Isolation and identification of mycobacteria responsible for tuberculosis of dromedaries in Algeria.

Tuberculosis in dromedaries in Algeria has been little studied to date. The purpose of this study is to determine the prevalence of tuberculosis in dromedaries in three Algerian slaughterhouses using samples from suspected tuberculosis lesions, which were detected on carcasses during a post-mortem visual inspection. The study also uses laboratory diagnosis to isolate and identify the agents responsible for the infection. Between 2016 and 2018, 102 carcasses (3.05%; with a confidence interval [CI] of 95% from 2.05 to 3.69) were suspected of tuberculosis out of a total of 3,342 dromedary carcasses inspected. The lesions were located as follows in the carcasses: 64 of 102 were in the lungs, 37 in the liver and 1 in a bronchial ganglion. Five and six samples respectively of suspected tuberculosis lesions were found to be positive by bacilloscopy (4.9%; with a CI of 95% from 1.61 to 11.1) and in culture (5.88%; with a CI of 95% from 2.19 to 12.36). The concordance between bacilloscopy and culture was good (kappa coefficient of 0.71) and the probability of finding a positive culture was 184 times greater when the bacilloscopy was positive (value of p = 0.01). Molecular characterisation by polymerase chain reaction of extracts of DNA gave a positive signal, indicating that the isolated strains belonged to a mycobacterium genus. An enzymatic restriction on DNA extracts indicated the presence of mycobacterium DNA belonging to the Mycobacterium tuberculosis complex. Spoligotyping on the same DNA extracts confirmed the presence of four strains of Mycobacterium bovis with the same spoligotype SB0941 and another strain with spoligotype SB2562, a newly described profile in this study, which is phylogenetically close to the previous profile. Using suspected tuberculosis lesions in dromedaries, a non-tuberculosis mycobacterium was identified as Mycobacterium virginiense MO-233 (sequence ID: Nr149186) using the sequencing technique on the region 16SrDNA. Having demonstrated the presence of tuberculosis with M. bovis in the Algerian dromedary population, it is now necessary to implement measures to control it in order to reduce transmission between animals and humans.