Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: May 30, 2003
Publication Date: March 1, 2005
Citation: Ridpath, J.F. 2005. Classification and molecular biology. In: Goyal, S.M., Ridpath, J.F., editors. Bovine Viral Diarrhea Virus: Diagnosis, Management, and Control. 1st edition. Ames, IA: Blackwell Publishing Professional. p. 65-80. Technical Abstract: This chapter is a review that summarizes the molecular biology, variation and classification of bovine viral diarrhea viruses (BVDV). BVDV are a diverse group of viruses that are classified within the pestivirus genus of the Flavivirus family. Like other Flaviviruses they are enveloped and have a single stranded RNA genome. The genome consists of one large open reading frame (ORF) flanked by 5' and 3' untranslated regions (UTR). The 5' UTR is highly conserved among pestiviruses due to the dependence of viral replication on tertiary structures formed by the 5' UTR sequences. The polyprotein coded for by the large ORF is cleaved post translation into the individual viral proteins. Pestiviruses produce two gene products that are unique to the genus. These are the N**pro, an autoprotease, and E**rns, a structural protein with a unique Rnase activity. BVDV strains are highly variable and can be segregated into two different genotypes, BVDV1 and BVDV2. BVDV1 and BVDV2 strains may be differentiated by sequence comparison, monoclonal antibody binding and virus neutralization using polyclonal sera. However, the most frequently used test for segregating BVDV strains is based on differential amplification of the 5' UTR. Viruses from either genotype may belong to one of two genotypes, cytopathic and noncytopathic, based in their activity in cultured epithelial cells. The majority of strains found in nature belong to the noncytopathic biotype. Biotype does not correlate with virulence in vivo. Determining genotype is usually more important to control programs than determining biotype.