Ornithobacterium rhinotracheale (ORT) has been identified as one of the respiratory bacterial pathogens in turkey and chicken flocks. Four live birds displaying severe torticollis were submitted from a 13-week-old commercial broiler breeder chicken flock located in Mazandaran province. These birds were suspected to
pasteurellosis by the farm veterinarian. No other marked gross lesion except emaciation was seen. Histopathologic examination of the brains showed mild to moderate meningeal vasculitis, perivascular cuffing with lymphocytes, degeneration and necrosis of purkinje cells in the cerebellum. Viral culture of the brains
especially for Newcastle disease and avian influenza viruses was negative. Bacterial culture of the brains onto the blood agar revealed pure growth of Ornithobacterium rhinotracheale. In this study molecular confirmation of ORT by using of a very specific polymerase chain reaction (PCR) was carried out. Amplification products of a 784 bp region of the 16S rRNA gene of ORT confirmed the bacterium identification. This is the first field case of ORT isolation from the brain of commercial chickens in Iran. These data suggest that this bacterium should be considered in differential diagnosis in cases of avian nervous signs. Further studies are necessary to confirm if ORT is a primary pathogen in such cases.