Detection of Bovine Respiratory Syncytial Virus in Cattle: A Systematic Review and Meta-Analysis

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Ruminants (ISSN 2673-933X)

ruminants-3228048

 

Detection of bovine respiratory syncytial virus in cattle: a systematic review and meta-analysis

 

General comments

 

The authors state that the goal of this manuscript was to “conduct a systematic review and meta-analysis to determine the prevalence of BRSV and identify associated risk factors.”  Because this was a review of published papers, not a survey of BRSV detection in the field, they did not determine the prevalence of BRSV.  They determined the prevalence of BRSV detection reported in papers submitted for publication.  None of the papers available to them constituted a large scale comprehensive survey that effectively determined the incidence of BRSV exposure or detection in any large geographic location.  Of course, the authors can only work with the data that is available.  I am not faulting them for that.  They need to be more circumspect in their claims, however.  They did not determine the prevalence of BRSV.  They surveyed the reports of BRSV in the literature.  This may seem a picayune point.  However, what too frequently happens is that subsequent authors, practicing poor scholarship, will quote the results of a literature review verbatum and use their generalized overviews as established fact.  This is particularly problematic when relatively small geographically localized studies are used to represent a large geographic area (see figure 2B).  This figure should include that number of studies used to determine “prevalence” for each country.  This way the reader would have a better idea of the limitations of the data. 

 

This review is more useful when comparing the rate isolation/detection of BRSV to other respiratory pathogens in multiple BRD cases.  I would encourage the authors to put more emphasis on this aspect of their review compared to determining “prevalence”.  Examining the reported association with of BRSV with other pathogens across BRDC cases is also useful.

 

Would be good to see more discussion on impact of BRSV infections as a precursor to BRDC.  The BRSV literature suggests that BRSV is more likely to be detected in the early stages of a BRDC outbreaks than from animals with clinical presentations of respiratory disease.  This scenario would impact the frequency of association of BRSV with BRDC.  Did you come across any of this literature in your review?  Would the criteria used for your review find these papers?  The review doesn’t necessarily need to be repeated but this weakness needs to be noted.

 

Specific comments

 

Section 3.2.2

 

I’m having trouble understanding how 24 BRSV positive cases represents a random selection. 

 

Fig. 4

 

Be careful about using the term seropositivity for serum samples in which BRSV was detected.  Traditionally seropositivity is used to refer to serum samples positive for antibody.  It might be best to reconsider this term to avoid confusion.

 

Discussion of risk factors (lines 398 – 402)

 

A number of the factors listed were discussed in just one article, sometimes with accompanied data and sometimes just as discussion points.  The authors need to clearly state that the factors listed are suggested, not always proved and not necessarily generally accepted.  They should be presented as possibilities not facts.     

Author Response

Reviewer 1:

General comments

 The authors state that the goal of this manuscript was to “conduct a systematic review and meta-analysis to determine the prevalence of BRSV and identify associated risk factors.”  Because this was a review of published papers, not a survey of BRSV detection in the field, they did not determine the prevalence of BRSV.  They determined the prevalence of BRSV detection reported in papers submitted for publication.  None of the papers available to them constituted a large scale comprehensive survey that effectively determined the incidence of BRSV exposure or detection in any large geographic location.  Of course, the authors can only work with the data that is available.  I am not faulting them for that.  They need to be more circumspect in their claims, however.  They did not determine the prevalence of BRSV.  They surveyed the reports of BRSV in the literature.  This may seem a picayune point.  However, what too frequently happens is that subsequent authors, practicing poor scholarship, will quote the results of a literature review verbatum and use their generalised overviews as established fact.  This is particularly problematic when relatively small geographically localised studies are used to represent a large geographic area (see figure 2B).  This figure should include that number of studies used to determine “prevalence” for each country.  This way the reader would have a better idea of the limitations of the data. 

 Authors: Thank you for your comments and valuable suggestions. We understand the concern regarding using the term "prevalence" in this context and acknowledge the need for clearer phrasing. As correctly pointed out, our study does not aim to directly measure the prevalence of BRSV in a broad population. Instead, we performed a systematic review and meta-analysis to evaluate the prevalence of BRSV detection as reported in published studies. To avoid misinterpretation, revisions have been made on lines ( 23 and 101 and for the purpose of this manuscript, the terms prevalence and detection rate have been defined in the methods section of the manuscript ( lines 167-173).  Additionally, in addition to Figure 2B, data for each country can be found in Supplementary Figure 1.

