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Movement of adult female #Ixodes scapularis (Acari: Ixodidae) in response to experimental manipulations of temperature and moisture
AbstractThis study investigated the response of #tick movement to temperature and moisture stress, key factors influencing #tick-borne disease risk. The blacklegged #tick, #Ixodes scapularis Say, a parasite found widely across the United States, transmits multiple pathogens and spends most of its life off-host, exposed to varying environmental conditions. We quantified the movement of adult female I. scapularis during experimental exposures to 5 temperatures (10 °C to 25 °C) crossed with 3 target relative humidities (75%, 84%, and 100%) using a Drosophila activity monitor (DAM). We then modeled the probability of #tick movement as a function of temperature and vapor pressure deficit (VPD), a measure of moisture stress derived from the observed temperature and relative humidity, over 4 different trial durations (30, 45, 60, and 75 min). For all durations, the best-fitting model contained fixed effects of temperature, VPD, and their quadratic terms. The predicted probability of #tick movement was concave-down with VPD, with movement increasing up to a certain threshold and then decreasing. Consistent with the cool-weather adult activity period, the predicted probability of #tick movement was highest at 10 °C, decreasing as temperature increased and increasing slightly at the warmest temperatures. We conclude that adult female I. scapularis respond non-linearly to increases in both temperature and moisture stress; the DAM can be a useful tool for tracking I. scapularis movement over sub-daily time scales; and trial duration does not strongly impact the estimated response surface over the periods evaluated.