Epidemiological Investigation of Peste des Petits Ruminants in Bahrain
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis study investigated the status of Peste des Petits Ruminants (PPR) in Bahrain through serological surveillance and molecular testing. The results revealed significant seroprevalence in sheep and goats, and viral infection was currently not detected in the country. However, the high antibody rates in the Northern region bordering Saudi Arabia, where vaccination is practiced, suggests potential undocumented cross-border movement of animals remains a concern. The findings validate PPR control without vaccination in Bahrain, while highlight continuous monitoring particularly at border areas. Recommendations
1. Justify the small wild ruminant sample and discuss potential underrepresentation.
2. Sampling timelines should be described in the Methods.
3. Suggest to provide details on RT-PCR primer sequences, cycling conditions, and detection limit to strengthen reliability of negative results.
4. Add error bars to Figure 1.
5. Address potential false negative result in RT-PCR due to sample timing.
6. Contrast non-vaccination approach in Bahrain with regional vaccinated countries in Discussions.
Author Response
Here we present professional point-by-point response to your candid review comments, along with suggested manuscript changes.
Response to Reviewer Comments
Reviewer 1
Comment 1. Justify the small wild ruminant sample and discuss potential underrepresentation.
Response: We acknowledge the limited number of wild ruminants (n = 38). This reflects the small, confined, and managed population of wild ruminants, located in protected areas of Bahrain. Out of these protected areas, we sampled from the Al Areen Wildlife Park. As such, our sample proportionally represents the accessible population. We have clarified this in the Methods and Discussion.
Manuscript change: Added explanation in Methods (Sampling) and Discussion to highlight the restricted wildlife population and the representativeness of the sample.
Comment 2. Sampling timelines should be described in the Methods.
Response: We thank the reviewer for this suggestion. The sampling timelines have now been clearly specified: serological survey (March–September 2021) and molecular surveillance (September 2023–August 2024).
Manuscript change: Added timeline details in Methods, Section 2.2 Sampling.
Comment 3. Provide details on RT-PCR primer sequences, cycling conditions, and detection limit.
Response: Additional details have been included. Swab samples collected during the 2023–2024 surveillance campaigns were tested for PPR viral RNA using reverse transcription quantitative polymerase chain reaction (RT-qPCR) with a commercial kit (ID Gene™, Innovative Diagnostics, Lyon, France). RNA was extracted using the ID Gene™ Spin Universal Extraction Kit (Innovative Diagnostics, Lyon, France) in accordance with the manufacturer’s instructions.
Manuscript change: Expanded Methods, Section 2.3 Laboratory analysis with primer sequences, cycling conditions, and detection limit.
Comment 4. Add error bars to Figure 1.
Response: Error bars representing 95% confidence intervals for seroprevalence have been added to Figure 1.
Manuscript change: Updated Figure 1 and corresponding legend.
Comment 5. Address potential false negative RT-PCR due to sample timing.
Response: We agree with this important point. Although the animals tested were young and unvaccinated, transient infections or very early/late sampling could theoretically yield false negatives. We have added a paragraph discussing this limitation.
Manuscript change: Expanded Discussion to acknowledge possible false negatives and the importance of repeated surveillance.
Comment 6. Contrast non-vaccination approach in Bahrain with regional vaccinated countries.
Response: A new comparative paragraph has been added. Bahrain’s non-vaccination policy contrasts with Saudi Arabia and other GCC states, where routine vaccination complicates serological interpretation. Despite this, Bahrain has maintained moderate seroprevalence without active circulation, highlighting the effectiveness of strict biosecurity and surveillance.
Manuscript change: Added comparative discussion in Discussion.
Reviewer 2 Report
Comments and Suggestions for AuthorsComments will according to rows' number:
- 79 & 83: how it was assessed that 38 wild animals were representative of 5% at 95% confidence ? is there any estimation of wild animals population ? or how was the sample determined ?
- 79: total flocks population should be indicated; if not how it was calculated the sample ?
- 87: can you specify which kind of swabs have been used ? how they were kept and transported ? if possible, indicate producer.
- 79: if understood well, here it should be indicated that the sample is relative to 2021 - first investigation -.
- 119: same as for row 79
- in general, I would suggest to summarize in a simple Table the 2021 and 2023-2024 results; by species (sheep, goats); by herd/flock; by age (adult/young).
- 131: again: we suppose the results on Figutre 2 are relative to 2021 ; if correct, it should be indicated.
- 177: on 2021 ? on 2023/24 ?
- 182: "informally" is not the right word; eithetr smuggled or imported without control; etc. This is a serious point ! It should be discussed in depth and addressed to local Veterinary Authorities as an improvement point, as in row 192; can you give indications on how to improve controls ? Can you describe how the border between the two countries is organized ? (fences, etc ??)
- 214-216: this describes a "zero control" situation ! It should be commented in depth ! Is there any system for control and registration of imported/exported animals ? How is animal population registered in Bahrein ?
Author Response
Reviewer 2
Comment 1. Clarify representativeness of 38 wild animals (95% CI claim).
Response: The statement has been corrected. We have removed the reference to 5% at 95% CI and clarified that the wild ruminant sample reflected the available managed population, not a statistical extrapolation.
Manuscript change: Revised Methods, Section 2.2 Sampling.
Comment 2. Total flock population should be indicated; explain sample size calculation.
Response: In 2021, the total small ruminant population in Bahrain is ~85000 (60,000 sheep, 25,000 goats). Sample size was calculated at 95% CI, 5% precision, assuming 50% expected prevalence. This yielded ~1,200 samples per species.
Manuscript change: Added population data and formula reference in Methods.
Comment 3. Specify swab types, storage, and transport.
Response: Nasal and ocular swabs were collected using sterile polyester-tipped swabs (Copan Diagnostics, Italy), transported in viral transport medium at 4 °C, and processed within 24 hours.
Manuscript change: Expanded Methods, Section 2.2 Sampling.
Comment 4. Clarify “informally” used for vaccine entry.
Response: We replaced “informally” with “illegally introduced or smuggled” to better reflect the context. We also expanded the Discussion to highlight enforcement gaps and the need for stronger border control measures.
Manuscript change: Revised Discussion, paragraphs on cross-border risks.
Comment 5. Discuss border organization and animal registration systems.
Response: Additional detail provided. The King Fahd Causeway is the only land border, where animals are officially subject to quarantine, health certification, and inspection. However, risks of illegal entry exist. Animal population registration is handled through the Ministry of Municipalities Affairs and Agriculture’s Veterinary Information System, which records herd sizes and animal movements.
Manuscript change: Expanded Discussion, Section on Biosecurity and Import Controls.
Comment 6. Summarize 2021 and 2023–24 results in a single table.
Response: A new summary Table 5 has been added, presenting serological and molecular results by species, year, and method.
Manuscript change: Added Table 5 to Results section.
Round 2
Reviewer 2 Report
Comments and Suggestions for Authorsnew version and comments are fine for me.
