Tick-borne encephalitis (TBE) was known to have occurred in humans in the area of Mecklenburg-Western Pomerania in Germany, until 1985. Between 1992 and 2004 more than 16,000 ticks were tested and found to be negative for TBE virus in that area of Germany, wich was therefore thought to be free of TBE. But after 19 years three autochthonous cases of human TBE-infections were identified between 2004 and 2006. We subsequently collected ticks from the three areas where the infection had been acquired and tested them for the presence of TBE-virus RNA with a nested reverse transcription polymerase chain reaction (RT-PCR). Since there is evidence that a blood-meal leads to an increase of FSME-RNA in ticks, we tested both, unfed ticks and ticks after a blood-meal. Three unfed and one fed nymph from the area around Lake Woblitz and one unfed and one fed nymph from Thiessow were positive for TBE-virus RNA. A total of six of 250 (2.4%) ticks tested positive for TBE-virus. The emerging of human TBE infections in three regions in Mecklenburg-Western Pomerania shows that the activity of natural TBE virus foci does not cease even after decades, or that TBE-infected ticks could have recolonized these regions.
Georg Thieme Verlag KG Stuttgart, New York.