High habitat richness reduces the risk of tick-borne encephalitis in Europe: A multi-scale study

Background

The natural transmission cycle of tick-borne encephalitis (TBE) virus is enhanced by complex interactions between ticks and key hosts strongly connected to habitat characteristics. The diversity of wildlife host species and their relative abundance is known to affect transmission of tick-borne diseases. Therefore, in the current context of global biodiversity loss, we explored the relationship between habitat richness and the pattern of human TBE cases in Europe to assess biodiversity's role in disease risk mitigation.

Methods

We assessed human TBE case distribution across 879 European regions using official epidemiological data reported to The European Surveillance System (TESSy) between 2017 and 2021 from 15 countries. We explored the relationship between TBE presence and the habitat richness index (HRI1) by means of binomial regression. We validated our findings at local scale using data collected between 2017 and 2021 in 227 municipalities located in Trento and Belluno provinces, two known TBE foci in northern Italy.

Findings

Our results showed a significant parabolic effect of HRI on the probability of presence of human TBE cases in the European regions included in our dataset, and a significant, negative effect of HRI on the local presence of TBE in northern Italy. At both spatial scales, TBE risk decreases in areas with higher values of HRI.

Interpretation

To our knowledge, no efforts have yet been made to explore the relationship between biodiversity and TBE risk, probably due to the scarcity of high-resolution, large-scale data about the abundance or density of critical host species. Hence, in this study we considered habitat richness as proxy for vertebrate host diversity. The results suggest that in highly diverse habitats TBE risk decreases. Hence, biodiversity loss could enhance TBE risk for both humans and wildlife. This association is relevant to support the hypothesis that the maintenance of highly diverse ecosystems mitigates disease risk.

Elevated levels of serum muscle enzymes in the initial phase of tick-borne encephalitis

PURPOSE

Since some patients with tick-borne encephalitis (TBE) have pronounced myalgias, and since myositis is reported in Flavivirus diseases such as dengue, we performed systematic search for abnormalities of muscle enzymes in a group of patients in whom the presence of tick-borne encephalitis virus (TBEV) RNA in the first phase of the disease was demonstrated and who developed second phase of TBE.

METHODS

Total leukocyte and platelet blood counts were determined routinely at the initial examination during the first and the second phase of TBE. Activity of aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatine kinase (CK), myoglobin and troponin was determined from the available stored serum specimens; the first and second phase disease specimens were tested simultaneously.

RESULTS

Of 24 patients with biphasic course of TBE, 83% had leukopenia, 65% thrombocytopenia, 83% elevated AST and 4% elevated ALT level. Furthermore, 33% had elevated serum CK, 26% myoglobin and 22% troponin activity; at least one of the muscle enzymes was elevated in 42% of patients. Leukopenia, thrombocytopenia, elevated liver enzymes and elevations of CK and myoglobin were present in the initial phase but resolve later, while troponin abnormalities were also found in the second phase of TBE.

CONCLUSIONS

The present study exposes that in addition to previously known leukopenia, thrombocytopenia and increased liver enzymes activity, the initial phase of TBE is relatively often associated also with elevated muscle enzymes. Clinical relevance of these findings remains to be determined.

Web search volume as a near-real-time complementary surveillance tool of tick-borne encephalitis (TBE) in Italy

The Internet is an important gateway for accessing health-related information, and data generated through web queries have been increasingly used as a complementary source for monitoring and forecasting of infectious diseases and they may partially address the issue of underreporting. In this study, we assessed whether tick-borne encephalitis (TBE)-related Internet search volume may be useful as a complementary tool for TBE surveillance in Italy. Monthly Google Trends (GT) data for TBE-related information were extracted for the period between January 2017 and September 2022, corresponding to the available time series of TBE notifications in Italy. Time series modeling was performed by applying seasonal autoregressive integrated moving average (SARIMA) models with or without GT data. The search terms relative to tick bites reflected best the observed temporal distribution of TBE cases, showing a correlation coefficient of 0.81 (95 % CI: 0.71-0.88). Particularly, both the reported number of TBE cases and GT searches occurred mainly during the summer. The peak of disease notifications coincided with that of Google searches in 4 of 6 years. Once calibrated, SARIMA models with or without GT data were applied to a validation set. Retrospective forecast made by the model with GT data was associated with a lower prediction error and accurately predicted the peak timing. By contrast, the traditional SARIMA model underestimated the actual number of TBE notifications by 65 %. Timeliness, easy availability, low cost and transparency make monitoring of the TBE-related Internet search queries a promising addition to the traditional methods of TBE surveillance in Italy.

A brief tale of two pioneering moments: Europe's first discovery of Tick-Borne Encephalitis (TBE) virus beyond the Soviet Union and the largest alimentary TBE outbreak in history

The emergence of tick-borne encephalitis (TBE) in Europe marked several significant milestones. The discovery of TBE in Czechoslovakia in 1948, with Gallia and Krejčí simultaneously isolating the TBE virus (TBEV) from human samples for the first time in Europe outside the Soviet Union, was pivotal. Subsequent TBEV isolation from ticks suggested the viral transmission via this vector. In 1951, the outbreak in Rožňava in Slovakia (Czechoslovakia) revealed an unexpected mode of transmission, unpasteurized milk from a local dairy, challenging existing understanding. Investigations exposed illicit practices of mixing cow's milk with goat's milk for economic gains. Laboratory research confirmed the outbreak was caused by TBEV, which was substantiated by serological analyses. This was the first and largest documented alimentary TBE outbreak in history. In this review, we delve into both published sources and unpublished archival data, offering a comprehensive understanding of these historic accomplishments and shedding light on these pivotal moments.

Proteomic and metabolomic analysis of the serum of patients with tick-borne encephalitis

Tick-borne encephalitis virus (TBEV) is a common virus in Europe and Asia, causing around 10,000 to 10,500 infections annually. It affects the central nervous system and poses threats to public health. However, the exact molecular mechanisms of TBE pathogenesis are not yet fully understood due to the complex interactions between the virus and its host. In this study, a comprehensive analysis was conducted to characterize the serum metabolome and proteome of adult patients infected with TBEV, in comparison to a control group of healthy individuals. Liquid chromatography tandem mass spectrometry (LC-MS) was employed to monitor metabolic and proteomic alternations throughout the progression of the disease, significant physiological changes associated with different stages of the disease were identified. A total of 44 proteins and 115 metabolites exhibited significantly alternations in the sera of patients diagnosed with TBE. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses of these metabolites and proteins revealed differential enrichment of genes associated with the extracellular matrix, complement binding, hemostasis, lipid metabolism, and amino acid metabolism between TBE patients and healthy controls. We gained valuable understanding of the specific metabolites implicated in the host's responses to TBE, establishing a basis for further research on TBE disease. SIGNIFICANCE: The current investigation revealed a comprehensive and systematic differences on TBE using LC-MS platform from human serum samples of TBE patients and healthy individuals providing the immune response to the invasion of TBE.

Phase 3 immunogenicity and safety study of a tick-borne encephalitis vaccine in healthy Japanese participants 1 year of age and older

BACKGROUND

Tick-borne encephalitis (TBE) virus infects the central nervous system and may lead to severe neurological complications or death. This study assessed immunogenicity, safety, and tolerability of TBE vaccine in Japanese participants 1 year of age and older.

METHODS

This phase 3, multicenter, single-arm, open-label study was conducted in Japanese adult (≥ 16 years) and pediatric (1-< 16 years) populations. Participants received a single 0.5-mL (adult) or 0.25-mL (pediatric) dose of TBE vaccine at each of 3 visits. The primary endpoint was the proportion of participants who were seropositive (neutralization test [NT] titer ≥ 1:10) 4 weeks after Dose 3. Secondary and exploratory endpoints included NT seropositivity rates 4 weeks after Dose 2, immunoglobulin G (IgG) seropositivity 4 weeks after Doses 2 and 3, NT geometric mean titers (GMTs), IgG geometric mean concentrations (GMCs), and geometric mean fold rises. Primary safety endpoints were frequencies of local reactions, systemic events, adverse events (AEs), and serious AEs.

RESULTS

Among 100 adult and 65 pediatric participants, 99.0 % and 100.0 % completed the study, respectively. NT seropositivity was achieved in 98.0 % adult and 100.0 % pediatric participants after Dose 3; seropositivity after Dose 2 was 93.0 % and 92.3 %, respectively. In both age groups, IgG seropositivity was ≥ 90.0 % and ≥ 96.0 % after Doses 2 and 3, respectively; GMTs and GMCs were highest 4 weeks after Dose 3. Reactogenicity events were generally mild to moderate in severity and short-lived. AEs were reported by 15.0 % (adult) and 43.1 % (pediatric) of participants. No life-threatening AEs, AEs leading to discontinuation, immediate AEs, related AEs, or deaths were reported. No serious AEs were considered related to TBE vaccine.

