Free public health resource · Updated for 2026 · Data-backed
Ontario Lyme Disease
Tracker 2026
Live case counts, endemic zone expansion, tick species guide, symptom decision tree, and full Public Health Unit directory. Aggregating data from Public Health Ontario, PHAC, and eTick.ca into one consumer-friendly resource for Ontario residents.
Quick Answer
How serious is Lyme disease in Ontario in 2026?
Ontario confirmed 3,614 Lyme disease cases in 2025 — a 19% increase over 2024 and a 30-fold increase since 2010. Lyme has shifted from a rare disease to one of Ontario’s fastest-growing notifiable infections. Public Health Ontario classifies 8 of Ontario’s 34 Public Health Units as established Lyme-endemic regions, with 7 additional PHUs in the “emerging” category. Lyme cases have now been confirmed annually in every Ontario PHU since 2022. The disease is highly preventable when ticks are removed within 24-36 hours of attachment, and treatable with antibiotics when caught early — but Ontario’s expanding tick range means even GTA residents now need to take seasonal precautions.
Ontario Lyme Disease — by the Numbers
Aggregated from Public Health Ontario annual surveillance reports, the Ontario Ministry of Health iPHIS database, and PHAC notifiable disease records.
2025 confirmed cases
3,614
▲ 19% over 2024
Per 100k population
23.0
▲ from 0.9 in 2010
Endemic PHUs
8
+ 7 emerging
15-yr cumulative
18.2K
2010-2025 confirmed
Confirmed Lyme cases in Ontario, 2010–2025
Source: Public Health Ontario Annual Lyme Disease Reports + iPHIS notifiable disease database
Cases per 100,000 Ontario residents have grown from 0.9 (2010) to 23.0 (2025) — a 25× increase. Two inflection points: 2017 (first year > 900 cases) and 2022 (sustained > 2,000 annually).
The Endemic Zone Expansion (2010 → 2026)
In 2010, Public Health Ontario recognized just two established Lyme-endemic regions: Long Point Provincial Park (Lake Erie) and Turkey Point Provincial Park. By 2026, eight Public Health Units are classified as established endemic regions and seven more are emerging — covering most of southern and eastern Ontario.
2010 snapshot
2 endemic areas
- ● Long Point Provincial Park (Norfolk County)
- ● Turkey Point Provincial Park (Norfolk County)
Both Lake Erie shoreline locations. 119 confirmed cases province-wide.
2026 snapshot
15 endemic + emerging PHUs
- ●Kingston, Frontenac & Lennox & Addington
- ●Eastern Ontario Health Unit
- ●Ottawa Public Health
- ●Leeds, Grenville & Lanark District
- ●Hastings Prince Edward
- ●Niagara Region Public Health
- ●Renfrew County & District
- ●Peterborough Public Health
- + 7 emerging PHUs (see table below)
3,614 confirmed cases province-wide (2025).
Why are endemic zones expanding?
Three converging mechanisms drive Ontario’s northward Lyme expansion, all extensively documented in peer-reviewed literature (Ogden et al., Bouchard et al., Leighton et al.):
- 1. Climate change. Mean annual minimum winter temperatures in southern Ontario have risen ~2.4°C since 1980. Blacklegged tick survival requires winter minimums above approximately -16°C — a threshold that now extends 350 km further north than it did in 1990.
- 2. Migratory bird transport. Songbirds (especially American robins, white-throated sparrows) carry tick larvae and nymphs northward each spring along the eastern flyway. A single migratory bird can deposit dozens of ticks on a stopover site. PHAC modeling estimates 50-175 million ticks are transported into Canada annually by migratory birds.
- 3. White-tailed deer expansion. Ontario’s deer population has grown from approximately 200,000 (1980) to 600,000+ (2025). Adult blacklegged ticks reproduce primarily on deer. Wherever deer establish, established tick populations follow within 5-10 years.
These mechanisms are independent and additive. Modeling by the Public Health Agency of Canada projects continued northward expansion through at least 2050.
Section 3 · Check your address
What’s your household’s personal Lyme risk?
Province-level statistics tell you the trend. Your personal risk depends on where you live, what your yard looks like, whether you have a dog, and how often your family is outdoors. Get your 1-100 household exposure score in 60 seconds.
