Co-infection of Ornithobacterium rhinotracheale with Streptococcus zooepidemicus in Chickens

An outbreak of bronchial embolization with 50%-70% morbidity and 30% mortality occurred in broilers in northeast China. This highly contagious disease is characterized by the sudden onset of clinical symptoms, including dyspnea, hemorrhagic tracheal discharge, and bronchial obstruction. Subsequently, six strains of Ornithobacterium rhinotracheale (ORT) and three strains of Streptococcus zooepidemicus were isolated from the various organs and identified using biochemical tests and PCR methods. The pathogenesis of embolization in chickens is poorly understood. The current experimental study confirmed that ORT infection alone could induce a significantly fatal hemorrhagic pneumonia and high mortality in comparison with S. zooepidemicus infection. Moreover, co-infection of ORT with S. zooepidemicus could induce even higher mortality, with severe bronchial obstruction, than that observed in chickens infected with S. zooepidemicus or ORT alone. Therefore, the combination of ORT and S. zooepidemicus may be associated with the outbreak of chicken bronchial embolization. Further investigation of the pathogenesis of ORT and Streptococcus is urgently needed.