PONE-D-20-30800

Insecticide resistance status of indoor and outdoor resting malaria vectors in a highland and lowland site in Western Kenya

PLOS ONE

Dear Dr. Afrane,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please address the comments raised by the reviewers, and pay careful attention to the issue raised by reviewer 2 concerning the validity of the data with respect to the way the mosquitoes were collected i.e. is there clear differentiation between indoor and outdoor resting mosquitoes based on the way they were collected? 

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Reviewers' comments:

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Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Partly

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: No

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3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: No

Reviewer #2: No

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: My comments are below

Introduction

Line 73 to 75 « Despite the observed improvement in malaria incidence and prevalence in many parts of sub-Saharan Africa, transmission is increasing in several countries [2,3]. » I don’t think the term « improvement » is appropriate and the sentence doesn’t make sense

Line 80 to 81 « Insecticide resistance in malaria mosquitoes is linked to presence and increase in metabolic detoxification enzymes, target site insensitivity and behavioural resistance [11]. » the sentence is not clear can the author rephrase the sentence to improve understanding?

Line 84 to 86 « Detoxification enzyme systems that have been reported to confer resistance include three major families of enzymes; the cytochrome P450 monooxygenases, β-esterases, and the Glutathione S-transferases. » please write esterase as you are refering to enzymes families

Line 92 to 95 « The increasing levels of insecticide resistance in malaria mosquitoes have been associated with continuous exposure to insecticides in Long Lasting Insecticide Nets( LLINs) [23,24] and agro-chemicals such as pesticides due to the creation of selection pressures [25-27]. » The phrase is not clear and need to be rewritten to improve understanding

The introduction is not straight forward and is poorly written the authors need to revise this section carefully to improve understanding

Methods

Study sites

Line 120 « The study was carried out in the lowland site of Kisian (0.0749° S, 34.6663° E, 1,137m) in Kisumu county … » The geographical coordinates is not appropriate can the authors check for the correct coordinates ?

Line 127 to 128 « There is extensive use of agrochemicals on these farms which could have a potential role in the mediation of resistance to insecticides. » Are anopheline breeding habitats found in tobacco farms and what type of insecticides are used in these farms please provide more information. Please also say how frequent insecticides are sprayed in these farms. How distant are these farms from the village.

Mosquito sampling

Mosquitoes were collected in how many houses per site and outdoor places please include information

Line 156 to 160 « First filial generation (F1) females raised from field-collected adults that were resting either indoors or outdoors, that were 3-5 -day old, were tested for susceptibility using the standard WHO tube bioassays (WHO, 2016) against discriminating doses of five insecticides selected from three classes: (i) Pyrethroids - (0.05% deltamethrin, 0.75% permethrin and (0.05% Alphacypermethrin); and (ii) organophosphate - (5% malathion). » The author say they tested 5 insecticides only a list of four insecticide is provided please correct.

Line 166 to 167 « Mortality was defined as the inability of the mosquitoes to stand or to fly in a coordinated manner. » is this mortality or knock down effect please correct

Line 175 to 176 « After pre-exposure to PBO, the mosquitoes were immediately exposed to the three pyrethroids (deltamethrin, permethrin and alphacypermethrin) for an additional hour. » Where mosquitoes exposed to all three insecticides at once or seperately to each insecticide please clarify

Results

There are data missen in this part the author need to give the number of gravid and non gravid females collected outdoor and indoor in each site. They could also indicate the number collected during each season.

The number of mosquitoes tested for each insecticide need to be provided

Table 1

The authors say that the percentage is in bracket but it is not clear how they did the calculations of the percentage of An. funestus in Kisian 122(19%) in Kimaeti they also wrote 167 (23.16) can they provide explanation for their calculations or correct.

The author also need to check their calculations the row on An. arabiensis in Kisian the total in the column and line also need to be corrected.

Reviewer #2: Comments:

This study intends to show the insecticides resistance between indoors and outdoors resting vectors in highlands and lowlands

This study has a major drawback in methodology.

To start with the ecological behavior of An. gambiae s.l is to feed indoor and rest indoor for An. gambiae s.s. while for An. arabienses is feeding indoor and resting outdoor or feed outdoor and rest outdoors. Due to the wide coverage of the insecticide treated surfaces (LLINs and RS), mosquitoes have changed the feeding and resting behavior to forfeit the effect of the insecticides treated surfaces. Due to this, higher proportions have found to feed and rest outdoors regardless of the vector species.

Sampling:

The samplings of vectors were done indoor and outdoor. The vector after feeding indoor they get out to rest and search for oviposition site. This is indeed a challenge to mark that this mosquito was found resting outdoor while it fed indoor. The physiological and enzymatic dynamics in mosquitoes is mostly reflected by blood meal source. There is no barrier between indoor and outdoor resting populations hence free mating is possible. In first place, authors should be aware that resistance is genetical and is clearly related age of the mosquito. These mosquitoes share breeding sited and feeding sources. The emerging young mosquitoes resting outdoor before searching for host. The outdoor collection is probably that it collected emerged and gravid mosquitoes searching for oviposition site. The methods were weak not to show the separation of population fed outdoor or indoor. So collection alone cannot provide a guarantee of the biochemical processes to be elevated by resting position.

I personally reject this paper as the basis used of outdoor and indoor resting have no barrier separation between the populations collected. Since resistance is genetical and biochemical process is influenced by blood meal sources. No evidence of where the mosquitoes fed (i.e. blood meal source). That was not shown so as to give the=at strong evidence.

This study can compare the enzyme changes and resistance and enzyme presentation between lowland and highland but not between indoor and outdoor resting mosquitoes

More specific comments are uploaded in attached document.

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Reviewer #1: No

Reviewer #2: No

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Attachments

Attachment

Submitted filename: comments.docx

Insecticide resistance status of indoor and outdoor resting malaria vectors in a highland and lowland site in Western Kenya

PONE-D-20-30800R1

Dear Dr. Afrane,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

Basil Brooke, PhD

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #2: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #2: I have realized that, all comments I raised in first place were all addressed in this revised version.

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7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #2: No