CONCLUSIONS

TBE vaccine elicited robust immune responses in Japanese participants 1 year of age and older. The 3-dose regimen was safe and well tolerated, and findings were consistent with the known safety profile of this TBE vaccine.

CLINICALTRIALS

gov: NCT04648241.

Paretic complications of tick-borne encephalitis and Lyme neuroborreliosis in the Czech Republic: Characteristics and clinical outcome

Tick-borne encephalitis (TBE) and Lyme neuroborreliosis (LNB), the most common tick-borne diseases of the central nervous system in Central Europe, are frequently associated with pareses. The aim of this study was to characterise paretic complications in patients with TBE and LNB, including their severity, persistence and impact on the patients' quality of life. Our retrospective observational study included patients with aseptic CNS infection due to TBE virus or Borrelia burgdorferi sensu lato. Paretic complications were evaluated in the acute phase and the patients were followed up until complete regression or long-term stabilisation of any neurological deficit. The severity of the neurological deficit was graded according to the modified Rankin Scale (mRS). A total of 823 patients (582 with TBE, 241 with LNB) was included. Paretic complications were diagnosed in 63 TBE patients (10.8 %) and in 147 LNB patients (61.0 %). In TBE, the most common neurological deficit was brachial plexus paresis in 21 patients (33 %) and bulbar symptoms in 18 patients (29 %). In LNB patients, facial nerve palsy was the most frequent neurological deficit (117patients; 79.6 %), followed by lower limb paresis in 23 patients (15.6 %). Forty-nine TBE patients and 134 LNB paretic patients completed follow-up. Paresis resolved within 3 weeks in 16 TBE patients (33 %) and 53 LNB patients (39.5 %), but the proportion of patients with paresis persisting for more than 12 months was significantly higher in TBE (34.7 vs. 3.7 %, p < 0.001). The mean mRS was significantly higher in TBE paretic patients compared to LNB (p < 0.001). Paretic complications are significantly more common in LNB than in TBE but pareses associated with TBE last longer than in LNB and considerably reduce the quality of life of patients. Prevention remains the only way to influence the long-term motor deficits of TBE.

Tick-Borne Encephalitis, Lombardy, Italy

Tick-borne encephalitis was limited to northeast portions of Italy. We report in Lombardy, a populous region in the northwest, a chamois displaying clinical signs of tickborne encephalitis virus that had multiple virus-positive ticks attached, as well as a symptomatic man. Further, we show serologic evidence of viral circulation in the area.

Seroprevalence of tick-borne encephalitis virus and vaccination coverage of tick-borne encephalitis, Sweden, 2018 to 2019

BackgroundIn Sweden, information on seroprevalence of tick-borne encephalitis virus (TBEV) in the population, including vaccination coverage and infection, is scattered. This is largely due to the absence of a national tick-borne encephalitis (TBE) vaccination registry, scarcity of previous serological studies and use of serological methods not distinguishing between antibodies induced by vaccination and infection. Furthermore, the number of notified TBE cases in Sweden has continued to increase in recent years despite increased vaccination.AimThe aim was to estimate the TBEV seroprevalence in Sweden.MethodsIn 2018 and 2019, 2,700 serum samples from blood donors in nine Swedish regions were analysed using a serological method that can distinguish antibodies induced by vaccination from antibodies elicited by infection. The regions were chosen to reflect differences in notified TBE incidence.ResultsThe overall seroprevalence varied from 9.7% (95% confidence interval (CI): 6.6-13.6%) to 64.0% (95% CI: 58.3-69.4%) between regions. The proportion of vaccinated individuals ranged from 8.7% (95% CI: 5.8-12.6) to 57.0% (95% CI: 51.2-62.6) and of infected from 1.0% (95% CI: 0.2-3.0) to 7.0% (95% CI: 4.5-10.7). Thus, more than 160,000 and 1,600,000 individuals could have been infected by TBEV and vaccinated against TBE, respectively. The mean manifestation index was 3.1%.ConclusionA difference was observed between low- and high-incidence TBE regions, on the overall TBEV seroprevalence and when separated into vaccinated and infected individuals. The estimated incidence and manifestation index argue that a large proportion of TBEV infections are not diagnosed.

A fatal case of tick-borne encephalitis in an immunocompromised patient: case report from Northeastern Poland and review of literature

Tick-borne encephalitis (TBE) is an infectious illness of the central nervous system caused by the TBE virus, which is commonly transmitted through a tick-bite. TBE is endemic in Europe and mid-Asia. In this study, we report a case of a 36-year-old woman, living in Northeastern Poland, with a history of double corneal transplantation and post-transplant immunosuppressive therapy who was admitted to hospital because of progressive weakness, acute headache, nausea, vertigo, vomiting, and fever. The patient was diagnosed with TBE. However, the diagnosis was challenging as the initial serological tests for antibodies against the TBE virus were negative. We want to raise the awareness among the clinicians that the course of TBE is often unpredictable and that it tends to be more severe in immunocompromised individuals.. Delayed production of antibodies against TBE virus, which might inhibit the diagnosis of the disease, is observed in some immunocompromised patients.

Genetic polymorphisms in innate immunity genes influence predisposition to tick-borne encephalitis

Tick-borne encephalitis (TBE) is a neuroviral disease that ranges in severity from a mild febrile illness to a severe and life-threatening meningoencephalitis or encephalomyelitis. There is increasing evidence that susceptibility to tick-borne encephalitis virus (TBEV)-induced disease and its severity are largely influenced by host genetic factors, in addition to other virus- and host-related factors. In this study, we investigated the contribution of selected single nucleotide polymorphisms (SNPs) in innate immunity genes to predisposition to TBE in humans. More specifically, we investigated a possible association between SNPs rs304478 and rs303212 in the gene Interferon Induced Protein With Tetratricopeptide Repeats 1 (IFIT1), rs7070001 and rs4934470 in the gene Interferon Induced Protein With Tetratricopeptide Repeats 2 (IFIT2), and RIG-I (Retinoic acid-inducible gene I) encoding gene DDX58 rs311795343, rs10813831, rs17217280 and rs3739674 SNPs with predisposition to TBE in population of the Czech Republic, where TBEV is highly endemic. Genotypic and allelic frequencies for these SNPs were analyzed in 247 nonimmunized TBE patients and compared with 204 control subjects. The analysis showed an association of IFIT1 rs304478 SNP and DDX58 rs3739674 and rs17217280 SNPs with predisposition to TBE in the Czech population indicating novel risk factors for clinical TBE but not for disease severity. These results also highlight the role of innate immunity genes in TBE pathogenesis.

Vaccination against tick-borne encephalitis elicits a detectable NS1 IgG antibody response

Vaccine-induced protection against tick-borne encephalitis virus (TBEV) is mediated by antibodies to the viral particle/envelope protein. The detection of non-structural protein 1 (NS1) specific antibodies has been suggested as a marker indicative of natural infections. However, recent work has shown that TBEV vaccines contain traces of NS1, and immunization of mice induced low amounts of NS1-specific antibodies. In this study, we investigated if vaccination induces TBEV NS1-specific antibodies in humans. Healthy army members (n = 898) were asked to fill in a questionnaire relating to flavivirus vaccination or infection, and blood samples were collected. In addition, samples of 71 suspected acute TBE cases were included. All samples were screened for the presence of TBEV NS1-specific IgG antibodies using an in-house developed ELISA. Antibodies were quantified as percent positivity in reference to a positive control. For qualitative evaluation, cut-off for positivity was defined based on the mean OD of the lower 95% of the vaccinated individuals + 3 SD. We found significantly higher NS1-specific IgG antibody titers (i.e., quantitative evaluation) in individuals having received 2, 3, or 4 or more vaccine doses than in non-vaccinated individuals. Similarly, the percentage of individuals with a positive test result (i.e., qualitative evaluation) was higher in individuals vaccinated against tick-borne encephalitis than in unvaccinated study participants. Although NS1-specific IgG titers remained at a relatively low level when compared to TBE patients, a clear distinction was not always possible. Establishing a clear cut-off point in detection systems is critical for NS1-specific antibodies to serve as a marker for distinguishing the immune response after vaccination and infection.

