Climate Warming and Tick-borne Encephalitis, Slovakia (original) (raw)
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Central European journal of public health, 2008
The steep rise in the incidence of tick-borne encephalitis (TBE) in the 1990s and its subsequent high level in the Czech Republic are not even over the whole territory. It is manifested markedly in the Czech-Moravian Highland region. In the decades of 1971 through 1992, TBE incidence in the Highland Region did not reach the countrywide average. The rise has been noted only since 1997; in the year 2006 TBE incidence in that administrative region was more than double the countrywide average. Analysis of the situation have not found any socio-economic shifts or land-use changes, or in the numbers of game animals, that could have had an effect on TBE incidence. The rise of infections in localities 500 m above sea level (a.s.l.) and more was markedly steeper than that below that altitudinal limit. At those altitudes there has been found an increase in average monthly temperatures exceeding countrywide averages namely in the period of maximum Ixodes ricinus activity (May-August). Detailed...
International Journal of Medical Microbiology Supplements, 2004
The geographic/temporal pattern of cases of tick-borne encephalitis (TBE) registered in the Czech Republic since 1970 was analysed to verify the surmise of a global warming effect. Using a geographic information system, over 8,700 notified places of infection were pinpointed on a map and overlaid with a digital elevation model to estimate the vertical distribution of the cases. Series of yearly disease ceilings (assessed alternatively as the respective maximum altitude or mean altitudes of the upper 5 or 10 cases) were tested against the null hypothesis of random elevation course and analysed for correlation with concomitant factors (yearly TBE incidence rate, mean yearly temperature, population density of small rodents and roe deer). Statistical tests proved that the TBE ceiling has gradually moved upwards in the course of the last three decades. The average rate of ascension within this period was approx. 5.4 + 1.7 m yearly, which corresponds well with concurrent mean temperature rising of approx. 0.036 • 0.007°C yearly, and the vertical temperature gradient of 0.0065 + 0.0004°C m-1. The TBE-ceiling estimates significantly correlated with TBEincidence data and the mean yearly temperature recorded 1-2 years earlier. Although TBE incidence correlated with rodent population density that was observed 1-2 years earlier, the TBE ceiling does not seem to be influenced by rodent population dynamics nor did the population dynamics correlate with mean yearly temperatures. TBE incidence as well as mean altitudes of the upper 10 cases also correlated with official data on harvested roe deer. Overall, the fluctuations of TBE incidence and TBE ceiling proved to be synchronous processes that correspond with temperature changes. Although the dependence of TBE on temperature is not a direct one and various factors could be involved, an impact of climate warming on the vertical disease distribution in Central Europe is evident.
Climate Change Cannot Explain the Upsurge of Tick-Borne Encephalitis in the Baltics
PLoS ONE, 2007
Background. Pathogens transmitted by ticks cause human disease on a greater scale than any other vector-borne infections in Europe, and have increased dramatically over the past 2-3 decades. Reliable records of tick-borne encephalitis (TBE) since 1970 show an especially sharp upsurge in cases in Eastern Europe coincident with the end of Soviet rule, including the three Baltic countries, Estonia, Latvia and Lithuania, where national incidence increased from 1992 to 1993 by 64, 175 and 1,065%, respectively. At the county level within each country, however, the timing and degree of increase showed marked heterogeneity. Climate has also changed over this period, prompting an almost universal assumption of causality. For the first time, we analyse climate and TBE epidemiology at sufficiently fine spatial and temporal resolution to question this assumption. Methodology/Principal Finding. Detailed analysis of instrumental records of climate has revealed a significant step increase in spring-time daily maximum temperatures in 1989. The seasonal timing and precise level of this warming were indeed such as could promote the transmission of TBE virus between larval and nymphal ticks co-feeding on rodents. These changes in climate, however, are virtually uniform across the Baltic region and cannot therefore explain the marked spatio-temporal heterogeneity in TBE epidemiology. Conclusions/Significance. Instead, it is proposed that climate is just one of many different types of factors, many arising from the socio-economic transition associated with the end of Soviet rule, that have acted synergistically to increase both the abundance of infected ticks and the exposure of humans to these ticks. Understanding the precise differential contribution of each factor as a cause of the observed epidemiological heterogeneity will help direct control strategies.
