The Efficacy of Combining Intradermal Tuberculin Test (ITT), Enzyme-linked Immunosorbent Assay and Comparative Test on Detecting Infected Cattles of ITT-positive Dairy Herds

• Main Authors: Cheng-Mao Chen, 陳振茂
• Other Authors: Yeong-Huey Wu
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/20321554515047316482

碩士 === 國立屏東科技大學 === 獸醫學系所 === 101 === One of the cause to eradicate the tuberculosis ( TB ) with difficulty in the infected dairy herds in Taiwan was considered that the sensitivity of intradermal tuberculin test ( ITT ) is not enough. Therefore, combining the ITT with other diagnostic methods to improve the detecting rate was suggested. The aims of this study are to evaluate the efficacy of combining ITT with enzyme-linked immunosorbent assay ( ELISA ) or rapid test ( RT ) on effectively detecting the TB-infected dairy cattles, and the ability of comparative intradermal tuberculin test ( CITT ) for accurately identifing the ‘true’ bovine tuberculosis-infected herds. A total of 248 cattles from ITT-positive farms, including 11 of ITT- positive and ELISA- positive, 218 of ITT- positive but ELISA- negative, 13 of ITT-negative but ELISA-positive and 6 of ITT-negative and ELISA-negative cattles, were performed with the ITT, ELISA ( and / or RT ), gross lesion examinations of retropharyngeal and mediastinal lymph nodes and lung in the necropsy, and Mycobacterium bovis ( M. bovis ) isolation of the lymph nodes and lung lesions. If using the results of gross lesion as the diagnostic standard, the results showed that the highest coincidence is RT ( 77.0%, 94/122 ), followed by ELISA ( 70.2%, 165/235 ), and ITT ( 31.4%, 77/245 ) in the single diagnostic tests, and ITT+ELISA ( 25.9%, 56/216 ) and ITT+RT ( 24.4%, 40/164 ) in the combination of the two diagnostic tests. The highest sensitivity is ITT ( 86.8%, 53/61 ), follow by RT ( 45.0%, 9/20 ), and ELISA ( 13.3%, 8/60 ) in the single diagnostic tests, and ITT+ELISA ( 98.1%, 54/55 ) and ITT+RT ( 94.5%, 35/37 ) in the combination of the two diagnostic tests. The highest specificity is ELISA ( 89.6%, 156/174 ), followed by RT ( 83.1%, 84/101 ), and ITT ( 12.5%, 23/183 ) in the single diagnostic tests, and ITT+ELISA ( 1.9%, 3/157 ) and ITT+RT ( 3.1%, 4/126 ) in the combination of the two diagnostic tests. On the other hand, if using the results of M. bovis isolation as the diagnostic standard, the highest coincidence is also RT ( 80.5%, 91/113 ), followed by ELISA ( 73.3%, 129/176 ), and ITT ( 25.3%, 45/178 ) in the single diagnostic tests, and ITT+ELISA ( 12.8%, 14/109 ) and ITT+RT ( 8.5%, 8/94 ) in the combination of the two diagnostic tests. The highest sensitivity is also ITT ( 87.8%, 36/41 ), follow by RT ( 50.0%, 7/14 ), and ELISA ( 14.6%, 6/41 ) in the single diagnostic tests, and ITT+ELISA ( 100%, 13/13 ) and ITT+RT ( 100%, 7/7 ) in the combination of the two diagnostic tests. The highest specificity is also ELISA ( 90.2%, 121/134 ), followed by RT ( 84.6%, 83/98 ), and ITT ( 8.8%, 12/136 ) in the single diagnostic tests, and ITT+ELISA ( 1.0%, 1/94 ) and ITT+RT ( 1.1%, 1/185 ) in the combination of the two diagnostic tests. According above results, the coincidence of the humoral immunity tests ( ELISA and RT ) is significantly ( P&;lt;0.05 ) better than the cell-mediated immunity test ( ITT ), and the sensitivity of the cell-mediated immunity test ( ITT ) is significantly ( P&;lt;0.05 ) better than the humoral immunity tests ( ELISA and RT ), whether using the results of gross lesion or isolation as the diagnostic standard. The results indicated that the majority of these ITT-positive cattles were in the early stages of TB infection. Combining two of antemortem diagnostic tests could significantly increase the sensitivity to 100% ( P&;lt;0.05 ). On the results of the CITT test, a total of 151 cattles included 145 ITT- positive and 6 ITT-negative reactors from 18 ITT-positive dairy farms were conducted the cervical CITT test within 10 days of the initial caudal-fold tuberculin test ( ITT ). The results showed that CITT couldn’t completely certified the ITT-positive reactors whether to have gross lesion and/or M. bovis infection ( isolation-positive ), but can confirmed the CITT-negative reactors to haven’t gross lesion and/or M. bovis infection ( isolation-negative ). On the other hand, 10 times of CITT in the 10 farms randomly selected from above 18 ITT-positive dairy farms, a total of 67 cattles were analysed. The results showed that CITT-positive reactors were commonly found in each farm, and the ratio of the CITT-suspected reactors ( 43.3%，29/67 ) is significantly ( P&;lt;0.05 ) higher than CITT-negative reactors ( 23.9%，16/67 ). Besides, a total of 27 cattles from 8 initial ITT-positive dairy farms, which no cattle with gross lesion and M. bovis isolation was found, were analysed. The results showed that no CITT-positive reactors was found, and the ratio of the CITT-negative reactors ( 66.7%，18/27 ) was significantly higher than CITT-suspected reactors ( 33.3%，9/27 ) ( P&;lt;0.05 ). According to the above results, we presumed the ITT-positive reactor isn’t the M. bovis infection, and maybe the infection of nontuberculous mycobacteria. Key words：bovine tuberculosis, intradermal tuberculin test, enzyme-linked immunosorbent assay for bovine tuberculosis, rapid test for bovine tuberculosis, comparative intradermal tuberculin test