First evidence of tick-borne encephalitis (TBE) outside of Hokkaido Island in Japan

Tick-borne encephalitis (TBE) is an infection of the central nervous system caused by the tick-borne encephalitis virus (TBEV). TBE is endemic in parts of Europe and Asia. TBEV is transmitted to humans primarily by Ixodes ticks. There have been 5 TBE cases identified in Japan, all on the northern island of Hokkaido. Rodents with TBEV antibodies and Ixodes ticks have been identified throughout Japan, indicating that TBEV infection might be undiagnosed in Japan. Residual serum and cerebrospinal fluid (CSF) collected in 2010-2021 from 520 patients ≥1 year-of-age previously hospitalized with encephalitis or meningitis of unknown etiology at 15 hospitals (including 13 hospitals outside of Hokkaido) were screened by ELISA for TBEV IgG and IgM antibodies; TBEV infection was confirmed by the gold standard neutralization test. Residual serum was available from 331 (63.6%) patients and CSF from 430 (82.6%) patients; both serum and CSF were available from 189 (36.3%). Two patients were TBE cases: a female aged 61 years hospitalized for 104 days in Oita (2000 km south of Hokkaido) and a male aged 24 years hospitalized for 11 days in Tokyo (1200 km south of Hokkaido). Retrospective testing also identified a previous TBEV infection in a female aged 45 years hospitalized for 12 days in Okayama (1700 km south of Hokkaido). TBEV infection should be considered as a potential cause of encephalitis or meningitis in Japan. TBE cases are likely undiagnosed in Japan, including outside of Hokkaido, due to limited clinical awareness and lack of availability of TBE diagnostic tests.

Efficacy and immunogenicity of a veterinary vaccine candidate against tick-borne encephalitis in dogs

Tick-borne encephalitis (TBE) is a severe neuroinfection of humans. Dogs are also commonly infected with tick-borne encephalitis virus (TBEV). These infections are usually asymptomatic, but sometimes show clinical signs similar to those seen in humans and can be fatal. To date, there is no TBEV vaccine available for use in dogs. To address this need, a TBEV vaccine candidate for dogs based on inactivated whole virus antigen was developed. The safety, immunogenicity, and efficacy of the vaccine candidate were tested in mice as the preclinical model and in dogs as the target organism. The vaccine was well tolerated in both species and elicited the production of specific anti-TBEV antibodies with virus neutralising activity. Vaccination of mice provided complete protection against the development of fatal TBE. Immunisation of dogs prevented the development of viremia after challenge infection. Therefore, the developed vaccine candidate is promising to protect dogs from severe TBEV infections.

Recovery and sequelae in 523 adults and children with tick-borne encephalitis in Germany

PURPOSE

Despite being vaccine-preventable, tick-borne encephalitis (TBE) continues to cause considerable morbidity in Germany. Limited insight into potentially debilitating consequences of TBE may partially underly low (~ 20%) TBE vaccine uptake. We aimed to systematically assess TBE sequelae and other consequences.

METHODS

Routinely notified TBE patients from 2018 to 2020 from Southern Germany were invited to telephone interviews acutely and again after 18 months. Duration of acute symptoms was prospectively assessed. Recovery was defined as score 0 on the modified RANKIN scale. Determinants of time to recovery were analysed with cox regression, adjusted for covariates identified using directed acyclic graphs, yielding hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS

Of 558 cases, 523 (93.7%) completed follow-up. Full recovery was reported by 67.3% (children: 94.9%, adults: 63.8%). Sequelae included fatigue (17.0%), weakness (13.4%), concentration deficit (13.0%), and impaired balance (12.0%). Compared with 18-39-year-olds, recovery rates were 44% lower in ≥ 50-year-olds (HR: 0.56, 95%CI 0.42-0.75) and 79% higher in children (HR: 1.79, 95%CI 1.25-2.56). The recovery rate was 64% lower after severe TBE (compared to mild; HR: 0.36, 95%CI 0.25-0.52) and 22% lower with comorbidities (HR: 0.78, 95%CI 0.62-0.99). Substantial health-care use was reported (90.1% hospitalisation, 39.8% rehabilitation). Of employed cases, 88.4% required sick leave; 10.3% planned/reported premature retirement due to sequelae.

CONCLUSION

Half the adult and 5% of paediatric patients reported persisting sequelae after 18 months. Improved prevention could alleviate both individual (morbidity) and societal TBE burden (health-care costs, productivity losses). Insights into sequelae can help guide at-risk populations towards tick-avoidant strategies and encourage TBE vaccination.

Arbovirology and Cold War Collaborations: A Transnational History of the Tick-borne Encephalitis Vaccine, 1930-1980

This article analyzes the history of immunization against tick-borne encephalitis (TBE) and specifically the processes that led to the creation and application of TBE vaccines in the Soviet Union and Austria. Rather than presenting the development of TBE vaccines from the perspective of national scientific schools, the article investigates their history as a transnational project, focusing on the connections among the Soviet Union, Czechoslovakia, Austria, the United States, and the United Kingdom. It argues that biomedical research on TBE was profoundly intertwined with political and military agendas and depended on civil international cooperation as well as Soviet, American, and British military concerns, infrastructures and funding. The article consists of four parts that discuss (1) the identification of the TBE virus and the creation of the first TBE vaccine in the Soviet Union in the 1930s; (2) the internationalization of TBE research and vaccine development in the 1940s-1960s; (3) the history of TBE research and virology in Austria in the 1930s-1960s and the role of the US military funding; and (4) the cooperation of Austrian virologist Christian Kunz with the Microbiological Research Establishment Porton Down in the UK leading to the development of the Austrian/British vaccine against TBE in the 1970s.

Associations of the cerebrospinal fluid lymphocyte population with a clinical presentation of tick-borne encephalitis

In tick-borne encephalitis (TBE), lymphocytes infiltrating central nervous system are indispensable for the infection control, but also potentially immunopathogenic. To clarify their roles, we have evaluated cerebrospinal fluid (CSF) count of the main lymphocyte populations (considered as a proxy of the brain parenchyma lymphocytic infiltrate) in TBE patients and analyzed if they associate with clinical presentation, blood-brain barrier disruption and intrathecal antibody synthesis. We have studied CSF from 96 adults with TBE (50 with meningitis, 40 with meningoencephalitis, 6 with meningoencephalomyelitis), 17 children and adolescents with TBE and 27 adults with non-TBE lymphocytic meningitis. Th CD3+CD4+, Tc CD3+CD8+, double positive T CD3+CD4+CD8+, B CD19+ and NK CD16+/56+ cells were counted cytometrically with a commercial fluorochrome-stained monoclonal antibody set. The associations between the counts and fractions of these cells and clinical parameters were analyzed with non-parametric tests, p<0.05 considered significant. The TBE patients had lower pleocytosis with similar proportions of the lymphocyte populations compared to non-TBE meningitis. The different lymphocyte populations correlated positively with one another, as well as with CSF albumin, IgG and IgM quotients. The higher pleocytosis and expansion of Th, Tc and B cells associated with a more severe disease and neurologic involvement: Th with encephalopathy, myelitis and weakly with cerebellar syndrome, Tc with myelitis and weakly with encephalopathy, B with myelitis and with at least moderately severe encephalopathy. The double-positive T lymphocytes associated with myelitis, but not with other forms of CNS involvement. The fraction of double positive T cells decreased in encephalopathy and the fraction of NK in patients with neurologic deficits. In children with TBE, Tc and B counts were increased at the expense of Th lymphocytes in comparison with adults. The concerted intrathecal immune response, involving the main lymphocyte populations, increases with the clinical severity of TBE, with no evidently protective or pathogenic elements distinguishable. However, the particular populations including B, Th and Tc cells associate with different, though overlapping, spectra of CNS manifestations, suggesting they may be specifically related to TBE manifesting as myelitis, encephalopathy and cerebellitis. The double-positive T and NK cells do not expand evidently with severity and may be most closely associated with the protective anti-TBEV response.

Arboviral vaccines for use in pregnant travelers

Pregnant women traveling abroad can be exposed to a variety of arboviruses, primarily spread by mosquitoes or ticks. Some arboviral infections can be of particular concern for pregnant women or their fetuses. Vaccination is one preventive measure that can reduce the risk for infection. Several arboviral vaccines have been licensed for many years and can be used to prevent infection in travelers, namely Japanese encephalitis, yellow fever, and tick-borne encephalitis vaccines. Recommendations on use of these vaccines in pregnancy vary. Other arboviral vaccines have been licensed but are not indicated for use in pregnant travelers (e.g., dengue vaccines) or are in development (e.g., chikungunya, Zika vaccines). This review describes arboviral vaccines for travelers, focusing on women who are pregnant and those planning travel during pregnancy.

