Prevalence of tuberculosis in Slaughtered Cattle in north of Iran

Objectives: Bovine tuberculosis (BTB) is a chronic disease of cattle which is characterized by granulomatous lesions mainly seen in the respiratory tract and associated lymph nodes. The aetiological agent of bovine tuberculosis is Mycobacterium bovis. M. bovis infection in cattle is now mostly confined to the respiratory system, which reflects transmission and establishment to infection mainly by this route. A single bacillus transported within a droplet nucleus is probably sufficient to establish infection within the bovine lungs. Once the bacteria enter the lungs, they begin to multiply and generally spread to the lymph nodes near the lungs. Materials & Methods: A total of 148180 cattle slaughtered at 20 slaughterhouses belonging to public and private sector were examined from January 2008 to December 2009 in mazandaran province in north of Iran. Lungs and bronchial and mediastinal lymph nodes were macroscopically examined. The information was analyzed statistically by SPSS. Results & Conclusion: In this survey Diffuse fibrinous adhesions were observed between the visceral surface of the lungs and pleura. Lesions were changed from irregular caseous bronchopneumonia to conglomera caseous lobar pneumonia especially in the caudo dorsal lobs depending on the rapidity and extent of spread. The diameters of the firm, dark yellow nodules were ranged from 0.4-3 cm. Furthermore, dense consolidation areas ranged from dark red to purple were observed almost in all the lung tissue. Bronchial and mediastinal lymph nodes were enlarged 2-3 fold in diameter and caseous yellowish content was present in the cut surface. In macroscopic examinations lesions were noted in 38 (0.062%) of 61217 cattle in 2008 and in 19 (0.021%) of 86963 cattle in 2009. In conclusion, in this study the prevalence of bovine tuberculosis in slaughtered cattle in Mazandaran province was 0.038%. The standard control measure applied to TB is test and slaughter. Disease eradication programs consisting of post mortem meat inspection, intensive surveillance including on-farm visits, systematic individual testing of cattle and removal of infected and in-contact animals as well as movement controls have been very successful in reducing or eliminating the disease.