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![Observed (grey bars) and predicted (red lines) Austrian tick-borne encephalitis series (left) and corresponding power spectra (right). GLM1: model using exclusively the human population NTOT as predictor variable resulting in a good approximation of the linear trend depicted by the black line. GLM2: model extended by the predictors net migration rate NMIG and Scandinavian index SI to explain low-frequency oscillations. GLM3: model extended by the beech fructification index 2 years prior Fyear−2 to explain also high-frequency oscillations. GLM4: best performance model extended by the annual sunshine duration SD. For each model the verification measures root-mean-square error (RMSE) and explained variance R² (with Radj2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$^{2}_{{adj}}$\end{document} in brackets) are given. Period 1979–2018](publication/342478771/figure/fig4/AS:962869550125065@1606577398394/Observed-grey-bars-and-predicted-red-lines-Austrian-tick-borne-encephalitis-series.png)
Observed (grey bars) and predicted (red lines) Austrian tick-borne encephalitis series (left) and corresponding power spectra (right). GLM1: model using exclusively the human population NTOT as predictor variable resulting in a good approximation of the linear trend depicted by the black line. GLM2: model extended by the predictors net migration rate NMIG and Scandinavian index SI to explain low-frequency oscillations. GLM3: model extended by the beech fructification index 2 years prior Fyear−2 to explain also high-frequency oscillations. GLM4: best performance model extended by the annual sunshine duration SD. For each model the verification measures root-mean-square error (RMSE) and explained variance R² (with Radj2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$^{2}_{{adj}}$\end{document} in brackets) are given. Period 1979–2018
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Background:
Why human tick-borne encephalitis (TBE) cases differ from year to year, in some years more 100%, has not been clarified, yet. The cause of the increasing or decreasing trends is also controversial. Austria is the only country in Europe where a 40-year TBE time series and an official vaccine coverage time series are available to investi...
Citations
... To reach this goal, a realistic appraisal of the amount of people exposed outdoors to tick bites is needed. Epidemiological modelling of TBDs relies on surrogates: it employs, for example, the fact that human outdoor/recreational activities are correlated with some environmental factors such as sunshine duration [40]; however, physical variables do not explain the population exposure completely enough for the given purpose. One alternative approach utilizes the fact that the amount of overnight accommodation booked by tourists (especially in rural destinations) closely follows the pattern of recreational/touristic activities [41]. ...
Until causal prophylaxis is available, the avoidance of ticks and personal protection provide the best insurance against contracting a tick-borne disease (TBD). To support public precaution, tick-activity forecasts (TAFs) based on weather projection are provided online for some regions/countries. This study—aimed at evaluating the efficacy of this preventative strategy—was conducted between 2015 and 2019, and included two countries where TAFs are issued regularly (Czech Republic, Germany) and two neighbouring countries for reference (Austria, Switzerland). Google Trends (GT) data were used to trace public concern with TAFs and related health information. GTs were compared with epidemiological data on TBD cases and tick bites, wherever available. Computer simulations of presumable effectiveness under various scenarios were performed. This study showed that public access to TAFs/preventive information is infrequent and not optimally distributed over the season. Interest arises very early in midwinter and then starts to fall in spring/summer when human–tick contacts culminate. Consequently, a greater number of TBD cases are contracted beyond the period of maximum public responsiveness to prevention guidance. Simulations, nevertheless, indicate that there is a potential for doubling the prevention yield if risk assessment, in addition to tick activity, subsumes the population’s exposure, and a real-time surrogate is proposed.
... TBEv is typically distributed in hotspots (foci of infection) characterized by high spatial and temporal variability. Numerous modelling studies have investigated how the presence of suitable habitat, climate conditions, and host availability influence the distribution of ticks and TBEv and the mechanisms of TBEv transmission [9][10][11][12][13][14][15][16] . www.nature.com/scientificreports/ ...
... Inter-annual variation in rodent density and their pathogens will influence the zoonotic risk to humans but the timing of increased risk relative to the mast event will differ among pathogens 29 . Thus, when the pathogen is transmitted by a tick with a multi-year life cycle, high rodent density caused by larger food availability leads to an increase in the number of infected nymphs the following year, and hence a greater incidence of human cases is expected to occur two years after the masting event 5,12,13,[30][31][32] . ...
... The link between tree masting, rodent population dynamics, density of nymphal ticks and eventually the incidence of tick-borne diseases in humans, has been investigated in several studies mainly correlating some climatic variables that regulate the mast event 33,34 or directly using a masting index to predict the incidence of TBE in humans 5,13,31 . The expected two-year lag between a masting event and the increase in (infected) nymphs density has been confirmed by several studies 10,[35][36][37] . ...
