The practical consequences of immunosuppressive effect of BVD virus

Summary Background: Bovine viral diarrhoea virus (BVDV) is an important endemic infection worldwide. Acute infections with BVDV, a major pathogen of cattle, are often asymptomatic or produce only mild clinical symptoms. The BVDV causes several clinical signs but these are changed by other infectious agents which can colonize and proliferate due to immunosuppressive effect of BVDV. Objectives: In that study the authors summarize the pathogens associated with BVDV. Although the direct economic losses caused by this virus have not been well quantified, the role it plays as an immunosuppressive agent and as a potentiater for other diseases, most notably bovine respiratory disease, have been well documented. Material and Methods: The etiological role of BVDV is known in the Bovine respiratory disease complex. BVDV has synergistic effect on many viral and bacterial pathogens that cause respiratory illnesses: Bovine respiratory syncytial virus, Parainfluenza virus-3, Pasteurella multocida, Mycoplasma bovis, M. arginini, M. bovirhinis, M. bovigenitalium, Histophilus somni and Mannheimia haemolytica. The most often occurring mixed infections with BVDV in the digestive system are salmonellosis and rotavirus infection. The synergistic effect of BVDV also proved in mixed infection with Neospora caninum, Anaplasma marginale, Bovine herpesvirus-1, Bovine herpesvirus-5, Bovine leukaemia virus and Bovine immunodeficiency virus which cause the illness of reproductive system and other organs. Results and Discussion: Results of the coinfection are that the clinical signs are more serious, the efficiency of treatment is decreased and the economic losses further increases. Although occasionally the primary pathogen, BVDv’s impact on cattle health is through the immunosuppressive effects of the virus and its synergism with other pathogens