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Tick-borne encephalitis virus (TBEV) infection may cause acute central nervous system inflammation varying in clinical manifestations and severity. A possible correlation of TBEV-specific antibody and cell-mediated immune responses, shortly after infection, with clinical manifestations, severity and long-term outcome has been poorly investigated. In a cohort of thirty early tick-borne encephalitis (TBE) patients, we assessed the magnitude, specificity and functional properties of TBEV-specific T-cell and antibody responses. These responses early during disease were assessed in view of clinical manifestations, severity and long-term outcome. TBEV-specific T-cell responses to C, E, NS1, and NS5 proteins were significantly lower in patients with severe acute illness than in patients with mild TBE. Lower T-cell responses to E, NS1, and NS5 proteins also correlated with the development of meningoencephalomyelitis. Virus-specific antibody titres early after infection did not correlate with disease severity, clinical manifestations, or long-term outcome in this study, possibly due to the small number of patients of which matching serum and peripheral blood mononuclear cells were available. The findings suggest that virus-specific T cells afford a certain degree of protection against the development of severe TBEV-induced disease.

Tick-borne encephalitis (TBE) is a viral infection of the human central nervous system caused by the TBE virus (TBEV). The most effective protective measure against TBE is vaccination. Despite the highly immunogenic vaccine, cases of vaccine breakthroughs (VBTs) occur. One of the first targets of infection is dendritic cells (DC), which represent a fundamental bridge between innate and adaptive immunity through antigen presentation, costimulation, and cytokine production. Therefore, we investigated the activation and maturation of DCs and cytokine production after in vitro TBEV stimulation of peripheral blood mononuclear cells (PBMCs) obtained from VBT and unvaccinated TBE patients. Our results showed that the expression of HLA-DR and CD86 on DCs, was upregulated to a similar extent in both vaccinated and unvaccinated TBE patients but differed in cytokine production after stimulation with TBEV. PBMCs from patients with VBT TBE responded with lower levels of IFN-α and the proinflammatory cytokines IL-12 (p70) and IL-15 after 24- and 48-hour in vitro stimulation with TBEV, possibly facilitating viral replication and influencing the development of cell-mediated immunity. On the other hand, significantly higher levels of IL-6 in addition to an observed trend of higher expression of TNF-α measured after 6 days of in vitro stimulation of PBMC could support disruption of the blood-brain barrier and promote viral and immune cell influx into the CNS, leading to more severe disease in VBT TBE patients., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Marušić, Kopitar, Korva, Knap, Bogovič, Strle, Ihan and Avšič-Županc.)

Tick-borne encephalitis (TBE) usually has a biphasic course which begins with unspecific febrile illness, followed by central nervous system involvement. Because TBE is not yet suspected during the initial phase, knowledge of early TBE pathogenesis is incomplete. Herein we evaluated laboratory and immune findings in the initial and second (meningoencephalitic) phase of TBE in 88 well-defined adult patients. Comparison of nine laboratory blood parameters in both phases of TBE revealed that laboratory abnormalities, consisting of low leukocyte and platelet counts and increased liver enzymes levels, were predominately associated with the initial phase of TBE and resolved thereafter. Assessment of 29 immune mediators in serum during the initial phase, and in serum and cerebrospinal fluid (CSF) during the second phase of TBE revealed highly distinct clustering patterns among the three groups. In the initial phase of TBE, the primary finding in serum was a rather heterogeneous immune response involving innate (CXCL11), B cell (CXCL13, BAFF), and T cell mediators (IL-27 and IL-4). During the second phase of TBE, growth factors associated with angiogenesis (GRO-α and VEGF-A) were the predominant characteristic in serum, whereas innate and Th1 mediators were the defining feature of immune responses in CSF. These findings imply that distinct immune processes play a role in the pathophysiology of different phases of TBE and in different compartments.

The clinical presentation of tick-borne encephalitis virus (TBEV) infection varies from asymptomatic to severe meningoencephalitis or meningoencephalomyelitis. The TBEV subtype has been suggested as one of the most important risk factors for disease severity, but TBEV genetic characterization is difficult. Infection is usually diagnosed in the post-viremic phase, and so relevant clinical samples of TBEV are extremely rare and, when present, are associated with low viral loads. To date, only two complete TBEV genomes sequenced directly from patient clinical samples are publicly available. The aim of this study was to develop novel protocols for the direct sequencing of the TBEV genome, enabling studies of viral genetic determinants that influence disease severity. We developed a novel oligonucleotide primer scheme for amplification of the complete TBEV genome. The primer set was tested on 21 clinical samples with various viral loads and collected over a 15-year period using the two most common sequencing platforms. The amplicon-based strategy was compared to direct shotgun sequencing. Using the novel primer set, we successfully obtained nearly complete TBEV genomes (>90% of genome) from all clinical samples, including those with extremely low viral loads. Comparison of consensus sequences of the TBEV genome generated using the novel amplicon-based strategy and shotgun sequencing showed no difference. We conclude that the novel primer set is a powerful tool for future studies on genetic determinants of TBEV that influence disease severity and will lead to a better understanding of TBE pathogenesis.

Information on febrile illness caused by tick-borne encephalitis virus (TBEV) without central nervous system involvement is limited. We characterized 98 patients who had TBEV RNA in their blood but no central nervous system involvement at the time of evaluation. Median duration of illness was 7 days; 37 (38%) patients were hospitalized. The most frequent findings were malaise or fatigue (98%), fever (97%), headache (86%), and myalgias (54%); common laboratory findings were leukopenia (88%), thrombocytopenia (59%), and abnormal liver test results (63%). During the illness, blood leukocyte counts tended to improve, whereas thrombocytopenia and liver enzymes tended to deteriorate. At the time of positive PCR findings, 0/98 patients had serum IgG TBEV and 7 serum IgM TBEV; all patients later seroconverted. Viral RNA load was higher in patients with more severe illness but did not differ substantially in relation to several other factors. Illness progressed to tick-borne encephalitis in 84% of patients within 18 days after defervescence.

