Biology subjects

Zewude, A.

Publications and source records attributed to Zewude, A..

3 recordsLinked to original sources

bioRxiv2020

Population structure and transmission of Mycobacterium bovis in Ethiopia

Bovine tuberculosis (bTB) is endemic in cattle in Ethiopia, a country that hosts the largest national cattle herd in Africa. The intensive dairy sector, most of which is peri-urban, has the highest prevalence of disease. Previous studies in Ethiopia have demonstrated that the main cause is Mycobacterium bovis (M. bovis), which has been investigated using conventional molecular tools including deletion typing, spoligotyping and Mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR). Here we use whole genome sequencing (WGS) to examine the population structure of M. bovis in Ethiopia. A total of 134 M. bovis isolates were sequenced including 128 genomes from 85 mainly dairy cattle and six genomes isolated from humans, originating from 12 study sites across Ethiopia. These genomes provided a good representation of the previously described population structure of M. bovis, based on spoligotyping and demonstrated that the population is dominated by the clonal complexes African 2 (Af2) and European 3 (Eu3). A range of within-host diversity was observed amongst the isolates and evidence was found for both short- and long-distance transmission. Detailed analysis of available genomes from the Eu3 clonal complex combined with previously published genomes revealed two distinct introductions of this clonal complex into Ethiopia between 1950 and 1987, likely from Europe. This work is important to help better understand bTB transmission in cattle in Ethiopia and can potentially inform national strategies for bTB control in Ethiopia and beyond.

genomics↗

bioRxiv2020

Cellular and Cytokine Responses in the Granulomas of Asymptomatic Cattle naturally infected with Mycobacterium bovis in Ethiopia

Cellular (CD3+ T cell and CD68+ macrophages), cytokines (IFN-{gamma}+ and TNF-+) and effector molecule (iNOS+) responses were evaluated in the lymph nodes and tissue of cattle naturally infected with Mycobacterium bovis. Detailed post mortem and immunonohistochemical examinations of lesions were performed on 16 cows positive for single intradermal cervical comparative tuberculin test (SICCTT) and identified from dairy farms located around the Addis Ababa City. The severity of the gross lesion was significantly higher (p=0.003) in M. bovis culture positive (n=12) cows than in culture negative (n=4). Immunohistochemical techniques showed that the mean percentage labelling of CD3+ T cells decreased as the stage of granuloma increased from stage I to stage IV in culture positive cows (p<0.001). On the other hand, the proportional fraction of CD68+ macrophages and the concentrations of IFN-{gamma}+, TNF-+ and iNOS+ increased significantly from stage I to stage IV (p< 0.001) in culture positive cows. At the early stage of the granuloma, the culture negative cows showed significantly higher mean proportions of CD68+ macrophages (p=0.03) as well as the concentrations of iNOS+ (p=0.007) compared to culture positive cows. Similarly, at advanced granuloma stages, culture negative cows demonstrated significantly higher mean proportions of CD3+ T cells (p< 0.001) compared to culture positive cows. Thus, the present study demonstrated that following natural infection of cows with M. bovis, as the stage of granuloma increases from stage I to stage IV, the proportion of CD3+ cells decreases while the immunolabeling fraction of CD68+ macrophages, IFN-{gamma}+, TNF- and iNOS+ increases.

immunology↗

bioRxiv2019

Tuberculosis at farmer-cattle interface in the rural villages of South Gondar Zone of northwest Ethiopia

BackgroundTuberculosis (TB) has been an important public health concern in Ethiopia, particularly at areas of human-animal intersection. However, limited epidemiological information is available in this respect in the country. Therefore, the present study was conducted to investigate the transmission of TB at human-cattle interface, associated risk factors and public awareness about the disease at South Gondar Zone, northwest Ethiopia.\n\nMethodsA cross sectional study was conducted between March 2015 and April 2018 on 186 farmers and 476 cattle in South Gondar Zone, northwest Ethiopia. Bacteriological examination, region of difference (RD) 9 based polymerase chain reaction (PCR), single intradermal comparative tuberculin test (SIDCTT) and questionnaire were used for undertaking this study.\n\nResultsCulture positivity in farmers was 59.7% (111/186) and all the culture positive isolates were M. tuberculosis. About 68% (74/111) of culture positive respondents did not know about the transmission of TB from cattle to human or vice versa. The animal and herd prevalence of bovine TB were 1.5% (7/476) and 7.4% (7/95) respectively. The odd of bovine TB in cattle owned by TB positive households was slightly higher than those owned by TB free households (adjusted odds ratio, AOR=1.39; 95% CI: 0.31-7.10; p = 0.76).\n\nConclusionAlthough SIDCTT reactivity was slightly higher in cattle owned by TB positive households, all the human isolates were M. tuberculosis and no M. bovis was isolated from farmers, which could be due to the low prevalence of bovine TB in the area.

epidemiology↗