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Infectious Diseases

Lyme Disease

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What is Lyme disease?

Lyme disease is a bacterial infection transmitted from infected blacklegged ticks (also known as deer ticks) to humans.  Tick bites are usually painless and most people do not know that they have been bitten.  Lyme disease has become a common problem in parts of U.S. and can also be acquired in certain parts of Canada.

How is it spread?

Not all ticks carry Lyme disease.  Even with a bite from an infected tick, there is only a small chance of getting Lyme disease.  Ticks feed on blood by inserting their mouth (not their whole bodies) into the skin of a person or an animal.  They are slow feeders so it takes time before the bacteria can be transmitted to your blood.  Ticks are most likely to transmit infection after being attached for more than one day of feeding.  A complete blood meal can take several days.

What are the symptoms?

After a tick bite 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.  Symptoms can be different from person to person.  Some may not have any symptoms and others may suffer severe symptoms.  Seek medical advice if you develop these symptoms:  fever, headache, muscle and joint pains, fatigue and a skin rash, especially one that looks like a red bull's eye (called erythema migrans).

It is very important to tell your doctor when and where you were bitten by a tick. 

What is the treatment for Lyme disease?

People should seek medical attention if symptoms develop within 30 days of suspected tick exposure.  If a physician assesses someone to have Lyme disease within a month of the tick exposure they will prescribe an antibiotic.  If treated early with appropriate antibiotics, patients can expect to make a full recovery.

If the initial infection is not treated, then infection can become difficult to treat and patients may experience joint, heart and neurological symptoms.

In most circumstances in Ontario, antibiotic treatment is not necessary if someone has been bitten by a tick.  A person who is bitten should remove the tick and have the tick tested through the local public health unit.  The tick will be sent for identification and Lyme bacteria testing (black-legged ticks only species tested).

How do I protect myself and others?

  • Check yourself after every two to three hours of outdoor activity for ticks attached to clothing or skin.
  • Wear light-coloured clothing and tuck pants into socks and shirts into pants to minimize exposure to ticks.
  • Applying repellents containing (DEET) to skin or clothing.
  • Put a tick and flea collar on your pet and check for ticks periodically.CDC/ James Gathany

For symptoms common with Lyme disease see the Government of Canada’s information.

For treatment options with Lyme disease see the Government of Canada's information.

For information on prevention tips, how to remove a blacklegged tick or to submit a tick for testing see our Lyme and Blacklegged Ticks page.


 For data on the incidence of Lyme disease in Simcoe Muskoka and Ontario, please visit the Lyme disease page on the health unit’s HealthSTATS site 

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