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Babesiosis and Tick-Borne Pathogens Subcommittee Report to the Tick-Borne Disease Working Group








  
  
    

  
      





Disclaimer

*Information and opinions in this report do not necessarily reflect the opinions of the Working Group, the U.S. Department of Health and Human Services, or any other component of the Federal Government. Readers should not consider the report or any part of it to be guidance or instruction regarding the diagnosis, care, or treatment of tick-borne diseases or to supersede in any way existing guidance. All subcommittee members actively participated in the development of this report. Members voted to approve submission of the report to the Working Group and on the wording of each of the possible actions contained in the report. The vote to submit the report indicates general agreement with the content of the document, but it does not necessarily indicate complete agreement with each and every statement in the full report.*

Background

Tick-borne diseases (TBD) account for approximately 75 percent of all nationally notifiable vector-borne diseases reported to Centers for Disease Control and Prevention (CDC) each year. In 2017, 59,349 cases of TBDs were reported to CDC, a 22% increase over reported cases in 2016. This represented the highest number of TBD cases ever reported in a single year in the United States (U.S.) and included - 42,743 Lyme disease cases, 7,718 anaplasmosis and ehrlichiosis cases, 6,248 spotted fever rickettsiosis cases, 2,368 babesiosis cases, 239 tularemia cases, and 33 Powassan virus cases.

The Babesiosis and Other Tick-Borne Pathogens Subcommittee was established to address tick-borne pathogens of concern that are not individually addressed by the other, pathogen-specific, subcommittees. Some of the most important agents discussed in the deliberations of the subcommittee are included in Table 1. These agents, and other closely related pathogens of public health importance, are discussed in greater detail in the Results and Appendices of this report.

**Table 1. Some Key Pathogens Addressed by the Babesiosis and Other Tick-Borne Pathogens Subcommittee.**

Pathogen
			Disease
			Priority Action & Appendix*Babesia microti*, *Babesia duncani*
			Babesiosis
			Priority Action 1; Appendix A*Borrelia hermsii*, *B. turicatae*and related species
			Tick-borne relapsing fever
			Priority Action 2; Appendix B*Borrelia miyamotoi*
			Borrelia miyamotoi disease
			Priority Action 2; Appendix BPowassan virus
			Powassan virus disease
			Priority Action 3; Appendix CColorado tick fever virus
			Colorado tick fever
			Priority Action 3; Appendix CBourbon virus
			Bourbon virus disease
			Priority Action 3; Appendix CHeartland virus
			Heartland virus disease
			Priority Action 3; Appendix C*Francisella tularensis*
			Tularemia
			Priority Action 4; Appendix DAmong tick-borne pathogens, the disease agents addressed by this subcommittee present unique challenges: they are relatively uncommonly reported or emerging, may have regional differences in distribution, and, in some cases, can result in severe illness, including death. Consequently, they may not be readily recognized clinically, particularly in cases of travel-associated infections. Delays in diagnosis and treatment may lead to more severe outcomes. Babesiosis often occurs in patients with other underlying conditions where the illness can be both severe and difficult to treat. While some of these diseases have a relatively stable incidence, others are emerging in both incidence and distribution with more reported cases generally occurring each year in the U.S.

The subcommittee identified 27 potential actions that represent important challenges and needs for each of these pathogens and associated illnesses. These challenges and needs provide unique opportunities and priorities for critical research and other activities and are briefly summarized in Table 2 then discussed in greater detail in the Results section of this report.

**Table 2. Preliminary list of challenges or needs identified by the subcommittee**

Challenges or needsBetter understanding of the disease ecology and natural historyImproved surveillance, particularly for *Babesia,* to capture species and travel history of patientsMultiple pathogen interaction within vectors and hosts and subsequent impact on transmissionImproved diagnostic assays that distinguish tick-borne relapsing fever from *Borrelia miyamotoi* infection, and a broader availability of diagnostic assays for this entire group of pathogens.Improved understanding of range of illness associated with infection, from asymptomatic to severe manifestationsCo-infections in patients and the impact on clinical symptoms, disease severity, and treatment response, particularly in the case *B. miyamotoi,* *B. burgdorferi,* and*Babesia*speciesBetter understanding of the efficacies of currently recommended treatments and the need for new treatment options for *Babesia* infections**Note:**This table contains a preliminary list of initially identified challenges or needs that is further expanded upon in the Results section of the report.

Methods

Membership

In establishing the subcommittee, the co-chairs made a deliberate effort to ensure diversity among the group by including - university researchers, government scientists, public health professionals, physicians, and patient advocates. In addition to including members from different stakeholder groups, subcommittee members were also selected to represent different regional perspectives due to the regionality of these illnesses. The subcommittee members and a brief description of their qualifications to serve are included in Table 3. Except for one of the co-chairs, all of the subcommittee members were non-federal participants. The subcommittee was supported by a science writer, Melinda T. Hough, PhD; and a federal officer, Debbie Seem, RN, MPH; throughout their deliberations.

**Table 3: Members of the Babesiosis and Other Tick-Borne Pathogens Subcommittee.**

**Members**
			**Type**
			**Stakeholder Group**
			**Expertise***Co-Chair*

			**Charles Benjamin (Ben) Beard, PhD,** Deputy Director, Division of Vector-Borne Diseases, Centers for Disease Control and Prevention (CDC); Ft. Collins, CO
			Federal
			Scientist
			40+ years of experience working in vector-borne disease prevention and control, including 28 years at CDC working on infectious diseases with an emphasis on vector-borne diseases both domestic and global.*Co-Chair*

			**Eugene (Gene) David Shapiro, MD,**Professor of Pediatrics, Epidemiology, and Investigative Medicine, Yale University; Vice Chair for Research, Department of Pediatrics; Co-Director of Education, Yale Center for Clinical Investigation; Deputy Director, Yale PhD Program in Investigative Medicine; New Haven, CT
			Federal
			Scientist and Health Care Provider
			Dr. Shapiro has been seeing patients with tick-borne diseases and has been conducting research on tick-borne diseases for 40 years.**Alan G. Barbour, MD,**Distinguished Professor; Microbiology & Molecular Genetics, Medicine, and Ecology & Evolutionary Biology; University of California Irvine; Irvine, CA
			Public
			Scientist
			Co-discoverer of the cause of Lyme disease and 40 years’ experience with the microbiology, immunology, genetics, and ecology of Lyme disease, relapsing fever, and other tick-borne diseases.**P.** **Bryon Backenson, MS,**Deputy Director for Disease Control, New York State Department of Health; Assistant Professor, University at Albany, State University of New York, School of Public Health; Albany, NY
			Public
			Scientist
			25+ years of working with tick-borne diseases from multiple angles, including field ecology, disease pathology, and human and vector surveillance. Past author of the national Lyme disease surveillance case definition.**Greg Ebel, ScD,**Professor, Department of Microbiology, Immunology, and Pathology, Colorado State University; Director, Arthropod-Borne and Infectious Diseases Laboratory, Colorado State University; Ft. Collins, CO
			Public
			Scientist
			20+ years working on arthropod-borne viruses, including Powassan virus, and emerging tick-borne flavivirus. Work on Powassan has encompassed field studies on host associations and ecology, sequencing studies of virus population biology and evolution, and experimental transmission studies.**Richard I. Horowitz, MD,**Internist, Hudson Valley Healing Arts Center; Hyde Park, NY
			Public
			Health Care Provider
			30+ years of experience treating Lyme disease, babesiosis, and tick-borne co-infections; former member HHS TBDWG 2017-2019, former co-chair HHS Other Tick-borne Diseases and Co-infections subcommittee.**Anne Kjemtrup, DVM, MPVM, PhD**, Research Scientist, California Department of Public Health, Vector-Borne Disease Section; Sacramento, CA
			Public
			Epidemiologist
			25+ years of experience working on tick-borne diseases in California including description of epidemiology of *Babesia duncani*, and as public health subject matter expert on tick-borne diseases in California including borrelioses and rickettsial diseases.**Anna Schotthoefer, PhD,** Project Scientist, Marshfield Clinic Research Institute; Marshfield, WI
			Public
			Scientist
			12+ years of experience working on the ecology and epidemiology of vector-borne diseases, including 9+ years working to improve the clinical and laboratory diagnosis of tick-borne diseases in the United States**Sam R. Telford, III, SD, MS,** Professor, Department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine at Tufts University; N. Grafton, MA
			Public
			Scientist
			35+ years as a researcher focused on the epidemiology and control of deer tick transmitted infections in New England, including contributions to Lyme disease vaccines, ecology of Lyme disease, and public health burden of *Babesia microti*, *Anaplasma phagocytophilum*, *Borrelia miyamotoi*, Powassan virus, and *Francisella tularensis***Monica White**, President and Co-founder, Colorado Tick-Borne Disease Awareness Association; Poncha Springs, CO
			Public
			Patient Advocate (nonprofit)
			18+ years Wildlife Biologist US Forest Service (former career employee); 13+ years patient & caregiver of children (family) with Lyme disease & other TBDs; Lyme disease & TBD educator & advocate; member Public Tick IPM Working Group; co-coordinator of Tick Research to Eliminate Disease (TRED) Scientist Coalition; member 2018 HHS-TBDWG Subcommittee for Disease Vector, Surveillance & Prevention.Meetings

Ten meetings were held bi-weekly by conference call, from July 18, 2019 through January 10, 2020. Meetings were suspended for holidays and on one occasion when there was a conflict with the Working Group meeting. An overview of these meetings is presented in Table 4.

**Table 4: Overview of Babesiosis and Other Tick-Borne Pathogen Subcommittee Meetings, 2019.**

**Meeting No.**
			**Date**
			**Present**
			**Topics Addressed**1
			July 18, 2019
			Alan Barbour, Ben Beard (Co-Chair), P. Bryon Backenson, Greg Ebel, Richard Horowitz, Anne Kjemtrup, Gene Shapiro (Co-Chair), Sam Telford, Monica White

			Nicole Green (TBDWG support), Jennifer Gillissen (contract support), Christina Li (contract support)
			Introduction of members to each other; review of subcommittee report outline, milestones, and deliverables; and discussion of proposed topics to be addressed, including potential speakers.2
			August 1, 2019
			Alan Barbour, Ben Beard (Co-Chair), Greg Ebel, Richard Horowitz, Anne Kjemtrup, Anna Schotthoefer, Gene Shapiro (Co-Chair), Sam Telford

			Nicole Green (TBDWG support), Jennifer Gillissen (contract support), Christina Li (contract support)
			Two presenters provided PowerPoint presentations and answered questions from subcommittee members; discussion on the key issues and questions relating to *Babesia*; and finalization of presentations for the remaining meetings. The presenters and their topics included in order of presentation: Susan P. Montgomery, DVM, MPH: Babesiosis; and Choukri Ben Mamoun, PhD: Pathogenesis and Therapy of *Babesia microti & Babesia duncani*.3
			August 15, 2019
			Ben Beard (Co-Chair), P. Bryon Backenson, Greg Ebel, Richard Horowitz, Anne Kjemtrup, Anna Schotthoefer, Gene Shapiro (Co-Chair), Sam Telford

			Nicole Green (TBDWG support), Jennifer Gillissen (contract support), Melinda T. Hough (contract support)
			Discussion of report content and provisions for managing discordant views among subcommittee members; and finalization and prioritization of Babesia-related issues/needs.4
			August 29, 2019
			Alan Barbour, Ben Beard (Co-Chair), P. Bryon Backenson, Greg Ebel, Richard Horowitz, Anne Kjemtrup, Anna Schotthoefer, Gene Shapiro (Co-Chair), Sam Telford, Monica White

			Debbie Seem (TBDWG support), Melinda T. Hough (contract support)
			Three presenters provided PowerPoint presentations and answered questions from subcommittee members. The presenters and their topics included in order of presentation: Alan G. Barbour, MD: Tick-borne Relapsing Fever including *Borrelia miyamotoi* infection; Greg Ebel, ScD: Emergence of Powassan Virus in North America; and P. Bryon Backenson, MS: How NYSDOH handled a small Powassan cluster in 2017.5
			September 26, 2019
			Alan Barbour, Ben Beard (Co-Chair), P. Bryon Backenson, Greg Ebel, Richard Horowitz, Anne Kjemtrup, Anna Schotthoefer, Sam Telford, Monica White

			Nicole Green (TBDWG support), Melinda T. Hough (contract support)
			Jeannine Petersen, PhD presented on the topic of tularemia and answered questions from subcommittee members.6
			October 10, 2019
			Alan Barbour, Ben Beard (Co-Chair), P. Bryon Backenson, Greg Ebel, Richard Horowitz, Anna Schotthoefer, Gene Shapiro (Co-Chair), Sam Telford, Monica White

			Debbie Seem (TBDWG support), Melinda T. Hough (contract support)
			Subcommittee members discussed, revised and voted on the Background and Methods document. The subcommittee also discussed the Results and Potential Actions draft process before identifying writing teams and beginning to draft these sections.7
			October 24, 2109
			Beard (Co-Chair), P. Bryon Backenson, Greg Ebel, Richard Horowitz, Anne Kjemtrup, Anna Schotthoefer, Gene Shapiro (Co-Chair), Monica White

			Debbie Seem (TBDWG support), Jennifer Gillissen (contract support), Melinda T. Hough (contract support)
			Subcommittee members reviewed the progress of each subsection; discussed the process of insuring full subcommittee input into each section; and discussed their workplan and deliverables to the Tick-Borne Diseases Working Group.8
			November 7, 2019
			Alan Barbour, Ben Beard (Co-Chair), P. Bryon Backenson, Greg Ebel, Richard Horowitz, Anne Kjemtrup, Anna Schotthoefer, Gene Shapiro (Co-Chair), Sam Telford, Monica White

			James Berger (TBDWG DFO), Jennifer Gillissen (contract support), Melinda T. Hough (contract support)
			Subcommittee members reviewed the progress of each subsection and discussed the process of insuring full subcommittee input into each section.9
			November 21, 2019
			Alan Barbour, Ben Beard (Co-Chair), P. Bryon Backenson, Richard Horowitz, Anne Kjemtrup, Anna Schotthoefer, Gene Shapiro (Co-Chair), Monica White

			Debbie Seem (TBDWG support), Jennifer Gillissen (contract support), Melinda T. Hough (contract support)
			Subcommittee members reviewed the progress of the Results and Potential Action draft sections and agreed a timeline for full subcommittee comment and voting.10
			December 19, 2019
			Alan Barbour, Ben Beard (Co-Chair), P. Bryon Backenson, Greg Ebel, Richard Horowitz, Anne Kjemtrup, Anna Schotthoefer, Gene Shapiro (Co-Chair), Sam Telford, Monica White

			Debbie Seem (TBDWG support), Melinda T. Hough (contract support)
			Subcommittee members reviewed outstanding Potential Actions language and agreed a timeline for full subcommittee comment, voting, and submission.Over the course of the meetings, presentations were given both by outside subject matter experts, who were suggested by subcommittee members, and by subcommittee members themselves who are known experts in the field. These presentations provided important background information to guide discussions aimed at identifying key challenges and needs. The list of presentation topics and presenters is shown in Table 5.

**Table 5: Presenters to the Babesiosis and Other Tick-Borne Pathogens Subcommittee.**

**Meeting No.**
			**Presenter**
			**Topics Discussed**
			**Ok to Share?**2
			Susan P. Montgomery, DVM, MPH and Choukri Ben Mamoun, PhD.
			Babesiosis; and Pathogenesis and Therapy of *Babesia microti* & *Babesia duncani*.
			Yes4
			Alan G. Barbour, MD; Greg Ebel, ScD; and P. Bryon Backenson, MS.
			Tick-borne Relapsing Fever including *Borrelia miyamotoi*infection; Emergence of Powassan Virus in North America; and How NYSDOH handled a small Powassan cluster in 2017.
			Yes5
			Jeannine Petersen, PhD.
			Tularemia
			YesReport Development

Subcommittee meetings that were held from June through September focused on discussing the following: (1) subcommittee goals and processes, (2) scope and content matter for the report, and (3) key challenges and needs. Meetings from October through January focused on drafting, discussing, and approving various sections of the report.

