The Public Health Agency of Canada (PHAC) in partnership with provincial and territorial public health authorities, conducts surveillance for Lyme disease in Canada. Our studies show the risk of the disease is growing in this country. Risk is emerging in parts of Manitoba, Ontario, Quebec, New Brunswick, Nova Scotia and has been present in southern British Columbia for several years, due to spread of populations of the ticks that carry the bacterium that causes Lyme disease.
Lyme disease is an illness caused by the bacterium Borrelia burgdorferi, which can be spread through the bite of certain types of ticks. Lyme disease in humans can have serious symptoms but can be effectively treated. Lyme disease is the most common vector-borne disease in the temperate zone and occurs in Europe, Asia, and throughout much of North America.
Ticks live in and around wooded areas and they get infected when they feed on mice, squirrels, birds and other small animals that can carry the bacterium. Ticks then spread the bacterium to humans. Tick bites are usually painless and most people do not know that they have been bitten. Two types of ticks are responsible for the spread of Lyme disease in Canada: the western blacklegged tick in British Columbia and the blacklegged tick in other parts of Canada. People can’t spread Lyme disease to each other. Although dogs and cats can contract Lyme disease, there is no evidence that they can spread the infection directly to people. Pets can, however, carry infected ticks into homes and yards. Hunters may be at greater risk of contracting Lyme disease because they spend more time in habitats where ticks tend to live. However, Lyme disease cannot be spread by butchering or eating deer meat or organs.
The Agency encourages people to spend time outdoors, be active and to remember to protect themselves against tick bites and Lyme disease with the following measures:
If a blacklegged tick bite occurs:
Blacklegged ticks are primarily found in densely wooded areas and the unmaintained transitional edge habitat between woodlands and open areas. Fewer ticks are found in ornamental vegetation and lawn areas. Within the lawn, most of the ticks are located within 3 metres of the lawn perimeter particularly along woodlands, stonewalls, or ornamental plantings.
Precautions to reduce tick habitat near your residence:
For more information on integrated tick management please see:
Tick Management Handbook, 2007 Kirby Stafford. (PDF document)
Ticks are small biting arachnids (related to scorpions, spiders and mites) that feed on blood. Ticks vary in size and colour; blacklegged ticks are very small. Before feeding, adult females are approximately 3-5 mm in length and red and dark brown in colour. Ticks feed on blood by attaching to animals including people with their mouth parts. Females are a little larger than males and when they’re full of blood, they can be as big as a grape. Males never expand in size because they do not engorge on blood. Larvae and nymphs (the juvenile life stages) are smaller still and, when unfed, are lighter in colour than adult ticks. People and pets can pick up ticks by brushing against vegetation like grass, shrubs and leaf litter.
Figure 1: This figure shows the size and colour of female blacklegged ticks in various stages of feeding by using a photograph of five female ticks superimposed on a plastic ruler and next to which a 10-cent coin has been placed. The photograph shows that unfed female ticks are a dark reddish brown colour, they become paler brown to yellow as they start to feed, then they become greyish as they continue to feed and are dark grey-brown when fully fed. As the ticks feed, the abdomen of the tick enlarges so the tick increases in size from approximately 0.3 cm when unfed to 0.6 cm when partially engorged. When fully fed, the tick is approximately 1cm long and egg shaped.
Figure 2: This figure shows the size and colour of nymphs of the blacklegged tick in various stages of feeding by using a photograph of three nymphs superimposed on a plastic ruler and next to which a 10-cent coin has been placed. The photograph shows that unfed nymphal ticks are very small (0.15 cm long) and grey-brown in colour. As they engorge, their abdomen enlarges and darkens. When fully fed, the engorged nymph is approximately 0.3 cm long, almost black in colour and egg shaped.
There are areas in Canada where tick populations that transmit the agent of Lyme disease are established and these are known as Lyme disease endemic areas. Though western blacklegged ticks, Ixodes pacificus (sometimes called the deer tick), are widely distributed in British Columbia, populations are largest in the lower mainland, on Vancouver Island and in the Fraser Valley. Established populations of blacklegged ticks, Ixodes scapularis (sometimes called the deer tick), on the other hand, have been found in southeastern Manitoba, southern and eastern Ontario, southeastern Quebec and parts of New Brunswick and Nova Scotia.
