Lyme disease

Lyme disease is mainly caused by species of bacteria in the Borrelia genus. These bacteria are transmitted to humans by the bite of infected ticks. Ticks acquire these pathogens by feeding on infected animals. Transmission to humans then generally occurs through prolonged contact with natural environments where these ticks live: forests, clearings, parks. Found at altitudes of up to 2,000 m, they live at ground level, in grasses or bushes, from which they attach themselves to passing animals or humans. It generally takes around ten hours for borrelia to enter the bloodstream of the person bitten. The most common tick species in Switzerland is Ixodes ricinus.

Infection is usually asymptomatic, and only around 5% of tick bites cause the disease to develop. The clinical symptoms of borreliosis in humans are extremely varied, complicating diagnosis. This diversity of symptoms is explained by the existence of several species of Borrelia bacteria, leading to distinct organ involvement. The course of the disease can be divided into three phases.

• Typically, the first symptom is a local, circular reddening that spreads around the area of the bite. This symptom may appear between 7 and 14 days after the tick bite, and disappears after a few days or weeks.
• Secondly, a few weeks or months after the bite and as the infection progresses, other symptoms may appear, such as fever, chills, headaches, extreme fatigue, muscle and joint pain, and swollen lymph nodes. Finally, if left untreated, the infection can cause neurological complications, neuropathic pain and facial paralysis, as well as heart problems.
• Phase 3 is characterized by dermatological changes, joint pain, mobility difficulties and urinary disorders. Symptoms that may appear several years after infection.

Risk factors include exposure to areas where ticks are abundant, such as forests, tall grass and bushes. Outdoor activities such as hiking or gardening increase the risk of contact with infected ticks. The riskiest period is from spring to summer, when ticks are most active. Dry periods in summer and winter are less conducive to tick proliferation, although their organisms are particularly resistant to the vagaries of the weather. Pets also need attention, as they can be tick hosts.

The treatment of borreliosis/Lyme disease mainly involves the use of antibiotics. As Lyme disease is bacterial, there is no vaccine, unlike viral meningoencephalitis. In more complex or advanced cases, intravenous antibiotics may be required. It is crucial to start treatment as soon as possible to avoid serious complications.

Without appropriate treatment, Lyme disease can become chronic and in some cases lead to irreversible consequences. Despite successful antibiotic treatment, some patients develop post-Lyme syndrome, which doctors describe as residual disorders. This is characterized by persistent symptoms despite the absence of an active pathogen in the body.

Avoiding tick bites is the key to preventing Lyme disease. Wearing covering clothing and closed shoes is the most effective way to prevent this. Repellents can also be used. After outdoor activities, a meticulous examination of the body is recommended to identify the possible presence of ticks, in which case they should be removed as soon as possible and the area of the bite disinfected. Prompt action is crucial, as the risk of transmitting pathogens such as borreliosis increases over time.

If any of the symptoms of Lyme disease appear, it is advisable to consult a doctor. In the event of a tick bite, and if the tick has remained attached to the skin for more than 24 hours, a consultation may be warranted. Early diagnosis and treatment are crucial to prevent complications.

Do all ticks transmit Lyme disease?
No, not all ticks transmit Lyme disease. Only ticks of the genus Ixodes are known Lyme disease vectors, particularly Ixodes ricinus in Europe.

What are the first signs of Lyme disease?
The first sign is often erythema migrans, a circular redness that appears at the site of the tick bite. However, it is important to note that the appearance of symptoms is not systematic, and their absence does not rule out the possibility of infection.

How is Lyme disease diagnosed?
The diagnosis of Lyme disease is based on clinical symptoms, and can be confirmed by serological tests detecting Borrelia burgdorferi antibodies.

Can Lyme disease be treated?
Yes, with appropriate antibiotic treatment, especially when diagnosed early.

Can Lyme disease recur after treatment?
Immunity to Lyme disease is not guaranteed after infection; reinfection is possible. Although antibiotic treatment is generally effective, some patients may experience persistent symptoms known as "post-Lyme syndrome". These symptoms are generally managed by symptomatic approaches.

What's the riskiest time of year for tick bites?
Ticks are most active in the warmer months, generally from spring to autumn. However, in some regions, they can be active all year round if temperatures remain above freezing.

Is there a vaccine against Lyme disease?
There is no vaccine against Lyme disease available to the general public. Prevention is based on wearing covering clothing and using repellents to avoid tick bites, and inspecting the body after being outdoors.