The subcommittee recognized the important contributions of the 2018 Health and Human Services (HHS) Tick-Borne Disease Working Group Report to Congress, the 2018 subcommittee report on “Other Tick-Borne Diseases and Coinfections”, and specific contributions of members who had served previously on that subcommittee. It was agreed that efforts would be made both to reference and build upon that report given an overlap in scope. It was also agreed that an in-depth awareness of published literature was a key foundation to the subcommittee’s work, with the aim of identifying specific knowledge gaps and high priority needs for tools and resources. The subcommittee relied on the rich diversity of views among members, with different specialties and different life experiences, to ensure that alternative views were represented in the report, based both on published literature as well as professional and personal experience. When differences were noted, an emphasis was placed on recognizing and respecting differing views, and acknowledging that if needed, both majority and minority views could be included, supported by subcommittee vote. The subcommittee noted that both the federal inventory from the previous Working Group report and public comments were important resources available for use in developing the final report.

The Background and Methods sections were drafted primarily by the subcommittee co-chairs using the template that was provided, shared with the larger subcommittee, discussed, revised, and approved by vote of the subcommittee. The subcommittee voted unanimously in approval of the Background section (9 in favor; 0 opposed; 1 absent). A second unanimous vote in support of both the Background and Methods sections combined was recorded (9 in favor; 0 opposed; 1 absent). One person was absent from the meeting when the voting occurred.

For the Results section, key content areas noted below were identified and subcommittee members volunteered to work together in drafting the respective subsections of the report generally following the template that was provided.

Babesia (Lead writers: Sam Telford and Rich Horowitz)
	Tickborne relapsing fever and *Borrelia miyamotoi* disease (Lead writers: Alan Barbour and Monica White)
	Tick-borne viruses (Lead writers: Greg Ebel and Bryon Backenson)Tularemia (Lead writers: Gene Shapiro and Sam Telford)

Throughout the course of the subcommittee’s discussions and subsequent drafting, review, and approval of the report, efforts were made to encourage a diversity of views and opinions. When disagreements occurred, efforts were made to discuss the differences, arriving at compromises when possible. For any points of impasse, the opportunity was provided for written minority views that were supported by subcommittee vote. This option was not needed, however, since consensus was achieved. Each section of the report was voted on for approval by the subcommittee with the votes for each section noted in Table 6. There was full subcommittee consensus on the vast majority of the report content.

**Table 6: Votes Taken by the Babesiosis and Other Tick-Borne Pathogens Subcommittee.**

**Meeting or Date**
			**Motion**
			**Result**
			**Minority Response**6
			To approve the draft Background section of the report for submission to the Working Group
			Outcome: Passed—all present in favor; none opposed; none abstained; one member was not present (9/0/0/1)
			No6
			To approve the draft Background and Methods section of the report for submission to the Working Group
			Outcome: Passed—all present in favor; none opposed; none abstained; one member was not present (9/0/0/1)
			No11/27/2019
			Results > Priority Action 1: **Babesiosis** > **Vote on Potential Action One**: Explore the utility of newly developed blood screening technologies for validation for clinical diagnostic use.
			Outcome: Passed—all present in favor; none opposed; none abstained; none absent (10/0/0/0)
			No11/27/2019
			Results > Priority Action 1: **Babesiosis** > **Vote on Potential Action Two:**Provide education to health care providers, including subspecialists and frontline providers (including but not limited to hospitalists, OB/GYN, and infectious disease doctors), in addition to family practice and internal medicine physicians, regarding the signs/symptoms/risks/laboratory evaluation/treatment challenges of babesiosis.
			Outcome: Passed—all present in favor; none opposed; none abstained; none absent (10/0/0/0)
			No11/27/2019
			Results > Priority Action 1: **Babesiosis** > **Vote on Potential Action Three:**Conduct laboratory research and clinical trials to evaluate new treatment regimens for babesiosis. New treatment regimen investigation should include research on immunotherapies (e.g., human monoclonal antibodies) or adjunctive therapies to control parasitemia while on drug treatment. New treatment regimens can be evaluated in animal models prior to clinical evaluation and human trials. Host factors are important therefore more research is needed to determine the best therapeutic regimen in conditions where chronic parasitemia may occur, in particular whether adjunctive therapy could be useful.
			Outcome: Passed—all present in favor; none opposed; none abstained; none absent (10/0/0/0)
			No11/27/2019
			Results > Priority Action 1: **Babesiosis**> **Vote on Potential Action Four:**Conduct research on the ecology and distribution of *B. duncani* and other *Babesia* species (e.g., MO-1) that might be pathogenic. To facilitate such research, development and validation of sensitive and specific serologic methods to detect exposure to *B. duncani* are needed.
			Outcome: Passed—all present in favor; none opposed; none abstained; none absent (10/0/0/0)
			No11/27/2019
			Results > Priority Action 1: **Babesiosis**> **Vote on Potential Action Five:**Educate state health departments on the Council of State and Territorial Epidemiologist (CSTE) case definitions and the importance of reporting for these nationally notifiable diseases to the species level.
			Outcome: Passed—8 in favor; none opposed; 2 abstained; none absent (8/0/2/0)
			No11/27/2019
			Results > Priority Action 2: **Tick-Borne Relapsing Fever and *Borrelia miyamotoi*Infection** > **Vote on Potential Action One:**Improve public education on prevention of tick bites. Improve education of health care providers regarding clinical manifestations, diagnosis, treatment, modes of transmission, surveillance reporting, and preventive measures for the unique exposure risks of TBRF and BMD.
			Outcome: Passed—all present in favor; none opposed; none abstained; none absent (10/0/0/0)
			No11/27/2019
			Results > Priority Action 2: **Tick-Borne Relapsing Fever and *Borrelia miyamotoi*Infection**> **Vote on Potential Action Two:**Develop point-of-care testing, such as with a nucleic acid amplification test, to support the diagnosis of TBRF and BMD in their symptomatic stages.
			Outcome: Passed—9 in favor; none opposed; 1 abstained; none absent (9/0/1/0)
			No11/27/2019
			Results > Priority Action 2: **Tick-Borne Relapsing Fever and *Borrelia miyamotoi*Infection** > **Vote on Potential Action Three:**Develop immunodiagnostic assays to discriminate between TBRF*Borrelia* species and *B. miyamotoi.*
			Outcome: Passed—all present in favor; none opposed; none abstained; none absent (10/0/0/0)
			No11/27/2019
			Results > Priority Action 2: **Tick-Borne Relapsing Fever and *Borrelia miyamotoi*Infection** > **Vote on Potential Action Four:**Assess the effectiveness of alternatives to oral doxycycline and parenteral penicillin as treatments of TBRF and BMD, beginning first with *in vitro* testing and then animal models.
			Outcome: Passed—all present in favor; none opposed; none abstained; none absent (10/0/0/0)
			No11/27/2019
			Results > Priority Action 2: **Tick-Borne Relapsing Fever and *Borrelia miyamotoi*Infection** > **Vote on Potential Action Five:**Initiate studies to assess sequela and other post-infection symptomology as a result of either TBRF or BMD.
			Outcome: Passed—all present in favor; none opposed; none abstained; none absent (10/0/0/0)
			No11/27/2019
			Results > Priority Action 2: **Tick-Borne Relapsing Fever and *Borrelia miyamotoi*Infection** > **Vote on Potential Action Six:**Increase resources at the federal and state levels for assessing the incidence of TBRF and BMD.
			Outcome: Passed—all present in favor; none opposed; none abstained; none absent (10/0/0/0)
			No11/27/2019
			Results > Priority Action 2: **Tick-Borne Relapsing Fever and *Borrelia miyamotoi*Infection** > **Vote on Potential Action Seven:**Encourage CSTE to develop case criteria for inclusion of TBRF and BMD in the list of nationally reportable diseases.
			Outcome: Passed—9 in favor; none opposed; 1 abstained; none absent (9/0/1/0)
			No11/27/2019
			Results > Priority Action 2: **Tick-Borne Relapsing Fever and *Borrelia miyamotoi*Infection**> **Vote on Potential Action Eight:**Investigate whether TBRF or *B. miyamotoi* spirochetes persist as cultivable or uncultivable forms in different tissues, including the brain, and under what conditions, after antibiotic therapy in suitable animal models.
			Outcome: Passed—10 in favor; 0 opposed; none abstained; none absent (10/0/0/0)
			No11/27/2019
			Results > Priority Action 2: **Tick-Borne Relapsing Fever and *Borrelia miyamotoi*Infection** > **Vote on Potential Action Nine:**Allocate funds to recruit and encourage professionals in the study of soft ticks, TBRF, and BMD.
			Outcome: Passed—9 in favor; none opposed; 1 abstained; none absent (9/0/1/0)
			No11/27/2019
			Results > Priority Action 3: **Tick-Borne Viruses** > **Vote on Potential Action One:**Allocate resources and establish uniform reporting criteria for Colorado Tick fever virus, Heartland virus, and Bourbon virus. Encourage conversations between the Centers for Disease Control and Prevention and CSTE to make all TBVs nationally notifiable.
			Outcome: Passed—all present in favor; none opposed; none abstained; none absent (10/0/0/0)
			No11/27/2019
			Results > Priority Action 3: **Tick-Borne Viruses** > **Vote on Potential Action Two:**Identify and promote simple, rapid, and straightforward viral diagnostics and incorporate them into existing, commercially available, tick-borne disease panels.
			Outcome: Passed—all present in favor; none opposed; none abstained; none absent (10/0/0/0)
			No11/27/2019
			Results > Priority Action 3: **Tick-Borne Viruses**> **Vote on Potential Action Three:**Conduct serological surveys and clinical follow-up to determine the range of clinical presentations and outcomes following TBV infection.
			Outcome: Passed—all present in favor; none opposed; none abstained; none absent (10/0/0/0)
			No11/27/2019
			Results > Priority Action 3: **Tick-Borne Viruses** > **Vote on Potential Action Four:**Increase education to physicians and other healthcare providers on these uncommon diseases that have changing geographic distributions. If healthcare providers do not know about these diseases, they will never consider them in their diagnoses nor order tests for them.
			Outcome: Passed—all present in favor; none opposed; none abstained; none absent (10/0/0/0)
			No11/27/2019
			Results > Priority Action 3: **Tick-Borne Viruses** > **Vote on Potential Action Five:**Conduct research to better understand the relationship between virus perpetuation and human risk. Research efforts should include: long-term field studies of TBVs in relevant field locations as well as the use of existing collections of ticks and vertebrate specimens to determine the distribution of infection in space, in different tick species, and in putative vertebrate hosts.
			Outcome: Passed—9 in favor; none opposed; 1 abstained; none absent (9/0/1/0)
			No11/27/2019
			Results > Priority Action 3: **Tick-Borne Viruses**> **Vote on Potential Action Six:**Conduct laboratory experiments on virus-vector-vertebrate interactions to clarify molecular interactions that are critical to transmission and to identify weak points in transmission that could serve as targets for novel interventions.
			Outcome: Passed—all present in favor; none opposed; none abstained; none absent (10/0/0/0)
			No11/27/2019
			Results > Priority Action 3: **Tick-Borne Viruse**s > **Vote on Potential Action Seven:**Evaluate the potential role of the Asian longhorned tick, *Haemaphysalis longicornis,* in transmission of TBVs including laboratory and field studies to: evaluate host associations, particularly whether it will feed on humans; evaluate potential interactions between this tick species and important native tick vectors; e.g., *Ixodes scapularis* and *Amblyomma americanum*; and determine the potential for significant changes in the risks for different tick-borne diseases.
			Outcome: Passed—10 in favor; none opposed; 0 abstained; none absent (10/0/0/0)
			No11/27/2019
			Results > Priority Action 3: T**ick-Borne Viruses** > **Vote on Potential Action Eight:**Conduct experiments to determine the potential interactions between tick species where many different species coexist or are expected to coexist in the future. Expected increases or decreases in tick populations or species distributions have significant impacts on risk for different TBVs.
			Outcome: Passed—all present in favor; none opposed; none abstained; none absent (10/0/0/0)
			No11/27/2019
			Results > Priority Action 3: **Tick-Borne Viruses** > **Vote on Potential Action Nine:**Assess the role of multi-pathogen interactions within vectors and vertebrates and their impacts on transmission. These studies should include: defining the tick microbiome giving attention to tick species, location, life-stage, time of year, and infection status for known pathogens. Efforts should also focus on experimental studies to define the extent that pathogenic and apathogenic microbiota impact virus replication and transmission.
			Outcome: Passed—all present in favor; none opposed; none abstained; none absent (10/0/0/0)
			No11/27/2019
			Results > Priority Action 3: **Tick-Borne Viruses** > **Vote on Potential Action Ten:**Develop molecular and entomological tools to analyze vector pathogen interactions, such as antibodies against tick cell markers, and improved reverse genetic systems for tick-borne virus studies *in vivo*.
			Outcome: Passed—all present in favor; none opposed; none abstained; none absent (10/0/0/0)
			NoA PowerPoint briefing on subcommittee progress and accomplishments was presented virtually to the larger HHS Tick-Borne Diseases Working Group on September 12, 2019. A final PowerPoint briefing outlining key findings was presented to the larger HHS Tick-Borne Diseases Working Group on January 29, 2020. Both briefings initially drafted by the subcommittee co-chairs and the reviewed, revised, and approved by the entire subcommittee.

Potential Actions

Priority 1: Reduce Burden of Illness Due to Babesiosis in the United States Through Improved Diagnosis, Treatment, and Prevention

Summary of evidence/findings

Babesiosis is caused by a single-cell protozoal pathogen resulting in a malarial-like illness. Reported cases in the United States (U.S.) are increasing each year. Disease in humans is primarily caused by *Babesia microti* and, on rare occasions, *Babesia duncani*. *B. divergens-*like-MO-1 infrequently causes symptomatic disease. Patients may need to be tested for multiple *Babesia*species to ensure an accurate diagnosis. Transmission to humans is typically through the bite of an infected tick. Transfusion-associated congenital, and rarely solid organ transplantation can also occur. Most reported cases of babesiosis occur in the Northeast and upper Midwest where the *Babesia* pathogen is transmitted primarily by the blacklegged tick, *Ixodes scapularis*. Cases have also been reported in the Western U.S., primarily in California, Oregon and Washington, where transmission is less well understood but is thought to be via the winter tick, *Dermacentor albipictus*. Recent reports of the spread of *B. duncani* in other states need further confirmation.

Babesiosis in humans can range from an asymptomatic infection to a rapidly fatal disease. Symptoms are typically flu-like with fever, chills, sweats, myalgia, nausea, and fatigue that can be accompanied by high bilirubin, elevated liver functions, low hemoglobin, and low platelet counts. A cough and shortness of breath is also possible. Severe disease is more common in the elderly, immunocompromised, and asplenic patients for whom treatment can be challenging. Diagnosis can be performed by microscopy, serology, and molecular techniques. Treatment of babesiosis relies on the use of anti-protozoal agents and/or antibiotics, including atovaquone, azithromycin, clindamycin, and quinine. Treatment regimens are limited by the emergence of drug-resistant parasites, toxicity, and failure of drugs. Treatment failures are seen in clinical cases. Additional research is needed to find new, effective treatment protocols. Currently there is no vaccine to prevent babesiosis. Prevention relies on efforts to protect against the bites of infected ticks and screening of the blood supply in areas of risk.

Possible opportunities

There is a significant opportunity to prevent transfusion associated cases due to the introduction of Food & Drug Administration (FDA)-approved, blood supply screening, tests in states where tick-borne transmission of babesiosis is known to occur.

New technologies utilizing whole genome sequencing have led to a better understanding of *Babesia* genetics and taxonomy. Promising research is currently underway to identify more effective drugs for treating patients, particularly those who are immunocompromised.

Threats or challenges

Babesiosis is a nationally notifiable disease, although awareness of reporting requirements in non-endemic states is low. The need for more complete information on the geographic distribution, potential expansion of the range of different *Babesia* species, and risk of travel exposure could be addressed by more complete reporting.

There is a need for more effective therapeutics. There is a need for better understanding of the natural ecology, including the vectors and reservoirs for different *Babesia* species.

Potential Actions for the Working Group to Consider

The following Potential Actions should be considered as a means to reduce the burden of illness due to babesiosis in the U.S.

**Potential Action One:** Explore the utility of newly developed blood screening technologies for validation for clinical diagnostic use.

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			0**Potential Action Two:** Provide education to health care providers, including subspecialists and frontline providers (including but not limited to hospitalists, OB/GYN, and infectious disease doctors), in addition to family practice and internal medicine physicians, regarding the signs/symptoms/risks/laboratory evaluation/treatment challenges of babesiosis.

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			0**Potential Action Three:** Conduct laboratory research and clinical trials to evaluate new treatment regimens for babesiosis. New treatment regimen investigation should include research on immunotherapies (e.g., human monoclonal antibodies) or adjunctive therapies to control parasitemia while on drug treatment. New treatment regimens can be evaluated in animal models prior to clinical evaluation and human trials. Host factors are important therefore more research is needed to determine the best therapeutic regimen in conditions where chronic parasitemia may occur, in particular whether adjunctive therapy could be useful.

