Tick-borne meningo-encephalitis in Canton Thurgau: a clinical and epidemiological analysis

Background: Tick-borne meningo-encephalitis (TBE) is caused by a flavivirus species that is transmitted from rodents to humans by Ixodes ticks. The cl inical picture of central nervous system involvement varies from febrile he adache to lethal encephalitis. To date no specific treatment exists, althou gh protective active immunisation is available. Methods: We present the clinical and epidemiological data from 73 patients with TEE who acquired the infection in Canton Thurgau in the years 1996-199 9. Results: Canton Thurgau is a state in eastern Switzerland with a population of 230 000. Within the last five years the reported cases of TEE have incr eased more than threefold. The area where infectious tick bites were regist ered has expanded from the western to the eastern part and now encompasses the entire state. The risk of infection is clearly related to frequent acti vities in wooded areas, though outdoor activities not in forests also carry a considerable risk. In >80% of the cases a postviral neurasthenic syndrom e develops involving absence from work for two months on average. In the el derly 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 TEE, the expansion of infectious ti cks to the east and high morbidity justify active immunisation against TEE on a broad scale in Canton Thurgau.