Tuberculosis in bovine slaughtered in the semi-arid region of Rio Grande do Norte, Brazil

Abstract

Between November 2017 and August 2018, in order to determine the occurrence of tuberculosis in cattle slaughtered in the semi-arid region of Rio Grande do Norte, 11,610 bovine carcasses underwent a routine post-mortem inspection. One animal presented suggestive lesions and samples from lung, spleen and heart were submitted to microbiological culture in Stonebrink medium for 90 days and molecular analysis by nested-PCR. For histopathological examination and Ziehl Neelsen staining, the omentum was used. In the cultured samples, two of them (heart and spleen) showed growth, but were not confirmed as M. bovis by conventional PCR. At nested-PCR, the samples showed amplification for the TbD1 region. The presence of numerous granulomas was detected in the histopathological examination characterized by a necrotic center and areas of mineralization, as well as the presence of acid-fast bacilli (AFB) in the Ziehl-Neelsen stain. Microbiological culture can show false negative results, despite being considered a gold standard technique, although it takes time. Nested-PCR and histopathology show fast and effective results for the diagnosis of the disease. The presence of positive animals represents a public health risk in the studied region. Therefore, one of the essential systems applied to the control of bovine tuberculosis is the epidemiological surveillance of animals in slaughterhouses.