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			0**Potential Action Four:** Conduct research on the ecology and distribution of *B. duncani* and other *Babesia* species (e.g., MO-1) that might be pathogenic. To facilitate such research, development and validation of sensitive and specific serologic methods to detect exposure to *B. duncani* are needed.

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			0**Potential Action Five:**Educate state health departments on the Council of State and Territorial Epidemiologist (CSTE) case definitions and the importance of reporting for these nationally notifiable diseases to the species level.

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			0Priority 2: Reduce Tick-Borne Relapsing Fever and *Borrelia Miyamotoi*Infection in the United States

Summary of evidence/findings

Tick-borne relapsing fever (TBRF) is caused by bacterial infections with *Borrelia*species distinct from the newly renamed *Borreliella*agents known to cause Lyme disease. Symptoms typically include recurrent episodes of fever accompanied by headache, muscle and joint pains, and nausea. TBRF usually occur in the Western U.S. and is often associated with sleeping in rustic cabins that are infested with rodents. Soft ticks, of the genus *Ornithodoros*, infected with relapsing fever spirochetes transmit the disease to humans. These ticks are short-term, intermittent feeders that do not attach when they bite. The soft tick becomes infected with the relapsing fever spirochete when it feeds on an infected host, often a small rodent. If the infected tick then feeds on a human, it can transmit the relapsing fever spirochete and illness to humans. Transplacental infection of the human fetus has also been recognized.

One member of the genus *Borrelia*, *Borrelia miyamotoi*, also causes illness in humans. Unlike related spirochetes that cause TBRF and are transmitted by soft tick species, the main vector for BMD in the U.S. is a hard tick, the blacklegged tick. The blacklegged tick is also the vector of Lyme disease in Eastern and Central U.S. *B. miyamotoi* has also been found in the western blacklegged tick in the far Western U.S., however, there is currently no evidence of transmission of *B. miyamotoi* to humans by this tick. Similar to *B. microti*, *B. miyamotoi* can survive in human blood products. Active screening of the blood supply is needed to decrease transfusion-related infection risk. The illness presents with fever but usually without other specific symptoms such as a rash, other localized symptoms, or recurring fever episodes. Immunocompromised individuals are at higher risk of complications.

Both TBRF and *B. miyamotoi* disease (BMD) can cause severe infections, however these can be treated with antibiotics and rarely, can be fatal. Fatality, though rare, is higher for TBRF during the first febrile episode. It is unknown if these diseases have persistent infections or symptomatology, nor how co-infection may affect treatment. Neither illness is nationally notifiable in the U.S.

Possible opportunities

Antibodies to TBRF and BMD do not cause positive results for either whole immunoassays or Western immunoblot tests for Lyme disease. However, C6 antibody testing for Lyme disease can react with antibodies to BMD, resulting in a false-positive result for Lyme disease. New approaches for the diagnosis of BMD that utilize the variable major protein (VMP) and the GlpQ protein may help increase sensitivity in early and convalescent illness. Newly developed Line Immunoblot Assays may be useful for laboratory confirmation of TBRF and BMD.

New technologies utilizing metagenomics have led to the detection of *B. miyamotoi* in patients with undifferentiated acute febrile illness. Recently initiated national tick surveillance activities may lead to a better understanding of the distribution and spread of enzootic BMD across the U.S. TBRF spirochetes and *B. miyamotoi* may be directly transmitted vertically from infected female ticks to their progeny (transovarial transmission) which does not occur with *Borrelia burgdorferi*. Larvae (as well as nymphs and adults) can transmit *B. miyamotoi* to wildlife and to human hosts.

In general, there is increasing recognition that tick-borne relapsing fever (TBRF) has been relatively neglected as a disease in North America, Africa, and Eurasia. Increased funding and resources can aid in the recruitment of professionals to study the many gaps in TBRF and BMD research.

Threats or challenges

Cases of TBRF and BMD are inconsistently reported in states where transmission is known to occur. Neither TBRF nor BMD is nationally notifiable. Consequently, the burden of illness in the U.S. is not known nor can it be easily determined. More information is needed about the geographic distribution of the agents that cause both TBRF and BMD. BMD occur in areas where Lyme disease also occurs leading to the possibility for co-infection with pathogens.

Potential Actions for the Working Group to Consider

The following Potential Actions should be considered as a means to achieve the priority of reducing TBRF and BMD as a public health threat.

**Potential Action One:** Improve public education on prevention of tick bites. Improve education of health care providers regarding clinical manifestations, diagnosis, treatment, modes of transmission, surveillance reporting, and preventive measures for the unique exposure risks of TBRF and *BMD.*

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			0**Potential Action Two:**Develop point-of-care testing, such as with a nucleic acid amplification test, to support the diagnosis of TBRF and BMD in their symptomatic stages.

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			0**Potential Action Three:**Develop immunodiagnostic assays to discriminate between TBRF*Borrelia* species and *B. miyamotoi.*

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			0**Potential Action Four:**Assess the effectiveness of alternatives to oral doxycycline and parenteral penicillin as treatments of TBRF and BMD, beginning first with *in vitro* testing and then animal models.

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			0**Potential Action Five:**Initiate studies to assess sequela and other post-infection symptomology as a result of either TBRF or BMD.

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			0**Potential Action Six:**Increase resources at the federal and state levels for assessing the incidence of TBRF and BMD.

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			0**Potential Action Seven:**Encourage CSTE to develop case criteria for inclusion of TBRF and BMD in the list of nationally reportable diseases.

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			0**Potential Action Eight:**Investigate whether TBRF or *B. miyamotoi* spirochetes persist as cultivable or uncultivable forms in different tissues, including the brain, and under what conditions, after antibiotic therapy in suitable animal models.

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			0**Potential Action Nine:** Allocate funds to recruit and encourage professionals in the study of soft ticks, TBRF, and BMD.

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			0Priority 3: Reduce Illness in the United States Due to Tick-Borne Viruses

Summary of evidence/findings

Tick-borne viruses (TBV) pose an important emerging human disease threat, resulting in severe illness and a small number of deaths in the U.S. each year. Most notable among these is Powassan virus (POWv), a flavivirus relative of the tick-borne encephalitis viruses (TBEv). Transmitted by *Ixodes scapularis, Ixodes cookei,* and several other *Ixodes* tick species, TBEVs are important causes of human illness in Europe and Asia. With the geographic expansion in the U.S. of the lone star tick, *Amblyomma americanum,* other tick-borne viruses have recently been identified and appear to be emerging. These include Heartland virus (HRTv) and Bourbon virus (BRBv). Colorado Tick fever virus (CTFv), transmitted by *Dermacentor* species ticks, causes sporadic illness mainly in the U.S. Mountain West region and may rarely be transmitted by blood transfusion. While other TBVs likely are present in the U.S., these four viruses represent the most significant public health threats.

As with other tick-borne agents, TBVs are zoonotic pathogens. Humans most frequently become infected through the bite of an infected tick. Some flaviviruses, such as West Nile virus and Zika virus, share many biological characteristics to POWv and have been shown to persist after acute infection. Although none have been reported to date, it is possible that POWv can establish a persistent infection in humans and/or be responsible for birth defects, but more research is required to answer these questions.

TBVs are maintained naturally in various animal reservoirs, providing a source of infection for ticks. The four TBVs mentioned are important human pathogens for different reasons – POWv, due to its rapid transmission (within 15 minutes of tick attachment), high case-fatality rate, and the increasing number of reported human infections; HRTv and BRBv due to their similarly high pathogenic potential; and CTFv due to its consistent presence in enzootic areas.

Possible opportunities

New technology utilizing metagenomics may be useful for identifying these and other, novel TBVs in both humans and animal reservoirs. Recently initiated national tick surveillance activities may lead to a better understanding of the enzootic distribution of TBVs across the U.S.

Threats or challenges

Increasing numbers of cases of POWv infection have been reported in the Northeastern and Upper Midwestern of the U.S. This emergence trend is similar to other tick-borne diseases that are associated with deer, rodents, and the blacklegged tick, *Ixodes scapularis*. In the absence of effective tick control strategies, this trend will likely continue.

HRTv and BRBv are recently discovered pathogens, therefore, little is known about their natural ecology. There is concern that the recently introduced Asian longhorned tick, *Haemaphysalis longicornis,* which is rapidly spreading in the U.S., could be a vector for HRTv both between animals and to humans. The Asian longhorn tick is a vector for a virus genetically similar to HRTv that causes severe fever with thrombocytopenia syndrome (SFTSv), a potentially fatal infection in Asia. In addition to HRTv, other pathogens and allergens have been shown to be transmissible by *H. longicornis*. To date, no human pathogens have been found in *H. longicornis*collected and tested in the U.S. Anecdotal evidence has shown that this tick, at least in lineages found in the U.S., does not have a preference for humans, though occasional bites have been reported (L. Eisen, personal communication, January 9, 2020).

Potential Actions for the Working Group to Consider

The following Potential Actions should be considered as a means to achieve the priority of reducing burden of illness associated with tick-borne viruses in the U.S.

**Potential Action One:** Allocate resources and establish uniform reporting criteria for Colorado Tick fever virus, Heartland virus, and Bourbon virus. Encourage conversations between the Centers for Disease Control and Prevention and CSTE to make all TBVs nationally notifiable.

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			0**Potential Action Two:** Identify and promote simple, rapid, and straightforward viral diagnostics and incorporate them into existing, commercially available, tick-borne disease panels.

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			0**Potential Action Three:** Conduct serological surveys and clinical follow-up to determine the range of clinical presentations and outcomes following TBV infection.

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			0**Potential Action Four:** Increase education to physicians and other healthcare providers on these uncommon diseases that have changing geographic distributions. If healthcare providers do not know about these diseases, they will never consider them in their diagnoses nor order tests for them.

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			0**Potential Action Five:** Conduct research to better understand the relationship between virus perpetuation and human risk. Research efforts should include: long-term field studies of TBVs in relevant field locations as well as the use of existing collections of ticks and vertebrate specimens to determine the distribution of infection in space, in different tick species, and in putative vertebrate hosts.

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			0**Potential Action Six:** Conduct laboratory experiments on virus-vector-vertebrate interactions to clarify molecular interactions that are critical to transmission and to identify weak points in transmission that could serve as targets for novel interventions.

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			0**Potential Action Seven.** Evaluate the potential role of the Asian longhorned tick, *Haemaphysalis longicornis,* in transmission of TBVs including laboratory and field studies to: evaluate host associations, particularly whether it will feed on humans; evaluate potential interactions between this tick species and important native tick vectors; e.g., *Ixodes scapularis* and *Amblyomma americanum*; and determine the potential for significant changes in the risks for different tick-borne diseases.

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			0**Potential Action Eight:** Conduct experiments to determine the potential interactions between tick species where many different species coexist or are expected to coexist in the future. Expected increases or decreases in tick populations or species distributions have significant impacts on risk for different TBVs.

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			0**Potential Action Nine:** Assess the role of multi-pathogen interactions within vectors and vertebrates and their impacts on transmission. These studies should include: defining the tick microbiome giving attention to tick species, location, life-stage, time of year, and infection status for known pathogens. Efforts should also focus on experimental studies to define the extent that pathogenic and apathogenic microbiota impact virus replication and transmission.

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			0**Potential Action Ten:** Develop molecular and entomological tools to analyze vector pathogen interactions, such as antibodies against tick cell markers, and improved reverse genetic systems for tick-borne virus studies *in vivo*.

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			0Priority 4: Reduce the Risk of Tularemia as a Public Health Threat in the United States

Summary of evidence/findings

Tularemia is caused by the bacterium *Francisella tularensis.* It is harbored in animals and can be transmitted to humans through a number of different pathways including the bites of infected ticks or deer flies, skin contact with infected animals, consuming contaminated food or water, or inhaling contaminated aerosols or dusts. The symptoms of tularemia can vary greatly depending on the route of exposure. Forms of the disease include ulceroglandular, glandular, oculoglandular, oropharyngeal, pneumonic, and typhoidal. The most serious form of infection is pneumonic, which can be rapidly fatal if not diagnosed and treated promptly.

Each year 100 – 200 cases of tularemia are reported in the U.S. The majority of these cases occur during the summer months and are associated with outdoor exposure. Over 70% of reported cases are either ulceroglandular or glandular, generally indicating that the infection was caused by the bite of an infected tick or deer fly.

Tularemia is classified as a U.S. Department of Health and Human Services (HHS) Tier 1 select agent due to its potential to be used as a weapon. Significant resources have previously been provided to enhance surveillance, diagnosis, and treatment. The select agent designation has dramatically limited research on tularemia.

Possible opportunities

New technology utilizing metagenomics may be useful for identifying *F. tularensis* in both humans and animal reservoirs. Recently initiated national tick surveillance activities may lead to a better understanding of the distribution of enzootic tularemia occurrence across the U.S.

Threats or challenges

Tularemia that does not manifest as ulceroglandular or glandular tularemia can be difficult to diagnose. It is a rare disease whose symptoms can be mistaken for other, more common, illnesses.

Potential Actions for the Working Group to Consider

The following Potential Actions should be considered as a means to achieve the priority of reducing the risk of tularemia as a public health threat in the U.S.

**Potential Action One:**Enhance education for healthcare providers to aid in appropriate diagnosis of potential tick-borne tularemia cases. This education would include epidemiology, natural history, signs and symptoms, preferred specimens and volumes for collection, and shipping requirements.

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			0**Potential Action Two:**Improve prevention education targeting high risk groups (e.g., hunters, anglers, ranchers, landscaping workers), especially in regions where transmission is known to occur.

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			0**Potential Action Three:**Include tularemia testing in multiplex systems that are used for testing field collected ticks as a part of a national tick surveillance system to provide better information on pathogen occurrence and distribution.

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			0**Potential Action Four:**Mitigate the administrative and legal effects of the Select Agent Rule to facilitate research on tularemia.

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			0Appendix A: Babesiosis

**Lead Authors:**Richard I. Horowitz (MD) and Sam R. Telford, III (SD, MS)

Executive Summary

*Babesia* is a single celled protozoal parasite that can be transmitted from a tick bite, blood transfusion, maternal-fetal transmission and/or solid organ transplantation. This parasitic infection is rapidly spreading throughout the United States (U.S.) and is frequently transmitted at the same time as Lyme disease, often worsening clinical symptomatology. Babesiosis is now the most commonly reported transfusion-transmitted protozoal infection in the U.S. Although most infections are subclinical or milder in younger individuals, advanced age, immunosuppression, and splenectomy increase the risk of critical and potentially fatal outcomes. Treatment failures have been reported with presently used medications and there is an urgent need to find new effective treatment protocols for both acute and chronically affected individuals.

Background

***Epidemiology****–***Two main species of *Babesia*are responsible for clinical illness in the U.S. - *Babesia microti* and *Babesia duncani*. *Babesia divergens-*like MO-1 rarely causes symptomatic disease therefore patients may not be diagnosed if tested for only one species (Herwaldt et al., 1996). There is also genetic diversity, variable number tandem repeat (VNTR marker) among human derived *B. microti* samples that could have implications for chronic illness or treatment efficacy (Goethert, Molloy, Berardi, Weeks & Telford, 2018). Some common *Babesia* species in the U.S. include:

*B. divergens* and *B. divergens*-like infections (including EU-1, MO-1) are primarily found in the U.S., Europe, Russia and China.
	*B. duncani* babesiosis is currently established in Western U.S. Understanding the ecology of this parasite and its tick vector, *Dermacentor albipictus* ̧ is needed to further delineate its distribution. Clinicians have recently reported *B. duncani*babesiosis in the Eastern U.S., however, additional confirmation is required. (Horowitz & Freeman, 2019).
	MO-1 babesiosis, caused by a *B. divergens*-like parasite, have sporadically been reported in the Southcentral and Midwestern (Missouri) U.S. as well as Kentucky and Washington (Herwaldt et al., 1996). The parasite is widely distributed throughout the U.S. in rabbits, but its presence in nature does not necessarily imply increased risk to humans. Recently a transfusion-associated MO-1 babesiosis was reported in Arkansas (Burgess et al., 2017).Due to regional distribution of *Babesia*species, it is important to obtain a detailed travel history in order to determine the risk of exposure from those species not present in the U.S. or more region specific *Babesia* species.

