Epidemiology and Molecular Characterization of Causative Agents of Bovine Tuberculosis in Ruminants

Abstract

A cross sectional study was conducted on 110 cattle and 397 small ruminants to determine the prevalence of bovine tuberculosis and possible risk factors, and to characterize the species of Mycobacteria circulating in Chifra district. Bacterial isolation and multiplex Polymerase Chain Reaction (PCR) were performed on milk and nasal swab samples of reactor animals. In tuberculin test, 13.64% cattle and 5.29% small ruminants were positive, and 31.58% and 25.00% were positive cultures on Lwenstein-Jensen media from milk and nasal swab samples, respectively. Based on PCR products, 12 were positive for genus Mycobacterium and none were positive for Mycobacterium tuberculosis complex or Mycobacterium avium-intracellulare complex group. The reactor rates observed for cattle under different body condition scores were poor (17.24%), medium (6.25%) and good (50.00%) Body Condition Scores (BCS) (P=0.025). The stepwise logistic regression analysis using independent variable medium BCS as a reference category indicated that good BCS (adjusted OR=4.29, 95% CI for OR=0.49-37.89) significantly affected tuberculin reactivity. This study showed that the prevalence of Single Comparative Intra-dermal Tuberculin (SCIDT) test positives and risk of acquiring the disease, increased with good BCS. Thus, more sensitive diagnostic techniques and control strategies should be considered on this risk group.