Abstract
Mycobacterium bovis is responsible for bovine tuberculosis in both animals and humans. Despite being one of the most important global zoonotic disease, data related to the ecology and pathogenicity of bovine tuberculosis is scarce, especially in developing countries. In this report, we examined the dynamics of M. bovis transmission among dairy cattle in the Nile Delta of Egypt. Animals belonging to 27 herds from 7 governorates were tested by the Single Intradermal Comparative Skin Tuberculin (SICST), as a preliminary screen for the presence of bovine tuberculosis. Positive SICST reactors were identified in 3% of the animals spread among 40% of the examined herds. Post-mortem examination of slaughtered reactors confirmed the presence of both pulmonary and/or digestive forms of tuberculosis in > 50% of the examined animals. Targeted and whole-genome analysis of M. bovis isolates indicated the emergences of a predominant spoligotype (SB0268) between 2013–2015, suggesting a recent clonal spread of this isolate within the Nile Delta. Surprisingly, 2 isolates belonged to M. bovis BCG group, which are not allowed for animal vaccination in Egypt, while the rest of isolates belonged to the virulent M. bovis clonal complex European 2 present in Latin America and several European countries. Analysis of strain virulence in the murine model of tuberculosis indicated the emergence of a more virulent strain (MBE4) with a specific genotype. More analysis is needed to understand the molecular basis for successful spread of virulent isolates of bovine tuberculosis among animals and to establish genotype/phenotype association.
Highlights
Mycobacterium bovis is the most common causative agent of bovine tuberculosis, an important infectious disease of cattle all over the world
The single intradermal comparative skin test (SICST) screening of dairy herds included herds from 7 governorates located in the Nile Delta (Fig. 1)
The global prevalence of human M. bovis infection is higher among patients with extra-pulmonary tuberculosis, since the pathogen is frequently acquired via oral ingestion and gastrointestinal disease is an important clinical manifestation[37]
Summary
Mycobacterium bovis is the most common causative agent of bovine tuberculosis (bTB), an important infectious disease of cattle all over the world. Whole-Genome Sequencing (WGS) provided new insights into host-pathogen interactions and the dynamics of disease transmission[11,12,13]. Sequencing the genomes of clinical isolates of M. bovis provided an accurate estimates of strain geographical distribution and evolution[14,15,16,17,18] Such approaches are not common on isolates from Africa and the Middle East, contratry to the analysis of isolates from Euroupe[8]. BTB reached up to 41% on the herd-level but only 3.4% on the animal-level Both genotyping and WGS indicate the genomic diversity of Egyptian isolates with predominance of isolates being closely related to clonal complex “European 2”. We utilized WGS to gain novel insights onto polymorphism and virulence of M. bovis isolates circulating in the Nile Delta
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