Community-based prevalence of undiagnosed mycobacterial diseases in the Afar Region, north-east Ethiopia

Background: Information on the community-based prevalence of tuberculosis (TB) in different settings is vital for planning, execution and evaluation of strategies to control the disease. Objective: To assess community-based prevalence of undetected active pulmonary TB (PTB) in pastoralists of the Amibara District. Methods: Between March and April 2010, a community-based cross-sectional survey of undiagnosed active PTB was conducted in the pastoralists of the Amibara District of the Afar Region, north-east Ethiopia. The study participants were interviewed for symptoms suggestive of PTB using a structured questionnaire. Sputum samples were collected and processed for smear microscopy and culture. Mycobacterium genus typing was performed using a multiplex polymerase chain reaction (PCR). Results: Out of 222 individuals who had symptoms suggestive of PTB, 4 (1.8%) were found positive by smear microscopy, while mycobacterial growth was observed on 62 (27.9%) samples. Mycobacterium genus typing was carried out for 42 of these 62 samples; 39 (92.9%) gave a positive signal for the genus Mycobacterium. Of these, 23 (59%) isolates proved to be members of the Mycobacterium tuberculosis (Mtb) complex, while the remaining 16 (41.0%) were found to be members of non-tuberculous Mycobacteria (NTM) species. Conclusion: Sputum culture is highly sensitive, and it is the gold standard for the bacteriological diagnosis of PTB, while smear microscopy is less sensitive to detect acid fast bacilli (AFB) in stained sputum smears. The findings of the present study warrant the strengthening of culture facility services in the study area. The study also provides important preliminary information on the status of NTM infection in the pastoral setting. Nevertheless, further investigations into the species identification of the NTM infections would be useful in the study area.