Incidence Of Tick-borne Encephalitis Research Articles

Influence of altitude on tick-borne encephalitis infection risk in the natural foci of the Altai Republic, Southern Siberia

The Altai Republic is a highly endemic area as far as tick-borne encephalitis (TBE) is concerned. The aim of the research was to study the effect of altitude on the risk of tick-borne encephalitis infection in the Altai Republic. The paper analyzes the following data: the study of ixodid ticks collected from the vegetation in 116 sites at the 200–2383m elevation above sea level in 2012–2014, TBE virus prevalence of these vectors, tick-bite incidence rate, and TBE incidence rate of the population.Species identification of 4503 specimens has shown that the most common species are Dermacentor nuttalli (45.3%), Ixodes persulcatus (33.1%), Dermacentor silvarum (9.4%), Dermacentor reticulatus (8.9%), and Haemaphysalis concinna (5.0%).A total of 2997 adult ixodid ticks were studied for the presence of the TBE virus; 2163 samples were examined by ELISA, while 834 specimens were tested by PCR. The TBE virus prevalence of Dermacentor spp. ticks in both reactions was significantly higher than of Ixodes persulcatus ticks (p<0.001).The work shows that the altitude is an important factor in the development of the epidemiological situation of tick-borne encephalitis: the higher the elevation of the area above sea level, the smaller the range of vectors. There is also a change of a leading species: in middle altitude (800–1700m above sea level) the virus is transmitted by ticks of D. nuttalli along with I. persulcatus, and in high mountains (above 1700m above sea level) D. nuttalli becomes an absolute dominant species. However, these species of ticks are less effective vectors than I. persulcatus. With the increase of altitude the tick-bite incidence rate decreases (r=−0.78, p<0.05), and TBE incidence also reduces (r=−0.67, p<0.05).

Increasing incidence of tick-borne encephalitis and its importance in the Slovak Republic.

Tick-borne encephalitis (TBE) is caused by tick-borne encephalitis virus (TBEV), a virus species of the genus Flavivirus within the Flaviviridae family. In Western Europe, TBEV is transmitted primarily by the Ixodes ricinus (I. ricinus) tick. During the last 30 years, there has been a continued increase in human cases of TBE in Europe. A total number of 102 cases in Slovakia was reported in 2012 (1.89/100,000), with two local outbreaks after the ingestion of raw milk and dairy products. Active vaccination is the most effective method of preventing TBE. According to the available data in Slovakia from 2012, 8,491 children under 15 years of age were vaccinated that year, which, when compared to 2009 with approximately 17,000 vaccinated children, represents a decrease of more than 50%. The data on vaccination of adults are not available, but the estimated vaccination coverage in Slovakia is around 1% (1.3/100,000). The education of the population is also an important precautionary measure in the prevention of tick-borne illnesses.

The Role of Game (Wild Boar and Roe Deer) in the Spread of Tick-Borne Encephalitis in the Czech Republic

In the Czech Republic, the incidence of human tick-borne encephalitis (TBE) has been increasing over the last two decades. At the same time, populations of game have also shown an upward trend. In this country, the ungulate game is the main host group of hosts for Ixodes ricinus female ticks. This study examined the potential contribution of two most widespread game species (roe deer [Capreolus capreolus] and wild boar [Sus scrofa]) to the high incidence of TBE in the Czech Republic, using the annual numbers of culls as a proxy for the game population. This was an ecological study, with annual figures for geographical areas-municipalities with extended competence (MEC)-used as units of analysis. Between 2003 and 2011, a total of 6213 TBE cases were reported, and 1062,308 roe deer and 989,222 wild boars were culled; the culls of roe deer did not demonstrate a clear temporal trend, but wild boar culls almost doubled (from 77,269 to 143,378 per year). Statistical analyses revealed a positive association between TBE incidence rate and the relative number of culled wild boars. In multivariate analyses, a change in the numbers of culled wild boars between the 25th and 75th percentile was associated with TBE incidence rate ratio of 1.23 (95% confidence interval 1.07-1.41, p=0.003). By contrast, the association of TBE with culled roe deer was not statistically significant (p=0.481). The results suggest that the size of the wild boar population may have contributed to the current high levels and the rising trend in incidence of TBE, whereas the regulated population of roe deer does not seem to be implicated in recent geographical or temporal variations in TBE in the Czech Republic.