Although anti-TBE vaccines are highly effective, vaccine breakthrough (VBT) cases have been reported. With increasing evidence for immune system involvement in TBE pathogenesis, we characterized the immune mediators reflecting innate and adaptive T and B cell responses in neurological and convalescent phase in VBT TBE patients. At the beginning of the neurological phase, VBT patients have significantly higher serum levels of several innate and adaptive inflammatory cytokines compared to healthy donors, reflecting a global inflammatory state. The majority of cytokines, particularly those associated with innate and Th1 responses, are highly concentrated in CSF and positively correlate with intrathecal immune cell counts, demonstrating the localization of Th1 and proinflammatory responses in CNS, the site of disease in TBE. Interestingly, compared to unvaccinated TBE patients, VBT TBE patients have significantly higher CSF levels of VEGF-A and IFN-β and higher systemic levels of neutrophil chemoattractants IL-8/CXCL8 and GROα/CXCL1 on admission. Moreover, serum levels of IL-8/CXCL8 and GROα/CXCL1 remain elevated for two months after the onset of neurological symptoms, indicating a prolonged systemic immune activation in VBT patients. These findings provide the first insights into the type of immune responses and their dynamics during TBE in VBT patients. An observed systemic upregulation of neutrophil derived inflammation in acute and convalescent phase of TBE together with highly expressed VEGF-A could contribute to BBB disruption that facilitates the entry of immune cells and supports the intrathecal localization of Th1 responses observed in VBT patients., Competing Interests: PB served on the scientific advisory board for Pfizer on TBE CEE expert meeting 2020. KS served on the scientific advisory board for Roche for development of Lyme disease serological diagnostics received support by grant from MGH-ECOR. FS served on the scientific advisory board for Roche on Lyme disease serological diagnostics and the scientific advisory board for Pfizer on TBE CEE expert meeting 2020, has been a member of Pfizer Lyme Vaccine Licensure Advisory Board, received research support from the Slovenian Research Agency [grant number P3-0296], and is an unpaid member of the steering committee of the ESCMID Study Group on Lyme Borreliosis/ESGBOR. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Pavletič, Korva, Knap, Bogovič, Lusa, Strle, Nahtigal Klevišar, Vovko, Tomažič, Lotrič-Furlan, Strle and Avšič-Županc.)

This study assessed cost-effectiveness of a potential anti-tick vaccine that would protect against both Lyme borreliosis (LB) and tick-borne encephalitis (TBE) in a highly endemic setting of Slovenia. A Markov model was developed to estimate cost-effectiveness of a vaccine with potential combined protection against LB and TBE from the societal perspective. The model expressed time in annual cycles, followed a target population through their lifetime, and applied an annual discounting of 3%. A target population entered the model in a susceptible state, with time dependent probabilities to acquire LB/TBE. Disease manifestations were either resolved within one cycle, or a patient developed LB/TBE sequelae. The vaccination consisted of initial immunization and one revaccination. Estimates of LB/TBE direct and indirect costs, and data on natural course of LB/TBE were obtained from Slovenian databases. Effectiveness of the vaccine with potential combined protection against LB/TBE was derived from studies on existing TBE and LB vaccines, while utility estimates were collected from various literature sources. A vaccine with potential combined protection against LB/TBE was predicted to have an incremental cost of €771,300 per 10,000 vaccinated persons, an incremental utility of 17QALYs and a base-case incremental cost-effectiveness ratio (ICER) of 46,061€/QALY. Vaccine cost, effectiveness and discount rates were identified as the most influential model parameters. A wholesale price for a vaccine shot of €9.13 would lead to cost savings followed by health gains for the vaccination strategy. The base-case ICER was below commonly accepted thresholds of cost-effectiveness, indicating that a combined LB/TBE vaccine might be a cost-effective option in Slovenia. With early Health Technology Assessment becoming increasingly important, this analysis still represents a rare example of cost-effectiveness assessment prior to market authorisation. Although obviously in such a situation some key parameters are unknown, our model sets up a tool to analyse pharmacoeconomic criteria that can help development of a cost-effective health technology, in this case a combined tick-borne diseases vaccine., (Copyright © 2018 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Background: Information on parameters associated with the severity of tick-borne encephalitis (TBE) is limited., Methods: The association between 15 pre-defined parameters and the severity of TBE was evaluated in 717 consecutive adult patients diagnosed in Slovenia 2007-2012., Results: Multivariable logistic regression showed that patient age (odds ratio, OR 1.26, 95% CI 1.11-1.44; P = 0.001), previous vaccination against TBE (OR 14.23, 95% CI 1.72-117.87; P = 0.014), blood leukocyte count (OR 1.45, 95% CI 1.13-1.85; P = 0.004), and level of specific TBE virus serum IgG antibodies (OR 0.85, 95% CI 0.75-0.96; P = 0.009) were associated with severe acute illness based on the clinical diagnosis. When severity of TBE was based on the severity score and linear regression was used, corresponding association was found for age (estimated coefficient, EC 1.70, 95% CI 1.06-2.33; P<0.001), previous vaccination against TBE (EC 11.16, 95% CI 5.05-17.27; P < 0.001), serum C-reactive protein level (EC 1.20, 95% CI 0.48-1.91; P = 0.001), and level of specific TBE virus serum IgG antibodies (EC -0.74, 95% CI -1.27-0.20; P = 0.007)., Conclusions: Previous vaccination against TBE, low levels of TBE virus serum IgG antibodies, older age, higher blood leukocyte count, and higher serum C-reactive protein levels are associated with more severe TBE., (Copyright © 2018. Published by Elsevier Ltd.)

