¹DVM Graduated of Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz, Ahvaz, IRAN
²Department of Pathobiology, Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz, Ahvaz, IRAN DOI : 10.9775/kvfd.2016.15679 Mannheimia haemolytica infection is one of the most common etiologic agents of sheep pneumonia almost all over the world. Ovine pneumonic Mannheimiosis is characterized by severe fibrinous pleuropneumonia. Subacute to chronic cases progress to purulent bronchopneumonia and its squeals include abscessation and fibrous pleural adhesions. In the present study, lungs of 8986 sheep were inspected grossly in the Ahvaz abattoir and totally 65 lungs with visible signs of bronchopneumonia were selected for pathological and bacteriological examinations. Mannheimia haemolytica antigens were detected in 63.07% of immunoperoxidase stained tissue sections while 52.30% of the lungs were positive in bacteriological culture. Suppurative, necrotic and fibrinous types of bronchopneumonia were the most abundant lesions and right cranial lobes, specifically their cranial portions, were the most affected areas. McNemar test showed a significant difference between the diagnostic power of immunohistochemistry (IHC) and bacterial culture in detection of M. haemolytica (κ=0.66). Considering IHC as a golden test, sensitivity and specificity of bacterial culture were estimated as 78.05 and 91.67%, respectively. Chi- squared test showed significant correlations between the distribution of the lesions and bacterial isolation (P=0.04), types of lesions and IHC results (P=0.01), and also types of bronchopneumonia and mixed/pure isolation (P=0.008). This study showed the significant role of Mannheimia haemolytica in causing pneumonic lesions of studied sheep. Keywords : Immunohistochemistry, Mannheimia haemolytica, Sheep, Lung, Bacteriology