The features of tick-borne encephalitis in the Yaroslavl region at the present stage. The problem of evolution of the infection

In the Yaroslavl region (Central Federal District of Russia), endemic of tick-borne encephalitis (TBE), the features of epidemiology of this infection were studied during 1992-2012. Cyclical fluctuations in the incidence of TBE, the lack of the trend to decrease of the incidence were observed, the average annual incidence was 1,6 ± 0,32 per 100 thousand ofpopulation. The prevalence offebrile forms of disease was 62,2%, meningeal forms - 16,3%, the total percentage offocal forms was 13,9%. Manifestations of evolution of TBE were: the increase of the epidemiological significance of anthropogenically transformed natural foci, anthropurgical foci of TBE, until 81% of TBE cases were unvaccinated citizens, the high lethality of 4% and the high frequency of cases of alimentary infection of TBE of 7,8% with lethality of 10,8%. The aethiological agent of 10 lethal cases was Siberian subtype of TBE virus.

ECOLOGICAL AND EPIDEMIOLOGICAL CHARACTERISTICS OF TICK-BORN ENCEPHALITIS AND TICK BORRELIOSIS (THE LIME DISEASE) IN KALININGRAD OBLAST

Abstract. Results of monitoring of tick-borne encephalitis (TBE) and tick borreliosis (TB) in the western enclave of Russia in Kaliningrad oblast in 1999-2008 are presented in the article. The number of basic vector of the agents of these infections — I. ricinus during the analyzing period in the territory of Kurshskaya spit increased. The number of tick attacked persons in the oblast also increased. Despite these events the TBE incidence rates remained not so high and have tendency to decrease. At the same time the TB morbidity has moderate trend to increase. The link between increase of average annual air temperature and incidence of "tick" infections was not proved for the studying period of time. The people of pre-pension and pension ages living in cities more often suffer from TBE and TB. The most part of patients are exposed to tick attack during visiting of rest places. It was determined that eastern districts of Kaliningrad oblast are more problematic on "tick" infections.

Tick-borne encephalitis transmission risk: its dependence on host population dynamics and climate effects.

Tick-borne encephalitis (TBE) is a human disease caused by a flavivirus that is spread by ticks (Ixodes ricinus). In 2011 and 2012, the highest TBE incidence ever was recorded in Sweden. It has been proposed that warmer spring temperatures result in higher survival of ticks and thus high incidence of TBE. Here, analyses were done of time series of TBE for 1976-2011 in relation to the North Atlantic Oscillation (NAO), mean summer temperatures, and yearly number of harvested European hare (Lepus europeaus), roe deer (Capreolus capreolus), and red fox (Vulpes vulpes) in the County of Stockholm, the area with most TBE cases in recent years in Sweden. The results show that the winter NAO index or winter temperature has no significant effect on the variation in wildlife numbers harvested or TBE cases over time. Mean summer temperature above 12°C had a slight effect, but a multivariate model revealed that only the numbers of European hare and red fox remained in the model and explained 64.4% of the variation in TBE cases. Ticks do not seem to be as sensitive to climate variations as anticipated, even though that summer temperature has increased by 2°C during the time period studied here. Instead, TBE cases seem to be more dependent on host population dynamics than on climate factors.

Tick-borne encephalitis virus habitats in North East Germany: reemergence of TBEV in ticks after 15 years of inactivity.

The incidence of tick-borne encephalitis has risen in Europe since 1990 and the tick-borne encephalitis virus (TBEV) has been documented to be spreading into regions where it was not previously endemic. In Mecklenburg-West Pomerania, a federal state in Northern Germany, TBEV was not detectable in over 16,000 collected ticks between 1992 and 2004. Until 2004, the last human case of TBE in the region was reported in 1985. Following the occurrence of three autochthonous human cases of TBE after 2004, however, we collected ticks from the areas in which the infections were contracted. To increase the chance of detecting TBEV-RNA, some of the ticks were fed on mice. Using nested RT-PCR, we were able to confirm the presence of TBEV in ticks for the first time after 15 years. A phylogenetic analysis revealed a close relationship between the sequences we obtained and a TBEV sequence from Mecklenburg-East Pomerania published in 1992 and pointed to the reemergence of a natural focus of TBEV after years of low activity. Our results imply that natural foci of TBEV may either persist at low levels of activity for years or reemerge through the agency of migrating birds.