Tick-borne encephalitis (TBE) is caused by a flavivirus that infects animals including humans. In Europe, the TBE virus circulates enzootically in natural foci among ticks and rodent hosts. The abundance of ticks depends on the abundance of rodent hosts, which in turn depends on the availability of food resources, such as tree seeds. Trees can exhibit large inter-annual fluctuations in seed production (masting), which influences the abundance of rodents the following year, and the abundance of nymphal ticks two years later. Thus, the biology of this system predicts a 2-year time lag between masting and the incidence of tick-borne diseases such as TBE. As airborne pollen abundance is related to masting, we investigated whether inter-annual variation in pollen load could be directly correlated with inter-annual variation in the incidence of TBE in human populations with a 2-year time lag. We focused our study on the province of Trento (northern Italy), where 206 TBE cases were notified between 1992 and 2020. We tested the relationship between TBE incidence and pollen load collected from 1989 to 2020 for 7 different tree species common in our study area. Through univariate analysis we found that the pollen quantities recorded two years prior for two tree species, hop-hornbeam (Ostrya carpinifolia) and downy oak (Quercus pubescens), were positively correlated with TBE emergence (R² = 0.2) while a multivariate model with both tree species better explained the variation in annual TBE incidence (R² = 0.34). To the best of our knowledge, this is the first attempt at quantifying the correlation between pollen quantities and the incidence of TBE in human populations. As pollen loads are collected by widespread aerobiological networks using standardized procedures, our study could be easily replicated to test their potential as early warning system for TBE and other tick-borne diseases.
... They have been detected over many decades and are associated with such factors as demography, changes in land use and relevant density of organisms (population) in wilderness, and __________________________ Mishchenko V.A., Kshnyasev I.A., Davydova Yu.A., Vyalykh I.V., 2022 Vladimir A. Mishchenko people's recreational behavior. We should also remember that the climate change makes a significant contribution to the process as a possible driving force for cyclicity of TBErelated processes [4]. ...
Incidence of tick-borne encephalitis and other tick-borne infections correlates with a number of people applying for medical aid due to tick bites. Obviously, the number of registered tick bites is proportionate to people’s economic and recreational activities on an endemic territory and the quantity of hungry ticks. In its turn, the quantity of ticks depends on abundance of main hosts for blood-feeding stages but with a certain time lag caused by their life cycle parameters such as molting to the next stage, diapauses, and apparent seasonality in a continental boreal climate zone.
Our research goal was to analyze and synthesize an adequate formalized/parameterized statistical model to describe and predict risks of tick bites for population.
To describe dynamics and to predict a number of people bitten by ticks exemplified by the Sverdlovsk region, we used several linear (by parameters) logistic regression models. We applied a multimodel inference framework to assess whether the observed dynamics was described adequately. Long-tern dynamics of the number of people bitten by ticks in the Sverdlovsk region is characterized with an occurring high-amplitude slow long-wave oscillation (circadecadal one, with a quasi-period being approximately 10 years) and a short-wave 2–3-year cyclicity. The former may be associated with climatic rhythm and socioeconomic trends; the latter may be caused by biotic factors.
By using the logit-regression model, we showed that the number of small mammals, both in the previous year and at the beginning of the current tick activity season can be a valuable predictor of a risk for population to be bitten by ticks.
Predictive values of the created statistical model adequately describe an initial time series of chances/probabilities of tick bites.
... A recent paper has claimed that climate change plays only a minor role in the rising trend of Austrian TBE cases, and that population growth is the most probable cause of this trend. However, the authors state that this increase is probably a multifactorial phenomenon, with a complex interplay of factors that influence the dynamics of viral transmission in natural hosts, including climate change and human factors, such as risk exposure, better diagnostic capabilities, and population aging [18][19][20]. Furthermore, another study showed that other factors may explain the observed oscillation of the annual incidence of TBE in Austria. ...
... In their modelling study of a 40-year trend of TBE cases, they established that the main determinant of the variation in TBE incidence was the natural cycle of TBE transmission between rodents and ticks, which is driven by beech fructification. Population growth, net migration index, large-scale climate changes, and annual sunshine duration (as a proxy of human outdoor activity) may also contribute to the observed oscillations in annual TBE incidence [20]. ...
