Comparison of tick-borne encephalitis between children and adults-analysis of 669 patients

Trends in emerging vector-borne viral infections and their outcome in children over two decades

This review utilizes quatitative methods and bibliometric data to analyse the trends of emerging and re-emerging vector-borne diseases, with a focus on their impact on pediatric population. To conduct this analysis, a systematic search of PubMed articles from the past two decades was performed, specifically looking at 26 different vector-borne viruses listed in WHO and CDC list of vector-borne viruses. The review found that diseases like Dengue, Zika, West Nile, and Chikungunya were frequently discussed in the literature. On the other hand, diseases such as Tick-borne encephalitis, Rift Valley fever, Venezuelan equine encephalitis, Sindbis fever, Venezuelan equine encephalitis, Ross River virus, and Eastern equine encephalitis showed an upward trend in publications, indicating potential resurgence. In addition to discussing trends and patterns, the review delves into the clinical manifestations and long-term effects of the top 10 viruses in children. It highlights various factors including deforestation, urbanization, global travel, and immunosuppression that contribute to disease emergence and resurgence. To effectively combat these vector-borne diseases, continuous surveillance is crucial. The review also emphasizes the importance of increased vaccination efforts and targeted research to address the health challenges they pose. IMPACT: This review employs quantitative analysis of publications to elucidate trends in emerging pediatric vector-borne viral diseases over two decades. Dengue, the most prevalent of these diseases, has spread to new regions. New strains of Japanese Encephalitis have caused outbreaks. Resurgence of Tick-borne Encephalitis, West Nile, and Yellow Fever due to vaccine hesitancy has also transpired. Continuous global surveillance, increased vaccination, and research into novel therapeutics are imperative to combat the substantial morbidity and mortality burden these diseases pose for children worldwide.

Tick-Borne Encephalitis Vaccine: Recommendations of the Advisory Committee on Immunization Practices, United States, 2023

Tick-borne encephalitis (TBE) virus is focally endemic in parts of Europe and Asia. The virus is primarily transmitted to humans by the bites of infected

Ixodes species ticks but can also be acquired less frequently by alimentary transmission. Other rare modes of transmission include through breastfeeding, blood transfusion, solid organ transplantation, and slaughtering of viremic animals. TBE virus can cause acute neurologic disease, which usually results in hospitalization, often permanent neurologic or cognitive sequelae, and sometimes death. TBE virus infection is a risk for certain travelers and for laboratory workers who work with the virus. In August 2021, the Food and Drug Administration approved Ticovac TBE vaccine for use among persons aged ≥1 year. This report summarizes the epidemiology of and risks for infection with TBE virus, provides information on the immunogenicity and safety of TBE vaccine, and summarizes the recommendations of the Advisory Committee on Immunization Practices (ACIP) for use of TBE vaccine among U.S. travelers and laboratory workers.

The risk for TBE for most U.S. travelers to areas where the disease is endemic is very low. The risk for exposure to infected ticks is highest for persons who are in areas where TBE is endemic during the main TBE virus transmission season of April–November and who are planning to engage in recreational activities in woodland habitats or who might be occupationally exposed. All persons who travel to areas where TBE is endemic should be advised to take precautions to avoid tick bites and to avoid the consumption of unpasteurized dairy products because alimentary transmission of TBE virus can occur. TBE vaccine can further reduce infection risk and might be indicated for certain persons who are at higher risk for TBE. The key factors in the risk-benefit assessment for vaccination are likelihood of exposure to ticks based on activities and itinerary (e.g., location, rurality, season, and duration of travel or residence). Other risk-benefit considerations should include 1) the rare occurrence of TBE but its potentially high morbidity and mortality, 2) the higher risk for severe disease among certain persons (e.g., older persons aged ≥60 years), 3) the availability of an effective vaccine, 4) the possibility but low probability of serious adverse events after vaccination, 5) the likelihood of future travel to areas where TBE is endemic, and 6) personal perception and tolerance of risk

ACIP recommends TBE vaccine for U.S. persons who are moving or traveling to an area where the disease is endemic and will have extensive exposure to ticks based on their planned outdoor activities and itinerary. Extensive exposure can be considered based on the duration of travel and frequency of exposure and might include shorter-term (e.g., <1 month) travelers with daily or frequent exposure or longer-term travelers with regular (e.g., a few times a month) exposure to environments that might harbor infected ticks. In addition, TBE vaccine may be considered for persons who might engage in outdoor activities in areas where ticks are likely to be found, with a decision to vaccinate made on the basis of an assessment of their planned activities and itinerary, risk factors for a poor medical outcome, and personal perception and tolerance of risk. In the laboratory setting, ACIP recommends TBE vaccine for laboratory workers with a potential for exposure to TBE virus

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.

