Updated May 2018


Lyme disease in humans is caused by three species of Borrelia bacteria. In North America, Lyme disease is caused primarily by Borrelia burgdorferi, while in Europe the disease is caused mainly by B. garnii and B. afzelli. In Ontario, transmission occurs through the bite of infected blacklegged ticks called Ixodes Scapularis or deer ticks. The risk for exposure to the disease is highest in regions where the ticks that transmit Lyme disease bacteria are known to be established. Blacklegged ticks are found in Toronto with Rouge Valley, Morningside Park, Highland Creek and Algonquin Island being established areas of risk. However, the risk of acquiring Lyme disease in Toronto is believed to be low.

Lyme disease prophylaxis and diagnosis algorithm for clinicians

Signs and symptoms usually occur one to two weeks after a tick bite, but can begin as early as three days to as long as four weeks after a tick bite.

Lyme borreliosis is generally divided into three stages in which infected persons may experience any of the following symptoms:

Early localized disease

  • Erythema migrans (EM) or “bull’s eye” rash (see below) at the site of a recent tick bite
  • Fever
  • Malaise
  • Headache
  • Myalgia
  • Neck stiffness
  • Fatigue
  • Arthralgia

Early disseminated disease

  • Multiple EM in approximately 15% of people occurs several weeks after infective tick bite
  • Cranial nerve palsies
  • Lymphocytic meningitis
  • Conjunctivitis
  • Arthralgia
  • Myalgia
  • Headache
  • Fatigue
  • Carditis

Late disease

May develop in people with early infection that was undetected or not adequately treated. May involve the following:

  • Heart
  • Nervous system and joints
  • Arrhythmias, heart block and sometimes myopericarditis
  • Recurrent arthritis affecting large joints (i.e., knees)
  • Peripheral neuropathy
  • Central nervous system manifestations – meningitis; encephalopathy (i.e., behavior changes, sleep disturbance, headaches)
  • Fatigue
2 examples of bull's eye rashes.
Lyme Disease Erythema Migrans


Erythema migrans represents a response to the bacterium as it spreads intradermally from the site of the tick bite. Characteristics include:

  • Develops in about 70-80% of infected persons.
  • Occurs within three to 30 days (average seven days) at the bite site; can persist for up to eight weeks.
  • The rash gradually expands and can reach up to 12 inches across its largest diameter. As it expands, area of the rash may clear resulting in a “bull’s-eye” appearance.
  • Rash is rarely itchy or painful; usually feels warm to the touch.


Note: An erythematous skin lesion that presents while a tick is still attached or which develops within 48 hours of detachment is most likely a hypersensitivity rather than EM. Tick bite hypersensitivity is typically less than five cm in largest diameter, has urticarial appearance and begins to disappear within 24 – 48 hours. There is usually little pain, swelling, itchiness, scaling, exudation or crusting, erosion or ulceration. Inflammation at the centre of the lesion may or may not be present.

In Ontario, blacklegged ticks are the only type of tick that transmits the bacteria that causes Lyme disease. The risk of human infection increases with the time a tick is attached to a person and usually requires the tick to be attached for 24 hours or more.

Ticks can attach to any part of the human body but, if found, may be in hard-to-see areas such as the armpits, groin and scalp. Most humans are infected through the bites of immature ticks called nymphs, which are tiny (less than two mm) and difficult to see. Adult ticks can also transmit Lyme disease bacteria, but they are larger (five mm) and therefore more likely to be discovered and removed before they have had time to transmit the bacteria. Early detection and removal of ticks is important in the prevention of Lyme disease.

For information about where ticks can be found within the City of Toronto, see Toronto Public Health’s Blacklegged Tick Surveillance.

Tick Surveillance outside of Toronto

For information on Lyme disease risk locations in Ontario, see Public Health Ontario Lyme Disease Risk Areas Map

Public Health Agency of Canada surveillance has identified that Lyme disease is present or establishing in other parts of Canada. For more specific Lyme disease risk locations, consult the Public Health Agency of Canada website .

Tick Surveillance outside of Canada

In the United States, blacklegged ticks infected with Borrelia are concentrated heavily along the Atlantic seaboard (from Maine to Virginia), and in the upper Midwest (Minnesota and Wisconsin).

