Broad diversity of Mycobacterium tuberculosis complex strains isolated from humans and cattle in Northern Algeria suggests a zoonotic transmission cycle

Mycobacterium tuberculosis complex (MTBC) comprises closely related species responsible for human and animal tuberculosis (TB). Efficient species determination is useful for epidemiological purposes, especially for the elucidation of the zoonotic contribution. In Algeria, data on MTBC genotypes are largely unknown. In this study, we aimed to investigate the occurrence and diversity of MTBC genotypes causing human and bovine TB in Northern Algeria. During a two-year sampling period (2017-2019) in two regions of Northern Algeria, we observed an overall prevalence of 6.5% of tuberculosis (TB) among slaughtered cattle, which is higher than previous Algerian data yet comparable to neighboring countries. A total of 296 Mycobacterium tuberculosis complex (MTBC) isolates were genotyped by spoligotyping: 181 from tissues with TB-like lesions collected from 181 cattle carcasses and 115 from TB patients. In human isolates, we identified 107 M. tuberculosis, seven M. bovis and one "M. pinnipedii-like", while for bovine samples, 174 isolates were identified as M. bovis, three as M. caprae, three as "M. pinnipedii-like" and one as "M. microti-like". The majority of isolates (89.2%) belonged to 72 different known Shared International Types (SIT) or M. bovis spoligotypes (SB), while we also identified seven new SB profiles (SB2695 to SB2701). Twenty-eight of the SB profiles were new to Algeria. Our data suggest zoonotic transmission in Setif, where significantly more TB was observed among cattle (20%) compared to the slaughterhouses from the three other regions (5.4%-7.3%) (p < 0.0001), with the isolation of the same M. bovis genotypes from TB patients. The present study showed a high genetic diversity of MTBC isolated from human and cattle in Northern Algeria. Even though relatively small in terms of numbers, our data suggest the zoonotic transmission of TB from cattle to humans, suggesting the need for stronger eradication strategies for bovine TB. Author summary To establish the circulating genotypes causing human and bovine tuberculosis (TB) in Northern Algeria, spoligotyping was used to characterize 296 Mycobacterium tuberculosis complex isolates of human (n = 115) and bovine (n = 181) origin. Molecular identification showed that most human isolates were identified as M. tuberculosis, with few M. bovis isolates, while among cattle, M. bovis, M. caprae, "M. pinnipedii-like" and "M. microti-like" isolates were found. Among M. tuberculosis isolates, 84 (78.5%) were classified into six families, with three prevailing genotypes (Latin-American Mediterranean (LAM), T clade and Haarlem). Concerning M. bovis, three spoligotype profiles (SB0120, SB0121 and SB0134) were predominant in Algeria, as in other Northern African countries. In addition, we identified some new M. bovis types (SB2695 to SB2701). For the first time in Algeria, M. bovis was found in 6% of human cases analyzed in this study. Furthermore, we documented regional variability in the prevalence of bovine TB among slaughtered cattle and in the probability of human TB being caused by M. bovis, suggesting the zoonotic transmission of M. bovis. This finding should draw the attention of Algerian health authorities to the importance of the effective control of bovine TB, including the establishment of traceability systems for livestock from the farm to slaughterhouse and between farms.

Publication year:2020

Keywords:A1 Journal article

BOF-keylabel:yes

BOF-publication weight:6

CSS-citation score:1

Authors:International

Authors from:Government

Accessibility:Open