TBE (early summer meningoencephalitis)

Early summer meningoencephalitis refers to an inflammation of the brain or meninges caused by the TBE virus. You can become infected with the virus through a tick bite. In 2009, 313 people in Germany contracted TBE. The risk of becoming infected with TBE is particularly high in the months of June to August.

Once the disease has broken out, treatment is usually very difficult. In about ten percent of cases, the nervous system is also affected. Another ten percent of those affected suffer from late effects. These include concentration disorders, headaches and psychoses. Paralysis, on the other hand, occurs only in rare cases. About one to two percent of cases are fatal. To prevent TBE, a preventive vaccination can be administered.

TBE is found almost exclusively in risk areas such as forests.

TBE is transmitted to humans through tick bites. Ticks belong to the class of parasites that live on the blood of a host. Their habitat is grass, scrub and deciduous forests. In addition to forest workers, foresters and farmers, the disease also affects many people who become infected during outdoor recreational activities.

Rarely, people may also become infected with TBE by consuming raw milk or raw milk products (such as goat or sheep cheese). This source of infection is a great risk mainly in Eastern Europe, but in Germany it is considered very unlikely.

Ticks are only found when temperatures are between seven and ten degrees Celsius, i.e. mainly in the months of March to November. Warm winters and humid summers are considered extremely favourable for the reproduction of ticks and thus increase the risk of infection with TBE.

Nevertheless, not all ticks are infected with TBE, but only 0.2 to 5 percent. The virus that causes TBE is an RNA virus and belongs to the class of Flavi viruses. It is similar to the pathogens that cause dengue, yellow fever and West Nile virus. The virus is localised in the salivary glands of the ticks and is transmitted rapidly after the sucking act has been completed.

The incubation period of TBE is about ten days.

Normally, early summer meningoencephalitis has a two-phase course. The first symptoms appear on average seven days to two weeks after the tick bite. The patient suffers from flu-like symptoms:

• Fever and general fatigue
• Rhinitis
• headache and muscle pain
• loss of appetite, nausea, abdominal pain and diarrhoea

On average, every tenth TBE patient enters the second phase of the disease after a week in which no symptoms appear. In this phase, mainly neurological symptoms occur. The fever rises and is accompanied by severe headaches and pain in the limbs, as well as a severe feeling of illness.

The following parts of the nervous system are affected by TBE:

• Approximately 25 percent of those affected suffer only meningitis. This is characterised by severe headaches, sensitivity to light, dizziness, nausea and stiff neck.
• In about half of the patients, the brain is also affected by the infection (meningoencephalitis). In addition to the signs of meningitis, there are also paralyses, speech disorders, changes of character, as well as concentration and consciousness disorders.
• Ten percent of patients also suffer from an inflammation of the brain and spinal cord (meningoencephalomyelitis, meningoradiculitis), which manifests itself similarly to severe polio. In addition, breathing may also be affected.

Children are less likely to contract TBE, which also affects the nervous system. Therefore, it usually has a milder course than in adults and heals without permanent damage.

People who are ill with TBE cannot infect other people, as transmission from person to person is not possible.

In order to diagnose TBE, it is crucial to know whether the affected person was bitten by a tick and whether this happened in a risk area. From this information, the doctor can already draw initial conclusions as to whether TBE is present.

To make the final diagnosis, blood and cerebrospinal fluid are taken and examined in the laboratory. Based on certain laboratory values, it is possible to tell whether there is inflammation in the body. More specific is the detection of certain antibodies (IgG and IgM) that the immune system produces as a result of a TBE infection. In most cases, the results of the tests are conclusive and other diseases can be completely ruled out. However, if there is a borderline case in which a similar pathogen can be the trigger for the disease, a neutralisation test (TBE-NT) can provide clarity.

If there is a particularly severe case of TBE, or if the diagnosis is unclear, magnetic resonance imaging is also performed. With the help of this method, certain areas of the brain that are affected by the viruses can be visualised from three days after the onset of the second phase of the disease. Normally, the affected areas are located in a circumscribed region of the diencephalon (thalamus).

Once the disease has broken out, the therapy is very complicated. There is no specific treatment against the viruses. For this reason, protective measures should be taken against tick bites. Here, especially the vaccination has proven to be very effective.

The therapy of TBE aims at alleviating the symptoms and preventing possible complications. Affected persons should observe absolute bed rest and receive sedative and, if necessary, antiepileptic medication to alleviate the pain.

Patients suffering from a TBE infection of the nervous system are under constant surveillance so that countermeasures can be taken immediately in the event of complications, which may occur in the form of seizures, for example. Severe courses of the disease accompanied by respiratory paralysis and clouding of consciousness (up to coma) are treated in the intensive care unit.

The majority of TBE cases have no complications. The risk of dying from early summer meningoencephalitis is only one percent of the total number of cases.

However, the risk increases with the number of nerve structures affected by the virus. The most severe form of TBE, the combined inflammation of the meninges, brain and spinal cord (meningoencephalomyelitis), is lethal in ten percent of cases. Those who survive this form of the disease often suffer from concentration disorders, paralysis, epileptic seizures or headaches for months or years afterwards. Some of these symptoms may also remain permanent.

Meningitis without a combination of brain inflammation usually has quite good chances of recovery and little subsequent damage to health.

After a survived TBE infection there is a lifelong immunity.

In order to ensure a safe protection against TBE, you should get a preventive vaccination in winter. Thus, the vaccination protection is already active in spring, when the tick season begins. Vaccination is particularly advisable if you live in a TBE risk area or are planning a trip there. Forestry workers, farmers and laboratory personnel should also be vaccinated.

The common TBE vaccination is an active vaccination consisting of three doses (basic immunization). The first two injections are administered one to three months apart. The third dose is given nine to twelve months after the second. If a holiday to a risk area is imminent, two injections may be sufficient.

After basic immunisation, the first booster should be given after three years. For people under 50 years of age there is a five-year protection, for older people a booster is already necessary after three years.

To prevent TBE, it is also advisable to protect yourself from tick bites. For this purpose, tight-fitting, light-coloured clothing should be worn when in the forest or in high meadows. It is also advisable to avoid the undergrowth. Tick repellents have only a limited effect of a few hours.

After a stay in nature, the clothes and the body should be searched for ticks. Preferred areas for children are the hairy head and the neck. Ticks prefer to stay on warm parts of the body, which is why armpits, groins and the back of the knees should also be thoroughly searched. Even if the tick is removed immediately after discovery, this does not protect against TBE, as the virus is located in the salivary glands and is transmitted immediately after the bite.