Lyme disease

Transmitted by ticks, Lyme disease is an infectious disease. It can be difficult to diagnose.

Discover our complete fact sheet below to find out more.

  Lyme disease, what is it?

Lyme disease or Lyme borreliosis is an infectious, non-contagious disease caused by a bacterium, Borrelia burgdorferi, transmitted by ticks.

The disease is sometimes difficult to diagnose since tick bites are not always visible and the symptoms are similar to those of other diseases such as the flu.

Lyme disease is usually cured effectively with antibiotics. If not treated quickly, the disease can affect the joints and the nervous system.

Transmission of Lyme disease

Lyme disease is caused by infection with the bacteria Borrelia burgdorferi. In Europe, other bacterial strains (B. garinii, B. afzelii, B. spielmanii, B. valaisiana) can cause Lyme disease with somewhat different symptoms.

This bacterium is transmitted to humans through the bite of an infected tick. Ticks (of the genus Ixodes) inhabit wooded areas and become contaminated when they feed on the blood of small rodents (mice, squirrels), birds and other mammals (deer, horses, dogs, etc.) which can be carriers of the bacteria. Most of these animals do not develop the disease.

The infected tick transmits the bacteria to humans during a bite. The bacterium is distributed in the skin and then in the blood and tissues. Humans mainly contract the disease from spring to autumn, during walks in the forest, when ticks are numerous. Tick ​​bites are usually painless and most people don't know they've been bitten.

In Canada, two types of ticks are responsible for transmitting Lyme disease: the western blacklegged tick (Ixodes pacificus) in British Columbia and the blacklegged tick (Ixodes scapularis) in the rest of the country. Note that ticks in a region affected by the bacteria are generally infected in a proportion of 5 to 35%. In France, the tick mainly responsible is Ixodes Ricinus.

Lyme disease is not passed from person to person. Pets can carry infected ticks into homes or gardens.

 Lyme disease: symptoms

A skin rash, a small red bump at the site of the tick bite. In a few days, this redness spreads forming a circular red patch lighter in the center, hot, several centimeters wide (called erythema migrans). This redness usually appears 7 to 14 days after the tick bite.

Some people develop multiple such rashes, indicating that the bacteria is multiplying in the bloodstream. Some affected people show no redness (20% of cases).

Other symptoms:

When not treated quickly, weeks or months after infection, the disease can cause:

arthritis, joint pain or inflammation of the joints, especially the knees. Arthritic symptoms can even become chronic and last for several years when the disease is not treated;

neurological problems, such as meningitis, temporary paralysis on one side of the face (Bell's Palsy), numbness or weakness of limbs or muscles.

More rarely :

  • heart problems such as irregular heartbeats (usually only lasts a few days or weeks);
  • eye inflammation;
  • hepatitis;
  • extreme fatigue and general weakness.

Lyme disease: who is affected?

Lyme disease is present on all continents, but it is most prevalent in temperate and cold regions of the Northern Hemisphere (in Europe, Asia and North America), especially in forested regions.

In Canada, populations of infected ticks are established in southern regions of Manitoba, Ontario and Quebec and in parts of New Brunswick, Nova Scotia and southern British Columbia.

In France, the most affected areas are the east and center of the country.

In France, the incidence of Lyme disease varies by region and there are approximately 12,000 to 15,000 new cases per year (Data from the Institut Pasteur).
 Lyme disease: how to prevent it?
Work or frequent grassy or wooded areas in regions where infected ticks are abundant;
failing to protect the skin of people who spend time outdoors in areas affected by infected ticks;
failing to quickly and appropriately extract ticks attached to the skin;
own a domestic animal (cat, dog, horse) that frequents the wooded areas affected by the disease.

Prevention and risks

Simple precautionary measures can limit tick bites and thus avoid infection by the bacteria responsible for the disease.

In the early stages, Lyme disease is usually easily treated with antibiotics. However, if it is delayed in treatment, the disease can lead to serious complications that are more difficult to treat.

Basic preventive measures

  • In tick-infested areas:
wear appropriate clothing that covers arms, legs and neck and use DEET-based mosquito repellent;
carefully inspect the skin for ticks after a walk in the forest. Within 24 to 48 hours, extract the ticks (taking care to remove the head) that attach to the skin using forceps and disinfect the affected area;
pets (e.g. cats, dogs, horses) can be treated with anti-tick powders as a preventive measure.