Bluetongue in the Mediterranean: prediction of risk in space and time

Bluetongue virus (BTV) causes an infectious, non-contagious disease of ruminants and is transmitted by Culicoides biting midges. Currently an unprecedented epidemic of bluetongue (BT) is sweeping the Mediterranean Basin and a large number of countries are now involved in managing the disease. Therefore the development of new methods for accurate prediction of BT risk in space and time is essential. The life-history parameters of Culicoides and other parameters of the BTV transmission cycle are highly sensitive to climatic conditions. Thus the potential exists to define the limiting conditions and likelihood of spread of BTV, using geographical information systems (GIS) to combine vector, virus and environmental information. This paper reviews the progress and current status of GIS and remote sensing (RS) as applied to BTV in the Mediterranean Basin. These analytical tools have aided the determination of the relative roles of different Culicoides vectors in BTV transmission across the region and have facilitated prediction of the wide-scale distribution of the major field vector C. imicola from RS climate variables. On the basis of findings and lessons from statistical models of vector distribution, a strategy for development of dynamic biological or process-based models of BT risk is suggested.

Keywords: Bluetongue virus; Mediterranean; Culicoides obsoletus; Culicoides pulicaris; Culicoides imicola; distribution; climate; remote sensing; risk map