Determining environmental predictors of Amblyomma americanum (Lone Star Tick) population densities in central Georgia, United States: 2019 and 2021 Público

Walsh, Timothy (Spring 2022)

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Vector-borne diseases pose a significant public health threat due to the number of diseases and pathogens these vectors can transmit to humans. Specifically, tick-borne pathogens, like Borrelia, the pathogen that causes Lyme Disease, and Rickettsia, the pathogen that causes Rocky Mountain Spotted Fever, have traditionally been of greatest concern. Recently however, a new disease has emerged in the southern continental United States. Vectored by the Lone Star Tick, Amblyomma americanum, Heartland virus is a relatively novel pathogen that was recently confirmed to be carried by Amblyomma in Georgia. Population sizes for this tick have been on the rise in recent years, and a deeper understanding of when population sizes peak within a given field season was needed to determine risks. For this study, we collected tick abundance and density values from two field sites in Putnam and Jones counties on a weekly basis during the spring, summer, and early fall of 2019 and 2021. Weather factors, like rainfall, temperature, and humidity, were abstracted from an online source and analyzed together with collected density values to determine biologically plausible environmental drivers. It was determined through cross-correlations and predictive modeling that the strongest predictors of population sizes were the maximum daily temperature, cumulative rainfall, and relative humidity 15 days prior to a collection event. When determining safety guidelines and recommendations around tick-borne infections in the future, these values should be considered for their relationship with population size, as increases in population sizes increase the risk of pathogen transmission.

Table of Contents

Table of Contents

Introduction. 1

Methods. 4

Study Sites. 4

Data Collection. 7

Data Analysis. 8

Results. 10

Discussion. 19

Conclusions and Recommendations. 20

References. 21

Appendix. 23

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