This domain is composed of alpha-helices and contains long extending loops. The second domain is larger and consists of the residues 1–120 and 250–349. Įach monomer subunit consists of two distinct domains where the domain that forms the outer surface of the core, is the smaller domain and it consists of the central third of the polypeptide chain (residues 121–149), which is folded into a beta-sheet. The protein VP7 of the BTV, consists of 349 amino acids and is encoded by dsRNA genome segment 7, which is 1154–1156 base pairs long and contains only a single open reading frame. The inner capsid or core is composed of the two major proteins VP3 and VP7 and three minor ones VP1, VP4, and VP6 and the outer capsid is composed of VP2 and VP5. The viral particle contains seven structural proteins named viral protein (VP)1 through 7 and four non-structural proteins named NS1 through 4. īTV has a distinctive structure of an outer capsid that surrounds an inner capsid core that itself is composed of two protein layers. The spread of the diseased is therefore highly reliant on the vector and outbreaks are seen to be seasonal.
BTV is carried and spread by blood-feeding Culicoides midges, which act as a vector and transmit the disease when feeding. BTV has become common throughout the world and is particularly important economically, not only due to the direct loss of livestock through fatalities, but also the indirect loss due to banning livestock movement to prevent the spread of infection. A number of different symptoms are seen in different infected animals including depression, fever, nasal discharge, facial oedema, and general muscle weakness. The disease is symptomatically seen most often in sheep, occasionally in goats, and rarely in cattle and wild ruminants.
BTV affects many domestic and wild ruminants. Twenty-seven serotypes of BTV have been identified to date. Bluetongue virus (BTV) belongs to the genus Orbivirus from the family Reoviridae.
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