Objectives: Although statins have anti-inflammatory and potentially also antimicrobial (including antiviral) activity, their therapeutic impact on infectious diseases is controversial. In this study, we evaluated whether pre-existing statin use influenced the course and outcome of tick-borne encephalitis., Methods: To assess the influence of statin usage on the severity of acute illness and the outcome of tick-borne encephalitis, univariate and multivariable analyses were performed for 700 adult patients with tick-borne encephalitis of whom 77 (11%) were being treated with statins, and for 410 patients of whom 53 (13%) were receiving statins, respectively., Results: Multivariable analyses found no statistically significant association between statin usage and having a milder acute illness. There was also no statistically significant benefit with respect to a favorable outcome defined by the absence of post-encephalitic syndrome (ORs for a favorable outcome at 6 months was 0.96, 95% CI: 0.46-2.04, P = 0.926; at 12 months 0.29, 95% CI: 0.06-1.33, P = 0.111; at 2-7 years after acute illness 0.44, 95% CI: 0.09-2.22, P = 0.321), by a reduction in the frequency of six nonspecific symptoms (fatigue, myalgia/arthralgia memory disturbances, headache, concentration disturbances, irritability) occurring during the 4 week period before the last examination, or by higher SF-36 scores in any of the eight separate domains of health as well as in the physical and mental global overall component. Furthermore, there were no significant differences between patients receiving statins and those who were not in the cerebrospinal fluid or serum levels for any of the 24 cytokines/chemokines measured., Conclusions: In this observational study, we could not prove that pre-existing use of statins affected either the severity of the acute illness or the long-term outcome of tick-borne encephalitis., Competing Interests: Gary P. Wormser reports receiving research grants from Immunetics, Inc., Institute for Systems Biology, Rarecyte, Inc., and Quidel Corporation. He owns equity in Abbott/AbbVie; has been an expert witness in malpractice cases involving Lyme disease; and is an unpaid board member of the American Lyme Disease Foundation. Franc Strle is an unpaid member of the steering committee of the ESCMID Study Group on Lyme Borreliosis/ESGBOR. All the other authors have declared that no competing interests exist. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

We determined levels of tick-borne encephalitis (TBE) virus (TBEV) RNA in serum samples obtained from 80 patients during the initial phase of TBE in Slovenia. For most samples, levels were within the range of 3-6 log 10 copies RNA/mL. Levels were higher in female patients than in male patients, but we found no association between virus load and several laboratory and clinical parameters, including severity of TBE. However, a weak humoral immune response was associated with a more severe disease course, suggesting that inefficient clearance of virus results in a more serious illness. To determine whether a certain genetic lineage of TBEV had a higher virulence potential, we obtained 56 partial envelope protein gene sequences by directly sequencing reverse transcription PCR products from clinical samples of patients. This method provided a large set of patient-derived TBEV sequences. We observed no association between phylogenetic clades and virus load or disease severity.

Background: Information on the long-term outcome of tick-borne encephalitis (TBE) is limited., Objectives: To assess the frequency and severity of post-encephalitic syndrome (PES) at different time points after TBE, and to determine the parameters associated with unfavourable outcome., Methods: Adult patients diagnosed with TBE in Slovenia in the period 2007-2012 were followed-up for 12 months and also examined 2-7 years after TBE. Each patient was asked to refer a person of similar age without a history of TBE to serve as control., Results: A total of 420 patients and 295 control persons participated in the study. The proportion of patients with PES (defined as the presence of ≥ 2 subjective symptoms that newly developed or worsened since the onset of TBE and which had no other known medical explanation, and/or ≥ 1 objective neurological sign) was higher (P < 0.001) at the follow-up visit 6 months after the acute illness (127/304, 42%, 95% CI: 36-47%) than at 12 months (68/207, 33%, 95% CI: 26-40%); the proportion at 12 months was the same as at 2-7 years after TBE (137/420, 33%, 95% CI: 28-37%). However, the proportion of severe PES at the last two time points differed (9.7% vs 4.3%, P = 0.008). Multivariate logistic regression showed that unfavourable outcome at 6 months was associated with CSF leukocyte count (OR = 1.003, 95% CI: 1.001-1.005%, P = 0.017), at 12 months with the disease outcome at 6 months (OR = 115.473, 95% CI: 26.009-512.667%, P < 0.001), and at the final visit with disease outcome at 6 months (OR = 3.808, 95% CI: 1.151-12.593%, P = 0.028) and 12 months (OR = 26.740, 95% CI: 8.648-82.680%, P < 0.001). Unspecific symptoms that occurred within the four weeks before the final examination were more frequent and more constant in patients than in the control group., Conclusions: The frequency of PES diminished over time and stabilized 12 months after the acute illness, whereas the severity of PES continued to decline. Unfavourable outcomes at 12 months and at the final visit were strongly associated with the presence of PES at previous time points., (Copyright © 2017 Elsevier GmbH. All rights reserved.)

