ArticlePLoS neglected tropical diseases2023
Environmental sampling for typhoidal Salmonellas in household and surface waters in Nepal identifies potential transmission pathways.
Article in PLoS neglected tropical diseases, 2023. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 7 papers, 1 of them a synthesis that pooled it.
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7 citing papers in PubMed, 1 synthesis or guideline pooled it, 12 citations in OpenAlex.
- Systematic review on the laboratory methodology for conducting wastewater and environmental surveillance forFrontiers in public health · 2026Pooled it
- Multidrug-ResistantPolish journal of microbiology · 2026Review
- Rapid, low-cost colorimetric detection ofmBio · 2025Article
- Environmental surveillance for Salmonella Typhi to detect the typhoid burden in Yogyakarta, Indonesia.International journal of hygiene and environmental health · 2025Article
- Evaluation of Moore and grab sampling method for Salmonella Typhi detection in environmental samples in Ghana.PloS one · 2025Article
- Environmental surveillance for Salmonella Typhi in rivers and wastewater from an informal sewage network in Blantyre, Malawi.PLoS neglected tropical diseases · 2024Article
- Detection of Salmonella Typhi bacteriophages in surface waters as a scalable approach to environmental surveillance.PLoS neglected tropical diseases · 2024Article
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17 authors at 8 institutions in 5 countries.
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Abstract
introductionSalmonella Typhi and Salmonella Paratyphi, fecal-oral transmitted bacterium, have temporally and geographically heterogeneous pathways of transmission. Previous work in Kathmandu, Nepal implicated stone waterspouts as a dominant transmission pathway after 77% of samples tested positive for Salmonella Typhi and 70% for Salmonella Paratyphi. Due to a falling water table, these spouts no longer provide drinking water, but typhoid fever persists, and the question of the disease's dominant pathway of transmission remains unanswered.
methodsWe used environmental surveillance to detect Salmonella Typhi and Salmonella Paratyphi A DNA from potential sources of transmission. We collected 370, 1L drinking water samples from a population-based random sample of households in the Kathmandu and Kavre Districts of Nepal between February and October 2019. Between November 2019 and July 2021, we collected 380, 50mL river water samples from 19 sentinel sites on a monthly interval along the rivers leading through the Kathmandu and Kavre Districts. We processed drinking water samples using a single qPCR and processed river water samples using differential centrifugation and qPCR at 0 and after 16 hours of liquid culture enrichment. A 3-cycle threshold (Ct) decrease of Salmonella Typhi or Salmonella Paratyphi, pre- and post-enrichment, was used as evidence of growth. We also performed structured observations of human-environment interactions to understand pathways of potential exposure.
resultsAmong 370 drinking water samples, Salmonella Typhi was detected in 7 samples (1.8%) and Salmonella Paratyphi A was detected in 4 (1.0%) samples. Among 380 river water samples, Salmonella Typhi was detected in 171 (45%) and Salmonella Paratyphi A was detected in 152 (42%) samples. Samples located upstream of the Kathmandu city center were positive for Salmonella Typhi 12% of the time while samples from locations in and downstream were positive 58% and 67% of the time respectively. Individuals were observed bathing, washing clothes, and washing vegetables in the rivers. IMPLICATIONS: These results suggest that drinking water was not the dominant pathway of transmission of Salmonella Typhi and Salmonella Paratyphi A in the Kathmandu Valley in 2019. The high degree of river water contamination and its use for washing vegetables raises the possibility that river systems represent an important source of typhoid exposure in Kathmandu.
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