Role of bovine respiratory syncytial virus in etiology of respiratory diseases on milk farms

Abstract

Bovine respiratory syncytial virus (BRSV) is one of the etiological agents of respiratory diseases. The agent spreads widely in all the countries with intensive livestock farming and can cause pathologic changes in respiratory system either alone or in combination with other viruses and bacteria. It is a matter of crucial importance to study spread of the agent on large milk farms, to detect it in the internal organs of infected animals, and to quantify virus accumulation in them. The purpose of the research was to study peculiarities of RS infection spread, frequency of the virus detection in biomaterial samples (both alone and in associations with infectious bovine rhinotracheitis (IBR) and bovine viral diarrhea/mucosal disease viruses (BVDV) and with Pasteurellaceae bacteria) on large milk farms affected by respiratory animal diseases; and to determine virus concentration in the respiratory organs. BRSV alone was reported in 9.2% of the tested biomaterial samples, as associated with IBR and BVDV it was reported in 1.4% and 5.2% of samples, correspondingly. The number of samples containing simultaneously BRSV and Pasteurellaceae bacteria was 10.8%. The virus was reported in a maximum of 26.6% of the tested samples. With the help of real-time PCR the virus genome was detected in lungs (13.1%), in exudate from trachea, bronchi and nasal sinuses (6.0%), in nasal discharge (4.0%) and in bronchi (1.7%). The virus was seldom detected in trachea and bronchial mucosa (1.1%) and in pulmonary lymph nodes (0.8%). Quantification of BRSV RNA demonstrated that maximum virus accumulation was observed in lungs and nasal charges and it confirms data on its tropism to pulmonary interstitium.