For health professionals: Lyme disease

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What health professionals need to know about Lyme disease

Lyme disease is a serious illness caused by the bacterium Borrelia burgdorferi. The bacterium is a spirochete transmitted by certain species of Ixodes ticks. It is spread through the bite of infected blacklegged ticks and western blacklegged ticks.

Health professionals are encouraged to further their knowledge of Lyme disease in Canada. This includes the ability to:

  • understand and identify the signs and symptoms
  • prescribe appropriate treatment for patients diagnosed with the disease
  • report human cases through appropriate channels

Consult the national case definition for additional information.

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Clinical manifestations

Symptoms sometimes appear in overlapping stages, as:

  • early localized Lyme disease
  • early disseminated Lyme disease
  • late disseminated Lyme disease

It is important to note that some people with Lyme disease may have no or minimal symptoms. Others may suffer more severe symptoms.

Some people may not develop symptoms until weeks after the initial bite, as described in the early localized disease stage below. In this case, they may not remember the tick bite or associate the illness with the bite. Because the blacklegged tick is so small and usually painless, some people may not even know they were bitten by a tick.

Health professionals should be knowledgeable about the clinical manifestations and epidemiological risk factors of Lyme disease. Consider Lyme disease as part of your differential diagnosis in a patient who presents with compatible symptoms and signs.

Accurate diagnosis and immediate treatment are key factors to the successful management of Lyme disease.

Early localized Lyme disease (less than 30 days)

Early localized Lyme disease usually presents as an acute illness characterized by:

  • fever
  • arthralgias
  • myalgias
  • headache
  • the presence of a single, localized skin lesion known as erythema migrans (EM)

Not all patients will present with an EM. Therefore, diagnosis should not be based solely on the presence of EM.

Most patients will present with EMs within 7 days of the initial tick bite. However, the incubation period can vary between 3 and 30 days.

The skin lesion is characteristically an annular erythematous lesion greater than 5 cm in diameter that:

  • slowly increases in size
  • is usually painless and non-pruritic

The lesion sometimes develops central clearing, but it can be more homogenously erythematous. In dark-skinned patients, the rash may appear more as a bruise.

Variations of an EM are highly suggestive of Lyme disease and can take the following forms:

  • blistering
  • solid lesions
  • crusted lesions
  • blue-purple hues
  • a bull's-eye appearance
Image of erythema migrans or EM that has developed into a Bull's eye at the site of a tick bite. It is shown here on this woman's upper arm.

A skin lesion called erythema migrans can develop into a bull's-eye at the site of a tick bite. It is shown here on a patient's upper arm.Footnote 1 

A typical sign of early non-disseminated Lyme disease is an expanding rash called erythema migrans. This can take on the appearance of a bull's eye.

A typical sign of early non-disseminated Lyme disease is an expanding rash called erythema migrans. This can take on the appearance of a bull's eye.Footnote 1 

Some Lyme disease skin lesions are uniformly red and do not appear with the classic ring.

Some Lyme disease skin lesions are uniformly red and do not appear with the classic ring.Footnote 1  

Some patients present with a central blistering lesion, commonly mistaken as a spider bite. This is likely due to an inflammatory reaction to the pathogen induced by the tick.Footnote 1 

Some skin lessions caused by lyme diseases have a blue-purple colour. They are distinct from bruises as the perfectly uniform circle has a sharply demarcated border.

Some skin lesions caused by Lyme diseases have a blue-purple colour. They are distinct from bruises as the perfectly uniform circle has a sharply demarcated border.Footnote 1  

Lyme disease is spread through the blood to other areas of the body. Therefore, a bite may lead to multiple skin lessions,taking variable shapes.

