Abstract
Tuberculosis-like lesions (TBL) in pigs have been associated with microorganisms other than mycobacteria. In this work a histopathological and microbiological evaluation of TBL in pigs is shown. A total of 352 samples belonging to 171 pigs totally condemned at slaughterhouse due to generalized TBL were sampled and selected for analysis. Pyogranulomatous (56.2%) and granulomatous lesions (20.2%) were observed in all analysed organs. Most of the granulomas observed in both lymph nodes and lungs belonged to more advanced stages of development (stages III and IV) whereas in the liver and the spleen most of lesions belonged to intermediate stages (stages II and III). Different microorganisms were simultaneously detected from TBL in the 42.7% of the animals. Mycobacterium tuberculosis complex (MTC) (38%), coryneform bacteria (40.3%) and streptococci (28.1%) were the main groups of microorganisms detected after bacteriological analysis, with Trueperella pyogenes and Streptococcus suis as the most frequently isolated species. Mycobacteria belonging to MTC were the most frequently detected pathogens in granulomatous and pyogranulomatous lesions in submandibular lymph nodes (32.7%) and coryneform bacteria were the microorganisms more frequently isolated from lungs (25.9%) and spleen samples (37.2%). These results may provide new insights into the pathogenesis and diagnosis of this pathology. The importance of coryneform bacteria and streptococci in such processes must be evaluated in future studies.
Highlights
Tuberculosis-like lesions (TBL) can be an important cause of condemnation in swine at abattoir inspection representing significant important economic losses [1]
Mycobacterium avium complex (MAC), Mycobacterium tuberculosis complex (MTC) and Rhodococcus equi have been reported as the species most frequently associated with TBL, and these infections typically result in indistinguishable gross lesions in pigs [5, 9, 10, 11, 12, 13]
Necrotic foci or lesions showing intense mineralization and fibrosis, with absence of epithelioid cells or MNGCs (13/352; 3.7%) were separately considered as these lesions could not clearly be classified as either pyogranulomas or granulomas. Other lesions such as interstitial pneumonia, catarrhal-purulent bronchitis, periportal fibrosis, periesplenitis and interstitial and multifocal hepatitis were detected in the absence of granulomatous or pyogranulomatous lesions (71/ 352, 20.2% samples; and 1/171, 0.6% animals)
Summary
Tuberculosis-like lesions (TBL) can be an important cause of condemnation in swine at abattoir inspection representing significant important economic losses [1]. Mycobacterium avium complex (MAC), Mycobacterium tuberculosis complex (MTC) and Rhodococcus equi have been reported as the species most frequently associated with TBL, and these infections typically result in indistinguishable gross lesions in pigs [5, 9, 10, 11, 12, 13]. Other genera such as Corynebacterium spp., Streptococcus spp. or Staphylococcus spp., have been isolated in caseous lymphadenitis in pigs, highlighting the potential diversity of pathogens that might be associated with TBL in this species [1, 14, 15]. Results of this study can help to better understand the interaction among microorganisms in pigs affected by TBL to improve the knowledge on the pathogenesis and diagnosis of this pathology
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