High neutralizing antibody mismatch as a possible reason for vaccine failure in two children with severe tick-borne encephalitis

We describe two adolescents (13 and 16 years old) with severe tick-borne encephalitis (TBE) and vaccination breakthrough (VBT). Both suffer from severe persistent neurologic sequelae. Both patients had high TBE-IgG-titers after vaccination at the beginning of the infection and a low or missing TBE-IgM response (Type 2 vaccine failure). Neutralization tests show low titers against the respective infecting TBE virus strain and higher titers against the vaccine strain at the beginning of the infection implying an individual weak or impaired immune response to the respective virus as possible cause of TBE vaccine failure. We do not know of any similar observation or explanation for the phenomenon and at the moment can only speculate of a severe course correlated to highly mismatched IgG. This constellation of high TBE IgGs, the lack of immune response and a severe course strongly resembles the severe TBE courses that occurred in the past after TBE immunoglobulin administration. To our knowledge differentiation between structural and functional antibodies by neutralization tests with a) the affecting TBE virus strain and b) the vaccine virus strain in TBE vaccine failures has never been described before. We conclude (1) to consider a TBE virus infection also in vaccinated children presenting with meningoencephalitis, (2) to perform a broad immunological work-up in severe TBE especially after VBT, (3) to further study if high mismatch IgG's are a possible reason for vaccine failure.

Tick-borne encephalitis in pediatrics: An often overlooked diagnosis

Tick-borne encephalitis (TBE) is a vector-borne disease caused by a flavivirus, the tick-borne encephalitis virus (TBEV), and transmitted by the bite of infected Ixodes ricinus ticks. The European subtype (TBEV-Eu) is endemic in 27 European countries. During the last decade, increased TBE incidence was observed in many countries, including some of those believed to be of low endemicity/devoid of TBEV circulation. However, data dealing with TBE in children are far less profuse than with adults. Historically, children are known to have mild TBEV infection with favorable outcomes. That said, recent case reports and observational studies on pediatric cohorts have challenged this point of view. Like adults, children may present severe forms and fail to completely recover following TBE infection, at times leading to long-term cognitive impairment. In this review, we comprehensively describe the incidence, exposure factors, and transmission routes of TBEV in children, as well as the clinical and biological manifestations of TBE and imaging findings in this population. We also harness new data on long-term outcomes and sequelae in pediatric cohorts. Finally, we provide an overview of vaccination recommendations for children in European countries.

Tick-borne encephalitis affects sleep–wake behavior and locomotion in infant rats

Background/Aims

Tick-borne encephalitis (TBE) is a disease affecting the central nervous system. Over the last decade, the incidence of TBE has steadily increased in Europe and Asia despite the availably of effective vaccines. Up to 50% of patients after TBE suffer from post-encephalitic syndrome that may develop into long-lasting morbidity. Altered sleep–wake functions have been reported by patients after TBE. The mechanisms causing these disorders in TBE are largely unknown to date. As a first step toward a better understanding of the pathology of TBEV-inducing sleep dysfunctions, we assessed parameters of sleep structure in an established infant rat model of TBE.

Methods

13-day old Wistar rats were infected with 1 × 10⁶ FFU Langat virus (LGTV). On day 4, 9, and 21 post infection, Rotarod (balance and motor coordination) and open field tests (general locomotor activity) were performed and brains from representative animals were collected in each subgroup. On day 28 the animals were implanted with a telemetric EEG/EMG system. Sleep recording was continuously performed for 24 consecutive hours starting at day 38 post infection and visually scored for Wake, NREM, and REM in 4 s epochs.

