title: The Ecological Dynamics of Fecal Contamination and Salmonella Typhi and Salmonella Paratyphi A in Municipal Kathmandu Drinking Water.
abstract: One of the UN sustainable development goals is to achieve universal access to safe and affordable drinking water by 2030. It is locations like Kathmandu, Nepal, a densely populated city in South Asia with endemic typhoid fever, where this goal is most pertinent. Aiming to understand the public health implications of water quality in Kathmandu we subjected weekly water samples from 10 sources for one year to a range of chemical and bacteriological analyses. We additionally aimed to detect the etiological agents of typhoid fever and longitudinally assess microbial diversity by 16S rRNA gene surveying. We found that the majority of water sources exhibited chemical and bacterial contamination exceeding WHO guidelines. Further analysis of the chemical and bacterial data indicated site-specific pollution, symptomatic of highly localized fecal contamination. Rainfall was found to be a key driver of this fecal contamination, correlating with nitrates and evidence of S. Typhi and S. Paratyphi A, for which DNA was detectable in 333 (77%) and 303 (70%) of 432 water samples, respectively. 16S rRNA gene surveying outlined a spectrum of fecal bacteria in the contaminated water, forming complex communities again displaying location-specific temporal signatures. Our data signify that the municipal water in Kathmandu is a predominant vehicle for the transmission of S. Typhi and S. Paratyphi A. This study represents the first extensive spatiotemporal investigation of water pollution in an endemic typhoid fever setting and implicates highly localized human waste as the major contributor to poor water quality in the Kathmandu Valley.
authors.affiliation: Oxford University Clinical Research Unit, Patan Academy of Health Sciences, Kathmandu, Nepal.
authors.forename: Abhilasha
authors.initials: A
authors.lastname: Karkey
authors.affiliation: MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, United Kingdom.
authors.forename: Thibaut
authors.initials: T
authors.lastname: Jombart
authors.affiliation: The Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, United Kingdom.|Microbiology Group, The Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom.
authors.forename: Alan W
authors.initials: AW
authors.lastname: Walker
authors.affiliation: The Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam.|Centre for Tropical Medicine, Oxford University, Oxford, United Kingdom.
authors.forename: Corinne N
authors.initials: CN
authors.lastname: Thompson
authors.affiliation: Grupo de Investigación Ciencia e Ingeniería del Agua y el Ambiente, Facultad de Ingeniería, Pontificia Universidad Javeriana, Bogotá, Colombia.
authors.forename: Andres
authors.initials: A
authors.lastname: Torres
authors.affiliation: Oxford University Clinical Research Unit, Patan Academy of Health Sciences, Kathmandu, Nepal.
authors.forename: Sabina
authors.initials: S
authors.lastname: Dongol
authors.affiliation: The Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam.
authors.forename: Nga
authors.initials: N
authors.lastname: Tran Vu Thieu
authors.affiliation: The Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam.
authors.forename: Duy
authors.initials: D
authors.lastname: Pham Thanh
authors.affiliation: The Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam.
authors.forename: Dung
authors.initials: D
authors.lastname: Tran Thi Ngoc
authors.affiliation: The Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam.
authors.forename: Phat
authors.initials: P
authors.lastname: Voong Vinh
authors.affiliation: NERC Centre for Ecology and Hydrology, Wallingford, Oxfordshire, United Kingdom.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Singer
authors.affiliation: The Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, United Kingdom.
authors.forename: Julian
authors.initials: J
authors.lastname: Parkhill
authors.affiliation: The Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam.|Centre for Tropical Medicine, Oxford University, Oxford, United Kingdom.
authors.forename: Guy
authors.initials: G
authors.lastname: Thwaites
authors.affiliation: Oxford University Clinical Research Unit, Patan Academy of Health Sciences, Kathmandu, Nepal.
authors.forename: Buddha
authors.initials: B
authors.lastname: Basnyat
authors.affiliation: MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, United Kingdom.
authors.forename: Neil
authors.initials: N
authors.lastname: Ferguson
authors.affiliation: The Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam.|Centre for Tropical Medicine, Oxford University, Oxford, United Kingdom.|The London School of Hygiene and Tropical Medicine, London, United Kingdom.
authors.forename: Stephen
authors.initials: S
authors.lastname: Baker
mesh_terms: D002947:Cities; D004269:DNA, Bacterial / Q000235:genetics; D005243:Feces / Q000382:microbiology*; D006801:Humans; D009390:Nepal; D010284:Paratyphoid Fever / Q000453:epidemiology / Q000382:microbiology; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D012482:Salmonella paratyphi A / Q000302:isolation & purification*; D012485:Salmonella typhi / Q000302:isolation & purification*; D014435:Typhoid Fever / Q000453:epidemiology / Q000382:microbiology; D014871:Water Microbiology; D014881:Water Supply / Q000592:standards*
chemical_list: D004269:DNA, Bacterial; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S