry conditions would cause CO2 trapping to collect the most A. americanum ticks regardless of life stage, as ticks remained under the leaf litter to avoid desiccation. We sampled at two urban parks located in Louisville, Kentucky: one near city center and one near the periphery. At each sampling location (n=30), we collected ticks by conducting the flagging method in a 30 x 30 m square, and by setting out a CO2 trap in the middle of the square for 24 hours. We collected 846 ticks across the two parks, with the majority being A. americanum larvae (n=842, 99.5%). Overall, we found that the flagging method collected more A. americanum larvae (n=791, 93.5%) compared to CO2 trapping (n=51, 6.5%); however, trapping methods performed similarly in the park closest to city center. The knowledge gained from this research can help future tick surveillance efforts select the best sampling method to use in urban areas and provide the public with more accurate health information on tick-borne diseases