Molecular characterization and phylogenetic analysis of bovine viral diarrhea virus in dairy herds of Fars province, Iran

Bovine viral diarrhea virus (BVDV) is one of the most important viral pathogens of cattle worldwide. The aim of present study was to determine the molecular characterization and phylogenetic analysis of BVDV infection in dairy herds of Fars province, Iran. For initial screening, a total of 400 blood samples were collected from 12 industrial dairy herds with previous history of diarrhea, abortion or birth of weak calves and analyzed using reverse transcription-polymerase chain reaction (RT-PCR) on buffy coat. In the next step, blood samples and also ear notch biopsies were collected from 100 cattle of infected farms three weeks later which were subsequently tested by antigen capture ELISA (ACE), RT-PCR and immunohistochemistry (IHC). The results of nested RT-PCR were successful in 16 out of 400 buffy coat samples (4%) in the initial screening. Also, 8 out of 100 samples (8%) were positive by all practiced tests including RT-PCR, ACE and IHC on buffy coat, serum and skin samples, respectively. Immunoreactivity for bovine BVDV antigen as brown, coarsely to finely granular was observed within the cytoplasm of epidermic epithelial cells, hair follicles and subcutaneous stromal cells. Genetic sequence analyses showed both genotypes, BVDV-1 and BVDV-2. The new isolates were identified as BVDV1-FarsA, BVDV1-FarsB and BVDV2-FarsA in the phylogenetic tree. Since both genotypes of the virus are present in the region, our findings emphasize the importance of monitoring BVDV infection in cattle and suggest detection and elimination of PI animals for controlling and eradication of BVDV in Fars province.