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PLENARY SESSION II: DIAGNOSIS AND LABORATORY TESTING
PLENARY SESSION III:
PLENARY SESSION IV: HUMAN EPIDEMIOLGY AND SURVEILLANCE
PLENARY SESSION V: INFORMATION AND COMMUNICATION
BREAKOUT SESSION REPORTS
BREAKOUT SESSION 1
BREAKOUT SESSION II
PLENARY SESSION VII: NEXT STEPS
Public Health Agency of Canada
Canadian Lyme Disease Foundation
British Columbia Centre for Disease Control
University of Iowa and Connecticut
Nova Scotia Department of Health
Public Health Agency of Canada
Canadian Lyme Disease Foundation
British Columbia Centre for Disease Control
Nova Scotia Department of Health
The Public Health Agency of Canada is grateful to all contributors to the meeting on Lyme disease who provided perspectives representing the findings and concerns of national and international experts, public health professionals, the Canadian Lyme Disease Foundation and the National ME/FM Action Network. The Agency also wishes to express its gratitude to the Planning Committee for their support in organizing the meeting and in the development of the agenda, and to the Canadian Lyme Disease Foundation for identifying a speaker for each session. We would also like to thank all these partners, including the Review Committee, for their continued support in completing this report. Finally, we wish to acknowledge the administrative staff who worked diligently to ensure the success of the meeting and the completion of this report, and facilitation team for their valuable help in keeping discussion focused.
In Canada, diseases transmissible between animals and humans, or zoonotic diseases, represent an increasingly important public health threat and are caused by a wide-range of pathogens including bacterial, viral, fungal, rickettsial, chlamydial, prion and parasitic agents. Zoonotic diseases infect farmed, companion and wild animals as well as humans, and include many agents that are recognized as emerging threats. Lyme disease is a tick transmitted zoonotic disease of bacterial etiology which is currently of growing concern in Canada.
There are many factors, including environmental and climatic changes, changes in human behaviour and travel, urbanization, ecological changes and others, that affect the level of risk associated with zoonotic and vector-borne diseases such as Lyme disease. The documentation of newly identified populations of blacklegged ticks infected with Borrelia burgdorferi, the bacteria which causes Lyme disease, in some areas of Manitoba, Ontario and Nova Scotia indicates the need for a broader, systematic approach to tick and human case surveillance, in order to better assess the risk of human infection. Improved understanding of risk would be a driver to developing new approaches in the control, prevention and investigation of Lyme disease in Canada.
On March 8-9th, 2006, the Public Health Agency of Canada sponsored a meeting of national and international scientific experts on Lyme disease, communication experts, provincial representatives, representatives from the Canadian Lyme Disease Foundation and the National ME/FM Action Network. The intent of the meeting was to begin a process to review and update the guidelines from the 1991 consensus conference on Lyme disease. To facilitate this process the meeting reviewed current knowledge on the epidemiology and diagnosis of Lyme disease, and took the opportunity to identify and prioritise research requirements. Consideration was also given to new approaches to surveillance and risk communication of Lyme disease in Canada. The discussion groups, plenary presentations and question and answer periods provided an opportunity to review current guidelines on the epidemiology, diagnosis and treatment of Lyme disease which are based on recommendations from the January 15-16, 1991 Consensus Conference on Lyme disease.
The two-day meeting included presentations which addressed epidemiological, ecological, diagnostic, public health, communications and ethics perspectives and identified significant research findings and issues relating to Lyme disease in Canada and the United States. The plenary sessions provided updates and current information on the epizootiology, diagnosis and laboratory testing, human epidemiology and surveillance, and information and communication of Lyme disease issues.
The tick vector of B. burgdorferi in eastern and central Canada, Ixodes scapularis, has steadily expanded its range in the United States over the last 30 years, and similar range expansions have been observed in parts of southern Manitoba, eastern Ontario, and Nova Scotia in recent years. The need for systematic sampling for ticks together with ecological risk modelling was identified as key to developing predictive risk maps.
The role of migrating passerine birds in transporting vector ticks (I. pacificus and I. scapularis) was demonstrated to be one important mechanism for range expansion, and could help to explain the occurrence of human Lyme disease cases in parts of Canada where the vector ticks are not known to be established. The major bird migration routes transect Lyme disease endemic areas of the United States and Canada. Spring migrating birds stop-over to feed at times that coincide with the seasonal activity of immature stages of I. pacificus and I. scapularis. This has potential to impact the future range of ticks as well as areas of risk of human infection in Canada.
Ongoing expansion of Lyme disease in Canada, however, will be dependent on numerous factors including climate, available habitat, and distribution of potential host species. Current modelling suggests that increased ambient temperatures with climate change could result in expansion of tick range to encompass most of the heavily populated regions of southeastern Canada.
Currently, Lyme disease testing in Canadian Laboratories is based on a two-tiered approach, utilizing an ELISA as a front-line test. Reactors are further examined using IgG and, or IgM western blot tests. This approach is the same as that adopted by the US CDC as the most likely to give the best combination of sensitivity and specificity. However, it was clear in discussions that there were concerns that current testing procedures could miss some patients with Lyme disease. It was acknowledged by all that issues such as the testing approach, stage of disease, the time between tick bite and test, persistence of antibody responses, interpretation of western blot tests, impact of early treatment, and the technical demands of the western blot test can affect test outcomes and that newer and developing test procedures should be evaluated.
