Review for 10.1186/s12876-022-02174-4 (2022)

Title: Fecal indicator bacteria along multiple environmental exposure pathways (water, food,
and soil) and intestinal parasites among children in the rural northwest Ethiopia
Version: 1 Date: 29 Nov 2021
Reviewer:  Nuhu Amin
Reviewer's report:
Thanks for the opportunity to review the manuscript. This is an important paper that highlighted
the links between environmental contamination and enteric diseases. I went through the
manuscript carefully and made some suggestions to improve the quality of the paper:
Abstract:
Methods:
Page 1, line 24: Put space after “E.” while writing E. coli (applicable for all)
Page 1, line 26: What do you mean by internal exposure?
Results:
Page 2, line 29:  “Enteric infection” You did not mention what method you used to determine
enteric infection of children?
Page 2, line 30:  How many samples were collected (N/n)? What was the denominator?
Page 2, line 33:  Briefly mention from where you have collected these samples?
Page 2, line 34:  How handwashing data was collected. If you want to report HW data in the
result section, you must report it in the method section.
Page 2, line 35:  Be consistent using the word “handwashing” or hand hygiene. You used
“handwashing” in the results section.
Page 2, lines 34-39:  How handwashing data was collected. If you want to report HW data in
the result section, you have to report it in the method section.
Conclusions:
The conclusion is not to the point. Rather than intervention only, the author should discuss
potential sources of the contamination (water, soil, etc.). For example, is it open defecation, poor
onsite sanitation or poor drainage/sewerage system?
Background
Page 2, lines 49-62: Paragraph 1 and 2 (lines 49-62) is too detailed. Make the burden of diseases
succinct and highlight the burden of the disease of Africa and Ethiopia if available.
Page2, lines 63-70: Not sure why children exposure appears here suddenly.
In the introduction it is important to highlight why this study is important? There are already
many studies conducted to explore child exposures in LMICs. Why this study needed despite
substantial evidences exist in recent literature?
Page3, lines 65: Space between infection and reference. (Applicable for all)
Page3, lines 76-79: Need sufficient justification for this activity. I request the author to search
related literature from LMICs (for example WASH-benefits study in Bangladesh and Kenya,
SaniPath environmental exposure studies etc.) and provide sufficient justification for these
activities.
Page3, lines 79-80: The objective is not clear.
Page3, lines 80-82: This sounds like methods
Page3, lines 81: Which framework have you used?
Methods:
I do not see any logical flows and chronological order of the methodology. This made the
manuscript challenging to understand. In addition, laboratory methods are merged with field
activities, and data collection/sample collection approaches are not described well.
Make subsection: Selection of study sites and selection of study participants under study design
and settings. Also add a study site map in the supplemental figure.
Page 4, line 86: Which season (dry or wet season) did you collect samples?
Sample size estimation: Merge the Sample size calculation with the Statistical analysis section
to maintain the chronological order of the method section. SS calculation section is too detailed.
It would be helpful if you provided a study flow chart and reduced the text.
Page 4, line 101: Define kebeles.
Briefly describe the approach of systematic random sampling. What tool was used? What were
the eligibility criteria? If two children were eligible, which children were selected from each
HH?
This information should be available in the study flowchart.
Page 4, lines 103-104: Before assessing exposure, add a subsection of “Selection of sampling
points with justification”. Define drinking water, ready-to-eat foods, and courtyard soil because
this also varies in a different context.
Page 4, line 105: Put justification; why you only choose these 3 environmental exposures? In
LMICS, environmental exposures are many?
You can see some recent examples here: https://www.sciencedirect.com/science/article/pii/
S0048969721063518
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0234364
Page 4, line 106: Describe Goddard FG approaches briefly and then start your method section.
Page 4, line 109-111: Add reference.
Also did you also explore:
•  Sources of drinking water
• Water treatment approach
• Have you measured free or residual chlorine/iron or other parameters of water? Why? why not?
Page 5, line 115: what do you mean by “small amount”? 1gm or to gm or 100 gm”?
Page 5, line 116: What types of plastic bags you used this is important to declare.
Page 5, line 118-120: I am wondering about the approach of stool sample collection from
children? Is it a feasible approach that the fieldworkers request the children to poop and they
did it? Clearly mention the practical approach of stool sample collection from children.
Also when (Morning or noon or evening) samples were collected?
Page 5, line 120-122: Where and who performed these activities?
Page 5, line 122-131: Make a separate section of the laboratory procedure.
Page 5, line 132: Need an appropriate heading of this section. Household data collection?
Page 6, line 145: You did not mention anything about the sample transportation and how they
maintain the QAQC of the samples during collection and transportation?
All laboratory analysis part should be in a separate section.
Results:
Page 8, line 217: How is handwashing information collected? I do not see anything in the method
section related to handwashing?
Page 8, line 228: I did not find this in the method section. This section is also poorly presented
in the result section.
• What do you mean by any type of latrine
•  What do you mean by “splashed domestic wastewater everywhere in the yard”
• What do you mean by “garbage”
Not sure if I missed the method of exploring animal excreta in the method section?
Page 9, line 233: What was the sources of water? Underground, surface water etc?
Page 10, line 274-275: This sentence does not make any sense
Page 10, line 280-282: This interpretation is quite technical. Make the result in simple and non-
technical language for the readers.
Page 11, line 284: I did not see any method to collect “open defecation” in the methods
Discussion:
Page 12, line 308: The discussion is not aligned with the main results of the study.
The author should describe the discussion as follows:
• Actual causes of this high infection among the children
• Discuss the infectious dose of each pathogen you found in the environmental samples.
• What are the primary sources of water and soil contamination
Page 12, line 312-315: Possible solution to limit the contamination: innovation, FSM, behavior
change communication to reduce open defecation.
If there are multiple studies on intestinal parasitic information among children <5 in Ethiopia,
why are you repeating this research? This is not clear. You have to use some of these previous
studies' data in the introduction.
Also, what about other studies in LMICs? It is better to put some comparisons in the discussion.