Reviewer 1:

This review is more useful when comparing the rate isolation/detection of BRSV to other respiratory pathogens in multiple BRD cases.  I would encourage the authors to put more emphasis on this aspect of their review compared to determining “prevalence”.  Examining the reported association with of BRSV with other pathogens across BRDC cases is also useful.

 Authors: Thank you for your feedback. We recognise the value of examining the rate of isolation and detection of BRSV in comparison to other respiratory pathogens in BRDC cases, and we agree that this aspect provides important information into the role of BRSV within the broader disease complex. While our systematic review primarily focused on evaluating the detection rates and associated risk factors specific to BRSV, we did address some pathogen comparisons in the qualitative analysis (subsection 3.5, beginning on line 381), where we included co-infections that demonstrated statistically significant associations with BRSV. However, a more detailed comparative analysis of BRSV alongside other respiratory pathogens, including those without statistically significant associations, though highly relevant, falls outside the scope of the current study. We agree that this would be a valuable direction for future research, and we would be eager to explore this in a subsequent study.

 Reviewer 1:

Would be good to see more discussion on impact of BRSV infections as a precursor to BRDC.  The BRSV literature suggests that BRSV is more likely to be detected in the early stages of a BRDC outbreaks than from animals with clinical presentations of respiratory disease.  This scenario would impact the frequency of association of BRSV with BRDC.  Did you come across any of this literature in your review?  Would the criteria used for your review find these papers?  The review doesn’t necessarily need to be repeated but this weakness needs to be noted.

 Thank you for your valuable feedback. We acknowledge that BRSV is frequently detected during the early stages of BRDC, which may influence its association with advanced respiratory disease. Our review included studies on BRSV detection in BRDC cases, but many did not specify the detection timing relative to disease progression. The current study addresses this issue in the introduction ( lines 56-60 ) and discussion ( lines 470-476).

Reviewer 1:

Specific comments

 

Section 3.2.2

 I’m having trouble understanding how 24 BRSV positive cases represents a random selection. 

  Authors: Thank you for your feedback. The reference to the "24 BRSV positive cases representing a random selection" refers to the random sampling approach used in the studies rather than randomness in the distribution of positive cases. The studies employed random sampling methods to minimise selection bias during sample collection. The identification of 24 BRSV-positive cases resulted from testing these randomly selected samples, and this reflects the prevalence of BRSV in that cohort. The relatively low number of positive cases highlights the low prevalence of BRSV in the studied population and does not suggest a flaw in the random sampling methodology itself.

Reviewer 1:

Fig. 4

Be careful about using the term seropositivity for serum samples in which BRSV was detected.  Traditionally seropositivity is used to refer to serum samples positive for antibody.  It might be best to reconsider this term to avoid confusion.

 Authors: Thank you for noticing the error. We have now revised the Figure 4  legend.  

 

Reviewer 1:

Discussion of risk factors (lines 398 – 402)

 A number of the factors listed were discussed in just one article, sometimes with accompanied data and sometimes just as discussion points.  The authors need to clearly state that the factors listed are suggested, not always proved and not necessarily generally accepted.  They should be presented as possibilities not facts.     

Authors: Thank you for this important observation. We acknowledge that some of the risk factors mentioned were drawn from single studies or presented as discussion points without conclusive data. In response, we have revised the discussion section ( lines 537-540).

 

Reviewer 2 Report

Comments and Suggestions for Authors

Overall a very well written and interesting article. One comment I would recommend considering adding in your discussion, is the vaccine efficacy (or lack thereof) for BRSV.

On Figure 2, the prevalence size is hard to visualize. Prevalence keys should be the same for both figures A and B. Maybe make different symbols? I will defer to the authors and editors for final recommendation.  

Author Response

Reviewer 2:

Comments and Suggestions for Authors

Overall a very well written and interesting article. One comment I would recommend considering adding in your discussion, is the vaccine efficacy (or lack thereof) for BRSV.

 

Authors: Thank you for your suggestion. We have addressed the vaccine efficacy for BRSV in the revised discussion (line 440).

Reviewer 2:

On Figure 2, the prevalence size is hard to visualize. Prevalence keys should be the same for both figures A and B. Maybe make different symbols? I will defer to the authors and editors for final recommendation.  

Authors: Thank you for your suggestion. Figure 2 is primarily designed to visually indicate the spatial distribution of BRSV detected using different methods across various populations. The symbols for both panels (A and B) are consistent, ensuring comparability. We acknowledge that the current representation might make it difficult to visualize the prevalence size clearly. Additionally, supplementary figure 1 provides further country-specific information for more detailed visualization.