Lyme Disease in Ontario: Symptoms, Risk Areas, and How to Protect Your Family

Medical disclaimer: This article provides general public health information about Lyme disease risk in Ontario. Always consult a licensed healthcare provider for medical advice, diagnosis, and treatment. Part of our Ultimate Tick Control Guide for Ontario Homeowners.

Last June, a Brampton mom found a tiny dark speck on the back of her nine-year-old's knee after an afternoon at Chinguacousy Park. She almost mistook it for a freckle. It wasn't. The tick had been attached long enough that her doctor ordered a precautionary course of antibiotics. Her daughter was fine. But she called us the next day asking what she could do so it never happened again.

That story is not unusual. Lyme disease is now the most commonly reported vector-borne illness in Canada, and southern Ontario sits squarely in the highest-risk zone. Here is what every GTA homeowner needs to know.

What Is Lyme Disease?

Lyme disease is a bacterial infection caused by Borrelia burgdorferi, transmitted to humans through the bite of an infected blacklegged tick (Ixodes scapularis), also called the deer tick. The tick picks up the bacterium by feeding on white-footed mice and other small mammals during its larval and nymph stages. When that same tick later feeds on a person, it can pass the pathogen into the bloodstream.

It is not contagious between people or between pets and people. You cannot catch it from touching a tick that is not attached, and a bite does not guarantee infection — not every blacklegged tick carries the bacterium. But given how difficult ticks are to spot (nymphs are the size of a poppy seed) and how serious late-stage Lyme can become, prevention is far better than treatment.

Is Lyme Disease a Real Risk in Ontario?

Yes — and the risk has grown substantially. Public Health Ontario surveillance data shows a steady increase in confirmed Lyme disease cases province-wide over the past decade. The primary driver is range expansion: blacklegged ticks have moved northward into southern and central Ontario as milder winters allow them to survive and reproduce in areas that were previously too cold.

Public Health Ontario currently identifies the following as areas with established or growing blacklegged tick populations:

• Mississauga / Peel Region: Credit Valley, Rattray Marsh, and adjacent conservation corridors. See our Mississauga tick control service.
• Hamilton: Dundas Valley, Cootes Paradise, and the Niagara Escarpment trails carry some of the highest tick densities in the province. See our Hamilton tick control service.
• Toronto: Don Valley ravines, High Park, and connected green corridors have confirmed populations. See our Toronto tick control service.
• Oakville and Burlington: Bronte Creek, Royal Botanical Gardens, and escarpment greenways are active risk zones. See our Oakville and Burlington tick control services.
• Brampton: Humber River corridor and park edges. See our Brampton tick control service.

If your backyard backs onto a ravine, a greenbelt, a conservation area, or even an unmaintained neighbour's lot, blacklegged ticks can migrate onto your property on deer and small mammals.

Symptoms of Lyme Disease in Humans

Early localised (3–30 days after bite)

• Bull's-eye rash (erythema migrans) expanding outward from the bite site — present in roughly 70–80% of cases
• Fever and chills
• Fatigue that feels out of proportion to activity
• Headache
• Muscle and joint aches
• Swollen lymph nodes near the bite

The absence of a rash does not rule out infection. Some people develop no visible rash at all, or the rash appears in a location that is easy to miss (scalp, behind the knee, in a skin fold).

Early disseminated (days to weeks after bite)

• Multiple rashes appearing elsewhere on the body
• Bell's palsy (facial drooping on one or both sides)
• Severe headaches and neck stiffness
• Heart palpitations or irregular heartbeat (Lyme carditis)
• Shooting pain, numbness, or tingling in the hands and feet

Late disseminated (months after bite, if untreated)

• Severe arthritis, particularly in the knees
• Cognitive difficulties, memory problems, brain fog
• Chronic fatigue

If you develop any of these symptoms and have had a tick bite, or have been in tick habitat in the GTA recently, see your doctor and mention the possible exposure. Early antibiotic treatment almost always results in full recovery.

Lyme Disease Symptoms in Dogs and Cats

Your pets spend more time low to the ground than you do, which makes them effective tick magnets. A dog that walks the same ravine trail you do is likely picking up more ticks — and carrying some of them back into your home.

Dogs

Dogs are genuinely susceptible to Lyme disease. Symptoms often appear 2–5 months after infection and can include:

• Sudden lameness that shifts from leg to leg over days
• Swollen, painful joints
• Fever (above 39.5°C)
• Loss of appetite and lethargy
• Swollen lymph nodes
• In rare severe cases, kidney disease (Lyme nephropathy)

A Lyme vaccine is available for dogs and is worth discussing with your veterinarian if you live near ravines or conservation areas. Year-round tick preventatives are also recommended for dogs in the GTA.

Cats

Cats appear more resistant to clinical Lyme disease than dogs, but they can still carry ticks into your home and onto furniture. If your cat goes outdoors in tick habitat and develops unexplained lethargy, fever, or limping, raise tick exposure with your vet. Never apply dog-specific tick treatments to cats — many are toxic to felines.

