Prevalence of Bovine Tuberculosis in Dairy Cattle at Dairy Farm of Holeta Agricultural Research Center, Central Ethiopia

Abstract

Bovine tuberculosis, caused by Mycobacterium bovis, which belongs to Mycobacterium tuberculosis complex (MTC), is a globally distributed zoonotic disease in cattle and remained an economic problem in Ethiopia. This study was conducted from November 2015 to May 2017 on 502 dairy cattle managed under the Dairy Farm at Holeta Agricultural Research Center. The objectives of the study were to estimate the prevalence, evaluate gamma interferon and comparative intradermal tuberculin test (CIDTT) for the diagnosis of bovine tuberculosis, and isolate, identify, and characterize causative agents of bovine tuberculosis using RD4 deletion typing molecular technique. Data collected on study animals were analyzed using STATA version13 software. Out of 502 cattle examined using different methods, 148 (29.5%, 95% CI: 25.5 - 33.7%) were positive for bovine tuberculosis using CIDTT, 173 (34.5%, 95% CI: 30.3 -38.8%) for Gamma-Interferon and 97 (19.3%, 95% CI: 15.9 – 23.1%) were positive for both tests. The results indicated moderate Kappa agreement between the two tests. Among 60 slaughtered animals that were positive for both test, 48 (80.0%) had gross tuberculosis lesion while the rest 12 (20.0%) had no such lesions. Out of 48 gross lesions cultured on Löwenstein–Jensen medium, 24 samples were culture-positive (19 on pyruvate enriched media that were suspected as Mycobacterium bovis while the 5 on glycerol which suspected as Mycobacterium tuberculosis). All of the isolates were subjected to PCR amplification for RD4 deletion typing technique that confirmed 8 (33.3%) of the isolates to be M. bovis. The rest being other members of the genus Mycobacterium. From the study it was concluded that bovine tuberculosis is highly prevalent in the studied farm. The comparison of evaluation techniques indicated the presence of moderate Kappa agreement between gamma interferon (ELISA) and tuberculin test (PPD). Therefore, it is recommended that an urgent need for regular surveillance, implementation of strict biosecurity measures and further large scale molecular epidemiological studies need to be implemented for effective prevention and control of bovine tuberculosis.