Results

As a novelty of this study, infected animals showed a significant larger percentage of time spend awake during the dark phase and less NREM and REM compared to the control animals (p < 0.01 for all comparisons). Furthermore, it was seen, that during the dark phase the wake bout length in infected animals was prolonged (p = 0.043) and the fragmentation index decreased (p = 0.0085) in comparison to the control animals. LGTV-infected animals additionally showed a reduced rotarod performance ability at day 4 (p = 0.0011) and day 9 (p = 0.0055) and day 21 (p = 0.0037). A lower locomotor activity was also seen at day 4 (p = 0.0196) and day 9 (p = 0.0473).

Conclusion

Our data show that experimental TBE in infant rats affects sleep–wake behavior, leads to decreased spontaneous locomotor activity, and impaired moto-coordinative function.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00859-7.

A Retrospective Analysis of Tick-borne Encephalitis in Children Treated in Kaunas Hospital During 2012 to 2019

BACKGROUND

Lithuania has the highest tick-borne encephalitis (TBE) rates in Europe. Although TBE incidence in children is lower, it may still cause long-term consequences. So far pediatric epidemiological and clinical characteristics of TBE in Lithuania were not described.

METHODS

We performed a retrospective analysis of 87 cases of children who were hospitalized for TBE in Kaunas Hospital of the Lithuanian University of Health Sciences from 2012 to 2019. Each case was identified with neurological symptoms and positive serological tests.

RESULTS

Around half of the children (50.6%) reported having a tick bite, whereas 6.9% stated having exposure to unpasteurized milk. Biphasic course of the disease occurred in 70.1% of the cases. The most common clinical symptoms were headache (100%), fever (100%), nausea (85.1%), vomiting (78.2%), drowsiness (67.8%) and general weakness (66.7%). Meningeal symptoms were present in 93.1% of the cases, and 93.1% of the children had at least one focal neurological sign (tremor 82.3%, impaired balance 73.6%). Isolated meningitis was diagnosed in 57.5%, meningoencephalitis in 41.4% and meningoencephalomyelitis in 1.1% of the cases. Majority of younger children (1-8 years old) had meningitis (77.3%), whereas 49.2% of older children (9-17 years old) had more severe forms of TBE. Cerebrospinal fluid pleocytosis was found in 94.3% of cases (average white blood cell count: 111.7 per μL, protein: 0.5 g/L). Higher levels of cerebrospinal fluid protein were associated with more severe forms of TBE and older age. Duration of the symptomatic disease lasted ≈11 days. Early residual signs were observed in 75.9% of all cases.

CONCLUSIONS

The epidemiological and clinical characteristics of TBE in children in Lithuania are similar to those described in other countries. Only half of the subjects reported having a tick bite. Younger children tend to suffer from meningoencephalitis and meningoencephalomyelitis less frequently than elder ones. Focal neurological signs were commonly observed. Majority of children had lasting symptoms of TBE upon discharge from the hospital.

Babesiosis in Southeastern, Central and Northeastern Europe: An Emerging and Re-Emerging Tick-Borne Disease of Humans and Animals

There is now considerable evidence that in Europe, babesiosis is an emerging infectious disease, with some of the causative species spreading as a consequence of the increasing range of their tick vector hosts. In this review, we summarize both the historic records and recent findings on the occurrence and incidence of babesiosis in 20 European countries located in southeastern Europe (Bosnia and Herzegovina, Croatia, and Serbia), central Europe (Austria, the Czech Republic, Germany, Hungary, Luxembourg, Poland, Slovakia, Slovenia, and Switzerland), and northern and northeastern Europe (Lithuania, Latvia, Estonia, Iceland, Denmark, Finland, Sweden, and Norway), identified in humans and selected species of domesticated animals (cats, dogs, horses, and cattle). Recorded cases of human babesiosis are still rare, but their number is expected to rise in the coming years. This is because of the widespread and longer seasonal activity of Ixodes ricinus as a result of climate change and because of the more extensive use of better molecular diagnostic methods. Bovine babesiosis has a re-emerging potential because of the likely loss of herd immunity, while canine babesiosis is rapidly expanding in central and northeastern Europe, its occurrence correlating with the rapid, successful expansion of the ornate dog tick (Dermacentor reticulatus) populations in Europe. Taken together, our analysis of the available reports shows clear evidence of an increasing annual incidence of babesiosis across Europe in both humans and animals that is changing in line with similar increases in the incidence of other tick-borne diseases. This situation is of major concern, and we recommend more extensive and frequent, standardized monitoring using a "One Health" approach.