Background and Purpose: Tick-borne encephalitis (TBE) is an infection of the central nervous system (CNS) caused by tick-borne encephalitis virus (TBEV) and transmitted by ticks, with a variety of clinical manifestations. The incidence of TBE in Europe is increasing due to an extended season of the infection and the enlargement of endemic areas. Our objectives are to provide recommendations on the prevention, diagnosis and management of TBE, based on evidence or consensus decisions., Methods: For systematic evaluation, the literature was searched from 1970 to 2015 (including early online publications of 2016), and recommendations were based on evidence or consensus decisions of the Task Force when evidence-based data were not available., Recommendations: Vaccination against TBE is recommended for all age groups above 1 year in highly endemic areas (≥5 cases/100 000/year), but also for individuals at risk in areas with a lower incidence. Travellers to endemic areas should be vaccinated if their visits will include extensive outdoor activities. Post-exposure prophylaxis after a tick bite is not recommended. A case of TBE is defined by the presence of clinical signs of meningitis, meningoencephalitis or meningoencephalomyelitis with cerebrospinal fluid (CSF) pleocytosis (>5 × 10 6 cells/l) and the presence of specific TBEV serum immunoglobulin M (IgM) and IgG antibodies, CSF IgM antibodies or TBEV IgG seroconversion. TBEV-specific polymerase chain reaction in blood is diagnostic in the first viremic phase but it is not sensitive in the second phase of TBE with clinical manifestations of CNS inflammation. Lumbar puncture should be performed in all patients with suspected CNS infection unless there are contraindications. Imaging of the brain and spinal cord has a low sensitivity and a low specificity, but it is useful for differential diagnosis. No effective antiviral or immunomodulating therapy is available for TBE; therefore the treatment is symptomatic. Patients with a potentially life threatening meningoencephalitis or meningoencephalomyelitis should be admitted to an intensive care unit. In the case of brain oedema, analgosedation should be deepened; osmotherapy and corticosteroids are not routinely recommended. If intracranial pressure is increased, therapeutic hypothermia or decompressive craniectomy might be considered. Seizures should be treated as any other symptomatic epileptic seizures., Conclusions: Tick-borne encephalitis is a viral CNS infection that may result in long-term neurological sequelae. Since its incidence in Europe is increasing due to broadening of endemic areas and prolongation of the tick activity season, the health burden of TBE is enlarging. There is no effective antiviral treatment for TBE, but the disease may be effectively prevented by vaccination., (© 2017 EAN.)

Background: Information on tick-borne encephalitis (TBE) in patients already vaccinated against the disease is limited., Objectives: To compare the course and outcome in patients with vaccination breakthrough TBE with findings in patients who developed TBE without previous vaccination., Methods: All adult patients diagnosed with TBE at a single medical centre during a 16-year period and who had received at least two doses of TBE vaccine before the onset of illness qualified for the study. For each patient with breakthrough TBE, two unvaccinated sex- and age-matched patients, diagnosed with TBE in the same year, were included for comparison., Results: Amongst 2332 patients diagnosed with TBE in the period 2000-2015, 39 (1.7%) had been vaccinated against the disease. Their median age was 59 (20-83) years; 22 of 39 (56.4%) were male. In comparison with unvaccinated patients with TBE, those with breakthrough disease more often experienced a monophasic course of illness (P = 0.006), had a higher CSF leucocyte count (P = 0.005), more often had urine retention (P = 0.012), more often needed ICU treatment (P = 0.009), were hospitalized for longer (P = 0.002) and had more severe acute illness (P = 0.004 for simple clinical assessment, P = 0.001 for severity score)., Conclusion: In addition to several findings corroborating previous results in patients with vaccination breakthrough TBE, such as older age and the presence of a particular specific serum antibody pattern indicating anamnestic response, findings in this study indicate that the acute illness in patients with breakthrough TBE is more severe than in unvaccinated sex- and age-matched patients who develop the disease., (© 2017 The Association for the Publication of the Journal of Internal Medicine.)

Background: Tick borne encephalitis is the most frequent vector-transmitted infectious disease of the central nervous system in Europe and Asia. The disease caused by European subtype of tick borne encephalitis virus has typically a biphasic clinical course with the second phase presenting as meningitis, meningoencephalitis, or meningoencephalomyelitis. Cerebrospinal fluid pleocytosis is considered a condition sine qua non for the diagnosis of neurologic involvement in tick borne encephalitis, which in routine clinical practice is confirmed by demonstration of serum IgM and IgG antibodies to tick borne encephalitis virus., Case Presentation: Here we present a patient from Slovenia, an area highly endemic for tick borne encephalitis, with encephalitis but without cerebrospinal fluid pleocytosis in whom tick borne encephalitis virus infection of the central nervous system was demonstrated., Conclusion: Cerebrospinal fluid pleocytosis is not mandatory in encephalitis caused by tick borne encephalitis virus. In daily clinical practice, in patients with neurologic symptoms/signs compatible with tick borne encephalitis and the risk of exposure to ticks in a tick borne encephalitis endemic region, the search for central nervous system infection with tick borne encephalitis virus is warranted despite the lack of cerebrospinal fluid pleocytosis.

Lyme borreliosis (LB), tick-borne encephalitis (TBE) and human granulocytic anaplasmosis (HGA) are endemic in central part of Slovenia. We tested the hypothesis that patients with erythema migrans (EM) from this region, who have leukopenia and/or thrombocytopenia (typical findings in HGA and in the initial phase of TBE but not in patients with LB) are coinfected with Anaplasma phagocytophilum and/or with TBE virus, i.e. that cytopenia is a result of concomitant HGA or the initial phase of TBE. Comparison of clinical and laboratory findings for 67 patients with EM who disclosed leukopenia/thrombocytopenia with the corresponding results in sex- and age-matched patients with EM and normal blood cell counts revealed no differences. In addition, patients with typical EM and leukopenia and/or thrombocytopenia tested negative for the presence of IgM and IgG antibodies to TBE virus by ELISA as well as for the presence of specific IgG antibodies to A. phagocytophilum antigens by IFA in acute and convalescent serum samples. Thus, none of 67 patients (95% CI: 0 to 5.3%) with typical EM (the presence of this skin lesion attests for early Lyme borreliosis and is the evidence for a recent tick bite) was found to be coinfected with A. phagocytophilum or had a recent primary infection with TBE virus. The findings in the present study indicate that in Slovenia, and probably in other European countries endemic for LB, TBE and HGA, patients with early LB are rarely coinfected with the other tick-transmitted agents.