Blacklegged ticks can be found in many parts of Canada, even where tick populations have not been identified. These ticks are likely introduced into these areas by migratory birds and about 10 per cent of these “bird-borne” ticks are infected with the Lyme disease bacterium. So, while it is possible to be bitten by an infected tick almost anywhere in Canada, the chances of this happening in places where tick populations are not established are very low.
For more information on blacklegged ticks, please view the Agency’s website on Lyme disease and other tick-borne disease.
The symptoms of Lyme disease usually happen in three stages, although not all patients have every symptom. The first sign of infection is usually an expanding rash called erythema migrans or EM. This rash occurs in about 70-80 per cent of infected people. It often begins at the site of the tick bite after a delay of three days to one month and can persist for up to eight weeks. Typical signs of skin irritation such as itchiness, scaling, pain, swelling, or exudation are not normally associated with EM. Other common symptoms include:
If untreated, the second stage of the disease, known as disseminated Lyme disease, can last up to several months and the symptoms include:
If the disease remains untreated, the third stage can last months to years with symptoms that can include recurring arthritis and neurological problems.
Fatalities from Lyme disease are very rare.
For more information on the clinical symptoms of Lyme disease, please see - Lyme disease, A zoonotic disease of increasing importance to Canadians. Canadian Family Physician 2008
Lyme disease can usually be treated effectively with antibiotics. The sooner treatments start, the better. Most cases of Lyme disease can be cured with a two to four week treatment of doxycycline, amoxicillin, or ceftriaxone. People with certain neurological or cardiac problems may require intravenous treatment with penicillin or ceftriaxone. Patients diagnosed in the later stages of the disease can have persistent or recurrent symptoms requiring a longer course, up to eight weeks maximum, of antibiotic treatment.
In 2009, Lyme disease became a nationally reportable disease in Canada. This means that all healthcare professionals should report cases of Lyme disease to the Public Health Agency of Canada via their provincial public health system. Recent studies suggest that the incidence of Lyme disease in Canada is increasing.
The risk for exposure to the disease is highest in regions where the ticks that transmit Lyme disease are known to be established. These regions are parts of southeastern Manitoba, southern and eastern Ontario, southern and southeastern Quebec, New Brunswick and Nova Scotia as well as much of southern British Columbia. Surveillance data indicates a small number of blacklegged ticks are introduced into widely separated areas of Canada by migratory birds, posing some risk that individuals in other areas may also be exposed to infected ticks.
Some Lyme disease symptoms are similar to symptoms of other illnesses, so diagnosing it correctly usually involves:
Blood tests may be negative in patients with early Lyme disease or in patients who have had antibiotic treatment. This should be taken into consideration during diagnosis. However, the accuracy of blood tests becomes more reliable as the infection progresses. All laboratory tests have a margin of error, which is why Lyme disease should be diagnosed by a doctor’s assessment of symptoms first and foremost. Laboratory testing can be used as supportive evidence.
The National Microbiology Laboratory (NML), and some provincial laboratories assist clinicians to diagnose Lyme disease using a two-tiered testing method which includes an ELISA screening test followed by a confirmatory Western blot test. ELISA stands for enzyme-linked immunosorbent assay, which is a blood test that detects the presence of antibodies to Borrelia burgdorferi, the bacterium that causes Lyme disease. The Western blot also identifies Lyme disease antibodies and can confirm the results of an ELISA test. The NML uses the two-tiered testing method because together the two tests offer more accurate results.
Yes, according to the Public Health Agency of Canada, the United States Centers for Disease Control and European Public Health organizations, the two-tiered method is the best laboratory method currently available for supplementing clinical information on Lyme disease. The two-tiered test starts with a screening ELISA test. Any samples that test positive or where the results are uncertain, are confirmed using a Western blot test. This two-tiered approach to blood testing for Lyme disease is based on the best available scientific evidence.
Like other infectious diseases where two-tiered testing is used (for example, HIV infections), screening tests followed by confirmatory tests provide the greatest level of true positives while minimizing the number of false negatives. Simply put, the two-tiered approach provides the most accurate information about infection compared to either test conducted alone. However, all laboratory tests have a margin of error, which is why the Agency recommends that Lyme disease be diagnosed first and foremost on the basis of a doctor’s assessment of symptoms, especially in early infection.
Blood tests may be negative in patients with early Lyme disease (for example when a rash is present) or in patients who have had antibiotic treatment. The accuracy of blood tests increases as the infection progresses, although it is recognized that a very 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.
