Bluetongue disease virus is a vector-borne hemorrhagic disease of ruminant species in many tropical, subtropical and some temperate regions, including much of the Americas, Africa, southern Asia and northern Australia. It is caused by Bluetongue virus (BTV) which has a double stranded RNA genome (Orbivirusgenus in the family Reoviridae). BTV is transmitted to ruminants via certain species of biting midges (Culicoides spp.). The major symptoms of infection are high fever, excessive salivation, swelling of the face and tongue, and cyanosis of the tongue. Nasal symptoms are common, including nasal discharge and stertorous respiration.
Phylogenetic analyses show that it represents the least conserved region of the BTV genome, separating primarily into 26 distinct serotypes which are characterized by its geographic regions. BTV serotype 1 was identified in North of Africa and Europe but even it has been reported in USA. BTV serotype 2 was reported for the first time in Tunisia and Algeria. The virus then spread round the Mediterranean. BTV serotype 4 was identified in Oman but it has been reported in Europe and Africa. BTV serotype 6 was identified in Netherlands but it has been reported in USA too. BTV serotype 8 was identified in Netherlands but it has been reported in several Europe countries. BTV serotype 9 was reported for the first time in Libya and India. BTV serotype 11 was reported for the first time in Zimbabwe but its spread for all Europe. BTV serotype 16 was reported for the first time in Oman.