Disease Carrying Ticks of Canada
THE BLACKLEGGED (DEER) TICK
Because it is common to find many Blacklegged adult ticks feeding on deer, this species is sometimes referred to as the deer tick, but its official common name is the Blacklegged tick. Larvae and nymphs feed mainly on small mammals and birds, but these ticks will bite people at any stage of their life cycle. Ixodes Scapularis nymphs are active from early May to late September, though they can be abundant in the environment and on hosts during June and July. Adults prefer to be active and feed in the fall or early spring. Well-fed females can produce an average of 4000 eggs (range 2500–7000) over a period of 17–51 days. That’s a lot of ticks!
Each year Blacklegged ticks attached to migrating birds making the journey from the United States are carried into different parts of Canada. A percentage of these ticks are infected with B. burgdorferi and Anaplasma Phagocytophilum, the agents of Lyme disease and human anaplasmosis, respectively. These introduced ticks represent a persistent risk of disease transmission to people and domestic animals over a large portion of Canada. There are areas with established Blacklegged tick populations such as Manitoba, Ontario, Québec, New Brunswick, and Nova Scotia. In the prairies the risk of infection is lower because there are fewer nymphs. Although we are unsure if they are able to survive our winters, we are noticing more ticks throughout Alberta and Saskatchewan.
Blacklegged ticks tend to like deciduous or coniferous woodlands, although they have been found on lawns and ornamental shrubbery in suburban residential areas.
ROCKY MOUNTAIN WOOD TICK
This tick is common along the Rocky Mountain Range which is how it gets its name. In Canada, populations can be found in British Columbia, Alberta, and Saskatchewan. In Saskatchewan, these ticks can be found sporadically in central and western regions of the province.
Adult Rocky mountain Wood ticks are usually most active on warm, humid days, in the late afternoon or early evening. They can also be active at night. They prefer to live in clearings along power lines or logging roads, and can be found near shrubby, rocky outcrops, and in open grassy areas. In prairie habitats, adults will live in open rangelands, but are abundant in sparse vegetation, dried riverbeds and coulees.
Nymphs begin to seek hosts as soon as the snow melts, typically from March to early May, depending on the area.
On people, you are most likely to find a Rocky Mountain Wood tick attach to the scalp, though they occasionally bite other parts of the body including the shoulders, back, and groin. Adults often bite humans, but unlike Blacklegged ticks, larvae and nymphs rarely bite people. Their bite does not cause pain, and because they have short mouthparts, they are easy to remove.
These ticks have been known to spread pathogens responsible for Tularaemia, Rocky Mountain spotted fever, and Colorado tick fever in Canada. Adult ticks are most likely to spread these diseases to humans because immature ticks of this species rarely feed on people.
AMERICAN DOG TICK
The American Dog tick is widely distributed and abundant from Saskatchewan east to the Atlantic Provinces. The American dog tick tends to prefer highly wooded, shrubby, and long-grass areas. This tick has expanded its range in Manitoba and Saskatchewan and is established considerably further north and west than in previous decades.
Adult dog ticks will often bite humans and their bites typically do not cause any pain. They have been known to carry the pathogen responsible for Lyme disease, but we currently do not believe they can spread the disease to humans. Dog ticks can transmit the pathogens responsible for Tularaemia, and Rocky Mountain spotted fever to humans in Canada, however, the probability of acquiring a tick-borne pathogen from this species is very low. In the United States this species is also known to transmit a deadly disease to cats.
Photos from URI TickEncounter Resource Center. Images may not be to scale.