Inside look at Lyme disease in Canada


A recent study examines the epidemiology and clinical manifestations of Lyme disease cases in Canada. The study included 4,701 individuals residing in seven provinces in Canada. Participants had been diagnosed with Lyme disease (LD) between 2009-2019. The median age was 53 years and nearly 57% were male.

Murison and colleagues discuss the findings in their report “Epidemiology and clinical manifestations of reported Lyme disease cases: Data from the Canadian Lyme disease enhanced surveillance system.”¹

“The results from this analysis describe the clinical manifestations associated with Canadian [Lyme disease] cases from the LDES system and show trends of LD diagnosis in several Canadian provinces over time,” states Murison.

Common manifestations

A single EM rash was the most common manifestation (76%) reported by Lyme disease patients.

Lyme arthritis was the second most reported manifestation (32%).

Cardiac complications were higher in specific age groups including those 25–39, 60–64 and 70–74. However, “Similar to reports in the United States, fatal cardiac manifestations are rare,” the authors state.

Interestingly, “There was a significant decrease in the proportion of late disseminated [Lyme disease] cases reported after 2016.”

Investigators suggest this may be due to improvements in identification and treatment of Lyme disease.

Cases of late disseminated Lyme disease appeared more often in the Central region.

Lyme disease manifestations by age

Single and multiple EM rashes were more frequently seen in children between the ages of 5-9 and in adults between ages 55-79 and 60-79, respectively.

The incidence of Bell’s palsy peaked in children ages 5-14 and in adults between 60-64.

Lyme arthritis was most often seen in children ages 5-14 and in adults between 60-74.

Meanwhile, other neurological manifestations peaked in children aged 10–14 and in adults aged 55–74.

“Cardiac symptoms were more evenly distributed across age groups, with lower incidence in children and spikes in incidence in adults aged 25–39, 60–64 and 70–74,” the authors state.

Geographic distribution and changes in manifestations over time

The majority of cases reported in New Brunswick (67%) and Nova Scotia (63%) included patients who exhibited signs of early localized Lyme disease.

However, Ontario reported more cases of late disseminated Lyme disease.

Reports of other neurological manifestations increased from 15% (2009–2015) to 20% (2016–2019).

Meanwhile, reports of Lyme arthritis decreased from 36% in 2009–2015 to 31% in 2016–2019.

  1. Murison K, Wilson CH, Clow KM, Gasmi S, Hatchette TF, Bourgeois AC, Evans GA, Koffi JK. Epidemiology and clinical manifestations of reported Lyme disease cases: Data from the Canadian Lyme disease enhanced surveillance system. PLoS One. 2023 Dec 15;18(12):e0295909. doi: 10.1371/journal.pone.0295909. PMID: 38100405; PMCID: PMC10723709.

2 Replies to "Inside look at Lyme disease in Canada"

  • Rob Murray
    02/16/2024 (2:36 pm)

    In Canada, officials only count the cases they are absolutely sure of. All you really know is the absolute minimum number of cases. There is consensus that cases are under-detected but not consensus on what multiplier to use. You can safely multiply whatever number they report by 10 and still be under estimating the true number. The estimated under-detection ranges from 12.1 to 58.2-fold [1.7% to 8.3%] under-detection. Lloyd/Hawkins 2018. Journalists unfailingly report only the official numbers posted by PHAC website and fail to note any limitations or discrepancies which PHAC fails to disclose. Canada doesn’t have a second source of data similar to that of the U.S. insurance industry that showed there are at least half a million new cases a year not the 50,000 officially reported.

    The CDC in a recent report made incremental changes but are still reliant on the flawed serology that got us into all this trouble. Currently there is no test that can rule out Lyme disease. The original problem was that they defined the test too narrowly by a flawed test that misses at least a third of those that are truly positive in Canada. The worst thing you can do for a patient is give them a false negative test result. The test for Lyme is based on the original strain of Borrelia found on the Eastern U.S. Seaboard. Strains vary across Canada while new ones are still being discovered. The test doesn’t detect Borrelia miyamotoi which is found in all provinces. Physicians haven’t been told that the test and guidelines they used are flawed and should be scrapped.

    IDSA/ AMMI Definition: “Lyme borreliosis is caused by the spirochete Borrelia burgdorferi [strain B- 31] and is transmitted by deer ticks [Ixodes scapularis].”

    CanLyme definition: “Lyme disease is a tick-borne zoonosis caused by several genospecies of the spirochete Borrelia burgdorferi sensu lato.” [In the broad

    More important, one shouldn’t “define” a disease in terms of a single bacterial species, let alone a single strain of that species. One should acknowledge the well-known diversity of agents [in this case a spirochete] that causes a disease.

    “It’s like defining a dog bite as that of a German shepherd when you have been bitten by a pit bull”. They are choosing to define the disease by the diagnostic. That’s what they can detect, so that’s what they consider the disease. This makes no sense but politics rarely does. We have different strains of the bacteria across Canada and the test won’t detect all of them. AMMI [Canada] have moved serology to the top of the hierarchy when this is a clinical disease and tests were only meant to help the physician confirm the diagnoses.

    Many physicians will mistakenly defer to the PHAC case definition of Lyme disease in making a diagnosis. These clinicians require that patients meet these strict and narrow criteria in order to be diagnosed with the disease. However, this definition was designed as a surveillance-monitoring tool to track the number of Lyme disease cases throughout the country. It was not meant to be used in making a clinical diagnosis. Still, even when patients meet the PHAC criteria, there can be a delay in diagnosis; a delay that can have long-lasting consequences for the patient.

    Rob Murray [DDS retired]
    Board member Canadian Lyme Disease Foundation []

  • Bonnie Weaver
    02/12/2024 (6:52 pm)

    I got Lyme Disease after I was bitten by a tick in France. My rash was not the typical one for Canada and the nearby USA. It was an oval expanding rash. I got neurological Lyme. No arthritic pain. I delayed treatment because I didn’t recognize my rash as a Lyme Disease rash. I did not have any treatment in time so I have been on antibiotics to keep the Lyme under control for several years now.

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