Seroprevalence and risk factors of tick-borne encephalitis in Mongolia between 2016 and 2022

The tick-borne encephalitis virus (TBEV) is a zoonotic agent that causes severe encephalitis in humans and is transmitted through the bites of infected ticks. Ixodes ticks are the primary vector for TBEV in Mongolia, and approximately 3.4% carry the TBEV. The ticks are capable of not only transmitting these viruses but also serve as excellent reservoir hosts. The Dermacenter tick species may have similar properties. TBEV is a significant cause of virus-related diseases of the central nervous system in many European countries as well as in China, Russia, and Mongolia. Our objectives were to investigate TBEV seroprevalence and infection risk factors in different biogeographical zones and provinces, especially in the highly endemic areas of Mongolia. Serum samples were collected from individuals who experienced tick bites (n = 993) in Mongolia between 2016 and 2022. Enzyme-linked immunosorbent assay of the samples was performed to evaluate for TBEV-specific immunoglobulin (Ig)M and IgG. We analyzed the risk factors and seroprevalence of TBEV infection among these individuals using a cross-sectional, questionnaire-based study. Statistical analyses were performed using a multistage cluster sampling survey design, and all data were analyzed using the R software. TBEV IgM and IgG antibodies were detected in 8.1% (80/993) and 20.2% (201/993) of all serum samples, respectively. The seroprevalence was significantly higher in men (68%, 95% confidence interval [CI]: 1.63-3.13, odds ratio [OR]: 2.25) than in women (p < 0.001). Additionally, the seroprevalence was significantly higher among unemployed (35.0%, 95% CI: 0.31-0.84, OR: 0.51) than employed individuals (p < 0.001). The seroprevalence was the highest among the 25-29 and 35-39-year age groups (11%, 95% CI: 1.29-5.51, OR: 2.65 and 11%, 95% CI: 0.94-3.87, OR: 1.9, respectively), and the lowest in the 65-69-year age group (4%, 95% CI: 0.46-6.15, OR: 1.83) (p < 0.001). Furthermore, the seroprevalence was the highest in Selenge province and the capital city Ulaanbaatar (40%, 95% CI: 1.73-21.7, OR: 5.07 and 28%, 95% CI: 0.51-6.89, OR: 1.57, respectively) and the lowest in Bayan-Ulgii and Dornod provinces (0.5%, 95% CI: 0.06-12.4, OR: 1.33 and 0.5%, 95% CI: 0.03-6.24, OR: 0.72, respectively). TBEV infection incidence remained low in most regions of Mongolia but increased in endemic areas. Furthermore, in the univariate subgroup analysis, age, occupation status, and residential area were significantly associated with TBEV seroprevalence.

Effectiveness of tick-borne encephalitis vaccination in Latvia, 2018-2020: an observational study

OBJECTIVES

Tick-borne encephalitis (TBE) is an infection by the tick-borne encephalitis virus (TBEV) that results in symptoms of central nervous system inflammation. TBE is endemic in Latvia and other European countries. TBE vaccines are commonly used in Latvia, but vaccine effectiveness estimates are limited.

METHODS

Study staff at Rīga Stradinš University conducted nationwide active surveillance for TBEV infections. Serum and cerebrospinal fluid were ELISA-tested for TBEV-specific IgG and IgM antibodies. Vaccination history was collected by interview and medical record review. Utilising data from surveillance and population surveys, vaccine effectiveness (with 95% confidence intervals) and cases averted were estimated using the screening method.

RESULTS

There were 587 laboratory-identified TBE cases from 2018-2020; 98.1% (576/587) were unvaccinated, 1.5% (9/587) were unknown or partially-vaccinated, and 0.3% (2/587) were fully-vaccinated (three-dose primary series and appropriately timed boosters). TBE resulted in the death of 1.7% (10/587) of TBE cases. TBE vaccine history was ascertained from 92.0% (13,247/14,399) people from the general population: 38.6% (5113/13,247) were unvaccinated, 26.3% (3484/13,247) were fully-vaccinated, and 35.1% (4650/13,247) were partially-vaccinated. TBE vaccine effectiveness was 99.5% (98.0-99.9) against TBE, 99.5% (97.9-99.9) against TBE hospitalisation, 99.3% (94.8-99.9) against moderate/severe TBE, and 99.2% (94.4-99.9) against TBE hospitalisation >12 days. From 2018-2020, vaccination averted 906 TBE cases, including 20 deaths.

CONCLUSIONS

TBE vaccine was highly effective in preventing TBE, moderate and severe disease, and prolonged hospitalisation. To prevent life-threatening TBE, TBE vaccine uptake and compliance should be increased in Latvia and other European regions where TBE is endemic.

Can protection motivation theory predict protective behavior against ticks?

BACKGROUND

Cases of reported tick-borne diseases in humans have increased over the past decades. Strategies informing the public about ticks, their associated diseases, and preventive measures are often highlighted as important in limiting pathogen transfer and disease. However, knowledge about the motivation for people to apply preventative measures is sparse.

METHODS

The aim was to examine if Protection Motivation Theory, a model of disease prevention and health promotion, can predict the use of protective measures against ticks. Ordinal logistic regression and Chi-square tests were used on data from a cross-sectional survey with respondents from Denmark, Norway, and Sweden (n = 2658). We examined the effect of (1) the perceived seriousness of tick bites, Lyme borreliosis (LB), and tick-borne encephalitis (TBE), and (2) the perceived probability of getting a tick bite, Lyme borreliosis, and tick-borne encephalitis on protection against ticks. Finally, we examined if there was an association between the use of a protective measure and the perceived efficacy of that measure.

RESULTS

The perceived seriousness of a tick bite and LB significantly predict who is more likely to apply protective measures for all three countries combined. The perceived seriousness of TBE did not significantly predict the level of adoption of protective measures applied by respondents. The perceived likelihood of getting a tick bite within the next 12 months and the perceived likelihood of getting LB if bitten by a tick significantly predicted the application of protective measures. However, the increases in the likelihood of protection were very small. The application of a certain type of protection was always correlated with the perceived efficacy of the same protective measure.

CONCLUSION

Some variables of PMT may be used to predict the level of adoption of protection applied against ticks and tick-borne diseases. We found that the perceived seriousness of a tick bite and LB significantly predict the level of adoption protection. The perceived likelihood of getting a tick bite or LB also significantly predicted the level of adoption of protection, although the change was very small. The results regarding TBE were less clear. Lastly, there was an association between applying a protective measure and the perceived efficacy of the same measure.

Sustained antibody persistence for at least 15 years after a booster vaccination against tick-borne encephalitis following different primary vaccination schedules: Third 5-year follow-up

BACKGROUND

Vaccination is the best mode of protection against tick-borne encephalitis (TBE) and its sequelae. The duration of protection and the optimal interval of repeat booster doses are still debated. The current study evaluated the persistence of the antibody response 11-15 years after a first booster vaccination following different primary vaccination schedules with a TBE vaccine (Encepur Adults, manufactured by Bavarian Nordic, previously by GSK).

METHODS

This phase IV, open-label, mono-centric extension study enrolled adults who had received (at ≥ 12 years of age) primary vaccination with one of three randomly assigned TBE vaccine schedules (rapid [group R], conventional [group C], or accelerated conventional schedule [group A]) followed by a booster dose 3 years later. The antibody response was measured annually from 11 to 15 years post-booster using a TBE virus neutralization test (NT). An NT titer of ≥ 10 was considered as a clinically meaningful threshold and surrogate for protection.

RESULTS

In total, 194 participants were enrolled and included in the per-protocol set; 188 completed the study. The percentage of participants with an NT titer ≥ 10 was 100% in group R and 99.0% in group A at all visits and ranged from 100% (year 11) to 95.8% (year 15) in group C. NT geometric mean titers were similar in the three study groups (181-267 in group R, 142-227 in group C, 141-209 in group A). NT geometric mean titers also remained high among participants ≥ 50 years old (98-206) and ≥ 60 years old (91-191) across study groups and time points.

CONCLUSIONS

This study showed neutralizing antibody persistence for at least 15 years after a first booster dose of the Encepur Adults TBE vaccine in all age groups evaluated, regardless of which primary vaccination schedule was given to adolescents or adults. Trialregistry: ClinicalTrials.gov: NCT03294135.

Tick-Borne Encephalitis: An Update for the Special Operations Forces Provider

Tick-borne encephalitis (TBE) is a severe disease caused by the tick-borne encephalitis virus (TBEV). TBEV is endemic throughout Eurasia and can cause persistent neurologic deficits and death. Special Operations Forces (SOF) participating in field exercises or operations in TBE-endemic countries are at significantly increased risk of infection. Unlike Lyme disease and other tick-borne illnesses, transmission of TBEV can be immediate, and early tick removal does not reduce the risk of infection. While there are no virus-specific treatments available, the US Food and Drug Administration (FDA) recently approved a TBE vaccine that has yet to be incorporated into formal Department of Defense (DoD) recommendations. SOF medical providers should be aware of this disease entity and consider the TBE vaccine when planning exercises and operations in areas of responsibility (AORs) with TBE-endemic countries. This review serves as a refresher and update on the epidemiology, transmission, and management of TBE for the SOF provider.