Tick-borne encephalitis (TBE) is endemic in several European countries, and its incidence has recently increased. Various factors may explain this phenomenon: social factors (changes in human behavior, duration and type of leisure activities and increased tourism in European high-risk areas), ecological factors (e.g., effects of climate change on the tick population and reservoir animals), and technological factors (improved diagnostics, increased medical awareness). Furthermore, the real burden of TBE is not completely known, as the performance of surveillance systems is suboptimal and cases of disease are under-reported in several areas. Given the potentially severe clinical course of the disease, the absence of any antiviral therapy, and the impossibility of interrupting the transmission of the virus in nature, vaccination is the mainstay of prevention and control. TBE vaccines are effective (protective effect of approximately 95% after completion of the basic vaccination—three doses) and well tolerated. However, their uptake in endemic areas is suboptimal. In the main endemic countries where vaccination is included in the national/regional immunization program (with reimbursed vaccination programs), this decision was driven by a cost-effectiveness assessment (CEA), which is a helpful tool in the decision-making process. All CEA studies conducted have demonstrated the cost-effectiveness of TBE vaccination. Unfortunately, CEA is still lacking in many endemic countries, including Italy. In the future, it will be necessary to fill this gap in order to introduce an effective vaccination strategy in endemic areas. Finally, raising awareness of TBE, its consequences and the benefit of vaccination is critical in order to increase vaccination coverage and reduce the burden of the disease.
... Future studies could continuously update our model and compare it to competing models over time to inspect model failures and make incremental improvements. This may be especially necessary when modelling tick paralysis or tick densities in general, as it is not uncommon for tick-borne disease cases to demonstrate 2-3 years cycles driven by the population dynamics of ticks [68]. There are a range of models that can incorporate multiple seasonalities, including the GAM and Prophet models we used here, and future work should investigate whether inclusion of these cycles improves near-term forecasts. ...
Tick paralysis resulting from bites from Ixodes holocyclus and I. cornuatus is one of the leading causes of emergency veterinary admissions for companion animals in Australia, often resulting in death if left untreated. Availability of timely information on periods of increased risk can help modulate behaviors that reduce exposures to ticks and improve awareness of owners for the need of lifesaving preventative ectoparasite treatment. Improved awareness of clinicians and pet owners about temporal changes in tick paralysis risk can be assisted by ecological forecasting frameworks that integrate environmental information into statistical time series models. Using an 11-year time series of tick paralysis cases from veterinary clinics in one of Australia's hotspots for the paralysis tick Ixodes holocyclus, we asked whether an ensemble model could accurately forecast clinical caseloads over near-term horizons. We fit a series of statistical time series (ARIMA, GARCH) and generative models (Prophet, Generalised Additive Model) using environmental variables as predictors, and then combined forecasts into a weighted ensemble to minimise prediction interval error. Our results indicate that variables related to temperature anomalies, levels of vegetation moisture and the Southern Oscillation Index can be useful for predicting tick paralysis admissions. Our model forecasted tick paralysis cases with exceptional accuracy while preserving epidemiological interpretability, outperforming a field-leading benchmark Exponential Smoothing model by reducing both point and prediction interval errors. Using online particle filtering to assimilate new observations and adjust forecast distributions when new data became available, our model adapted to changing temporal conditions and provided further reduced forecast errors. We expect our model pipeline to act as a platform for developing early warning systems that can notify clinicians and pet owners about heightened risks of environmentally driven veterinary conditions.
... The accumulated TBE cases officially reported in Austria, Germany and Switzerland are shown in Fig. 50 Rubel et al . (2020b) and the data used (supplemented here by the years 2019 and 2020) were documented by Rubel and Brugger (2020) . Exceptionally high TBE case numbers are presented for the COVID-19 year of 2020. It can be seen that despite the availability of efficient vaccines ( Heinz et al ., 2013 ), TBE cases in the GAR have risen sharply in recent deca ...
... Spectral analysis of TBE time series from Austria, Germany (the federal states of Bavaria and Baden-Wuerttemberg), Slovenia, the Czech Republic and Switzerland revealed that this oscillation is synchronized over Central Europe with a periodicity of 10-16 years, depending on the length of the time series considered ( Zeman, 2017a ). This is due to fluctuations in the large-scale atmospheric circulation patterns, which can be best described by the so-called Scandinavian index ( Rubel et al ., 2020b ). ...
... Superimposed on the trend and the lowfrequency oscillations are high-frequency oscillations with a period of 2-3 years. They represent fluctuations in the natural TBE transmission cycle between small mammals (rodents) and ticks, which is -in those countries where beech ( Fagus sylvatica ) is the dominant tree speciesassociated with the beech fructification two years previously ( Brugger et al ., 2018 ;Rubel et al ., 2020b ). ...