How Lyme Disease Transmission Works

Understanding the timeline of transmission explains why prompt tick removal is so effective:

• A tick must be attached and feeding for approximately 24–36 hours before it can transmit Borrelia burgdorferi
• Nymph-stage ticks (tiny, hard to see) cause the majority of human Lyme cases because they go unnoticed longer
• Peak nymph activity in Ontario runs May through July — overlapping with garden season, children's outdoor sports, and dog walking
• Adult ticks are active in spring and again in fall, and are easier to spot due to their larger size
• Ticks do not jump or fly — they quest by holding onto tall grass or brush with their back legs and reaching forward with their front legs, waiting for a host to brush past

What to Do If You Find a Tick

Stay calm. The 24–36 hour transmission window means you have time to act correctly:

1. Use fine-tipped tweezers. Grasp the tick as close to the skin as possible. Do not use your fingers.
2. Pull straight up with steady, even pressure. Do not twist or jerk — this can cause mouthparts to break off in the skin.
3. Do not crush, burn, or apply petroleum jelly. These methods are ineffective and may increase transmission risk.
4. Clean the area with rubbing alcohol or soap and water.
5. Save the tick in a sealed bag or container with the date noted. You can submit it for identification at eTick.ca, a free Public Health Agency of Canada tool that provides species identification and risk assessment.
6. Monitor for symptoms for 30 days. See a doctor if a rash, fever, or flu-like illness develops. Mention the tick bite and the date.

As an Amazon Associate, BuzzSkito earns from qualifying purchases. BuzzSkito only points to products we would genuinely use or recommend, at no extra cost to you.

A purpose-made removal hook like the Tick Twister grips the mouthparts at skin level without squeezing the body — worth keeping in the first-aid kit if you live near a ravine or walk a dog daily. Check price on Amazon.ca →

For a detailed step-by-step guide including what to do with the tick after removal, see our post on how to remove a tick safely.

How to Protect Your Family from Lyme Disease This Season

The most effective approach combines several layers. None of them are particularly hard — the trick is doing all of them rather than picking one.

In your yard

Ticks don't live in the middle of a sunny lawn. They concentrate in the transition zones: where the mowed grass meets a garden bed, a wood edge, a leaf pile, or a shaded fence line. Reducing these microhabitats helps:

• Keep grass mowed short and clear leaf litter regularly
• Move woodpiles away from the house and off the ground
• Place a 60–90 cm barrier of wood chips or gravel between lawn and wooded borders
• Discourage deer with fencing if your property backs onto a greenbelt

A passive layer worth adding: permethrin tick tubes let mice carry treated cotton back to their nests, killing the larval ticks that feed on them before those ticks ever quest for your family. Commercial tubes are formulated and labelled for exactly this use, which matters in Canada — PMRA rules say a permethrin product may only be used the way its own label says. See our guide to tick tubes in Canada for placement and timing.

For the most reliable yard protection, professional tick barrier spray treats exactly the zones where blacklegged ticks hide and wait. Our tick control treatments apply a Health Canada-registered residual formula to garden edges, foundation plantings, shaded turf, and wood borders — the areas that matter. One treatment provides up to 30 days of protection, which is why the seasonal program is five treatments spread roughly monthly from May through September — $597 standalone, or $497 added to any mosquito plan.

The monthly cadence is the whole point. Nymphs — the poppy-seed-sized stage that drives most Lyme transmission because it is so easily missed — peak from May through July, and adults re-emerge and stay active through the autumn, into November in mild years. A pair of visits timed to spring and fall would leave a multi-month gap right across nymph season, which is precisely the wrong window to be uncovered. Deer, mice and birds also keep carrying fresh ticks in from the ravine or woodlot next door, so the barrier has to be renewed rather than applied once or twice and left to lapse.

Your kids shouldn't have to stay off the grass. Your dog shouldn't come home from the backyard with a passenger. Professional treatment is the one layer that works while you're not thinking about it.

On your body

• Apply Health Canada-approved repellent containing DEET (20–30%) or icaridin to exposed skin. Icaridin repellent on Amazon.ca →
• Wear light-coloured clothing — ticks are easier to spot on pale fabric
• Tuck pants into socks in long grass or wooded areas
• Permethrin-treated clothing provides excellent protection for people who spend a lot of time outdoors — permethrin gaiters cover the ankle-to-knee zone where most ticks latch on. Permethrin gaiters on Amazon.ca →

For a full head-to-toe rundown of treated clothing options, see our bug-protective clothing guide for Canada.

After being outdoors

• Do a full tick check of yourself, children, and pets within two hours of coming inside — pay attention to the scalp, behind the ears, armpits, groin, and behind the knees
• Shower within two hours; this helps rinse off unattached ticks and makes a full check easier
• Tumble dry clothing on high heat for 10 minutes — heat kills ticks that clothing removal alone may miss

For your pets

• Ask your veterinarian about the Lyme vaccine and tick preventatives suitable for your dog's size and lifestyle
• Check pets after every outing near natural areas
• Keep dogs on trails rather than bushwhacking through long grass

Frequently Asked Questions About Lyme Disease in Ontario

Related Guides

• The Ultimate Tick Control Guide for Ontario Homeowners
• How to Identify Ticks in Ontario
• How to Remove a Tick Safely
• When Are Ticks Active in Ontario?
• Best Tick Control for Your Yard: Ontario Comparison Guide
• BuzzSkito Tick Control Services

BuzzSkito is a licensed mosquito and tick control provider serving Mississauga, Toronto, Brampton, Oakville, Burlington, Hamilton, and the broader GTA. Our technician is trained in integrated pest management and applies only Health Canada-registered products. For medical advice on tick bites or Lyme disease, consult a licensed healthcare provider. For tick identification, visit eTick.ca or Public Health Ontario.