Tick-borne encephalitis: Acute clinical manifestations and severity in 581 cases from Germany, 2018-2020

OBJECTIVES

Tick-borne encephalitis (TBE) is a growing public health problem with an average of 361 cases notified annually to Germany's passive surveillance system since 2001. We aimed to assess clinical manifestations and identify covariates associated with severity.

METHODS

We included cases notified 2018-2020 in a prospective cohort study and collected data with telephone interviews, questionnaires to general practitioners, and hospital discharge summaries. Covariates' causal associations with severity were evaluated with multivariable logistic regression, adjusted for variables identified via directed acyclic graphs.

RESULTS

Of 1220 eligible cases, 581 (48%) participated. Of these, 97.1% were not (fully) vaccinated. TBE was severe in 20.3% of cases (children: 9.1%, ≥70-year-olds: 48.6%). Routine surveillance data underreported the proportion of cases with central nervous system involvement (56% vs. 84%). Ninety percent required hospitalization, 13.8% intensive care, and 33.4% rehabilitation. Severity was most notably associated with age (odds ratio (OR): 1.04, 95% confidence interval (CI): 1.02-1.05), hypertension (OR: 2.27, 95%CI: 1.37-3.75), and monophasic disease course (OR: 1.67, 95%CI: 1.08-2.58).

CONCLUSIONS

We observed substantial TBE burden and health service utilization, suggesting that awareness of TBE severity and vaccine preventability should be increased. Knowledge of severity-associated factors may help inform patients' decision to get vaccinated.

Spatiotemporal spread of tick-borne encephalitis in the EU/EEA, 2012 to 2020

BackgroundTick-borne encephalitis (TBE) is a vaccine-preventable disease involving the central nervous system. TBE became a notifiable disease on the EU/EEA level in 2012.AimWe aimed to provide an updated epidemiological assessment of TBE in the EU/EEA, focusing on spatiotemporal changes.MethodsWe performed a descriptive analysis of case characteristics, time and location using data of human TBE cases reported by EU/EEA countries to the European Centre for Disease Prevention and Control with disease onset in 2012-2020. We analysed data at EU/EEA, national, and subnational levels and calculated notification rates using Eurostat population data. Regression models were used for temporal analysis.ResultsFrom 2012 to 2020, 19 countries reported 29,974 TBE cases, of which 24,629 (98.6%) were autochthonous. Czechia, Germany and Lithuania reported 52.9% of all cases. The highest notification rates were recorded in Lithuania, Latvia, and Estonia (16.2, 9.5 and 7.5 cases/100,000 population, respectively). Fifty regions from 10 countries, had a notification rate ≥ 5/100,000. There was an increasing trend in number of cases during the study period with an estimated 0.053 additional TBE cases every week. In 2020, 11.5% more TBE cases were reported than predicted based on data from 2016 to 2019. A geographical spread of cases was observed, particularly in regions situated north-west of known endemic regions.ConclusionA close monitoring of ongoing changes to the TBE epidemiological situation in Europe can support the timely adaption of vaccination recommendations. Further analyses to identify populations and geographical areas where vaccination programmes can be of benefit are needed.

Dairy milk from cow and goat as a sentinel for tick-borne encephalitis virus surveillance

Tick-borne encephalitis (TBE) is one of the most severe human tick-borne diseases in Europe. It is caused by the tick-borne encephalitis virus (TBEV), which is transmitted to humans mainly via bites of Ixodes ricinus or I. persulcatus ticks. The geographical distribution and abundance of I. ricinus is expanding in Sweden as has the number of reported human TBE cases. In addition to tick bites, alimentary TBEV infection has also been reported after consumption of unpasteurized dairy products. So far, no alimentary TBEV infection has been reported in Sweden, but knowledge about its prevalence in Swedish ruminants is scarce. In the present study, a total of 122 bulk tank milk samples and 304 individual milk samples (including 8 colostrum samples) were collected from dairy farms (n = 102) in Sweden. All samples were analysed for the presence of TBEV antibodies by ELISA test and immunoblotting. Participating farmers received a questionnaire about milk production, pasteurization, tick prophylaxis used on animals, tick-borne diseases, and TBE vaccination status. We detected specific anti-TBEV antibodies, i.e., either positive (>126 Vienna Units per ml, VIEU/ml) or borderline (63-126 VIEU/ml) in bulk tank milk from 20 of the 102 farms. Individual milk samples (including colostrum samples) from these 20 farms were therefore collected for further analysis. Our results revealed important information for detection of emerging TBE risk areas. Factors such as consumption of unpasteurized milk, limited use of tick prophylaxis on animals and a moderate coverage of human TBE vaccination, may be risk factors for alimentary TBEV infection in Sweden.

Co-exposure to Anaplasma spp., Coxiella burnetii and tick-borne encephalitis virus in sheep in southern Germany

The intracellular bacteria Anaplasma spp. and Coxiella burnetii and the tick-borne encephalitis virus (TBEV) are tick-transmitted pathogens circulating in the southern German sheep population. Knowledge of interaction among Anaplasma spp., C. burnetii and TBEV in sheep is lacking, but together they might promote and reinforce disease progression. The current study aimed to identify co-exposure of sheep to Anaplasma spp., C. burnetii and TBEV. For this purpose, 1,406 serum samples from 36 sheep flocks located in both southern German federal states, Baden-Wuerttemberg and Bavaria, were analysed by ELISAs to determine the antibody levels of the three pathogens. Inconclusive and positive results from the TBEV ELISA were additionally confirmed by a serum neutralisation assay. The proportion of sheep with antibodies against Anaplasma spp. (47.2%), C. burnetii (3.7%) and TBEV (4.7%) differed significantly. Significantly more flocks with Anaplasma spp. seropositive sheep (91.7%) were detected than flocks with antibodies against TBEV (58.3%) and C. burnetii (41.7%), but there was no significant difference between the number of flocks which contained TBEV and C. burnetii seropositive sheep. Seropositivity against at least two pathogens was detected in 4.7% of sheep from 20 flocks. Most co-exposed sheep had antibodies against Anaplasma spp./TBEV (n = 36), followed by Anaplasma spp./C. burnetii (n = 27) and Anaplasma spp./C. burnetii/TBEV (n = 2). Only one sheep showed an immune response against C. burnetii and TBEV. Flocks with sheep being positive against more than one pathogen were widely distributed throughout southern Germany. The descriptive analysis revealed no association between the antibody response of the three pathogens at animal level. Taking the flocks as a cluster variable into account, the exposure to TBEV reduced the probability of identifying C. burnetii antibodies in sheep significantly (odds ratio 0.46; 95% confidence interval 0.24-0.85), but the reason for this is unknown. The presence of Anaplasma spp. antibodies did not influence the detection of antibodies against C. burnetii and TBEV. Studies under controlled conditions are necessary to evaluate any possible adverse impact of co-exposure to tick-borne pathogens on sheep health. This can help to clarify rare disease patterns. Research in this field may also support the One Health approach due to the zoonotic potential of Anaplasma spp., C. burnetii and TBEV.

New directions in the experimental therapy of tick-borne encephalitis

Tick-borne encephalitis (TBE) is a potentially fatal disease common in much of Europe and Asia. There is no specific therapy for the treatment of TBE patients. However, several efforts are being made to develop small molecules that specifically interfere with the life cycle of TBE virus. In particular, recently various nucleoside analogues that can inhibit the viral replicase, such as the RNA-dependent RNA polymerase or viral methyltransferases, have been explored. In addition, human or chimeric (i.e., structural chimeras that combine mouse variable domains with human constant domains) monoclonal antibodies with promising potential for post-exposure prophylaxis or early therapy have been developed. This review summarizes the latest directions and experimental approaches that may be used to combat TBE in humans.

Serum matrix metalloproteinase-9 (MMP-9) as a biomarker in paediatric and adult tick-borne encephalitis patients

Matrix metalloproteinases (MMPs) play an important role in central nervous system infections. We analysed the levels of 8 different MMPs in the cerebrospinal fluid (CSF) of 89 adult patients infected with tick-borne encephalitis (TBE) virus and compared them with the levels in a control group. MMP-9 was the only MMP that showed significantly increased CSF levels in TBE patients. Serum MMP-9 levels were subsequently measured in 101 adult TBE patients at various time points during the neurological phase of TBE and at follow-up. In addition, serum MMP-9 was analysed in 37 paediatric TBE patients. Compared with control levels, both paediatric and adult TBE patients had significantly elevated serum MMP-9 levels. In most adult patients, serum MMP-9 levels peaked at hospital admission, with higher serum MMP-9 levels observed in patients with encephalitis than in patients with meningitis. Elevated serum MMP-9 levels were observed throughout hospitalisation but decreased to normal levels at follow-up. Serum MMP-9 levels correlated with clinical course, especially in patients heterozygous for the single-nucleotide polymorphism rs17576 (A/G; Gln279Arg) in the MMP9 gene. The results highlight the importance of MMP-9 in the pathogenesis of TBE and suggest that serum MMP-9 may serve as a promising bioindicator of TBE in both paediatric and adult TBE patients.

