Acta Univ Latv (2004) 676: 27–37

Tick-borne encephalitis – pathogen, vectors and epidemiological situation in Latvia 2002 - 2003

Abstract

Tick-borne encephalitis (TBE) morbidity in Latvia declined significantly in 2002 compared to the previous decade, although in 2003 the number of TBE cases rose again. Ixodes ricinus tick activity observations in nature as well as from the records on seasonal tick numbers removed from patients in the Vaccination service for TBE virus (TBEV) tests pointed to a sharp rise in nymph numbers. TBEV prevalence shown with ELISA in ticks removed from humans was four times higher than in field collected ticks, but the total TBEV prevalence level decreased in 2003. Investigations of TBEV by RT-PCR was performed by means of two methods, targeting 5'NCR (non-coding) or NS5 (nonstructural) sequences of the TBEV gene. The initial results of the newly adapted methods confirmed the validity of the developed RT-PCR and pointed at the necessity to improve and standardise the system of sampling, storage and transporting. Observations identified TBE as a continuing public health problem in Latvia requiring further research.