ON THE SPATIAL SPREAD OF RABIES AMONG FOXES WITH IMMUNITY

We consider a model for the spatial spread of rabies in foxes, where a certain proportion of the foxes develop a natural immunity to the disease. We modify the model of Murray et al. (1986, Proc. R. Soc. Lond. B 229, 111-150) to include a population of immune foxes and find that, with realistic estimates for the size of this class, this aspect has little effect on the propagation speed of the initial wave of the rabies epidemic but it does affect the behavior of the periodic outbreaks associated with the oscillating tail of the wave. We use the modified model to estimate the width of a rabies break which would be required to contain the epidemic. We also investigate the effect of spatial dispersal of susceptible and infected foxes. Previous work hypothesized that the required break width might depend on whether the break was created by killing foxes or by vaccinating them against rabies. With our model we consider this difference and find that the break width does not change significantly unless the rate of spatial dispersal is large. © 1992 Academic Press Limited.