Epidemiological patterns of tick-borne encephalitis in Lithuania and clinical features in adults in the light of the high incidence in recent years: a retrospective study.

BACKGROUND AND PURPOSE: Lithuania is one of the countries with the highest incidence of tick-borne encephalitis (TBE) in Europe. The aim of this study was to describe the epidemiological patterns of TBE in Lithuania, and characterize clinical features in adults in the light of the high incidence in recent years. METHODS: Surveillance data available on the website of the Centre for Communicable Diseases and AIDS of Lithuania were used to describe the epidemiological patterns of TBE. The retrospective study included 712 patients hospitalized in the Centre for Infectious Diseases and the Centre for Neurology of Vilnius University in the years 2005-2014. RESULTS: Tick-borne encephalitis incidence rates have been increasing by 8.5% per year for the 45-year period from 1970 to 2014. The joinpoint model finds two joinpoints at 1991 and 1994, with a significant decrease of 8.4% per year (P < 0.05) prior to the joinpoint at 1991, and a rise of 195.2% afterwards. TBE presented with meningoencephalitis in 556 cases (81.3%). A total of 129 patients (18%) had a severe case of the disease. The most common neurological signs were ataxia (579, 81.3%), meningeal signs (474, 66.5%) and tremor (338, 47.5%). Limb paresis was observed in 6.3% of patients. Five patients (0.7%) died, and 544 patients (76.7%) were discharged with sequelae. CONCLUSIONS: Intensified efforts in promoting TBE vaccination will be needed in the light of the high incidence and expanded spatial distribution. Significant prognostic factors for severe cases of the disease were age above 61 and delayed immune response of specific immunoglobulin G.

Upsurge of tick-borne encephalitis in the Baltic States at the time of political transition, independent of changes in public health practices.

Despite evidence that socio-economic factors associated with political transition played a major causal role in the abrupt upsurge in tick-borne encephalitis (TBE) in the newly independent Baltic States, doubts are still repeatedly expressed about the importance of these factors relative to changes in public health practices that may have affected merely the registration of cases. In response to these doubts, evidence of relevant practices of surveillance, registration, diagnosis, awareness and immunization is presented as taken from archived data and interviews with experienced medical practitioners. There were changes that could have had neutral, negative or positive impacts on recorded TBE incidence, but the variable timing in these changes at both national and regional levels is not consistent with their having been responsible for the epidemiological patterns observed in the early 1990 s.