Tick-borne Encephalitis Risk Areas Research Articles

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

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

Surveillance of tick-borne encephalitis in emerging risk areas in southern Sweden: a retrospective case finding study

Tick-borne encephalitis (TBE) is an emerging infection causing CNS infection of various severity. Good knowledge of the incidence in the population and defined risk areas is important in risk communication and vaccination recommendations. The aim of this study was to investigate potential underreporting by retrospectively diagnose TBE among patients with viral CNS infections of unknown etiology in a region with emerging risk areas for TBE, and define variables associated with performed TBE serology at the time of infection. Epidemiological data and microbiological diagnostics of cases with viral CNS infection of unknown etiology treated at departments of infectious diseases and pediatrics in Skåne County during 2000–2012 were investigated. Analyses to evaluate variables associated with performed TBE serology at the time of infection were performed. Retrospective TBE serology was performed on stored blood samples when available. TBE serology was already performed at the time of CNS infection in 193 out of 761 cases. Department, type of clinical manifestation, time period of illness, and whether Borrelia serology had been performed were independent variables associated with having had TBE serology performed or not at the time of illness. Only one of 137 cases, where samples could be retrospectively analyzed for TBE, turned out positive. This study shows a low frequency of TBE sampling among patients with meningoencephalitis in a region with emerging risk for TBE. A higher awareness of TBE as differential diagnosis could contribute to earlier detection of new risk areas and adequate preventive advice to the public.

A Serosurvey of Tick-Borne Encephalitis Virus in Sweden: Different Populations and Geographical Locations.

Background: New risk areas for tick-borne encephalitis (TBE) are emerging and the spread of disease and vaccine coverage is unclear in Sweden. We wanted to study the prevalence and levels of TBE-virus (TBEV) antibodies in southern Sweden, and to investigate whether there were individuals with undiagnosed TBE. Materials and Methods: Two cohorts of sera were collected: One group of anonymous individuals in rural areas (AIRA) in Skåne and one group of volunteers who often got tick-bites (tick-bitten individuals [TBI]). An enzyme-linked immunosorbent assay for TBEV IgM and IgG was performed, as well as a TBEV neutralization test (NT) in selected individuals. Results: In the AIRA group, there was an IgG seropositivity of 5.3%. There were individuals with high antibody levels both in areas previously considered as risk areas (Bromölla and Knislinge), as well as in another area (Tyringe). In the TBI group, 45% of the individuals were vaccinated according to the questionnaires and IgG seropositivity was 28%. A lower seroprevalence and levels of antibodies were seen in the middle-aged group (50-69 years) compared with younger or elderly study participants. A positive NT revealed several individuals with suspected undiagnosed episodes of TBE. Conclusion: Subclinical or misdiagnosed cases have probably occurred in Skåne. Middle-aged individuals had lower levels of IgG, which could indicate either less tick exposure or a lower vaccine response. Less than half of the TBI were vaccinated, an indication that more information about the disease and vaccine might be needed. We conclude that the study motivates an increased awareness of TBEV in the region.

Mapping geographical areas at risk for tick-borne encephalitis (TBE) by analysing bulk tank milk from Swedish dairy cattle herds for the presence of TBE virus\u2013specific antibodies

BackgroundThe vector-borne human viral zoonosis tick-borne encephalitis (TBE) is of growing concern in Sweden. The area where TBE is considered endemic has expanded, with an increasing geographical distribution of Ixodes ricinus as the tick vector and a rising number of reported TBE cases in humans. Efforts to map TBE risk areas have been carried out by sentinel monitoring, mainly based on individual sampling and analysis of wild and domestic animals, as well as ticks, for tick-borne encephalitis virus (TBEV). However, the interpretation of the geographical distribution has been hampered by the patchy and focal nature of TBEV occurrence. This study presents TBEV surveillance data based on antibody analysis of bulk tank milk collected from dairy herds located throughout Sweden before (May) and after (November) the vector season. A commercial TBEV antibody ELISA was modified and evaluated for use in this study.ResultsThe initial comparative TBEV antibody analysis revealed a good correlation between milk and serum antibody levels from individually sampled cows. Also, the TBEV-antibody levels for the mean-herd serum showed good comparability with TBEV antibody levels from bulk tank milk, thus indicating good predictability of seroprevalence when analysing bulk tank milk from a herd.Analyses of bulk tank milk samples collected from 616 herds in May and 560 herds in November showed a geographical distribution of TBEV seropositive herds that was largely consistent with reported human TBE cases. A few TBEV-reactive herds were also found outside known locations of human TBE cases.ConclusionSerological examination of bulk tank milk from dairy cattle herds may be a useful sentinel surveillance method to identify geographical presence of TBEV. In contrast to individual sampling this method allows a large number of animals to be monitored. TBEV seropositive herds were mainly found in coastal areas of southern Sweden similar to human TBE cases. However, some antibody-reactive herds were found outside known TBE areas at the time of the study.