Lyme disease is spread through the blood to other areas of the body. Therefore, a bite may lead to multiple skin lesions, taking variable shapes.Footnote 1  

Some people may have minor symptoms. Therefore, it is best not to make a diagnosis based solely on the presence or absence of a bull's-eye rash. Consider other signs and symptoms as part of your differential diagnosis of the disease, including:

  • fatigue
  • arthralgia
  • headache
  • low-grade fever

Early disseminated Lyme disease (less than 3 months)

If untreated, the bacterium causing Lyme disease can:

  • disseminate via the bloodstream to other body sites
  • provoke damage to body tissues at those sites

Symptoms can include:

  • fatigue and general weakness
  • cutaneous signs (for example, multiple EM lesions)
  • cardiac manifestations are:
    • atrioventricular block
    • tachyarrhythmias
    • myopericarditis
    • myocardial dysfunction
  • neurological symptoms, such as:
    • aseptic meningitis
    • radiculopathy
    • encephalopathy
    • cranial neuropathy (especially facial nerve palsy)
    • mononeuritis multiplex
    • subtle cognitive difficulties
    • motor and sensory radiculoneuropathy
  • other rare manifestations, such as:
    • uveitis
    • keratitis
    • conjunctivitis
    • mild hepatitis
    • splenomegaly

Late Lyme disease (more than 3 months)

If it remains untreated, late Lyme disease can last months or even years.

Symptoms could be musculoskeletal, such as in the form of:

  • Baker's cyst
  • chronic arthritis
  • asymetric oligoarticular arthritis (usually affects the knees)
  • transient, migratory arthritis and effusion in 1 or multiple joints

If untreated, arthritis may recur in the same or different joints.

Symptoms can also be neurological, such as:

  • subacute mild encephalopathy, affecting:
    • memory
    • concentration
  • chronic mild axonal polyneuropathy, manifested as:
    • distal paresthesias
    • radicular pain (less common)
  • encephalomyelitis (rare)
  • leukoencephalopathy (rare)

Symptomatic infection of the heart is rare in Lyme disease cases. However, 3 sudden cardiac deaths associated with Lyme carditis were reported in the U.S. between 2012 and 2013.

Post-treatment symptoms

Some people who were treated for Lyme disease continue to have symptoms months to years after treatment.

This condition is known as post-treatment Lyme disease syndrome (PTLDS). Its symptoms should be managed and treated appropriately.


The diagnosis of Lyme disease is primarily clinical, supported by a history of possible tick exposure.

Not all patients will develop noticeable symptoms. As such, it is important to:

An additional diagnostic tool is the detection of antibodies using the two-tiered serological method described below.

However, patients with clear symptoms of early localized Lyme disease should be diagnosed and treated without laboratory confirmation. This is because false negative results are possible during the early stage of Lyme disease.

Laboratory testing

Laboratory testing should only be used to supplement clinical findings, not as a basis for diagnosis of early Lyme disease.

Two-tiered serological testing

The two-tiered serological testing approach is recommended when testing a patient's blood for antibodies against the bacterium causing Lyme disease. This approach is validated for use in Canada and includes:

  • an enzyme immunoassay (EIA) screening test
  • a confirmatory immunoblot (IB) test (if the EIA is positive or equivocal)

Interpretative criteria for the EIA and IB assays have been standardized and summaries of the diagnostic approaches for Lyme disease are available.Footnote 2 Footnote 3  If testing is required, indicate the presumed exposure area (for example, North America or Europe) on the requisition. The location will determine which tests will be used, as tests vary depending on the species of Borrelia.

In suspected Lyme meningitis, testing by an accredited laboratory for intrathecal IgG or IgM antibodies may be helpful.

All diagnostic laboratories across Canada have systems in place that are recognized by accreditation bodies, such as:

  • Ontario Laboratory Accreditation
  • the College of American Pathologists
  • the International Organization for Standardization

This applies to all procedures conducted in the laboratory, including those specifically for Lyme disease serological testing.

These laboratories are required to:

  • participate in external proficiency testing to ensure high-quality results
  • be licenced by the federal government to conduct serological tests for Lyme disease

Canadian laboratory diagnostic guidelines for Lyme disease meet current international standards. They are also consistent with those followed by public health authorities in the U.S. and Europe. Public health professionals in these countries have concerns that some private, for-profit laboratories may not be using:

  • properly validated tests
  • recommended standards for interpreting test results

Notes on serological tests

For patients with illness lasting over a month, only IgG testing should be performed (not IgM). A positive IgM test alone is not sufficient to diagnose current disease in these patients.

Due to antibody persistence, a positive serological test cannot distinguish between active and past infection.

