Schistosomiasis japonicum in Indonesia: Progress and Surveillance Needs in Verge-of-Elimination Settings

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript is more of a report on the current status of schistosomiasis in Indonesia rather than a typical research study. Thus, some of the usual aspects of research papers (detailed materials and methods, data analysis plan, statistics) do not really apply. In general, it relays the current situation and considerations to achieve interruption of schistosomiasis transmission and is informative for the reader. Nevertheless, there are a number of ways in which the manuscript could be improved:

--It would be very helpful to know the sample sizes for Figure 1 and Table 1. The reliability of the data is very different if the number of data points is 25 versus 250 versus 2500. Error bars for the data in the figure and confidence intervals for the table would also be helpful (i.e, is there a great deal of variation between villages or are they somewhat similar across the endemic area?). Similarly, for the human data, the age-prevalence curves of the infected individuals would be informative as it may be different from most schistosomiasis endemic areas due to the large impact of animal infections. Also, are there any occupational groups that are more likely to be infected, such as farmers. Providing such information gives the reader a better picture of the overall infection situation.

--what age group(s) received MDA? In most countries, MDA is targeted to school aged children. Is this also the case in Indonesia or is the MDA available to everyone in the community? 

--what methods are used to diagnose infection in animals? Do infected domestic animals get treated? If so, how often are they surveyed, what is the coverage of the surveys, and how often do they get treated?

--the authors mention a recombinant antigen ELISA (lines 176-178) but provide no reference for this ELISA or its performance characteristics (e.g., sensitivity and specificity) or whether the test has been validated in local laboratories. As the program moves forward, it is critical that laboratory work for diagnosis, whether by parasitology, serology, or molecular methods (PCR) is properly implemented with staff competency and proficiency testing in place so that results are reliable and any dossier will be approved by reviewers. Without the proper laboratory quality assurances in place, elimination will not be verified.

--how well do the control programs for humans, animals, and environmental (snails) sectors work together? As the authors rightly indicate, the zoonotic nature of S. japonicum makes elimination even more difficult than it is for schistosome species where humans are the primary definitive host. Are the drugs and dosing regimens for treating animals present in Indonesia? They are absent in most places with zoonotic infection. If they are not currently available in Indonesia, an important component of work to be conducted in the immediate future is to determine how to treat domestic animals for schistosomiasis. The authors need to comment on the current status of animal treatments in the manuscript.

It may be that the life cycle of schistosomiasis in Indonesia is primarily maintained in animals with humans being more of an accidental host that does not contribute as much to the maintenance of transmission. Thus, interrupting transmission will not be possible by intervening with humans alone and may differ greatly than countries where humans are the primary driver of mammalian transmission. The authors should address what alternative, or additional strategies may be needed to interrupt transmission of schistosomiasis in Indonesia. 

line 30--confirmation of interruption of transmission is verification, not validation

lines 43-45--schistosome infection only leads to severe disease in some individuals, usually those with extended, heavy intensity infections. What are the clinical manifestations of schistosomiasis in Indonesia. Presumably, they are rather mild, which may make it difficult to identify infected individuals and/or convince the population of the value of continued MDA.     

Comments on the Quality of English Language

the English is mostly fine, there are just a few mistakes:

--line 60--"met" should probably be "meeting"

--line 61--"documented focal" doesn't really make sense and should be revised

--line 129-130-- there ARE no personal identifiers

--line 224--cercaria are THE infections form, not "an" infectious form of the parasite

Author Response

Comment 1: It would be very helpful to know the sample sizes for Figure 1 and Table 1. The reliability of the data is very different if the number of data points is 25 versus 250 versus 2500. Error bars for the data in the figure and confidence intervals for the table would also be helpful (i.e, is there a great deal of variation between villages or are they somewhat similar across the endemic area?). Similarly, for the human data, the age-prevalence curves of the infected individuals would be informative as it may be different from most schistosomiasis endemic areas due to the large impact of animal infections. Also, are there any occupational groups that are more likely to be infected, such as farmers. Providing such information gives the reader a better picture of the overall infection situation.

Response 1: Thank you for your suggestion and detailed comments. We have revised the manuscript accordingly to improve transparency regarding sample sizes, data reliability and heterogeneity, and to better characterise human infection patterns within the constrains of available routine surveillance data at national level.

