Ecological Niche Modeling of Lyme Disease Risk in Maine Based on Human Case Data

Ixodes scapularis, the blacklegged tick,is the primary vector for the Lyme disease-causing bacteria Borrelia burgdorferi in the United States.Lyme disease poses a significant concern to the state of Maine, as both the number and geographic distribution of cases across the state have been steadily increasing over the past two decades. In 2001, there were 108 confirmed or probable cases of Lyme disease in Maine compared to 1404 cases in 2018. Using tick-borne disease human case data from the Maine CDC andArcGIS software, I created three Lyme disease maps for the years 2001, 2009, and 2017. These maps show the number of confirmed and probable cases of Lyme disease in Maine for each town, where case coordinates were randomly assigned within the town boundary that the patient resides in. I used Maxent modeling to locate areas of high-risk for Lyme disease cases in Maine. The land cover variables were taken from the National Land Cover Database and the climate variables were based onBioclimatic variables from WorldClim. The final variable in this model was the distance from hospital. The findings of this study show that the distribution of Lyme disease cases across the state of Maine increased from 2001 to 2017. The coldest temperature of the coldest month was the best predictor for Lyme disease case prevalence, and land cover was not an important predictor for Lyme disease cases. These findings pose research questions on the causality behind these trends