Serological tests:

  • should not be done as a test of cure
  • cannot be used to measure treatment response

The EIA test:

  • has low specificity
  • may yield false-positive results when used as a stand-alone test
  • may cross-react with antibodies to commensal or pathogenic spirochetes
    • there may be some viral infections (for example, varicella and Epstein-Barr virus) for certain autoimmune diseases (for example, lupus)


The treatment regimens listed in the chart below are guidelines for localized (early) Lyme disease. The regimens may need to be adjusted depending on a patient's:

  • age
  • allergies
  • medical history
  • pregnancy status
  • underlying health conditions

Consult an infectious disease specialist for the most current treatment guidelines or individual patient treatment decisions.

Treatment guidelines for localized (early) Lyme disease
Age category Drug Dosage Maximum Duration in days (range)
Adults Doxycycline 100 mg, p.o., q 12 h N/A 14 (14 to 21)
Cefuroxime axetil 500 mg, p.o., q 12 h N/A 14 (14 to 21)
Amoxicillin 500 mg, p.o., q 8 h N/A 14 (14 to 21)
Children Amoxicillin 50 mg/kg per day p.o., divided in 3 doses 500 mg per dose 14 (14 to 21)
Doxycycline 4 mg/kg per day p.o., divided into 2 doses 100 mg per dose 14 (14 to 21)
Cefuroxime axetil 30 mg/kg per day p.o., divided into 2 doses 500 mg per dose 14 (14 to 21)

Important treatment considerations

Doxycycline is contraindicated and amoxicillin is the drug of choice for:

  • children younger than 8 years of age
  • women who are pregnant or lactating

In addition, some patients may be unable to tolerate the drugs listed in the chart. In this case:

  • a macrolide from the following list can be used, although it will have lower efficacy
    • azithromycin
    • erythromycin
    • clarithromycin
  • patients who are treated with a macrolide should be closely monitored to ensure their symptoms are resolved

Large population studies of pregnant women with Lyme disease who received treatment have shown no increased risk of adverse outcomes.

Some experts recommend offering doxycycline as a single dose of 200 mg for people weighing less than 45 kg. An alternative is to offer doxycycline in multiple doses of 4 mg/kg, to a maximum dose of 200 mg. This is for people 8 years of age or older who have been bitten in an area with hyper endemic infection.

There is no data on the use of amoxicillin as an alternate prophylactic antibiotic in younger children.

Persistent symptoms following treatment

In most cases, timely treatment according to the appropriate regimen described in the chart above is effective. However, some Lyme disease patients have persistent symptoms following treatment. Research continues into the causes and methods of treatment.

There is no definitive evidence that persistent symptoms represent ongoing infection. Post-infectious inflammation due to damage from the infectious process may respond to anti-inflammatory drugs.


Prophylaxis treatment can be started if the patient meets all of the following 4 criteria.

  1. The tick can be reliably identified as a blacklegged tick and is estimated to have been attached for more than 36 hours.
    • This is based on the degree of engorgement or by certainty of when the individual was bitten.
  2. Prophylaxis will be started within 72 hours after the feeding tick has been removed.
  3. The local rate of Borrelia burgdorferi infection in ticks is more than 20% (check with local public health).
  4. Doxycycline is not contraindicated.

If all of the above criteria are met, a single dose of 200 mg of doxycycline may be given to:

  • adults
  • children older than 8 years of age

It should be given at 4.0 mg/kg for patients under 45 kg, up to a maximum dose of 200 mg.

Doxycycline is not recommended for children younger than 8 years of age or for pregnant women.


There is currently no human vaccine for Lyme disease. The best way to avoid the disease is to protect against tick bites. Advise your patients to use preventive measures.

Lyme disease surveillance in Canada

Lyme disease became a national notifiable disease in December 2009.

Canada continues to monitor the evolving geographic distribution and prevalence of infected ticks and cases of Lyme disease. Therefore, you must report clinically diagnosed or laboratory-confirmed cases to your provincial or territorial public health authorities.

Health professionals in Canada play a critical role in identifying and reporting cases of Lyme disease. See the surveillance section for more information on surveillance in Canada.

Consult the national case definition for additional information.

Removing and submitting ticks for testing

  • identify a tick
  • remove a tick from the body
  • submit a tick for identification and possible testing

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