Bovine tuberculosis (Mycobacterium bovis – Tb) is endemic in wild brushtail possum (Trichosurus vulpecula) populations in New Zealand. The mainstay of Tb eradication strategies has been the use of lethal control, usually using poison baits in an attempt to keep possum population densities below the theoretical threshold for disease eradication. However, vaccination of possums using Bacille Calmette-Guerin (BCG) has been shown to afford some protection to possums from Tb infection with an efficacy of 70% being demonstrated in wild individuals vaccinated by both intranasal aerosol and conjunctival instillation (Corner et al. 2002). Hence BCG is being considered for more wide-scale use to help control the disease. However, little information exists on the duration of protection afforded by BCG in possums and how decay in vaccine immunity might affect vaccination strategies. We explored the potential for vaccination to complement or replace existing lethal control strategies using a spatially explicit stochastic model of possums and Tb. The model simulates events (i.e. birth, death, infection, dispersal) for individual possums located uniquely in a two-dimensional landscape. The model is partially based on the deterministic, non-spatial, Anderson/May type S1 (susceptible/infected) compartment model of Barlow (2000) and hence, uses many of the same parameters. However, the spatial structure is modelled explicitly and hence, disease transmission occurs at a local scale and is based on the probability of contact between infected and susceptible individuals, which is dependent on the degree of home range overlap. Secondly, the model includes both sexes to account for sex-specific dispersal behaviour.
|Author||Ramsey, D. and Efford, M.|
|Secondary title||13th Australasian Vertebrate Pest Conference|
|Place published||Wellington, NZ|