This book is a collection of 77 expert opinions arranged in three sections. Section 1 on "Climate" sets the scene, including predictions of future climate change, how climate change affects ecosystems, and how to model projections of the spatial distribution of ticks and tick-borne infections under different climate change scenarios. Section 2 on "Ticks" focuses on ticks (although tick-borne pathogens creep in) and whether or not changes in climate affect the tick biosphere, from physiology to ecology. Section 3 on "Disease" focuses on the tick-host-pathogen biosphere, ranging from the triangle of tick-host-pathogen molecular interactions to disease ecology in various regions and ecosystems of the world. Each of these three sections ends with a synopsis that aims to give a brief overview of all the expert opinions within the section. The book concludes with Section 4 (Final Synopsis and Future Predictions). This synopsis attempts to summarize evidence provided by the experts of tangible impacts of climate change on ticks and tick-borne infections. In constructing their expert opinions, contributors give their views on what the future might hold. The final synopsis provides a snapshot of their expert thoughts on the future.
... Given the importance of I. ricinus as a disease vector, forecasting the density of ticks questing for hosts is important for managing the risk of tick-borne diseases [15,16,38,39,[80][81][82]. In Europe, there is much interest in determining which ecological factors influence the seasonal and inter-annual abundance of I. ricinus ticks [15,38]. ...
Background: The tick Ixodes ricinus is an important vector of tick-borne diseases including Lyme borreliosis. In continental Europe, the nymphal stage of I. ricinus often has a bimodal phenology with a large spring peak and a smaller fall peak. There is consensus about the origin of the spring nymphal peak, but there are two alternative hypotheses for
the fall nymphal peak. In the direct development hypothesis, larvae quest as nymphs in the fall of the same year that they obtained their larval blood meal. In the developmental diapause hypothesis, larvae overwinter in the engorged state and quest as nymphs one year after they obtained their larval blood meal. These two hypotheses make different
predictions about the time lags that separate the larval blood meal and the density of questing nymphs (DON) in the spring and fall.
Methods: Inter-annual variation in seed production (masting) by deciduous trees is a time-lagged index for the density of vertebrate hosts (e.g., rodents) which provide blood meals for larval ticks. We used a long-term data set on the masting of the European beech tree and a 15-year study on the DON at 4 different elevation sites in western Switzerland
to differentiate between the two alternative hypotheses for the origin of the fall nymphal peak.
Results: Questing I. ricinus nymphs had a bimodal phenology at the three lower elevation sites, but a unimodal phenology at the top elevation site. At the lower elevation sites, the DON in the fall was strongly correlated with the DON in the spring of the following year. The inter-annual variation in the densities of I. ricinus nymphs in the fall and spring
was best explained by a 1-year versus a 2-year time lag with the beech tree masting index. Fall nymphs had higher fat content than spring nymphs indicating that they were younger. All these observations are consistent with the direct development hypothesis for the fall peak of I. ricinus nymphs at our study site. Our study provides new insight into the
complex bimodal phenology of this important disease vector.
Conclusions: Public health officials in Europe should be aware that following a strong mast year, the DON will increase 1 year later in the fall and 2 years later in the spring. Studies of I. ricinus populations with a bimodal phenology should consider that the spring and fall peak in the same calendar year represent different generations of ticks.
... pogodowe) jak i wewnętrzne -zmiany ekosystemu czynnika chorobotwórczego (9). Zmienność składników pogody, jak choćby liczba dni słonecznych, może wpływać na skłonność ludzi do korzystania z aktywności na świeżym powietrzu, co przekłada się na liczbę zachorowań na kzm (12). Istotną rolę mogą mieć okresowe wahania dostępności pożywienia dla kluczowego rezerwuaru zwierzęcego, w tym przypadku małych ssaków. ...
... Cykle o różnych przyczynach mogą nakładać się na siebie, ostatecznie powodując wypadkową obserwowaną zmienność zapadalności. Powyższe obserwacje mogą być podstawą prognozowania liczby zachorowań w nadchodzących latach (12)(13)(14). Dane dotyczące zapadalności na kzm w obrębie Federacji Rosyjskiej obejmują okres ponad 80 lat i są podstawą do przewidywania liczby przy- ...
... weather) and internal factors -changes in the pathogen's ecosystem (9). The variability of weather components, such as the number of sunny days, may affect the tendency of people to perform outdoor activities, which translates into the number of people suffering from TBE (12). Periodic fluctuations in food availability for a key animal reservoir, in this case small mammals, may play an important role. ...
