Bluetongue virus in Europe: The current epidemiological situation

Abstract

The article reviews the history of BT occurrence in Europe and its present status. It describes the distribution of BT in Europe before 1998, the emergence of BTV in southern and eastern Europe in 1998-2006 and the epidemiology of BT in north-western Europe after 2006. Up to 1998, sporadic cases of BT were noted in Cyprus, on the Iberian Peninsula and on several Greek islands. However, since 1998, probably due to climatic changes, BTV has spread northwards into the Mediterranean Basin, where five BTV serotypes (1, 2, 4, 9 and 16) have been identified. In August 2006, BTV passed for the first time latitude 50°N, and BT outbreaks caused by BTV serotype 8 occurred in the Netherlands, Belgium, Germany, France and Luxembourg. Mass vaccination campaigns implemented in Europe in the spring of 2008 quickly limited the spread of disease caused by BTV-8, and it was eradicated by 2011. However, after a 3-year break, in September 2015, BTV-8 re-emerged in Europe, in central France, and subsequently spread throughout the entire country. In the following years, BTV-8 outbreaks were found in Switzerland, Germany, Belgium and Spain. In addition to BTV-8 outbreaks, BTV serotypes 1, 2, 4, 9 and 16 have recently circulated in Europe. As revealed by phylogeographic inference, the recent spread of BTV in Europe is a consequence of climatic, landscape and vertebrate host factors.