• First, annual sample sizes are now explicitly reported in Table 1, which summarises the number of sample examined, number positive, prevalence estimates, and 95% confidence intervals for each survey (section 3.1; Table 1; line 171). Annual sample sizes ranged from approximately 14,000 to over 21,000 individuals, thereby addressing concerns regarding the robustness and comparability of prevalence estimates across years.
• Second, to illustrate variation between villages, we added two complementary figures: a village level heatmap showing spatial and temporal heterogeneity in prevalence across endemic villages (Figure 3; line 196 ), and box-and-whisker plots (Figure 4; line 205) summarising the annual distribution of village-level prevalence (Figure 3). Together, they demonstrate substantial between village heterogeneity in selected years, despite low national prevalence, and serve as a visual analogue to error bars at the aggregated level.
• Third, regarding error bars in Figure 1, we decided to present confidence intervals in Table 1 rather than overlaying them on the national trend figure, as the figure is intended to illustrate programme-level trends in prevalence and MDA coverage, while the table provides the appropriate statistical detail interpretation of uncertainty.
• Regarding age-prevalence curve and occupational risk, such analyses could not be conducted because routine surveillance data available in the ministry of Health (national level) are collected and reported in aggregated form and do not include individual-level age stratification or occupational information. We have clarified this limitation in the manuscript (Section 4.5; line 558) and highlighted the need for more granular data collection in near-elimination settings as a future surveillance priority (Sections 3.1 and 4.4)

Comment 2: what age group(s) received MDA? In most countries, MDA is targeted to school aged children. Is this also the case in Indonesia or is the MDA available to everyone in the community? 

Response 2: Thank you for this important observation. In Indonesia, MDA for schistosomiasis is community-wide rather than limited to school aged children (SAC). As clarified in the revised manuscript (section 3.1; line 145), MDA with praziquantel targets all individuals aged six years and above residing in endemic villages, with exception of pregnant women and individuals with severe illness. This eligibility reflects the zoonotic nature of schistosomiasis transmission in Indonesia and the recognition that adults may contribute to ongoing transmission risks due to occupationally exposed population.

Comment 3: what methods are used to diagnose infection in animals? Do infected domestic animals get treated? If so, how often are they surveyed, what is the coverage of the surveys, and how often do they get treated?

Response 3: Thank you for the question. Animal infection with Schistosoma japonicum in Indonesia is diagnosed primarily through parasitological stool examination. Surveillance of animal reservoirs (including cattle, buffaloes, pigs, dogs, and rodents) is mandated under the national schistosomiasis eradication framework and implemented by the Maros Veterinary Research Centre under the Ministry of Agriculture as part of zoonotic disease surveillance. However, animal surveillance is irregular, under-resourced, and inconsistent across endemic areas. While treatment of livestock is recognised as a key intervention, systematic Praziquantel treatment for animals has not yet been implemented at scale, largely due to logistical constraints as the formulation of Praziquantel for cattle is not available in Indonesia.

The animal surveys conducted used a purposive sampling method for domesticated animals owned by people who provided consent for the survey, hence only covering certain proportion of the animal population. Positive samples were treated using combination drug that contains Praziquantel and Albendazole (Section 3.2; line 223-240) (brand name examples of Nilzan® or Albipraz®).

Comment 4: the authors mention a recombinant antigen ELISA (lines 176-178) but provide no reference for this ELISA or its performance characteristics (e.g., sensitivity and specificity) or whether the test has been validated in local laboratories. As the program moves forward, it is critical that laboratory work for diagnosis, whether by parasitology, serology, or molecular methods (PCR) is properly implemented with staff competency and proficiency testing in place so that results are reliable and any dossier will be approved by reviewers. Without the proper laboratory quality assurances in place, elimination will not be verified.

Response 4: Thank you for your comments. We agree with the reviewer and have clarified this in the revised manuscript (section 3.1; line 214-221). The recombinant antigen ELISA (RA-ELISA) was introduced in Indonesia in 2023 as a screening tool to improve sensitivity in near-elimination settings, particularly where Kato–Katz has reduced sensitivity at low prevalence levels. At present, the RA-ELISA method is undergoing study for its performance in the diagnosis of schistosomiasis japonicum in endemic areas in Indonesia by other institutions, and that formal nationwide laboratory quality assurance systems (including external proficiency testing) for ELISA and molecular diagnostics are not yet fully institutionalised in the national public health laboratory system. We hope that the results from the RA-ELISA study be published soon to provide evidence-guided programme in the near future.

