Biomarkers of Toxins in Improved Drinking Water and Diarrhea Patients of South Wollo Communities, Northern Ethiopia
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Date
2022-04
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Addis Ababa University
Abstract
The world's most vulnerable communities frequently drink contaminated water, which is linked to
a variety of public health issues. Escherichia coli toxins are the most common types of
contaminants found in association with disease in E. coli bacteria. They are found in nearly all
pathogenic E. coli bacteria either released from the bacteria or E. coli cell or both transmitted via
the feco-oral route. The objective was to evaluate the safety of improved water supplies using
toxins as a biomarker and correlate with the toxins found in patient stools, and identify gaps
between water quality and the global classification of improved water supplies in the South Wollo
zone, Ethiopia. This dissertation reports the results of a laboratory-based cross-sectional
study conducted in South Wollo, Ethiopia, from January 2019 to June 2020. Two
hundred forty-eight samples of household water and patient stool were collected (in a 1:1
match) and toxins were tested using polymerase chain reaction (PCR). The targeted
toxins used were (enteroaggregative E. coli heat-stable enterotoxin 1 (EAST1), heat-stable
(Sta); shiga-like toxin 1 (Stx1), shiga-like toxin 2 (Stx2), and heat-liable (LT)), which cause
diarrhea when people drink contaminated water. A survey questionnaire was used to
gather information on the types of water sources, as well as the knowledge and practices
of the respondents about household water treatment methods. To analyze the data and
examine the relationship between the variables, descriptive statistics, Chi-square (χ2),
Fisher’s exact test, logistic regression, and Pearson’s bivariate correlation coefficients
were used. In general, 24% of households had positive results from both water and stool
samples, 63% [Confidence Interval (CI): 55- 67%] had positive results from water
samples only, and 46% [CI: 37- 49%] had positive results from only stool frequently, with 33% in the water and 38% in the stool. Frequently founded contaminants
in household water brought from improved water sources were the toxins ESAT1, Stx1,
and LT, with Sta the least founded (2%). There were fewer (13%) toxins detected in
shallow groundwater sources than in piped water, a statistically significant difference
(P=0.031). There was a lower proportion of toxins detected in those who did not know
about and used cloth filters than in those who did, and the negative relationship is
statistically significant (P=0.017). Approximately one-third of the improved water
services sampled, which are considered ‘functional’ by international standards, do not
provide potable water due to fecal and toxin contaminants. There was a significant
positive correlation (r = 0.412) between toxins in the stool and toxins in the water (P <
0.05). The findings indicate that toxin biomarkers can be used to monitor water safety.
Water quality parameters are not currently considered in the classification of basic water
services. This suggests that international efforts to address SDG 6 should incorporate
water quality and its indicators as a key parameter to better track international progress
towards ‘clean water and sanitation’ efforts. More research is needed to determine the
sources of pathogenic microbial markers that cause water-related diseases, such as
diarrhea, as well as focus areas for water contamination prevention.samples for
toxins. Out of the five toxins examined, EAST1 was the one that was found the most