The aim of the present study was to quantify the severity of acute illness in patients with tick-borne encephalitis and to ascertain this approach by comparing it to standard clinical assessment. We designed scoring system for quantification of the severity of acute illness in patients with tick-borne encephalitis. Certain number of points was allotted to the presence, intensity, and duration of individual symptoms/signs. According to the obtained score the disease was classified as mild, moderate, and severe. Tick-borne encephalitis was assessed clinically as mild when only signs/symptoms of meningeal involvement were found, moderate in case of monofocal neurological signs and/or mild to moderate signs/symptoms of central nervous system dysfunction, and severe in patients with multifocal neurological signs and/or symptoms of severe dysfunction of central nervous system. By designed scoring system 282 adult patients, 146 males and 136 females, average aged 52.2 ± 15.5 years (range 15-82 years), with confirmed tick-borne encephalitis, were prospectively assessed. In 279/282 (98.9%) patients the severity according to clinical assessment matched with the score ranges for mild, moderate, and severe disease. The proposed approach enables precise and straightforward appraisal of the severity of acute illness and could be useful for comparison of findings within/between study groups.

Tick-borne encephalitis (TBE) developed in 3 persons in Slovenia who drank raw milk; a fourth person, who had been vaccinated against TBE, remained healthy. TBE virus RNA was detected in serum and milk of the source goat. Persons in TBE-endemic areas should be encouraged to drink only boiled/pasteurized milk and to be vaccinated.

Although tick-borne encephalitis (TBE) has been recognized in Europe for more than 70 years and has been the topic of numerous reports, information on the involvement of facial nerves in the course of the disease is limited. Our study conducted at a single medical centre revealed that facial nerve involvement in the course of TBE in Central Europe is (i) infrequent--it was found in only 11 of 1218 (0.9%) consecutive adult patients diagnosed with TBE; (ii) manifests with unilateral or rarely bilateral peripheral facial palsy (PFP) (nine and two patients, respectively); (iii) appears late in the course of acute illness--in our patients 10-20 days after the onset of the meningoencephalitic phase of TBE, and often after defervescence (in 8/11 patients; 6-13 days after normalization of body temperature); (iv) develops more often in patients with more severe illness, i.e. more frequently in those with encephalitic than in those with meningitic clinical presentation, and more commonly in patients with monophasic than biphasic illness; and (v) has a favourable outcome--our patients had a clinically complete recovery from PFP within 7-90 (median 30) days after its onset. Moreover, the finding of Borrelia infection in 3/11 (27.3%) patients (diagnosis of confirmed Lyme neuroborreliosis was established in 1/11 patients and two patients fulfilled criteria for possible Lyme neuroborreliosis) suggests that in countries where TBE and Lyme borreliosis are endemic, concomitant infection with Borrelia burgdorferi sensu lato should be considered and searched for in patients who develop PFP in the course of TBE., (© 2011 The Authors. Clinical Microbiology and Infection © 2011 European Society of Clinical Microbiology and Infectious Diseases.)

Tick-borne encephalitis is a zoonosis, endemic in a vast area of Europe and Asia. Clinical spectrum of the disease ranges from mild meningitis to severe meningoencephalitis with or without paralysis. Rare clinical manifestations are an abortive form of the disease and a chronic progressive form. A post-encephalitic syndrome, causing long-lasting morbidity that often affects the quality of life and sometimes also forces the individual to a change in lifestyle, develops in 35-58% of patients after acute tick-borne encephalitis. Clinical course and outcome vary by subtype of tick-borne encephalitis virus causing infection. Severity of the disease increases with the age of patients. The risk of incomplete recovery is higher for patients who have more severe clinical illness during acute stage of tick-borne encephalitis., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

One of the primary goals of the 11th Annual Meeting of the International Scientific Working Group on Tick-borne encephalitis (ISW-TBE) held in 2009 was to develop the first update of the Position Paper on TBE in Golden Agers, summarizing the most essential aspects of the disease in this age group. TBE morbidity has continued to increase in recent years, which is thought to be due to an interplay of social, political, ecological, economic and demographic factors combined with climate changes. Today's golden agers i.e. individuals aged 50 years or above, are healthier and more mobile, lead more active lifestyles and spend more time travelling and performing outdoor leisure activities. This places them at an increased risk of infection. At the same time, increasing age is associated with a quantitative and qualitative decline in innate and adaptive immunity, which is why elderly individuals are more susceptible to infection and severe disease than younger people. Also, their response to vaccination tends to be slower, antibody titres generally reach lower levels and titres tend to decrease earlier than in younger individuals. Evidence is accumulating that this is also the case with TBE vaccination, emphasizing the importance of administering the first TBE booster vaccination no later than 3 years after the completion of primary immunization or at an even shorter interval. Encouragingly, recent data have shown that the field effectiveness of TBE vaccination exceeds 97%, with no significant differences between age groups.

Objective: To present epidemiological data and clinical characteristics of tick-borne encephalitis (TBE) in adult patients, and to compare findings in the subgroup over the age of 60 years with those aged 60 or under., Methods: The information for this retrospective study was obtained by review of medical documentation. All patients over 15 years of age hospitalized at the Department of Infectious Diseases, University Medical Center Ljubljana, Slovenia, between 2000 and 2004 with pleocytosis (cerebrospinal fluid leukocyte count >5 x 10(6) cells/l) and the presence of serum IgM antibodies against TBE virus qualified for inclusion in this report. Patients were divided into two groups according to their age (patients over the age of 60 were classified as seniors and those aged 60 or under as adults); the findings in the two groups were compared., Results: Of 448 patients with TBE, 318 were in the adult group and 130 in the senior group. Males predominated in both groups. A biphasic course of the illness was reported by 56% of patients. There were no significant differences in the majority of clinical parameters in the initial phase of TBE but several distinctions between adults and seniors were found in the second phase of the illness. Adults more often presented with fever, headache, stiff neck and photophobia, whereas seniors more frequently reported fatigue, altered consciousness and decreased muscle strength, these differences indicating a more classic course of TBE in the younger group and a somehow different and more severe acute disease in the older group. More severe acute disease and less favorable outcome in seniors was further corroborated by the occurrence of urine retention (18/318, 5.7% versus 27/130, 20.8%; P < 0.001), frequency of pareses (10/318, 3.1% versus 7/130, 5.4%; P = 0.002) and the need for antiedematous treatment (103/318, 32.4% versus 61/130, 46.9%; P = 0.005), as well as by the duration of treatment, duration of hospital stay and the death rate (0/318 versus 3/130, 2.3%; P = 0.024). Several distinctions were present also in laboratory findings, including higher cerebrospinal fluid leukocyte count in the adults than in the seniors (107 x 10(6) cells/l versus 47 x 10(6) cells/l; P < 0.001)., Conclusion: Direct comparison of the course and outcome of TBE revealed several distinctions between patients over 60 years of age and those aged 60 or under and corroborates previous assumptions that TBE is a more serious illness in the elderly population.