Treatment decisions may be influenced by the *Babesia*species and patient comorbidities. Treatment failures have been observed across the northeast, primarily in patients with associated comorbidities or immunosuppression where there is *B. microti* babesiosis. Lemieux et al. (2016) found mutations in the *cytb* and *rpl4* genes of *B. microti* from patients with resistant infections (these genes in *Plasmodia* are known to encode proteins with sites where atovaquone and azithromycin bind). Resistance to atovaquone and azithromycin is now commonly seen in clinical practice. Evidence to date is that this is due to selection within the host rather than an increase in the prevalence of resistant strains in nature. Additional research is needed to identify more effective treatment protocols. Ineffective treatment can increase inflammation by increasing nitric oxide resulting in more inflammatory cytokine production and a worsening clinical picture. Nitric oxide can be stimulated by infections (as well as toxins and trauma), leading to increased levels of peroxynitrite. The oxidative stress that results stimulates NF-κB, subsequently increasing inflammatory cytokines, such as IL-1, IL-6, IL-8, TNF-α, IFNγ. These contribute to increased signs and symptoms seen with tick-borne illness. Additional research is needed to reduce cellular damage caused by inflammation.

***Clinical Picture/Syndromic Surveillance**********–***The genus *Babesia* comprises over 100 species of tick-transmitted protozoal pathogens (piroplasms). The most common human pathogens in the U.S. are *B. microti*, *B. duncani* (WA-1), and *B. divergens-*like MO-1 (found in Arkansas, Kentucky, Missouri, and Washington).

Infection with *Borrelia burgdorferi*, the causative agent of Lyme disease,**increases the frequency of *B. microti*carriage in ticks. *B. microti*is often transmitted with Lyme disease. Serological studies indicate that coinfection with *B. burgdorferi*and *B. microti*and is common in humans (Curcio, Tria & Gucwa, 2016). In endemic regions, almost 20% of Lyme disease patients reported concurrent babesiosis; up to 25% of babesiosis patients also had Lyme disease (Diuk-Wasser, Vannier & Krause, 2016). A large percentage of patients with chronic/post-treatment Lyme disease syndrome (52%) also show evidence of past or active *B. microti* infection (Horowitz & Freeman, 2019). Surveillance data from the Centers for Disease Control and Prevention (CDC) have shown a rapid geographic expansion and an increase in number of reported cases of babesiosis in Lyme endemic areas, such as Wisconsin, where the reported incidence of confirmed babesiosis has increased 26-fold between 2001 and 2015 (Stein, Elbadawi, Kazmierczak & Davis, 2017).

In the lower Hudson Valley of New York, Connecticut, Rhode Island, and Maine the number of reported cases has also significantly risen in the past several decades (Rodgers & Mather, 2007; Kogut et al., 2005; Krause et al., 1991; Smith et al., 2014; Krause et al., 2003). As many as two-thirds of New York residents with *Borrelia*-reactive sera have been found to have *Babesia*-reactive sera (Krause et al., 2002). A recent study by Sanchez-Vicente, Tagliafierro, Coleman, Benach & Tokarz (2019) found more than half the *Ixodes* deer ticks on Long Island were infected with *B. burgdorferi* followed by infections with the agents of babesiosis and anaplasmosis. Adult deer ticks are very poor vectors of *B. microti*, requiring up to five days for pathogen transmission, and are usually found and removed before transmitting *Babesia*. For nymphs however it is 2.5 days, increasing risk of transmitting *Babesia*. The East Hampton location surveyed in 2018 found 34% of deer tick nymphs and 8% of adult deer ticks collected were infected with *B. microti*. Statewide, as many as 26% of deer tick nymphs and 24% of adult deer ticks were infected by *B. microti* (Sanchez-Vicente et al., 2019). Nearly one-quarter of these ticks were infected with more than one agent, increasing the likelihood of simultaneous transmission of multiple agents from a single tick bite and increasing the risk of severe illness. Multidisciplinary approaches to controlling the spread of ticks are urgently needed in order to reduce the risk of severe illness (Sprong et. al., 2018).

Babesiosis is an emerging health threat in the U.S. Community-acquired and transfusion-transmitted babesiosis are increasing (Kumar, Fish & Krause, 2018). The number of reported cases of babesiosis has steadily increased from approximately 1100 cases in 2011, to nearly 1800 cases in 2014, and almost 2400 in 2017 (Centers for Disease Control and Prevention [CDC], 2019).

A recent, statistically-validated, Lyme disease questionnaire, the Horowitz Multiple Systemic Infectious Disease Syndrome Questionnaire (HMQ), contained two questions (questions 1 and 22) related to symptoms of babesiosis - “Any patient who complains of unexplained fevers, day and night sweats, chills, flushing, an unexplained cough, and shortness of breath (“air hunger”) may have a concomitant infection with *Babesia.*” (Mylonakis, 2001; Horowitz, Coletta & Fein, 1994; Knapp & Rice, 2015; Citera, Freeman & Horowitz, 2017). Five factors consistent with Lyme disease co-infection were seen on the HMQ: fatigue, flu-like symptoms, joint stiffness, tingling, and concentration problems. Migratory joint/muscle/nerve pain was found to be highly correlated with exposure to Lyme disease, once other causes were ruled out.

The HMQ is predictive in clinical practice and has been statistically validated. A score > 63 on the questionnaire indicates a high probability of Lyme disease. A score between 45 and 62 indicates a probably case of Lyme disease. A score between 25 and 44 indicates a possible case of Lyme disease. Healthy individuals scored below 24. A high score on the questionnaire, with positive responses to questions one and 22 in section one, increase the pretest probability of exposure to babesiosis, apart from exposure to Lyme disease.

Based on these findings, clinicians should evaluate for the sudden onset of babesiosis symptoms, such as fevers, sweats, shaking chills, fatigue, headaches, and myalgias. Respiratory symptoms including an unexplained cough and shortness of breath (“air hunger”) have also been observed. In rare cases, splenic rupture has been found (Li et. al., 2018). A *Babesia*laboratory panel approach, including a Giemsa stain as well as DNA and RNA based methods, may help establish a diagnosis of babesiosis and rule out other causes of these symptoms.

***Laboratory Evaluation**–*Malarial-like symptoms can be seen with or without associated laboratory abnormalities including leucopenia, thrombocytopenia, transaminitis, and hemolytic anemia. Patients who are co-infected and/or with low levels of parasitemia may therefore not present with the classical symptoms of babesiosis (i.e., anemia, leucopenia, thrombocytopenia, transaminitis). Due to the possibility of chronic, low-level parasitemia and the dynamic nature of stressors that might allow the expression of pathology, untreated babesiosis may relapse under certain conditions. For example, splenectomy and immunosuppression lead to severe illness which including immunodeficiencies, resulting from B-cell lymphomas, organ transplants, HIV/AIDS, or treatment with immunosuppressive drugs, such as Rituximab (Parveen & Bhanot, 2019; Raffalli & Wormser, 2016). Severe disease is also seen in hospitalized patients with concurrent illnesses, including chronic conditions such as diabetes, congestive heart failure and renal failure (Fida, Challener, Hamdi, O’Horo & Saleh, 2019). Immunodeficiencies, concurrent illnesses, and coinfection with *Borrelia* species or *Anaplasma* species heighten the risk for babesiosis, increase the chances of severe symptoms, and have a higher chance at hospitalization. In these cases, diagnoses tend to be easily confirmed with a blood smear.

*Babesia* are increasingly appreciated as a cause of transfusion-transmitted infection. Babesiosis is now the most commonly reported transfusion-transmitted protozoal infection in the U.S. (Bloch, Kumar & Krause, 2019). Chagas disease and malaria are others. Babesiosis transfusion-transmitted infections are fatal in approximately 20% of cases (Vannier, Diuk-Wasser, Mamoun & Krause, 2015). Most infections are subclinical or mild therefore patients often do not seek treatment and their parasitemia may persist for months. Infected donors are often asymptomatic and the resulting risk of transfusion-transmitted parasitemia is frequently below the level of detection achievable by nucleic acid testing (NAT). Of 1,661,281 blood donations in 2018, 0.38% contained evidence of a *Babesia* infection (Moritz et al., 2016). Of these, 0.38%, 20% contained *B. microti* DNA, suggesting that viable parasites are a transfusion hazard. *B. microti* is the most common transfusion-associated *Babesia*species in the U.S.; *B. duncani* is rarely implicated (Moritz et al., 2016). In 2017, a patient with asplenia and multiple red blood cell transfusions, with no known tick exposure, acquired a babesiosis infection with *B. divergens-*like/MO-1 (Burgess et. al., 2017).

Routine screening of blood units is not done everywhere. The Food and Drug Administration (FDA) has recommended targeted screening of the blood supply, focusing on states with high endemic risk (Food and Drug Administration [FDA], 2019). The Grifols Procleix assay, targeting four known zoonotic *Babesia* species ribosomal RNA NAT, has been approved by the FDA for direct detection of the parasite within blood units and in donor tissues. An antibody-based test remains to be approved but would be useful given cost considerations and as a complement to NAT, specifically when parasitemia of the blood unit may be below the NAT limit of detection. NAT has advantages over antibody tests for detecting parasitemia in early infections because there is a window during which antibodies are not detectable. In addition, given the non-specificity of serology for *B. duncani* given current assays, NAT would be the only means of screening for this infection.

***Pathology/Pathophysiology*****– Symptoms are typically flu-like with fever, chills, sweats, myalgia, nausea, and fatigue that can be accompanied by high bilirubin, elevated liver functions, low hemoglobin, and low platelet counts (Nassar & Richter, 2017). Apart from causing a hemolytic anemia, atypical symptoms include an unexplained cough, air hunger, acute respiratory distress syndrome (ARDS) (avoid steroids), and warm autoimmune hemolytic anemia (Alvarez De Leon et. al., 2019). Severe hemolytic anemia as a presenting complaint has been reported in immunocompetent patients with intact spleens. Advanced age, immunosuppression, and splenectomy increase the risk of critical outcomes in patients. In a recent case series of 22 patients with babesiosis in the medical intensive care unit, eight (36.4%; 95% CI: 19.7–57.0%) had ARDS, and three patients (37.5%) died.

Pathophysiology of babesiosis includes potentially adverse effects on treatment of Lyme disease. *B. microti* coinfection appears to enhance the severity of Lyme disease-like symptoms in both human and animal models, although inconsistent outcomes in different human and animal studies point to the need for further investigation (Krause, Telford & Spielman, 1996; Djokic et.al., 2019; Bhanot & Parveen, 2019). Effective control of *B. burgdorferi* infection depends on a Th2 CD4+ T-cell response within regional lymph nodes. Co-infection with *B. microti* may influence T-cells toward a Th1 response. Th1 cell-mediated immunity appears to be important in clearance of this intracellular pathogen (Djokic, Akoolo & Parveen, 2018). Suppressed immune responses can also be seen with parasites. Infection with *Babesia*species impairs other parasite clearance including nematodes, like *Trichuris*, and trypanosomes. There are immunosuppressive effects of *B. microti* infections on the maintenance of co-infecting agents.

***Treatment*********– Treatment regimens for babesiosis are limited by the *in vivo* emergence of drug-resistant parasites, toxicity, and drug failure (Genda et al., 2016; Krause et al., 2000; Lawres et al., 2016). The most common pharmacological treatment regimens for the treatment of babesiosis are listed below:

**Table 7: Human Babesiosis Pharmacological Treatment Regimens**

Patient
			Dosing RegimenAdults and Children
			Atovaquone and azithromycin (oral) twice a day; or

			Clindamycin (oral or IV) every eight hours with Quinine (oral) every six hours. Dosing is dependent on body weight.An increase in parasite resistance as well as the number of relapsed, immunocompromised, and asplenic individuals have made widely used anti-babesial treatment regimens, like atovaquone and azithromycin, less effective necessitating the need to develop new and effective therapies (Wormser et al., 2010; Simon et al., 2017; Lemieux et al., 2016). The discovery of new drug targets, such as peptide inhibitors that are selective for the parasite proteasome, offer potential new anti-babesial drugs (Jaloveckaa et al., 2018).

Adding high dose trimethoprim/sulfamethoxazole to clindamycin and quinine or atovaquone and azithromycin may be useful adjuncts to combination therapy in the treatment of resistant babesiosis. Antimalarial drugs, such as mefloquine with artemisinin-based drugs, used against *Plasmodium falciparum,*also have some efficacy in treating resistant babesiosis however the mechanism of action is poorly understood due to metabolic differences between the parasites. Clinicians need to pay particular attention to prevent potential drug interactions and side effects that could affect the QT interval on the electrocardiogram (Tickell-Paintera, Maayan, Saunders, Pace & Sinclair, 2017; Martin, Rogalski & Black; 1997; Nachimuthu, Assar & Schussler, 2012). A similar drug molecule, tafenoquine, has recently been approved by the FDA for prophylaxis of malaria in adults. There are currently no human studies on tafenoquine’s efficacy in preventing or treating babesiosis in humans. In a SCID mouse model of babesiosis, tafenoquine demonstrated excellent parasiticidal effect (Mordue & Wormser, 2019). Similarly, ELQ-300 prodrugs for malaria have not yet been tested regarding their efficacy in patients with babesiosis (Miley et al., 2015).

Newer treatment protocols for babesiosis have recently been published. Mycobacterial drugs, like dapsone, with antimalarial activity have been demonstrated to be helpful in those failing classical therapy for Lyme disease with associated babesiosis (Horowitz & Freeman, 2019; Horowitz & Freeman, 2016).

Newer combinations of endochin-like quinolones and atovaquone have been shown to be effective in animal models, but have yet to be tested in human clinical trials. Disulfiram, a sulfa based drug molecule, was recently reported to be effective in a small case series of patients with resistant Lyme and babesiosis, but larger, well controlled trials are need (Liegner, 2019).

***Evidence for persistent infection/chronic symptomatology/chronic co-infection***– Persistent infection leading to chronic symptomatology has been reported (Wormser et al., 2010; Krause et al., 1998; Krause et al., 2008; Lemieux et al., 2016; Allred, 2003; Djokic et al., 2018; Horowitz, 1999, Horowitz & Freeman, 2019). In many animal models, infection lasts for the duration of life.

Gaps in Knowledge and/or Data

Splenectomy and immunosuppression lead to severe illness, including immunodeficiencies resulting from B-cell lymphomas, organ transplants, HIV/AIDS, or treatment with immunosuppressive drugs, such as Rituximab (Raffalli & Wormser, 2016; Parveen & Bhanot, 2019; Mareedu et al., 2017). What is the mechanism or pathophysiology that explains these differences in clinical symptoms and confirmatory laboratory testing?
	While NATs are the preferred method of detection during the window-period of parasitemia, antibody tests can detect infected subjects during periods of low-level parasitemia (Cheng et al., 2018; Levin et al., 2014). The development of antibody-based screening to economically focus NAT use as a strategy to eliminate infected blood units is needed.Sensitive and specific antibody tests and validation thereof for *B. duncani* exposure.
	A better understanding for the mechanism of action of drugs with empirical efficacy (disulfiram, dapsone, artemisinin, mefloquine) for which there is no known metabolic pathway target in *Babesia* species. (It is possible that these drugs do not act on the parasite, but instead regulate downstream inflammatory cytokines.)
	Prospective cohort studies are needed to determine whether and how frequently signs and symptoms might sporadically be found.Opportunities

Transmission of *Babesia* takes place primarily through tick bites, however, it is also possible to acquire the infection by blood transfusion, solid organ transplantation, and maternal-fetal transmission (Horowitz & Freeman, 2020). Certain groups are particularly at risk and more prone to the effects of babesiosis. Neonates, children under one year of age, and the elderly are particularly high-risk groups.

Age-related pathology is seen in babesiosis, similar to anaplasmosis, with a worsening of the clinical picture if a patient is splenectomized, immuncompromised, or has a co-infection (Rosner, Zarrabi, Benach & Habicht, 1984; White et al., 1998; Hatcher, Greenberg, Antique & Jimenez-Lucho, 2001; Krause et al., 2008). Physician education is needed to identify the risk of babesiosis in specific age groups with these medical conditions. This includes the judicious use of steroids because death due to reactivation of latent babesia infections with high-dose corticosteroid therapy has been reported (Herwaldt et al., 1995; Callow & Parker, 1969; Hussein, 1984).

Red Cross, or other blood sources, should be screened and considered for those requiring a transfusion, especially if the patient has comorbid conditions and/or is immunosuppressed (FDA, 2019). *Babesia* has also been reported to be transmitted by solid organ transplantation. Physician education is needed to help stratify risk as well as identify symptoms and potential risk factors post transfusion/transplantation.

