In the majority of cases, tick bites are harmless, but they can sometimes cause certain diseases in humans, including tick-borne encephalitis. In Belgium, the virus has been shown to circulate in animals since several years, and occasionally transmission to humans has been described. A vaccine is sometimes recommended when traveling to at-risk countries in Europe, such as Austria and Sweden.
Tick-borne encephalitis is a disease caused by a virus, which is transmitted when bitten by an infected tick. In Europe, ticks involved in transmission are mainly of the genus Ixodes, which are found in shaded areas covered with thick litter or densely invaded by brush, ferns, and tall grasses. Small rodents are the natural reservoir of the virus.
Transmission of the virus is also possible through ingestion of unpasteurized milk and milk products from infected cattle, sheep and goats.
The risk of infection varies according to the seasons and is highest from June to October, i.e. during the period of tick activity.
Diagnosis of the disease is performed at the National Reference Centre for arboviruses, at the Institute of Tropical Medicine.
In about two thirds of cases, infection in humans will not cause symptoms and will therefore go unnoticed. When the disease develops, two symptomatic phases are usually separated by a symptom-free period: one phase of influenza syndrome and another characterized by damage to the central nervous system (meningoencephalitis). In this case, the disease can be severe, with a mortality rate of 0.5% to 2%.
The disease is present in Asia and Europe, with a higher risk in Central Europe (Austria, Switzerland, Germany, etc.) and in Eastern Europe (Czech Republic, Hungary, Poland, etc.), in the Baltic states (Estonia, Latvia, Lithuania), as well as in certain regions in Sweden and Finland. A map presenting risk areas for TBE in Europe is published on the website for travellers of the Institute of Tropical Medicine.
Seroprevalence studies in animals (deer, wild boar, cows, etc.) have shown that the virus also circulates in Belgium. This was also confirmed by some sporadic infections in persons who did not travel to an at-risk country.
There is a vaccine that is recommended in Belgium for people who travel to an area or country at risk and engage in outdoor activities (bivouacking, hiking, etc.). Consult the advice ‘Vaccination against tick-borne encephalitis’ of the Superior Health Council.
