Development of a Novel Rabies Simulation Model for Application in a Non-endemic Environment

Domestic dog rabies is an endemic disease in large parts of the developing world and also epidemic in previously free regions. For example, it continues to spread in eastern Indonesia and currently threatens adjacent rabies-free regions with high densities of free-roaming dogs, including remote northern Australia. Mathematical and simulation disease models are useful tools to provide insights on the most effective control strategies and to inform policy decisions. Existing rabies models typically focus on long-term control programs in endemic countries. However, simulation models describing the dog rabies incursion scenario in regions where rabies is still exotic are lacking. We here describe such a stochastic, spatially explicit rabies simulation model that is based on individual dog information collected in two remote regions in northern Australia. Illustrative simulations produced plausible results with epidemic characteristics expected for rabies outbreaks in disease free regions (mean R0 1.7, epidemic peak 97 days post-incursion, vaccination as the most effective response strategy). Systematic sensitivity analysis identified that model outcomes were most sensitive to seven of the 30 model parameters tested. This model is suitable for exploring rabies spread and control before an incursion in populations of largely free-roaming dogs that live close together with their owners. It can be used for ad-hoc contingency or response planning prior to and shortly after incursion of dog rabies in previously free regions. One challenge that remains is model parameterisation, particularly how dogs’ roaming and contacts and biting behaviours change following a rabies incursion in a previously rabies free population.Author Summary: Rabies in domestic dog populations still causes >50,000 human deaths worldwide each year. While its eradication by vaccination of the reservoir population (dogs and wildlife) was successful in many parts of the world, it is still present in the developing world and continues to spread to new regions. Theoretical rabies models supporting control plans do exist for rabies endemic regions; however these models usually provide information for long-term programs. Here, we describe a novel rabies simulation model for application in rabies-free regions experiencing an incursion. The model simulates a rabies outbreak in the free-ranging dog population in remote indigenous communities in northern Australia. Vaccination, dog density reduction and dog confinement are implemented as control strategies. Model outputs suggest that the outbreak lasts for an average of 7 months and typically spreads through all communities of the region. Dog vaccination was found to be the most effective response strategy. The model produces plausible results and can be used to provide information for ad-hoc response planning before and shortly after rabies incursion.