Comment 5: how well do the control programs for humans, animals, and environmental (snails) sectors work together? As the authors rightly indicate, the zoonotic nature of S. japonicum makes elimination even more difficult than it is for schistosome species where humans are the primary definitive host. Are the drugs and dosing regimens for treating animals present in Indonesia? They are absent in most places with zoonotic infection. If they are not currently available in Indonesia, an important component of work to be conducted in the immediate future is to determine how to treat domestic animals for schistosomiasis. The authors need to comment on the current status of animal treatments in the manuscript.

Response 5:  Thank you for the comments and suggestions. Indonesia’s schistosomiasis programme is formally designed as a multisectoral One Health programme, involving the health, agriculture, public works, environment, and village development sectors, as mandated under Ministerial Regulation No. 19 Year 2018. In practice, however, coordination remains uneven, with human MDA and snail control more consistently implemented than veterinary interventions. Currently, standardised drug formulation of Praziquantel (single-drug formulation) for domestic animals is not available in Indonesia. We have put this information in the revised manuscript accordingly (section 3.2; line 256-269).

Comment 6: It may be that the life cycle of schistosomiasis in Indonesia is primarily maintained in animals with humans being more of an accidental host that does not contribute as much to the maintenance of transmission. Thus, interrupting transmission will not be possible by intervening with humans alone and may differ greatly than countries where humans are the primary driver of mammalian transmission. The authors should address what alternative, or additional strategies may be needed to interrupt transmission of schistosomiasis in Indonesia. 

Response 6:  We fully agree with the reviewer that in Indonesia, schistosomiasis transmission is likely maintained primarily through animal reservoirs and infected snail habitats, with humans acting largely as incidental or accidental hosts. In such zoonotic settings, interventions focused solely on human MDA are unlikely to be sufficient to interrupt transmission and differ substantially from strategies used in settings where humans are the primary drivers of transmission.

We have addressed this point explicitly in the “Next Steps” section (Section 4.4, lines 525–546) of the revised manuscript. In this section, we discuss the need for alternative and complementary strategies to interrupt transmission in Indonesia, including integrated snail control through environmental modification and targeted mollusciciding, strengthened surveillance and management of animal reservoirs, improvements in water, sanitation, and hygiene (WASH) infrastructure, and community-based environmental and livestock management, in line with the National Roadmap on Schistosomiasis Eradication.

Comment 7 (language):

--line 60--"met" should probably be "meeting"

--line 61--"documented focal" doesn't really make sense and should be revised

--line 129-130-- there ARE no personal identifiers

--line 224--cercaria are THE infections form, not "an" infectious form of the parasite

Response 7 (language):

• Line 60: Met was revised into meeting
• Line 61: In the Philippines, infection remains focal and low in intensity... (revised)
• Line 136: There ARE no personal identifiers (revised)
• Line 275: The snails release a large number of cercariae, the infectious form of the parasite (revised)

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This review article provides a clear explanation of schistosomiasis control in Indonesia, covering its history, past efforts and the current situation, as well as the challenges involved. It provides valuable insights for readers in Asia, as well as for individuals interested in schistosomiasis control in Africa, the Middle East, and South America, making it an excellent resource. I have one minor point that should be addressed in the article, as follows. Including a map showing the location of Central Sulawesi Island within Indonesia and the areas on the island where schistosomiasis is endemic would provide readers with more tangible information.

Author Response

Comment 1: This review article provides a clear explanation of schistosomiasis control in Indonesia, covering its history, past efforts and the current situation, as well as the challenges involved. It provides valuable insights for readers in Asia, as well as for individuals interested in schistosomiasis control in Africa, the Middle East, and South America, making it an excellent resource. I have one minor point that should be addressed in the article, as follows. Including a map showing the location of Central Sulawesi Island within Indonesia and the areas on the island where schistosomiasis is endemic would provide readers with more tangible information.

