Symptoms
Early summer meningoencephalitis (TBE) is asymptomatic in about 70-90% of cases. It is characterized by its biphasic course. In the early phase, which lasts 4-6 days, there are flu-like symptoms such as fever, headache, aching limbs, nausea and vomiting. Neurological symptoms such as visual disturbances may also occasionally occur. This is followed by a short, asymptomatic phase, at which point the disease is over for the majority of patients (70-80%). 20-30% of infected persons go through the second phase of the disease, in which the central nervous system is affected. Dangerous inflammatory reactions of the nervous system develop with inflammation of the brain and/or meninges. These are accompanied by high fever, severe headache, neck stiffness, sensitivity to light, dizziness, speech and walking disorders, and paralysis. In approximately 10% of cases with a second phase, inflammation of the spinal cord or spinal nerve roots may also develop, causing secondary damage or being fatal in 1-2%.
Causes and causative agents
The TBE agent is an RNA virus of the flavivirus family that is transmitted to humans by tick species of the genus with saliva. Two subtypes are distinguished based on geographic location: (the common wood tick) is the transmission vector in Central and Eastern Europe, while TBE virus is responsible for spreading in Russia and the Far East. The virus is related to West Nile virus, which causes similar clinical pictures.
Transmission
TBE virus resides in the salivary glands of infected ticks and enters the human bloodstream directly during a tick bite. Rarely, viral infection is possible through consumption of nonpasteurized milk from TBE-infected cows, sheep, or goats. Cases have also been described in which the virus was transmitted during blood transfusion and breastfeeding. Rodents, birds, and deer are the natural reservoir for the virus. TBE, on the other hand, cannot be passed from person to person.
Complications
In 20-30% of severe courses, permanent damage and symptoms must be expected. These include headache, fatigue, dizziness, hearing and vision deterioration, emotional lability, locomotor disorders, memory impairment, and paralysis. Long-term damage primarily affects adults. In children, the disease is usually benign and without sequelae. Children under 6 years of age are very rarely affected. About 1% of those affected die as a result of the attack on the nervous system.
Risk factors
The risk of infection increases for those who live or work in TBE endemic areas. Forest workers are particularly affected. Recreational activities such as hiking or camping may also pose a risk for infection in endemic areas. Furthermore, age is a decisive factor for the severity of the course of the disease. The older the person, the worse TBE can be.
Diagnosis
Diagnosis is made by medical treatment on the basis of a detection of IgM and IgG antibodies in the serum. Other viral infections that can also cause meningitis or encephalitis must be excluded. Examples include herpes simplex, measles, mumps, rubella virus, and West Nile virus.
Drug treatment
To date, no antiviral therapy exists. Therefore, the infection can only be treated symptomatically.
Vaccination
To protect yourself from TBE viruses, you can get vaccinated. TBE vaccination is especially indicated for people who live or stay in endemic areas. For detailed information, see TBE vaccination.
Prevention
The risk of TBE infection can be substantially reduced by avoiding habitats with high tick densities, such as forests, and by not roaming underbrush, shrubbery, and tall grasses. Another measure that helps protect against tick bites is wearing closed clothing such as shirts, blouses, sweaters with long sleeves, pants with long legs, and closed shoes or boots. Insect repellents are also frequently used. Products containing DEET or Icaridin, for example, can be applied directly to the skin. After high-risk visits, the body should be checked for ticks.Rapid tick removal does not prevent infection, but may reduce the severity of the disease. Transmission through milk, which is rare, can be avoided by pasteurizing the milk.