Tick-borne encephalitis virus expansion to higher altitudes correlated with climate warming
International Journal of Medical Microbiology, 2008
Since 2002, the expansion of Ixodes ricinus ticks and tick-borne infection agents have been studied in the Krkonosˇe Mts., Czech Republic. Tick-borne encephalitis virus was detected by means of RT-PCR. In 2003, it was detected in 2 out of 491 ticks at 620 and 710-720 m a.s.l., respectively, and in 3 out of 939 ticks at 600 m a.s.l. at the same locality in 2004. In 2005, tick-borne encephalitis virus was detected in 5 out of 295 ticks at 900-1100 m a.s.l., which is above the formerly known altitudinal limit of I. ricinus distribution. The reason for that could be found in the changing climate. Based on the meteorological data collected in the Krkonosˇe Mts., 1961-2005, there was a significant increase in the mean annual temperature (1.3-1.4 1C) over that period, namely by 2-3.5 1C in May through August. Thus, with respect to the average vertical temperature gradient in summer of about 0.6 1C/100 m, 2 1C correspond to 300-350 m in altitude, and accordingly 3.5 1C correspond to a shift in altitude of approximately 550-600 m, that being in accordance with environmental conditions of the former I. ricinus altitudinal limit confirmed in the Krkonosˇe Mts. 20 years ago. r
BMC Infectious Diseases, 2020
Background Impact of climate change on tick-borne encephalitis (TBE) prevalence in the tick-host enzootic cycle in a given region depends on how the region-specific climate change patterns influence tick population development processes and tick-borne encephalitis virus (TBEV) transmission dynamics involving both systemic and co-feeding transmission routes. Predicting the transmission risk of TBEV in the enzootic cycle with projected climate conditions is essential for planning public health interventions including vaccination programs to mitigate the TBE incidence in the inhabitants and travelers. We have previously developed and validated a mathematical model for retroactive analysis of weather fluctuation on TBE prevalence in Hungary, and we aim to show in this research that this model provides an effective tool for projecting TBEV transmission risk in the enzootic cycle. Methods Using the established model of TBEV transmission and the climate predictions of the Vas county in wes...
Tick-borne encephalitis in the Baltic States: Identifying risk factors in space and time
International Journal of Medical Microbiology, 2006
This paper presents preliminary results in our investigations of the biological (abiotic and biotic) and non-biological causes of the spatial heterogeneity and temporal change of tick-borne encephalitis (TBE), both within and between Estonia, Latvia, and Lithuania. Spatial analysis revealed that the land cover and precise seasonal patterns of climatic indices (temperature and normalized difference vegetation index) can explain 55% of the observed spatial variation in TBE incidence over the period 1993-98 across all the Baltic States. Temporal analysis of climatic variables indicates a very specific change in spring temperature conditions from 1993 onwards that could enhance the transmission of TBE virus. Further time series analysis of climate, together with analysis of biotic factors, socio-economic conditions, and human behaviour is being undertaken to explain the epidemiological patterns more fully.
Climate and Tickborne Encephalitis
Conservation Ecology, 1998
Climatic changes are projected to alter the abundance, dynamics, and geographical distribution of many vectorborne diseases in human populations. Tick-borne diseases such as Lyme disease and tick-borne encephalitis (TBE) are a growing concern in northern Europe and the United States. The impact of a future climate change on the transmission of tick-borne diseases is not known. To make such assumptions, more empirical data are needed on the relations between short-term fluctuations in contemporary weather and disease incidence. This paper analyzes relations between daily minimum and maximum temperatures, monthly precipitation, and TBE incidence during a 36-yr period in Stockholm County, a high-endemic region for TBE in Sweden. Multiple regression analyses were performed, with temperature variables expressed as number of days per winter or spring-summer-fall season with temperatures above, below, or in the interval between different temperature limits. The limits used for daily minimum temperatures represent bioclimatic thresholds of importance for pathogen transmission. To adjust for the length of the tick's life cycle, each TBE incidence rate was related to meteorological data over two consecutive years. Results reveal that increased incidence of tick-borne encephalitis is related to a combination of two successive years of more days with temperatures permitting prolonged seasonal tick activity and, hence, pathogen transmission (i.e., daily minimum temperatures above 5ºC-10ºC), and a mild winter preceding the year before the incidence year (i.e., fewer winter days with minimum temperatures below-7ºC). Alternative explanations of the results are discussed. Findings of this study suggest that a climate change may extend the seasonal range and intensify the endemicity of tickborne diseases, in particular, at northern latitudes.
