Tick-borne Diseases
Learn about local risk factors for Lyme disease, anaplasmosis and more.
Ticks are becoming more common across Ontario. Warmer temperatures, fewer winter die-offs, and longer warm seasons allow ticks to thrive, expand into regions where they were once uncommon, and remain active for more of the year. As tick populations continue to grow and spread northward, the chance of encountering a tick—and the risk of tick-borne diseases—is increasing across Ontario and Canada.
As of 2025, blacklegged ticks are established throughout the WDG region, especially in Puslinch, the City of Guelph and the Town of Mono.
Learn more:
• Increased Risk of Tick-Borne Diseases with Climate Change (PDF)
• Managing Tick-Related Risks in Outdoor Environments
Tick Species in WDG
Blacklegged ticks (Ixodes scapularis)
- Found across WDG as of 2025.
- Can carry Lyme disease and other infections (anaplasmosis, babesiosis, Powassan virus).
- Not every tick is infected.
American dog ticks (Dermacentor variabilis)
- Very common in WDG.
- Do not spread Lyme disease.
- Can carry tularemia or Rocky Mountain spotted fever, but these have not been reported in WDG.
Check out our Zoonotic Vector-Borne Diseases Dashboard (ZVBD) to explore the surveillance data on local ticks.
Tick-Borne Diseases in Ontario
Your risk of getting a tick-borne disease is low, but you can make it even lower by:
- Staying on marked trails
- Doing tick checks after outdoor activities
- Removing ticks promptly
Below are the tick-borne diseases present in Ontario and what we know about them in WDG.
Detected in WDG.
Lyme disease is an illness transmitted through the bite of an infected blacklegged tick carrying Borrelia burgdorferi. Early infection causes flu-like symptoms and may include a bull’s-eye rash. If untreated, it can affect the joints, heart, and nervous system.
Blacklegged ticks are established throughout Wellington-Dufferin-Guelph.
Symptoms may begin 3 to 30 days after a tick bite and can include:
- Fever and chills
- Headache
- Fatigue
- Muscle and joint aches
- Bull’s-eye rash (not always present)
Early Lyme disease is usually treatable with antibiotics. If you find a tick on you or have symptoms, contact your health care provider.
A blacklegged tick generally needs to be attached and feeding for at least 24 hours to transmit Lyme disease.
If you find a tick on you or have symptoms, contact your health care provider.
Learn more: Ontario Lyme Disease Risk Map (2025)
No cases linked to tick bites acquired in WDG.
Anaplasmosis is a bacterial infection caused by Anaplasma phagocytophilum and spread by infected blacklegged ticks. Most infections cause flu-like illness and are treatable with antibiotics.
It became a reportable disease in Ontario in 2023. That year, 40 cases were reported—all in Eastern Ontario.
Symptoms usually begin within 1 to 2 weeks of a tick bite and may include:
- Fever
- Headache
- Chills
- Muscle aches
- Nausea
- Cough (sometimes)
Anaplasmosis is treated with antibiotics.
Contact your health care provider if you develop symptoms after a tick bite.
Not detected in WDG.
Babesiosis is a parasitic infection spread by the bite of an infected blacklegged tick. Many people do not develop symptoms, but others may experience flu-like illness. More severe illness can occur in older adults or people with weakened immune systems.
Babesiosis became reportable in Ontario in 2023; Ontario recorded 15 probable and confirmed cases.
Symptoms can begin 1 to 9 weeks after a tick bite and may include:
- Fever
- Chills
- Sweats
- Fatigue
- Muscle aches
- Nausea
Treatment usually involves antibiotics. Seek medical attention if you develop symptoms after a recent tick bite.
Not detected in WDG.
Powassan virus is a rare infection spread by blacklegged ticks and groundhog ticks. Most infections cause no symptoms, but severe cases can affect the brain or the tissues surrounding it.
Powassan virus became reportable in Ontario in 2023; 21 cases have been reported in Ontario since 2017.
Symptoms typically appear 1 week to 1 month after a tick bite and may include:
- Fever
- Headache
- Vomiting
- Weakness
- Confusion
- Seizures (in severe cases)
There is no specific treatment for Powassan virus, so avoiding tick bites is the best protection. Seek medical care right away if you develop symptoms after a tick bite.
Other Tick-Borne Diseases (Very Low or No Risk in Ontario)
These diseases are rare or have never been reported in Ontario. They may become more relevant in the future due to climate change, land-use changes and animal migration.
Learn more: A Review of Ticks in Canada and Health Risks from Exposure (NCCEH)
Not reported in WDG.
Alpha-gal syndrome is a rare allergic reaction triggered after a lone star tick bite. The tick can inject alpha-gal, a sugar molecule found in red meat (beef, pork, lamb). Some people then develop an allergy to red meat or meat products.
Lone star ticks are not established in Ontario.
Symptoms usually begin several hours after eating red meat, and may include:
- Hives or rash
- Stomach pain or nausea
- Trouble breathing
- Swelling of the lips, tongue, or throat (rare)
Symptoms are managed with avoidance of trigger foods.
Seek emergency care for any severe allergic reaction.
Not reported in WDG.
Ehrlichiosis is caused by Ehrlichia bacteria. It can be spread by lone star ticks or blacklegged ticks, though lone star ticks are the primary source. Most human infections in North America are spread by the lone star tick, which is not established in Ontario.
Symptoms often begin within 1–2 weeks after a tick bite:
- Fever and chills
- Headache
- Muscle aches
- Nausea
- Rash (less common)
Treated with antibiotics (usually doxycycline). Early treatment helps prevent complications.
Note for pet owners: Ehrlichiosis can also occur in dogs. Infection risk may increase if lone star ticks become established in the future.
Not reported in WDG.
Spread by the American dog tick, which is common in WDG, but Rocky Mountain spotted fever is extremely rare in Canada and more common in the United States. Infections have been linked to travel—especially the Long Point region of southwestern Ontario.
RMSF is caused by Rickettsia rickettsii. It is a serious bacterial infection that can progress quickly.
Symptoms usually appear 2–14 days after a tick bite:
- Fever
- Headache
- Muscle aches
- Nausea or vomiting
- Rash (often starting on wrists and ankles)
- Belly pain
- Confusion
- Bleeding problems or severe complications (in advanced cases)
Severe illness can occur without prompt treatment of antibiotics.
For dog owners: A small number of RMSF cases have been reported in dogs after exposure to ticks in the Long Point region. Contact a veterinarian if your dog shows fever, lethargy, loss of appetite or joint pain after a tick bite.
Not reported in WDG.
Extremely rare in Ontario—only 4 cases reported since 2014. Tularemia is caused by Francisella tularensis. It can be spread by various insects including:
- Ticks (lone star, American dog tick, Rocky Mountain wood tick)
- Mosquitoes
- Deer flies and horse flies
Symptoms vary but often include:
- Fever
- Chills
- Headache
- Skin ulcers at the bite site
- Swollen lymph nodes
Treated with antibiotics. Most people recover fully with prompt care.