| Bovine respiratory syndrome is often caused by a mixture of multiple pathogens, with a complex pathogenic mechanism. This study report the outbreak of this disease in calves on a beef cattle farm in Kunming City, which was mainly manifested by respiratory symptoms such as cough, shortness of breath, runny nose and diarrhea, and subsequently died successively. Field investigation and clinical examination showed that it was suspicious infection of respiratory pathogens. In order to confirm the specific cause of the disease, nose swabs were collected from the infected cattle, and pathological autopsy was performed on the dead cattle. The pathological changes were mainly tracheal, bronchial, gastric mucosa, small intestine hemorrhage, pulmonary liver change, liver hemorrhage and enlargement, cardiac hemorrhage, pericardium adhesion, etc. The tissue samples of died case were collected for laboratory testing. And PCR detection kit for eight common respiratory pathogen (bovine viral diarrhea virus, bovine coronavirus, bovine parainfluenza virus type 3, bovine respiratory syncytial virus, Bovine herpesvirus type 1, Pasteurella multocida, Mantella hemolyticus, mycoplasma bovis) were using. Detection results shows the outbreak were caused by mixed infection of parainfluenza virus type 3, Pasteurella multocida and mycoplasma bovis. After treatment with macrolides such as gamamycin, 10% temicosin and 20% flufenicol, combined with intensive feeding management, most of sick cattle recovered. |