[Tick-borne meningoencephalitis in Thurgau Canton: a clinical and epidiomological analysis]

Abstract

Background: Tick-borne meningo-encephalitis (TBE) is caused by a flavivirus species that is transmitted from rodents to humans by Ixodes ticks. The clinical picture of central nervous system involvement varies from febrile headache to lethal encephalitis. To date no specific treatment exists, although protective active immunisation is available.

Methods: We present the clinical and epidemiological data from 73 patients with TBE who acquired the infection in Canton Thurgau in the years 1996-1999.

Results: Canton Thurgau is a state in eastern Switzerland with a population of 230,000. Within the last five years the reported cases of TBE have increased more than threefold. The area where infectious tick bites were registered has expanded from the western to the eastern part and now encompasses the entire state. The risk of infection is clearly related to frequent activities in wooded areas, though outdoor activities not in forests also carry a considerable risk. In > 80% of the cases a postviral neurasthenic syndrome develops involving absence from work for two months on average. In the elderly and patients who present with encephalitic symptoms, a worse outcome with persistent neurological symptoms or even death has been observed.

Conclusion: The increasing incidence of TBE, the expansion of infectious ticks to the east and high morbidity justify active immunisation against TBE on a broad scale in Canton Thurgau.