Lyme disease is named after the small town in Connecticut where an explosion of rheumatoid arthritis cases was observed in hundreds of children in 1975. It was only seven years later when it was confirmed that these cases were due to a bacterium – Borrelia burgdorferi – transmitted by a single species of tick: the black-legged tick, also known as the deer tick.
Areas most affected
The black-legged tick is found in areas with an abundance of white-tailed deer and white-footed mice, the two main reservoirs of B. burgdorferi. Global warming has largely contributed to the expansion of this tick’s territory, which has spread to Ontario and Quebec, mostly in the Montérégie and Estrie regions. Infected ticks have also been found in neighbouring regions such as Centre-du-Québec and southwestern Outaouais. Since these ticks can be carried by birds, the risk of contracting Lyme disease, which is currently rather low in other regions, will increase over time.
Black-legged ticks are most active in the summer (June, July and August), although they can also infect people in other months when there is no snow on the ground, namely April, May, September, October, November and December.
About 20% to 25% of black-legged ticks are infected with B. burgdorferi. Therefore, not all bites from this tick will cause Lyme disease. In addition, for the bacterium to infect the human body, the tick must remain on the skin for more than 24 hours.
A serious illness
Some people will experience only very mild symptoms – or none at all – following an infection with the bacterium. But for others, the situation will be more worrisome.
The most visible sign of an infection is redness on the skin, which grows day by day to reach a diameter of more than 5 cm. Called “erythema migrans,” this rash often takes the form of a bull’s-eye. It
appears three to twenty days after a bite and is often accompanied by flu-like symptoms such as fever, fatigue, headaches, or muscle and joint pain.
If the infection is not treated, the consequences can be serious. In the weeks and months that follow, it could lead to paralysis of the facial nerves (Bell’s palsy), pain and numbness in the limbs, stiffness in the neck, headaches, heart rhythm disturbances and joint pain. After several years, some people develop chronic damage to their major joints.
According to some health care professionals and observations made in several individuals, there is also another chronic form of Lyme disease. This form could manifest itself several years after infection and result in chronic fatigue and muscle and joint pain. Although medical authorities recognize the existence of a post-treatment syndrome of Lyme disease in many people, the existence of a chronic form of the disease is the subject of much controversy. This debate is fuelled by the current difficulty in reliably detecting traces of the bacterium after several years and by the dangerous nature of the treatment, which involves administering a very powerful antibiotic, doxycycline, for several months.
In the vast majority of cases (80%), the presence of an erythema migrans leads to a diagnosis of Lyme disease during the period of a few days to three weeks after infection. If it also turns out that the person resided or stayed in an area infested with the black-legged tick, there is usually little doubt. It is then justified to begin treatment with doxycycline without the need to confirm the diagnosis in the laboratory.
Public health authorities recommend not waiting for the appearance of an erythema migrans before starting preventive treatment with doxycycline if the following conditions are met:
Less than 72 hours have passed since the tick was removed.
The tick has been attached for more than 24 hours.
Treatment with doxycycline is not contraindicated for the person.
The person was bitten in one of the geographical areas designated as higher risk.
If the situation is less clear, a diagnosis can be made by detecting the presence of antibodies produced against the bacterium in the blood. This approach will be used if the person has not visited one of the higher-risk areas, does not have an erythema migrans rash, or if the illness has reached the later stages.
Quebec health authorities only allow the so-called two-tier approach, which involves identifying antibodies using an enzyme immunoassay, followed by confirmation of a positive result using an immunoblot (western blot). Certain tests proposed by American laboratories for the diagnosis of the chronic form of Lyme disease are strongly discouraged.
As with many other diseases, prevention remains the weapon of choice. The first step is to determine whether you are engaged in high-risk activities in a designated area: hiking, picnicking, bird watching, gardening or golfing near a wooded area, picking wild fruit or mushrooms, and so on. Some jobs, such as a biologist or wildlife officer, or any other activities in nature, obviously involve a higher risk.
According to public health agencies, prevention is also based on simple and effective measures:
Avoid tall grass.
Wear a hat, closed shoes and long, light-coloured clothing (to help you see the ticks) in order to limit exposed areas of the skin.
Apply insect repellent to unprotected skin.
Inspect your body and those of your children thoroughly after the activity.
Use a mirror or ask someone to help you inspect less visible areas, such as the back or top of the head.
Using fine-tipped tweezers, such as eyebrow tweezers, immediately and gently remove any tick present on the body (read these tips on removing a tick).
Carefully examine your equipment and pets and, ideally, take a shower or bath within two hours of completing the activity.
These simple precautionary measures should allow you to enjoy the many benefits of outdoor activities!
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