High resolution spatial modeling of Dermacentor spp. tick density at Turnbull National Wildlife Refuge in Spokane County, WA

The Rocky Mountain Wood Tick (Dermacentor andersoni) and the American Dog Tick (Dermacentor variabilis) are two widespread tick species in Eastern Washington, capable of transmitting a range of human and veterinary pathogens. Predicting and mapping the relative density of these tick species at a high resolution would allow the public to take steps to avoid high density locations. In order to develop such a map for the public use area of Turnbull National Wildlife Refuge (TNWR) in Spokane County, we established thirty 50 meter transects across 6 different land-cover types, and collected ticks using the drag method once a week from March to July in 2018. We also collected vegetation data, burn status, small mammal abundance, land-cover type and large mammal counts at the same transects as covariates. 74.4% of the variation in the questing tick density across these transects was explained using the best Poisson regression model with shrub cover, land-cover type and burn status as predictor variables. We created a shrub cover layer across the public use area at TNWR at a 10m-by-10m resolution using LiDar data obtained through the Puget Sound LiDar consortium. We used this shrub cover layer, along with land-cover type and burn status to generate a high-resolution map of predicted questing tick density across the public use area of TNWR. During the Spring of 2020, we validated this map, and extended it to other areas of Spokane County.