Trends in Tick-Borne Virus Ecology: Vector Incrimination, Focal Distribution, and Reservoir Associations
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors report about Tick-borne virus ecology and especially vector dynamics, focal distribution and reservoir associations.
There are a number of unclearities which have to be corrected before publication:
Line 41: Rickettsial diseases like relapsing fever...: Relapsing fever is not a rickettsial disease, but a borreliosis. Same with East Coast Fever, which is a Theileriosis.
Line 61: Arachnida are not split into categories, but they are divided into three families.
Line 67: Only in the genus Ixodes males are not sucking blood. In all other tick genera the adult males have to suck blood for development of sperms.
Line 97:-99: The vertebrate hosts are not infecting naive tick hosts but naive ticks.
Line 118: cases cannot be asymptomatic. Infections may be asymtomatic. Cases per se are always associated with symptoms.
In table 1 some viruses of Europe are missing like Eyach virus or Tribec virus which are at least suspected to be associated with human neurological disorders. In contrast for the New world viruses with unknown pathogenic potential are mentioned in a specific table.
In general, I am missing more detailed data on ecology. E.g. the name and work of Pavlowsky is not mentioned at all, who was the founder of the natural focus theory. In Colorado tick fever chapter it would have been interesting to mention and discuss that it mainly/exclusively occures in the mountin areas about 5000ft. The ecological aspects of these viruses are unfortunately shortcoming. so the manuscript is "only" a list of tick-borne viruses with some general information. Also I cannot find much information about vactor dynamics (!) and tick-borne diseases (how would transmission develop if the tick population increases or declines? amplification effect, dilution effect?)
Unfortunately the manuscript is not holding what promising in the title.
Author Response
Review for viruses-4480360 - “Trends in Tick-borne Virus Ecology: Vector Dynamics, Focal Distribution, and Reservoir Associations”
We thank the reviewers for their careful critiques and have revised the manuscript to address these comments. The reviewers had great insight and suggestions for the manuscript that we believe have made it stronger overall. Please find responses and descriptions of changes following individual critiques below.
Reviewer 1
Comments to the Authors: The authors report about Tick-borne virus ecology and especially vector dynamics, focal distribution and reservoir associations. There are a number of unclearities which have to be corrected before publication:
- Line 41: Rickettsial diseases like relapsing fever...: Relapsing fever is not a rickettsial disease, but a borreliosis. Same with East Coast Fever, which is a Theileriosis.
Response to Reviewer: We thank the reviewer for this correction and have fixed the text to more accurately read: “The last 125 years since this report has been marked by an abundance of discoveries related to ticks and human pathogens ranging from early reports of bacterial disease like relapsing fever (Borrelia hermsii), East Coast fever (Theileria parva), and Rocky Mountain spotted fever (Rickettsia rickettsii) in Ornithodoros, Rhipicephalus, and Dermacentor species…” (Lines 41-42)
- Line 61: Arachnida are not split into categories, but they are divided into three families.
Response to Reviewer: We thank the reviewer for this correction and have incorporated the change into the text as follows: “Within Arachnida, ticks (Order: Ixodida) are split into two main families the hard (Ixodidae) and soft (Argasidae) ticks…” (Line 64). The other families (Nuttalliellidae the third family, and the recently identified Khimairidae) are mentioned in the following lines.
- Line 67: Only in the genus Ixodes males are not sucking blood. In all other tick genera the adult males have to suck blood for development of sperms.
Response to Reviewer: We thank the reviewer for this correction, to avoid confusion we have removed lines 70-71 for clarity.
- Line 97:-99: The vertebrate hosts are not infecting naive tick hosts but naive ticks.
Response to Reviewer: We thank the reviewer for this suggestion and have incorporated it into the text (Line 103).
- Line 118: cases cannot be asymptomatic. Infections may be asymtomatic. Cases per se are always associated with symptoms.
Response to Reviewer: We thank the reviewer for this correction and have amended the text for clarity so it now reads: “As is common with arboviruses, this is presumably an underestimate as most human infections are likely asymptomatic, self-resolving, or undiagnosed.” (Line 129)
- In table 1 some viruses of Europe are missing like Eyach virus or Tribec virus which are at least suspected to be associated with human neurological disorders. In contrast for the New world viruses with unknown pathogenic potential are mentioned in a specific table.
Response to Reviewer: We thank the reviewer for pointing this out and opted to keep Table 1 to the previously listed viruses for conciseness but agree discussion of these other viruses in the Old World with probable/low case burdens is also important. We’ve added additional information in the introductory paragraph to Chapter 2. Tick-borne Viruses of the Old World to include information on these lesser viruses. The text now reads: “Additionally, there are numerous identified tick-borne viruses with unknown yet probable pathogenic potential in humans like Eyach, Tribec, Karshi, Batken, and Kadam viruses, but lack any or have minimal reports of confirmed clinical human cases likely due to under recognition and diagnostic biases” (Line 129-133).
- In general, I am missing more detailed data on ecology. E.g. the name and work of Pavlowsky is not mentioned at all, who was the founder of the natural focus theory. In Colorado tick fever chapter it would have been interesting to mention and discuss that it mainly/exclusively occures in the mountin areas about 5000ft. The ecological aspects of these viruses are unfortunately shortcoming. so the manuscript is "only" a list of tick-borne viruses with some general information. Also I cannot find much information about vactor dynamics (!) and tick-borne diseases (how would transmission develop if the tick population increases or declines? amplification effect, dilution effect?)