Flavivirus genome detected in Mus and Apodemus species sampled in illegal waste sites

Tick-borne encephalitis virus (TBEV), a zoonotic flavivirus that occurs on the Eurasian continent and causes tick-borne encephalitis (TBE) in humans, is considered medically the most important arthropod vector transmitted virus in Europe. As such, TBEV is of course not a neglected pathogen. However, the knowledge about TBEV could importantly contribute to the research of other neglected vector borne pathogens. In nature, TBEV is transmitted from tick to tick via vertebrates in a process named co-feeding which is independent of a systemic viraemia in vertebrates. Therefore the ticks are the reservoirs as well as the vectors for TBEV, while the vertebrate is considered the transient bridge in transmission and maintenance of TBEV. Slovenia is an endemic country for TBEV with approximately 300 cases reported annually and incidence around 14 per 100,000 inhabitants. It was shown, that TBEV in Slovenia is maintained in tick-rodent-deer cycle. TBEV viraemic rodents of Myodes and Apodemus species were described previously in Slovenia. We were interested whether TBEV could be present in Mus species which share a living habitat with Apodemus mice in illegal waste sites. Thus we collected 83 samples of Mus and Apodemus species from different dump sites in Slovenia and Croatia. The presence of TBEV was determined using molecular techniques. Total RNA was extracted from spleen samples using RTP Pathogen Kit (Invitek-Stratec) and tested with real time RT-PCR specific for TBEV-Eur subtype. All samples were negative which could be explained by the fact that testing area was in the part of Slovenia with low incidence of TBE. However, distinctive samples were also tested with universal primers for amplification of flavivirus genome. Six amplicons of correct size were seen on agarose gel and are in the process of sequencing to reveal the identity of detected flavivirus.

Tick-borne Encephalitis Virus, Zealand, Denmark, 2011

Tick-borne Encephalitis Virus, Zealand, Denmark, 2011

Correlation of TBE Incidence with Red Deer and Roe Deer Abundance in Slovenia

Tick-borne encephalitis (TBE) is a virus infection which sometimes causes human disease. The TBE virus is found in ticks and certain vertebrate tick hosts in restricted endemic localities termed TBE foci. The formation of natural foci is a combination of several factors: the vectors, a suitable and numerous enough number of hosts and in a habitat with suitable vegetation and climate. The present study investigated the influence of deer on the incidence of tick-borne encephalitis. We were able to obtain data from deer culls. Using this data, the abundance of deer was estimated and temporal and spatial analysis was performed. The abundance of deer has increased in the past decades, as well as the incidence of tick-borne encephalitis. Temporal analysis confirmed a correlation between red deer abundance and tick-borne encephalitis occurrence. Additionally, spatial analysis established, that in areas with high incidence of tick-borne encephalitis red deer density is higher, compared to areas with no or few human cases of tick-borne encephalitis. However, such correlation could not be confirmed between roe deer density and the incidence of tick-borne encephalitis. This is presumably due to roe deer density being above a certain threshold so that availability of tick reproduction hosts has no apparent effect on ticks' host finding and consequently may not be possible to correlate with incidence of human TBE.

PIN7 Estimate of Infectious Disease Burden Attributable to Climate Change

To assess the incidence and distribution of infectious diseases which have been markedly affected by climate change. Literature searches were performed using Embase®, MEDLINE®, Google Scholar, and WHO website. Current evidence suggests that inter-annual and inter-decadal climate variability have a direct impact on the epidemiology of infectious diseases. According to WHO, since mid-1970s, climatic changes have caused annually over 150 000 deaths and an approximately 5 million disability-adjusted life-years, mainly in developing countries. Malaria has been considered as an extremely climate-sensitive disease. A temperature rise of 2°C-3°C increases the risk of malaria by 3%-5%. Across the world, the incidence cases of malaria increased from 233 000 in 2000 to 244 000 in 2005, with highest incidence observed in Africa. The West Nile virus (WNV) disease is considered as an emerging epidemic in the US. More than 7000 neuroinvasive WNV disease cases were reported in the US from 1999-2004. Parallel to rising temperatures, the US has recorded a 41% increase in vibrio infection rate from 1996-2006. In continental Europe, a temperature rise of 6°C above the mean resulted in an estimated 30% reported cases of salmonellosis. In Russia, rising temperatures from 2001 have increased the incidence of tick-borne encephalitis (TBE) by 10-fold within a decade. Korea's climatic variability has also been positively correlated with the incidence cases of malaria, Vibrio vulnificus sepsis, scrub typhus, leptospirosis, and Hantavirus infection during 2001-2008. Further, in 2009-2010, government officials of Europe have predicted that borreliosis, WNV fever, TBE, and salmonellosis are likely to be majorly affected by climate change. Accelerating climate change carries a profound threat for the increased burden of infectious diseases worldwide. To attain the maximum disease prevention, an understanding of the ecology of infectious diseases must be developed in order to protect vulnerable populations, rather than focussing on single agent of disease.

