Wastewater-based epidemiology: an additional tool for TB surveillance?

Abstract

BACKGROUND AND AIM: Tuberculosis (TB) is a global public health concern that causes a significant strain on healthcare systems, particularly in sub-Saharan Africa. Current surveillance using clinic and hospital data are inadequate as they exclude those patients who either cannot access healthcare or choose not to, due to potential stigmatisation associated with HIV/TB coinfection. Wastewater based epidemiology using molecular methods may be used as an alternate surveillance system to augment data. METHODS: We used droplet-digital-PCR to assess the presence, quantity and diversity of tuberculosis-causing Mycobacterium spp. in wastewaters across several sub-Saharan African countries. Wastewater samples from Ghana, Nigeria, Kenya, Uganda, Cameroun and South Africa, from both influent and effluent (post-chlorination) were analysed. RESULTS: Mycobacterium spp. (MTBC, M. tuberculosis, M.bovis, M africanum, M.caprae) were detected in wastewater samples pre and post-treatment from all six countries, at significantly varying concentrations. The highest median concentration detected in untreated wastewater was up to 4.8 (±2.73) log copies/ml for total mycobacteria, 4.6 (±3.86) log copies/ml for MTBC, 3.4 (±2.79) log copies/ml for M. africanum all from Ghana, 3.9 (±3.17) log copies/ml for M. tuberculosis from Uganda and 3.8(±0.10) log copies/ml for M. caprae from South Africa. Apart from a significant difference between Kenya and Cameroun, removal efficiency was similar in all tested treatment plants. CONCLUSIONS: The detection of M. africanum in South Africa and other African indicates that migration should be considered in TB control strategies, particularly with developing resistant strains. The diversity of MTBC species in wastewater samples from these countries may be correlated to the prevalence of tuberculosis infections in the population served by these wastewater treatment plants and the migration of people across different countries. This study emphasizes the utility of wastewater-based epidemiology in tracking tuberculosis infections for use in surveillance. Keywords: Wastewater-based epidemiology, droplet-digital polymerase chain reaction, TB surveillance