EXPERIMENTAL BOVINE RESPIRATORY SYNCYTIAL VIRUS-INFECTION IN LAMBS - ULTRASTRUCTURAL-STUDY OF LUNG

An experimental model was designed to characterize ultrastructural lesions in the lung of lambs inoculated with Bovine Respiratory Syncytial Virus (BRSV). 30 Merino lambs of both sexes, with a live weight of 17 +/- 3 kg, received an intratracheal inoculation of 20 ml saline solution containing 1,26 x 10(6) TCID50 BRSV (strain NMK-7) per ml. Lambs were slaughtered 1, 3, 7, 11 and 15 days post inoculation, and samples were taken for analysis using scanning and transmission electron microscopy. Results reflected the action of the virus on airway epithelia, giving rise to changes in the mucociliar apparatus and a modification of respiratory tract defense mechanisme, rendering the lung parenchyma susceptible to opportunist bacterial infection. SEM analysis revealed a narrowing of respiratory lumina and a considerable interstitial reaction which lasted until 11 d.p.i. Evidence of repair was observed by 15 d.p.i.