Low prevalence of tick-borne encephalitis virus antibodies in Norwegian blood donors

Background Tick-borne encephalitis (TBE) constitutes a public health concern in Europe. Certain coastal municipalities in southern Norway are considered TBE risk areas and in the last two years, there have been increasing numbers of TBE cases. Since the majority of infections are claimed to be asymptomatic, the aim of the current study was to assess the seroprevalence of antibodies to tick-borne encephalitis virus (TBEV) among unvaccinated adults living in a TBE endemic area in Norway. Methods One thousand one hundred and twenty-three blood donors living in Vestfold and Telemark county were included and associated sera were analysed for TBEV IgG antibodies. Information regarding tick bites, previous flavivirus exposure and knowledge regarding TBE and TBE prevention were obtained through a questionnaire. Results Fifty-eight samples were reactive by ELISA, of which 21 (36.2%) were confirmed by a TBEV-specific serum neutralization test. Of the 21 blood donors with neutralizing TBEV antibodies detected, 17 reported previous TBE vaccination. Thus, only four blood donors (0.4%) had TBEV neutralizing antibodies consistent with previously undergone TBEV infection. Regarding TBE awareness, half of the blood donors were familiar with TBE, but only 35% were aware of a preventive TBE vaccine. Conclusions Our study indicates low prevalence of subclinical TBEV infections among blood donors living in Vestfold and Telemark county and there is a lack of awareness among general public.

Tick-Borne Encephalitis Virus and Its European Distribution in Ticks and Endothermic Mammals.

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.

TBE in Belarus

Almost the entire territory of Belarus is believed to be endemic for tick-borne encephalitis virus (TBEV), with the Central European subtype, also known as TBEV-EU (Figure 1). In all, 96 counties (i.e., 71.5% of all administrative districts) are considered to be risk areas for tick-borne encephalitis (TBE). The most intensive natural foci have been found in the western part of the country (Brest and Grodno Area), and infections in these areas account for an average of 40% each of the total number of reported cases

Revealing new tick-borne encephalitis virus foci by screening antibodies in sheep milk

BackgroundTick distribution in Sweden has increased in recent years, with the prevalence of ticks predicted to spread towards the northern parts of the country, thus increasing the risk of tick-borne zoonoses in new regions. Tick-borne encephalitis (TBE) is the most significant viral tick-borne zoonotic disease in Europe. The disease is caused by TBE virus (TBEV) infection which often leads to severe encephalitis and myelitis in humans. TBEV is usually transmitted to humans via tick bites; however, the virus can also be excreted in the milk of goats, sheep and cattle and infection may then occur via consumption of unpasteurised dairy products. Virus prevalence in questing ticks is an unreliable indicator of TBE infection risk as viral RNA is rarely detected even in large sample sizes collected at TBE-endemic areas. Hence, there is a need for robust surveillance techniques to identify emerging TBEV risk areas at early stages.MethodsMilk and colostrum samples were collected from sheep and goats in Örebro County, Sweden. The milk samples were analysed for the presence of TBEV antibodies by ELISA and validated by western blot in which milk samples were used to detect over-expressed TBEV E-protein in crude cell extracts. Neutralising titers were determined by focus reduction neutralisation test (FRNT). The stability of TBEV in milk and colostrum was studied at different temperatures.ResultsIn this study we have developed a novel strategy to identify new TBEV foci. By monitoring TBEV antibodies in milk, we have identified three previously unknown foci in Örebro County which also overlap with areas of TBE infection reported during 2009–2018. In addition, our data indicates that keeping unpasteurised milk at 4 °C will preserve the infectivity of TBEV for several days.ConclusionsAltogether, we report a non-invasive surveillance technique for revealing risk areas for TBE in Sweden, by detecting TBEV antibodies in sheep milk. This approach is robust and reliable and can accordingly be used to map TBEV “hotspots”. TBEV infectivity in refrigerated milk was preserved, emphasising the importance of pasteurisation (i.e. 72 °C for 15 s) prior to consumption.

