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Science  —  8 minutes

Lyme Disease

May 10th, 2024
Raymond Lepage, PhD, Doctor in Biochemistry
Raymond Lepage, PhD, Doctor in Biochemistry
Science popularizer
insecte lyme disease

What is Lyme disease?

Lyme disease is named after the small town in Connecticut where an explosion of rheumatoid arthritis cases was observed in a large number hundreds of children in 1975. It was only seven years later that we 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.

Most affected areas

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. The tick's territory, initially concentrated in Montérégie, Estrie and southern Ontario, is now expanding northwards at a rate of 33 to 55 km per year (1). Since these ticks can be carried by birds, the risk of contracting Lyme disease, which is currently rather low in other regions, will increase with global warming (2). Black-legged ticks are most active in the summer (June, July and August), although they can also infect people as soon as the temperature rises above 4°C (April to December).

About 20% to 25% of black-legged ticks are infected with B. burgdorferi but this rate can rise to 40% in regions where it is well established 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:

  • Paralysis of facial nerves (Bell's palsy);
  • Pain and numbness in the limbs;
  • Stiffness in the neck;
  • Cardiac rhythm disorders;
  • Chronic damage to large joints (after several years).
The “Long” Lyme Disease

According to healthcare professionals and observations made in several affected individuals, there is also another chronic form of Lyme disease of the same type as the one associated with Long COVID. This form could manifest itself several years after an untreated 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 without initial diagnosis is the subject of much greater controversy. This debate is fuelled by the current difficulty in reliably detecting traces of the bacterium presence in the body after several years, and by the dangerous nature of the treatment- which involves administering highly potent broad-spectrum antibiotics such as - doxycycline - for several months. Research is ongoing to confirm whether hygromycin A, a recently “rediscovered” low-spectrum antibiotic (highly specific to B. Burgdorferi), could offer treatment with fewer undesirable side effects (3).

Diagnosis, symptoms and treatment

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 the infection. If it also turns out that the person resided or stayed in an area infested with the black-legged tick, all doubts can be cleared. It is then justified to begin treatment with doxycycline without the need for laboratory confirmation of the presence of bacteria.

In the most severely affected regions, Public health authorities even 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 is 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.

For laboratory diagnosis, the Quebec health authorities only allow the so-called two-tier approach, which, in the first stage, involves identifying antibodies in the blood using anti B. Burgdorferi, an enzyme immunoassay, followed by confirmation of a positive result using an immunoblot (western blot). Certain tests offered by American laboratories for the diagnosis of the chronic form of Lyme disease are strongly discouraged.

Preventive measures

As with many other diseases, prevention remains the best way to avoid tick bites. The first step is to evaluatewhether 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). (4)
  • Carefully examine your equipment and pets and, ideally, take a shower or bath within two hours of completing the activity.

Ticks prefer damp, shady habitats such as wooded and grassy areas. As part of a joint research project with the City of Bromont, a team of researchers from the Université de Montréal has provided advice on how to reduce the number of ticks in the immediate environment of families living in high-risk areas.

These advices consist in identifying and favoring certain habitats that are less favorable to tick exposure (5) :

  • Maintained grass surfaces;
  • Ornamental vegetation;
  • Urban areas, concrete, asphalt, gravel, wood or mulch surfaces.
Need to identify a tick to find out if it is a blacklegged tick?

Visit the eTick website

These simple precautionary measures should allow you to enjoy the many benefits of outdoor activities!

This revised edition reflects an updated version from the original version published on April 2nd, 2019, on our website. We have incorporated recent facts to offer you current and pertinent information.

For professional support, we’re here!

We offer services that can help your doctor diagnose Lyme disease and determine the appropriate treatment.

If you have any questions or would like more information, contact our customer service number at 1 833 590-2712

  1. PA Leighton coll. “Predicting the speed of tick invasion: an empirical model of range expansion for the Lyme disease vector Ixodes scapularis in Canada”. J. Appl. Ecol. 2012; 49 : 457-464.
  2. Ariane Kroll. Maladie de Lyme. Les tiques à l’assaut du Québec. La Presse Plus, 10 mai 2024. Consulté le 10 mai 2024.
  3. R. Béliveau. Un antibiotique contre la maladie de Lyme . Journal de Montréal, 5 décembre 2021. Consulté le 10 mai 2024.
  5. Ville de Bromont. Projet de recherche sur la maladie de Lyme. Consulté le 10 mai 2024.
Raymond Lepage, PhD, Doctor in Biochemistry
Raymond Lepage, PhD, Doctor in Biochemistry
Science popularizer
For about 50 years, Raymond Lepage worked as a clinical biochemist in charge of public and private laboratories. An associate clinical professor at the Faculty of Medicine of the Université de Montréal and an associate professor at the Université de Sherbrooke, he has also been a consultant, researcher, legal expert and conference speaker. He has authored or co-authored more than 100 publications for scientific conferences and journals, and now devotes part of his semi-retirement to popularizing science.