To get Lyme disease, a person must be bitten by a blacklegged tick that is infected with the Borrelia burgdoferi bacteria. The risk of human infection increases with the time a tick is attached to a person and usually requires the tick to be attached for 24 hours or more.
The risk of acquiring Lyme disease in Toronto overall is believed to be low. However, the risk for exposure is highest in wooded, bushy areas where ticks that transmit Lyme disease have been found, including Rouge Valley, Morningside Park, and Algonquin Island. In 2015, blacklegged ticks were found in these areas of the city and in greater numbers in 2016. Personal protective measures should be taken when visiting these areas.
Ticks are found in wooded or bushy areas with lots of leaves on the ground or where there are tall grasses. Lawns, mowed grass, sports fields or paved areas are not where blacklegged ticks are usually found. Ticks cannot fly or jump. Instead they wait for a host (person, animal or bird), resting on the tips of grasses and shrubs. If a person brushes the spot where a tick is waiting, it quickly climbs aboard. It then finds a suitable place to bite. Ticks can attach to any part of the human body but, if found, may be in hard-to-see areas such as the armpits, groin and scalp.
Blacklegged ticks pass through three different active life stages (larva, nymph, adult). Ticks are small, ranging in size from a poppy seed to a pea. The size of the tick varies depending on its life stage and whether it has fed recently.
The nymphal stage typically occurs during the summer months and is the stage most responsible for human infections. This is due to their very small size (less than 2 mm) which prevents people from noticing them on their body. Adult ticks can also transmit Lyme disease bacteria, but they are larger (5 mm) and therefore more likely to be discovered and removed before they have had time to transmit the bacteria.
Early detection and removal of ticks is important in the prevention of Lyme disease.
If the tick was attached for 24 hours or more, your doctor may prescribe an antibiotic to prevent Lyme disease. The antibiotic must be taken within 72 hours from the time that the tick was removed.
When participating in outdoor activities in wooded or bushy areas, you can take the following precautions to avoid tick bites. For known Lyme disease risk areas refer to the Public Health Agency of Canada.
How to avoid tick bites
- Long pants and long sleeves are recommended. Light coloured clothing may make ticks easier to spot
- Apply insect repellent containing DEET or icaridin and follow the manufacturer's instructions
- After spending time outdoors in wooded or bushy areas, shower to remove ticks before they become attached. Check your full body and head for attached ticks.
- If you find a tick on your body, remove it as soon as possible.
- Remember to also check your children and pets for ticks
On your property
- Mow the lawn regularly; remove leaf litter, brush and weeds from the edge of the lawn
- Keep tree branches and shrubs trimmed to let in more sunlight
- Move children's swing sets and sandboxes away from the woodland's edge and consider placing them on a woodchip or mulch foundation
- Ticks feed on rodents, deer and birds. Discourage rodents by sealing stonewalls and small openings around the yard. Use plantings that do not attract deer or exclude deer by fencing. Keep bird feeders away from the house.