Field-Oriented Assessment of Bovine Tuberculosis in Tunisian Cattle: IDR, PCR Mpb70 and serological Test prediction based on AI approaches

Bovine tuberculosis (bTB), caused by Mycobacterium bovis ( M. bovis ), remains a major zoonotic and economically burdensome disease worldwide. In Tunisia, where bTB has remained present for many years, eradication efforts have been hampered by diagnostic limitations and resource constraints. While the tuberculin Intra Dermal Reaction test (IDR), also known as Tuberculin Skin Test (TST), remains the cornerstone of surveillance, its limited sensitivity and specificity highlight the need for improved diagnostic strategies. This study evaluated the diagnostic performance of IDR, PCR _Mpb70 and three serological rapid tests: Quickvet Ab® (Ac1, detecting antibodies against a recombinant M.bovis antigen), Vetdiagnostix Ab® (Ac2, detecting antibodies against a recombinant MPB70/MPB83 fusion protein), and Vetdiagnostix Ag® (Monoclonal antibodies against Bovine IFN-γ detecting a native M. bovis antigen complex) in Tunisian cattle (n = 32). Based on AI, Bayesian Latent Class Model (BLCM) analysis, PCR _Mpb70 was identified as the most reliable reference standard due to its high sensitivity (Se) and perfect specificity (Sp) when assessed alongside other tests. Using PCR _Mpb70 as a proxy gold standard, supervised machine learning via Random Forest algorithm was employed to assess the predictive performance of the individual and combined diagnostic tests. As a main result, a high bTB prevalence (46.37%) was confirmed in the tested animals, although prevalence estimates varied considerably depending on the diagnostic used test (average ± 9.76). The combinations IDR2/Ac2, IDR2/Ag, and IDR2/Ac2/Ag, corresponding to the application of the second IntraDermal test (IDR2) alongside antibody detection via Immunochromatographic assays targeting the Ac2 antigen, the Ag antigen, or both, emerged as the most informative and complementary alternatives to PCR. These approaches provide practical and effective diagnostic options for field settings where access to molecular testing is limited or unavailable.