Lyme disease is an illness spread through the bite of a blacklegged tick, also known as a deer tick, that is infected with the Borrelia burgdorferi bacteria. Not all ticks are infected with the bacteria, so not all tick bites spread Lyme disease. The risk of getting Lyme disease from a tick bite increases with the time a tick is attached to a person and usually requires the tick to be attached for 24 hours or more. Lyme disease does not spread from person to person.
Early symptoms of Lyme disease usually occur within one to two weeks, but can occur as soon as three days, or as long as a month after a tick bite.
Initial symptoms differ from person to person, which makes Lyme disease very difficult to diagnose. Some people may have no symptoms at all. Others may suffer severe symptoms, but not for weeks after the bite and may not associate the illness with the bite. The sooner you get treatment, the sooner you can begin recovery.
Signs of Lyme disease can include one or a combination of the following symptoms with varying degrees of severity:
- Fever or chills
- Spasms, or weakness
- Numbness or tingling
- Swollen lymph nodes
- Skin rash around the tick bite
- Cognitive dysfunction (brain fog) or dizziness
- Temporary paralysis or weakness on one side of the face
- Abnormal heartbeat
If left untreated, symptoms can last for months or years and may include recurring arthritis (muscle and joint pain), nervous system and/or neurological problems, numbness and/or paralysis. If Lyme disease is diagnosed in its early stages, it can be treated effectively with antibiotics.
Source: Public Health Agency of Canada
What to do if you become are bitten by a blacklegged tick
If a blacklegged tick was attached for 24 hours or more, your pharmacist or physician may prescribe an antibiotic to prevent Lyme disease. The antibiotic must be taken within 72 hours from when the tick was removed.
See your health care professional right away if you develop symptoms of Lyme disease in the weeks after a tick bite.
Lyme disease Information for Health Care Providers
Other Tick-borne Diseases
As of July 1, 2023, the Ontario Ministry of Health announced three new tick-borne Diseases of Public Health Significance. Anaplasmosis, Babesiosis and Powassan Virus are spread through the bite of an infected blacklegged tick.
Anaplasmosis is a bacterial infection transmitted through the bite of an infected blacklegged tick. Most human exposures occur in areas known to have infected blacklegged ticks. Symptoms may include fever, chills, severe headache, myalgia, abdominal pain, nausea, vomiting, diarrhea and/or loss of appetite.
Babesiosis is a parasitic infection transmitted through the bite of an infected blacklegged tick. Most infections are asymptomatic; however, infected individuals may develop mild to severe systemic symptoms such as fever, chills, sweats, headache, body aches, loss of appetite, nausea or fatigue. Babesiosis may also cause a type of anemia called hemolytic anemia, with symptoms including fatigue, jaundice and dark urine. Other severe symptoms include low platelets and renal failure.
Powassan virus disease is a rare infection transmitted through the bite of an infected blacklegged tick, or less commonly the groundhog tick or squirrel tick. Most people who become infected are asymptomatic; however, infected individuals may show mild to severe symptoms such as fever, headache, nausea, vomiting, weakness or muscle and joint pain. Severe disease may result in meningitis and/or encephalitis with symptoms that may include confusion, loss of coordination, difficulty speaking, paralysis, seizures or coma.
Source: Public Health Ontario
- Be sure to take precautions when outside, especially in areas where blacklegged ticks are commonly found
- Use insect repellent containing DEET or icaridin when outside and apply it according to the manufacturer’s instructions
- Cover up exposed skin when you go outside by wearing long-sleeved shirts or jackets, long pants and socks
- Search your body for ticks after spending time outdoors
- Remove attached ticks from your body as soon as possible
- Pay special attention to the following body areas:
- Underarm areas
- It is also important to check your pets regularly for ticks. Although they cannot spread Lyme disease, dogs and cats can bring infected ticks into your home
- Permethrin-treated clothing may provide protection against ticks and mosquitoes
Removing a Tick
To remove the tick:
- Grasp the tick with a set of tweezers as close to the skin as possible
- Slowly pull the tick straight out until it is removed
- Do not squeeze the tick
- Do not put anything on the tick or try to burn it off
- After removing the tick, thoroughly cleanse the bite site with rubbing alcohol and/or soap and water
- Visit www.etick.ca for free tick identification
- Consult with your physician if the tick has been attached for more than 24 hours or you are feeling unwell in the weeks following a tick bite or being in a natural area
For your convenience, we encourage you to visit www.etick.ca to submit a picture of a tick for free identification. Ticks removed from both animals and humans can be submitted to see if it is a blacklegged tick, the species that can carry the Lyme disease bacteria.
Please note this service is for identification of the tick only. For concerns about Lyme disease transmission, please contact your health care professional or speak to your veterinarian if you find a tick on your pet.
All of York Region is now considered an estimated Lyme disease risk area. Tick testing is no longer required for surveillance.
Where are blacklegged ticks found in Ontario?
The risk for exposure is highest in regions where ticks infected with the bacteria that cause Lyme disease are known to be established. This includes areas along the north shores of Lake Erie, Lake Ontario and the St. Lawrence River. Surveillance efforts have identified blacklegged ticks throughout York Region and much of the Greater Toronto Area. Some of those ticks have tested positive for the bacteria that causes Lyme disease.
Blacklegged ticks can be transported by birds or other wildlife across regions. There is a chance of being exposed to Lyme disease through contact with infected ticks almost anywhere in Ontario. Take precautions against ticks when visiting any woodland habitats where ticks may be present.
Public Health Ontario Lyme Disease Map
All of York Region is now considered an estimated Lyme Disease Risk Area.
Updated on a yearly basis, the map of estimated Lyme disease risk areas has been developed to assist clinicians in the diagnosis and/or treatment of Lyme disease, with potential exposures or tick bites in the risk areas delineated on the map leading to greater concern about the risks of Lyme disease. Risk areas are represented on the map based on tick testing.
- Public Health Ontario: Lyme disease information for residents, physicians and health units
- Ontario Ministry of Health and Long-Term Care: Lyme disease for Health Care Providers
- Health Canada: Safety tips, maps and statistics related to Lyme disease
- Lyme Disease and Other Tick-borne Diseases
- US Centres for Disease Control: Repellents and helpful tips on protecting yourself from tick bites
- The Clinical Assessment, Treatment, and Prevention of Lyme Disease, Human Granulocytic Anaplasmosis, and Babesiosis: Clinical Practice Guidelines by the Infectious Diseases Society of America
- Tick Encounter Resource Centre: Information on tick identification