Tick-borne encephalitis virus (TBEV)-specific RT-PCR for characterization of natural foci of TBE and for other applications.

An effective detection system for TBEV-RNA sequences using a RT-PCR technique has been developed. In our system, specific oligonucleotide primers corresponding to the 5'-terminal noncoding region were successfully used to identify TBEV sequences in ticks. To prove the specificity of the PCR products, Southern blot hybridization with an internal digoxigenin-labelled probe was carried out. In this paper, we present some potential applications of this technique. The primers were used to identify 21 TBEV strains isolated in different years, in different geographic regions and from different sources. 22313 Ixodes ricinus ticks from north-east Germany were analyzed for TBEV-specific sequences in order to characterize the viral activity in natural foci of TBE. In the new Federal Länder, only 6 samples gave positive PCR-results, showing that the natural foci of TBE had not been extinguished but remained in a state of endemic latency. We also used the RT-PCR to develop an animal model to investigate the temporal pattern of viraemia in the Mongolian gerbil (Meriones unguiculatus) through xenodiagnosis (sequential tick feeding on an infected host and subsequent RT-PCR testing of the resultant engorged ticks).