Encephalitis, Tickborne

Description

Tickborne encephalitis (TBE), also known as spring-summer encephalitis, is a viral infection of the central nervous system transmitted by bites of certain vector ticks. Human infections follow bites of infected Ixodes ricinus ticks, usually in persons who visit or work in forests, fields, or pastures. Infection also can be acquired by consuming unpasteurized dairy products from infected cows, goats, or sheep.

Occurrence

The disease occurs in Scandinavia, western and central Europe, and countries of the former Soviet Union. Risk of acquiring the disease is greatest from April through August, when Ixodes ricinus, the principal tick vector, is most active. TBE is common in Austria, Estonia, Latvia, the Czech Republic, Slovakia, Germany, Hungary, Poland, Switzerland, Russia, Ukraine, Belarus, and northern Yugoslavia. It occurs at a lower frequency in Bulgaria, Romania, Denmark, France, the Aland archipelago and neighboring Finnish coastline, and along the coastline of southern Sweden, from Uppsala to Karlshamn. Serologic evidence for TBE infection, as well as sporadic cases, has been reported from Albania, Greece, Italy, Norway, and Turkey. A closely related disease, Russian spring-summer encephalitis, which is transmitted by Ix. persulcatus ticks, occurs in China, Korea, Japan, and eastern areas of Russia. The severity of disease, incidence of sequelae, and case-fatality rates are higher in the Far East and eastern regions of Russia than in western and central Europe.

Risk for Travelers

The risk for travelers who do not visit forested areas or consume unpasteurized dairy products is low. Travelers with extensive unprotected outdoor, evening, and nighttime exposure in rural areas, such as might be experienced while bicycling, camping, or engaging in certain occupational activities, might be at high risk even if their trip is brief.

Prevention

Vaccine

Effective vaccines can be obtained in Europe from Baxter (Vienna, Austria, and Heidelberg, Germany) and in Canada from many travelers' clinics. Available data do not support recommending its use by those whose risk for infection is low. Anyone at high risk for infection who plans to be in infected areas during the warm weather months when ticks are active should be advised to be vaccinated.

Other

Travelers should be advised to avoid tick-infested areas and to protect themselves from tick bites by dressing appropriately and using repellents. Repellents containing N,N-diethylmetatoluamide (DEET) can be applied directly on the skin. Compounds containing permethrin have an acaricidal and repellent effect and should be used on clothing and camping gear. (See Protection against Mosquitoes and Other Arthropods) Consumption of unpasteurized dairy products should be avoided.

— Anthony Marfin