A dynamic model of the spatial spread of an infectious disease: the case of fox rabies in Illinois

A spatially explicit computer model is developed to examine the dynamic spr ead of fox rabies across the state of Illinois and to evaluate possible dis ease control strategies. The ultimate concern is that the disease will spre ad from foxes to humans through the pet population. Modeling the population dynamics of rabies in foxes requires comprehensive ecological and biological knowledge of the fox and pathogenesis of the rabi es virus. Variables considered including population densities, fox biology, home ranges, dispersal rates, contact rates, and incubation periods, can g reatly effect the spread of disease. Accurate reporting of these variables is paramount for realistic construction of a spatial model. The spatial mod eling technique utilized is a grid-based approach that combines the relevan t geographic condition of the Illinois landscape (typically described in a georeferenced database system) with a nonlinear dynamic model of the phenom ena of interest in each cell, interactively connected to the other appropri ate cells (usually adjacent ones). The resulting spatial model graphically links data obtained from previous m odels, fox biology, rabies information and landscape parameters using vario us hierarchical scales and makes it possible to follow the emergent pattern s and facilitates experimental stimulus/result data collection techniques. Results of the model indicate that the disease would likely spread among th e native healthy fox population from East to West and would occur in epidem iological waves radiating from the point of introduction; becoming endemic across the State in about 15 years. Findings also include the realization t hat while current hunting pressures can potentially wipe out the fox in the State, some level of hunting pressure can be effectively utilized to help control the disease.