Medical disclaimer: This article provides general public health information about tick risks in Ontario. Always consult a licensed healthcare provider for medical advice. Part of our Ultimate Tick Control Guide for Ontario Homeowners.
The Short Answer: Yes, Ticks Are Dangerous in Ontario
Ticks in Ontario are not just a nuisance — they are a legitimate health risk. The blacklegged tick (Ixodes scapularis), now established across virtually all of Southern Ontario, can transmit Lyme disease, Anaplasmosis, Babesiosis, and Powassan virus. The number of confirmed Lyme disease cases in Canada has increased more than tenfold over the past decade, and the geographic range of disease-carrying ticks continues to expand northward every year.
For GTA homeowners, the days of dismissing ticks as a "cottage country problem" are over. Toronto ravines, Mississauga conservation areas, Hamilton escarpment trails, and suburban backyards across the region now harbour established blacklegged tick populations.
Which Ticks in Ontario Are Dangerous?
Ontario is home to several tick species, but they carry very different levels of risk:
Blacklegged Tick (Ixodes scapularis) — Highest Risk
The blacklegged tick (also called the deer tick) is the most medically significant tick in Ontario. It carries:
- Lyme disease (Borrelia burgdorferi) — the most common tick-borne disease in Ontario
- Anaplasmosis — an emerging bacterial infection that can cause severe flu-like symptoms
- Babesiosis — a parasitic infection that destroys red blood cells
- Powassan virus — rare but potentially fatal, can transmit in as little as 15 minutes
- Borrelia miyamotoi — tick-borne relapsing fever
See: Complete List of Tick-Borne Diseases in Ontario
American Dog Tick (Dermacentor variabilis) — Lower Risk
The American dog tick is the most commonly encountered tick species in Ontario. It is larger and more visible than the blacklegged tick. While it can theoretically transmit Rocky Mountain Spotted Fever and tularemia, these diseases are extremely rare in Ontario. The primary concern with dog ticks is nuisance biting and the potential for allergic reactions at the bite site.
Lone Star Tick (Amblyomma americanum) — Emerging
The lone star tick is occasionally found in Southern Ontario, likely transported by migratory birds from the eastern United States. It is associated with alpha-gal syndrome (a red meat allergy triggered by tick saliva), ehrlichiosis, and STARI. The lone star tick is not yet considered established in Ontario, but detections are increasing.
See: How to Identify Ticks in Ontario
How Common Is Tick-Borne Disease in the GTA?
Lyme disease is a reportable disease in Ontario, meaning every confirmed case must be reported to public health authorities. The numbers tell a clear story of escalating risk:
- Confirmed Lyme disease cases in Canada have risen from fewer than 150 per year a decade ago to well over 2,000 per year — Ontario accounts for a significant share
- Blacklegged ticks have been confirmed through active surveillance in every GTA municipality
- Infection rates in blacklegged tick populations in established Southern Ontario risk areas range from approximately 20% to 40%
- Cases of Anaplasmosis and Babesiosis, while still uncommon, are being detected with increasing frequency
The risk is not theoretical — people in the GTA are contracting Lyme disease from tick bites acquired in their own backyards, local parks, and neighbourhood trails.
Why the Risk Is Growing
Several converging factors are making ticks more dangerous in Ontario with each passing year:
- Climate change: Warmer winters allow blacklegged ticks to survive and reproduce further north. Ticks that could not overwinter in central Ontario a decade ago now thrive year-round across the GTA
- Geographic expansion: The blacklegged tick range expands approximately 35-55 km northward per decade, driven by warming temperatures and bird-mediated dispersal
- Suburban encroachment: New housing developments at the urban-rural interface bring humans into direct contact with tick habitat
- Deer population growth: White-tailed deer — the primary host for adult blacklegged ticks — have thrived in suburban environments across Southern Ontario
- Longer active season: Blacklegged ticks are active on any day above 4°C, and Ontario is experiencing more warm days earlier in spring and later into fall
Ticks in Your Own Backyard
One of the most important things GTA homeowners need to understand is that tick exposure does not require a hike in a provincial park. Ticks live in:
- Leaf litter along fence lines and garden borders
- Tall grass and unmowed field edges
- Shaded areas under shrubs and low branches
- Stone walls, wood piles, and garden beds
- The transition zone between lawn and wooded or naturalized areas
Any GTA property that borders a ravine, conservation area, woodlot, or naturalized landscape has potential tick habitat within the property boundary. Even properties without direct woodland borders can have ticks introduced by deer, rodents, or birds passing through the yard.
