Tick-borne encephalitis (TBE)

Tick-borne encephalitis is a viral infection. The virus is mainly carried by wood mice but also by other mammals. Ticks that bite these animals can contract the TBE pathogen from them. If people are bitten by an infected tick, the viruses can enter their blood stream and trigger TBE. However, this is not the case with every tick bite.

On rare occasions, a TBE infection can also be caused by consuming infected unpasteurized milk. UHT milk (pasteurized milk), on the other hand, does not pose any risks.

The German name “Frühsommer-Meningoenzephalitis” literally translates as “spring meningoencephalitis” and gives the impression that the condition is caused by tick bites in spring and involves the inflammation of the meninges and the brain. This is not actually the case. Firstly, ticks can transmit the TBE virus at any other time of year as well. In fact, the risk of contracting the infection in Germany is actually highest in autumn and lowest in spring. Secondly, inflammation of the central nervous system (CNS) only occurs in about a third of people infected with TBE.

An average of 10 days pass between infection and the presentation of symptoms (incubation period) although this can range from 5 to 28 days. People who have been infected are not contagious.

The TBE symptoms generally occur in two phases:

Phase 1: mild TBE

The first indications of infection are general fatigue and flu-like symptoms such as a headache, high temperature and aching limbs. Stomach aches and vomiting are also possible. These symptoms usually disappear after a few days. In about 70 percent of adults, the condition solely appears in this form.

Phase 2: severe TBE

About 30 percent of infected adults temporarily improve but then find that their temperature rises again and they experience inflammation of the meninges, brain and/or spinal cord.

Inflammation of the meninges (meningitis) occurs in the second phase of the condition in about half of patients. These often have highly impaired general wellbeing, severe headaches and a very high temperature (fever). Children can become apathetic, fall into a coma or experience seizures.

In about 40 percent of patients, the brain is also affected (meningoencephalitis). In about 10 percent of people infected with TBE, the meninges, brain and spinal cord all become inflamed (meningoencephalomyelitis).

If multiple central nervous system (CNS) organs are affected, people struggle to coordinate their movements. Drowsiness, disorientation and paralysis of the arms and legs can also ensue. Damage to the cranial nerves manifests itself through facial paralysis and problems hearing, swallowing or speaking.

TBE viruses are transmitted to humans by ticks (specifically castor bean ticks). Transmission occurs within the first few hours of the tick bite.

Ticks are found in undergrowth, grass and bushes at a height of 30 to 60 centimeters. They do not fall from trees. In the mountains, they can survive at altitudes of up to about 1,500 meters above sea level. They are active in conditions involving high humidity and a temperature of anything above about 6 to 8 degrees Celsius.

Most people recover from tick-borne encephalitis after the initial phase of the illness but some people find that their symptoms disappear for about a week and they then enter a second phase.

This is characterized by inflammation of the meninges (meningitis), brain (encephalitis) and, in rare cases, the spinal cord (myelitis). The inflammation can occur in just one area or a mixture of them.

Inflammation of the meninges generally clears up without consequence. One in 5 patients who additionally experience inflammation of the brain recover fully. If the meninges, brain and spinal cord are affected, the chances of full recovery are the lowest. In such cases, the illness can be fatal.

About a third of severely ill patients are left with permanent damage to the nervous system.

Children have a higher chance of fully recovering from a severe case of TBE than adults. Adults over the age of 60 and people with a weak immune system have a higher risk of severe TBE.

On the whole, tick-borne encephalitis is a rare condition: 441 infections were reported in 2019. Almost 90 percent of cases in Germany occur in Bavaria and Baden-Württemberg.

The following regions are classed as high-risk:

• Bavaria
• Baden-Württemberg
• Thuringia
• South Hesse
• Certain districts in Rhineland-Palatinate, Saarland, Saxony and Lower Saxony

Information about high-risk areas for TBE in Germany can be found on the Robert Koch Institute website.

People who have previously contracted TBE have life-long immunity, meaning that they cannot get it again.

Although severe TBE is rare, it can have serious consequences such as paralysis. Effective TBE prevention is therefore extremely important, especially for people in high-risk areas.

There are two effective measures for preventing TBE infections:

• vaccination
• actively avoiding tick bites

Vaccination

The Robert Koch Institute’s Standing Committee on Vaccination (Ständige Impfkommission – STIKO) recommends vaccination for people who live or regularly stay in high-risk areas for TBE. The recommendation particularly applies to people who frequently spend time in forests or meadows (e.g. due to their job). There is also a travel vaccination for high-risk areas outside Germany.

• Basic immunization against the TBE virus requires 3 vaccinations, after which people remain protected for at least 3 years.
• Depending on people’s age, boosters are required every 3 to 5 years. Following complete basic immunization and a booster, 99 percent of people are fully protected against TBE.
• Children can be vaccinated once they are over 12 months of age.
• In high-risk areas, health insurance providers generally cover the cost of TBE vaccinations. For people in certain occupations, such as forestry workers, the costs are borne by employers.

The vaccine is directly injected into the muscle and is generally well tolerated. 10 in every 100 people experience temporary pain, redness and swelling at the injection site. Flu-like symptoms are also possible.

The TBE vaccine does not increase the attack rate in patients with multiple sclerosis.

Answers to frequently asked questions about the TBE vaccine can be found on the Robert Koch Institute (RKI) website.

Avoiding tick bites

The general protective measures include:

• ensuring clothing is tucked in
• avoiding undergrowth
• applying insect repellent to the body
• checking the body for ticks and removing them quickly

Other practical tips on how to protect yourself against tick bites can be obtained from the Federal Center for Health Education (Bundeszentrale für gesundheitliche Aufklärung – BZgA).

The doctor will start by asking if the person:

• has been in a high-risk area for TBE.
• can remember being bitten by a tick.
• has drunk or eaten any products containing unpasteurized milk.
• has had flu-like symptoms with a headache and high temperature.

A TBE infection can be diagnosed by performing laboratory tests on the blood or cerebrospinal fluid (liquor) to check for “IgM” and “IgG” antibodies. In some cases, magnetic resonance imaging (MRI) of the brain is also performed.

There is no causal treatment for TBE, i.e. there are no drugs that can directly combat the virus. As a result, doctors can solely treat the symptoms of the infection to alleviate these and help the body fight the infection.

TBE treatment options include:

• bed rest
• painkillers
• antipyretic drugs, but ideally only from a temperature of 39 degrees Celsius

Drugs containing cortisone should be avoided as they can impair the body’s natural immune defenses.

People who suffer from a severe case of TBE may require medical rehabilitation (rehab) after their treatment. Specialists like physiotherapists or speech therapists help patients reduce or completely overcome the consequences of TBE.

Being bitten by a tick does not instantly mean that it transmits a pathogen such as the Lyme disease (borreliosis) bacterium or TBE virus to the person bitten. To do this, the tick must firstly be a carrier of the pathogen and secondly transfer it into the person’s bloodstream via its saliva.

The longer an infected tick remains attached, the more likely it is to transmit a pathogen. This means the sooner ticks are discovered and removed, the better. 

When removing a tick, you should proceed calmly and systematically so that as little of it as possible remains in the wound:

• Never use oil or glue to remove a tick.
• Use tweezers, a tick hook or a tick removal card from a pharmacy.
• Try to grasp the tick on its head and mouth parts – not its body.
• Avoid squashing the tick.
• Pull the tick out straight and relatively slowly.
• Thoroughly disinfect the puncture site.