A study to evaluate the distribution of granulomatous lesions in the lymph nodes of swine carcasses was accomplished. The main objective was to compare the methods of isolation of mycobacteria of the Mycobacterium avium Complex (MAC), Ziehl-Neelsen (ZN) staining, histopathological examination and immunohistochemistry (IHC) for the diagnosis of granulomatous lymphadenitis caused by MAC. A total of 431 samples of lymph nodes from 394 swine carcasses kept in 12 cold storage rooms of southern Brazil, which had the Service of Federal Inspection (SFI), were analyzed. Lymph nodes with granulomatous lesions were submitted to histological examination, ZN staining and IHC with monoclonal antibody produced with cellular extract of M. avium. The agreement between the exams was measured by the Kappa test at a 95% confidence level. The macrocospic examination done by SFI correctly identified 90.3% of granulomatous lesions, when compared with histological examination, and the majority of carcasses (92.5%) showed the lesions only in lymph nodes of the alimentary chain. Histological examination confirmed the presence of granulomatous lesions in 90.3% of the lymph nodes. The agreements between histological examination, ZN staining (Kappa: 0.342), IHC and the isolation of MAC (Kappa: 0.102) were low, however high between IHC and histology with typical presence of granulomas in the lymph nodes (Kappa: 0.973). IHC together with histological examination revealed to be efficient for identification of the granulomatous lymphadenitis caused by MAC.
Swine; granulomatous lymphadenitis; Mycobacterium avium; immunohistochemistry
