Tick-borne encephalitis (TBE)

This virus affects the central nervous system, causing inflammation of the brain (encephalitis) and meninges (meningitis). TBEis caused by the tick-borne meningoencephalitis virus, transmitted mainly by the Ixodes ricinus tick, widely present in forests and grassy areas up to 2000 meters altitude. Ticks become infected by feeding on hosts, such as rodents, which carry the virus. The virus is transmitted through the bite of an infected tick, during the first few minutes after it has latched on to feed on blood. Immediate removal of the arachnid does not systematically eliminate the risk of infection. Contamination through consumption of unpasteurized dairy products, particularly goat's milk, has also been documented.

Symptoms of TBE generally appear in two phases.

• The first phase, occurring 7 to 10 days after the bite, is characterized by flu-like symptoms: fever, headache, fatigue, muscle aches. The majority of infected people show no symptoms at this stage.
• The second phase, which affects around 10% of infected people, following damage to the central nervous system, is characterized by more severe symptoms such as intense headaches, high fever, neurological disorders, stiff neck, dizziness and paralysis.

In children, symptoms are often mild, limited to fever. In the case of neurological involvement, meningitis (headache, nausea, vomiting, dizziness, stiff neck) is the most common form.

Symptoms may be confused with those of a simultaneous infection with the Borrelia burgdorferi bacterium, responsible for borreliosis or Lyme disease, transmitted by the same vector tick.

The main risk factors include exposure to ticks during outdoor activities in endemic areas, notably Switzerland (with the exception of the canton of Ticino). People who spend a lot of time in forests or grassy areas are particularly at risk, especially in spring and summer, when ticks proliferate. In addition, people who consume unpasteurized dairy products from endemic areas may also be exposed to the virus. The elderly are more likely to develop serious complications.

As TBE is a viral infection, there is currently no specific medication available. Treatments available are symptomatic, aimed at relieving pain and fever. In severe cases, hospitalization may be required for supportive care, such as management of neurological symptoms and prevention of secondary complications.

There is, however, a vaccine against TBE, recommended for everyone from the age of 3.

Although a central nervous system infection can be cured, many patients suffer long-term neurological sequelae. Some 30-50% suffer from residual symptoms such as chronic fatigue, headaches, muscle pain and cognitive impairment. In some cases, more serious sequelae may persist, such as severe cognitive impairment or chronic respiratory paralysis representing a major life-threatening risk.

Preventing TBE involves a number of measures:

• Vaccination: Vaccination against TBE is highly effective and recommended for all people living or staying in high-risk areas. Two vaccines are authorized in Switzerland for children and adults. Primary vaccination comprises 3 doses, and a booster is recommended every 10 years. The vaccine provides over 99% protection in vaccinated individuals.
• Protection against tick bites: Wear long, covering clothing, use repellents, and check regularly for ticks after outdoor activities.
• Food precautions: Avoid consumption of unpasteurized dairy products in high-risk areas.

The doctor will review the patient's clinical history to determine whether he or she has been vaccinated against TBE and, if so, whether he or she has been exposed to ticks. Depending on the symptoms observed and the results of the medical examination, he or she will consider the need for a blood test. The final diagnosis is made on the basis of all these elements.

Symptoms such as fever, headache, joint pain or flu-like symptoms following a tick bite warrant prompt medical attention. Early medical intervention can help manage symptoms and prevent serious complications.

Hôpital de La Tour offers comprehensive care for TBE patients, and has a neurology department for the diagnosis and treatment of neurological complications.

How is Tick-borne encephalitis transmitted?
Tick-borne encephalitis is transmitted mainly through the bite of infected ticks, but also through the consumption of unpasteurized dairy products in certain regions.

What are the symptoms of Tick-borne encephalitis ?
Symptoms include fever, headache, muscle pain and neurological disorders.

Is there a treatment for Tick-borne encephalitis?
There is no specific treatment for tick-borne encephalitis ; care focuses on symptom relief and prevention.

How can tick-borne encephalitis be prevented?
Prevention involves vaccination, the wearing of protective clothing, the use of repellents and regular body examinations after outings in nature.