Tick burden on European roe deer (Capreolus capreolus) from Saxony, Germany, and detection of tick-borne encephalitis virus in attached ticks.

Southern Germany is known as tick-borne encephalitis (TBE) risk area; however, the north of the country is almost free of human TBE cases. Due to its location in the transition zone between TBE risk areas and areas with only sporadic cases, Saxony is of importance in the surveillance of TBE. Roe deer (Capreolus capreolus), showing high seroprevalence of TBE virus (TBEV) antibodies, are considered to be sentinels for TBE risk assessment. Thus, roe deer could be used as indicators helping to better understand the focality of the TBEV in nature and as a possible source to isolate TBEV. Therefore, the aims of this study were to examine roe deer coats for the presence of ticks to establish the tick burden and to detect the TBEV in attached ticks. One hundred thirty-four roe deer coats were provided by hunters from the Hunting Association in Saxony (August 2017-January 2019). The coats were frozen at - 80°C and after de-freezing examined on both sides-inside and outside. Attached and nonattached ticks were collected, morphologically identified and tested using real-time RT-PCR for the presence of TBEV. In total, 1279 ticks were found on 48 coats. The predominant species was Ixodes ricinus (99.76%; n = 1276). Three remaining specimens were Ixodes spp. (0.16%, 1 female and 1 nymph) and Dermacentor reticulatus (0.08%, 1 male). The average infestation rate was 26.7 (SD = 69.5), with maximum of 439 ticks per animal. Females were the dominant life stage of ticks (n = 536; 42%), followed by nymphs (n = 397; n = 31.1%), males (n = 175; 13.7%), and larvae (n = 168; 13.2%). Only half of collected ticks were attached (n = 662; 51.8%). TBEV was detected only in one tick out of 1279 tested ticks. It was a female infesting a roe deer from Saxon Switzerland-East Ore Mountain. The results show that the method used in this study is not sufficient as a sentinel marker to predict TBEV spreading in nature. Although previous studies demonstrated the usefulness of serological testing of roe deer in order to trace TBE-endemic regions, using ticks attached to them to get virus isolates is not productive.

TBE in Belarus

Almost the entire territory of Belarus is believed to be endemic for tick-borne encephalitis virus (TBEV), with the Central European subtype, also known as TBEV-EU (Figure 1). In all, 96 counties (i.e., 71.5% of all administrative districts) are considered to be risk areas for tick-borne encephalitis (TBE).

Continued expansion of tick-borne pathogens: Tick-borne encephalitis virus complex and Anaplasma phagocytophilum in Denmark

Tick-borne encephalitis virus (TBEV) is a tick-transmitted flavivirus within the tick-borne encephalitis (TBE) complex. The TBE complex is represented by both TBEV and louping ill virus (LIV) in Denmark. Anaplasma phagocytophilum is also transmitted by ticks and is believed to play an essential role in facilitating and aggravating LIV infection in sheep.This study aimed to describe the distribution of TBE complex viruses in Denmark, to establish the possible emergence of new foci and their association with the distribution of A. phagocytophilum. We performed a nationwide seroprevalence study of TBE complex viruses using roe deer (Capreolus capreolus) as sentinels and determined the prevalence of A. phagocytophilum in roe deer. Danish hunters obtained blood samples from roe deer during the hunting season of 2013-14. The samples were examined for TBEV-specific antibodies by virus neutralization tests (NT). A. phagocytophilum infection was assessed by specific real-time-PCR.The overall seroprevalence of the TBE complex viruses in roe deer was 6.9% (51/736). The positive samples were primarily obtained from a known TBE endemic foci and risk areas identified in previous sentinel studies. However, new TBE complex risk areas were also identified. The overall prevalence of A. phagocytophilum was 94.0% (173 PCR-positive of 184 roe deer), which is twice the rate observed ten years ago.These results point to an expansion of these tick-borne diseases geographically and within reservoir populations and, therefore, rationalize the use of sentinel models to monitor changes in transmission of tick-borne diseases and development of new risk areas. We found no association between TBE complex-positive roe deer and the prevalence of A. phagocytophilum, as almost all roe deer were infected. Based on our findings we encourage health care providers to be attentive to tick-borne illnesses such as TBE when treating patients with compatible symptoms.