Vaccine uptake in 20 countries in Europe 2020: Focus on tick-borne encephalitis (TBE)

Vaccination as a highly effective measure to protect against tick-borne encephalitis (TBE) comes into new focus as known risk areas are expanding across Europe and Asia. Here we present an online household survey conducted in 20 European countries spanning endemic and non-endemic regions of TBE in 2020. With a comprehensive and standardized list of questions, this survey provided a unique opportunity to compare TBE/TBE vaccine awareness, TBE severity perception, vaccine uptake, vaccination completeness/compliance and motivators/barriers for vaccination across Europe. Among the 51,478 participants, tetanus- (72-92%), influenza- (83-98%), and measles-awareness (79-96%) were highest, but awareness was low for Lyme borreliosis, bacterial meningitis and pneumococcal pneumonia. Awareness towards TBE and a TBE vaccine was 74% and 56% in endemic countries, respectively, compared to 30% and 12% in non-endemic countries. Vaccine uptake defined as at least one TBE vaccination was found to be highly heterogenous across both endemic (range 7-81%) and non-endemic countries (range 1-8%). Compliance with the recommended vaccination schedule was 21% for the primary vaccination series and dropped to 7% for the first booster vaccination in endemic countries. The percentage of participants protected against TBE by vaccination at the time of the survey ranged from 21% in Slovakia to 69% in Lithuania. The perception of personal risk or lack thereof was found to be the most influencing factor for and against TBE vaccination. Overall, these data indicate highly heterogenous responses in different European countries regarding not only awareness towards a TBE vaccine, but also regarding TBE vaccine uptake and compliance. Regionally focused strategies to increase diagnostic completeness as well as TBE vaccination are needed across Europe.

Tick-borne encephalitis in pregnancy

A case report describing the case of a young and healthy pregnant patient who manifested tick-borne encephalitis in her peripartal period. This neuroinfection is rare in pregnant women. A more severe encephalomyelitic form of the disease, resulting in lasting consequences, occurred in the patient even though she had recently undergone a proper vaccination. In the course of 11-month observation, her newborn showed no symptoms of the disease nor psychomotor developmental disorders.

The influence of meteorological factors on the risk of tick-borne encephalitis infection

OBJECTIVES

The aim of this work was to analyze the relationship between new cases of clinical tick-borne encephalitis (TBE) and various meteorological and seasonal predictors.

MATERIAL AND METHODS

The modelling is based on national data from the Czech Republic for the period 2001-2016 in daily resolution, namely on average temperatures, average relative air humidity and the number of TBE cases classified according to the date of the first symptoms. Four variants of a negative binomial model from the generalized additive model class are used. The basic model relates the occurrence of TBE to the lagged ambient daily average temperature and daily average relative air humidity and their interaction with the lag reflecting the incubation period and other factors. The lag value was estimated via the optimization procedure based on Akaike information criterion. The model also includes the effect of the season and the effect of the day of the week. To increase the biological plausibility, the basic model has been expanded to account for possible time-varying effects of meteorological variables and to incorporate multiple lags.

RESULTS

The most statistically significant effect is the within-year seasonality and then the interaction of the temperature and relative air humidity. The relationship of both meteorological factors and their interactions vary throughout the activities season of the hostquesting Ixodes ricinus. This also changes the conditions of occurrence of the new clinical cases of TBE. The time-varying effect of meteorological factors on the incidence of TBE shows non-trivial changes within a year. In the period before the middle of the calendar year (around the week 22) the effect decreases, then it is followed by an increase until the week 35.

CONCLUSION

Flexible models were developed with quantitatively characterized effects of temperature, air humidity and their interaction, with the delay of the effect estimated through the optimization process. Performance of the model with multiple lags was checked using independent data to verify the possibility of using the results to improve the prediction of the risk of clinical cases of TBE uprise.

The impact of climatic conditions on the dynamics of tick-borne encephalitis in Slovakia in 2012-2016

OBJECTIVES

The main aim of our work was to analyse the development of the dynamics of tick-borne encephalitis (TBE) in connection with climatic conditions in Slovakia in 2012-2016.

MATERIAL AND METHODS

We performed the analysis based on the data provided by the Epidemiological Information System and the Slovak Hydrometeorological Institute. The study group consisted of 639 patients with confirmed diagnosis.

RESULTS

The highest incidence of TBE was recorded in 2016. The highest standardized incidence rate of TBE was in the districts of the Trenčín, Žilina and Banská Bystrica regions. The relation of TBE to air temperature showed that most cases of TBE were recorded at an air temperature of 10-20 °C during the months of May to October in 2012-2016. The relationship between air temperature and number of days with snow cover and the number of TBE cases proved to be statistically significant (p-value < 0.001). There is a statistically significant difference in the average number of disease cases according to the air temperature category (p-value = 0.03). This disease occurs mainly in districts with an altitude of 200-400 m a. s. l. The dynamics of TBE in Slovakia is two-peaked with a decline in August. The main season of the disease lasts from May to October, peaking during the summer months of June and July.

CONCLUSION

The results of the study point to a prognosis of the development of the disease in connection with air temperature. Based on the findings that in recent years we have observed a slightly increasing trend of TBE in Slovakia due to climate change, this disease is considered a persistent public health problem.

[Influence of the COVID-19 pandemic on the occurrence of neurological infectious diseases]

BACKGROUND

During the coronavirus disease 2019 (COVID-19) pandemic a wide range of hygiene measures were implemented to contain the spread of infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Besides a mitigation of SARS-CoV‑2, a decline in the number of other respiratory tract infections could be observed. Interestingly, the numbers for some infections of the central nervous system (CNS) decreased as well.

OBJECTIVE

This review article shows the development of important CNS infections in Germany during the COVID-19 pandemic.

MATERIAL AND METHOD

This article is based on relevant literature on the epidemiology of CNS infections during the COVID-19 pandemic up to autumn 2022.

RESULTS

During the COVID-19 pandemic the frequency of bacterial meningitis caused by Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae significantly declined. The frequency of viral meningitis, particularly those caused by Enterovirus, decreased as well. In contrast, the number of patients suffering from tick-borne encephalitis significantly increased within the first year of the pandemic.

DISCUSSION

During the pandemic there was a decrease in cases of bacterial and viral meningitis, most likely due to the general containment strategies and social contact restrictions. The increase of infections transmitted by ticks could be a consequence of changed leisure activities during the pandemic.

Comparison of laboratory and immune characteristics of the initial and second phase of tick-borne encephalitis

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.

Systematic Review and Meta-analysis of Foodborne Tick-Borne Encephalitis, Europe, 1980-2021

Most cases were associated with ingesting unpasteurized dairy products from goats; the clinical attack rate was 14%.

Tick-borne encephalitis (TBE) is a viral infection of the central nervous system that occurs in many parts of Europe and Asia. Humans mainly acquire TBE through tick bites, but TBE occasionally is contracted through consuming unpasteurized milk products from viremic livestock. We describe cases of TBE acquired through alimentary transmission in Europe during the past 4 decades. We conducted a systematic review and meta-analysis of 410 foodborne TBE cases, mostly from a region in central and eastern Europe. Most cases were reported during the warmer months (April–August) and were associated with ingesting unpasteurized dairy products from goats. The median incubation period was short, 3.5 days, and neuroinvasive disease was common (38.9%). The clinical attack rate was 14% (95% CI 12%–16%), and we noted major heterogeneity. Vaccination programs and public awareness campaigns could reduce the number of persons affected by this potentially severe disease.

Three-dose versus four-dose primary schedules for tick-borne encephalitis (TBE) vaccine FSME-immun for those aged 50 years or older: A single-centre, open-label, randomized controlled trial

BACKGROUND

TBE vaccination failures among those past middle age have raised concern about immune response declining with age. We investigated immunogenicity of the TBE-vaccine FSME-Immun among those aged 50+ years using the standard three-dose primary series and alternative four-dose schedules.

