Important Change to Passive Tick Surveillance in Ontario
Advisory Alert
September 23, 2020
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To: Community health providers
As of September 20, 2021, the National Microbiology Laboratory (NML) will no longer test blacklegged ticks (BLT) collected through passive surveillance. Individual tick pathogen testing will no longer be available. This is a change from the previous practice, where all BLTs are submitted for testing. Public Health Ontario (PHO) will continue to accept tick submissions and provide identification results to various submitters, but this can take weeks to process. An alternative for clinicians is www.etick.ca, an online image-based tick identification platform, which may produce faster results.
The diagnosis of Lyme disease is mainly clinical, supported by a possible history of tick exposure. It is important to remember that tick identification and pathogen testing of ticks as part of Ontario’s surveillance system were not specifically designed to aid clinicians in managing tick bites. Individual tick pathogen testing results may cause unintended harm to the patient due to:
- Reliance on individual tick results may be misleading as a person may have been bitten by another tick which they did not find or submit for subsequent testing.
- Misinterpretation of results (an infected tick does not always mean that the infection was transmitted during a bite) can hinder treatment.
- Delays in appropriate treatment. Patients with clear symptoms of Lyme disease should be diagnosed clinically and treated without laboratory confirmation. Similarly, post-exposure prophylaxis should be considered if criteria is met. Please refer to Ontario Health (Health Quality Ontario) clinical guidance document for managing patients following a tick bite.
Please note that despite these changes, monitoring of tick populations in Ontario remains an important part of public health activities. Active surveillance efforts, which involve ‘dragging’ for ticks in specific areas to determine if pathogen carrying ticks are present, will continue. Ticks found during active surveillance practices will be submitted to the NML for identification and pathogen testing.
Further information about Lyme disease can be found on PHO’s Lyme disease resource page, the Ontario Ministry of Health’s Lyme disease website, and by visiting www.phsd.ca or by calling Public Health Sudbury & Districts at 705.522.9200 (toll-free 1.866.522.9200).
Sincerely,
Original Signed By
Dr. Penny Sutcliffe
Medical Officer of Health and Chief Executive Officer
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This item was last modified on September 24, 2021