The Willingness to Pay for Vaccination against Tick-Borne Encephalitis and Implications for Public Health Policy: Evidence from Sweden.

The increasing incidence of tick-borne encephalitis (TBE) in Sweden and several other European countries has sparked a discussion about the need for a public vaccination strategy. However, TBE vaccination coverage is incomplete and there is little knowledge about the factors influencing vaccination behavior. Based on a survey of 1,500 randomly selected respondents in Sweden, we estimate vaccination coverage in areas with different TBE risk levels and analyze the role of vaccine price and other factors influencing the demand for vaccination. First, we find that the average rate of TBE vaccination in Sweden is 33% in TBE risk areas and 18% elsewhere. Income, age and risk-related factors such as incidence of TBE in the area of residence, frequency of visits to areas with TBE risk, and experience with tick bites are positively associated with demand for TBE vaccine. Next, using contingent valuation methodology, we estimate the willingness to pay for TBE vaccination among the unvaccinated respondents and the effect of a possible subsidy. Among the unvaccinated respondents in TBE risk areas, we estimate the mean willingness to pay for the recommended three doses of TBE vaccine to be 465 SEK (approximately 46 euros or 40% of the current market price). We project that a subsidy making TBE vaccines free of charge could increase the vaccination rate in TBE risk areas to around 78%, with a larger effect on low-income households, whose current vaccination rate is only 15% in risk areas. However, price is not the only factor affecting demand. We find significant effects on vaccination behavior associated with trust in vaccine recommendations, perceptions about tick bite-related health risks and knowledge about ticks and tick-borne diseases. Hence, increasing knowledge and trust, as well as ease of access to vaccinations, can also be important measures for public health agencies that want to increase the vaccination rate.

Surveillance of endemic foci of tick-borne encephalitis in Finland 1995-2013: evidence of emergence of new foci.

The geographical risk areas for tick-borne encephalitis (TBE) in Finland remained the same until the beginning of the 21st century, but a considerable geographical expansion has been observed in the past 10 years. In order to support public health measures, the present study describes the number of laboratory-confirmed TBE cases and laboratory tests conducted and the associated trends by hospital district, with a particular emphasis on the suspected geographical risk areas. An additional investigation was conducted on 1,957 clinical serum samples throughout the country taken from patients with neurological symptoms to screen for undiagnosed TBE cases. This study identified new TBE foci in Finland, reflecting the spread of the disease into new areas. Even in the most endemic municipalities, transmission of TBE to humans occurred in very specific and often small foci. The number of antibody tests for TBE virus more than doubled (an increase by 105%) between 2007 and 2013. Analysis of the number of tests also revealed areas in which the awareness of clinicians may be suboptimal at present. However, it appears that underdiagnosis of neuroinvasive TBE is not common.

Review: Sentinels of tick-borne encephalitis risk

Tick-borne encephalitis (TBE) is a viral zoonotic disease endemic in many regions of Eurasia. The definition of TBE risk areas is complicated by the focal nature of the TBE virus transmission. Furthermore, vaccination may reduce case numbers and thus mask infection risk to unvaccinated persons. Therefore, additional risk indicators are sought to complement the current risk assessment solely based on human incidence. We reviewed studies published over the past ten years investigating potential new sentinels of TBE risk to understand the advantages and disadvantages of the various sentinel animal surveys and surrogate indicator methods. Virus prevalence in questing ticks is an unsuitable indicator of TBE infection risk as viral RNA is rarely detected even in large sample sizes collected at known TBE endemic areas. Seroprevalence in domestic animals, on the other hand, showed good spatial correlation with TBE incidence in humans and might also uncover presently unknown TBEV foci.

