Mapping the basic reproduction number (R0) for vector-borne diseases: A case study on bluetongue virus

Geographical maps indicating the value of the basic reproduction number, R 0 , can be used to identify areas of higher risk for an outbreak after an introduction. We develop a methodology to create R 0 maps for vector-borne diseases, using bluetongue virus as a case study. This method provides a tool for gauging the extent of environmental effects on disease emergence. The method involves integrating vector-abundance data with statistical approaches to predict abundance from satellite imagery and with the biologically mechanistic modelling that underlies R 0 . We illustrate the method with three applications for bluetongue virus in the Netherlands: 1) a simple R 0 map for the situation in September 2006, 2) species-specific R 0 maps based on satellite-data derived predictions, and 3) monthly R 0 maps throughout the year. These applications ought to be considered as a proof-of-principle and illustrations of the methods described, rather than as ready-to-use risk maps. Altogether, this is a first step towards an integrative method to predict risk of establishment of diseases based on mathematical modelling combined with a geographic information system that may comprise climatic variables, landscape features, land use, and other relevant factors determining the risk of establishment for bluetongue as well as of other emerging vector-borne diseases.