Abstract
The East African Indian (EAI) and Central Asian (CAS) lineages of Mycobacterium tuberculosis complex (MTBC) mainly infect tuberculosis (TB) patients in the eastern hemisphere which contains many of the 22 high TB burden countries including China and India. We investigated if phylogeographical, epidemiological and demographical characteristics for these 2 lineages differed in SITVIT2 database. Genotyping results and associated data (age, sex, HIV serology, drug resistance) on EAI and CAS lineages (n = 10,974 strains) were extracted. Phylogenetic and Bayesian, and other statistical analyses were used to compare isolates. The male/female sex ratio was 907/433 (2.09) for the EAI group vs. 881/544 (1.62) for CAS (p-value<0.002). The proportion of younger patients aged 0–20 yrs. with CAS lineage was significantly higher than for EAI lineage (18.07% vs. 10.85%, p-value<0.0001). The proportion of multidrug resistant and extensively drug resistant TB among CAS group (30.63% and 1.03%, respectively) was significantly higher than in the EAI group (12.14% and 0.29%, respectively; p-value<0.0001). Lastly, the proportion of HIV+ patients was 20.34% among the EAI group vs. 3.46% in the CAS group (p-value<0.0001). This remarkable split observed between various parameters for these 2 lineages was further corroborated by their geographic distribution profile (EAI being predominantly found in Eastern-Coast of Africa, South-India and Southeast Asia, while CAS was predominantly found in Afghanistan, Pakistan, North India, Nepal, Middle-east, Libya, Sudan, Ethiopia, Kenya and Tanzania). Some geo-specificities were highlighted. This study demonstrated a remarkable cleavage for aforementioned characteristics of EAI and CAS lineages, showing a North-South divide along the tropic of cancer in Eastern hemisphere–mainly in Asia, and partly prolonged along the horn of Africa. Such studies would be helpful to better comprehend prevailing TB epidemic in context of its historical spread and evolutionary features, and provide clues to better treatment and patient-care in countries and regions concerned by these lineages.
Highlights
Africa and Asia are the two continents concentrating the highest incidence of worldwide Mycobacterium tuberculosis complex (MTBC) cases
In the present study, based on the recently released SITVIT2 database [12], we describe the overall distribution and epidemiological features of spoligotyping-based East-African-Indian (EAI– known as Lineage 1 or the Large Sequence Polymorphisms (LSP)-based Indo-Oceanic lineage), and Central Asian (CAS– known as LSP-based Lineage 3) lineages, which are predominantly found in Eastern Africa, South-East Asia, Indian subcontinent, and Western Asia [17]
East African Indian (EAI) lineage strains were more common in East African, South and South-Eastern Asian countries, whereas CAS lineage strains were predominantly found in South and Western Asian countries, as well as in North- and East-African countries
Summary
Africa and Asia are the two continents concentrating the highest incidence of worldwide Mycobacterium tuberculosis complex (MTBC) cases. A further one quarter (26%) occurred in Africa, which had the highest rates of cases and deaths relative to population [1]. In such a context, TB remains a priority communicable disease, even today, as underlined by the recent fact sheet from World Health Organization (WHO; [1]). Knowing that Mycobacterium tuberculosis and humans have coevolved for thousands of years [2], such an objective can only be achieved using modern tools of molecular epidemiology in conjunction with international databases and web tools able to extract patient demographic and clinical data from longitudinal studies, allowing to identify and highlight the various ways of ongoing TB transmission and a better understanding of the disease
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