Author
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Ridpath, Julia |
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Submitted to: Meeting Proceedings
Publication Type: Proceedings Publication Acceptance Date: 2/4/2010 Publication Date: 3/5/2010 Citation: Ridpath, J.F. 2010. BVDV: Detection, Risk Management and Control. Proceedings of Texas Veterinary Medical Association. p. 151-158. Interpretive Summary: Technical Abstract: The terms bovine viral diarrhea (BVD) and bovine viral diarrhea viruses (BVDV) are difficult to define in simple straightforward statements because both are umbrella terms covering a wide range of observations and entities. While diarrhea is in the name, BVD, it is used in reference to a number of clinical presentations, including respiratory, reproductive, and enteric disease with a severity of disease symptoms ranging from subclinical to severe. In addition, both acute and persistent infections are observed. Similarly, the term BVDV does not refer to just one viral entity, but to a group of viruses that may exist as one of two different biotypes and belong to two different species. Although bovine is in the name, these viruses also infect many species of both domestic and wild ruminants and pigs. In brief, BVDV refers to two distinct groups of viruses, BVDV1 and BVDV2, that are classified as two different species within the Pestivirus genus of the Flavivirus family. Acute infections may result in enteric, respiratory, and/or reproductive disease of varying severity, depending on the viral strain, the immune and reproductive status of the host, and the presence of secondary pathogens. Viruses from both species are further subclassified into cytopathic and noncytopathic biotypes based on their activity in cultured epithelial cells, with noncytopathic BVDV predominating in nature. Acute infections with BVDV are always accompanied by immune suppression 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 leaves infected animals vulnerable to secondary infections. In addition to acute infections, noncytopathic BVDV strains may establish life-long persistent infections. These persistent infections are the result of fetal exposure to BVDV before the development of the immune system. Persistently infected (PI) animals that become superinfected with cytopathic BVDV may develop mucosal disease (MD). The PI animal is thought to be the major vector for introduction of BVDV into herds. Thus most control programs in the U.S. are focused on the detection and removal of PI animals. The other goals of control programs are to increase herd resistance via vaccination and improve biosecurity to lessen the risk of exposure to BVDV. |