*OB-GYN*: Serious clinical disease associated with *Babesia*infection are a risk to pregnant patients and require education of obstetrician, gynecologists, and midwives. HELLP Syndrome (hemolysis, elevated liver enzymes, low platelet count) can be confused with babesiosis and education about the differences is needed (CDC, 2019; Khangura, Williams, Cooper & Prabulos, 2019; Mupombwa, Mulla & Kirby, 2016). Mothers with gestational Lyme disease and subclinical babesiosis can still transmit *Babesia* resulting in the fetuses requiring a transfusion (Saetre et al., 2018). Physician education is needed to establish proper diagnosis and to understand the risks and benefits of various drug treatments during pregnancy (Luckett, Rodriguez & Katz, 2014). Treatment in pregnancy includes clindamycin plus quinine for 7 days and has been shown to be effective/safe in the third trimester (Feder, Lawlor & Krause, 2003; McGready et al., 2002). High dose quinine can cause abortion in the first trimester (“Quinine”, 2019). In a published case report of a multiparous woman with a history of Lyme disease and active babesiosis, transmission of babesiosis from the mother to the baby did not occur during two consecutive pregnancies when the mother was treated with clindamycin and/or atovaquone and azithromycin during the third trimester (Horowitz & Freeman, 2020).

Animal models and a defined clinical case definition creating a cohort are needed in order to study pathophysiology and mechanism of disease.

Potential Actions for the Working Group to Consider

The subcommittee identified five potential actions that the federal government could take to reduce the burden of illness due to babesiosis in the U.S.

**Potential Action One:** Explore the utility of newly developed blood screening technologies and validation for clinical diagnostic use.

**Potential Action Two:** Provide education to health care providers, including subspecialists and frontline providers (including but not limited to hospitalists, OB/GYN, and infectious disease doctors), in addition to family practice and internal medicine physicians, regarding the signs/symptoms/risks/ laboratory evaluation/treatment challenges of babesiosis.

**Potential Action Three:** Conduct laboratory research and clinical trials to evaluate new treatment regimens for babesiosis. New treatment regimen investigation should include research on immunotherapies (e.g., human monoclonal antibodies) or adjunctive therapies to control parasitemia while on drug treatment. New treatment regimens can be evaluated in animal models prior to clinical evaluation and human trials. Host factors are important therefore more research is needed to determine the best therapeutic regimen in conditions where chronic parasitemia may occur, in particular whether adjunctive therapy could be useful.

**Potential Action Four:** Conduct research on the ecology and distribution of *B. duncani* and other *Babesia* species (e.g., MO-1) that might be pathogenic. To facilitate such research, development and validation of sensitive and specific serologic methods to detect exposure to *B. duncani* are needed.

**Potential Action Five:**Educate state health departments on the Council of State and Territorial Epidemiologist (CSTE) case definitions and the importance of reporting for these nationally notifiable diseases to the species level.

Votes of Subcommittee Members

Potential actions were presented and discussed by subcommittee members. The wording of potential actions here were voted on by subcommittee members and results are presented here.

**Potential Action One:** Explore the utility of newly developed blood screening technologies for validation for clinical diagnostic use.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Two:** Provide education to health care providers, including subspecialists and frontline providers (including but not limited to hospitalists, OB/GYN, and infectious disease doctors), in addition to family practice and internal medicine physicians, regarding the signs/symptoms/risks/laboratory evaluation/treatment challenges of babesiosis.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Three:** Conduct laboratory research and clinical trials to evaluate new treatment regimens for babesiosis. New treatment regimen investigation should include research on immunotherapies (e.g., human monoclonal antibodies) or adjunctive therapies to control parasitemia while on drug treatment. New treatment regimens can be evaluated in animal models prior to clinical evaluation and human trials. Host factors are important therefore more research is needed to determine the best therapeutic regimen in conditions where chronic parasitemia may occur, in particular whether adjunctive therapy could be useful.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Four:** Conduct research on the ecology and distribution of *B. duncani* and other *Babesia* species (e.g., MO-1) that might be pathogenic. To facilitate such research, development and validation of sensitive and specific serologic methods to detect exposure to *B. duncani* are needed.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Five:**Educate state health departments on the Council of State and Territorial Epidemiologist (CSTE) case definitions and the importance of reporting for these nationally notifiable diseases to the species level.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent8
			0
			2
			0References

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Appendix B: Tick-Borne Relapsing Fever and Borrelia miyamotoi Infection

**Lead Authors:**Alan G. Barbour (MD) and Monica White

Summary

The family *Borreliaceae* comprises the multi-species genera *Borrelia* and*Borreliella* (Barbour, 2018a). The genus *Borrelia* contains all known agents of tick-borne relapsing fever (TBRF) and *Borrelia miyamotoi* (the agent of *Borrelia miyamotoi*disease [BMD]), as well as the agents of some diseases of domestic animals (Barbour & Schwan, 2018). TBRF and BMD can cause serious infections characterized by a sepsis-like state. Although both infections are treatable with antibiotics, these illnesses often result in hospitalization. Few laboratory tests are available for the diagnosis of TBRF and BMD; these diseases are often misdiagnosed as other infections. With some exceptions, the antigens of TBRF and BMD pathogens do not cross react with antigens of *Borrelia burgdorferi*, the causative agent of Lyme disease, in tests for antibodies. The GlpQ antigen assay can be used to distinguish these infections from Lyme disease in the laboratory, but it cannot distinguish TBRF from BMD. New assays are under development but evaluation of these is incomplete. There are significant needs in our understanding of the ecology, epidemiology, and burden of illness for both TBRF and BMD, largely due to the sporadic nature of these illnesses and the fact that neither disease is nationally notifiable.

Background

***Epidemiology – Tick-borne relapsing fever –***TBRF is a zoonotic infection caused by spirochete bacteria in the genus *Borrelia*that are transmitted to people through the bite of an infected soft tick, such as *Ornithodoros hermsii*. Unlike hard ticks, soft ticks feed briefly before detaching (usually less than 30 minutes) and the painless bites typically go unnoticed (Dworkin, Schwan & Anderson, 2002). Two *Borrelia* species cause the majority of reported TBRF cases in the United States (U.S.) - *Borrelia hermsii*, whose range includes much of the mountainous West; and *Borrelia turicatae*, which mainly occurs in the Southwestern United States (U.S.) and in more arid environments and at lower altitudes than *B. hermsii*. Other possible agents of TBRF in North America are *Borrelia parkeri*, a close relative of *B. turicatae;* *Borrelia coriaceae*, which is associated with deer; and a newly identified organism provisionally named “*Borrelia johnsonii*” (Schwan et al., 2005; Lane, Mun, Parker & White, 2005; Schwan, Raffel, Schrumpf, Gill & Piesman, 2009). There is much less information on the frequencies and consequences of human infection, if any, caused by the latter three organisms or possibly other novel species.

Compared to hard ticks, like the blacklegged tick *Ixodes scapularis*, locating and collecting the soft tick vectors of TBRF is very challenging (Johnson, Fischer, Raffel & Schwan, 2016; Schwan, Raffel, Schrumpf & Porcella, 2007). Unlike hard ticks, most soft tick species usually feed on humans at night and do not remain attached for hours to days at a time. Largely associated with the nests of their hosts -usually rodents, but also bats, pigs, and other domestic animals living in or around human habitats; soft ticks are much less accessible for collection than hard ticks. The applications of current technologies, such as terrestrial drones or telemetry, for tracking and locating animals, nests, and the infesting ticks has been very limited.

Only a few places in the U.S. conduct research on the soft ticks that transmit diseases of humans, domestic animals, or wildlife. Only a handful of soft tick colonies still exist, and are maintained, for research purposes. Few active entomologists or vector biologists have active research programs on soft ticks or TBRF. Many of these experts have passed away or retired. There have been relatively few studies on the effectiveness of currently available repellents, such as DEET, on preventing soft tick bites, or on the comparative effectiveness of different measures to eliminate tick infestations from houses and other habitats. Without corrective action, tick-infested cabins, barns, and other dwellings will remain a source for human infection for years to come.

In comparison to Lyme disease and other nationally notifiable tick-borne diseases, the incidences of TBRF and BMD are unevenly recorded due to inconsistent reporting requirements across the country, even in endemic states. There have been serosurveys of the prevalence of antibodies to *B. miyamotoi* in the U.S.; however, no comparable serological study of antibodies to either *B. hermsii*, *B. turicatae,*or other TBRF species in areas of low and high risk in North America exist (Krause et al., 2014). Several major challenges inhibit such studies. One challenge is the distribution of *B. hermsii*, *B. coriaceae*, and *B. miyamotoi*, in an area such as the foothills of the Sierra Nevada mountains in California, overlap making speciation of the TBRF spirochetes difficult. In addition, antigenic cross-reactivity among the TBRF agents in the immunoassays for antibodies to recombinant GlpQ protein, the expression of which distinguishes the *Borrelia* species from the genus *Borreliella* and its Lyme disease agents, further complicates studies (Schwan et al., 2003). Finally, false positive reactions for BMD with the C6 peptide assay, generally considered specific for *B. burgdorferi* infection, have recently been reported (Molloy, Weeks, Todd & Wormser, 2018).

***Epidemiology – Borrelia miyamotoi disease –****B. miyamotoi* is transmitted by certain hard tick *Ixodes* species in North America and Eurasia. *B. miyamotoi* causes infections in humans that are similar in the clinical features of relapsing fever but generally less severe (Krause et al., 2013; Wagemakers, Staarink, Sprong & Hovius, 2015). Similar to Lyme disease, *B. miyamotoi* is acquired through outdoor activities and contact with hard ticks in forested or shrubby areas during recreation, work, or activities around the home. In areas were *B. miyamotoi* and *B. burgdorferi*coexist, the prevalence of antibodies to the former is about one third that to the latter among residents (Krause et al., 2014).

***Clinical Picture/Syndromic Surveillance – Tick-borne relapsing fever***– TBRF is characterized by a sudden onset of fever followed by an afebrile period then recurrent febrile episodes with temperatures as high as 430C. The typical incubation period ranges from three to 12 days. The first fever episode may last three to seven days and is followed by an abrupt, and brief, crisis phase that typically lasts less than an hour. During this time, the fever continues to rise, pulse and blood pressure increase, and rigors occur. The crisis phase is followed by decreasing temperature, profuse diaphoresis, and hypotension. Symptoms can reoccur with alternating febrile and afebrile periods, lasting roughly three days for febrile and seven days for afebrile episodes. This pattern of relapsing fevers is characteristic of this illness. Mortality for untreated infections can range from four to 10 percent and is most common during, or directly following, the crisis phase. Recurrent febrile episodes in TBRF are caused by a succession of *Borrelia* serotypes circulating in the blood. Each serotype is antigenically distinct and defined by specific surface lipoproteins called variable major proteins (VMPS) (Dai et al., 2006).

A variety of other constitutional signs and symptoms may also be present during both the initial and subsequent febrile periods. These include headache, myalgia, arthralgia, chills, fatigue, vomiting, and abdominal pain. The occurrence of unspecified febrile illness and symptoms may be indistinguishable from those of many other types of infection, including viral infections. Often the characteristic fever pattern of relapsing fever may lead to an accurate diagnosis.

TBRF may have consequences beyond the acute febrile illness with constitutional symptoms. Relapsing fever spirochetes can also cross the maternal-fetal barrier causing placental damage and inflammation that leads to intrauterine growth retardation and congenital infection (Larsson, Andersson, Guo, et al., 2006). Some species of *Borrelia*, such as *B. turicatae* in North America and *Borrelia duttonii* in Africa, have prominent neurological manifestations, such as Bell’s (facial) palsy, or a meningoencephalitis (Cadavid & Barbour, 1998). In experimental animal models, relapsing fever spirochetes have been found to persist in the brain (Cadavid, Sondey, Garcia & Lawson, 2006; Larsson, Andersson, Pelkonen, et al., 2006). These can be eliminated in the mouse model by some antibiotic regimens but not by others (Kazragis, Dever, Jorgensen & Barbour, 1996). There is scant reported information on whether TBRF agents can persist in the central nervous system or other immune-privileged sites, such as the testes, in humans (Shamaei-Tousi, Collin, Bergh & Bergstrom, 2001).

***Clinical Picture/Syndromic Surveillance – Borrelia miyamotoi disease -***Patients with BMD most commonly present with fever, chills, and headache. Other symptoms may include fatigue, myalgia, and arthralgia (Krause, Fish, Narasimhan & Barbour, 2015; Molloy et al., 2015). Rash is uncommon. The incubation period between tick bite and the onset of symptoms ranges from three to 40 days (Chowdri et al., 2013). Clinical manifestations can also be significantly affected by immune status and the occurrence of underlying illness (Gugliotta, Goethert, Berardi & Telford, 2013; Wormser, Shapiro & Fish, 2019). Patients with an untreated illness may occasionally develop recurrent fever episodes that are similar to those seen in TBRF (Molloy et al., 2015). Clinical symptoms of BMD are often indistinguishable from those of other tick-borne diseases, including babesiosis, early Lyme disease without a rash, and human granulocytic anaplasmosis (Krause, Fish, et al., 2015). Depending on the time of year, BMD may be misdiagnosed as influenza. Serious illness requiring hospitalization seems to be more common, however, than for early Lyme disease.

***Laboratory Evaluation – Tick-borne relapsing fever***– Diagnosis of TBRF can readily be accomplished by direct visualization of spirochetes in peripheral blood due to the high concentrations of circulating spirochetes during febrile episodes. This is performed microscopically using either dark field microscopy or a stained peripheral blood smears stained by the Wright or Giemsa method. A stained blood smear is the primary diagnostic test to confirm TBRF, as well as babesiosis. The timing of blood sampling, level of parasitemia, and the experience/skill of the observer all play into the effectiveness for detection. However, expertise in preparing and analyzing parasitological blood smears may not be locally available. Other methods for direct diagnosis include PCR and culture. There are PCR assays available through some commercial reference laboratories, however, these require shipment of the specimen, usually to another state, and there is a delay in obtaining results for the management of the acutely ill patient.

Due to the lack of standardization and variable results between laboratories, serological testing for TBRF is of limited value. Additionally, serum that is evaluated early in illness, before antibodies have had sufficient time to develop, may be negative. Consequently, paired acute and convalescent sera are required for accurate serological diagnosis. Some patients with TBRF may also test positive for Lyme disease in the whole cell-based assays that constitute the first tier in a two-tier testing protocol. This is due to the similarity of some proteins between the causative organisms. TBRF should be considered as a possible diagnosis for patients with positive Lyme disease serology who have not been in areas where Lyme disease is known to occur (Centers for Disease Control and Prevention [CDC], 2018).

Blood culture and subsequent PCR testing allows differentiation of the *Borrelia* species that cause TBRF. TBRF cases acquired in Western states, at higher elevations, are typically due to *B. hermsii*. Infections acquired in Southern states, particularly Florida or Texas, at lower elevations, are typically due to *B. turicatae* (CDC, 2018). Other antibody-based assays, such as a line immunoblot test, are under development and evaluation (Shah et al., 2019).

***Laboratory Evaluation – Borrelia miyamotoi disease –***Patients with known tick exposure, who live in areas where *B. miyamotoi* is considered endemic, and who present with non-specific febrile illness, should be evaluated for BMD. Diagnosis can be made by PCR detection of *B. miyamotoi* DNA in peripheral blood or cerebrospinal fluid. Serologic testing of acute and convalescent serum can also be performed, utilizing tests that are specific for the *B. miyamotoi* GlpQ antigen (Krause et al., 2013; Krause, Fish, et al., 2015). Both PCR and serologic tests are available commercially, but have not been widely adopted by clinical laboratories.

***Pathology/Pathophysiology – Tick-borne relapsing fever & Borrelia miyamotoi disease*** – TBRF and BMD are primarily infections of the blood. Symptoms are similar to what occurs in septic shock due to an outpouring of inflammatory molecules, such as cytokines, in response to the infection (Barbour, 2018b). Central nervous system invasion may occur in some cases. In TBRF, and probably in BMD, the recurrence, or persistence, of fever is explained by antigenic variation of surface proteins of the bacteria (Dai et al., 2006). This allows the pathogen to stay one step ahead of the immune system of the host by changing its bacterial cell wall. TBRF can be transmitted from the mother to fetus and may result in stillbirths, infection of the newborn, and more severe disease in the mother (Larsson et al., 2006). Transmission by blood transfusion of BMD is also possible (Krause, Hendrickson, Steeves & Fish, 2015).

