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Bovine Viral Diarrhea (BVD) or Bovine Viral Diarrhoea (UK English), and previously referred to as Bovine Virus Diarrhoea (BVD), is a significant economic disease of cattle which is endemic in the majority of countries throughout the world. The causative agent, bovine viral diarrhea virus (BVDV) is a member of the ''Pestivirus'' genus of the family Flaviviridae.〔 BVD infection results in a wide variety of clinical signs, due to its immunosuppressive effects, as well as having a direct effect on respiratory disease and fertility. In addition, BVD infection of a susceptible dam during a certain period of gestation can result in the production of a persistently infected (PI) fetus. PI animals recognise intra-cellular BVD viral particles as ‘self’ and shed virus in large quantities throughout life; they represent the cornerstone of the success of BVD as a disease. ==Virus classification and structure== BVDV is a member of the ''Pestivirus'' genus, belonging to the family ''Flaviviridae''. Border Disease Virus (Sheep) and Classical Swine Fever Virus (Pigs) are other members of this genus which also cause significant financial loss to the livestock industry. Pestiviruses are small, spherical, single-stranded, enveloped RNA viruses of 40 to 60 nm in diameter. The genome consists of a single, linear, positive-sense, single-stranded RNA molecule of approximately 12.3 kb. Two BVDV genotypes are recognised, based on the nucleotide sequence of the 5’untranslated (UTR) region; BVDV-1 and BVDV-2. BVDV-1 isolates have been grouped into 16 subtypes (a –p) and BVDV-2 has currently been grouped into 3 subtypes (a – c). BVDV strains can be further divided into distinct biotypes (cytopathic or non-cytopathic) according to their effects on tissue cell culture; cytopathic (cp) biotypes, formed via mutation of non-cytopathic (ncp) biotypes, induce apoptosis in cultured cells. Ncp viruses can induce persistent infection in cells and have an intact NS2/3 protein. In cp viruses the NS2/3 protein is either cleaved to NS2 and NS3 or there is a duplication of viral RNA containing an additional NS3 region. The majority of BVDV infections in the field are caused by the ncp biotype.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Bovine virus diarrhea」の詳細全文を読む スポンサード リンク
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