One-step RT-PCR and nested PCR were used to detect bovine respiratory syncytial virus (BRSV) in infected cell cultures. Specific 984 bp and 383 bp products, selected from gene encoding the F protein using suitable primers, were amplified and, if appropriate, reamplified. The method was further used for examination of nasal swabs and blood samples collected from animals showing signs of a respiratory disease. Lactating cows and 6-8-month-old bulls from two herds were investigated.The infection by BRSV was confirmed by a) demonstration of specific fragments of BRSV genome in all animals showing signs of an acute disease, and b) indirectly by serological methods in convalescent animals.Viral RNA was detected from nasal swabs and leukocytes of affected animals. The positive PCR product obtained by nested RT-PCR from RNA isolated from leukocytes was sequenced and nucleotide and amino acid homology were 97-100% and 94.5-100% respectively, when compared with sequences from the GenBank.Considering the difficulties associated with the demonstration of BRSV in cell cultures, the amplification techniques provide an effective tool for the identification of the causative agent of bovine respiratory diseases.
Nested PCR; BRSV, F protein; diagnosticsBovine respiratory syncytial virus is a pneumovirus of the family Paramyxoviridae causing an acute respiratory disease in cattle. BRSV mostly attacks calves, in which the infection is manifested by pyrexia, anorexia, increased respiratory rate, and dyspnoea. Infections in lactating cows, accompanied by considerable decrease in milk yield by up to 60%, have also been described (Elvander 1996;Pritchard et al. 1997). Morbidity is high and death rate can reach up to 20% (Kovafiãík 1997). BRSV is regarded as the major causative agent of the bovine respiratory syndrome in West European states and the USA. The agent was also demonstrated in the local cattle herds (Pospí‰il et al. 1978; Kovafiãík 1999), but its prevalence in the Czech Republic has not yet been studied.The diagnosis is based on virus demonstration in cell cultures and serological methods for the demonstration of viral antigen and seroconversion. The methods used most frequently for antigen demonstration include the immunofluorescence test and the enzymatic immunosorbent assay (EIA) (Kimman et al. 1986;Krilov et al. 1988;Valarcher et al. 1999). Virus isolation is complicated by a high sensitivity of the agent and the fact that several passages are necessary before CPE develops. Tests on two blood samples collected at three-week intervals are necessary for the demonstration of seroconversion. Moreover, the interpretation of results is impeded by interaction with maternal antibodies present in blood sera of calves. Therefore, the serological methods are used mostly for the demonstration of past infections.