Comparative Evaluation of Bovine Tuberculosis Diagnostics: Integrating Post-Mortem Findings, Bacteriology, and Immunological Assays in Egyptian Cattle

Bovine tuberculosis (bTB), caused by Mycobacterium bovis, remains a major zoonotic and economic issue in livestock-producing countries, including Egypt. Despite its widespread use, the Single Intradermal Comparative Cervical Tuberculin (SICCT) test has limitations in sensitivity and specificity, necessitating the use of other diagnostic tests. The study investigated several diagnostic techniques for tuberculosis in cattle, including postmortem examination, bacteriological culture, ELISA, lateral flow assay, γ-interferon (γ-IFN) testing, and Single Intradermal Comparative Cervical Tuberculin (SICCT). The SICCT test was used to screen 2,400 Holstein cattle from eight organized dairy farms at Alexandria-Cairo desert road, Borg El Arab area, El Khatatba, Tanta, and Ismaelia, with 50 (2.10%) identified as reactors. These animals had PM examinations, and the distribution of lesions throughout organ systems was documented. Tissue samples were cultured for M. bovis and MOTT (mycobacteria other than tuberculosis). Blood and serum samples were examined using γ-IFN, ELISA, and lateral flow assays. Sensitivity/specificity analysis and chi-square testing were used to evaluate diagnostic accuracy. Important results showed that 72% of reactors had visual lesions (VL), of which 36% were in the respiratory organs, and 28% had non-visible lesions (NVLs). 62% of animals (56% VL, 6% NVL) had M. bovis, according to bacteriological analysis, with 6% also having mycobacteria other than tuberculosis (MOTT). Visible lesions had higher ELISA and lateral flow test results (40% and 34%, respectively) than non-visual lesions (2% each). In contrast to SICCT (86% sensitivity, 92.50% specificity), the γ-IFN assay demonstrated a greater sensitivity (93.40%) but a lower specificity (84%). The results demonstrate the limitations of depending solely on the SICCT test and the significance of integrating other diagnostic methods for a successful bTB diagnosis. This multi-modal approach facilitates better disease control and public health interventions while also increasing the effectiveness of surveillance.