Radzišauskienė et al.
The epidemiology, clinical presentation, and predictors of severe tick-borne encephalitis in Lithuania, a highly endemic country: A retrospective study of 1040 patients
PLoS ONE. 2020; 15(11): e0241587,
doi.org/10.1371/journal.pone.0241587
Lithuania is one of the countries with the highest incidence of TBE cases. A retrospective study has been carried out from 2005 to 2017 to analyze the epidemiology and clinical presentation of severe TBE cases in this country.
Among 1040 patients included in this study, the mean age was 49.9 years and 55.2% were men. Most patients were admitted to the hospital from July to September. A total of 14.6% had a severe form of illness (from 7.1% in 2005 to 26.5% in 2010). Patients with a severe TBE were on average 6.2 years older than patients with a non-severe TBE. The results of univariate and multivariate logistic regression showed that each additional 10 years increase the risk of severe TBE by 30%.
The predominant clinical form of TBE was meningoencephalitis (82% of all cases), and 23.7% of severe patients and myelitis. The most frequent neurological signs were cerebellar ataxis (81.9%,) meningeal signs (61.7%) and extrapyramidal tremor (52.6%). A total of 20.2% had quantitative impairment of consciousness.
Severe cases had more elevated C-reactive protein, higher pleocytosis, a higher percentage of neutrophils and a higher level of protein in CSF compared to non-severe cases. The mean length of hospital stay was 12 days and 29.8% of the patients were treated in the intensive care unit. On discharge, 81% of the patients presented sequelae, most of them had myelitis. The presence of comorbidities, high fever and protein concentrations in CSF 1 g/l and above doubled the odds of severe TBE. The lethality rate was 0.7%.
A total of 46% of patients became infected in their living area in Lithuania (and were not vaccinated), and as many as 69% among myelitis patients were infected in their living area.