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What is Lyme disease?

Lyme disease is an infection caused by the corkscrew-shaped bacteria, Borrelia burgdorferi. These bacteria are spread by the bite of blacklegged ticks (formerly called deer ticks), Ixodes scapularis. The blacklegged tick can be found sporadically throughout Ontario.

How do ticks transmit Lyme disease?

Blacklegged ticks are the only type of tick in Ontario that can consistently transmit Lyme disease. Even with a bite from an infected blacklegged tick, there is only a small chance of getting Lyme disease. 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 feeds, making it more visible. Ticks are most likely to transmit infection after being attached for more than 24 hours of feeding because the bacteria requires time to migrate from the tick’s gut to its salivary glands. Because of this delay, prompt detection and removal of ticks is one of the key methods of 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 transferred Lyme disease to the human host. People who are bitten by a tick and who develop symptoms of infection should see their doctor.

What are the symptoms of Lyme disease?

Early symptoms of Lyme disease usually occurs within one to two weeks, but can occur as soon as three days or as long as a month, after a tick bite. If you develop fever, headache, muscle and joint pains, fatigue and a skin rash, especially one that looks like a red bull's eye (called erythema migrans), promptly seek medical advice. It is important to tell your doctor when and the geographical location of where you were bitten by a tick. Not all patients with Lyme disease will develop the bull’s eye rash.

How is Lyme disease treated?

In most circumstances in Ontario, antibiotic treatment is not necessary if someone has been bitten by a tick. If a tick is discovered attached to a person, the tick should be promptly removed. The tick can be identified through a doctor and/or public health unit. If the tick is a blacklegged tick, it will be tested for Lyme disease. Medical attention should be sought if any symptoms of early Lyme disease develop within 30 days of removal of the tick. In rare instances, antibiotic treatment may be recommended if the tick was attached for a long time (more than 24 hours), the person had been visiting an area where Lyme disease is relatively common, or the tick is not available for testing and the patient has symptoms of early Lyme disease. If symptoms of Lyme disease develop, antibiotics should prevent further complications. The earlier treatment is received, the better. If the initial infection is not treated, symptoms involving the heart, nervous system or joints can occur.

Lyme disease testing

Blood tests to support a diagnosis of Lyme disease are performed at the Ontario Public Health Laboratory. The diagnostic tests that are used are approved by federal regulators in Health Canada. The testing protocol follows the recommendations of the Canadian Public Health Laboratory Network as well as the Centers for Disease Control (CDC) in the USA. The CDC and the Public Health Agency of Canada caution health care professionals and the public regarding the use of private laboratories offering Lyme disease testing in the USA, as these “for-profit” laboratories may not follow the same testing protocols as most Canadian provincial and federal or United States federal or state laboratories.

This fact sheet provides basic information only. It must not take the place of medical advice, diagnosis or treatment. Always talk to a health care professional about any health concerns you have, and before you make any changes to your diet, lifestyle or treatment. 

Source: Ontario Ministry of Health & Long-term Care