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Science  —  5 minutes

Lyme Disease

April 2nd, 2019
Raymond Lepage, PhD, Doctor in Biochemistry
Raymond Lepage, PhD, Doctor in Biochemistry
Science popularizer

What is Lyme disease?

Lyme disease is named after the small town in Connecticut where an explosion of rheumatoid arthritis cases was reported in hundreds of children in 1975. It was only seven years later when it was confirmed that these cases were due to a bacterial infection transmitted by a single species of tick: the black-legged tick, also called the deer tick. The area where infected ticks are found is also a place where white-tailed deer and white-footed mice, the two main reservoirs of the bacteria, are abundant. The tick’s territory is expanding each year, largely due to global warming, and has spread from the Northeastern United States (especially Vermont and Maine), to Ontario and Quebec via the Montérégie and the Eastern Townships, the two regions currently most at risk. Infected ticks have also been identified in neighbouring regions, such as the Centre-du-Québec and the southwestern Outaouais. As ticks can be carried by birds, the risk of contracting Lyme disease in other regions will increase over time. Ticks are active mainly during the summer months (June to August), but infection can occur in any month when there is no snow on the ground, from April to December. About 20% to 25% of ticks are infected by the bacteria. Not all tick bites will cause Lyme disease. In addition, for the bacteria to infect the human body, the tick must remain on the skin for more than 24 hours.

A serious illness

Some people will experience no symptoms or very mild symptoms after being infected with the bacteria. The most specific sign of the infection is the appearance of a rash on the skin that gets bigger each day and can measure more than 5 cm (2 in.) across. This rash, called “erythema migrans,” often but not always takes the form of a bull’s eye, appearing between three and 20 days following the bite and often accompanied by flu-like symptoms such as fever, fatigue, muscle pain, joint pain and headache. In the subsequent weeks and months, an untreated infection may manifest itself as facial nerve damage (Bell’s palsy), pain and numbness in the limbs, a stiff neck, headaches, heart rhythm disorders and pain that moves from one joint to another. After several years, some people develop chronic damage to their major joints.

For many individuals and certain health care professionals, there is also a chronic form of Lyme disease that may appear several years after infection and include less specific symptoms such as chronic fatigue and pain in muscles and joints. While medical authorities recognize a post-treatment syndrome of Lyme disease in a number of people, the existence of a chronic form of the disease is the subject of considerable controversy. Fuelling this controversy are the current challenge of identifying traces of the bacteria after several years and the danger inherent in a treatment that involves using very powerful antibiotics for several months.

Diagnosing and treating Lyme disease

Within a period ranging from a few days to three weeks following infection, a diagnosis of Lyme disease in more than 80% of affected individuals is based mainly on the appearance of erythema migrans. The combination of this symptom with a history of living in or visiting a tick-infested area is sufficient to establish the diagnosis and justifies starting treatment with antibiotics without laboratory confirmation.

In tick-infested areas of Quebec, public health authorities also recommend that you don’t wait until symptoms appear (erythema migrans, etc.) before starting preventive treatment with doxycycline if:

  • Less than 72 hours have passed since the tick was removed.
  • The tick was on the skin for more than 24 hours.
  • The person has no contraindications to doxycycline.
  • The person was bitten in a designated geographical area.

In less clear-cut situations (e.g. typical symptoms but no visit to a designated area, suggestive symptoms but no erythema migrans, or a later phase of the disease), antibodies produced to combat the bacteria can be detected in the blood. The Quebec Public Health Laboratory (LSPQ) only authorizes the use of the two-tier approach, which involves identifying the antibody using the enzyme immunoassay technique, followed by confirmation of a positive result using the immunoblot (a.k.a. Western Blot). Certain tests offered by American laboratories and said to be useful for diagnosing the controversial chronic form of Lyme disease are prohibited.

Preventive measures

As with many other diseases, prevention remains the weapon of choice to defend against Lyme disease. First, you must decide whether to engage in high-risk activities in a designated area, such as hiking, picnicking, bird watching, gardening or golfing near a wooded area, picking wild fruit or mushrooms, etc. Certain jobs, such as biologist, wildlife officer or any other activity in nature, are obviously higher risk.

According to public health agencies, the other aspect of prevention is based on simple and effective measures:

  • Avoid tall grass and wear long, light-coloured clothing (to help you see the ticks); wear a hat and closed shoes, keep exposed skin to a minimum and use insect repellent on unprotected skin.
  • After the activity, thoroughly inspect your body and that of your children.
  • Use a mirror or ask someone for help to see less visible areas such as your back or the top of your head. Immediately and carefully remove any ticks from the body.
  • Examine your equipment and pets carefully and ideally, take a shower and a bath within two hours after the activity.

With these simple precautions, you should be able to enjoy the many benefits of being active in the great outdoors!