Lyme disease is caused by a bacterium called Borrelia burgdorferi which is spread by ticks. B. burgdorferi has been found in two species of ticks in BC: Ixodes pacificus and Ixodes angustus, also known as western black-legged ticks.
Ticks are tiny bugs about the size of sesame seeds,
that feed on blood. The ticks in BC prefer to get their blood meal from rodents
and small animals. Sometimes a tick will bite a person accidentally instead of
biting an animal. While most tick bites do not result in disease, some do.
Ixodes ticks are distributed throughout BC. However,
most ticks that carry Lyme disease are found in southwestern BC, including
Vancouver Island, the Gulf Islands, the Sunshine Coast, Greater Vancouver, and the
Fraser Valley. The geographic distribution of Lyme disease in people and in
ticks in BC has remained constant over time.
In BC, less than 1 percent of ticks tested carry the
bacteria B. burgdorferi that cause Lyme disease. The prevalence of B. burgdorferi
in ticks in BC has remained consistently low over time.
Ticks live in tall grass and forested areas and
attach to people or animals as they pass by. Ticks burrow part way into the
skin, bite, draw blood, and then drop off. Ticks can be found year-round but
they are most likely to bite in the spring (from March to June).
The risk of Lyme disease in BC is lower and more
stable than it is in eastern and central Canada and in the northeastern USA. In these
regions, Lyme disease rates in humans and ticks have increased with climate
change. Reasons for this difference include:
• The ticks species capable of
carrying Lyme disease in BC are different. I. pacificus and I. angustus
(western black-legged ticks) are less capable of carrying B. burdorferi than I.
scapularis (black-legged tick), the tick in eastern Canada.
• The animals on which ticks
feed are different. In BC, ticks feed on small rodents such as deer mice and
dusky-footed woodrat. In eastern Canada and the USA, ticks feed on white-footed
mice and white-tailed deer.
• The vegetation and climate are
different between BC and eastern Canada (e.g. BC has mostly
coniferous forests, whereas eastern Canada has mostly leafy forests).
• Ixodes ticks are present
throughout southern and central BC, including in most of the highly populated
areas. An expansion of the range of these ticks, which could occur with climate
change, will not greatly increase the number of people exposed in BC.