EXPERIMENTAL-INFECTION OF LAMBS WITH BOVI NE RESPIRATORY SYNCYTIAL VIRUS - PATHOLOGICAL AND HEMATOLOGICAL STUDIES

An experimental model was designed to characterise the gross and micro scopic lung lesions observed in lambs inoculated with Bovine Respirato ry Syncytial Virus (BRSV). Thirty merino lambs of both sexes, with a l ive weight of 17 +/- 3 kg, received an intratracheal inoculation of 20 mi saline solution containing 1,26 x 10(6)TCIDS(50) BRSV (strain NMK- 7) per ml. Lambs were slaughtered 1, 3, 7, 11 and 15 days post-inocula tion and histopathological and morphometric studies were performed. Bl ood samples were also collected 0, 1, 3, 5, 7, 9, 11 and 15 days post- inoculation, and various haematological parameters were analysed. Resu lts reflected a series of lesions, the most noteworthy of which were b ronchiolitis obliterans with destruction of the mucociliary apparatus, the presence of syncytial cells in alveoli and a progressive intersti tial reaction. This reaction led to a reduction in the area of bronchi olar and alveolar lumina. Blood tests revealed normocytic and normochr omic anaemia, together with neutrophil leukocytosis up to day 7 p.i.