Spatial diffusion of raccoon rabies in Pennsylvania, USA

Identification of the geographic pattern of diffusion of a wildlife disease could lead to information regarding its control. The objective of this stu dy was to model raccoon-rabies diffusion in Pennsylvania to identify geogra phic constraints on the diffusion pattern for potential use in bait-vaccina tion strategies. A trend-surface analysis (TSA) was used as a spatial filte r for month to first report by county location. A cubic polynomial model wa s fitted (R-2 = 0.80). Velocity vectors were calculated from the partial de rivatives of the model and mapped to demonstrate the instantaneous speed of diffusion at each location. A main corridor of diffusion through the ridge and valley section of the state was evident early in the outbreak. Once th e disease reached the northern counties, the disease moved west toward Ohio . I believe that TSA was useful in identifying the pattern of raccoon-rabie s diffusion across the state from the inherent noise of disease-reporting d ata. (C) 1999 Elsevier Science B.V. All rights reserved.