The aim of this prospective study was to assess the value of procalcitonin (PCT) level and serum concentration of C-reactive protein (CRP) in differentiating viral from bacterial infection in selected groups of patients, including those with acute human granulocytic anaplasmosis (HGA), which is caused by an intracellular bacteria Anaplasma phagocytophilum, and patients with the initial phase of tick-borne encephalitis (TBE), which is a viral disease caused by an RNA virus belonging to the Flavivirus genus of the family Flaviviridae.

Background: Tick-borne encephalitis virus (TBEV) is one of the most important causes of human viral infections of the central nervous system in Europe. Currently, the diagnosis of TBE is based on the demonstration of specific antibodies in patient's serum, which appear only several weeks after the infection., Objective: To determine how successfully can viral RNA be detected by RT-PCR in the samples of body fluids of patients with TBE prior to and after the appearance of antibodies., Study Design: Serum, whole blood and CSF samples from 34 patients with a serologically confirmed TBE were collected. Samples were tested for the presence of TBEV RNA by using RT-PCR method., Results: Viral RNA was detected in all blood and serum samples collected before the development of antibodies. After the appearance of IgM antibodies, the number of positive samples dropped by at least one third. After the development of IgG antibodies, only 3% of serum and 16% of blood samples tested positive for viral RNA. Samples of cerebrospinal fluid were shown to be inappropriate for the molecular diagnosis of TBE using this assay, since only one sample (10%) that was collected in the sero-negative phase of disease was found positive by the PCR assay., Conclusions: RT-PCR is an efficient method for an early detection of TBEV in blood and serum samples collected prior to the appearance of antibodies. This method can be of valuable use for a differential diagnosis of TBEV infection in patients with febrile illness after a tick bite, particularly in regions where more than one tick-transmitted diseases are endemic.

We report a patient with febrile illness and epidemiologic and clinical findings consistent with human granulocytic ehrlichiosis and tickborne encephalitis, in whom infection with Anaplasma phagocytophilum was demonstrated by polymerase chain reaction and seroconversion. Tickborne encephalitis virus infection was established by serum immunoglobulin (Ig) M and IgG antibodies.

Tick-borne encephalitis (TBE) is a communicable disease caused by a flavi-virus, ticks being the main vectors. The nervous system is affected, four clinical features of different severity are observed: meningitis, meningoencephalitis, meningoencephalomyelitis, meningoradiculoneuritis. TBE is a preventable disease, which is rapidly becoming a growing public health problem in Europe. So far no causal treatment is possible but an efficient, safe vaccination is available. During the 6th meeting of the International Scientific Working Group on TBE with the main conference issue "Tick-borne encephalitis in childhood" an international consensus was achieved. In countries where TBE is endemic--and not prevented by immunization--both children and adults are affected. The disease in children is generally milder, although severe illness may occur and even lead to permanent impairment of the quality of life due to neuropsychological sequelae. Therefore immunization should be offered to all children living in or traveling to endemic areas.

Background: To establish the etiology in Slovenian children with febrile illnesses occurring after a tick bite., Methods: Eighty-six febrile patients younger than 15 years referred to our institution in 2001 with a history of a tick bite within 6 weeks before onset of the illness were included in this prospective study. Acute and convalescent serum samples were tested for the presence of antibodies to tick-borne encephalitis virus, Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum, Ehrlichia chaffeensis, Rickettsia conorii, Babesia microti, Bartonella henselae, Bartonella quintana and Francisella tularensis. Cerebrospinal fluid was investigated in patients in whom meningeal involvement was clinically suspected. Blood and/or cerebrospinal fluid from the patients were cultured in modified Kelly-Pettenkofer medium. PCR was performed to detect ribosomal DNA of A. phagocytophilum and E. chaffeensis., Results: Of 86 patients 33 (38%) were excluded because a well-defined febrile illness not associated with tick bite was established. Tick-borne illness was diagnosed in 28 (53%) of the 53 remaining patients. The most common diagnosis was tick-borne encephalitis (64%), followed by Lyme borreliosis (46%), human monocytic ehrlichiosis and human granulocytic ehrlichiosis (serologic evidence of infection in 9 and 4%, respectively). In 6 (21%) patients there was evidence for infection with more than 1 tick-borne agent., Conclusions: Tick-borne illness was established in 53% of the patients younger than 15 years presenting with febrile illness occurring within 6 weeks after a tick bite. The most common identified illnesses were tick-borne encephalitis and Lyme borreliosis.

