Detection and Quantification of Enteric Pathogens in Aerosols Near Open Wastewater Canals in Cities with Poor Sanitation

Abstract

Urban sanitation infrastructure is inadequate in many low-income countries, leading to the presence of highly concentrated, uncontained fecal waste streams in densely populated areas. Combined with mechanisms of aerosolization, airborne transport of enteric microbes and their genetic material is possible in such settings but remains poorly characterized. We detected and quantified enteric pathogen-associated gene targets in aerosol samples near open wastewater canals (OWCs) or impacted (receiving sewage or wastewater) surface waters and control sites in La Paz, Bolivia; Kanpur, India; and Atlanta, USA, via multiplex reverse-transcription qPCR (37 targets) and ddPCR (13 targets). We detected a wide range of enteric targets, some not previously reported in extramural urban aerosols, with more frequent detections of all enteric targets at higher densities in La Paz and Kanpur near OWCs. We report density estimates ranging up to 4.7 × 102 gc per mair 3 across all targets including heat-stable enterotoxigenic Escherichia coli, Campylobacter jejuni, enteroinvasive E. coli/Shigella spp., Salmonella spp., norovirus, and Cryptosporidium spp. Estimated 25, 76, and 0% of samples containing positive pathogen detects were accompanied by culturable E. coli in La Paz, Kanpur, and Atlanta, respectively, suggesting potential for viability of enteric microbes at the point of sampling. Airborne transmission of enteric pathogens merits further investigation in cities with poor sanitation.

Associations Between Eight Earth Observation‐Derived Climate Variables and Enteropathogen Infection: An Independent Participant Data Meta‐Analysis of Surveillance Studies With Broad Spectrum Nucleic Acid Diagnostics

“…Four main hypothesized mechanisms by which hydrometeorological conditions impact short‐term risk of enteropathogen transmission include waterborne dispersal (K. Levy et al., 2016 ), airborne dispersal (Dennehy, 2000 ; Ginn et al., 2021 ), survival on surfaces and fomites (Abad et al., 1994 ; Hurst et al., 1980 ) and host factors or behaviors influencing contact rates (T.‐C. Chan et al., 2015 ).…”

A systematic review of enteric pathogens and antibiotic resistance genes in outdoor urban aerosols

“…Results of this systematic review suggest that fecal signatures are present in ambient urban air across the globe, along with evidence suggesting aerosols may play a role in urban AR spread. Notably, studies conducted in cities in LMICs show a broad and diverse range of airborne microbial gene targets of possibly human fecal origin, potentially related to sanitation infrastructure deficits 123 that permit uncontained waste flows in densely populated urban areas 43 . However, the results also reveal large gaps in the characterization and detection of important enteric and AR-associated pathogens in bioaerosols in ambient urban air.…”

“…130 This evidence suggests that these may be important targets in urban settings as well, especially when fecal contamination is widespread. Furthermore, few studies targeted and detected enteric viruses, even though fecal microbes are present and often are co-occurring with enteric viruses 43 .…”

“…39 However, in low-and-middle income countries (LMICs) where wastewater and biosolids present greater risks due to the high number of circulating infectious diseases in the population contributing waste and the presence of unsequestered waste in closer proximity to more people, risk may be higher for exposure through bioaerosols. [40][41][42][43] We conducted a systematic review of published estimates reporting detections of enteric pathogen and ARGs in cities to current knowledge in this emerging area.…”

Invited Perspective: Sanitation Innovation Holds Promise but Must Consider Risks to Users

“…2013 ), any use of excreta carries risks of exposure to those contacting the material if pathogens are not inactivated. Enteric pathogens are highly transmissible through well-known direct and indirect pathways ( Ginn et al. 2021 ; Penakalapati et al.…”