Database Reference
In-Depth Information
U1 D
=
F1 D * EXP(LOGN(S1 D) * F1 D*DT)
{
Model maturation rate for
survivors, 1/DAY. Hatch rate
=
instantaneous survival fraction * maturation
rate.
}
U1 H
=
F1 H * EXP(LOGN(S1 H) * F1 H*DT)
{
Model maturation rate for
survivors, 1/DAY. Hatch rate
=
instantaneous survival fraction * maturation
rate.
}
15.2 The Spatial Dynamic Spread of Rabies in Foxes
1
15.2.1 Introduction
A spatially explicit computer model is developed to examine the dynamic spread
of fox rabies across the state of Illinois and to evaluate possible disease control
strategies. The ultimate concern is that the disease will spread from foxes to humans
through the pet population. We are also concerned about the significant loss of an
indigenous species.
Modeling the population dynamics of rabies in foxes requires comprehensive
ecological and biological knowledge of the fox and pathogenesis of the rabies virus.
Variables considered, including population densities, fox biology, home ranges, dis-
persal rates, contact rates, and incubation periods, can greatly affect the spread of
disease. Accurate reporting of these variables is paramount for realistic construction
of a spatial model. The spatial modeling technique utilized is a grid-based approach
that combines the relevant geographic condition of the Illinois landscape (typically
described in a georeferenced database system) with a nonlinear dynamic model of
the phenomena of interest in each cell, interactively connected to the other appro-
priate cells (usually adjacent ones).
The resulting spatial model graphically links data obtained from previous mod-
els, fox biology, rabies information, and landscape parameters using various hierar-
chical scales and makes it possible to follow the emergent patterns. It also facilitates
experimental stimulus/result data collection techniques. Results from the model in-
dicate that the disease would likely spread among the native healthy fox population
from east to west and would occur in epidemiological waves radiating from the
point of introduction; becoming endemic across the state of Illinois in about 15 to
20 years. Findings also include the realization that while current hunting pressures
can potentially extirpate the Illinois fox population, some level of hunting pressure
could be used to control the disease.
Spatially explicit modeling of complex environmental problems is essential
for developing realistic descriptions of past behavior and the possible impacts of
1
Condensed from: A Dynamic Model of the Spatial Spread of an Infectious Disease: The Case of
Fox Rabies in Illinois, with Brian Deal, Cheryl Farello, Mary Lancaster, Thomas Kompare, Bruce
Hannon, Environmental Modeling and Assessment, 5:47-62, 2000.
