Abstract: This experiment was to identify the pathogen of calves which was suspected of infecting bovine respiratory syncytial virus and Pasteurella mutocida simultaneously. Conventional test of virus and bacterium, PCR methods were all used to identify viral and bacterial respectively. The results indicated that the virus could grow well, propagate and induce typical cytopathic effect with syncytium form ation in BT cells. The isolate could not agglutinate and adsorb erythrocytes of human, some animals and chicken. The virus could be neutralized by bovine respiratory syncytial virus (BRSV) standard positive serum. The RNA extracted from the cell culture of the isolated virus was subjected to RT-PCR analysis. According to the colony morphology, bacterial staining characteristics and biochemical characteristics, the isolated bacterium was Pasteurella multocida. The calves were infected by bovine respiratory syncytial virus and Pasteurella mutocida simultaneously.

Key words: bovine respiratory syncytial virus; Pasteurella multocida; mixed infection