cent (Campalans and Arns 1997). BRSV was isolated for the first time in Brazil in 1996, from nasotracheal secretions of calves with respiratory disease in the south of the country (Arns and others 2003). This short communication describes the characterisation of a new strain of BRSV in Brazil isolated from a one-year-old calf with severe respiratory signs. The calf showed anorexia, apathy, fever, an abundant seromucous nasal discharge, intense dyspnoea, tracheal and pulmonary sounds, and pain in the ventral thoracic region. Despite supportive treatment, the animal did not recover and was euthanased five days after the onset of clinical signs. Postmortem examination revealed interstitial multifocal pneumonia, extensive consolidated areas, severe interstitial and subpleural emphysema, intense thickening of the interlobular walls, non-catarrhal pleuritis and marked hypertrophy of the right ventricle. For immunohistochemistry (IHC) analysis, samples of lung tissue were fixed in 4 per cent paraformaldehyde (SigmaAldrich), embedded in paraffin wax, cut in 4 μm thick sections and mounted on microscope slides. The IHC was carried out at the Royal Veterinary and Agricultural University, Copenhagen, Denmark. After a pretreatment with 0·018 per cent protease, the sections were blocked with 5 per cent normal pig serum, and then incubated overnight at 4°C with a biotinylated polyclonal bovine serum against BRSV. The sections were then incubated with 0·9 per cent streptavidin (Dako), followed by 0·9 per cent biotinylated alkaline phos-