An Acarological Risk Model Predicting the Density and Distribution of Host-Seeking Nymphs in Minnesota.

is the vector of at least seven human pathogens in Minnesota, two of which are known to cause Lyme disease ( sensu stricto and ). In Minnesota, the statewide incidence of Lyme disease and other -borne diseases and the geographic extent over which cases have been reported have both increased substantially over the last two decades. These changes correspond with an expanding distribution of over a similar time frame. Because the risk of exposure to -borne pathogens is likely related to the number of ticks encountered, we developed an acarological risk model predicting the density of host-seeking nymphs (DON) in Minnesota. The model was informed by sampling 81 sites located in 42 counties in Minnesota. Two main foci were predicted by the model to support elevated densities of host-seeking nymphs, which included the seven-county Minneapolis-St. Paul metropolitan area and counties in northern Minnesota, including Lake of the Woods and Koochiching counties. There was substantial heterogeneity observed in predicted DON across the state at the county scale; however, counties classified as high risk for -borne diseases and counties with known established populations of had the highest proportion of the county predicted as suitable for host-seeking nymphs (≥ 0.13 nymphs/100 m). The model provides insight into areas of potential population expansion and identifies focal areas of predicted suitable habitat within counties where the incidence of -borne diseases has been historically low.