How to Protect Your Family
Professional Tick Treatment
Professional tick barrier spray is the most effective way to reduce tick populations on your property. Treatment targets the high-risk perimeter zones — garden edges, fence lines, shaded vegetation, stone walls, and the lawn-to-woods transition — reducing tick populations by up to 90%. Most GTA homeowners schedule two treatments per year: one in late May (targeting nymphs) and one in late August (targeting adult ticks before fall peak).
Yard Modifications
- Remove leaf litter — the most critical overwintering habitat for ticks
- Mow your lawn regularly (under 3 inches)
- Create a 1-metre gravel or wood chip barrier between your lawn and any wooded border
- Stack firewood in dry, sunny locations away from the house
- Clear brush and overgrown vegetation along fence lines
Personal Protection
- Wear light-coloured clothing when walking in wooded or grassy areas
- Apply DEET (20-30%) or icaridin repellent to exposed skin
- Tuck pants into socks in tick-prone areas
- Do full-body tick checks within 2 hours of outdoor activity
- Shower promptly after being outdoors
Know What to Do After a Tick Bite
If you find a tick attached to your skin:
- Remove it immediately with fine-tipped tweezers — grasp as close to the skin as possible and pull straight up with steady pressure
- Clean the bite area with rubbing alcohol or soap and water
- Save the tick (in a sealed bag or container) for identification
- Note the date and location of the bite
- Monitor for symptoms for 30 days — especially a bull's-eye rash, fever, or joint pain
- Consult your doctor if any symptoms develop
See: How to Remove a Tick Safely | Tick Bite Symptoms & What to Do
Protecting Pets
Dogs are highly susceptible to tick bites and can contract Lyme disease, Anaplasmosis, and Ehrlichiosis. Every GTA dog that spends time outdoors should be on year-round tick prevention medication prescribed by a veterinarian. Professional yard treatment provides an additional layer of protection by reducing the tick population your pets encounter in their own yard.
Cats can also be bitten by ticks but are less commonly affected by tick-borne diseases. Consult your veterinarian about feline tick prevention options if your cat goes outdoors.
The Bottom Line
Ticks are dangerous in Ontario — and the risk is not decreasing. The geographic range of disease-carrying blacklegged ticks expands every year, infection rates in tick populations are significant, and Lyme disease cases continue to climb. The GTA is firmly within the established risk zone.
The good news is that tick-borne disease is highly preventable through a combination of professional yard treatment, habitat modification, personal protection, and prompt tick removal. The key is taking the risk seriously and acting before tick season peaks.
Frequently Asked Questions
Are all ticks in Ontario dangerous?
Not all Ontario tick species carry the same risk. The blacklegged tick (Ixodes scapularis) is the most dangerous because it transmits Lyme disease, Anaplasmosis, Babesiosis, and Powassan virus. The American dog tick — the most commonly encountered species — can transmit Rocky Mountain Spotted Fever and tularemia, but these are extremely rare in Ontario. Regardless of species, any tick bite should be taken seriously: remove the tick promptly, save it for identification if possible, and monitor for symptoms.
How likely am I to get Lyme disease from a tick bite in Ontario?
Not every blacklegged tick carries Lyme disease — infection rates vary by location and year, but in established risk areas of Southern Ontario, roughly 20-40% of adult blacklegged ticks test positive for Borrelia burgdorferi. However, transmission generally requires 24-36 hours of attachment. If you find and remove a tick within 24 hours of attachment, your risk of Lyme disease transmission is very low. This is why tick checks and prompt removal are so important.
Can my dog or cat get sick from ticks in Ontario?
Yes. Dogs can contract Lyme disease, Anaplasmosis, and Ehrlichiosis from tick bites in Ontario. Cats are less commonly affected but can also be bitten by ticks. Dogs that spend time in wooded or grassy areas should be on veterinarian-prescribed tick prevention medication year-round (or at minimum from March through November). Professional yard treatment further reduces the tick population your pets encounter on your property.
Are ticks dangerous to children?
Children are at elevated risk for tick bites because they play in grass, gardens, and wooded areas where ticks are most active. Tick-borne diseases like Lyme disease affect children the same as adults. The key difference is that children are less likely to notice a tick on their body and less likely to report a bite. Parents should do thorough tick checks after any outdoor play, paying special attention to the scalp, behind ears, armpits, waistline, and behind knees.
When are ticks most dangerous in Ontario?
Ticks are most dangerous during two peak windows in Ontario. The first is May through July, when nymph-stage blacklegged ticks emerge — nymphs are tiny (poppy-seed sized), difficult to detect, and responsible for the majority of human Lyme disease cases. The second peak is September through November, when adult blacklegged ticks are most active. However, blacklegged ticks can be active on any day when temperatures exceed 4°C, including mid-winter warm spells.