Tick-Borne Encephalitis

What is Tick-Borne Encephalitis?

Tick-borne encephalitis (TBE) is an infectious disease of the brain caused by a group of related viruses that can be found in many parts of the world.

How do you get Tick-Borne Encephalitis?

Tick-borne encephalitis viruses are transmitted to humans through the bite of an infected tick that is found mostly in rural areas, meadows, scrub brush, and forests and mainly in the summer and fall seasons. It is usually acquired through outdoor activities, such as camping, hiking, fishing, bicycling in the woods, and collecting mushrooms, berries or flowers. It is occasionally acquired by consuming unpasturised milk or cheese obtained from infected goats, sheep or cows. It is usually not spread person to person.

Susceptibility and Resistance

All persons are susceptible.  However, prior infection results in long lasting immunity to re-infection.

Incubation Period

The incubation period for Tick-Borne Encephalitis is 7-14 days.

What are the Symptoms?

About two-thirds of all infected people do not have symptoms.  Eye redness may be the only outward sign of infection.  However, when symptoms are present, they may vary depending on the type of virus. The disease often occurs in two phases. The first phase is marked by headache (sometimes severe), chills, fever, muscle aches and fatigue.  The second phase is marked by nervous system involvement, i.e., brain inflammation, signs of meningitis, paralysis of the upper extremities and other neurological symptoms.    

Most of these viruses cause mild symptoms lasting for about a week or less.  Some of these viruses may cause a fever first and then be followed some days later by all the symptoms of brain inflammation (encephalitis).

Preventative Measures

Travellers to countries where TBE occurs should avoid tick habitats where possible. Daily tick checks and prompt removal of any attached ticks will help to reduce the risk of infection. Ticks can be removed by grasping them firmly with tweezers as close to the skin as possible and lifting gently. It has been shown that if ticks are removed within approximately 36 hours of the bite, the risk of acquiring TBE is reduced to nearly zero. However, the small size of the tick, especially in the nymph stage, may make detection difficult. Insect repellent and protective clothing (long-sleeved shirts, long pants, and a hat) will also help to protect against tick bites.

Vaccines against TBE are only available in Europe where the vaccines have been used extensively in parts of Europe and Russia for persons living in areas where high exposure might occur. Vaccination is usually not necessary for most travellers unless they plan on camping, hiking, or spending time outdoors in forested areas where TBE occurs.

Treatment

There is no specific treatment for TBE viral infections other than treating the symptoms.  Milder illnesses improve on their own through rest and symptomatic treatment (such as over-the-counter pain medication for muscle and joint aches). Severe TBE illnesses may require hospitalisation and supportive treatment such as intravenous fluids and nursing care. 

Vaccinations

Where Does It Commonly Occur?

The group of viruses that cause this infection include three types that are found in Russia, including Siberia, and other countries in Europe (eastern France, Czech Republic, Estonia, Germany, Hungary, Latvia, Lithuania, Poland, Slovenia, Sweden, and Switzerland). In Asia, it is found in China, Japan, Mongolia, and South Korea. It is not found in the Western Hemisphere.

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