Biotype, Genotype, and Clinical Presentation Associated With Bovine Viral Diarrhea Virus (BVDV) Isolates From Cattle

The clinical manifestations that are associated with bovine viral diarrhea virus (BVDV) infection are diverse. In this retrospective analysis of 177 BVDV-positive samples from 1992−2000, we determined the distribution of genotype and biotype. In addition, we compared the relationship among biotype, genotype, clinical sign, and age of animal at time of BVDV isolation, where information was available. Of the 177 BVDV-positive samples, 30% contained cytopathic (CP) isolates and 70% contained non-cytopathic (NCP) isolates. Genotyping using a 5’UTR region-based polymerase chain reaction revealed that 63% were BVDV-1, 26% were BVDV-2, and 11% of the samples contained both BVDV-1 and BVDV-2. Distribution of genotype within each biotype was proportional to the overall Intern J Appl Res Vet Med • Vol. 3, No. 4, 2005 Intern J Appl Res Vet Med • Vol. 3, No. 4, 2005 320 infect cattle of all ages, with consequences of infection in immunocompetent cattle ranging from subclinical or mild disease to a highly fatal form. , 2 In addition, BVDV infection of susceptible pregnant cattle may result in fetal infection, with early embryonic death, abortion, or congenital malformations as possible outcomes, as well as the birth of calves immunotolerant to, and persistently infected (PI) with, BVDV. Not only are PI cattle the major source of virus transmission within and among cattle herds, but they are also at risk of developing mucosal disease (MD). Bovine viral diarrhea virus belongs to the genus P e s t i v i r u s in the family F l a v i v i r i d a e. Isolates of BVDV can be segregated into 2 biotypes, cytopathic (CP) and non-cytopathic (NCP), based on their effect in cultured cells. Based on their genomic differences, BVDV isolates can be separated into 2 distinct genotypes, BVDV-1 and B V D V 2 . Viruses of either genotype may exist as either biotype. The NCP isolates of BVDV-2 have been associated with outbreaks of severe clinical disease in the United States and Canada. These BVDV infections have demonstrated that NCP BVDV can cause severe disease with high mortality in all age groups. In addition, severe thrombocytopenia and a hemorrhagic syndrome also have been associated with infection with NCP BVDV-2. , 7 A l t h o u g h NCP BVDV-2 may be associated with severe clinical disease, BVDV-2 isolates also may induce subclinical or mild d i s e a s e . , 8 Distribution data of biotype and genotype with clinical presentation is very important not only in controlling and understanding BVDV disease, but also in directing the choices for antigens to be utilized in vaccine development. The purpose of this study was to assess distribution of biotype and genotype for 177 BVDV-positive bovine samples from Kansas. A further objective, reliant upon information availability, was to compare the relationship among biotype, genotype, clinical sign, and age of animal for these BVDV-positive