Classification Tree Methods for Analysis of Mesoscale Distribution of Ixodes ricinus (Acari: Ixodidae) in Trentino, Italian Alps

Cases of Lyme disease and tick borne encephalitis were recently recognized in the province of Trento, Italian Alps. Assessment of areas of potential risk for these tick-borne diseases is carried out by a model based on CART (Classification and Regression Trees), using both discrete and continuous variables. Data on Ixodes ricinus (L.) occurrence resulted from samplings carried out by standard methods in 99 sites throughout the province of Trento. A series of environmental parameters were recorded from each site. Mesoscale population densities of roe deer, Capreolus capreolus (L.), were considered. Cross-validation and bootstrap techniques were used in the definition of the model. The CART model discriminates two variables which appear to have the greatest effect on the occurrence of ticks: altitude and a.s.l. or on volcanic substrata. The model seems to be effective in identifying the mesoscale areas at greater potential risk