Epidemiology of Tick-Borne Encephalitis in the Czech Republic 1970–2008

This article presents major epidemiologic features of tick-borne encephalitis (TBE) in the Czech Republic, using data of laboratory-confirmed cases since 1970. A total of 17,053 cases of TBE were reported in the Czech Republic (population 10 million) in 1970-2008. The data show several important features. First, the pattern of TBE incidence changed over time. Until the end of the 1970s, TBE was characterized by periods of alternately higher and lower incidence (between 180 and 595 cases per year); the 1980s were a period of low incidence with minimum variability; since the beginning of the 1990 s, there has been a steep rise in incidence, with marked year-to-year variation (e.g., 745 cases were registered in 1995, and a maximum of 1029 cases were registered in 2006). Second, the age distribution of TBE incidence has changed. Until the end of 1990 s, incidence peaked among those 15-19 years of age, with a gradual decline with age. In the 2000s, however, TBE incidence has been rising in those aged 60-64 years, with a sharp decline in those older than 65 years. Third, the seasonal pattern of TBE has changed markedly over time. In the earlier period, incidence had a clear peak in July/August; since the 1990 s, more cases have occurred in earlier and later months of the year. The proportion of cases occurring in April, May, October, and November increased from 9% in the 1970s to 23% in 2000-2008. Fourth, the geographical distribution of TBE also changed over time, with TBE increasingly occurring in the mountainous districts at higher altitudes. These changes in incidence patterns appear to be linked with changes in climatic and meteorological conditions. The link between climate change and TBE incidence is plausible, since TBE is a recreation-related infection associated with outdoor activities, and since climatic changes affect the life cycle of the vector.

Why is tick-borne encephalitis increasing? A review of the key factors causing the increasing incidence of human TBE in Sweden

The highest annual incidence of human tick-borne encephalitis (TBE) in Sweden ever recorded by the Swedish Institute for Communicable Disease Control (SMI) occurred last year, 2011. The number of TBE cases recorded during 2012 up to 6th August 2012 indicates that the incidence for 2012 could exceed that of 2011. In this review of the ecology and epidemiology of TBE in Sweden our main aim is to analyse the possible reasons behind the gradually increasing incidence of human TBE during the last 20 years. The main TBE virus (TBEV) vector to humans in Sweden is the nymphal stage of the common tick Ixodes ricinus. The main mode of transmission and maintenance of TBEV in the tick population is considered to be when infective nymphs co-feed with uninfected but infectible larvae on rodents. In most locations the roe deer, Capreolus capreolus is the main host for the reproducing adult I. ricinus ticks. The high number of roe deer for more than three decades has resulted in a very large tick population. Deer numbers have, however, gradually declined from the early 1990s to the present. This decline in roe deer numbers most likely made the populations of small rodents, which are reservoir-competent for TBEV, gradually more important as hosts for the immature ticks. Consequently, the abundance of TBEV-infected ticks has increased. Two harsh winters in 2009–2011 caused a more abrupt decline in roe deer numbers. This likely forced a substantial proportion of the “host-seeking” ticks to feed on bank voles (Myodes glareolus), which at that time suddenly had become very numerous, rather than on roe deer. Thus, the bank vole population peak in 2010 most likely caused many tick larvae to feed on reservoir-competent rodents. This presumably resulted in increased transmission of TBEV among ticks and therefore increased the density of infected ticks the following year. The unusually warm, humid weather and the prolonged vegetation period in 2011 permitted nymphs and adult ticks to quest for hosts nearly all days of that year. These weather conditions stimulated many people to spend time outdoors in areas where they were at risk of being attacked by infective nymphs. This resulted in at least 284 human cases of overt TBE. The tick season of 2012 also started early with an exceptionally warm March. The abundance of TBEV-infective “hungry” ticks was presumably still relatively high. Precipitation during June and July was rich and will lead to a “good mushroom season”. These factors together are likely to result in a TBE incidence of 2012 similar to or higher than that of 2011.