Prevalences of tick-borne encephalitis virus and Borrelia burgdorferi sensu lato in Ixodes ricinus populations of the Rhine-Main region, Germany

Tick-borne encephalitis (TBE) and Lyme borreliosis are the most common tick-borne zooanthroponoses in Germany. The federal risk map for TBE in this country is based on recorded cases of human infection, whereas information on the vector-based prevalence of either pathogen is fragmentary. In this study, a total of 12,497 host-seeking nymphal and adult Ixodes ricinus ticks (Acari: Ixodidae) were collected from March to October 2009 and April to June 2010, in 5 TBE non-risk and 4 TBE risk areas of the Rhine-Main region (Hesse) via flagging. A total of 3615 ticks was examined for infection with Borrelia burgdorferi sensu lato and 9115 ticks were analyzed for TBE virus (TBEV). Pathogens were detected by real-time polymerase chain reaction. Among 3615 questing ticks, 344 (9.5%) were found infected with B. burgdorferi sensu lato. Five Borrelia genospecies were identified by sequencing the OspA gene: B. afzelii (81.3%), B. garinii (14.0%), B. valaisiana (2.7%), B. spielmanii (1.3%), and B. bavariensis (0.7%). TBE infection of ticks differed between areas classified as TBE risk and TBE non-risk areas. While the prevalence of TBEV was between 0 and 0.2% (3 of 3947 ticks) in the TBE risk areas, no TBEV-infected tick was detected from TBE non-risk areas. The results show that B. burgdorferi sensu lato occurred in all 9 examined locations, indicating that Lyme borreliosis is prevalent in the Rhine-Main region, whereas TBEV was detected only in previously classified risk areas.

Tick-borne encephalitis 2010: Epidemiology, risk areas, and virus strains in Europe and Asia—An overview

Over the past decades, tick-borne encephalitis (TBE) has become a growing public health concern in Europe and Asia and is the most important viral tick-borne disease in Europe. It is also important in the Far East and in other parts of Asia. Vaccination can effectively prevent TBE. It is indicated for persons inhabiting or visiting a TBE endemic area who are likely to be exposed to tick bites. For this purpose, it is necessary to know where TBE virus (TBEV) occurs, where vectors are a potential hazard, and where as a consequence autochthonous TBE cases have been registered. Natural changes in the known TBE foci and the detection of new foci necessitate a summarizing data update to optimize the protection of inhabitants and visitors to TBE endemic areas. The present review includes an overview of the epidemiological data on TBE in Europe and Asia gathered between 1990 and 2009 and describes old and especially new TBE risk areas in Europe and Asia.

Factors affecting patterns of tick parasitism on forest rodents in tick-borne encephalitis risk areas, Germany

Identifying factors affecting individual vector burdens is essential for understanding infectious disease systems. Drawing upon data of a rodent monitoring programme conducted in nine different forest patches in southern Hesse, Germany, we developed models which predict tick (Ixodes spp. and Dermacentor spp.) burdens on two rodent species Apodemus flavicollis and Myodes glareolus. Models for the two rodent species were broadly similar but differed in some aspects. Patterns of Ixodes spp. burdens were influenced by extrinsic factors such as season, unexplained spatial variation (both species), relative humidity and vegetation cover (A. flavicollis). We found support for the ‘body mass’ (tick burdens increase with body mass/age) and for the ‘dilution’ hypothesis (tick burdens decline with increasing rodent densities) and little support for the ‘sex-bias’ hypothesis (both species). Surprisingly, roe deer densities were not correlated with larvae counts on rodents. Factors influencing the mean burden did not significantly explain the observed dispersion of tick counts. Co-feeding aggregations, which are essential for tick-borne disease transmission, were mainly found in A. flavicollis of high body mass trapped in areas with fast increase in spring temperatures. Locally, Dermacentor spp. appears to be an important parasite on A. flavicollis and M. glareolus. Dermacentor spp. was rather confined to areas with higher average temperatures during the vegetation period. Nymphs of Dermacentor spp. mainly fed on M. glareolus and were seldom found on A. flavicollis. Whereas Ixodes spp. is the dominant tick genus in woodlands of our study area, the distribution and epidemiological role of Dermacentor spp. should be monitored closely.

