Persistence of Tb in possums: Insights from a spatially explicit, stochastic model

The majority of models for predicting the dynamics of bovine Tb in brushtail possums in New Zealand owe much to the pioneering work of the late Nigel Barlow. These non-spatial, deterministic models subsumed local disease dynamics by using a heterogeneous mixing term that assumed Tb was confined to a fraction of the population (in patches). However, the underlying mechanism(s) that could result in this heterogeneity of infection risk were obscure. We present a new individual-based, spatial, stochastic simulation model of Tb in possums that provides an explicit mechanism for simulating heterogeneous risk of infection based on a model of individual home range utilisation and disease susceptibility. The manipulation of parameters governing individual utilisation of space also means that processes such as non-linear contact structure can be handled naturally. We use the model to predict the persistence of Tb in possums under scenarios currently implemented for the management of bovine Tb in wildlife and determine conditions under which Tb might be predicted to persist despite control efforts.