Lyme disease is an illness caused by a bacterium called Borrelia burgdorferi, which is transmitted by the bite of an infected tick. It is the most common tick-borne infection in Canada. The bacterium is usually carried by birds, mice, squirrels, and other small animals. Ticks become infected by the bacterium when they feed on infected animals. The bacterium can be passed to humans when they get bitten by an infected tick. Under normal circumstances, Lyme disease cannot be passed from human to human, by other animals, or through food. Pets (cats and dogs) can get Lyme disease, but they don't appear to pass it onto humans. However, they can bring infected ticks into the home.
You may come into contact with a tick simply by brushing against vegetation. The risk of contact increases between early spring and late fall. The winter months don't always offer protection from ticks if the temperature is 4°C (39°F) or more and there is no snow. The tick bite does not hurt or sting; you probably won’t notice it. Not all ticks carry Lyme disease, and the chance of getting Lyme disease from an infected tick is greatly reduced by removing ticks within 24 to 36 hours of attachment.
Lyme disease is passed to humans through the bite of certain types of ticks that are infected with a bacterium called Borrelia burgdorferi. Ticks are about the size of a sesame seed (3 mm to 5 mm in length), red and brown in colour, and feed on blood. As the tick feeds on blood, its body can swell up to 8 times its original size. In Canada, there are 2 major species of ticks that are known to transmit Lyme disease:
- the deer tick (blacklegged tick), which has been found to be established in parts of southern and eastern Ontario, southeastern Quebec, southeastern and south-central Manitoba, and parts of Nova Scotia and New Brunswick, and has been taken off humans and pets in other areas where the tick is not currently known to be established
- the western blacklegged tick, which can be found in parts of southern British Columbia
Ticks can also be carried by migratory birds to other parts of Canada.
Symptoms of Lyme disease can appear as early as 3 days and as late as 30 days after a tick bite, so it may be hard to tell if it was contracted locally. A travel history is important.
Symptoms and Complications
The symptoms of Lyme disease can often be described as occurring in 3 stages, although not all infected individuals experience all 3 stages.
Early Localized Lyme Disease
The classic and often first symptom of Lyme disease is a skin rash called erythema migrans (EM), which occurs in up to 80% of infected people. This characteristic skin rash can appear as early as 3 days following a tick bite, but may sometimes take up to a month to appear. The rash usually begins at the site of the bite and often forms a "bull's-eye" pattern. The centre may continue to darken or become warm to the touch. Some of the symptoms of Lyme disease are common to other medical conditions including fatigue, headache, chills and fever, muscle and joint pain, and swollen lymph nodes. Without treatment, EM will usually fade within 4 weeks. If the initial symptoms of Lyme disease go untreated, the next stage of the disease can persist for several months.
Early Disseminated Lyme Disease
During this stage, bacteria spread through the blood to other areas of the body, where they can cause tissue inflammation. Symptoms that may occur in the second stage of the disease include extreme weakness or tiredness, severe joint pain and stiffness, headaches, facial weakness, eye irritation, skin rashes, and irregular heartbeat. Without the presence of EM, these symptoms do not always lead to the diagnosis of Lyme disease. If the disease continues to progress, it will enter a third stage.
Late Lyme Disease
Symptoms of this stage can include long-term arthritis and neurological symptoms that include headache, dizziness, numbness, changes in ability to think clearly, heart problems, and even paralysis. This stage of the disease may last several months or years. Fatalities from Lyme disease are rarely documented. However, Lyme disease can be potentially fatal to an unborn baby if the disease is contracted during pregnancy.
Making the Diagnosis
A diagnosis of Lyme disease is based on the doctor's evaluation of symptoms and on recent exposure to ticks and tick-infested areas. The presence of EM is especially useful for diagnosis in the early stages. Blood tests may be used to detect the presence of antibodies to the bacteria (these antibodies may not appear for up to 2 to 6 weeks after the infection). The doctor will also gather other clinical information, such as medical history.
Treatment and Prevention
In general, routine use of antibiotics to prevent Lyme disease following tick exposure is not recommended. However, antibiotics such as doxycycline*, amoxicillin, cefuroxime, and ceftriaxone can be used to treat
Lyme disease if an infection develops. If you notice symptoms of Lyme disease, see your doctor for treatment.
For people who require treatment for a mild infection associated with Lyme disease, the doctor usually prescribes an oral antibiotic for 2 to 4 weeks to cure the infection.
For people who require treatment for more severe infections associated with Lyme disease (such as people with neurological or cardiac symptoms), the doctor usually prescribes an intravenous (given through the vein) antibiotic. For persistent infections, a longer course of treatment may be necessary. Lyme disease is easier to treat when treatment is started earlier in the disease.
You can help prevent Lyme disease if you know what to look for. The tick digs its mouth into the skin and feeds for several days before dropping off. The bite causes no local symptoms. If you spend time in the woods, you should wear long pants, socks, a hat, and a long-sleeved shirt to reduce the chances of tick bites. As an extra precaution, tuck your pants into your socks or put tape around the area where your pants and socks meet.
Permethrin sprayed on clothing kills ticks, and commercial sprays are readily available. Other tick repellants include DEET, oil of lemon, eucalyptus, and picaridin (icaridin).
Once you get back indoors, inspect yourself carefully for ticks. If you spend several days outdoors in areas that might contain ticks, inspect yourself daily. Check your skin carefully for ticks, and ask someone to check your scalp for ticks. If a tick has already latched on to you, don't panic. Ticks are less likely to transmit the infection if they've been attached for less than one day. This is because they need to feed for 24 hours to help the bacteria grow inside their own bodies to the point where it can cause infection.
The following are some other things you can do:
- If possible, stay away from tick-infested areas.
- Stay in the middle of hiking trails and try not to brush against grasses or leaves.
- Avoid wearing sandals and open-toed shoes. Wear shoes that cover the entire foot, and cover as much of your body with clothing as is practical.
- Wear light-coloured clothes to make it easy to spot ticks "hitching a ride" on you.
- Spray your clothes and exposed skin (except your face) with an insect repellent that contains DEET, oil of lemon, eucalyptus, pircaridin, or permethrin.
- Check your pets for ticks on a regular basis.
To remove a tick from the skin, use tweezers to hold the tick by the head as close to the skin as possible and pull slowly but firmly. Avoid twisting or crushing the tick when you are removing it. Do not squeeze the tick's body, as this may speed up infection.
Do not apply petroleum jelly or alcohol, or use a hot match, nail polish, or other products and home remedies to remove a tick.
After you've carefully removed the tick, cleanse the area with an antiseptic (e.g., alcohol) or mild soap and water. Wash your hands thoroughly with soap and water. You should also have tick bites examined by a doctor, especially if you develop a rash or experience flu-like symptoms.
If possible, try to save the tick by placing it in a small vial or zip-lock bag (use a double bag). The tick can be sent to a lab for further investigation, which may help in diagnosing your illness if symptoms develop.
Place a wet paper towel in the vial or bag with the tick to prevent it from drying out, since dried out ticks are harder to identify.