THE SPATIOTEMPORAL DYNAMICS OF AMBLYOMMA AMERICANUM AND THEIR INFLUENCE ON TICK DETECTION

Daniel S. Marshall

Ticks and the pathogens they transmit pose significant threats to human and animal health. Estimates of tick abundance and distribution are used to determine the risk of tick-host contact and inform tick control decisions. Methods of sampling ticks (i.e., drag cloths and CO2-baited traps) differentially detect ticks based on foraging behavior (i.e., questing and hunting). Questing ticks are better sampled using drag cloths while those that hunt their hosts are effectively captured using traps. Hunting ticks like Amblyomma americanum are highly mobile. This presents a problem when estimating their abundance because measures of tick populations may be less reliable for species that actively move in search of a host. Host-seeking behavior and abundance may be influenced by factors like ambient temperature and tick energy reserves. Determining the mechanisms influencing tick behavior and abundance will improve our ability to estimate tick hazard and mitigate the risk of pathogen transmission. Here I explore the factors affecting the detection of adult A. americanum. These factors include their local abundance, spatial arrangement, movement capabilities, mortality, lipid reserves, and environmental conditions experienced in the previous weeks. My results demonstrate the extremes of A. americanum movement and reveal how measures of tick hazard are influenced by local abundance. Additionally, my results call into question the utility of lipid content as a biomarker for tick condition. Using mark-recapture techniques, video tracking software, and survivorship analysis, I generated data that I used to parameterize a model simulating tick detection. My simulation suggests that past temperatures experienced by ticks will determine their detection through an interaction between abundance and host-seeking behavior. The results I present here demonstrate the first evidence of thermal carryover effects in A. americanum which have been rarely explored in other tick species. Collectively, this work suggests that the number of ticks detected in the environment are the result of their local abundance and movement capabilities, modified by the temperatures they have previously experienced.

THE SPATIOTEMPORAL DYNAMICS OF AMBLYOMMA AMERICANUM AND THEIR INFLUENCE ON TICK DETECTION

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