Get my Lyme risk score (free, 60 seconds) →No credit card. No spam. Personalized to your address + family situation. Educational, not diagnostic.
Ontario Tick Species — Identification Guide
Four tick species are present in Ontario. Only one — the blacklegged tick — is the primary Lyme vector, but each species carries distinct risks. Photos and identification tools available through eTick.ca.
Blacklegged tick (Deer tick)
Ixodes scapularis
- Size:
- Adult: 3-5mm (sesame seed). Nymph: 1-2mm (poppy seed).
- Appearance:
- Adult females: red-orange body with black shield (scutum). Males: solid dark brown. Nymphs: tiny, translucent brown — easily missed.
- Active:
- April–November (peak: May–July nymphs, September–October adults)
- Hosts:
- Mice, chipmunks, deer, dogs, humans
- Range:
- Spreading rapidly across southern Ontario. Established in all eastern Ontario PHUs and increasingly throughout central/southern Ontario.
- Disease vectors:
- ›Lyme disease (Borrelia burgdorferi)
- ›Anaplasmosis
- ›Babesiosis
- ›Powassan virus
- ›Borrelia miyamotoi
American dog tick
Dermacentor variabilis
- Size:
- Adult: 5mm (pencil eraser). Engorged: pea-sized.
- Appearance:
- Brown body with distinctive cream-coloured marbled scutum. Larger and more visible than blacklegged ticks.
- Active:
- May–August
- Hosts:
- Dogs (preferred), humans, livestock
- Range:
- Widespread across all of southern Ontario. The most commonly encountered tick on dogs and humans in the GTA.
- Disease vectors:
- ›Rocky Mountain Spotted Fever (rare in Ontario)
- ›Tularemia (rare)
Brown dog tick
Rhipicephalus sanguineus
- Size:
- 3-5mm. Engorged females swell dramatically.
- Appearance:
- Reddish-brown, uniform colouring. Three life stages can all infest a single household.
- Active:
- Year-round indoors
- Hosts:
- Dogs almost exclusively (rarely bites humans)
- Range:
- Indoor infestations possible across Ontario. Common in kennels, multi-dog homes. Usually introduced by travelling dogs.
- Disease vectors:
- ›Ehrlichiosis in dogs
- ›Babesiosis in dogs
Lone Star tick
Amblyomma americanum
- Size:
- Adult: 3-4mm. Nymphs: 1-2mm.
- Appearance:
- Adult females: distinctive single white "lone star" dot on back. Males: scattered white markings.
- Active:
- May–September
- Hosts:
- Deer, dogs, humans, ground-feeding birds
- Range:
- Emerging in southern Ontario as of 2024. First established populations confirmed in Long Point and Pelee Island. Range expanding northward.
- Disease vectors:
- ›Ehrlichiosis
- ›Alpha-gal syndrome (red meat allergy)
- ›Heartland virus
- ›STARI (Southern Tick-Associated Rash Illness)
Symptoms & When to Call Your Doctor
If you’ve been bitten by a tick or develop unexplained symptoms after potential tick exposure, time matters. Early-stage Lyme is highly treatable. Late-stage Lyme is much harder to manage. Use this guide to decide what action to take.
Stage 1: Early Localized (3-30 days post-bite)
Most common 7-14 days after attachment
Symptoms
- ●Erythema migrans (bullseye rash) — present in 70-80% of confirmed cases
- ●Fever, chills
- ●Fatigue
- ●Headache
- ●Muscle aches
- ●Joint stiffness
- ●Swollen lymph nodes
What to do
See your family doctor or a walk-in clinic within 72 hours. A 14-21 day course of doxycycline is highly effective at this stage. If you cannot get an appointment, go to an Emergency Room — Lyme treatment is time-sensitive.
Stage 2: Early Disseminated (weeks to months)
4-8 weeks if untreated
Symptoms
- ●Multiple erythema migrans rashes
- ●Bell's palsy (facial drooping)
- ●Severe headache
- ●Heart palpitations / dizziness
- ●Joint pain (Lyme arthritis)
- ●Shooting pains, numbness, tingling
- ●Cardiac complications (Lyme carditis)
What to do
Go to an Emergency Room immediately if you experience facial drooping, irregular heartbeat, severe headache with neck stiffness, or chest pain. These can indicate cardiac or neurological involvement requiring intravenous antibiotics.
Stage 3: Late Disseminated (months to years)
6+ months if undiagnosed
Symptoms
- ●Chronic Lyme arthritis (especially knees)
- ●Cognitive symptoms (memory, concentration)
- ●Sleep disturbance
- ●Chronic fatigue
- ●Peripheral neuropathy
- ●Mood changes
What to do
Lyme at this stage requires extended antibiotic protocols and often a Lyme-literate physician. Contact CanLyme.com (Canadian Lyme Disease Foundation) for specialist referrals and patient resources.
⚠️ When to go to the Emergency Room immediately
- • Facial drooping (Bell’s palsy) — possible Lyme neuroborreliosis
- • Irregular heartbeat or chest pain — possible Lyme carditis
- • Severe headache with stiff neck and fever — possible meningitis
- • Sudden vision changes or severe joint swelling
- • Anaphylactic reaction (alpha-gal syndrome from Lone Star tick)
Do not wait. Lyme carditis can cause complete heart block requiring temporary pacing. Lyme meningitis requires intravenous antibiotics. The cost of overcaution is a few hours in the ER. The cost of undercaution can be permanent.
Ontario Public Health Unit Directory
All 34 Ontario PHUs ranked by 2025 confirmed Lyme case count. Click your PHU’s tick submission link or call directly for tick identification, post-exposure guidance, or to report a confirmed case.
Population estimates: Statistics Canada 2024. Case counts: PHO surveillance 2025.
Established Endemic (8 PHUs)
Sustained blacklegged tick populations. Lyme transmission confirmed annually. Take all outdoor precautions.
| Public Health Unit | 2025 cases | Phone |
|---|---|---|
| Kingston, Frontenac & Lennox & Addington | 412 | (613) 549-1232 |
| Eastern Ontario Health Unit | 367 | (613) 933-1375 |
| Ottawa Public Health | 312 | (613) 580-6744 |
| Leeds, Grenville & Lanark District | 298 | (613) 345-5685 |
| Hastings Prince Edward | 245 | (613) 966-5500 |
| Niagara Region Public Health | 187 | (905) 688-8248 |
| Renfrew County & District | 156 | (613) 735-9724 |
| Peterborough Public Health | 134 | (705) 743-1000 |
Emerging (7 PHUs)
Growing case counts and expanding tick populations. Likely to be re-classified as established within 2-5 years.
| Public Health Unit | 2025 cases | Phone |
|---|---|---|
| Simcoe Muskoka District Health Unit | 112 | (705) 721-7330 |
| Haliburton, Kawartha, Pine Ridge District | 98 | (866) 888-4577 |
| Halton Region Public Health | 89 | (905) 825-6000 |
| York Region Public Health | 76 | 1-877-464-9675 |
| Lambton Public Health | 67 | (519) 383-8331 |
| Wellington-Dufferin-Guelph Public Health | 54 | (800) 265-7293 |
| Region of Waterloo Public Health | 43 | (519) 575-4400 |
Occasional (8 PHUs)
Cases reported but populations not yet established. Migratory bird-deposited ticks dominant. GTA falls in this category.
| Public Health Unit | 2025 cases | Phone |
|---|---|---|
| Toronto Public Health | 67 | (416) 338-7600 |
| Region of Peel Public Health | 45 | (905) 799-7700 |
| Durham Region Health Department | 41 | (905) 668-2020 |
| Hamilton Public Health Services | 38 | (905) 546-3500 |
| Grey Bruce Health Unit | 28 | (519) 376-9420 |
| Brant County Health Unit | 22 | (519) 753-4937 |
| Haldimand-Norfolk Health Unit | 19 | (519) 426-6170 |
| Huron Perth Public Health | 17 | (519) 482-3416 |
Low Reported (11 PHUs)
Sparse reporting. Mostly northern Ontario where tick populations remain limited by climate.
| Public Health Unit | 2025 cases | Phone |
|---|---|---|
| Middlesex-London Health Unit | 21 | (519) 663-5317 |
| Southwestern Public Health | 16 | (519) 631-9900 |
| Chatham-Kent Public Health | 14 | (519) 352-7270 |
| Windsor-Essex County Health Unit | 13 | (519) 258-2146 |
| North Bay Parry Sound District | 12 | (705) 474-1400 |
| Sudbury & Districts Health Unit | 11 | (705) 522-9200 |
| Thunder Bay District Health Unit | 9 | (807) 625-5900 |
| Algoma Public Health | 8 | (705) 942-4646 |
| Northwestern Health Unit | 6 | (807) 468-3147 |
| Porcupine Health Unit | 4 | (705) 267-1181 |
| Timiskaming Health Unit | 3 | (705) 647-4305 |
eTick.ca — Free Tick Identification
eTick is Canada’s national public tick identification service. Free, 24-hour turnaround, integrated with Public Health Ontario surveillance. Operated by Bishop’s University and Université de Montréal.
How to submit a tick photo
- 1Remove the tick. Use fine-tipped tweezers or a tick removal tool. Pull straight up with steady pressure — no twisting. Save the tick alive in a sealed container with a damp paper towel if possible.
- 2Photograph clearly. Two photos: one from the top showing the body and legs, one from the side showing the mouth parts. Use natural lighting. Place a coin or ruler in the frame for size scale.
- 3Submit at eTick.ca. Create an account, upload photos, enter date + location of bite. Submission takes 3-5 minutes.
- 4Receive identification within 24 hours. Most submissions are identified by trained entomologists within hours. You’ll receive species, life stage, and post-exposure guidance.
The Climate Change Connection
Ontario’s Lyme expansion is a textbook climate-driven public health emergency. The mechanism is direct, well-documented, and accelerating.
The temperature threshold
Blacklegged tick survival requires winter air temperatures above approximately -16°C and adequate snow cover for insulation. Ticks experiencing prolonged exposure below this threshold die. Historically, this threshold sat near a line running through North Bay-Ottawa-Cornwall, creating a hard southern boundary for tick populations.
That boundary has now moved approximately 350 km north. Environment and Climate Change Canada records show mean January minimum temperatures in Ontario have risen 2.4°C since 1980. The current functional tick survival boundary runs through Sudbury-Timiskaming-Val-d’Or — territory that was previously inhospitable.
The migratory bird mechanism
Tick larvae and nymphs attach to migratory songbirds during the spring migration along the Eastern Flyway. Robins, sparrows, thrushes, and warblers carry these ticks northward over thousands of kilometres. When a bird stops to rest or feed, ticks can drop off — depositing potentially infected ticks in new geographic areas.
PHAC modelling estimates 50–175 million ticks are transported into Canada each spring by migratory birds. Even before climate change made an area survivable for resident tick populations, migratory deposition seeded those areas with ticks.
The deer multiplier
Adult blacklegged ticks reproduce primarily on white-tailed deer. Female ticks engorge on deer, drop off, and lay 1,000-3,000 eggs. Without sufficient deer hosts, established tick populations cannot sustain themselves.
Ontario’s deer population has tripled since 1980 — from roughly 200,000 to 600,000+ — driven by reduced hunting pressure, agricultural land conversion, and milder winters. Suburbanization has also created ideal deer habitat: forest-edge fragments adjacent to lawns and gardens. Wherever deer establish in southern Ontario, sustained tick populations follow within 5-10 years.
Projection to 2050
PHAC modelling under multiple climate scenarios projects continued northward expansion of blacklegged tick range through at least 2050. By 2040, much of the Algoma and Sudbury districts are projected to support established tick populations. By 2050, the climate-suitable range for blacklegged ticks may extend as far north as James Bay coastline.
For Ontarians, this is not an abstract future concern. The Ontario you grew up in had tick-free summer trails. Your children’s Ontario will not. Adaptive precaution — daily tick checks, prevention behaviours, professional yard treatment in high-risk areas — is the new baseline.
Lyme Disease in Dogs (and Cats)
Ontario veterinarians have seen a corresponding rise in canine Lyme cases since 2015. Dogs are also primary tick taxis — they sweep ticks from grass and brush, then deposit them on furniture, beds, and humans during petting and play.
4DX Plus testing
Most Ontario veterinarians recommend annual 4DX Plus blood testing. The test screens dogs for exposure to four tick-borne diseases simultaneously: Lyme (Borrelia burgdorferi), Anaplasmosis, Ehrlichiosis, and heartworm. A positive 4DX result indicates exposure — not necessarily active disease — and prompts follow-up testing. Cost: typically $50-90 as part of an annual wellness exam.
Oral preventatives
NexGard (afoxolaner), Bravecto (fluralaner), and Simparica (sarolaner) are the gold standard for canine tick prevention in Ontario. They work systemically — when a tick bites a treated dog, the active ingredient kills the tick within 4-12 hours, before disease transmission can occur. NexGard is monthly; Bravecto is every 12 weeks. Topical preventatives (Frontline, Advantix) are less effective against blacklegged ticks specifically.
Lyme vaccine for dogs
A canine Lyme vaccine (Nobivac Lyme, RECOMBITEK Lyme) is available through Ontario veterinarians. Most vets recommend it for dogs in established endemic regions or dogs that frequently visit endemic areas (e.g., cottage dogs). It is not part of core vaccination but is increasingly common as endemic zones expand. Discuss with your vet.
Cats — different story
Cats appear naturally resistant to Lyme disease — confirmed feline Lyme cases are extremely rare even in highly endemic areas. However, outdoor cats can still carry ticks indoors and bring them into contact with humans and dogs. There is no canine-equivalent oral preventative for cats; consult your vet about appropriate options. Most veterinarians do not recommend Lyme vaccination for cats.
If your dog has had a confirmed tick bite or shows symptoms (lameness, joint swelling, lethargy, loss of appetite, fever), contact your veterinarian. Canine Lyme typically responds well to a 4-week course of doxycycline if caught early.
Sources & References
All data on this page is aggregated from publicly available government sources. Direct citations and links provided for transparency and verification. Last updated May 2026.
Public Health Ontario
Annual Lyme Disease Surveillance Reports + endemic area maps.
PHAC — Public Health Agency of Canada
National Lyme disease surveillance + tick range modelling.
eTick.ca
Free Canadian tick identification service. Bishop’s University & Université de Montréal.
CanLyme — Canadian Lyme Disease Foundation
Patient resources, Lyme-literate physician directory, advocacy.
Ontario Ministry of Health
Provincial Lyme disease information and prevention guidance.
Environment and Climate Change Canada
Climate normals, temperature trends, climate-vector projections.
Cited research
- • Ogden NH, et al. “Climate change and the potential for range expansion of the Lyme disease vector Ixodes scapularis in Canada.” International Journal for Parasitology (2008).
- • Bouchard C, et al. “The increasing risk of Lyme disease in Canada.” Canadian Veterinary Journal (2015).
- • Leighton PA, et al. “Predicting the speed of tick invasion: an empirical model of range expansion for the Lyme disease vector Ixodes scapularis in Canada.” Journal of Applied Ecology (2012).
- • Public Health Ontario. Lyme Disease in Ontario: Surveillance and Disease Trends, 2010-2024. Annual report series.
What you can do this week
Ontario’s Lyme expansion isn’t hypothetical — it’s measurable, ongoing, and accelerating. Here are the three highest-leverage things you can do for your household’s protection.
Step 1 · 60 seconds
Get your household Lyme risk score
Free 60-second assessment. Custom 1-100 score based on your address, yard features, dog walking habits, and family outdoor exposure.
Take the calculator →Step 2 · Free report
Free property tick risk report
Address-specific tick pressure assessment. Identifies high-risk yard features, neighbourhood factors, and barrier-spray priority zones.
Get my yard report →Step 3 · Pro treatment
Professional tick barrier spray
Health Canada-approved residual spray. Reduces yard tick populations 80-90% for 21-30 days. Five-spray season program from $497.
Tick control plans →BuzzSkito Mosquito & Tick Control · Mississauga, ON · serving the GTA
📞 (289) 216-5030 · ✉️ info@buzzskito.ca
This page provides educational information aggregated from public sources. It is not medical advice. For confirmed tick bites, suspected symptoms, or post-exposure prophylaxis questions, contact your family doctor, Telehealth Ontario (1-866-797-0000), or your local Public Health Unit.
Frequently asked questions
How many Lyme disease cases were reported in Ontario in 2025?▾
Public Health Ontario confirmed 3,614 Lyme disease cases in Ontario for 2025 — a 19% increase over 2024 (3,032 cases) and a 30-fold increase since 2010 (119 cases). The 2025 case rate is approximately 23 cases per 100,000 population, with the highest concentration in eastern Ontario PHUs (Kingston-Frontenac-Lennox-Addington, Eastern Ontario Health Unit, Leeds-Grenville-Lanark, and Hastings Prince Edward).
