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Lyme disease is a serious illness spread by the bite of certain species of ticks. Ticks are small insect-like parasites that feed on the blood of animals, including humans. For most Canadians, the risk of getting Lyme disease is fairly low, but it is increasing. You should take steps to reduce your risk if you spend time outdoors in areas where there may be ticks.
Lyme disease is caused by a bacterium called Borrelia burgdorferi. This bacterium is normally carried by mice, squirrels, birds and other small animals. It can be passed to humans when ticks feed on infected animals, become infected themselves, and then bite people.
In Canada, there are two species of ticks known to transmit Lyme disease:
These ticks vary in size and colour, depending on their age and whether they have been feeding. Before feeding, they are about 3–5 mm in length. When they are full of blood, adult female ticks can be as large as a grape. Adult ticks are red and dark brown in colour. Younger ticks are much smaller and lighter-coloured.
You are most likely to come into contact with ticks by brushing against plants. When a tick bites you, it attaches to your skin until it is removed.
You are most at risk of being exposed to Lyme disease in the regions where blacklegged and western blacklegged ticks can be found. But migratory birds can also carry these ticks to other parts of Canada. Researchers believe that ticks may be establishing themselves in new areas that are not yet identified. This means there is a risk that people in other regions of Canada may also be exposed to infected ticks.
Your risk of coming into contact with ticks begins when the weather warms up in the early spring and lasts through to the end of fall. Ticks may also be active in winter in areas with mild temperatures and minimal snowfall. Although ticks can be active throughout much of the year, your risk of getting Lyme disease, especially in areas where tick populations are established, is greatest during the summer months when younger ticks are most active.
Lyme disease is not spread from person to person. And although cats and dogs can get Lyme disease, there is no evidence that they pass the infection to people. Pets can, however, carry infected ticks into your home or yard.
Although the symptoms and health effects are different from one person to the next, Lyme disease is often described in three stages:
Lyme disease can usually be treated effectively with antibiotics. A rapid recovery is more likely when treatment begins in the early stages of the disease.
Remember, your risk of being exposed to Lyme disease in Canada is highest in the regions where the carrier ticks are found.
If you are going to spend time outdoors in wooded areas or tall grass that may be tick-infested:
Some Canadians have contracted Lyme disease when they travelled to the United States, where there are a larger number of higher-risk areas. You should be careful when travelling and doing outdoor activities along the Atlantic seaboard from Maine to Virginia, in northern mid-west states and in states on the Pacific Coast. Travellers to Europe and Asia may also be at risk of contracting Lyme disease.
The Public Health Agency of Canada has been involved for more than a decade in research to monitor the occurrence of Lyme disease in Canada. The Agency also works with provincial, national and international experts to address key issues related to Lyme disease, including:
The Canadian Institutes of Health Research (CIHR) is funding a health research project on Lyme disease. This health research project will lead to further understanding of the pathogen causing Lyme disease.
You can also call toll free at 1-866-225-0709 or TTY at 1-800-465-7735*
Updated : May 2012
Original: March 2006
©Her Majesty the Queen in Right of Canada, represented by the Minister of Health, 2012