A mathematical model for the control of diseases in wildlife populations: culling, vaccination and fertility control

Abstract

Recent advances have permitted the red fox ( Vulpes vulpes) to be vaccinated against rabies in order to control the European epidemic. Vaccination is also the preferred long-term strategy for controlling bovine tuberculosis ( Mycobacterium bovis) (TB) in the European badger ( Meles meles) in England. We discuss a model to compare the efficacy of various disease control strategies, including temporary and permanent sterilisation. By using rabies and TB as examples of acute and chronic diseases, the model shows that lethal control can be more effective at disease eradication in an isolated population than vaccination. This is due to the birth of larger numbers of susceptible individuals during a vaccination campaign, which makes it harder to keep the population below the critical threshold density. This difference was very marked for the progressive disease of tuberculosis. The inclusion of an abortifacient increased the chances of disease control to levels close to that of lethal control. If the abortifacient is replaced by a permanent contraceptive then the chances of disease eradication and population extinction were very similar to that of lethal control, since the birth of susceptibles is now much reduced. These results are also of relevance in the control of wildlife diseases in threatened populations or species.