METHODS

In this single-centre, open-label, randomized controlled trial, 200 TBE-naive Swedish adults were given primary TBE vaccination with FSME-Immun. Those aged 50+ years (n = 150) were randomized to receive the standard three-dose (days 0-30-360) or one of two four-dose series (0-7-21-360; 0-30-90-360). For participants < 50 years (n = 50) the standard three-dose schedule was used. Titres of neutralizing antibodies were determined on days 0, 60, 120, 360, and 400. The main outcome was the log titre of TBE virus-specific neutralizing antibodies on day 400.

RESULTS

The three-dose schedule yielded lower antibody titres among those aged 50+ years than the younger participants on day 400 (geometric mean titre 41 versus 74, p < 0.05). The older group showed higher titres for the four-dose 0-7-21-360 than the standard three-dose schedule both on day 400 (103 versus 41, p < 0.01; primary end point) and at the other testing points (days 60, 120, 360). Using the other four-dose schedule (0-30-90-360), no such difference was observed on day 400 (63 versus 41, NS).

CONCLUSION

Immune response to the TBE vaccine declined with age. A four-dose schedule (0-7-21-360) may benefit those aged 50 years or older. This study is registered at ClinicalTrials.gov, NCT01361776.

The manifestation of myositis in tick-borne encephalitis as a prophet of severe disease course: a rare case report

Tick-borne encephalitis (TBE) is one of the most serious neurological tick-transmitted diseases. The initial phase usually occurs with non-specific symptoms such as fever, headache, and muscular pain. The clinical spectrum of the second phase of the disease typically ranges from mild meningitis to severe meningoencephalitis. Our case demonstrates a rare clinical case of acute myositis as manifestation of TBE virus infection. A 33-year-old female was admitted to the Rheumatology centre with a fever followed by proximal muscle pain and weakness. Despite the tick bite history and marginally positive anti-TBE virus IgM titre, the patient did not present any neurological symptoms. Laboratory test results showed elevated creatine kinase (CK) and myoglobin. Other infections, idiopathic inflammatory myopathies, were excluded. TBE virus infection was confirmed by rapid seroconversion of specific IgG class antibodies in serum. The second phase of the disease was followed by neurological symptoms and a repeated increase of CK and myoglobin. We suggest that in the case of acute myositis of unknown cause and the history of thick bite, TBE virus infection should be considered and creatine kinase might be considered as a laboratory marker of disease activity that correlates with the severity of the disease.

Effectiveness of TBE vaccination in southern Germany and Latvia

BACKGROUND

Tick-borne encephalitis (TBE) is a vaccine-preventable disease which may cause long-term sequelae and even death. The data on the long-term effectiveness of TBE vaccines are limited. Additionally, the vaccination schedule is complex which in part contributes towards sub-optimal uptake in TBE-endemic areas. The current ecological study measures vaccine effectiveness (VE) in two European countries.

METHODS

TBE VE was measured from 2007 to 2018 in Latvia and Southern German states by age group, vaccination history, and schedule compliance. TBE cases and vaccination history were obtained from the public health agencies for Latvia and the southern German federal states of Bavaria and Baden-Wuerttemberg. Cases were "within schedule" if a TBE infection was diagnosed within the time interval preceding the next scheduled dose and "outside schedule" if the diagnosis occurred after the next scheduled dose. Vaccine uptake was estimated via representative nationwide surveys.

RESULTS

VE after 2, 3, and ≥4 doses was high in both countries at 97.2%, 95.0%, and 95.4% for southern Germany, and 98.1%, 99.4%, and 98.8% for Latvia while within- schedule, and only showed marginal differences outside schedule at 90.6%, 89.9%, and 95.6% for southern Germany, and 97.4%, 98.4%, and 99.0% for Latvia regardless of age groups.

CONCLUSIONS

In both countries, VE after two and three primary doses within-schedule was very high in all age groups. Once receiving booster doses, high VE continued to be observed even in persons with extended intervals since the last dose received, suggesting that longer and more flexible booster intervals may be considered for sustainable long-term protection.

Meningitis, meningoencephalitis and encephalitis in Bern: an observational study of 258 patients

Background

Depending on geographic location, causes of encephalitis, meningoencephalitis and meningitis vary substantially. We aimed to identify the most frequent causes, clinical presentation and long-term outcome of encephalitis, meningoencephalitis and meningitis cases treated in the Inselspital University Hospital Bern, Switzerland.

Methods

In this monocentric, observational study, we performed a retrospective review of clinical patient records for all patients treated within a 3-year period. Patients were contacted for a telephone follow-up interview and to fill out questionnaires, especially related to disturbances of sleep and wakefulness.

Results

We included 258 patients with the following conditions: encephalitis (18%), nonbacterial meningoencephalitis (42%), nonbacterial meningitis (27%) and bacterial meningoencephalitis/meningitis (13%). Herpes simplex virus (HSV) was the most common cause of encephalitis (18%); tick-borne encephalitis virus (TBEV) was the most common cause of nonbacterial meningoencephalitis (46%), enterovirus was the most common cause of nonbacterial meningitis (21%) and Streptococcus pneumoniae was the most common cause of bacterial meningoencephalitis/meningitis (49%). Overall, 35% patients remained without a known cause. After a median time of 16 months, 162 patients participated in the follow-up interview; 56% reported suffering from neurological long-term sequelae such as fatigue and/or excessive daytime sleepiness (34%), cognitive impairment and memory deficits (22%), headache (14%) and epileptic seizures (11%).

Conclusions

In the Bern region, Switzerland, TBEV was the overall most frequently detected infectious cause, with a clinical manifestation of meningoencephalitis in the majority of cases. Long-term neurological sequelae, most importantly cognitive impairment, fatigue and headache, were frequently self-reported not only in encephalitis and meningoencephalitis survivors but also in viral meningitis survivors up to 40 months after acute infection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-021-02502-3.

Incidence and occurrence of tick-borne encephalitis and neuroborreliosis in Germany

Given the nationwide distribution of the vector, Ixodes ricinus, both neuroborreliosis and tick-borne encephalitis (TBE) might be expected to occur throughout Germany. However, cases of neuroborreliosis and TBE have so far only been reported in certain German states and counties. The aim of this survey therefore was to investigate the possible occurrence of TBE in regions not designated as known risk areas and the spread and incidence of neuroborreliosis throughout Germany. Data were collected by means of a questionnaire which was sent to 305 neurological clinics in Germany. Only twenty-two of them (7.2%) participated in a prospective, and 52 (17%) in a retrospective survey, therefore the significance of the study is limited. Cases of TBE were detected in five counties (Barnim, Dessau-Roßlau, Western Pomerania-Ruegen, Saarbruecken, Uckermark) that were not known so far as areas of risk according to the definition of the German Robert-Koch-Institute (RKI). The median incidence of TBE in various counties was 1.24 cases with a range from 0.19 to 20 cases per 100,000 inhabitants/year. Illnesses from neuroborreliosis were reported from all 61 counties, where clinics participated in the study. The incidence here varied between 0.19 and 23.4 cases with a median of 3.0 cases per 100,000 inhabitants/year. In areas where both diseases occurred, their incidence differed greatly from each other. The survey shows the occurrence of TBE in several counties in eastern Germany that are not defined as risk areas by the RKI and an incidence of neuroborreliosis in Germany that is significantly higher than reported to the public health authorities.

Public health preparedness and response synergies between institutional authorities and the community: a qualitative case study of emerging tick-borne diseases in Spain and the Netherlands

BACKGROUND

Communities affected by infectious disease outbreaks are increasingly recognised as partners with a significant role to play during public health emergencies. This paper reports on a qualitative case study of the interactions between affected communities and public health institutions prior to, during, and after two emerging tick-borne disease events in 2016: Crimean-Congo Haemorrhagic Fever in Spain, and Tick-Borne Encephalitis in the Netherlands. The aim of the paper is to identify pre-existing and emergent synergies between communities and authorities, and to highlight areas where synergies could be facilitated and enhanced in future outbreaks.

METHODS

Documentary material provided background for a set of semi-structured interviews with experts working in both health and relevant non-health official institutions (13 and 21 individuals respectively in Spain and the Netherlands), and focus group discussions with representatives of affected communities (15 and 10 individuals respectively). Data from all sources were combined and analysed thematically, initially independently for each country and then for both countries together.

RESULTS

Strong synergies were identified in tick surveillance activities in both countries, and the value of pre-existing networks of interest groups for preparedness and response activities was recognised. However, authorities also noted that there were hard-to-reach and potentially vulnerable groups, such as hikers, foreign tourists, and volunteers working in green areas. While the general population received preventive information about the two events, risk communication or other community engagement efforts were not seen as necessary specifically for these sub-groups. Post-event evaluations of community engagement activities during the two events were limited, so lessons learned were not well documented.

