Accuracy of inspection surveillance in detecting bovine tuberculosis during slaughter in Rio Grande do Sul

Bovine tuberculosis (bTB) is a zoonosis whose main reservoir and source of infection is cattle. Continuous efforts for disease effective control and eradication are made worldwide, including the identification of bTB-suggestive lesions in slaughtered animals. Since granulomatous lesions could have different causes, laboratory diagnosis is important to confirm the disease etiology. The aim of this study was to evaluate the accuracy of the macroscopic bTB diagnosis during abattoir inspection compared to laboratory confirmation, and to identify macroscopic lesions characteristics associated with tuberculosis. A total of 163 tissue samples were collected in slaughterhouses from Rio Grande do Sul, South Brazil, of which 38 were classified as bTB-suggestive. Among these, 31 were confirmed as bTB-positive by laboratory diagnosis based on PCR, histopathology, and bacterial isolation, resulting in abattoir surveillance sensitivity of 93.9%, specificity of 94.7%, positive predictive value of 81.6%, negative predictive value of 98.4%, agreement of 94.51% and Kappa value of 0.84. The results indicate that abattoir surveillance in the evaluated slaughterhouses is effective in preventing bTB-positive carcasses from reaching the consumers. Significant associations of bTB diagnosis and a higher number of affected organs, pulmonary location and pasty lesion consistency were identified in univariable analyses, with the number of affected organs emerging as a significant risk factor. These characteristics can serve as useful indicators to support more targeted and efficient post-mortem inspection procedures, such as training meat inspectors to recognize and prioritize carcasses displaying them for further diagnostic testing or detailed examination.