The correlation between M. bovis isolation and ELISA using PPD-B and ESAT6-CFP10 mixture on the sera of tuberculin reactor cattle and buffaloes

In this study, 6150 animals (3600 dairy cattle and 2550 buffaloes) in different Egyptian governorates were tested by single intradermal cervical tuberculin test using purified protein derivatives - bovine type (PPD-B), 72 cattle (2%) and 26 buffaloes (1 %) reacted positively. The postmortem examination of the positive reactors revealed 49 (68.1%) out of 72 slaughtered cattle with visible lesions (VL) while the other 23 (31.9%) reactors showed no visible lesions (NVL); comparing with 17 (65.4%) out of 26 slaughtered buffaloes with VL while the other 9 (34.6%) reactors showed NVL. The bacteriological examination of processed samples from the 72 slaughtered cattle revealed 44 Mycobacterium bovis (61.1%); 40 (81.6%) were from 49 VL and 4 (17.4%) were from 23 NVL, compared to 15 (57.7%) Mycobacterium isolates from buffaloes; 10(38.5%) were M. bovis, all were from the 17 VL (58.8%). and 5 isolates (19.2%) were Mycobacterium other than tuberculosis (MOTT), 3 (17.6%) were from the 17 VL and 2 (22.2%) were from the 9 NVL. The ESAT6-CFP10 mixture using ELISA of the tuberculin positive animals sera showed VL could detect 83.7% and 70.6% in cattle and buffaloes, respectively; compared to 89.8% and 76.5% in cattle and buffaloes, respectively using PPD-B. On the other hand, the sera collected from tuberculin positive animals with NVL, the antigen mixture revealed 17.4% and 22.2% in cattle and buffaloes, respectively, using the ESAT6-CFP10 mixture; compared to 21.7% in cattle and 33.3% in buffaloes using the PPD-B antigen. The PCR assay using oligonucleotide primer that amplifies a 350 bp fragment in RD7 region of M. bovis confirmed the cultural and biochemical identification of M. bovis isolates (PCR-positive) and MOTT (PCR-negative).