To construct a mathematical model that explains the spread of endemic
diseases, generally the populations are decomposed into groups. The number of
these groups depends on the dynamics of the disease that is being modeled. We use
an SIR model, that is the populations is divided into three groups, susceptible,
infectious and recovered. The model that we offer is to explain the dynamics of
rabies within a single species animal population. We use the following notation for
variables:
N(t)= Total number of animals at time t,
S(t)= Number of susceptible animals at time t,
I(t)= Number of infected animals at time t,
R(t)= Number of recovered animals at time t.
It is clear that
for all t. The transfer diagram for the model can be seen in Fig.1. For the
construction of the model, we used the facts that rabies is a fatal disease for animals