CONCLUSIONS

A set of good practices emerged from this study, that could be applied in these and other settings. They included the potential value of conducting stakeholder analyses of community actors with a stake in tick-borne or other zoonotic diseases; of utilising pre-existing stakeholder networks for information dissemination; and of monitoring community perceptions of any public health incident, including through social media. Efforts in the two countries to build on the community engagement activities that are already in place could contribute to better preparedness planning and more efficient and timely responses in future outbreaks.

Autochthonous tick-borne encephalitis in the United Kingdom: A second probable human case and local eco-epidemiological findings

Tick-borne encephalitis (TBE) is a neurotropic flaviviral disease. TBE was previously thought to be absent from the United Kingdom. We report the second probable case of United Kingdom-acquired TBE and demonstrate deer TBE-serocomplex seropositivity in the surrounding area, providing further evidence of the presence of TBE in England.

[Gestion of arboviral alerts: Experience feedback from the Secproch working group of the French "Haut Conseil de la santé publique" (2019-2021)]

The Secproch working group (for "sécurité des produits issus du corps humain") was created in 2019 within the « Haut Conseil de la santé publique » (HCSP) for addressing all the questions related to labile blood products, organs, tissues, cells (OTC) and gametes issued from human body. It is notably in charge of the management of alerts regarding arbovirus infections. These infections due to arthropod-transmitted viruses are responsible for emergence and reemergence, notably in the context of global warming. This review relates the alerts taken into consideration by the Secproch group between 2019 and 2021 following three pathologies due to Flaviviridae : dengue, West Nile virus (WNV) infection and tick-borne encephalitis (TBE). The dengue alerts have occurred in French Indies where the virus is endemic/epidemic, Reunion Island where the population was naïve until 2018 towards the virus, and the metropole where foci of autochthonous cases are observed sporadically. The WNV infection was responsible of both human and equine cases in 2019 in the South of France but with intensity much less than in 2018. At last, the TBE virus was at the origin of a cluster of about 40 cases in the Ain department following a contamination by crude non-pasteurized goat cheese. This review offers the opportunity to reevaluate the risks linked to these three viruses through blood products and organs/tissues/cells and to precise the means recommended by HCSP to secure these products.

Knowledge and vaccination practices among family physicians in northeastern France regarding tick-borne encephalitis virus

Tick-borne encephalitis (TBE) cases have been emerging in Europe. The Franche-Comte area, in northeastern France, borders Switzerland, but the two countries differ in their approach to TBE surveillance and prevention. Because family physicians (FPs) are in direct contact with the local population, at-risk of infected tick bites, they need to be well aware of TBE epidemiology and management. An observational survey was performed in 2019 in order to investigate Franche-Comte physicians' knowledge and vaccination practices with regard to TBE. Standardized online questionnaires were sent to a list of FPs practicing in Franche-Comte. The questionnaires included socio-demographic details, questions about TBE knowledge, symptomatology and vaccination. The response rate was 14.7%. FPs practicing in rural areas reported a significantly higher frequency of consultations for tick bites. While 81% of FPs indicated that they had some knowledge about TBE, only 20% were at ease with its clinical symptomatology. Thirty-one % of the FP participants performed TBE vaccinations. A general lack of knowledge about TBE and its clinical symptoms was observed in this survey. FPs play an essential role in screening and preventing TBE, especially those practicing in rural areas and in areas bordering Switzerland.

The increased intrathecal expression of the monocyte-attracting chemokines CCL7 and CXCL12 in tick-borne encephalitis

Tick-borne encephalitis (TBE) is a relatively severe and clinically variable central nervous system (CNS) disease with a significant contribution of a secondary immunopathology. Monocytes/macrophages play an important role in the CNS inflammation, but their pathogenetic role and migration mechanisms in flavivirus encephalitis in humans are not well known. We have retrospectively analyzed blood and cerebrospinal fluid (CSF) monocyte counts in 240 patients with TBE presenting as meningitis (n = 110), meningoencephalitis (n = 114), or meningoencephalomyelitis (n = 16), searching for associations with other laboratory parameters, clinical presentation, and severity. We have measured concentrations of selected monocytes-attracting chemokines (CCL7, CXCL12, CCL20) in serum and CSF of the prospectively recruited patients with TBE (n = 15), with non-TBE aseptic meningitis (n = 6) and in non-infected controls (n = 8). The data were analyzed with non-parametric tests, p < 0.05 considered significant. Monocyte CSF count correlated with other CSF inflammatory parameters, but not with the peripheral monocytosis, consistent with an active recruitment into CNS. The monocyte count did not correlate with a clinical presentation. The median CSF concentration of CCL7 and CXCL12 was increased in TBE, and that of CCL7 was higher in TBE than in non-TBE meningitis. The comparison of serum and CSF concentrations pointed to the intrathecal synthesis of CCL7 and CXCL12, but with no evident concentration gradients toward CSF. In conclusion, the monocytes are recruited into the intrathecal compartment in concert with other leukocyte populations in TBE. CCL7 and CXCL12 have been found upregulated intrathecally but are not likely to be the main monocyte chemoattractants.

Comparison of whole genomes of tick-borne encephalitis virus from mountainous alpine regions and regions with a lower altitude

Tick-borne encephalitis (TBE) has been a notifiable disease in Germany since 2001. Its causative agent, the TBE virus (TBEV), is the most important arbovirus in Europe and Northern Asia. The illness, caused by the European Subtype usually displays flu-like symptoms, but can result in sequelae and, in 2 % of all cases, in death. Over the last few decades, the virus has spread into new habitats, such as higher altitudes in the Alpine region. For this study, it was hypothesized that the environmental challenges that the virus might be exposed to at such altitudes could lead to the selection of viral strains with a higher resilience to such environmental factors. To determine whether strains identified at higher altitudes possessed different genetic traits compared to viruses from lower altitudes, an analysis of viral genomes from higher Alpine altitudes (> 500 m above sea level) (n = 5) and lower altitudes (< 500 m above sea level) (n = 4) was performed. No common phylogenetic ancestry or shared amino acid substitutions could be identified that differentiated the alpine from the lowland viral strains. These findings support the idea of many individual introductions of TBEV into the alpine region and the establishment of foci due to non-viral specific factors such as favorable conditions for vector species and host animals due to climate change.

Vaccination rate and adherence of tick-borne encephalitis vaccination in Germany

BACKGROUND

Tick-borne encephalitis (TBE) is an arboviral infection of the central nervous system. As there is no causal treatment of TBE, disease prevention by vaccination is especially important. Immunization consists of a three-dose primary vaccination schedule, followed by regular booster doses. In Germany, the Standing Committee on Vaccination (STIKO) at the Robert Koch-Institute recommends TBE vaccination for all those at high risk of contracting TBE. This includes individuals living in, traveling to and/or working in risk areas, and being exposed to ticks. To our knowledge, there are currently no reliable data on TBE vaccination rates in Germany available.

METHODS

This retrospective cohort study based on anonymized German health claims data was conducted to determine vaccination rates of TBE primary immunization in 2012 to 2015 by federal state, compliance with the vaccination schedule, and TBE vaccination uptake for the 2011 birth cohort. Vaccination protection rates for each federal state were simulated based on a compartmental model.

RESULTS

Vaccination rates of an initiated primary immunization ranged from about 3% in the southern federal states to <1% in the northern federal states. Across all federal states, compliance with the vaccination schedule decreased with each subsequent vaccination. Slightly higher TBE vaccination uptake was determined in the 2011 birth cohort, as compared to the German school entry health examination statistics in 2017. Simulated vaccination protection rates for each federal state ranged from 10% in Hamburg to 51% in Baden-Wuerttemberg.

CONCLUSIONS

While there was an overall low vaccination uptake and a discrepancy between areas of high vs. low TBE risk, this study also indicates a concerning decline in vaccination compliance. Vaccinating physicians should address the importance of adherence upon initiation of TBE vaccination.

What we know and still do not know about tick-borne encephalitis?

Tick-borne encephalitis (TBE) is a febrile illness caused by tick-borne encephalitis virus (TBEV), frequently manifesting as inflammation of the central nervous system. TBEV is a typical arbovirus, i.e., belongs to a group of viruses transmitted by blood-sucking arthropods. Taxonomically, TBEV is a member of the genus Flavivirus, family Flaviviridae. The disease is endemic in North Eurasia, from western Europe to East Asia. The virus occurs in natural foci of the disease all over Czechia, where it is transmitted predominantly by the castor bean tick (Ixodes ricinus). This infection has a potential to cause significant long-term disability affecting the quality of the patients life. Vaccine is available; however, vaccination coverage in Czechia is still low (around 30% of the total population). Lately, attention has been focused on new possibilities for early diagnosis and specific treatment, which so far has only been symptomatic or empirical.