Worldwide, the disease is also known in China, Japan and Russia. Lyme disease is the most common vector borne disease in Europe with the highest incidence in the Baltic States and Sweden in the north, and in Austria, the Czech Republic, Germany, Slovenia and central Europe.

Human Surveillance

In Toronto, within the last five years, an average of 39 persons with Lyme disease infection were reported to Toronto Public Health. Most of these cases acquired the disease outside of the City of Toronto. For more information, see Public Heath Ontario’s Surveillance Reports page.

Knowledge of a patient’s exposure to Lyme disease risk areas is an important parameter for Lyme disease diagnosis. However, tick populations continue to expand and it is possible that Lyme disease can be acquired outside the currently identified areas. In addition, ticks can travel or migrate on the bodies of animals such as birds, and therefore can be sporadically present in very low numbers over an even broader area

Diagnosis, particularly the early stage, is based primarily on clinical symptoms and epidemiological risk factors. Public Health Ontario Laboratory has information on General Test Requisition (PDF).

Blood sample should be collected in a red-top tube and sent to Public Health Ontario Laboratory which performs a two-step testing protocol for Lyme disease (see below) to detect antibodies against B. burgdorferi. The first step involves testing using a screening Enzyme Immunoassay (EIA) test. If initial EIA result is non-reactive, healthcare providers should consider an alternative diagnosis; or in cases where the patient has had symptoms for <= 30 days, the provider may treat the patient and follow up with a convalescent serum. If the EIA result is reactive or indeterminate, a confirmatory test using Western Immunoblot assay is performed.

Blood tests may be negative in patients with early stage Lyme disease or in patients previously treated with antibiotics. The accuracy of blood tests increases as the infection progresses, although it is recognized that a small proportion of patients with later-stage Lyme disease may test negative. The stage of infection and the possible impact of treatment on the outcomes of blood testing should be taken into consideration during diagnosis.

If a patient was exposed to other species of Borrelia such as those that occur in Europe, provide travel history and request testing for European Lyme disease. The specimens from these patients are sent to the National Microbiology Laboratory for antibody testing.

Public Health Ontario Laboratories


Enzyme Immunoassay (EIA): If non-reactive, "no serological evidence of infection", consider alternative diagnosis or obtain convalescent serum if patient has signs/symptoms consistent with Lyme Disease. If re reactive or indeterminate, requires Western Immunoblot testing Igm and IgG. If the results are reactive/indeterminate, the results should be interpreted in the context of clinical signs and symptoms. If the Western Immnubolot testing is non-reactive, the results should also be interpreted in the context of clinics signs and symptoms.
Lyme Disease 2 step protocol

Blood sample should be collected in a red-top tube and sent to Public Health Ontario Laboratory (PHOL), which performs a two-step testing protocol to detect antibodies against B. burgdorferi. If patient was exposed to other species of Borrelia such as those that occur in Europe, provide travel history and request testing for European Lyme disease.


Indication and Limitation to tests

  • Initial negative serological tests in patients with EM should have testing repeated after four weeks.
  • Sera that screen negative using EIA will not be sent for further testing using Western blot.
  • Patients that are treated early in the course of the illness may not develop antibodies to the Lyme disease agent and may therefore have a non reactive test.
  • EIA test lacks the specificity necessary to base a diagnosis of Lyme disease on an unconfirmed result, therefore confirmation must be done using the Western blot.
  • Results should be interpreted in the context of clinical signs and symptoms and exposure history.

For information on preventing Lyme disease, please visit Toronto Public Health’s Environmental Health Lyme disease prevention page.

If you find a tick on your body, remove it with fine-tipped tweezers. Do not squeeze or try to burn it off. Grab the tick as close to your skin as possible. Pull the tick away from your skin gently but firmly.


