Date on Senior Honors Thesis

5-2026

Document Type

Senior Thesis

Degree Name

B.S.

Department

Biology

Committee Chair

Rachel Pigg

Committee Member

Jeffrey Masters

Committee Member

Lee Thompson

Author's Keywords

Amblyomma americanum; Kentucky; Lone star tick; CO2 trapping; flagging; urban heat island

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.

Lay Summary

Lone star ticks (Amblyomma americanum) are parasites and vectors, which means they carry infectious bacteria or viruses that cause human diseases. To estimate or reduce tick abundance, we need a reliable means of capturing ticks; however, hot, dry conditions in urban environments could alter tick behavior and affect the efficacy of different tick capture methods. Our study investigated which method of capturing Lone star ticks is the best in urban Kentucky parks during the fall season. We hypothesized that, in cooler areas away from city center, the best trapping method to use would vary depending on Lone star tick life stage. The CO2 trapping method would be the better method for collecting adults and nymphs because they are attracted to CO2 and can walk long distances, whereas the flagging method would be better at collecting larvae because they are more limited in their movement and climb vertically on vegetation to access hosts. We also hypothesized that, in hotter areas near the city center, the CO2 trapping method would be the most efficient method for all life stages because the increased heat may cause all ticks to stay under the leaf litter while seeking hosts to avoid drying out. We collected ticks at two urban parks in Louisville, Kentucky: one near city center and one near the periphery. At each sampling location within a park, we conducted the flagging method in a 30 x 30 m square and then set out a CO2 trap in the middle of that square for 24 hours. Overall, the flagging method collected more Lone star tick larvae (n=791, 93.9%) compared to CO2 trapping (n=51, 6.1%); however, the two trapping methods performed similarly in the park closest to city center. The knowledge gained from this research can help inform future efforts to collect ticks in urban parks and provide the public with more accurate health information on tick-borne diseases. 

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