Tick-borne encephalitis (TBE) is one of the most important human infections of the central nervous system (CNS) and is endemic in several European countries, including a large part of Slovenia. In at least two-thirds of patients who develop CNS involvement, the disease has a characteristic biphasic course. Seroepidemiological studies on TBE virus infection in endemic areas of various European countries have demonstrated that asymptomatic infections are common. In some of these reports it was also suggested that there is an abortive form of TBE virus infection, which is manifested only by a febrile headache without meningeal involvement (i.e., the initial phase of illness without subsequent CNS involvement) and that it represents more than half of the cases of clinically manifested infection with TBE virus. The aim of this report was to evaluate patients who presented with the initial phase of TBE and monitor them for the appearance of the second, encephalitic phase of the disease. In 56/205 (27.3%) patients with febrile illness occurring after a tick bite, infection with TBE virus was demonstrated by the appearance of specific IgM and IgG antibodies against TBE virus during a follow-up period of 6 weeks. All 56 patients were diagnosed during the initial phase of TBE, however, only 1/56 (1.8%) had an isolated initial phase of TBE without subsequent CNS involvement, whereas 55/56 (98.2%) patients developed a clinically biphasic course of illness with CSF abnormalities (pleocytosis) during the second phase of the disease. Detailed epidemiological, clinical and laboratory characteristics of this patient with an abortive form of TBE virus infection are presented. The results of our study support the view that the abortive form of central European TBE is a rare clinical manifestation of TBE virus infection.

Objective: To establish epidemiological, clinical and laboratory differences between adult patients with proven acute human granulocytic ehrlichiosis (HGE) and patients with the initial phase of tick-borne encephalitis (TBE)., Methods: Epidemiological, clinical and laboratory findings were compared in nine patients with acute HGE (established by the presence of specific DNA sequences of Ehrlichia phagocytophila in whole blood by polymerase chain reaction and/or by seroconversion or at least a four-fold change of serum antibody titres to E. phagocytophila by indirect immunofluorescence assay) and 29 patients with the initial phase of TBE (demonstrated in ELISA tests by the presence of serum IgM antibodies to TBE virus)., Results: Findings were similar for the majority of the general parameters examined, which included sex, age, incubation period, duration of fever, and frequency of additional tick bites. However, a statistically significant difference was found for the duration of fever before the first visit (median 7 days in patients with acute HGE and 4 days in patients with the initial phase of TBE; p = 0.0169), and for the frequency of hospitalisation, which was higher for patients with the initial phase of TBE (29/29) than for those with acute HGE (5/9; p = 0.0017). Comparison of clinical signs and symptoms and laboratory findings in the two groups revealed significant differences: in patients with acute HGE there was a higher frequency of chills (4/9 versus 3/29, respectively; p = 0.0407), myalgia (8/9 versus 13/29, respectively; p = 0.0263), and arthralgia (7/9 versus 3/29, respectively; p = 0.0003), and elevated values of lactate dehydrogenase (7/9 versus 3/29, respectively; p = 0.0003) and concentration of C-reactive protein (9/9 versus 6/29, respectively; p = 0.0000)., Conclusions: In a patient with febrile illness occurring after a tick bite, a clinical report of chills, myalgia and arthralgia, and laboratory findings of elevated values for lactate dehydrogenase and concentration of C-reactive protein direct towards a diagnosis of acute HGE rather than the initial phase of TBE.

The limited information on co-infection with Borrelia burgdorferi sensu lato and tick-borne encephalitis (TBE) virus was a stimulus for presentation of two patients with well-defined double infection of the central nervous system. TBE virus and B. burgdorferi sensu lato infections are searched for in all patients with lymphocytic meningitis and/or meningoencephalitis admitted to our department. During the last ten years we identified two patients who had ELISA IgM and IgG antibodies to TBE virus in serum and a positive PCR result for TBE virus in cerebrospinal fluid as well as B. burgdorferi sensu lato isolated from cerebrospinal fluid. Intrathecal production of borrelial antibodies was not proven in either of the two patients. These findings show that in patients with acute lymphocytic meningitis originating in regions endemic for Lyme borreliosis and TBE, the possibility of concomitant infection should be considered.

The aim of this prospective study was to compare epidemiological data and clinical features in children and adults with tick-borne encephalitis (TBE). Patients with aseptic meningitis diagnosed at the University Medical Centre, Department of Infectious Diseases, Ljubljana, Slovenia, from June to August 1997, in whom the diagnosis of TBE was ascertained by the presence of serum IgM antibodies against TBE virus, who were serologically negative for Borrelia burgdorferi sensu lato and had a negative PCR CSF result on enteroviral infection, were included in the study. Out of 213 patients with aseptic meningitis, 80 (37.56%) fulfilled inclusion criteria. There were 20 children and 60 adults. In both groups males predominated. Virtually all patients had headache and fever, and more than 50% suffered from vomiting. The majority of patients in both groups recalled a tick bite, had a biphasic course of the illness, and was found to have obviously expressed meningeal signs. In both groups the median CSF leukocyte count was somewhat lower than 100 x 10(6)/l with a predominance of lymphocytes. Children were more often given antibiotics during the initial phase of TBE than adults (p = 0.0095). Several other statistically significant distinctions (p < 0.05) were found including the frequency of fatigue, malaise, vertigo, photophobia, myalgias, arthralgias, as well as elevated CSF albumin and protein concentration, elevated albumin quotient and IgG quotient; all these findings were more often present in adults. In addition a longer duration of fever, more frequent need for anti-edematous treatment and longer hospitalization were found in adults. Direct comparison of clinical and epidemiological characteristics of TBE in children and adults revealed differences in several clinical and laboratory features and corroborates the previous conclusion that TBE in childhood is a milder illness than TBE in adults.