Response to Reviewer: We thank the reviewer for making this point and agree with the importance of Pavlowsky’s work especially in this context of natural foci. This was not discussed in detail in this review to focus the texts on 1) the viral discovery, 2) broad vector incrimination, 3) vertebrate hosts, and 4) geographic distributions in relation to human disease. The concept and proof of Pavlowsky’s theory in the context of TBEV and POWV is currently being prepared by our group which will provide an indepth discussion of this theory and a review of it’s application with these related, yet geographically disparate flaviviruses. We felt these details were beyond the scope of this review as our discussion focuses more on the broad host associations with these viruses in juxtaposition to these geographic transmission hotspots that are also linked to clinical disease variability. Additionally, we agree vector dynamics and broad ecological interactions of these viruses are not thoroughly discussed here and have revised the title to reflect this (Line 2).
- Unfortunately the manuscript is not holding what promising in the title.
Response to Reviewer: We understand the reviewer’s concern and have decided to revise the title as follows: “Trends in Tick-borne Virus Ecology: Vector Incrimination, Focal Distribution, and Reservoir Associations” (Line 2).
Reviewer 2 Report
Comments and Suggestions for AuthorsThe manuscript: "Trends in Tick-Borne Virus Ecology: Vector Dynamics, Focal Distribution, and Reservoir Associations" is a useful review for monitoring tick-borne viruses. It is quite well written, covers new information in this research area. It requires only a few additions and improvements.
- The first chapter would be easier to comprehend if it were divided using subtitles like other chapters are.
- Either the Chapter 5. is missing, or the chapter: Conclusions and Future Priorities has been mislabeled.
- It would be interesting to include the rest of the New World countries in the Figure 2., or at least give an explanation somewhere in the text (such as lack of publications on the subject from other New World countries)
- The part A of the Figure 1. is quite interesting, and I would like the authors to comment on why there are, on occasion, quite significant differences between neighbouring countries, for example Spain and Portugal have the highest number of species reported, while France has only 1. Is the lack of papers on the subject the issue here, or there are some other differences between countries that attribute to that. Other than that I find the paper suitable for publishing.
Author Response
Review for viruses-4480360 - “Trends in Tick-borne Virus Ecology: Vector Dynamics, Focal Distribution, and Reservoir Associations”
We thank the reviewers for their careful critiques and have revised the manuscript to address these comments. The reviewers had great insight and suggestions for the manuscript that we believe have made it stronger overall. Please find responses and descriptions of changes following individual critiques below.
Reviewer 2
Comments to the Authors: The manuscript: "Trends in Tick-Borne Virus Ecology: Vector Dynamics, Focal Distribution, and Reservoir Associations" is a useful review for monitoring tick-borne viruses. It is quite well written, covers new information in this research area. It requires only a few additions and improvements.
- The first chapter would be easier to comprehend if it were divided using subtitles like other chapters are.
Response to Reviewer: We thank the review for this suggestion and have divided the first chapter into the following subchapters: Tick Natural Histories and Virus Transmission in Ticks. (Lines 58 and 93)
- Either the Chapter 5. is missing, or the chapter: Conclusions and Future Priorities has been mislabeled.
Response to Reviewer: We thank the reviewer for finding this mistake and have corrected the title to now read: “Chapter 5. Conclusions and Future Priorities” (Line 362).
- It would be interesting to include the rest of the New World countries in the Figure 2., or at least give an explanation somewhere in the text (such as lack of publications on the subject from other New World countries)
Response to Reviewer: We thank the reviewer for making this suggestion and have now included an explanation in the introductory paragraph of Chapter 3. Tick-borne Viruses of the New World. The text now includes, “Despite the abundant circulation of mosquito-borne viruses in Central and South America, little remains known about the burden of tick-borne viruses in these regions despite known prevalence of Amblyomma, Rhipicephalus, and Dermacentor species. The current knowledge of pathogenic tick-borne viruses in the Americas is dependent on knowledge of the four circulating viruses recognized in North America likely due to their known association with fatal or severe clinical cases, support for robust awareness and testing of bacterial tick-borne pathogens, and lack of prioritization of ticks in the mosquito-dominated tropics” (Line 250-257).
- The part A of the Figure 1. is quite interesting, and I would like the authors to comment on why there are, on occasion, quite significant differences between neighbouring countries, for example Spain and Portugal have the highest number of species reported, while France has only 1. Is the lack of papers on the subject the issue here, or there are some other differences between countries that attribute to that. Other than that I find the paper suitable for publishing.
Response to Reviewer: We thank the reviewer for making this suggestion as we agree it is an important common trend with tick-borne virus research – the lack of testing and awareness contributing to our understanding of “distribution” which is rarely the actual geographic distribution of the virus. We have amended the introductory paragraph of Chapter 2. Tick-borne Viruses of the Old World to further discuss this. The text now includes, “The distribution and number of co-circulating viruses is based on reported cases and presence of infected ticks or vertebrates which likely underestimates the true distribution of these viruses and reported country-specific tick-borne virus burdens. Many factors influence this underestimate including lack of reporting, testing, and awareness in some countries” (Line 120-124).
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsNo further comments
Author Response
Reviewer Comment: The manuscript is now acceptable for publication subject to one minor
revision. Your text on lines 41-42 states that East Coast fever is a
bacterial disease. Please correct this error as the causative agent,
Theileria parva, is a protozoan parasite and not a bacterium.
RESPONE TO REVIEWER: We appreciate the reviewer correcting this important point and have adjusted the text to now read, "The last 125 years since this report has been marked by an abundance of discoveries related to ticks and human pathogens ranging from early reports of bacterial and protozoan diseases like relapsing fever (Borrelia hermsii), East Coast fever (Theileria parva), and Rocky Mountain spotted fever (Rickettsia rickettsii) in Ornithodoros, Rhipicephalus, and Dermacentor species…” (Lines 41-42).