***Treatment – Tick-borne relapsing fever***–******Treatment of TBRF******is with a tetracycline, such as oral doxycycline, or a penicillin, and usually given parenterally (Barbour, 2018b). These regimens have been used for decades, and are based on clinical experience rather than randomized clinical trials. Spirochetes disappear from the blood within a few hours of treatment. The death of the spirochetes, and the release of inflammation-eliciting cell components, may cause a moderate-to-severe Jarisch-Herxheimer reaction (JHR) with hypotension and other shock-like features (Barbour, 2018b). JHR can be life-threatening unless the patient is carefully monitored during first day of treatment (Barbour, 2018b). There is substantial evidence these therapies are effective for the majority of cases. Due to the sporadic and low number of cases, there has been little investigation, either in an animal model or in clinical trial, of newer or alternative antibiotic regimens, to reduce the severity of JHR or preventing post-therapy disability. A placebo-controlled trial found postexposure treatment with doxycycline to be effective in preventing TBRF (Moran-Gilad et al., 2013).

***Treatment – Borrelia miyamotoi disease***–******Doxycycline is the preferred antibiotic treatment of BMD (Krause, Fish, et al., 2015). It can be administered orally in dosages that are also effective for treating Lyme disease and anaplasmosis, which may be included initially in the differential diagnosis for illness. Amoxicillin and cefuroxime may be used in the case where doxycycline is contraindicated. Macrolides, such as azithromycin or clarithromycin, may also be effective. For treatment of more serious clinical presentations, such as meningoencephalitis, IV administered ceftriaxone has been shown to be effective, particularly in immunocompromised patients (Gugliotta et al., 2013). Most patients respond to treatment within two to three days.

***Evidence for persistent infection/chronic symptomatology/chronic co-infections –*** In animal models of TBRF, bacteria may persist in the brain long after the pathogen has been cleared from the blood (Cadavid and Barbour, 19988; Cadavid et al., 2006). Post-treatment residual symptoms and disability have been recognized in a minority of patients with early phase Lyme disease (Aucott, Crowder & Kortte, 2013). There has been little follow-up of the outcome of treatment of TBRF to assess whether persistence of bacteria or a post-infection syndrome, such as occurs after some other infectious diseases like Chikungunya virus, may prolong convalescence or delay full recovery (Gerardin et al., 2011).

Gaps in Knowledge

The true incidence of TBRF and BMD in the U.S. is not known because of the lack of physician recognition and testing of the disease as well as inconsistent reporting requirements across states where these zoonotic infections occur. In comparison to Lyme disease, there have been few serological surveys to estimate risk of infection. Neither infection is nationally reportable.
	Unlike Lyme disease and, to a lesser extent BMD, for which there have been serological surveys of at-risk and control populations in North America and Europe, there are no study of the prevalence of antibodies to TBRF agents. Serological studies are difficult due to antigenic cross-reactivity between TBRF agents, like *B. hermsii*, and *B. miyamotoi*, that limit available immunoassays in practice.
	Direct visualization in a properly-prepared and thoroughly-examined blood smear remains the gold-standard for laboratory diagnosis for TBRF; this is seldom achieved in practice. The timing of blood sampling, level of parasitemia, and the experience/skill of the observer all determine the effectiveness of microscopy for detection. Point-of-care rapid tests, such as a nucleic acid amplification test (NAAT), have limited availability. Expanding the use of NAATs would be beneficial to early and accurate diagnosis.
	While *B. hermsii* and *B. turicatae* are established as important agents of TBRF in the U.S., there is less information on the causative role, if any or to what extent, of *B. parkeri*, *B. coriaceae*, and *Candidatus Borrelia johnsonii*, and possibly other TBRF *Borrelia* species in human disease in their areas of enzootic transmission.
	Chronic or persistent forms of TBRF or BMD have not been documented in the literature due to a lack of rigorously evaluated, systematic follow-up, of cases; a lack of retrospective case-control studies in endemic areas, and a lack of experimental animal models using state-of-art methods. The frequency of a post-infection syndrome, like Post-Treatment Lyme Disease Syndrome (PTLDS), chronic fatigue syndrome, or fibromyalgia after TBRF or BMD is also unknown.
	The serious consequences of co-infection of *B. burgdorferi* and *Babesia microti* have been characterized. There is less information about co-occurrence of active Lyme disease and BMD, which share tick vectors and overlapping distributions, the outcome of the illness, or success of treatment. Acquiring Lyme disease and TBRF at the same time is highly unlikely because of differences in geographic distributions and tick vectors.
	There is no vaccine for either TBRF or BMD and prospects remain poor for the development of one. A *Borrelia* strain can manifest any one of several different antigenic identities when it first infects a mammalian host. Antibodies to one serotype might prevent infection with that particular serotype, but these antibodies would be ineffective against other serotypes. Due to this antigenic variation capability, limited research has investigated potential vaccines.
	Tick control and rodent host management of human habitats and structures infested by soft ticks has relied upon pesticides that are increasingly restricted. There is much less information on the efficaciousness of various pest control measures on soft ticks than on hard ticks.Opportunities

Although not a nationally notifiable condition, prompt reporting of TBRF cases is currently required in many Western states including: Arizona, California, Colorado, Idaho, Montana, North Dakota, Nevada, New Mexico, Oregon, Texas, Utah, and Washington. BMD is not a nationally notifiable disease. Many exposures may occur to out of region vacationers/travelers (locally or globally) who may seek medical care in their home states where these diseases are not endemic. Even within endemic regions, TBRF and BMD exposure risks and identification of disease process may not be recognized by practitioners who are unfamiliar with the diseases either due to a lack of training or experience. Prompt reporting by clinicians was critical to the identification and control of large, multistate outbreaks in recent years.

Without the prospect for a vaccine, reduction of exposure to ticks is a key strategy for preventing TBRF. The risk of TBRF can be reduced by constructing houses with concrete or sealed plank floors and without thatched roofs or mud walls. Log cabins, and similar rustic structures, pose a particular risk because rodents often nest in the roof or beneath the house and porch. Interiors, wall spaces, and attics of buildings infested with soft ticks can be treated with pesticides. As organophosphate use becomes increasingly restricted, less toxic pyrethroid insecticides, such as deltamethrin and cypermethrin, are being used, but there is less experience with these compounds for tick control (Barbour, 2018b). Individuals in high risk environments should move beds away from walls and not sleep on floors. In contrast, prevention of BMD would follow the same measures as those proposed for other hard-bodied tick vectors.

The single most effective measure to reduce the incidence of TBRF and BMD is education - specifically of home/cabin/lodge owners and renters, Airbnb or similar hosts and guests, cave explorers, and others at high risk in endemic areas. Certain activities or circumstances might increase risk. Ranchers, hunters, hikers, military personnel, natural resource managers or others who enter tick habitats could be exposed to soft ticks by working, resting, or camping near infested rodent burrows, caves, or other sites (Gage et al., 2001). Understanding how best to target this messaging, especially with social media, remains to be determined.

Potential Actions for the Working Group to Consider

The subcommittee identified nine potential actions that the federal government could take to reduce TBRF and BMD as a public health threat.

**Potential Action One:** Improve public education on prevention of tick bites. Improve education of health care providers regarding clinical manifestations, diagnosis, treatment, modes of transmission, surveillance reporting, and preventive measures for the unique exposure risks of TBRF and *BMD.*

**Potential Action Two:**Develop point-of-care testing, such as with a nucleic acid amplification test, to support the diagnosis of TBRF and BMD in their symptomatic stages.

**Potential Action Three:**Develop immunodiagnostic assays to discriminate between TBRF*Borrelia* species and *B. miyamotoi.*

**Potential Action Four:**Assess the effectiveness of alternatives to oral doxycycline and parenteral penicillin as treatments of TBRF and BMD, beginning first with *in vitro* testing and then animal models.

**Potential Action Five:**Initiate studies to assess sequela and other post-infection symptomology as a result of either TBRF or BMD.

**Potential Action Six:**Increase resources at the federal and state levels for assessing the incidence of TBRF and BMD.

**Potential Action Seven:**Encourage CSTE to develop case criteria for inclusion of TBRF and BMD in the list of nationally reportable diseases.

**Potential Action Eight:**Investigate whether TBRF or *B. miyamotoi* spirochetes persist as cultivable or uncultivable forms in different tissues, including the brain, and under what conditions, after antibiotic therapy in suitable animal models.

**Potential Action Nine:** Allocate funds to recruit and encourage professionals in the study of soft ticks, TBRF, and BMD.

Vote of Subcommittee Members

Potential actions were presented and discussed by subcommittee members. The wording of potential actions here were voted on by subcommittee members and results are presented here.

**Potential Action One:** Improve public education on prevention of tick bites. Improve education of health care providers regarding clinical manifestations, diagnosis, treatment, modes of transmission, surveillance reporting, and preventive measures for the unique exposure risks of TBRF and *BMD.*

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Two:**Develop point-of-care testing, such as with a nucleic acid amplification test, to support the diagnosis of TBRF and BMD in their symptomatic stages.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent9
			0
			1
			0**Potential Action Three:**Develop immunodiagnostic assays to discriminate between TBRF*Borrelia* species and *B. miyamotoi.*

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Four:**Assess the effectiveness of alternatives to oral doxycycline and parenteral penicillin as treatments of TBRF and BMD, beginning first with *in vitro* testing and then animal models.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Five:**Initiate studies to assess sequela and other post-infection symptomology as a result of either TBRF or BMD.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Six:**Increase resources at the federal and state levels for assessing the incidence of TBRF and BMD.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Seven:**Encourage CSTE to develop case criteria for inclusion of TBRF and BMD in the list of nationally reportable diseases.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent9
			0
			1
			0**Potential Action Eight:**Investigate whether TBRF or *B. miyamotoi* spirochetes persist as cultivable or uncultivable forms in different tissues, including the brain, and under what conditions, after antibiotic therapy in suitable animal models.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Nine:** Allocate funds to recruit and encourage professionals in the study of soft ticks, TBRF, and BMD.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent9
			0
			1
			0References

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Appendix C: Tick-Borne Viruses – Powassan Virus, Heartland Virus, Bourbon Virus, and Colorado Tick Fever Virus

**Lead Authors:**Greg Ebel (ScD) and P. Bryon Backenson (MS)

Executive Summary

Currently, four tick-borne viruses (TBVs) are found in the United States (U.S) and have begun to gain attention as individual cases are reported in the media, creating growing concern about their transmission within minutes of a tick bite. TBVs remain understudied and woefully overlooked by physicians during differential diagnosis due to their rare, and potentially emerging nature, as well as the emphasis on more common tick-borne disease, such as Lyme disease.

These four pathogens—Powassan virus, Heartland virus, Bourbon virus, and Colorado tick fever virus; can all cause death, some with high case-fatality rates. Diagnostic testing is only available at state or federal references laboratories thereby delaying diagnosis and treatment. No curative therapies are known therefore treatment is solely supportive care. Due to the geographic expansion in the range of tick vectors, there is increasing evidence the geographic range of these viruses is also spreading. The cycle of virus transmission, impact of co-infection with other tick-borne pathogens, and the true burden of disease remain to be elucidated.

Background

***Epidemiology****–*All TBVs found in the U.S. are rare. The most common is Powassan virus (POWv) with 30-50 cases reported yearly (Centers for Disease Control and Prevention [CDC], 2019). Approximately 10 cases of Colorado tick fever (CTF) are reported annually (CDC, 2019). About 50 cases of Heartland virus (HRTv) disease have been identified since the pathogen was discovered in patients in 2009 and first reported in 2016 (Centers for Disease Control and Prevention [CDC], 2018b; Esguerra, 2016). Less than 10 cases of Bourbon virus (BRBv) disease have been identified since the pathogen was discovered in 2014 (Kosoy et al., 2015). These numbers likely underreport the true number (incidence) of cases because none of the TBVs are nationally notifiable diseases. Cases have been reported across all age groups and for both sexes. However, due to their rarity and the limited number of reported cases, it remains difficult form a true demographic picture of diseases impact.

TBV diseases all have unique geographical ranges, perhaps dependent on the tick vector. POWv is often found in the same regions as Lyme disease (CDC, 2019). CTF is found in the Rocky Mountains (Centers for Disease Control and Prevention [CDC], 2018a). Until recently, HRTv and BRBv were only found in the Mid-Southern U.S.; however, both viruses were found in ticks in the Northeast U.S. in 2018 and 2019, respectively (P.B. Backenson, personal communication, August 29, 2019).

***Clinical Picture/Syndromic Surveillance****–*Four TBVs represent a significant public health threat in the U.S. POWv, a member of the tick-borne encephalitis (TBEV) group of flaviviruses, is the most notable of the emerging TBV. Currently, TBEVs are causing a major public health issue are responsible for several thousand human cases annually in temperate Eurasia. POWv cases are increasing, often with a high fatality rate (Ebel, 2010). Over the last ten years, the geographic range of the lone star tick, *Amblyomma americanum,*vector has expanded leading to the emergence of new TBVs, including the highly pathogenic HRTv and BRBv (Brault, Savage, Duggal, Eisen & Staples, 2018; Jackson et al., 2019). CTFv, often associated with *Dermacentor* ticks, causes sporadic illness in humans but is consistently present in enzootic areas (Romero & Simonsen, 2008).

*Powassan Virus –* POWv is an emerging tick-borne virus with human cases steadily increasing in the U.S. since the mid-1950s (Hinten et al., 2008)*.*This increase has been steady and gradual. Detection of a small cluster of cases in one particular area in a short time frame, as has recently been seen in both NY and NJ, does not appear to be indicative of a new baseline risk level for subsequent years. Many small case clusters may be ephemeral and factors that cause them to emerge and subside are not well understood.

POWv is transmitted by *Ixodes*species ticks, including *Ixodes scapularis* (deer tick)*and Ixodes cookei,*among small- and medium-sized mammals. The virus is transmitted between life stages in the tick and vertically, from infected females to her offspring (Costero & Grayson, 1996). Virus prevalence in ticks is site-specific. Approximately one to five percent of adult ticks contain viral RNA and/or infectious virus (Anderson & Armstrong, 2012; Brackney, Nofchissey, Fitzpatrick, Brown & Ebel, 2008). POWv can be transmitted by nymphal deer ticks within 15 minutes of attachment to mice (Ebel & Kramer, 2004). Preventing tick bites is essential due to the high likelihood of severe complications from this disease (Birge & Sonnesyn, 2012; Choi & Taylor, 2012; McLean & Donohue, 1959; Raval, Singhal, Guerrero & Alonto, 2012; Tavakoli et al., 2009).

Two Powassan lineages are known: lineage I (prototype POWv) and lineage II (deer tick virus [DTV]) (Ebel, Spielman & Telford, 2001). Most recent POWv encephalitis cases in the U.S have been caused by POWv lineage II, most frequently found in *I. scapularis* ticks. Due to the difficulty in differentiating lineage, the use of POWv in this report refers to both lineages.

As of 2019, cases have been detected in 14 U.S. states – Maine, New Hampshire, Connecticut, Rhode Island, Massachusetts, New York, New Jersey, Pennsylvania, Virginia, North Carolina, Indiana, Wisconsin, Minnesota, and North Dakota; and parts of Canada. Between 2009 and 2018, 75% of the 133 cases were reported in four states - Minnesota (34), Wisconsin (25), Massachusetts (22), and New York (19). POWv infection and disease is likely to continue to occur mainly in these states in the immediate future. The distribution of cases indicates the possibility for expansion with additional hotspots emerging in other states.

Serological studies, of wildlife and virus isolated from ticks, indicates that the distribution of POWv is much broader than the current distribution of human disease (Deardorff et al., 2013). Thomm et al. (2018) reported that in samples collected from Lyme disease endemic regions, POWv seroprevalence in tick-borne disease (TBD) samples was 9.4% (10 of 106) versus 2% in non-TBD samples (2 of 100, P = 0.034); in non-endemic Lyme disease region samples, no POWv seroprevalence was found (0 of 22). Taken together, it is likely exposure is significantly underestimated.

