Bovine viral diarrhea virus (BVDV) is classified as a member of the Pestivirus genus of the Flaviviridae family. BVDV is one of the most important viral pathogens of ruminants worldwide, causing severe economic losses. Infection results in a wide range of clinical manifestations, ranging from mild respiratory disease to fetal death and mucosal disease. The virus particles are small and contain a singlestranded, positive-sense RNA molecule of approximately 12.3 kb with one large open reading frame flanked by two untranslated regions (5’UTR and 3’UTR). The polyprotein is proteolytically cleaved by viral and host proteases resulting in the formation of mature viral proteins. It is well established that BVDV strains show considerable genetic diversity. BVD viruses are classified as two species: BVDV-1 and BVDV-2. Quite recently, a new putative species, BVDV-3, was detected. The viruses exist as one of two biotypes: cytopathic or non- cytopathic, based on their activity in cell cultures. The phylogenetic analysis of the 5’UTR and Npro region has revealed at least 21 distinct subtypes of BVDV-1 and 4 subtypes of BVDV-2. Genetic diversity of BVD viruses has serious clinical implications such as immune evasion, increase of virulence, host range alteration and also affects the efficacy of vaccination programmes and diagnostic methods.
1. Introduction. 2. Characteristics of BVD virus. 3. Genetic diversity. 4. The importance of genetic variation. 5. Conclusion