Tick-Borne Encephalitis in Slovenia: Data from a Questionnaire Survey

There has been a marked increase in the incidence of tick-borne encephalitis (TBE) in the last two decades, with new foci of the disease evolving. TBE is endemic in Slovenia, and the incidence rate is one of the highest in the European Union. A survey of notified TBE cases started in 1999, aiming to collect additional epidemiological data that are not available through the usual notification system. From 1999 to 2009, a short, anonymous, self-administered questionnaire was sent to 2779 notified TBE cases. The response rate was 69.5%. The willingness to respond was higher in those over 60 years of age, but did not differ by gender. In all, 1564 (82.3%) of the responders had a tick bite on one or multiple sites on the body. Age and gender influenced the location of the tick bite: males patients most often had the tick located on the torso, and females had them on the legs. Ticks located on the head and neck were significantly higher in preschool children compared to school children and adults. The estimated duration of tick attachment was less than 6 h in 23.5% of TBE cases. Long attachments (more than 24 h) were reported by only 10% of the patients. The tick bite occurred while the TBE patients were engaged in leisure time activities (sports or camping, 32.8%), mushroom or berry picking (30.2%), or farming (23.3%). Almost two-thirds of TBE patients reported that they had practiced at least one of the recommended preventive measures, most frequently self-inspection, and least often repellent use. The patients were asked to disclose the most probable geographical location of the TBE viral (TBEV) infection. Maps were created on a county level and showed that the risk of TBE is widespread, with few counties unaffected. The counties located in the northern and the central areas had the highest risk of TBEV infection.

The impact of climate change on the expansion of Ixodes persulcatus habitat and the incidence of tick-borne encephalitis in the north of European Russia

BackgroundThe increase in tick-borne encephalitis (TBE) incidence is observed in recent decades in a number of subarctic countries. The reasons of it are widely discussed in scientific publications. The objective of this study was to understand if the climate change in Arkhangelsk Oblast (AO) situated in the north of European subarctic zone of Russia has real impact on the northward expansion of Ixodid ticks and stipulates the increase in TBE incidence.MethodsThis study analyzes: TBE incidence in AO and throughout Russia, the results of Ixodid ticks collecting in a number of sites in AO, and TBE virus prevalence in those ticks, the data on tick bite incidence in AO, and meteorological data on AO mean annual air temperatures and precipitations.ResultsIt is established that in recent years TBE incidence in AO tended to increase contrary to its apparent decrease nationwide. In last 10 years, there was nearly 50-fold rise in TBE incidence in AO when compared with 1980–1989. Probably, the increase both in mean annual air temperatures and temperatures during tick active season resulted in the northward expansion of Ixodes Persulcatus, main TBE virus vector. The Ixodid ticks expansion is confirmed both by the results of ticks flagging from the surface vegetation and by the tick bite incidence in the population of AO locations earlier free from ticks. Our mathematical (correlation and regression) analysis of available data revealed a distinct correlation between TBE incidence and the growth of mean annual air temperatures in AO in 1990–2009.ConclusionNot ruling out other factors, we conclude that climate change contributed much to the TBE incidence increase in AO.

High burden of tick-borne encephalitis in Slovenia—Challenge for vaccination policy

Slovenia is one of the countries with the highest reported incidence rates of tick-borne encephalitis (TBE). Vaccination uptake is low, estimated to be 12.4%. TBE surveillance data for the last 20 years were analysed. Though nearly all of Slovenia is endemic for TBE with national yearly incidence rates up to 26.7/100,000, we showed that two regions (Gorenjska and Koroška) were much more affected than other seven regions, with annual incidence rates up to 57.2/100,000 and 76.9/100,000 population, respectively. In the last decade, there was a shift in the age distribution of reported TBE cases to the older age groups, which resulted in the highest age-specific incidence rates nationally in 55–64 age group (up to 33.4/100,000 in 2006). To reduce this high burden of TBE, ideally the whole population of Slovenia should be offered free of charge vaccination against TBE. Alternatively, in view of limited resources available, sensible approach would be increasing vaccination coverage of the general population using social marketing and increasing TBE awareness, and in addition, offering free of charge vaccination to the most affected groups. The following priority target groups should be considered to be prospectively covered with free of charge vaccination: (1) 45–69 years old individuals in the two most affected regions (Gorenjska, Koroška), (2) the remaining age groups in the two most affected regions, (3) 45–69 years old individuals in the region with the next highest TBE incidence rates (Ljubljana), and (4) individuals 45–69 years old in all remaining Slovenian regions.

