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Spatial clustering of rifampicin-resistant tuberculosis and dominant clone in Rwanda: implications for targeted case finding

I Cuella Martin(2) J C.S Ngabonziza(2,3,4) W Mulders(2) L Rigouts(2,5) B C de Jong(2) E M.H Mitchell(1)

1:Department of Public Health, Institute for Tropical Medicine, Antwerp, Belgium; 2:Mycobacteriology Unit, Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium; 3:Research Innovation and Data Science Division, Rwanda Biomedical Centre, Kigali, Rwanda; 4:Department of Clinical Biology, University of Rwanda, Kigali, Rwanda; 5:Department of Biomedical Sciences, Antwerp University, Antwerp, Belgium

In 2005, Rwanda established a program to manage rifampicin-resistant tuberculosis (RR-TB), which included standardized treatment and drug-susceptibility testing for rifampicin. Since then, the estimated prevalence of RR-TB in new cases declined from 3.9% (95%CI 2.5-5.7%) to 1.4% (95%CI 1.09-1.89%) in 2019-2020. RR-TB in Rwanda is largely driven by transmission of a single dominant clone, the Rwanda RR-TB clone (R3clone), which is resistant to all first-line drugs. In order to pinpoint recent transmission chains and develop effective targeted case-finding strategies, we utilized spatial epidemiology to detect any remaining hotspots.

We conducted a retrospective analysis of 213 patients from 2005-2021 with RR-TB confirmed through whole genome sequencing (WGS) and a known geographical cell address (Rwanda is comprised of 2148 cells). 52% (112 of 213) of the included isolates were R3 clone. Total RR-TB and R3clone prevalence were mapped using QGIS, and SaTScan software was used with the discrete Poisson model to identify circular clusters.

The study of RR-TB cases revealed the presence of three significant spatial clusters comprising 91 cells in the vicinity of Kigali, and exhibiting relative risks of 5.76, 10.30 and 11.59. The analysis of R3 clone hotspots showed again three Kigali clusters, as well as an additional cluster of eight cells situated in Huye district (Southern Province). These findings suggest that R3 clone may have a higher degree of transmissibility. Future analyses will explore possible diagnostic access, demographic, and health correlates. This study highlights the importance of continued monitoring and analysis to target more effective prevention and control measures.

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