The Public Health Agency of Canada (PHAC) conducts surveillance for Lyme disease in Canada and studies show the risk of the disease is growing in this country. According to recent research, published in April 2010, the risk is emerging in parts of southern Quebec due to newly found populations of ticks that carry the bacterium that causes Lyme disease. Similar changes in the distribution of Lyme disease-carrying ticks have been reported in Manitoba, Ontario, New Brunswick and Nova Scotia in recent years.
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: 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, because they spend more time in habitats where ticks tend to live. However, Lyme disease cannot be contracted from butchering or eating deer meat or organs.
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 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 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 until 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 Quebec, southern and eastern Ontario, southeastern Manitoba 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 a circular rash called erythema migrans or EM. This rash occurs in about 70-80 per cent of infected people. It 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 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
Some Lyme disease symptoms are similar to symptoms of other illnesses, so diagnosing it correctly usually involves three things:
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 clinically first and foremost. Laboratory testing can be used as supportive evidence.
The National Microbiology Laboratory (NML) diagnoses Lyme disease using a two-tiered testing method which includes an ELISA screening test followed by a confirmatory Western blot test. The NML uses the two-tiered testing method because together the two tests offer more accurate results.
Yes, the two-tiered method is the best laboratory method currently available for supplementing clinical information on Lyme disease. Two-tiered test involves: a screening ELISA test and any samples that test positive or inconclusive are confirmed using a Western blot test. This two-tiered approach to blood testing for Lyme disease is the gold standard recommended by US and Canadian public health organizations. It is based on the best available scientific evidence.
Like other infectious diseases where two-tiered testing is used (e.g., 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 PHAC recommends that Lyme disease be diagnosed first and foremost on the basis of clinical symptoms.
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 recognised 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.
Lyme disease has been a nationally notifiable disease in Canada since 2009.
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
Feeding ticks found on a patient’s skin can be submitted to the National Microbiology Laboratory for identification and testing for B burgdorferi infection. For additional information, contact the 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 ongoing concerns regarding American for-profit laboratories that may not be using properly validated tests or criteria for interpreting test results. By using these unvalidated methods, patients who don’t have Lyme disease may test positive and they may end up receiving potentially harmful treatments.
Several antibiotics can treat the illness. The sooner treatments starts, the better. Most cases of Lyme disease can be cured with a 2-4 week treatment of doxycycline, amoxicillin, or ceftriaxone. People with certain neurological or cardiac problems may require intravenous treatment with penicillin or ceftriaxone. Cephalexin is not effective. Patients diagnosed in the later stages of the disease can have persistent or recurrent symptoms requiring a longer course of antibiotic treatment.
The mainstream medical community doubts the existence of a condition known as “chronic Lyme disease” that is responsive to long term antibiotic treatments. However, a condition known as Post-Lyme Disease Syndrome does affect some patients following treatment. Please visit the National Institute of Allergy and Infectious Diseases website for more information.
Small rodents are the most common reservoirs of B. burgdorferi, while larger animals serve as hosts for ticks. Ticks that transmit Lyme disease thrive in wooded areas and can lurk on the tips of grasses or shrubs where they can easily transfer to people or animals as they brush past. In areas where ticks are found, people should know about the risk of Lyme disease and protect themselves. Find out from the local public health office if there are ticks, especially blacklegged ticks, in the area. Most cases of human illness occur in the late spring and summer when the tiny nymphs are most active and human outdoor activity is greatest. The risk of contact with ticks begins in early spring when the weather warms up and lasts until permanent snow cover and sub-zero temperatures persist. The timing and intensity of these events varies across Canada and thus so does the risk period for exposure to ticks. Ticks may be active in the winter months in provinces with mild seasonal temperatures (4°C and above) and infrequent snow cover.
Personal precautions to avoid infection:
The 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)
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. The Agency posts information on reportable, or notifiable, diseases on its website. The Agency also surveys the provinces and territories to assess the number of cases and distribution of Lyme disease in Canada. This survey does not capture all of the cases of Lyme disease in Canada, particularly cases of early Lyme disease. 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 southern and southeastern Quebec, southern and eastern Ontario, southeastern Manitoba, 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.
Although rarer than Lyme disease, there are other infections that can also be contracted from blacklegged ticks. These include Anaplasma phagocytophilum, the agent of human granulocytic anaplasmosis; Babesia microti, the agent of human babesiosis and Powassan encephalitis virus. Most of the precautions outlined above will also help to protect individuals from these infections.
Please click here for more information on diagnosis and reporting.
Public Health Agency of Canada scientists continue to collaborate in studying the occurrence of tick populations in Canada. These studies show there is low risk of encountering ticks infected with the Lyme disease agent in most of Canada although the number of risk areas is increasing in eastern Canada. Many of these findings have been published and reported at scientific meetings to help increase awareness of the potential for Lyme disease to occur in Canada.
In addition, Public Health Agency of Canada scientists are currently researching the potential impacts of climate change on the distribution of the ticks that carry Lyme disease. This research will contribute to our understanding of the occurrence of the ticks and the disease-causing agents they transmit.
The Canadian Institutes of Health Research is currently funding a health research project on Lyme disease. Funding of $820,000 over five years has been provided to study the properties of the bacteria. This health research project will lead to further understanding of the pathogen causing Lyme disease.