Response 1: We thank the reviewer for the positive assessment of the manuscript and for this helpful suggestion. We agree that a map would enhance the clarity and accessibility of the manuscript by providing geographic context for readers.

In response, we have added a new figure illustrating the location of Central Sulawesi within Indonesia and the spatial distribution of schistosomiasis-endemic areas on the island (line 99). This figure has been incorporated into the revised manuscript as Figure 1 and is referenced in the Introduction section. We believe this addition provides readers with clearer visualisation of the endemic setting and strengthens the overall presentation of the study.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Comments and Suggestions for Authors

 

This manuscript examines Indonesia's progress in eliminating Schistosoma japonicum transmission by analysing a decade of surveillance data from two endemic districts in central Sulawesi. The authors combine data on human prevalence with programme reports on mass drug administration, animal reservoir surveillance, and snail surveys to assess readiness for transmission interruption in a near-elimination context. The study highlights that, although human infections remain low, ongoing transmission via animal reservoirs and intermediate hosts continues to be a major obstacle. The authors also identified significant weaknesses in surveillance systems, including limited diagnostic sensitivity, inconsistent malacological surveys, and fragmented reporting. This work highlights the need for enhanced surveillance strategies based on the One Health principle and digital data systems to support sustainable elimination and final certification of transmission interruption.

 

This article is interesting. Here are a few minor revisions:

 

Point 1 : Line 115 I suggest that authors provide an illustrative map of the study areas.

Point 2 : Line 203 – 206 Why did the authors present monitoring data on animal populations only from 2018 onwards (Table 1) ?

Point 3 : Please refer to Table 2 in the relevant paragraph (lines 206 to 215).

Point 4 : Line 240-241 Please cite the reference.

Point 5 : The discussion needs to be rewritten. It is too detailed, which could obscure the most important information. I suggest reducing it to at least one third of its current length.

It would be useful to add a final short paragraph outlining the limitations of the study.

 

 

Best regards,

 

Author Response

Comment 1: Line 115 I suggest that authors provide an illustrative map of the study areas.

Response 1: We thank the reviewer for this helpful suggestion. In response, we have added an illustrative map showing the location of the study areas, including the position of Central Sulawesi within Indonesia and the distribution of schistosomiasis-endemic villages. This map has been incorporated into the revised manuscript as Figure 1 (line 99) and is referenced in the corresponding section of the text.

Comment 2: Line 203 – 206 Why did the authors present monitoring data on animal populations only from 2018 onwards (Table 1)?

Response 2: We thank the reviewer for this question. Monitoring data on animal populations are presented from 2018 onwards because systematic and standardised animal surveillance data were only consistently available from that year. Earlier data were either not routinely collected or were incomplete and not comparable across years. We have clarified this point in the revised manuscript (Section 3.2; line 223-240) to explain the temporal scope of the animal surveillance data presented.

Comment 3: Please refer to Table 2 in the relevant paragraph (lines 206 to 215)

Response 3: We thank the reviewer for this helpful suggestion. We have revised the manuscript to explicitly refer to Table 2 in the relevant paragraph (Lines 206–215), ensuring that the presented results are clearly linked to the corresponding table.

Comment 4: Line 240-241 Please cite the reference.

Response 4: We thank the reviewer for this comment. As the information presented is derived exclusively from national routine surveillance records maintained by the Ministry of Health and not from a published source, we have revised the text to clearly attribute these data to programme surveillance rather than adding an external reference (Line 237-238).

Comment 5: The discussion needs to be rewritten. It is too detailed, which could obscure the most important information. I suggest reducing it to at least one third of its current length.

Response 5: We thank the reviewer for this comment and for the suggestion to further shorten the Discussion. We respectfully disagree that the Discussion should be reduced to one third of its current length.

This manuscript is intended as a research article that synthesises long-term programme experience, routine surveillance findings, and multisectoral control efforts in a complex zoonotic transmission setting. A more detailed Discussion is necessary to adequately contextualise the findings, explain the observed differences between human, animal, and snail surveillance data, and articulate their implications for schistosomiasis elimination in Indonesia. Substantially reducing the length of the Discussion risks oversimplifying these interrelated issues and obscuring key messages that are central to the objectives of the review.

We have therefore retained the current structure and level of detail in the Discussion to ensure completeness and clarity for readers, particularly programme managers and policy-makers working in similar zoonotic settings.