Pulling a tick out of the skin, using tweezers. Pulling directly up at a 90 degree angle.
Removing a tick

Toronto Public Health staff can provide identification of ticks brought into our offices from these locations:

  • 44 Victoria Street, 18th Floor, phone number 416-392-7685
  • 1530 Markham Road, 5th Floor, phone number 416-338-7431
  • 5100 Yonge Street, 2nd Floor, phone number 416-338-8410
  • 399 The West Mall, 4th Floor, phone number 416-338-1507
  • 175 Memorial Park Avenue, phone number 416-392-0936

The tick will be submitted to the Public Health laboratory for identification. If the tick is identified as a blacklegged tick, it is forwarded to the National Microbiology Laboratory in Winnipeg to test for Borrelia burgdorferi, the bacteria that causes Lyme disease, as well as other tick-borne pathogens including Anaplasma phagocytophilum and Babesia microti. Test results can take several weeks to months.

Submitting ticks is for surveillance purposes and should not be used as a way to determine if a person needs treatment for Lyme disease.

Ticks not found on a person will not be accepted by the public health lab. Ticks found on a pet can be submitted to the Animal Health Laboratory through a veterinarian to the University of Guelph.

Please note: Tick submissions will no longer be accepted from parts of Toronto (Rouge Valley, Morningside Park, Highland Creek, and Algonquin Island) or from health units in Ontario (Eastern Ontario; Haldimand-Norfolk; Kingston-Frontenac; Lennox & Addington; Leeds-Grenville & Lanark District) where black-legged tick populations are known to be established.

Tick Submission

Ticks must be collected in a clean transparent container.  Name of the patient and date of birth must be marked on the container. A sterile urine collection container may be used for this purpose.

For Health Professionals

Parasitology Laboratory, Public Health Ontario (PHO)
MaRS 2 Tower (south side)
661 University Avenue
Toronto, Ontario M5G 1M1
    • To assist with Toronto Public Health’s passive surveillance activities, please remember to fax the submission form to 416-392-0714, attention Vector Borne Disease Manager or call Toronto Public Health for tick submission assistance at 416-338-7600

For the general public

Prompt removal of attached ticks is important to prevent Lyme disease.

A single 200 mg dose of oral doxycycline may be offered to adult patients and to children 8 years of age and older, when all of the following conditions are met:

  1. Adult or nymph of I. scapularis tick was attached for more than 24 hours; AND
  2. Prophylaxis can be started within 72 hours from the time that the tick was removed: AND
  3. Person was exposed in an area where ecologic information indicates that the rate of infection of ticks is >20%. Currently in Toronto, this includes Rouge Park, Morningside Park; and Highland CreekAND
  4. Doxycycline treatment is not contraindicated

Doxycycline is relatively contraindicated for pregnant and breast-feeding women and for children less than 8 years. In these cases, the patient and their provider should make an informed choice between a single dose of doxycycline and no prophylaxis.

There is effective antibiotic treatment for early localized Lyme disease. Should prophylaxis not be indicated based on the above criteria, the health care provider should watch for signs and symptoms of Lyme disease and treat early. (See below.)


1. Early Lyme Disease: These cases refer to patients with symptoms including a Bull’s Eye Rash (see above), fever, and/or arthritis and minimal or no comorbidities. These cases can be managed according to the table below.

Management Recommendations for Basic Lyme Disease in Patients without Significant Comorbidities

Medication Adult Dose and Duration Pediatric Dose and Duration

  • preferred primary treatment
  • not recommended for pregnant women
100 mg po bid for 14 days
  • Not recommended for children under 8.
  • Over 8 years: 4 mg/kg/day divided bid to max 100mg/dose
Amoxicillin 500 mg po tid for 14 days 50 mg/kg/day divided tid to max 500 mg/dose
Cefuroxime axetil 500 mg po bid for 14 days 30 mg/kg/day divided bid to max 500 mg/dose

2. More complex cases: These include late Lyme disease, Lyme disease with neurological complications, or Lyme disease in pregnant women and patients with significant comorbidities. These cases require more thorough consideration for treatment and in some cases, with expert consultation.

For more information on the prevention and treatment of Lyme disease see the full guidelines developed by the Infectious Diseases Society of America (2006)

Post-treatment Lyme Disease Syndrome (PTLDS)

Approximately 10-20% of patients may experience persistent or recurrent symptoms following appropriate antibiotic treatment, and are considered to have Post-treatment Lyme Disease Syndrome.