This paper presents the first isolation of bovine respiratory syncytial virus in Brazil and its physicochemical, morphological and molecular characterization. The virus was isolated from 33 samples of nasotracheal secretions, successively inoculated into a Madin-Darby bovine kidney cell culture, which was characterized by physicochemical tests and morphological observation by electron microscopy. The Brazilian sample is an RNA pleomorphic, enveloped, thermolabile and nonhemagglutinating spicular virus. Reverse transcription, followed by nested polymerase chain reaction (nRT-PCR) assay was carried out using oligonucleotides B1, B2A, B3 and B4 for the fusion proteins (F) and B5A, B6A, B7A and B8 for the attachment protein (G). The nRT-PCR-F amplified a fragment of 481 bp corresponding to part of the gene that codes for protein F, whereas nRT-PCR-G amplified a fragment of 371 bp, in agreement with part of the G gene. The virus isolated from Brazilian samples in this study corresponded to the bovine respiratory syncytial virus, and RT-PCR proved to be useful for the diagnosis of bovine clinical samples.
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-FIG 1: Alignment of nucleotide sequences residues 316 to 614 of the G gene of bovine respiratory syncytial virus (BRSV) strain BRSV-25-BR and 15 other representative strains of BRSV from subgroups A (375.1, 85-1330, Dorset, Snook), AB (NMK7, 220-69, Lelystad, MVR553) and B (BRSV-108-BR, BovX, 220-60, 127, 4642), the untyped strain WBH and one sequence derived from an ovine isolate of RSV (ORSV). The GenBank database accession numbers are shown, together with the origin and year of isolation of each strain.BOVINE respiratory syncytial virus (BRSV) is the most important cause of lower respiratory tract infections in calves and is an economically important pathogen of cattle (Bryson and others 1991). BRSV infections have increased with the intensification of cattle farming, and in many countries the virus is considered to be a major problem in calf rearing (Lekeux 1995). Little is known about the significance of BRSV infections and the virus strain profiles in Brazil. Serological investigations of cattle on 65 farms in southern Brazil have shown a seroprevalence of 75 per cent (Campalans and Arns 1997). In addition, more than 95 per cent of the lungs of cattle up to three years old, with or without respiratory signs, obtained from slaughterhouses in Brazil were positive in an immunofluorescent test, with 70 per cent of the calves being infected within the first year of life (Gonçalves and others 1993). The mortality rate for confirmed acute infections is 5 to 20 per Veterinary Record (2006) 158, 632-...
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