Comment 6: It would be useful to add a final short paragraph outlining the limitations of the study.

Response 6: We thank the reviewer for this helpful suggestion. As suggested, a paragraph outlining the limitations of the study has now been added to the manuscript and is presented in Section 4.5 (line 557)

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The revisions the authors have made have greatly improved the quality of the manuscript. The map (Fig 1) is especially helpful. Although it does bring up a couple more minor questions/editing suggestions: 

1. is it possible to denote which areas are in Poso and which are in Sigi?
2. there are 7 areas with no color, 2 of which are adjacent to areas with >0% prevalence. What is known about these areas? Are there just no data available? Is the program sure that there is no transmission in these areas? 

Section 2.2 is titled: "Ethical Considerations and the Use of Artificial Intelligence (AI)" but there is no mention of AI in the following paragraph. The authors could either include something here that was inadvertently left out or remove the mention of AI in the title. 

The median lines in Figure 4 are very difficult to see. Is there a way to make them black or otherwise make them more visible? There is also an "X" in each box that is very difficult to see. What does it denote? It is not mentioned in the legend. 

Going forward, how feasible would it be to use captured rodents as sentinels for the different villages? As more people and animals are treated with praziquantel, eggs going into the environment should decrease, leading to fewer infected snails (along with snail control efforts), leading to fewer infections in the environment. Capturing rodents and checking them for infection by looking for eggs in their livers may be a low-cost way to monitor force of infection in the different areas. It is usually quite easy to see evidence of eggs in livers with the naked eye in dissected rodents. 

Author Response

Comment 1: The revisions the authors have made have greatly improved the quality of the manuscript. The map (Fig 1) is especially helpful. Although it does bring up a couple more minor questions/editing suggestions:

• is it possible to denote which areas are in Poso and which are in Sigi?
• there are 7 areas with no color, 2 of which are adjacent to areas with >0% prevalence. What is known about these areas? Are there just no data available? Is the program sure that there is no transmission in these areas?

Response 1: We sincerely thank the reviewer for the positive feedback and for the constructive suggestions regarding Figure 1.

Denotation of Poso and Sigi districts

We have revised Figure 1 to clearly distinguish endemic villages by district (line 101). Specifically, endemic villages in Poso District (n = 23) are now shown in dark teal, while endemic villages in Sigi District (n = 5) are shown in burnt orange. The figure legend has been updated accordingly to explicitly indicate districts and villages distribution (see revised caption of Figure 1 in the manuscript). We hope that the modification improves geographic clarity and allows readers to immediately distinguish the two endemic districts within Central Sulawesi.

 

Clarification of areas shown in white (no colour)

We appreciate the reviewer’s important observation regarding the seven areas displayed in white, including two that are adjacent to villages with >0% prevalence. We would like to clarify that:

• These white areas represent non-endemic villages within the same geographical landscape (province), not endemic villages with missing data.
• They are not included among the 28 villages officially designated as endemic under the national schistosomiasis elimination programme.
• Routine surveillance activities (including stool surveys and MDA) are formally implemented only in these 28 endemic villages.
• Based on available routine disease surveillance data, no indigenous transmission and intermediate snails has been detected/found in the villages shown in white.

While the absence of detected snail habitats and routine human cases provides reassurance, we acknowledge that proximity to endemic villages warrants continued vigilance. As discussed in the manuscript, strengthening risk-based, ecologically informed surveillance remains critical in near-elimination settings to ensure that any potential emergence of new transmission foci is rapidly detected.

To improve clarity, we have revised the figure caption to explicitly state that villages shown in white represent non-endemic villages within the same geographical areas, where no indigenous transmission has been detected based on routine disease surveillance (see revised Figure 1 caption (line 102-108).

Comment 2: Section 2.2 is titled: "Ethical Considerations and the Use of Artificial Intelligence (AI)" but there is no mention of AI in the following paragraph. The authors could either include something here that was inadvertently left out or remove the mention of AI in the title.

Response 2:  We thank the reviewer for carefully noting this inconsistency.

