Prevalence of pulmonary TB and spoligotype pattern of Mycobacterium tuberculosis among TB suspects in a rural community in Southwest Ethiopia

Amare Deribew,Jafar Shiffa,Robert Colebunders,Fetene Deribe,Alemseged Abdissa,Kifle Woldemichael,Chali Jira,Abraham Aseffa,Mesele Bezabih,Gemeda Abebe,Markos Tesfaye,Ludwig Apers,Tadiye Abeje

doi:10.1186/1471-2334-12-54

Abstract

BackgroundIn Ethiopia where there is no strong surveillance system and state of the art diagnostic facilities are limited, the real burden of tuberculosis (TB) is not well known. We conducted a community based survey to estimate the prevalence of pulmonary TB and spoligotype pattern of the Mycobacterium tuberculosis isolates in Southwest Ethiopia.MethodsA total of 30040 adults in 10882 households were screened for pulmonary TB in Gilgel Gibe field research centre in Southwest Ethiopia. A total of 482 TB suspects were identified and smear microscopy and culture was done for 428 TB suspects. Counseling and testing for HIV/AIDS was done for all TB suspects. Spoligotyping was done to characterize the Mycobacterium tuberculosis isolates.ResultsMajority of the TB suspects were females (60.7%) and non-literates (83.6%). Using smear microscopy, a total of 5 new and 4 old cases of pulmonary TB cases were identified making the prevalence of TB 30 per 100,000. However, using the culture method, we identified 17 new cases with a prevalence of 76.1 per 100,000. There were 4.3 undiagnosed pulmonary TB cases for every TB case who was diagnosed through the passive case detection mechanism in the health facility. Eleven isolates (64.7%) belonged to the six previously known spoligotypes: T, Haarlem and Central-Asian (CAS). Six new spoligotype patterns of Mycobacterium tuberculosis, not present in the international database (SpolDB4) were identified. None of the rural residents was HIV infected and only 5 (5.5%) of the urban TB suspects were positive for HIV.ConclusionThe prevalence of TB in the rural community of Southwest Ethiopia is low. There are large numbers of undiagnosed TB cases in the community. However, the number of sputum smear-positive cases was very low and therefore the risk of transmitting the infection to others may be limited. Active case finding through health extension workers in the community can improve the low case detection rate in Ethiopia. A large scale study on the genotyping of Mycobacterium tuberculosis in Ethiopia is crucial to understand transmission dynamics, identification of drug resistant strains and design preventive strategies.

Highlights

In Ethiopia where there is no strong surveillance system and state of the art diagnostic facilities are limited, the real burden of tuberculosis (TB) is not well known
We performed such a survey in a predominantly rural area of Southwest Ethiopia to estimate the prevalence of TB and to characterize the Mycobacterium tuberculosis strains circulating in the community
Characteristics of TB suspects A total of 30040 adults in 10882 households were screened for pulmonary TB

Summary

Introduction

In Ethiopia where there is no strong surveillance system and state of the art diagnostic facilities are limited, the real burden of tuberculosis (TB) is not well known. In the absence of a strong surveillance system, state of the art diagnostic laboratories and high health service coverage, community-based prevalence surveys are good alternatives to estimate the burden of TB and to evaluate the impact of the TB control program. We performed such a survey in a predominantly rural area of Southwest Ethiopia to estimate the prevalence of TB and to characterize the Mycobacterium tuberculosis strains circulating in the community

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Discussion

Conclusion