Tick‐borne encephalitis in Latvia 1973–2009: epidemiology, clinical features and sequelae

To report a 37-year observational experience in Latvia relating the incidence of human tick-borne encephalitis (TBE) and its clinical manifestations, to the field abundance of ticks. Tick abundance was measured by standard flagging techniques. Incidence of human tick-borne disease was derived from Public Health reporting data. Clinical and follow-up data were determined from hospital cohorts from 1973 to 2009. Two TBE incidence peaks in the mid-1970s and the 1990s correlated with increased field abundance of ticks. Increased human TBE in the 1970s was associated with higher field abundance of both Ixodes ricinis and I. Persulcatus. The 1990s peak was particularly associated with I. ricinus, the species predominating in western/central Latvia, and with other factors, including changed agricultural land usage. Proportions of patients with meningitic or focal forms of TBE were similar in the two outbreaks and the intervening periods. Meningeal irritation occurred in 90%, altered consciousness in 19%, ataxia in 34%, seizures in 9%, bulbar features in 2-3% and limb weakness in 15% with shoulder amyotrophy predominating in 5%. Annual mortality varied from 0 to 1.3% and was not related to the overall incidence of TBE. Follow-up for 1-13 years of a cohort of 100 patients revealed long-term sequelae in over 50%, more commonly in those suffering focal forms of acute TBE. Clinical features and mortality of the 1970s and 1990s TBE outbreaks were similar and did not point to a change in virulence.

Economic downturn results in tick-borne disease upsurge.

BackgroundThe emergence of zoonoses is due both to changes in human activities and to changes in their natural wildlife cycles. One of the most significant vector-borne zoonoses in Europe, tick-borne encephalitis (TBE), doubled in incidence in 1993, largely as a consequence of the socio-economic transition from communism to capitalism and associated environmental changes.MethodsTo test the effect of the current economic recession, unemployment in 2009 and various socio-economic indices were compared to weather indices (derived from principal component analyses) as predictors for the change in TBE case numbers in 2009 relative to 2004-08, for 14 European countries.ResultsGreatest increases in TBE incidence occurred in Latvia, Lithuania and Poland (91, 79 and 45%, respectively). The weather was rejected as an explanatory variable. Indicators of high background levels of poverty, e.g. percent of household expenditure on food, were significant predictors. The increase in unemployment in 2009 relative to 2008 together with 'in-work risk of poverty' is the only case in which a multivariate model has a second significant term.ConclusionBackground socio-economic conditions determine susceptibility to risk of TBE, while increased unemployment triggered a sudden increase in risk. Mechanisms behind this result may include reduced resistance to infection through stress; reduced uptake of costly vaccination; and more exposure of people to infected ticks in their forest habitat as they make greater use of wild forest foods, especially in those countries, Lithuania and Poland, with major marketing opportunities in such products. Recognition of these risk factors could allow more effective protection through education and a vaccination programme targeted at the economically most vulnerable.

Forecasting risk of tick-borne encephalitis (TBE): Using data from wildlife and climate to predict next year's number of human victims

Over the past quarter century, the incidence of tick-borne encephalitis (TBE) has increased in most European nations. However, the number of humans stricken by the disease varies from year to year. A method for predicting major increases and decreases is needed. We assembled a 25-y database (1984-2008) of the number of human TBE victims and wildlife and climate data for the Stockholm region of Sweden, and used it to create easy-to-use mathematical models that predict increases and decreases in the number of humans stricken by TBE. Our best model, which uses December precipitation and mink (Neovison vison, formerly Mustela vison) bagging figures, successfully predicted every major increase or decrease in TBE during the past quarter century, with a minimum of false alarms. However, this model was not efficient in predicting small increases and decreases. Predictions from our models can be used to determine when preventive and adaptive programmes should be implemented. For example, in years when the frequency of TBE in humans is predicted to be high, vector control could be intensified where infested ticks have a higher probability of encountering humans, such as at playgrounds, bathing lakes, barbecue areas and camping facilities. Because our models use only wildlife and climate data, they can be used even when the human population is vaccinated. Another advantage is that because our models employ data from previously-established databases, no additional funding for surveillance is required.

Spatio-temporal variation of tick-borne encephalitis (TBE) incidence in the Czech Republic: Is the current explanation of the disease's rise satisfactory?

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 socio-economic 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 socio-economic conditions.