Upon revision, we have removed the reference to Artificial Intelligence (AI) from the title of Section 2.2 to ensure alignment with the actual content of the manuscript. There was no AI-based methods were used in data collection, analysis, interpretation, or generation of results. In line with the journal’s writing guidance, the use of generative AI solely for superficial text editing does not require formal declaration. Therefore, to avoid unnecessary confusion and to maintain methodological transparency, the section has been retitled to “Ethical Considerations” only.

Comment 3: The median lines in Figure 4 are very difficult to see. Is there a way to make them black or otherwise make them more visible? There is also an "X" in each box that is very difficult to see. What does it denote? It is not mentioned in the legend.

Response 3: We thank and appreciate the reviewer for this helpful observation regarding the clarity of Figure 4. In the revised manuscript (line 211), we have improved the visual clarity of the box-and-whisker plots by:

• Enhancing the median lines. The median lines have been reformatted in solid black with increased line thickness to improve visibility and ensure clear distinction from the box boundaries.
• Removing the “X” marker. Upon review, we decided to remove the “X” marker entirely to avoid visual clutter and potential confusion. Previously, the marker represented the mean village-level prevalence; however, because the box-and-whisker plot already summarises distribution through the median, interquartile range, and whiskers, inclusion of the mean was not essential for interpretation. Removing the marker has improved overall readability and figure clarity.

Comment 4: Going forward, how feasible would it be to use captured rodents as sentinels for the different villages? As more people and animals are treated with praziquantel, eggs going into the environment should decrease, leading to fewer infected snails (along with snail control efforts), leading to fewer infections in the environment. Capturing rodents and checking them for infection by looking for eggs in their livers may be a low-cost way to monitor force of infection in the different areas. It is usually quite easy to see evidence of eggs in livers with the naked eye in dissected rodents.

Response 4: We sincerely thank the reviewer for this important and forward-looking suggestion.

We agree that the use of rodents as proxy indicators of environmental transmission intensity is epidemiologically appropriate in zoonotic settings such as Indonesia. As shown in our 2023 survey results, rodent infection rates were substantial (overall 31.6%), reinforcing their role as important reservoir hosts and potential indicators of ongoing transmission.

In the revised manuscript, we have expanded the Discussion (Sections 4.2 and 4.4) to acknowledge the potential strategic value of sentinel rodent surveillance in near-elimination settings, particularly where human prevalence declines and stool-based surveillance becomes less sensitive. Monitoring infection in rodents could provide a practical proxy for environmental force of infection and help detect residual transmission earlier than human surveys alone.

However, we also clarified important institutional and operational considerations. According to the National Roadmap for Schistosomiasis Eradication, surveillance of animal reservoirs—including rodents—is mandated to be led by non-human health sectors under the broader One Health framework. In practice, similar to animal surveillance, rodent surveillance has received limited operational attention in recent years.

At present, the Ministry of Health—particularly through its vector control unit—technically possesses the capacity to conduct rodent trapping and examination. However, because rodent reservoir surveillance falls outside the formal mandate of the Ministry of Health, allocating dedicated programme budgets for this activity has been challenging. This institutional misalignment has contributed to inconsistent implementation despite recognised epidemiological importance.

Looking forward, we emphasise in the revised manuscript that effective operationalisation of the national roadmap—including integrated surveillance under one health framework—will be critical (line 550-556). Routine rodent surveillance should ideally be implemented in accordance with the designated responsibilities of the relevant ministries or agencies to ensure sustainability, regulatory alignment, and proper integration within a One Health surveillance architecture.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

"Schistosomiasis japonicum in Indonesia: Progress and Surveillance Needs on the Verge of Elimination Settings" by Achmad Naufal Azhari, et al.

I feel that I should congratulate all the authors for their significant work in preparation of a revised manuscript. I will therefore recommend the acceptance of this R1 MS to the Editor.

Author Response

Comment 1: "Schistosomiasis japonicum in Indonesia: Progress and Surveillance Needs on the Verge of Elimination Settings" by Achmad Naufal Azhari, et al.

I feel that I should congratulate all the authors for their significant work in preparation of a revised manuscript. I will therefore recommend the acceptance of this R1 MS to the Editor.

Response 1: We sincerely thank and appreciate the reviewer for the generous and encouraging feedback. We highly appreciate the time and expertise invested in reviewing our manuscript and providing constructive comments throughout the revision process.