According to the Centers for Disease Control and Prevention (CDC), many people who become infected with POWv do not develop any symptoms (Ebel, 2010). The incubation period from tick bite to the onset of illness ranges from about one week to one month. POWv can infect the central nervous system causing encephalitis and meningitis that leads to symptoms including fever, headache, nausea, vomiting, a stiff neck, weakness, confusion, loss of coordination, speech difficulties, and seizures (Johnson, Staples, Sotir, Warshauer & Davis, 2010; Raval et al., 2012). The majority of symptomatic POWv cases involve an initial febrile illness. During the prodromal phase, sore throat, drowsiness, headache, and disorientation are commonly present (Johnson et al., 2010; Raval et al., 2012). In more severe cases that progress to neurological involvement, the most common clinical presentations of disease are encephalitis (that can be hemorrhagic) with confusion, meningoencephalitis, and aseptic meningitis (Gholam, Puksa & Provias, 1999; Hinten et al., 2008; Tavakoli et al., 2009). The encephalitic phase is characterized by vomiting, prolonged fever, respiratory distress, loss of coordination, difficulty speaking, and seizures. Ocular symptoms, including ophthalmoplegia and direction-changing nystagmus, have been reported in some cases of POWv encephalitis (Trepanier, Loungnarath, Gourdeau, Claessens, & Savard, 2010). Throughout the encephalitic phase, lethargy and some degree of paralysis are typical. Reports of both spastic and flaccid paralyses, as well as coma, have been reported.

A clinically compatible case of POWv neuro-invasive disease, perhaps with a history of tick bite, is defined by the CDC (CSTE 14-ID-04) as – (1) having a fever of greater than 38OC, (2) any signs of peripheral or central nervous system dysfunction documented by a physician, and (3) the absence of a more likely clinical explanation (Centers for Disease Control and Prevention [CDC], 2015). In addition to meeting the clinical disease criteria, one or more of the following laboratory criteria must be met for POWv diagnosis: (1) POWV isolation; (2) detection of specific nucleic acid or viral antigen in blood, CSF (cerebrospinal fluid), tissue, or other body fluids; (3) a four-fold change in POWv-specific quantitative antibody titers in paired serum; (4) POWv-specific IgM antibodies in cerebral spinal fluid (CSF) with a negative result for other IgM antibodies in CSF for arboviruses endemic to the region where exposure occurred; or (5) POWv-specific IgM antibodies in serum with confirmatory POWv-specific neutralizing antibodies in the same or a later specimen (CDC, 2015).

Approximately half of individuals surviving POWv neuro-invasive disease have severe, permanent neurological symptoms such as recurrent headaches, muscle wasting, generalized weakness, and memory or movement problems. Approximately 10% of POWv encephalitis cases are fatal (Ebel, 2010).

*Colorado Tick Fever Virus –*CTF has been known since the late 1800s but received recent attention due to a cluster of human cases occurring in previously atypical locations, including the Pacific Northwest, Arizona, and New Mexico. Transmitted by *Dermacentor* ticks in the Rocky Mountains, CTFv causes a febrile illness in humans similar to other tick-borne disease, such as anaplasmosis and ehrlichiosis, making their diagnoses challenging. If a tick-borne illness cannot be attributed to another agent and antibiotic therapy fails, the clinician should test for CTFv.

*Heartland Virus and Bourbon Virus –*HRTv and BRBv are transmitted by *A. americanum*primarily in Midwestern states. The distribution of *A. americanum* is much broader than that currently of HRTv and BRBv disease. Based on the recent finding of HRTv in ticks on Long Island, New York, these viruses have the potential for to emerge, and cause disease, in wider geographic area.

HRTv was discovered in two Missouri farmers in 2009 (Esguerra, 2016). Approximately 40 cases, primarily in the Central Midwestern states where *A. americanum* is abundant, have been reported since. Cases have also been reported in North Carolina and South Carolina; the virus was recently detected in New York (Brault et al., 2018). Genetically, HRTv shares high sequence identity with the agent responsible for Severe Fever with Thrombocytopenia Syndrome Virus (SFTSV) in Asia. HRTv causes a severe febrile illness accompanied by thrombocytopenia and in most cases leukopenia. The majority of reported cases have required hospitalization and four cases were fatal (Carlson et al., 2018; Fill et al., 2017; Hevey et al., 2019; Muehlenbachs et al., 2014; Pastula et al., 2014). Progression of the disease is characterized by acute renal failure, respiratory failure, and hypotension consistent with sepsis, or uncontrolled systemic inflammation. Other complications have included elevated liver enzymes and ferritin, as well as hemophagocytic lymphohistiocytosis (HLH).

BRBv was first detected in 2014 in a Kansas man, who died from the infection (Kosoy et al., 2015). Only a few additional people are known to have been infected, but at least one other fatal case has been documented (Savage et al., 2017). BRBv causes an illness similar to HRTv, with fever, thrombocytopenia, and leukopenia; though the virus primarily affects liver, lungs, and spleen tissues leading to acute respiratory complications and acute hepatitis. *A. americanum* is thought to transmit the virus to humans, but very few naturally infected ticks have been detected (Savage et al., 2018).

***Laboratory Evaluation****–*No commercially (Food and Drug Administration, 510K cleared) tests are currently available due to the rarity of TBV diseases. Diagnostic testing is available solely at regional, state, or federal reference laboratories. The gold-standard for POWv diagnosis, like other flaviviruses, remains the plaque-reduction neutralization test (PRNT) using appropriately timed, paired acute and convalescent sera. In the Americas, putatively positive POWv samples must also be tested against West Nile Virus to provide specific diagnosis. Detection of CTFv, HRTv, and BRBv is done through serologic testing and PRNT. DNA isolation, PCR, and next generation sequencing are done by regional or state reference labs or the CDC. Newer, more rapid testing techniques still being developed and evaluated.

***Pathology/Pathophysiology****-* POWv neuropathogenesis occurs due to both virus- and immune-mediated damage to neural tissue. Neurons and glial cells are targeted by the virus. POWv encephalitis cases are typically characterized by perivascular and focal parenchymal infiltration, composed largely of lymphocytes and monocytes. Occasional brain necrosis is associated with areas of more intense inflammatory infiltrates. The widespread destruction of neuronal cells has been detected in the large motor neurons of the brainstem, spinal anterior horns, cerebellum, basal ganglia, and thalamus. As with TBEV cases in Europe, magnetic resonance imaging (MRI) abnormalities for POWv cases are nonspecific and not diagnostic. The majority of the reported MRI findings for patients diagnosed with POWv describe T2/fluid-attenuation inversion recovery (FLAIR) hyperintensities within the brainstem, extending to the cortex and deep gray structures (Ebel, 2010; Tavakoli et al., 2009).

***Treatment****-*Patients with severe POWv disease and the other TBVs often need to be hospitalized. Treatment is supportive including respiratory support, intravenous fluids, and medications to reduce swelling in the brain. No effective treatment exists for severe disease; 10-15% of cases are fatal. There are several reports of successful treatment with high-dose corticosteroids used to treat patients with severe, neuro-invasive POWv disease; the potential role of corticosteroids has not been clearly defined. Intravenous immunoglobulin (IVIG) for treatment of POWv encephalitis has also been tried. Both patients treated with IVIG survived the POWv infection; one patient displayed significant neurological sequelae after discharge (Hermance & Thangamani, 2017).

The role of antiviral therapy in treating POWv disease is therefore not clear. Though not yet tested in humans, evidence based on *in vitro* assays and in mouse models suggests the antivirals, ribavirin and favipiravir, which are inhibitors of viral RNA-dependent RNA polymerases, would inhibit replication of BRBv in humans (Bricker et al., 2019). There are no current known antivirals for HRTv or CTFv.

***Evidence for persistent infection/chronic symptomatology/chronic co-infection****–*There have been anecdotal reports and small case series describing coinfection of TBVs with other TBDs (Tokarz, Jain, Bennett, Briese & Lipkin, 2010; Tokarz et al., 2019). These are rarely reported because: (1) the rarity of TBVs in ticks, and (2) the probability that healthcare providers look for other pathogens first. If one or more of those is positive, it is not uncommon for additional testing to be cancelled or not ordered, leaving potential coinfections undiscovered. Developing new tests for TBVs and adding them to TBD testing panels should help address this issue.

To date, there is scant published evidence for pathology resulting from chronic TBV infection.

Gaps in Knowledge and/or Data

There is very limited information on the disease burden and range of clinical presentations of TBVs in the Americas. Neurotropic flaviviruses, such as West Nile Virus, cause a wide array of clinical presentations and even mild acute disease may lead to chronic health problems (Murray et al., 2018; Philpott et al., 2019).
	The number of cases of POWv, TBV, and coinfection may be underreported due to healthcare providers being unaware of their existence, or presence, in their geographic area. Healthcare providers often only test for Lyme disease because it is the tick-borne disease that they are most familiar with.
	POWv is in the process of a “slow” emergence as a significant health threat. The transmission cycles that are driving this process are not fully understood. POWv may be transmitted horizontally by the oral route, but the relative contribution of this mode of transmission compared with others (e.g., vertical, co-feeding, transstadial) of virus perpetuation in nature is understood solely through modeling studies (Nonaka, Ebel & Wearing, 2010). The role of tick phenology differs between the POW-enzootic states of Minnesota and New Jersey. The role of these phenologies in shaping virus transmission patterns is similarly incompletely understood. *I. scapularis* is a significant POWv vector; the vertebrate hosts that contribute most to transmission are unknown.
	POWv infects *I. scapularis* (deer ticks) in sites where they are highly abundant and other tick-borne pathogens, such as *B. burgdorferi* and *B. microti*, are maintained (Ebel, Foppa, Spielman & Telford, 1999; Telford et al., 1997). The degree to which other members of the TDB “guild” that are maintained by deer ticks influence POWv prevalence is not well understood. This could occur either via pathogen manipulation of the host immune response or by competition or synergism within tick vectors. It is increasingly clear that ticks harbor a diverse microbiome that includes several viruses (Cross et al., 2018; Tokarz et al., 2010; Tokarz et al., 2019; Tokarz et al., 2014). The relationship of this microbiome to its pathogenic components remains to be determined.
	No effective treatment exists for severe neurological complications and sequelae. Increasing rates of exposure to POWv in highly Lyme disease endemic areas, with the potential for severe morbidity and mortality, requires more research into antiviral drugs and evaluating vaccines for prevention. TBEV in Europe has an effective vaccine. Due to poor return on investment, vaccine development within the U.S. has stalled.
	As the geographic distributions of the highly aggressive *A. americanum* and *H. longicornis* ticks expand, how will this impact the distribution of known and yet to be discovered TBVs? Rigorous comparative studies, incorporating several tick populations and virus strains, are needed to understand the competency of these ticks as vectors for the transmission of viruses to human. It is also not well understood whether the high abundance of these ticks in new environments may displace more well-established ticks such as *I. scapularis* that currently serves as the vector for lineage II POWv.Opportunities

*Prevention –*The increasing numbers of individuals exposed to POWv in highly endemic areas, combined with the risk of contracting a potentially fatal illness with no cure, increases the opportunity to launch an effective educational campaign. The public needs to understand the necessity of instituting effective tick prevention. The best way to protect against POWv, and other TBDs, is to avoid tick bites. This requires staying out of wooded or grassy areas whenever possible and spraying all areas of bare skin with an insect repellent containing at least 20% DEET or IR3535 or picardin, which repel ticks, keeping in mind that repellants only last for a few hours. Permethrin-treated clothing and gear will also dramatically decrease the risk of a bite.

Once indoors, it is essential to check clothing and pets for ticks. A full body check is also essential, especially in areas that might escape recognition, such as the scalp, behind the knees, axilla (armpit), and groin/perirectal area, for those who have spent time outdoors. Taking a bath or shower to find to wash any ticks off the skin can also be helpful. Placing clothes in a dryer on high heat for 15 minutes will kill ticks.

*Making TBVs Nationally Notifiable –*Given the increasing burden of TBV diseases, POWv, CTFv, HRTv, and BRBv should be made reportable. Some states already report using the catch-all “arborviral diseases”, but these are often commonly thought of as mosquito-borne, rather than including TBVs. Making TBVs reportable by name would increase awareness of them and lead to more accurate recording of disease burden.

*Surveillance –*Starting and/or expanding tick and tick-borne pathogen surveillance at the state and county level is also recommended. CDC recently published a guidance document for tick surveillance and is encouraging states to start tick surveillance, if they haven’t already one, with a goal of understanding more tick species and their distributions and densities in the U.S.

Tick surveillance can be active (going out and collecting ticks in the field) or passive (having individuals send ticks to a tick identification or testing service). The challenge is having surveillance that is comprehensive enough to generate accurate data for the geographic area under study. Optimally, active surveillance collections would be done for all human biting life stages for the species under surveillance. For large states, or if surveillance needs to be performed for many different species (which often require different collection techniques), this can require many dedicated resources. Partnerships with colleges, universities, or veterinary clinics may help in alleviating this resource burden. Since 2009, the New York State Department of Health (NYSDH) has been performing active, statewide, tick surveillance. Aided by local colleges and universities, the limited staff at NYSDH has been able to maintain surveillance for both nymph and adult stages of*I. scapularis* at over 100 sites (P.B. Backenson, personal communication, August 29, 2019). These collaborations allow NYSDH access to specimens from more-difficult to reach areas of the state while the colleges and their students benefit from real-world field experience.

Identifying the tick-borne pathogens and viruses in ticks is perhaps the best opportunity to assess human disease risk, but it is also not without issue. Ticks are usually pooled, due to the relative rarity of these pathogens, and tested to conserve resources. Many laboratories have experience with testing ticks for the bacterial and parasitic pathogens that cause Lyme disease, ehrlichiosis, anaplasmosis, and babesiosis, however, viral testing may require additional training or biosafety precautions. If testing for public health decision making, when and how to release results as well as liability and specimen preservation must be considered. Pathogen testing in ticks does not typically need to meet the stringent requirements that are in place for clinical laboratory testing.

Other methods of surveillance for TBVs may be useful and less resource-intensive. Collecting blood from hunter-killed deer, either at check stations or at deer processors, and performing serologic testing has been helpful in determining whether or not deer have been exposed to various TBVs during their lifetimes (P.B. Backenson, personal communication, August 29, 2019). This can provide a “broad brush” view at whether or not there are ticks carrying various TBVs in an area.

Potential Actions for the Working Group to Consider

The subcommittee identified ten potential actions that the federal government could take to achieve the priority of reducing burden of illness associated with tick-borne viruses in the U.S.

**Potential Action One:** Allocate resources and establish uniform reporting criteria for Colorado Tick fever virus, Heartland virus, and Bourbon virus. Encourage conversations between the Centers for Disease Control and Prevention and CSTE to make all TBVs nationally notifiable.

**Potential Action Two:** Identify and promote simple, rapid, and straightforward viral diagnostics and incorporate them into existing, commercially available, tick-borne disease panels.

**Potential Action Three:** Conduct serological surveys and clinical follow-up to determine the range of clinical presentations and outcomes following TBV infection.

**Potential Action Four:** Increase education to physicians and other healthcare providers on these uncommon diseases that have changing geographic distributions. If healthcare providers do not know about these diseases, they will never consider them in their diagnoses nor order tests for them.

**Potential Action Five:** Conduct research to better understand the relationship between virus perpetuation and human risk. Research efforts should include: long-term field studies of TBVs in relevant field locations as well as the use of existing collections of ticks and vertebrate specimens to determine the distribution of infection in space, in different tick species, and in putative vertebrate hosts.

**Potential Action Six:** Conduct laboratory experiments on virus-vector-vertebrate interactions to clarify molecular interactions that are critical to transmission and to identify weak points in transmission that could serve as targets for novel interventions.

**Potential Action Seven:** Evaluate the potential role of the Asian longhorned tick, *Haemaphysalis longicornis,* in transmission of TBVs including laboratory and field studies to: evaluate host associations, particularly whether it will feed on humans; evaluate potential interactions between this tick species and important native tick vectors; e.g., *Ixodes scapularis* and *Amblyomma americanum*; and determine the potential for significant changes in the risks for different tick-borne diseases.

**Potential Action Eight:** Conduct experiments to determine the potential interactions between tick species where many different species coexist or are expected to coexist in the future. Expected increases or decreases in tick populations or species distributions have significant impacts on risk for different TBVs.

**Potential Action Nine:** Assess the role of multi-pathogen interactions within vectors and vertebrates and their impacts on transmission. These studies should include: defining the tick microbiome giving attention to tick species, location, life-stage, time of year, and infection status for known pathogens. Efforts should also focus on experimental studies to define the extent that pathogenic and apathogenic microbiota impact virus replication and transmission.

**Potential Action Ten:** Develop molecular and entomological tools to analyze vector pathogen interactions, such as antibodies against tick cell markers, and improved reverse genetic systems for tick-borne virus studies *in vivo*.

Votes of Subcommittee Members

Potential actions were presented and discussed by subcommittee members. The wording of potential actions here were voted on by subcommittee members and results are presented here.

