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Tick-borne encephalitis virus (TBEV) (Flaviviridae, Flavivirus) is an arthropod-borne virus, an etiologic agent of tick-borne encephalitis (TBE), a human infection involving the central nervous system. The disease is endemic in a large region in Eurasia, where it is transmitted mainly by Ixodes ricinus and Ixodes persulcatus ticks. It is known that also Dermacentor reticulatus is involved in circulation of TBEV. However, the current knowledge of D. reticulatus importance in TBE epidemiology is still insufficient. A total of 471 adult D. reticulatus ticks were collected by flagging vegetation in the Białowieża Primeval Forest, Biebrza National Park, Masurian Landscape Park (North-Eastern Poland) and in the city of Warsaw in the years 2007-2010. All collected ticks were examined individually for the presence of RNA of TBEV using nested RT-PCR assay. Positive results were noted in all investigated localities with the infection rate ranging from 0.99 to 12.5 % with a total mean of 2.12 %. The difference in the percentage of infective males and females was not statistically significant.

We provide evidence that tick-borne encephalitis virus and Borrelia burgdorferi s.l. are accumulated in the cement plug in the host skin within the first few hours after tick attachment. Extirpation of the tick without the cement plug, even very soon after the attachment, did not prevent the transmission by Ixodes ricinus, Ixodes persulcatus or Dermacentor reticulatus to mice. This was within 1 hour in the case of the TBE virus and after 20-22 h of attachment, in the case of Borrelia and I. persulcatus. The epidemiological significance of these findings is discussed.