What is tick-borne encephalitis?
Tick-borne encephalitis is an inflammation of the brain or meninges that is caused by the tick-borne encephalitis virus (TBE virus). Until recently, the virus only occurred abroad, but in the spring of 2016, there were signs that in the Netherlands deer had been infected by the virus and the virus was found in ticks in the Netherlands. There is one known case of a person having been infected by the virus in the Netherlands. The virus is transmitted by tick bites.
There are several types of TBE virus. In general, all types cause infections with a similar disease progression. The TBE virus which occurs in Far-Eastern Russia often causes more serious disease. The risk of an infection after a tick bite is very small, because only very few ticks are infected with the TBE virus. People who have been infected after a tick bite usually do not present any clinical manifestations. Otherwise the disease often comes in 2 phases. The incubation period of 7-14 days is followed by a phase in which a patient suffers from fever, fatigue, general malaise and headache. This usually lasts 2-7 days and is followed by an asymptomatic period of approximately 1 week, In the second phase of the disease the patient has symptoms such as severe headache and encephalitis, meningitis or meningoencephalitis. In this stage the patient needs to be admitted to a hospital. Some patients will develop unresolved neurological aspects. Approximately 1-2% do not survive. There is no specific medication to treat tick-borne encephalitis.
Infection and prevention
The TBE virus is
transmitted by infected ticks to humans . There is a vaccine that
gives 95% protection. People who stay for a long period in areas
where tick-borne encephalitis occurs, can have themselves
vaccinated; this is recommended for example in parts of Central and
Eastern Europe. For information about countries where vaccination
is recommend, we refer to the website of the National
Coordination of Advice for Travellers (Landelijke Coördinatie
Reizigersadvisering). For the time being, there is no reason to
vaccinate people in the Netherlands.
Removing ticks as soon as possible reduces the infection risks of viruses they may carry, such as the virus that causes Lyme disease. TBE virus, however, is transmitted shortly after the bite. So, quickly removing the tick will not always prevent infection. Tick bites can be prevented by wearing protective clothing and by using repellents that contain DEET on exposed skin. Repellants do not protect 100%, so tick bite checks remain a necessity after being outdoor/in nature. TBE virus is rarely found in farm animals, such as sheep, goats and cows. The virus is than excreted in milk. As a result people could be infected by drinking unpasteurized infected milk or eating cheese made from infected milk.
Where does the tick-borne encephalitis virus occur?
Tick-borne encephalitis virus occurs in parts of Europe, Russia and Central Asia. In Europe there are approximately 2000 patients with TBE per year and in Russia approximately 10,000. In the Netherlands, the TBE virus has been found in ticks in the national parks Sallandse Heuvelrug and Utrechtse Heuvelrug. RIVMNational Institute for Public Health and the Environment investigates, in collaboration with other organisations, the spread of the TBE virus in the Netherlands and the risk of infection.