Simulating disease spread within a geographic information system environment.

Simulation modelling is a tool that can be used to investigate the effectiveness and efficiency of exotic disease control, eradication and surveillance strategies. The Australian Government Department of Agriculture, Fisheries and Forestry (DAFF) has been involved with disease simulation modelling for more than 10 years. Although the focus has been on foot and mouth disease, models are now being developed for avian influenza, classical swine fever and other diseases. Recent models are spatially explicit, and incorporate a range of animal species and production types. The models also encompass a range of disease transmission pathways, including farm-to-farm animal movements, movements through saleyards, windborne spread, spread by feral animals and the less well-defined phenomenon of local spread. The DAFF spatial models are unique in that they are developed within the environment of a geographic information system (GIS) - MapBasic/MapInfo. This simplifies the spatial elements of their code and improves their ability to handle spatial data layers. Such layers vary, but may include the following: farm locations or boundaries; masks identifying grazing; cropping and non-agricultural land; water bodies and waterways; population centres, administrative boundaries and roadways; vegetation and other land cover masks; and, where relevant, elevation. The GIS environment also provides immediate access to sophisticated maps and tabular outputs.