**Potential Action One:** Allocate resources and establish uniform reporting criteria for Colorado Tick fever virus, Heartland virus, and Bourbon virus. Encourage conversations between the Centers for Disease Control and Prevention and CSTE to make all TBVs nationally notifiable.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Two:** Identify and promote simple, rapid, and straightforward viral diagnostics and incorporate them into existing, commercially available, tick-borne disease panels.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Three:** Conduct serological surveys and clinical follow-up to determine the range of clinical presentations and outcomes following TBV infection.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Four:** Increase education to physicians and other healthcare providers on these uncommon diseases that have changing geographic distributions. If healthcare providers do not know about these diseases, they will never consider them in their diagnoses nor order tests for them.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Five:** Conduct research to better understand the relationship between virus perpetuation and human risk. Research efforts should include: long-term field studies of TBVs in relevant field locations as well as the use of existing collections of ticks and vertebrate specimens to determine the distribution of infection in space, in different tick species, and in putative vertebrate hosts.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent9
			0
			1
			0**Potential Action Six:** Conduct laboratory experiments on virus-vector-vertebrate interactions to clarify molecular interactions that are critical to transmission and to identify weak points in transmission that could serve as targets for novel interventions.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Seven:** Evaluate the potential role of the Asian longhorned tick, *Haemaphysalis longicornis,* in transmission of TBVs including laboratory and field studies to: evaluate host associations, particularly whether it will feed on humans; evaluate potential interactions between this tick species and important native tick vectors; e.g., *Ixodes scapularis* and *Amblyomma americanum*; and determine the potential for significant changes in the risks for different tick-borne diseases.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Eight:** Conduct experiments to determine the potential interactions between tick species where many different species coexist or are expected to coexist in the future. Expected increases or decreases in tick populations or species distributions have significant impacts on risk for different TBVs.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Nine:** Assess the role of multi-pathogen interactions within vectors and vertebrates and their impacts on transmission. These studies should include: defining the tick microbiome giving attention to tick species, location, life-stage, time of year, and infection status for known pathogens. Efforts should also focus on experimental studies to define the extent that pathogenic and apathogenic microbiota impact virus replication and transmission.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Ten:** Develop molecular and entomological tools to analyze vector pathogen interactions, such as antibodies against tick cell markers, and improved reverse genetic systems for tick-borne virus studies *in vivo*.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0References

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Fill, M.A., Compton, M.L., McDonald, E.C., Moncayo, A.C., Dunn, J.R., Schaffner, W., . . . Shieh, W.J. (2017). Novel clinical and pathologic findings in a Heartland virus-associated death. *Clinical Infectious Diseases, 64*(4), 510-512. doi:10.1093/cid/ciw766.

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Appendix D: Tularemia

**Lead Authors:**Eugene (Gene) David Shapiro (MD) and Sam R. Telford, III (SD, MS)

Executive Summary

Tularemia is a rare bacterial zoonosis caused by *Francisella tularensis*. Approximately 100 to 200 cases are reported each year from the United States (U.S.), most of which were acquired via tick bites (Centers for Disease Control and Prevention [CDC], 2019). Most cases of tularemia are reported from the Southcentral U.S. *F. tularensis*was weaponized by both the U.S. and Soviet Union during the 1950s due to its low infective dose in experimental conditions (with a median infectious dose of less than 10 bacteria), capacity to cause severe disease, and purported environmental stability. Possession and use of *F. tularensis* are highly regulated by the federal government through the Federal Select Agent Program (FSAP). Confirmation testing is standardized and controlled by the Laboratory Response Network (LRN) through state public health departments. All cases must be reported within seven days to the FSAP. Select agent reporting has been routine for over 15 years making surveillance for tularemia excellent. Due to *T. F. tularensis’*association with biodefense and emergency preparedness, healthcare providers have been the focus of education to increase awareness about this pathogen.

Background

***Epidemiology -***Differences in the distribution, ecology, biochemistry, and virulence of the organism led to the seminal classification of tularemia into distinct types (Olsufiev, Emelyanova & Dunayeva, 1959). Type A organisms, now known as *F. tularensis* *tularensis*, are found in North America but not Eurasia, frequently transmitted by ticks, and may cause severe disease. Type B organisms, known as *F. tularensis* *holarctica*, can be isolated from water or soils; causes episodic outbreaks (epizootics) in beavers, muskrats, and arvicoline rodents in both North America and Eurasia; and may cause a milder disease (Jellison, Kohls, Butler & Weaver, 1942). Type B may also be transmitted by ticks.

Francis (1937) noted that over 90% of the more than 6000 tularemia case reports compiled from 1924-1935 were associated with exposure to cottontail rabbits or hares. As a result, this historical association has dominated the views of tularemia epidemiology. In the Southcentral U.S., tick exposure accounted for 70% of all cases during the 1960s (Brooks and Buchanan, 1970). The tick vectors *Dermacentor andersoni*, *Dermacentor variabilis*, and *Amblyomma* *americanum*are the same as those for Rocky Mountain spotted fever (RMSF). While RMSF incidence increased during the 1960s and 1970s, tularemia incidence has decreased over the same time period (Childs & Paddock, 2002; Boyce, 1975).

Tularemia remains a rare disease in the U.S. with a median of 127 cases reported annually from 2001-2010 (Centers for Disease Control and Prevention [CDC], 2013). *F. tularensis* is****highly infectious and may be transmitted mechanically, on the mouthparts of various hematophagous arthropods, by contact with body or tissue fluids through the abraded skin, or by ingestion, in addition to tick transmission. Whether ticks are obligately required for enzootic maintenance remains poorly understood (Telford & Goethert, 2020). A wide range of animals are known to be exposed or infected (Burroughs, Holdenried, Longanecker & Meyer, 1945). Tick surveys of endemic sites have found the prevalence of ticks infected with *F. tularensis* in the range of 0.1-5% (Hopla, 1960; Goethert, Shani & Telford, 2004). In contrast, for deer tick transmitted pathogens, other than *B. burgdorferi*, the prevalence of infected ticks ranges from 5%-15% (Pepin et al., 2012). Given these diverse modes of transmission and wide range in the U.S., it remains to be explained why tularemia is a rare infection (Telford & Goethert, 2011).

***Clinical Picture/Syndromic Surveillance –***Based on the Council of State and Territorial Epidemiologists (CSTE; Centers for Disease Control and Prevention [CDC], 2017) surveillance case definition (CSTE 16-ID-11), the clinical criteria for tularemia is characterized by several distinct forms, including:

Ulceroglandular: cutaneous ulcer with regional lymphadenopathy;
	Glandular: regional lymphadenopathy with no ulcer;
	Oculoglandular: conjunctivitis with preauricular lymphadenopathy;
	Oropharyngeal: stomatitis or pharyngitis or tonsillitis and cervical lymphadenopathy;
	Pneumonic: primary pulmonary disease;
	Typhoidal: febrile illness, occasionally with vomiting and diarrhea, without other localizing signs and symptoms. Depending on the infecting dose, gastrointestinal tularemia ranges from mild but persistent diarrhea to an acute fatal disease with extensive ulceration of the bowel (Ellis, Oyston, Green & Titball, 2002).Clinical diagnosis is supported by evidence or history of a bite from either a tick - the dog tick (*D. variabilis*), the wood tick (*D. andersoni*), the lone star tick (*A. americanum*) can transmit the organism, or a deerfly; exposure to the tissues of or a bite from a mammalian host of*F. tularensis*; or exposure to potentially contaminated water (Jellison, 1974, pp. 18-24). Only ulceroglandular, glandular, and typhoidal forms of tularemia spread through the blood after spillover from the initial sites of replication from an unrecognized tick bite) may be associated with tick bite.

***Laboratory Evaluation****–*Laboratory diagnosis can be broken into two categories – confirmatory or supportive. A confirmatory diagnosis requires one of the following criteria: (1) isolation of *F. tularensis* in a clinical or autopsy specimen, or (2) a fourfold or greater increase in serum antibody titer to *F. tularensis* between acute and convalescent specimens.

Supportive diagnosis requires one of the following criteria: (1) an elevated serum antibody titer(s) to *F. tularensis* antigen without a documented four-fold or greater change in a patient with no history of vaccination against tularemia, (2) detection of *F. tularensis* in a clinical or autopsy specimen by fluorescent assay, or (3) detection of *F. tularensis* in a clinical or autopsy specimen by polymerase chain reaction (PCR). Cases are further classified as probable – a clinically compatible case with supportive laboratory evidence, or confirmed – a clinically compatible case with confirmatory laboratory evidence.

New cases of tularemia can be distinguished from an existing case if there are additional epidemiology compatible exposure or a new onset of symptoms. The duration of antibody persistence is unknown, therefore the presence of antibodies without both a clinically-compatible illness AND an epidemiologically compatible potential exposure within 12 months of onset of the illness may not indicate a new infection, especially among persons who live in endemic areas.

***Pathology/Pathophysiology****–*Following tick exposure, tularemia typically develops within three days with a characteristic sudden onset of onset of chills, fever, sweats, headache, and prostration (Evans, Gregory, Schaffner & McGee, 1985; Matyas, Nieder & Telford, 2007). The incubation period may range from one day to a week. Within 48 hours of onset, regional adenopathy occurs with pain and enlargement of the draining lymph nodes (Evans et al., 1985; Simpson, 1929, pp. 97-108). As the disease progresses, the initial ulcer presented as a papule that becomes a circumscribed ulcer with erythema and a necrotic base (Evans et al., 1985; Simpson, 1929, pp. 97-108).

Tularemia is often perceived as a severe and fatal illness, however, only 5% of cases were fatal in the pre-antibiotic era. Secondary blood-associated transmission may cause severe pleuropneumonia with case fatality rates up to 40% prior to antibiotic treatment. Only one death has been reported out of over 100 cases over 10 years in a longstanding Martha’s Vineyard outbreak of primary pneumonic tularemia (Matyas et al., 2007). Patients may undergo a prolonged convalescence and remain bedridden for 10 days to 3 weeks. Transaminases may remain significantly elevated during this time and there can be extensive liver damage due to massive bacterial replication in the liver. Lymph nodes may be filled with pus many months after the acute phase. Most patients recover with no sequelae (Evans et al., 1985). Partial immunity may be retained, however Edward Francis, who comprehensively characterized the disease, suffered three distinct episodes of tularemia.

The differential diagnosis is extensive. Many different illnesses present with fever, regional lymphadenopathy, pneumonia, and/or fever including bacterial lymphadenitis, cat-scratch disease, toxoplasmosis, and numerous viral infections (Fredrichs & Remington, 1996). Given the non-specific nature of symptoms it is important to get a full patient history including potential exposure to the pathogen.

Diagnosis can be difficult to confirm. Bacteremia, when it occurs, is often transient and of low level, but can be identified by standard blood culture methods. Transient bacteremia leads to poor sensitivity of nucleic acid tests (NAT) of blood samples during the acute phase.

For tick-transmitted infection, bacteria can usually be detected by culture, agglutination and microagglutination tests, fluorescent antibody, or PCR assay on aspirate samples from skin lesions or an enlarged lymph node. Standard agglutination and microagglutination tests do not detect antibody until 10 days or more after illness presentation. In many cases, an antibody response is not detectible until two or more weeks after initial presentation. There is some evidence that an enzyme immunoassay (EIA) that uses the *F. tularensis* lipopolysaccharide may become positive for antibody 2 or more days earlier than the microagglutination test (Elliasson et al., 2008).

The standard microagglutination test is simple and has excellent sensitivity and specificity for convalescent serum samples. Most laboratories concurrently perform agglutination/microagglutination with *Brucella* antigens, however, false positives may be due to cross-reactivity with *Brucella* species. (Lindquist, Chu & Probert, 2007, pp815-834). Once in limited supply, the availability of *F. tularensis*antigen for these diagnostics has stabilized due to the commercial use of the non-restricted, attenuated, live vaccine strain (LVS).

***Treatment****–*Streptomycin or gentamicin (aminoglycosides) are the antibiotics of choice for the treatment of tularemia (Enderlin, Morales, Jacobs & Cross, 1994). Ciprofloxacin has been successfully used to treat uncomplicated tularemia, and may be more effective than the aminoglycosides, but a formal clinical trial is needed to assess its efficacy (Meric et al., 2008).

Doxycycline, the antibiotic of choice for the treatment of numerous tick-borne infections including Lyme disease and ehrlichiosis, is effective against *F. tularensis* and may prevent serious complications.

***Evidence for persistent infections/chronic symptomatology/chronic co-infection***–******Tularemia is marked by a prolonged convalescence due to extensive necrosis in the liver, spleen, and lungs, where masses of bacteria accumulate in untreated disease (Simpson, 1929, pp. 97-108). Complications are more frequent in those who do not seek prompt medical attention (Penn & Kinasewitz, 1987). Tick transmitted tularemia caused by *F. tularensis holarctica* (Type B) are often undiagnosed due to a mild and self-limiting fever and adenopathy (Schmid et al., 1983).

Comorbidities are likely to influence the severity of disease but there is no evidence coinfections impact the course of the illness. There is rare published evidence for persistent infection or chronic disease, although lymph nodes may remain pus-filled for weeks after acute disease (Horowitz & Freeman, 2016; Olsufjev, Shlygina & Ananova, 1984; Shygina, Ananova & Olsufjev, 1989).

Gaps in Knowledge and/or Data

The main gaps in knowledge for tularemia relate to treatment options and the natural history of *F. tularensis*.

Aminoglycosides effectively treat tularemia but require parenteral administration. Doxycycline can be sufficient to treat tularemia in younger, healthy individuals, but infection may recur. Ciprofloxacin can be effective but has not been assessed in a clinical trial because there are few endemic sites with enough cases to conduct an adequately powered clinical trial. Moxifloxacin has been used effectively in combination therapy with doxycycline, rifampin, and dapsone in an immunosuppressed patient with tularemia but further studies are necessary to evaluate efficacy (Horowitz and Freeman, 2016). Understanding the clinical effectiveness of these agents and how effective dosing may reduce the prolonged convalescence after tularemia are important knowledge gaps.
	All aspects of tularemia research are burdened by restrictions of the FSAP that legally impacts all potential research studies to expand our knowledge of this illness. Understanding the why human risk of tularemia is focally distributed remains unclear and would aide in evaluation of possible future outbreaks.Opportunities

Preventing tick bites reduces the risk of acquiring tick-transmitted tularemia. An attenuated vaccine (LVS) has been used by the U.S. military since the 1960s and effectively reduces disease risk for laboratory researchers. Clinical trials to determine whether vaccination with LVS prevents tick-transmitted tularemia have not been done. LVS may have public health utility if vaccination is warranted based on environmental risk(s), however, there is no obvious financial return on the investment needed to complete required clinical testing for Food and Drug Administration (FDA) approval. There is some perception that “new and better” vaccines are needed based on biodefense considerations, to better protect against inhalational tularemia, and because the basis of attenuation of the LVS, and potential reversion to wildtype, is not well understood.

Potential Actions for the Working Group to Consider

The subcommittee identified four potential actions that the federal government could take to reducing the risk of tularemia as a public health threat in the U.S.

**Potential Action One:**Enhance education for healthcare providers to aid in appropriate diagnosis of potential tick-borne tularemia cases. This education would include epidemiology, natural history, signs and symptoms, preferred specimens and volumes for collection, and shipping requirements.

**Potential Action Two:**Improve prevention education targeting high risk groups (e.g., hunters, anglers, ranchers, landscaping workers), especially in regions where transmission is known to occur.

**Potential Action Three:**Include tularemia testing in multiplex systems that are used for testing field collected ticks as a part of a national tick surveillance system to provide better information on pathogen occurrence and distribution.

**Potential Action Four:**Mitigate the administrative and legal effects of the Select Agent Rule to facilitate research on tularemia.

Vote of Subcommittee Members

Potential actions were presented and discussed by subcommittee members. The wording of potential actions here were voted on by subcommittee members and results are presented here.

**Potential Action One:**Enhance education for healthcare providers to aid in appropriate diagnosis of potential tick-borne tularemia cases. This education would include epidemiology, natural history, signs and symptoms, preferred specimens and volumes for collection, and shipping requirements.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Two:**Improve prevention education targeting high risk groups (e.g., hunters, anglers, ranchers, landscaping workers), especially in regions where transmission is known to occur.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent10
			0
			0
			0**Potential Action Three:**Include tularemia testing in multiplex systems that are used for testing field collected ticks as a part of a national tick surveillance system to provide better information on pathogen occurrence and distribution.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent9
			0
			1
			0**Potential Action Four:**Mitigate the administrative and legal effects of the Select Agent Rule to facilitate research on tularemia.

Number in Favor
			Number Opposed
			Number Abstained
			Number Absent9
			0
			1
			0References

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