Bluetongue and epizootic hemorrhagic disease viruses: recent developments with these globally re-emerging arboviral infections of ruminants

Bluetongue (BT) and epizootic hemorrhagic disease (EHD) are globally re-emerging diseases of domestic and wild ruminants, respectively caused by BT virus (BTV) and EHD virus. Both viruses are transmitted by hematophagous midges; however, newly recognized BTV serotypes may be transmitted horizontally without requirement for any biological vector. The global range of these viruses and/or their associated diseases have changed remarkably in recent years, most notably with the invasion of Europe by multiple serotypes of BTV since 1998. Although not zoonoses, the unanticipated emergence of BT and EHD in several different areas of the world provides a uniquely sobering and unambiguous reminder of the potential consequences of climate change on the distribution and severity of vector-borne diseases. Recent experiences with these viruses have also emphasized the need for effective, DIVA-compatible vaccines to combat anticipated future incursions, as existing vaccines have serious inherent deficiencies.