Tuberculosis in Farmers and Their Cattle in Smallholder Farming System in South Gondar Zone of Northwest Ethiopia: Epidemiology and Drug Sensitivity Profiles

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Date

2019-06-05

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Addis Ababa University

Abstract

Tuberculosis (TB), an infectious disease caused by Mycobacterium tuberculosis complex (MTBC), remains a public health problem in Ethiopia. However, there is still shortage of epidemiological data in different parts of the country, particularly, in the rural and semi-urban communities. Hence, the present study was conducted to investigate the epidemiology of TB in farmers and their cattle in South Gondar Zone, northwest Ethiopia. In addition, the drug sensitivity profile of M. tuberculosis isolated from TB cases was evaluated. The human aspect of the study was conducted on 2953 individuals using clinical and bacteriological examinations.Region of difference (RD) 9-based polymerase chain reaction (PCR) and spoligotyping were done on the MTBC isolates. Drug sensitivity pattern of the isolates was analyzed using the GenoType MTBDRplus assay. The animal aspect of the study was conducted on 95 herds consisting of 476 cattle using the single intra-dermal cervical comparative tuberculin test (SICCTT). The study determined TB prevalence of 6.3% (186/2953) in humans visiting health facilities in the study area. Some of the patients’ demographic characteristics (patients’ origin, c2 value: 62.80; p<0.001 and age group,c2 value: 35.46; p<0.001) were found to be significantly associated risk factors for TB infection. Out of 96 M. tuberculosis isolates spoligotyped, 35 spoligotype patterns iii were identified, of which 22 were shared typesand consisted of 79 isolates. Thirteen of these patterns were clustered consisting of 74 isolates making the clustering rate of 77.1%. The dominant shared international types (SITs) were SIT53 (Lineage 4), SIT149 (Lineage 4) and SIT428 (Lineage 3), each consisting of 18.8%, 12.5% and 12.5% of the total isolates, respectively. The SIT 428 was found to be specific to the study area and associated with EPTB. From the culture positive M. tuberculosis isolates, 18.0% (20 /111) were resistant to at least one of the two most effective firstline anti-TB drugs, isoniazid (INH) and rifampicin (RIF). Multi-drug resistant (MDR) TB was detected in 1.8% (2/111) of the cases. The high proportion of drug resistant M. tuberculosis strains in the study area indicates the need for an increased effort to strengthen TB control program in the study area.The animal and herd prevalence of bovine TB were 1.5% (7/476) and 7.4% (7/95), respectively with the odds of bovine TB in cattle owned by TB positive households being slightly higher than those owned by TB free households. This may suggest the zoonotic transmission potential of TB from domestic cattle. Overall, the study revealed a relatively high prevalence of TB in humans and all human isolates were M. tuberculosis and no M. bovis was isolated from the study population. The failure to detect M. bovis in the study could be due to the low prevalence of bovine TB in the area.

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Keywords

Tuberculosis, Epidemiology, Drug sensitivity, Zoonoses, South Gondar, Ethiopia

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