Abstract
In
this paper we study a deterministic differential equation model for the
spread and control of malaria, which involve two infectious classes. We
derived the conditions for disease free and endemic equilibria. A comparison
of this model and three other models is made and tables of ranges
of parameter values are established. The
main results shows that a simplified NDM-system has a unique endemic
equilibrium for certain values of the ratio of mosquito to human population,
which is always a global attractor. Otherwise, there is
no endemic equilibrium and the disease-free equilibrium is a global attractor.
When the ratio of mosquito to human population changes the endemic
equilibrium changes and forms a curve Ce in the phase space parameterized
by this ratio. For a certain range of the rate of human population entering the
susceptible class (either by birth or migration) the original NDM-system has an
equilibrium on the curve Ce. This equilibrium
is a saddle with a four dimensional stable and one dimensional unstable
manifold. The unstable manifold is well approximated by this curve.