While early stage Lyme disease may be characterized by erythma migrans (EM), which is sufficiently distinctive to permit clinical diagnosis by an experienced clinician, acute disseminated disease is characterized by a number of systemic presentations affecting multiple organ systems. Late infection appears to be more specifically associated with neurologic disease and arthritis.
Concern was expressed about suggested links between Lyme disease and Multiple Sclerosis, Chronic Fatigue Syndrome and Fibromyalgia, and the existence of post Lyme disease syndrome, described by some as chronic Lyme disease. Differences were apparent in attendees concerning the existence and definition of what is described as chronic Lyme disease. Part of the problem is the variety of non-specific symptoms associated with the latter, and it was suggested that while it is difficult to relate these symptoms to Lyme disease, the possibility should be further explored.
The number of reported cases of Lyme disease in Canada is relatively low (20-60 new cases reported annually), with over half associated with travel outside of the country. The actual number of cases is undoubtedly higher given that not all clinical cases are captured by current surveillance approaches and there are indications that the incidence of the disease may be increasing. The recent inclusion of Lyme disease as a nationally notifiable disease may help address these issues over time. The use of definitions specifically for surveillance may also help improve ascertainment of case numbers in Canada.
The breakout sessions, which covered the areas of epizootiology, laboratory diagnosis, and human surveillance, provided an opportunity for more in-depth discussions which, in turn, provided recommendations for the revision of the 1991 guidelines and the 1999 national notifiable disease case definition for Lyme disease. Specific comments and recommendations are outlined in the report and will be used as a starting point for revision of the 1991 guidelines.
Discussions in the breakout groups reached consensus on a series of recommendations related to the epizootiology of vector ticks, the definitions (criteria) of tick status in a geographic area, and current distribution of vector ticks in Canada, including the potential role of bird-borne ticks in the future range expansion of tick populations. Consensus was not reached on a number of issues or statements related to the clinical and laboratory diagnosis of Lyme disease due either to disagreement between discussants or because some of the issues identified for discussion were not covered due to lack of time. Some areas of concern could be addressed through clear communication and understanding of the different objectives of a surveillance case definition versus a clinical case definition, as well as improved description of clinical presentations of Lyme disease. There was consensus in plenary session about the need to establish technical working groups to specifically address the more complex and contentious issues by thorough appraisal of available scientific literature.
Positive steps were taken to recommend changes to the wording of the existing (1991) guidelines to update statements related to evidence of infection, and the use of specific diagnostic tests. In particular, it was re-emphasised that lack of evidence of a visit to an area where Lyme disease is established should not influence a clinical consideration of Lyme disease diagnosis in individual patients. Recommendations from the conference should be fully considered in future revisions of a case definition relevant to EM in an individual in a risk area and EM in an individual not in a risk area.
The final plenary session was a discussion on the compiled research needs identified throughout the two days of deliberations and included recommendations covering three key areas: the organism, B. burgdorferi, which causes Lyme disease; the disease itself; and the epidemiology of vector ticks. The genetic diversity and pathogenesis of B. burgdorferi were identified as current priorities for research. Focus on the disease itself should include improvement in diagnostic technologies and approaches, improvement in understanding the clinical presentations and the burden of disease; and improvement in physician awareness of, and knowledge about, Lyme disease.
There was also consensus among participants on critical key issues and recommended next steps which included the following:
Lyme disease poses unique challenges in a changing environment in which further expansion of tick-infested areas and increased risk of human infection are likely to occur. In light of these challenges, the Public Health Agency of Canada will continue to work collaboratively to monitor these risks, enhance diagnostic approaches and provide public health advice, including revision of the 1991 guidelines, based on the best available scientific evidence. Until new guidelines have been approved through the Public Health Network Council, the information in this report may be useful to public health officers and healthcare professionals for consideration in diagnosing, confirming, and reporting cases of Lyme disease in Canada.
The Public Health Agency of Canada brought together scientific experts, external stakeholders and other affected jurisdictions to present their own or their organizational perspectives on areas that need to be considered in the control, prevention, and management of Lyme disease in Canada. The report is a compilation of these perspectives and recommendations and unless otherwise stated does not necessarily represent a consensus of all participants.
This report has been divided into two main sections. The first consolidates all plenary presentations and includes the text of the brief Questions and Answers which followed each plenary session. Section two represents the summaries of the breakout groups, each of which presented comments based on specific tasks or questions and included recommendations and discussions on next steps or revisions to the text of the existing guidelines. The report concludes with a brief presentation of next steps and a summary of the proceedings.
The planning committee for the meeting recognized that addressing Lyme disease epidemiology and diagnosis would raise many issues which would challenge the existing guidelines as well as the views of experts and advocacy groups. To help the decision-making process, the committee requested the facilitator to present a decision-making framework to be agreed at the commencement of the meeting. The framework agreed upon at the meeting was based on definitions of different levels of decisions and is outlined below: