Ontario Lyme Disease
Data & Tick Directory

Ontario reported 2,369 confirmed and probable Lyme disease cases in 2024, according to the Public Health Agency of Canada’s Health Infobase annual tick-borne disease report. That is a 27% increase over the 1,859 cases reported in 2023, and it represents 41% of Canada’s national total of 5,809 cases. 2024 is the most recent year for which a final provincial figure has been published.

No. As of July 2026, neither Public Health Ontario nor the Public Health Agency of Canada had published a final 2025 Lyme disease case count for Ontario. The latest published provincial year is 2024. Public Health Ontario’s Vector-Borne Disease Tool does publish weekly year-to-date counts during the season, but those are provisional and are revised as cases are investigated and classified — they are not a substitute for a finalised annual figure. If you see a 2025 Ontario total quoted anywhere, check whether it traces back to one of those two agencies.

Public Health Ontario maps blacklegged tick risk areas through its Ontario Vector-Borne Disease Tool, and those risk areas are drawn as geographic areas rather than along public health unit boundaries — a single health unit can contain risk areas and non-risk areas at the same time. The 2026 map reflects newly identified or expanded risk areas based on 2025 field data. Because the boundaries move every year and do not follow municipal lines, the honest answer is to check the current map for your own address rather than rely on any third-party regional ranking, including ours. BuzzSkito does not publish a regional risk ranking of its own.

Standard public health guidance in Canada and the United States is that blacklegged ticks (Ixodes scapularis) generally need to be attached for at least 24 to 36 hours to transmit Borrelia burgdorferi, the bacterium that causes Lyme disease. The bacteria need time to migrate from the tick gut to its salivary glands. Doing a full tick check within 24 hours of outdoor activity, and removing anything you find, greatly reduces the chance of transmission.

The classic early sign is erythema migrans — an expanding rash, often but not always with a bullseye pattern, appearing 3 to 30 days after a tick bite and most commonly at 7 to 14 days. In the Canadian Lyme Disease Enhanced Surveillance data for 2009–2019, a single erythema migrans rash was the most frequently reported clinical manifestation, present in 76.4% of cases. Other early symptoms include fever, chills, fatigue, headache, muscle and joint aches, and swollen lymph nodes. If you see an expanding rash or develop unexplained flu-like symptoms after possible tick exposure, see a doctor promptly — early Lyme responds well to a 14 to 21 day course of doxycycline.

eTick.ca is the free public tick identification platform operated by Bishop’s University and the Université de Montréal. You submit clear photos of the tick — one from the top and one from the side — through the website, and trained identifiers return a species identification, usually within about a day. Several Ontario public health units also field tick questions directly; the directory further down this page lists phone numbers and the health unit contact for each one.

Two mechanisms are well documented in the peer-reviewed literature. First, temperature: blacklegged tick populations need enough accumulated warmth to complete their life cycle, and the published models use cumulative annual degree-days above 0°C rather than a single winter-cold threshold. Below roughly 2,800 degree-days above 0°C, Ixodes scapularis populations cannot establish or persist (Ghanbari et al., PLOS One 2025, citing Ogden et al. 2005). As accumulated degree-days rise, areas that were previously unsuitable become suitable. Second, dispersal: migratory songbirds carry tick larvae and nymphs north each spring — Ogden and colleagues estimated 50 to 175 million Ixodes scapularis ticks are dispersed into Canada annually by migratory birds (Applied and Environmental Microbiology, 2008). Together these mean ticks are constantly being seeded into new areas, and a growing share of those areas can now support them year-round.

Ontario veterinarians commonly recommend annual 4DX Plus blood testing, which screens dogs for exposure to Lyme (Borrelia burgdorferi), Anaplasma, Ehrlichia and heartworm in a single test. Oral preventatives (NexGard, Bravecto, Simparica) work systemically and kill ticks shortly after they bite a treated dog; topical products are generally considered less effective against blacklegged ticks. A canine Lyme vaccine is available in Ontario and is usually discussed for dogs that spend time in areas where blacklegged ticks are established. Talk to your veterinarian about what is appropriate for your dog.

Yes. Blacklegged ticks are present in parts of southern Ontario including the Greater Toronto Area, and migratory birds deposit ticks well outside established populations every spring. Rather than relying on a general statement about a city, check Public Health Ontario’s Vector-Borne Disease Tool risk-area map for your own area, and do a tick check after any outdoor activity — including dog walks in city parks and ravines.

No. This page provides educational information about tick-borne disease surveillance and prevention in Ontario. It is not diagnostic. If you have a confirmed tick bite, an expanding rash, or unexplained symptoms after potential tick exposure, contact your family doctor, Health811 / 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.