Abstract
Sanitary risk inspection protocols are often used to identify contamination hazards at water sources; however, different observers sometimes struggle to record hazards consistently. This study aimed to assess the effect of inter-observer variation in hazard observations on the strength of relationships between observed hazards and the bacterial contamination of water sources, particularly relationships with animal-related hazards. In a longitudinal study, five surveyors independently recorded hazards at 93 water sources used by 234 households in Siaya County, Kenya, in both wet and dry seasons. One surveyor collected samples from sources for subsequent Escherichia coli and intestinal enterococci testing. The relationship between each surveyor’s hazard observations and high bacterial contamination was examined using logistic regression. After controlling for water source type and preceding rainfall; percentage scores for animal-related hazards were significantly related to high contamination with enterococci and E. coli for one surveyor (odds ratio 1.02; 95% confidence intervals 1.00–1.03 for both parameters), but not for the remaining four surveyors. The relationship between observed contamination hazards and the microbiological contamination of water sources is sensitive to variation in hazard recording between surveyors. Sanitary risk protocols should be designed to enable robust and consistent observation of hazards.
Highlights
An estimated 1.8 billion people use faecally contaminated water, with 1.1 billion using drinking water that constitutes a ‘moderate’ risk (>10 colony-forming units (CFU)/100 mL of E. coli or thermotolerant coliforms per 100 mL) [1]
Separate models were fitted for E. coli and intestinal enterococci, with robust regression to account for clustering of bacteria counts where two samples were taken from the same source
Whilst almost all hazard scores were significantly related to high bacterial contamination in univariate analysis, after adjusting for source type, only the animal-related hazard score remained significant for both faecal indicator bacteria groups (Tables 2 and 3)
Summary
Joseph Okotto-Okotto 1 , Diogo Trajano Gomes da Silva 2 , Emmah Kwoba 3 , Samuel.M Thumbi 4,5,6 , Peggy Wanza 4 , Weiyu Yu 7 and Jim A. Paul G Allen School for Global Animal Health, Washington State University, P.O. Box 647090, Pullman, WA 99164, USA
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