Objectives: The aim of our study was to establish clinical and laboratory differences between patients with acute human granulocytic ehrlichiosis (HGE) and patients with the initial phase of tick-borne encephalitis (TBE)., Methods: Clinical features and laboratory results of four patients with acute HGE (established by the presence of the specific DNA sequences of the HGE agent in whole blood by polymerase chain reaction and/or by seroconversion to the HGE agent by indirect immunofluorescence assay) and 12 patients with the initial phase of TBE (demonstrated by the presence of serum IgM antibodies to TBE virus) were compared. All these patients were uncovered at the Department of Infectious Diseases, University Medical Centre, Ljubljana, Slovenia, during 1995-1996, in a prospective study on the aetiology of febrile illnesses occurring within 6 weeks after a tick bite., Results: Findings were similar for the majority of the examined parameters including severity of illness, level and duration of fever, presence of headache, leukopenia, thrombocytopenia, and liver - function test abnormalities. Statistically significant differences were found only for arthralgia (P=0.026) and elevated concentration of C-reactive protein (P=0.003); both variables were found more often in patients with acute HGE., Conclusions: In a patient residing in the central part of Slovenia, who reports a tick bite followed by a febrile illness with leukopenia and/or thrombocytopenia, the presence of arthralgias and/or an elevated C-reactive protein value directs toward the diagnosis of acute HGE and against the initial phase of TBE.

Alopecia occurring after febrile bacterial and viral infection is a phenomenon well known since the beginning of the century. To evaluate the occurrence of alopecia in tick transmitted disease, 23 adult patients with Lyme meningitis and 71 patients with tick-borne encephalitis were included in a prospective study and were followed up for one year. Diffuse alopecia occurred within three months after the outbreak of disease in 3 out of 23 (13%) patients with Lyme meningitis and in 40 out of 71 (56.3%) patients with tick-borne encephalitis. The mean duration of alopecia was 2 to 3 months and alopecia was reversible in all patients.

From September 1992 to August 1993, 338 patients over the age of 15 years presented to the Department of Infectious Diseases, University Medical Centre Ljubljana, with acute lymphocytic meningitis. In 89 of these patients (26.3%) serum IgM and IgG antibodies against tick-borne encephalitis (TBE) virus were detected, and in 59 patients (17.5%) a borrelial etiology of disease was demonstrated by one or more of the following presence of intrathecal antibody production, seroconversion to borrelial antigens, presence of erythema migrans, and/or isolation of Borrelia burgdorferi sensu lato from skin or cerebrospinal fluid. Of the 148 patients who fulfilled criteria for TBE or borrelial infection, concomitant infection with TBE virus and B. burgdorferi sensu lato was demonstrated in 12 patients (3.6% of all patients presenting with acute lymphocytic meningitis). In the majority of patients with concomitant infection the clinical features at presentation were characteristic of, or consistent with, TBE. In addition, during follow-up studies, eight of the 12 patients subsequently developed signs and symptoms compatible with minor and/or major manifestations of Lyme borreliosis. Six patients were diagnoses with neuroborreliosis based on signs or symptoms and/or laboratory tests. These findings show that in patients with acute lymphocytic meningitis or meningoencephalitis, originating in TBE and Lyme borreliosis endemic regions, the possibility of concomitant infection should be considered.

Cerebrospinal fluid lymphocyte subsets in patients with tickborne encephalitis (TBE) and in patients with TBE with concomitant neuroborreliosis (double infection) were analysed by flow cytometry. In the TBE group, higher percentages of CD4+DR+ T cells (p = 0.02) and CD25+ T cells (p = 0.0002) were observed, while in the group with double infection, higher percentages of CD19+ cells (p = 0.007), CD8+DR- T cells (p = 0.04), and CD3+CD71 + T cells (p = 0.0002) were found. It was concluded that several differences in immune cell parameters are present between the two groups of patients. Three variables (CD19+ cells, CD3+CD25+ T cells, CD3+CD71+ T cells) were included in the logistic regression model for calculation of probability for double infection. Flow cytometric characterisation of lymphocyte subsets in CSF can further substantiate the diagnosis of concomitant neuroborreliosis in patients with TBE.

The aim of this prospective study was to assess the frequency of thrombocytopenia and abnormal liver function tests in the initial phase of tick-borne encephalitis. In 1994, 248 adult patients presented at the Department of Infectious Diseases, University Medical Centre Ljubljana, with acute lymphocytic meningitis or meningoencephalitis and serologically confirmed tick-borne encephalitis virus infection. In 180/248 (72.6%) patients, typical biphasic course of the illness was found and 28/180 (15.6%) patients with biphasic course were examined in both phases of the illness. In 20 out of these 28 (71.4%) patients, thrombocytopenia and leukopenia were found initially, in one (3.6%) patient only leukopenia was recorded and three (10.7%) patients had thrombocytopenia without leukopenia. In four (14.3%) patients leukocyte and thrombocyte values were within the normal range. The lowest leukocyte number was 1.4 x 10(9)/l and the lowest recorded thrombocyte number was 60 x 10(9)/l. Abnormal liver function tests were discovered in four out of 18 patients tested (22.2%). In conclusion, in the initial phase of tick-borne encephalitis thrombocytopenia and abnormal liver function tests may be found. Thrombocytopenia is a common finding with a frequency similar to that of well-known leukopenia, while abnormal liver function tests are relatively rare.

One-hundred-seventy-five patients in whom bone marrow puncture had been performed at the Department of Infectious Diseases, University Medical Centre, Ljubljana, during the period from 1988 to 1992, were analysed in a retrospective study. In five out of these 175 patients, tick-borne encephalitis virus infection was confirmed by serological tests and in all of them bone marrow puncture was performed in the initial phase of the illness as part of diagnostic work-up in a patient with a febrile illness accompanied by leukopenia and thrombocytopenia. Bone marrow examination revealed minimal reactive changes or normal findings. In addition to leukopenia and thrombocytopenia, abnormal liver function tests were also found in four patients. All these patients later developed meningoencephalitis, i.e. they had clinically typical tick-borne encephalitis with biphasic course of the illness. In the initial phase of tick-borne encephalitis in addition to well-known leukopenia, thrombocytopenia and abnormal liver function tests may be found.