Introduction:
Tick-borne encephalitis (TBE) is endemic in many parts of Eurasia including countries previously considered to be free from the disease. The incidence of TBE is changing owing to various ecological and climatic factors. The factors influencing the variability of the number of TBE cases are still under investigation. In 2020 the new coronavirus SARS-CoV-2 emerged causing COVID-19 pandemic. Governments have reorganized health care systems to contain a surge of COVID-19 cases and avoid hospital overload. Moreover, new measures have modified several aspects of social habits leading to a change in the incidence of numerous diseases. We aimed to evaluate the epidemiology of TBE in the last decade (2010-2019) and to demonstrate the impact of the surge of SARS-CoV-2 infections on the TBE incidence as reported to a national surveillance database.
Material and methods:
We performed the analysis of the TBE notification from the epidemiologic reports in the years 2010-2019 and in the pandemic year 2020 at a national and regional level in Poland. We included data from two infectious disease departments located in the most TBE-prevalent province of Poland.
Results:
Most cases of TBE occur in two provinces of Northeastern Poland from May to December. The increasing temporal trend occurred in Poland in 2016-2017. The increased number of cases of COVID-19 coincided with a reduction of the number of the reported TBE cases in 2020.
Conclusions:
Tick-borne encephalitis virus activity in Poland is invariably concentrated in endemic regions of Northeastern Poland fluctuating considerably from year to year. The decrease of TBE incidence with surge of COVID-19 patients conceivably resulted from underreporting due to limited access to specialized diagnostics. In endemic areas, TBE should be included in the differential diagnostics in all the cases when the central nervous system infection in suspected.
... Another reason is the vaccination coverage which varies widely between various regions in Europe [43]. For example, Austria population has a vaccination coverage of more than 80% (fraction of the population which received at least one TBE vaccination, i.e., ≥1 vaccine dose) since the end of the nineties and this has led to a significant decline in the annual number of human TBE cases [44,45]. ...
Tick-borne encephalitis (TBE) is the most common viral tick-borne disease in Europe causing thousands of human infections every year. Available risk maps in Europe are solely based on human incidences, but often underestimate areas with TBE virus circulation as shown by several autochthonous cases detected outside known risk areas. A dataset of more than 1300 georeferenced TBE virus detections in ticks and mammals except for humans was compiled and used to estimate the probability of TBE virus presence in Europe. For this, a random forests model was implemented using temperature- and precipitation-dependent bioclimatic variables of the WorldClim dataset, altitude, as well as land cover of the ESA GlobCover dataset. The highest probabilities of TBE virus presence were identified in Central Europe, in the south of the Nordic countries, and in the Baltic countries. The model performance was evaluated by an out-of-bag error (OOB) of 0.174 and a high area under the curve value (AUC) of 0.905. The TBE virus presence maps may subsequently be used to estimate the risk of TBE virus infections in humans and can support decision-makers to identify TBE risk areas and to encourage people to take appropriate actions against tick bites and TBE virus infections.
... It is therefore not surprising that TBE incidence series of the three countries are very similar. High-frequency-oscillations in TBE incidence series are best described by the fructification index of the European beech (Fagus sylvatica), while low-frequency oscillations may be described by the large-scale atmospheric circulation patterns represented by the Scandinavian index (Rubel et al., 2020). Both beech fructification index and Scandinavian index are to a certain extent synchronized over Central Europe. ...
The forecast of human tick-borne encephalitis (TBE) incidence for the next years has been on the research agenda of epidemiologists since the discovery of this tick-borne zoonosis. Based on models to explain the trend as well as the low- and high-frequency oscillations in the Austrian TBE incidence series, TBE forecasts for Austria, Germany and Switzerland are presented here. For this purpose, generalized linear models (GLMs) of type negative binomial regression were calibrated with the TBE incidences of the period 1991–2018 to forecast the TBE incidences 2019 and 2020. The GLMs require only 4–5 predictors, 2 of which are large-scale synchronized over Central Europe and used for all 3 countries. Predictors used include the demographic parameters total population and net migration rate, the Scandinavian index which describes the large-scale atmospheric circulation patterns, the fructification index of the European beech (Fagus sylvatica) 2 years prior as a proxy for the intensity of the TBE virus transmission cycle, and the national TBE vaccination coverage. Since an official time series of TBE vaccination coverage is only available for Austria, the missing TBE vaccination coverages of Germany and Switzerland were reconstructed and presented as the first results. Model verification results in explained variances of 76 % for Austria, 84 % for Germany, and 89 % for Switzerland. Thus, the best model fit was determined for the Swiss GLM which is able to predict the TBE incidence with a root-mean-square error of RMSE=25 cases (19 % of the mean TBE incidence 1991–2018 or 7 % of the TBE incidence of 2018). Forecasting TBE incidences for 2019 and 2020 results in 92±12 and 142±26 TBE cases for Austria, 417±71 and 670±168 TBE cases for Germany as well as 235±30 and 465±91 TBE cases for Switzerland.