It is important to remember that all laboratory tests have a margin of error and no test is perfect. Lab tests, including those for Lyme disease, are routinely subject to internal and external quality control processes to ensure results are specific and accurate.
Please click here for more information on diagnosis and reporting.
For more information about the diagnosis of Lyme disease, please see: Ogden N et al. The emergence of Lyme disease in Canada. CMAJ 2009;180(12):1221-1224
Ticks found on a person’s skin can be submitted for identification and possible testing as part of the tick surveillance program coordinated by the Public Health Agency of Canada. When possible, ticks should be sent to provincial collaborators for identification who then forward only the blacklegged ticks to the Agency's National Microbiology Laboratory (NML). Staff at the NML will conduct diagnostic testing for the Lyme disease bacterium as well as several other disease-causing agents. For information on where to send tick specimens in your area, contact the NML through phone or email at:
National Microbiology Laboratory
Phone: (204) 789-2000
Canadian laboratory diagnostic guidelines for Lyme disease are consistent with those followed by public health authorities in the United States and Europe and meet international standards. Public health professionals in these countries have concerns regarding reports of some laboratories that may not be using properly validated tests or criteria for interpreting test results. Diagnostic methods used by these and Canadian laboratories produce a similar number of positive results, indicating that patients have been exposed to Lyme disease bacteria. However, the methods used by some laboratories may detect more “false positives” in people who are actually not infected with Lyme disease. As a result, patients who don’t have Lyme disease may end up receiving potentially harmful treatments.
Although timely treatment with a recommended two- to four-week course of antibiotics is effective to treat Lyme disease in most cases, approximately 10 to 20 per cent of patients have lingering symptoms of fatigue, pain, or joint and muscle aches. In some cases, these can last for more than six months. The clinical term for this condition is "Post-treatment Lyme Disease Syndrome" (PTLDS). The exact cause of PTLDS is not yet known. Most medical experts believe that the lingering symptoms are the result of residual damage to tissues and the immune system that occurred during the infection.
Regardless of the cause of PTLDS, studies have not shown that patients treated with prolonged courses of antibiotics do better in the long run than patients treated with placebo. Furthermore, long-term antibiotic treatment for Lyme disease has been associated with serious complications such as antimicrobial resistance, tender and swollen extremities, and low number of white blood cells. It can take several months for patients with PTLDS to feel completely well.
The Agency recognizes that chronic illnesses are a significant health burden in Canada, and supports, in principle, any efforts to ensure that affected patients receive prompt and effective diagnosis and treatment.
Yes, blacklegged ticks can spread other diseases. For example, some blacklegged ticks carry the bacterium Borrelia miyamotoi, which can cause a flu-like illness in people. This bacterium has only recently been discovered in blacklegged ticks from the U.S. and Canada. Although some cases of illness have been identified in the northern U.S., the risk to Canadians is low. Blacklegged ticks live in limited areas of Canada and the number of ticks that carry B. miyamotoi is much lower than the number that carry the Lyme disease bacteria. Similar precautions to avoid Lyme disease should be taken to protect against Borrelia miyamotoi. Infections are also treatable with antibiotics.
Blacklegged ticks can also carry the parasite Babesia microti, which can cause human babesiosis, as well as Powassan encephalitis virus, a rare cause of encephalitis in people. Other bacteria carried by these ticks include Borrelia bissettii, Borrelia carolinensis and Borrelia kurtenbachii; although whether these bacterium cause disease in humans in North America is unknown.
Along with its international partners, the Public Health Agency continues to investigate the diversity of bacteria carried by these ticks and test for infections.
For more information, please see: Investigation of Genotypes of Borrelia burgdorferi in Ixodes scapularis: Ticks collected during surveillance in Canada, Applied and Environmental Microbiology, 2011 May; 77(10): 3244–3254.
There is no evidence that Lyme disease can be directly transmitted from person to person through sexual or other common forms of human contact (such as kissing or coughing near someone).
Presently, there isn’t a licensed test for screening blood donors for Lyme disease. Although there is a theoretical risk, infection in humans has never been linked to a blood transfusion. Lyme bacteria are detectable in the blood of infected people for only a brief period of time, usually while they are symptomatic, and, therefore, those people are not eligible to donate blood. Also, donors being treated for Lyme disease should not donate blood until they are well finished their treatment.
The Public Health Agency of Canada is committed to working with provincial health authorities and other partners to address the risks to Canadians posed by Lyme disease through a number of activities: