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Lyme disease

What is Lyme disease?

Lyme disease is a tick-transmitted disease of people and animals caused by a microscopic bacteria called Borrelia burgdorferi. In nature, Lyme disease is most often associated with small mammals such as white-footed mice, deer mice, and birds or with large animals such as deer. In people, the symptoms of this illness vary greatly. As a result, this disease is often called "the great imitator" because patients can be misdiagnosed. The infection often starts out as a skin rash with or without flu-like symptoms and can progress to arthritic, cardiac or neurologic disease.

Diagram courtesy of the Center for Disease Control

How do ticks transmit Lyme disease?

Blacklegged ticks, also known as deer ticks, are the only type of tick in Ontario that can consistently transmit Lyme disease. Blacklegged ticks are often no bigger than a pin head, and their bite is painless, so many victims of Lyme disease are unaware they are at risk. Ticks feed on blood by inserting their mouthparts (not their whole bodies) into the skin of a person or an animal. Ticks feed slowly, and their body gradually enlarges as it consumes blood, making it more visible. It takes anywhere from 3 to 7 days for a blacklegged tick to take a complete blood meal.

Even after a bite from an infected tick, there is only a small chance of getting Lyme disease. Ticks are most likely to transmit infection after being attached to the skin for more than 24 hours because the Lyme disease bacteria needs time to migrate from the tick's gut to its salivary glands. This delay means prompt detection and removal of ticks are key to preventing Lyme disease.

If a blacklegged tick has Lyme disease and it is removed quickly from the body, it is very unlikely that it has transmitted Lyme disease to the human host. People who are bitten by a tick and who develop symptoms of infection should see their doctor.

Where are ticks found in Ontario?

Ticks can be found on tall grass and brush in wooded areas.

Blacklegged ticks can be found throughout Ontario, but are especially common in locations like:

  • Along the north shores of Lake Erie
  • Lake Ontario
  • Along the St. Lawrence River

Ontario Lyme Disease Map 2017 - Estimated Risk Areas

Blacklegged ticks are also known to feed on migrating birds, and as a result, are transported throughout the province. Therefore, while the potential is low, it is possible for people to encounter blacklegged ticks, and to be infected with Lyme disease, almost anywhere in the province.

Portions of this section have been adapted from Ontario Ministry of Health and Long Term Care.


The classic symptom of Lyme disease is a skin rash that occurs at the location of the tick bitewithin 3 to 30 days. Days to weeks following a tick bite, 80% of infected people develop a red, slowly expanding "bull's-eye" rash (erythema migrans) around or near the site of the bite. If left untreated the rash will disappear within 3 weeks.

Flu-like symptoms may also occur at this stage of the disease. These symptoms include a headache, chills, joint pain, loss of appetite, nausea, fatigue, fever, aching muscles, stiff neck, sore throat, and vomiting. If left untreated these symptoms will also disappear within 10 days.

The later stages of Lyme disease can involve arthritic, cardiac and neurological complications. These can occur weeks, months or even years after the initial symptoms have disappeared.


Antibiotic treatment is generally effective in the early stages of the disease. Individuals who are bitten by a blacklegged tick should remove the tick promptly, thoroughly clean the bite area and their hands with alcohol based hand rub or soap and water and have the tick tested for Lyme disease. Oxford County Public Health will submit the tick to the Public Health Laboratoryfor analysis. Medical attention should be sought if any symptoms of early Lyme disease develop over the next month. It is possible to get re-infected after being treated for Lyme disease.

How to submit a tick for testing, follow these steps:

  1. Put a paper towel in an airtight plastic container. The container should be big enough to hold the tick without damaging it. Also make sure the container has a top that fastens securely (for example, pill bottle).

2. Transfer the tick to the container using tweezers, gloves or other protection.

3. Label the container with the following information:

  • your name
  • location and date the tick was collected
  • Note: we only submit ticks that were attached to human hosts. Ticks that were attached to a dog or cat will not be accepted at the health unit. Please consult your vet regarding ticks from domestic pets.

4. If you cannot submit the tick immediately, you can store in in a container for up to 10 days. Store live ticks in the refrigerator and dead ticks in the freezer.

5. All tick submissions should be directed to:

Southwestern Public Health
410 Buller Street, Woodstock, ON N4S 4N2
519-421-9901 or 1-800-922-0096 ext. 3500