Evaluation on the eradication mode of tuberculosis in infected dairy herds

• Main Authors: Chuen-Huei Shiau, 蕭春輝
• Other Authors: Yeong-Huey Wu
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/02940897046838029758

碩士 === 國立屏東科技大學 === 獸醫學系 === 93 === Bovine tuberculosis is one of the most important zoonoses. Test-and-slaughter policies have led to the successful eradication of this chronic latent bovine disease in several countries. However, the control method, based on intradermal tuberculin test ( ITT ) , can not reduce yearly prevalence rates of dairy cattles lower than 0.22 ％ in last ten years in Taiwan. The difficulty to eradicate the tuberculosis in the infected dairy herds was considered the most important cause of the high prevalence rate, and simultaneously using the ITT and gamma interferon diagnostic test ( IFN-γtest ) or polymerase chain reaction ( PCR ) to improve the detecting rate of tuberculosis in cattle was suggested. In this study, in order to evaluate the practicability and efficacy of this new strategy for eradicating tuberculosis, ITT, IFN-γtest and PCR were continously examinated two to six times at an interval of three months in five ITT positive herds, which have had ITT positive cattles lasted in the last 2-10 years. All the ITT positive cattles were slaughterd, and their mediastinal and retropharyngeal lymph nodes were sampled for Mycobacterium bovis isolation. Three out of these five herds were tested for evaluating eradication mode of tuberculosis, the positive cattles of IFN-γtest and/or PCR ( IFN-γ/PCR ) were isolated from negative herds at an isolated barn that more easy to be disinfected, and the density of head number were decreased. Besides, the disinfection of cowshed, communal drinking troughs and other environment were strengtherned. On the other hand, the other two herds were used as control, the mangement and hygiene were as usual. The results showed that positive rates of ITT, IFN-γtest and PCR had a gradual and obvious decrease in that three herds tested for eradication mode, while the other two control herds remained stable and higher positive rates. So we consider that this eradication mode to improve the management and hygiene can efficiently and practicably reduce the ITT positive rates in the long term of tuberculosis infected dairy herds. However, the positive rates of IFN-γtest were unusually higher than ones of ITT and PCR in all the five tested herds. Besides, the specificities of IFN-γtest were only 25.7 ％ and 26.3 ％ in 72 ITT positive cattles, if using the results of M. bovis isolation and PCR as the diagnostic standards, respectively. And only 20.0 ％ ( 1/5 ) cows were positive by the M. bovis isolation of lymph nodes in five cows that positive on IFN-γtest but negative on ITT and blood PCR. So, slaughting or culling the positive cattles of IFN-γtest in that long-term tuberculosis infected dairy herds was not suggested.