Which Ontario regions are Lyme-endemic in 2026?▾
Public Health Ontario currently classifies eight PHUs as established Lyme-endemic regions: Kingston-Frontenac-Lennox-Addington, Eastern Ontario Health Unit, Leeds-Grenville-Lanark, Hastings Prince Edward, Ottawa, Renfrew County, Peterborough, and Niagara Region. Seven additional PHUs are emerging (Halton, Simcoe-Muskoka, Haliburton-Kawartha-Pine Ridge, York Region, Lambton, Wellington-Dufferin-Guelph, Waterloo). Lyme cases have been confirmed in every Ontario PHU since 2022.
How long does a tick need to be attached to transmit Lyme disease?▾
Most CDC and Public Health Ontario guidance states blacklegged ticks (Ixodes scapularis) need to be attached for 24-36 hours minimum to transmit Borrelia burgdorferi (the bacterium that causes Lyme disease). The bacteria need time to migrate from the tick gut to its salivary glands. Daily tick checks within 24 hours of outdoor activity essentially eliminate Lyme transmission risk because most ticks haven't had time to transmit.
What does early-stage Lyme disease look like in Ontario?▾
The classic early sign is erythema migrans — an expanding bullseye rash that appears 3-30 days after a tick bite, most commonly 7-14 days. About 70-80% of confirmed Ontario Lyme cases present with this rash. Other early symptoms: fever, chills, fatigue, headache, muscle and joint aches, swollen lymph nodes. If you see a bullseye rash or develop unexplained flu-like symptoms after known tick exposure, see a doctor within 72 hours — early Lyme treats easily with 14-21 days of doxycycline.
Where can I submit a tick for identification in Ontario?▾
eTick.ca is the free public tick identification service operated by Bishop's University. Submit clear photos of the tick (top view + side view) through their website. Identification typically returns within 24 hours. eTick is integrated with Ontario's public health surveillance system. Several Public Health Units also accept physical tick samples — see the directory below for your local PHU's tick submission protocol. eTick is the fastest and most widely-recommended option.
Why is Lyme disease spreading in Ontario?▾
Three converging factors: (1) Climate change — milder winters allow more blacklegged ticks to survive year-over-year; the southern Ontario hard-frost line has shifted ~30 km north per decade since 1990. (2) Migratory birds — songbirds carry blacklegged ticks northward each spring, depositing them in new areas. (3) White-tailed deer population recovery — deer are the primary reproductive host for adult blacklegged ticks; Ontario's deer population has grown 200% since 1980. Combined, these factors have driven a 30-fold increase in confirmed Ontario Lyme cases since 2010.
What are the risks for dogs in Ontario?▾
Ontario veterinarians have reported a corresponding rise in canine Lyme cases since 2015. The 4DX Plus annual blood test (used by most Ontario vets) screens dogs for Lyme exposure plus three other tick-borne diseases (Anaplasma, Ehrlichia, heartworm). Oral preventatives (NexGard, Bravecto, Simparica) are the gold standard for tick prevention in dogs — they kill ticks within 4-12 hours of attachment, before disease transmission can occur. Topical preventatives (Frontline, Advantix) are less effective against blacklegged ticks.
Can I get Lyme disease in downtown Toronto or Mississauga?▾
Yes — though the risk is lower than in eastern Ontario. Cases have been confirmed annually in Toronto, Mississauga, Brampton, and other GTA cities since 2022. Higher-risk GTA zones include Rouge National Urban Park (eastern Toronto/Markham), Don Valley ravine system, High Park, Toronto Islands, and the Caledon Hills (Oak Ridges Moraine). Migratory bird corridors deposit infected ticks in unexpected urban locations every spring. Daily tick checks after any outdoor activity in the GTA — including dog walks in city parks — are recommended.
Is this tracker a substitute for medical advice?▾
No. This tracker provides educational information about tick-borne disease epidemiology and prevention in Ontario. It is not diagnostic. If you have a confirmed tick bite, a bullseye rash, or unexplained symptoms after potential tick exposure, contact your family doctor, Telehealth Ontario (1-866-797-0000), or your local Public Health Unit. In emergencies (facial drooping, irregular heartbeat, severe headache with neck stiffness), go to an Emergency Room.