Quantitative microbial risk assessment of rural sanitation systems: with case studies from Fiji and Nepal

Abstract

Unsafe sanitation contributes to the transmission of several faecal-oral diseases through contaminated latrine surfaces, unwashed hands and other inadequate hygiene practices. While significant progress has been made on access to sanitation facilities, persistent sanitation-related infections in low to high human development index countries highlight the need to assess the safe use of sanitation facilities. This research examined the faecal pathogen transmission pathways at the front-end of rural sanitation systems in Fiji and Nepal, identifying the high-risk pathways and estimating human infection risks using Quantitative Microbial Risk Assessment (QMRA).

A mixed-method approach included sanitation surveys, observations, and latrine swab sampling to measure Escherichia coli densities. In Fiji, data were collected from 311 households from 29 rural communities, with an in-depth study of 12 households. In Nepal, analysis of national water, sanitation and hygiene survey (628 households) and an in-depth study of eight households were included. Despite the access to improved sanitation infrastructures in both Fiji and Nepal, findings emphasise the need to rigorously focus on latrine cleanliness, infrastructural maintenance and safe hygiene practices. The QMRA estimated infection risk for E. coli O157:H7 and rotavirus from hands contaminated with latrine surfaces. Three pathways were assessed: direct hand to mouth contact (Pathway 1), indirect ingestion via food (Pathway 2) and stored drinking water (Pathway 3). The major risk of E. coli O157:H7 was from ingestion via food (6%) and stored drinking water (5%), which highly elevated when food and stored drinking water had baseline contamination. Rotavirus scenario presented major risks for food (16%) and stored drinking water (13%). This study highlights the need for integrated multi-barrier approaches focusing on latrine cleanliness, maintenance and safe hygiene to reduce infection risks from latrine front-ends.