The reviewer’s insights have substantially strengthened the clarity, methodological transparency, and policy relevance of the manuscript. We are grateful for the positive evaluation and recommendation for acceptance.

On behalf of all co-authors, we thank the reviewer for their thoughtful engagement with our work.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Comments and Suggestions for Authors

 

This manuscript examines Indonesia's progress in eliminating Schistosoma japonicum transmission by analysing a decade of surveillance data from two endemic districts in central Sulawesi. The authors combine data on human prevalence with programme reports on mass drug administration, animal reservoir surveillance, and snail surveys to assess readiness for transmission interruption in a near-elimination context. The study highlights that, although human infections remain low, ongoing transmission via animal reservoirs and intermediate hosts continues to be a major obstacle. The authors also identified significant weaknesses in surveillance systems, including limited diagnostic sensitivity, inconsistent malacological surveys, and fragmented reporting. This work highlights the need for enhanced surveillance strategies based on the One Health principle and digital data systems to support sustainable elimination and final certification of transmission interruption.

 

This article is interesting.

Here are a few minor revisions :

 

- Figures 1, 2, 3 and 4, as well as Tables 1 and 3, are not mentioned in the body of the text. Please cite them in the appropriate paragraphs and insert them immediately after the passage where they are referenced.

- Line 291-292 : Please cite the reference.

- The discussion needs to be rewritten. It is too detailed, which could obscure the most important information. I suggest reducing it to at least one-third of its current length.

 

 

Best regards,

 

Author Response

Comment 1: Figures 1, 2, 3 and 4, as well as Tables 1 and 3, are not mentioned in the body of the text. Please cite them in the appropriate paragraphs and insert them immediately after the passage where they are referenced.

Response 1: We thank the reviewer for this helpful observation. In the revised manuscript, all figures (Figures 1–4) and tables (Tables 1 and 3) have now been explicitly cited in the main body of the text at appropriate analytical points within the Introduction and Results section. We have also ensured that each figure and table is positioned immediately after its first citation, in accordance with the journal’s formatting requirements.

Specifically, Figure 1 is now cited in the Introduction when describing the geographic distribution of the 28 endemic villages (line 65-68). Figure 2 (line 168-170) and Table 1 (line 182-183) are referenced in Section 3.1 in relation to temporal trends in human prevalence and MDA coverage. Figures 3 (line 189-198) and 4 (line 203-210) are cited in the subsection describing village-level heterogeneity and distributional patterns over time. Table 3 is now cited in Section 3.2 when presenting rodent surveillance findings (line 268). These revisions improve clarity, strengthen the analytical narrative, and ensure consistency between the text and visual materials.

Comment 2: Line 291-292 :Please cite the reference

Response 2:  We thank the reviewer for highlighting the need to clarify the source of this information. The reported reduction in snail foci from 301 in 2017 to 224 in 2021 is based on routine monitoring data from the National NTD Programme, Ministry of Health, Republic of Indonesia (line 312-313). These data form part of the national surveillance and programme records described in Section 2.1 (Study Design and Data Management), which include epidemiological and operational information compiled from 2015–2025.

Comment 3: The discussion needs to be rewritten. It is too detailed, which could obscure the most important information. I suggest reducing it to at least one-third of its current length.

Response 3: We thank the reviewer for reiterating this important comment. We carefully re-examined the Discussion section with attention to clarity, focus, and conciseness. In the revised manuscript, we have streamlined several paragraphs to reduce repetition, improved transitions between subsections, and sharpened key messages to enhance readability.

However, we respectfully maintain that a substantial reduction to one-third of the current length would limit the manuscript’s ability to adequately interpret the findings within the complex zoonotic transmission context of S. japonicum in Indonesia. The Discussion intentionally integrates human, animal, and snail surveillance data and situates them within regional and global elimination experiences. This level of detail is necessary to explain observed heterogeneity, methodological constraints, and operational implications in near-elimination settings.

Given that this manuscript synthesises a decade of programme data to inform elimination readiness in a zoonotic environment, we believe that maintaining a structured, thematically organised Discussion ensures clarity for researchers, programme managers, and policy-makers working in similar contexts. We have therefore refined the section for improved focus while preserving the analytical depth required to support the manuscript’s objectives.

Author Response File: Author Response.docx