Ticks and Tick-borne Diseases, 2010
A marked increase in tick-borne encephalitis (TBE) incidence has been observed in Europe during the last 2 decades. Hypothetical causes include global climatic fluctuations, human-induced environmental changes, and socioeconomic changes. These factors are thought to be disproportionately relevant in different geographical areas. To date, epidemiological studies of this phenomenon were based primarily on aggregated data, and little is known about TBE dynamics on the detailed geographical scale. This study is aimed at the subregional variations of incidence of TBE in the Czech Republic. The methodology of spatial statistics was applied. Over 13,000 cases of TBE, registered 1971-2007, were pinpointed on a GIS map and analysed for density variations in both time and space. Selected areas were studied in detail, using time series analysis. These analyses revealed that the incidence of TBE was highly variable both across the country and over the study period. Although the aggregate total of reported cases were generally increasing, local trends were divergent. A detailed study of one endemic area (that one with the highest case density level) showed that heterogeneities are detectable, even on a very fine geographical scale. There was no evident spatial coherence of the TBE trends; and some adjacent areas showed quite differing trends. However, countrywide coherence was demonstrated for quasi-octennial fluctuations in the TBE series, associable with the North Atlantic oscillation. The possible influences of both various climatic and population covariates upon TBE occurrence are discussed. However, the geographical heterogeneity of the disease trends, at such a fine spatial scale, cannot be explained satisfactorily by fluctuations in climatic or socioeconomic conditions.
Sudden increase in tick-borne encephalitis cases in the Czech Republic, 2006
International Journal of Medical Microbiology, 2008
In the year 1993, there was a great increase in the number of tick-borne encephalitis (TBE) cases in the Czech Republic, and this high level has persisted with certain fluctuations. In the period 1965-1992, there were 8690 cases (annual average: 310.4), whereas there were 8674 registered cases in the years 1993-2006 (annual average: 619.6). In 2006, there was an exceptionally sudden increase with 1029 registered TBE cases, i.e., the national incidence was 10/100,000, the highest level recorded so far. It is documented that this situation was significantly influenced by exceptional weather in 2006. During the warm and rainy spring and early summer period (April-June), high hostseeking activity of Ixodes ricinus was recorded and also a high incidence of TBE resulting in a typical spring/summer peak of disease (June/July). There was a sudden break in the weather and a cool August followed (average temperature 0.8 1C below the long-term [30 years] average) with high precipitation (175% above the long-term average). This had a favourable effect on the activity of I. ricinus, which did not decline in August (as it has been typical in other years), and it only gradually decreased thereafter in the warm autumn (September, October, and November average monthly temperatures 3.2, 2.8, and 3.2 1C above the long-term average, respectively). Also the recreational behaviour of people was influenced very much in the peak period of summer vacations and school vacations (TBE typically is a recreational infection in the Czech Republic). August weather resulted in a decline in water sports and directed the majority of holidaymakers to go on a mushroom foray, a traditional national hobby in the Czech Republic. This was also triggered by that year's very successful mushroom season, which was repeatedly highlighted by the media. This resulted in a second (late summer/autumn) peak of the incidence curve of TBE, which even exceeded the spring/summer culmination. Such a type of TBE seasonality had not been observed in the Czech Republic before, resulting in an exceptionally high overall annual incidence.