Submitted to: American Association of Bovine Practitioners Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/22/2005
Publication Date: 9/22/2005
Citation: Chase, C.L., Braun, L.J., Holler, L., Neill, J.D., Ridpath, J.F. 2005. Characterization of bovine viral diarrhea virus (BVDV) genetics and levels from a group of BVDV persistently infected calves. In: Proceedings of the 38th Annual Convention of the American Association of Bovine Practitioners, September 22-24, 2005, Salt Lake City, Utah. p. 207-208. Interpretive Summary:
Technical Abstract: Bovine viral diarrhea virus (BVDV) infections cause major problems in the US cattle industry. BVDV persistent infections are the result of fetal infections in the first and second trimesters of pregnancy. Persistently infected animals are a major reservoir of the virus in nature and are extremely efficient at spreading the virus among cattle populations. Understanding the nature of persistent infections and developing diagnostics and surveillance schemes that eliminate PI animals is vital to the control of BVDV. In this study we look at variations in clinical presentation, viral spread, immune response and viral stability in a large group of calves infected with the same BVDV strain. One hundred twenty-eight bred cows were obtained from a private ranch and moved to a university field station. The vaccination history of the herd indicated that a BVDV type 1 vaccine had been used. Following weaning the calves were screened in September 2004 and 44 were found to be immunohistochemistry positive for BVDV antigen. PCR analysis indicated that the animals were infected with a BVDV type 2a isolate. Five of these animals died prior to being moved to a university research facility. Three months later in December 2004, the remaining 39 calves were tested via PCR and IHC and 36 of the 39 were positive for BVDV by both tests. Sequence comparison of the 5’UTR of the 36 isolates showed a >99% sequence homology. Comparison of the highly variable region coding for the E2 polypeptide showed a greated than 96% sequence conservation among strains. Three of the PI animals had titers against BVDV. Studies are ongoing to see if the presence of titers will affect viral sequence over time. Viral titers are being assessed. The animals are being tested monthly for viral and antibody titers. Additional lymphocyte marker and neutrophil studies are also ongoing. This study indicates that 3 of the animals initially thought to be persistent were acutely infected and IHC positive. These PI animals provide an excellent opportunity to monitor virus evolution and immune response in animals infected with the same isolate.