Ticks and Lyme Disease

The Public Health Agency of Canada (PHAC) works with the provinces, health authorities and other experts on research to define and monitor the occurrence of the ticks that carry Borrelia burgdorferi, the bacterium that causes Lyme disease. In Canada, the blacklegged tick (Ixodes scapularis; often referred to as a 'deer tick') and the western blacklegged tick (Ixodes pacificus) are the species known to transmit this disease causing agent, as well as other less common agents.

Established Tick Populations
Identifying Blacklegged Ticks
Submitting Ticks for Identification and Testing

Established Tick Populations

In Ontario lacklegged tick populations can be found in Long Point; Point Pelee National Park; Rondeau Provincial Park; Turkey Point; Prince Edward Point; Presqu'île Provincial Park; and St. Lawrence Islands National Park in the Thousand Islands region of eastern Ontario. In Nova Scotia, blacklegged tick populations are known in the Lunenburg, Bedford and Liverpool areas. An established population has also been found in the Buffalo Point area of southeastern Manitoba. Western blacklegged ticks, on the other hand, are found in British Columbia; they are fairly widely distributed but populations are largest in the lower mainland, on Vancouver Island and in the Fraser Valley.

Although the distribution of blacklegged ticks in Canada appears to be limited, surveillance indicates that some of the established populations are spreading within certain areas of southern Canada. The potential expansion of localized tick populations makes it difficult to precisely define the geographic limits of any given population; however people living or visiting areas adjacent to established tick populations may have a greater chance of contact with blacklegged ticks. Although current evidence does not suggest a widespread distribution of blacklegged tick populations in Canada, the establishment of new populations appears to be an ongoing process. Hence continuing surveillance and precautions to reduce tick contact is desirable.

Visitors to the United States should note that there are extensive areas with established blacklegged tick populations there, particularly in the northeast and upper Midwest regions. More information on Lyme in the USA can be found on the Centers for Disease Control and Prevention web site ( http://www.cdc.gov/ncidod/dvbid/lyme/index.htm ).

The rate of infection of ticks with the bacterium causing Lyme disease varies. Infection rates are typically higher in adult ticks compared to the other stages (nymphs and larvae). Despite the lower rates of infection, people are most likely to acquire Lyme disease from a nymph because this stage is so small (see figure 2) and thus more likely to go unnoticed and feed for a sufficient amount of time for the Lyme disease bacterium to be transmitted (24-36 hours). Infection rates are often greater in tick populations that have been established for long periods of time (such as Long Point) compared to newly established ones. As many as 60% of the adult ticks at Long Point are infected; however, infection rates in adults are more often between 10 and 25% at the other localities where ticks are established. Partly because of differences in the types of hosts that they feed upon, infection rates of the Lyme disease agent in Ixodes pacificus are much lower (1-3%) than Ixodes scapularis.

While there is a higher risk to come in contact with infected blacklegged ticks in areas where populations are established, there is also a low risk of Lyme disease being contracted almost anywhere in Canada because migratory birds transport infected ticks over large geographic distances. Surveillance data indicates that about 10% of the ticks detected outside of areas where tick populations are established, and likely transported there on migratory birds, are infected with the agent of Lyme disease.

Identifying Blacklegged Ticks

Blacklegged ticks are considerably smaller than the more common American dog tick (often called the wood tick) and they lack the white marking seen on the dog tick's back (Figure 1). Before feeding, blacklegged adult females are approximately 3-5 mm in length and red and dark brown in colour. The pre-adult stages (larvae and nymph) are much smaller and lighter in colour (Figure 2). All stages except adult males increase in size and change colour as they feed upon a host. For example, it is not uncommon for adult females to reach the size of a grape and they typically go through a change in colour from whitish as they start feeding to dark gray to nearly black when fully fed (Figure 3). Larvae and nymphs also increase proportionally in size and go through a similar change in colour (Figure 4).

Figure 1: Unfed adult blacklegged ticks (top row) and adult American dog (wood) ticks (bottom row). Note the difference in colour patterns and relative size.

Figure 2: Life stages of the blacklegged tick (1-larva, 2-nymph, 3-adult male, 4-adult female). Sizes presented in relation to underlying 10-cent coin.

Figure 3: Female blacklegged ticks in various stages of feeding. Note the change in size and colour.

Figure 4: Unfed, partially fed and fully engorged nymphs of the blacklegged tick. Note the change in size and colour.

Submitting Ticks for Identification and Testing

Scientists at PHAC's National Microbiology Laboratory (NML), in collaboration with provincial and territorial colleagues, have been studying the distribution of the blacklegged tick since the early 1990s. The information gathered from these studies helps to determine the current range of this tick in Canada and to better define the areas of risk of human exposure to infected blacklegged ticks.

Ticks collected by members of the general public, veterinarians, medical professionals and wildlife biologists from pets, people, or wild animals can be submitted for identification and testing. This passive surveillance helps to identify areas for further research.

To remove ticks that are embedded in skin, use tweezers to carefully grasp the tick as close to the skin as possible and pull slowly upward, avoiding twisting or crushing the tick. Do not try to burn or smother the tick. Cleanse the bite area with soap and water, alcohol or household antiseptic. Note the date and location of the bite and save the tick in a secure container such as an empty pill vial or film canister. A bit of moistened paper towel placed inside the container will keep ticks from drying out. Dried out ticks are more difficult to identify and test for infection. If you are concerned about removing a tick from yourself or a member of your family, it is advisable to ask for assistance from a medical practitioner. A medical practitioner will also be able to inform you of the possible symptoms of tick-borne diseases such as Lyme disease (http://www.phac-aspc.gc.ca/id-mi/lyme-fs_e.html#4) so that if you show these symptoms you can recognize them and be promptly treated. Similarly your local veterinarian will be able to remove ticks from your pets and advise on any treatments they may require.

Ticks are usually sent to one of the provincial/territorial collaborators who determine the type (species) and then forward blacklegged ticks to the NML for diagnostic testing for the Lyme disease agent as well as several other disease-causing agents. Someone coming in contact with a tick who would like to have it identified (and possibly tested for infectious agents) can contact the NML at the address below for details on where to send the specimen in their province or territory:

National Microbiology Laboratory
1015 Arlington Street
Winnipeg, MB R3E 3R2
Phone: (204) 789-2000
Email: ticks@phac-aspc.gc.ca