Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 15, 2009
Publication Date: February 15, 2009
Citation: Ridpath, J.F. 2009. BVDV Strain Variability. In: Proceedings of the Western Veterinary Conference, February 15-19, 2009, Las Vegas, Nevada. Available: http://www.wvc.org/. Technical Abstract: Bovine viral diarrhea virus (BVDV) is an umbrella term for a group of viruses within the pestivirus genus of the flavivirus family. Actually the term should be bovine viral diarrhea viruses rather than virus, as there are two different species (BVDV1 and BVDV2), two different biotypes (cytopathic and noncytopathic), different virulence types and numerous strains included under the BVDV umbrella. BVDV infections may result in enteric, respiratory, and/or reproductive disease of varying severity depending on the strain of BVDV virus and host related factors such as immune status, reproductive status and presence of secondary pathogens. Regardless of strain, biotype or species, acute BVDV infections are always accompanied by suppression of the immune system. The immune suppression that follows acute infections is due, at least in part, to the death of immune cells within lymph nodes and gut associated lymphoid tissue and reduction of numbers of circulating white blood cells. The suppression of the immune system can leave the animal weakened and vulnerable to secondary infections. Cross protection between the two species is not complete and for this reason many manufacturers include both species (also known as genotypes) in the make up of vaccines. As stated above, there are cytopathic and noncytopathic versions of BVDV within both species. Noncytopathic strains from either genotype can establish persistent infections. BVDV strains also vary in virulence. To date the most virulent form of BVD, severe acute BVDV or hemorrhagic syndrome, is only observed with BVDV2 strains. This is not to say that all BVDV2 strains are highly virulent or that BVDV1 strains never cause clinically severe disease.