Plasma Proteomic Profile of Patients with Tick-Borne Encephalitis and Co-Infections

Despite the increasing number of patients suffering from tick-borne encephalitis (TBE), Lyme disease, and their co-infection, the mechanisms of the development of these diseases and their effects on the human body are still unknown. Therefore, the aim of this study was to evaluate the changes in the proteomic profile of human plasma induced by the development of TBE and to compare it with changes in TBE patients co-infected with other tick-borne pathogens. The results obtained by proteomic analysis using a nanoLC-Q Exactive HF mass spectrometer showed that the most highly elevated groups of proteins in the plasma of TBE patients with co-infection were involved in the pro-inflammatory response and protein degradation, while the antioxidant proteins and factors responsible for protein biosynthesis were mainly downregulated. These results were accompanied by enhanced GSH- and 4-HNE-protein adducts formation, observed in TBE and co-infected patients at a higher level than in the case of patients with only TBE. In conclusion, the differences in the proteomic profiles between patients with TBE and co-infected patients indicate that these diseases are significantly diverse and, consequently, require different treatment, which is particularly important for further research, including the development of novel diagnostics tools.

Incidence of Tick-Borne Encephalitis during the COVID-19 Pandemic in Selected European Countries

Ixodes ricinus ticks are one of the most important vectors and reservoirs of infectious diseases in Europe, and tick-borne encephalitis (TBE) is one of the most dangerous human diseases transmitted by these vectors. The aim of the present study was to investigate the TBE incidence in some European countries during the COVID-19 pandemic. To this end, we analyzed the data published by the European Center for Disease Prevention and Control (ECDC) and Eurostat on the number of reported TBE and COVID-19 cases in 2020 and TBE cases in 2015–2019 (reference period). Significant differences in the TBE incidence were found between the analyzed countries. The highest TBE incidence was found in Lithuania (25.45/100,000 inhabitants). A high TBE incidence was also observed in Central European countries. In 12 of the 23 analyzed countries, there was significant increase in TBE incidence during the COVID-19 pandemic during 2020 compared to 2015–2019. There was no correlation between the incidence of COVID-19 and TBE and between the availability of medical personnel and TBE incidence in the studied countries. In conclusion, Central Europe and the Baltic countries are areas with a high risk of TBE infection. Despite the COVID-19 pandemic and imposed restrictions, the incidence of TBE is increasing in more than half of the analyzed countries.

Clinical Characteristics of Patients with Tick-Borne Encephalitis (TBE): A European Multicentre Study from 2010 to 2017

Tick-borne encephalitis (TBE) virus is a major cause of central nervous system infections in endemic countries. Here, we present clinical and laboratory characteristics of a large international cohort of patients with confirmed TBE using a uniform clinical protocol. Patients were recruited in eight centers from six European countries between 2010 and 2017. A detailed description of clinical signs and symptoms was recorded. The obtained information enabled a reliable classification in 553 of 555 patients: 207 (37.3%) had meningitis, 273 (49.2%) meningoencephalitis, 15 (2.7%) meningomyelitis, and 58 (10.5%) meningoencephalomyelitis; 41 (7.4%) patients had a peripheral paresis of extremities, 13 (2.3%) a central paresis of extremities, and 25 (4.5%) had single or multiple cranial nerve palsies. Five (0.9%) patients died during acute illness. Outcome at discharge was recorded in 298 patients. Of 176 (59.1%) patients with incomplete recovery, 80 (27%) displayed persisting symptoms or signs without recovery expectation. This study provides further evidence that TBE is a severe disease with a large proportion of patients with incomplete recovery. We suggest monitoring TBE in endemic European countries using a uniform protocol to record the full clinical spectrum of the disease.

Microbiological Outcomes Associated With Low Leukocyte Counts in Cerebrospinal Fluid

The significance of low leukocyte counts in cerebrospinal fluid (CSF) remains unclear. We performed a 2-year retrospective study to examine microbiological outcomes associated with CSF leukocytes at 6–10/mm³. Of the 178 samples examined, we detected positive results for 11 samples, including 5 cases of tick-borne encephalitis virus infection.