| Bovine tuberculosis (BTB) is an important zoonotic disease, which seriously endangers human’s health and public safety and impede the production and economic development of animal husbandry. At present, there is no suitable vaccine and rapid detection techniques. For large-scale dairy farm, the implement of comprehensive prevention and control measures including "quarantine, surveillance, disinfection and culling" is an effective way for the prevention, control and eliminating carriers of. BTB A comparative study of routine detection of BTB of intradermal allergy test shows that Single Intradermal Comparative Cervical Tuberculin (SICCT) can exclude some avian PPD reaction positive catties, which can improve specificity. SICCT is more suitable for the detection of BTB carriers in controlled or stable controlled area. The results of pathogen detection indicated high non-specificity of Single Intradermal Cervical Tuberculin (SICT)."Tuberculosis Risk Assessment Model of Large-scale dairy farm " was used to evaluate BTB prevention and control level of large-scale dairy farm in Shanghai. Analysis of surveillance data of BTB, epidemiological situation about dairy farms and farm workers, and epidemic situation data of human tuberculosis, is used to raise schemes and recommendations about monitoring, elimination carriers, prevention and control of BTB in the large-scale dairy farms.1. Comparative Study of SICT and SICCT in detection of BTB In order to compare the advantages and disadvantages of SICT and SICCT and provide the basis for clinical application, detection by SICT and SICCT were made in2000cows from four dairy farms. The results showed that the coincidence of SICT positive cows by imported bovine PPD and domestic bovine PPD was19and the positive coincidence rate was64.41%(19/29.5) among1745tested cows. The coincidence of SICT and SICCT positive cows by imported bovine PPD was5and the positive coincidence rate was55.56%(5/9) among1107tested cows. The coincidence of SICT and SICCT positive cows by domestic bovine PPD was3and the positive coincidence rate was27.27%(3/11) among1316tested cows. The test results show that the SICT has higher sensitivity. In BTB epidemic areas, using SICT for the census testing of entire herd is conducive to early detection of BTB carriers and can accelerate the pace of BTB control. However, using SICT in BTB controlled or stablility controlled area may bring out more nonspecific results, which is not conducive to the elimination of BTB carriers. Compared with SICT, SICCT can exclude some avian PPD reaction positive cows and improve specificity of the test, which is more suitable for purification detection of BTB in the control or stablility control area.2. Pathogen isolation and identification of SICT positive cowsIn this study, SICT positive cows were detected by pathogen isolation and identification. Sixteen acid-fast bacteria strains were isolated from118tissue samples and twelve strains were identified as Mycobacterium. The isolation rate of Mycobacterium was10.2%(12/118). Of the twelve mycobacteria strains one strain was Mycobacterium bovis and the other eleven strains were identified as Mycobacterium avium, Mycobacterium terrace and other Nontuberculous mycobacteria (NTM). Mycobacterium bovis and NTM accounted for8.3%(1/11) and91.7%(10/11) of all isolates respectively. The results of pathogen detection indicated the high non-specificity of the SICT detection method. To ensure the accuracy of the test, it is necessary to use more than one method for diagnosis. At the same time, the rapid isolation and identification of Mycobacterium and strain identification technology should be introduced into the laboratory diagnosis of BTB, which can further improve the specificity of detection of BTB.3. The survey and current situation evaluation of BTB prevention and control in Shanghai areaAccording to " Shanghai Long-term and Medium-term Program of Prevention of Animal Disease (2012-2020)","BTB Prevention and Control Technical Specification"," Brucellosis and Tuberculosis Prevention and Control Program of2009-2015", as well as BTB prevention and control situation and practical experience in Shanghai, we made suggestions and schemes on the surveillance, prevention and control and elimination of BTB in Shanghai scale-up dairy farms.4. Establishment and validation of BTB risk assessment model in large-scale dairy farmIn order to reduce the transmission risk of BTB in large scale dairy farms, on the basis of research and determination on BTB transmission and epidemic factors, using "Delphi method" we selected48risk factors from the seven aspects including site location, site layout, facilities and equipments, feeding management, sanitation and epidemic prevention, staff management, monitoring, epidemic history and economic factors, and determined the weight of each factor. Then risk level is divided into three level:high risk, medium risk and low risk by Qualitative Risk Analysis Method and the "Large-scale Dairy Farm BTB Risk Assessment Model" was established. Through the validation and the preliminary application, this model can be used to evaluate BTB prevention and control level in scale-up dairy farms and is conducive to BTB risk management in large-scale dairy farms.5. Development and application of prevention, control and elimination measures of BTB in large scale dairy farmsIn order to guide prevention, control and elimination of BTB in large scale dairy farms, we developed a set of prevention, control and elimination measures of BTB suitable for large scale dairy farms in Shanghai on the basis of BTB prevention and control level and technology study, combined with BTB risk assessment results of large scale dairy farms. In the mean time, four large scale dairy farms were selected to demonstrate the application, surveillance and verification. The results showed that the average positive rate of BTB dropped from0.48%to0.22%in the four demonstration dairy farms, which was reduced by54.2%. The average numbers of positive cattles were reduced from39.5to18, which was reduced by54.4%. According to the analysis by SPSS there were significant difference in the positive rate between2010-2011and2012-2013in the four demonstration dairy farms (P<0.05). The experiment indicated that the implementation effect of prevention, control and elimination measures of BTB in small and medium scale dairy farms was more effective than in large scale dairy farms.Conclusion1. Compare and analyse the two detection methods SICT and SICCT. The sensitivity of SICT is higher, which is conducive to the early detection of BTB infection in cattle in BTB epdemic areas. SICCT has high specificity and is more suitable for BTB elimination detection in the controlled or stable controlled area.2. SICT positive cows were detected by pathogen isolation and identification. M.bovis and NTM accounted for8.3%and91.7%of all isolates respectively. The results indicated the high non-specificity of SICT. To ensure the accuracy of the detection, it is necessary to use more than one test for diagnosis.3. Through the investigation and analysis of the surveillance data about BTB of cows in Shanghai area, the present prevention and control level of BTB and the basic information of employee in the dairy farms, as well as data of human tuberculosis prevelence situation, we assessed the status of prevention and made suggestions and schemes for the prevention and control.4. We established a "Large-Scale Dairy Farm BTB Risk Assessment Model". This model can be used to evaluate the control level of BTB in scale-up diary farms, which is conducive to BTB risk management.5. According to the BTB control program and technical specifications, as well as the prevention and control situation about BTB of cows in Shanghai area and practical experience, we developed technical specifications for the prevention, control and elimination of BTB in scale-up dairy farms, which were successfully implemented in the four dairy farms. |
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