TBE incidence versus virus prevalence and increased prevalence of the TBE virus in Ixodes ricinus removed from humans

Traditionally, the classification of risk areas of tick-borne encephalitis (TBE) is based on the recording of autochthonous cases of the disease. In Germany, an extension of these areas over the years and an increasing virus prevalence in ticks have been observed in recent years. Registration of foci with autochthonous TBE cases, recording of disease incidence and virus prevalence in ticks are all proven epidemiological methods to characterize TBE risk areas. These data are necessary for a scientifically proven recommendation of TBE vaccines, and they need to be updated regularly. These epidemiological methods have advantages and disadvantages with respect to the risk assessment of TBE areas. Despite the fact that these methods are suitable for risk assessment in practice, disease incidence (new cases per year/100,000 inhabitants) and virus prevalence in questing ticks did not correlate. Using nested RT-PCR we were able to demonstrate that the prevalence of TBE virus (TBEV) in ticks removed from humans was significantly higher than in unfed, free-living Ixodes ricinus of the same area. The 561 ticks collected from humans in doctors’ surgeries in Bavaria in 2002 were examined by nRT-PCR. The estimated overall virus prevalence in tested ticks was 8.8% (95% CI: 6.45–11.57%). The removed ticks examined were classified according to the sites of exposure of the patients in the individual districts. Peak values were measured in the district of Regen with 20.6% and in the district of Freyung-Grafenau with 18.3%. In recent studies on unfed I. ricinus (nymphs, adults), the average TBEV prevalence in ticks in Bavarian risk areas was between 0.5% and 2%.

Tick-borne encephalitis (TBE) in Germany--epidemiological data, development of risk areas and virus prevalence in field-collected ticks and in ticks removed from humans.

In Germany, 100-300 autochthonous clinical TBE cases have been recorded annually. There are high-risk areas in Bavaria and Baden-Wuerttemberg and ongoing low-risk areas in Hesse, Thuringia, and the Rhineland-Palatinate and single cases in Saxony. In order to be able to evaluate the epidemiological changes described here, it must be mentioned that a new definition of TBE risk areas was introduced on the district level in 1998 in Germany and in 2001 with the new Infection Protection Act (Infektionsschutzgesetz) which states that TBE is a notifiable disease. This led to the replacement of earlier surveillance systems and to many changes to data collection. In 1998 63 country and town districts were TBE risk areas, in 2001 79 and in 2002 86. There were new risk districts within Bavaria and Baden-Wuerttemberg and outside these regions in Thuringia, Hesse and the Rhineland-Palatinate. An interesting trend was observed in TBE epidemiology. The TBE incidence in Bavaria and Baden-Wuerttemberg has been stable on a high level for years; outside these areas it has steadily been climbing (Odenwald, Thuringia). On the basis of epidemiological data on TBE from the eastern part of Germany since 1960, it is obvious that major changes in virus activity in TBE risk areas also occurred in the past, the explanation of which has remained a matter for speculation. The epidemiological situation in the different risk areas for TBE in Germany was found to vary considerably, if one considers the surveillance data of the last 40 years. 1. Establishment of completely new low-risk areas. 2. Reactivation of formerly active areas with endemic latency. 3. High-risk areas with stable viral activity over long periods. 4. High-risk areas which have expanded and merged with low-risk areas. 5. High-risk areas which have developed into endemic areas or become inactive. High-risk TBE areas from 1960-1975 (i.e. Mecklenburg-Western Pomerania) have since completely disappeared. There were, at the same time, high-risk areas in Thuringia which had only become latent and have now obviously become active again. The Odenwald demonstrated growing virus activity in the 1990s. These changes in TBE activity in German risk areas over more than the last 40 years are presented schematically. This ongoing number of risk areas is certainly linked to the notification obligation and greater public awareness. Nevertheless, any effects of ecological and climatic changes on the natural foci cannot be ruled out nor can changes in human leisure behaviour. Local weather conditions also have a major effect on the TBE incidence. Warm and dry summers may cause low tick activities, rainy summers may lead to low exposure rates of human beings. Even changes in forms of agricultural production prompted by different political structures probably have an impact as do economic constraints which may lead to lower vaccination and higher exposure rates. Regular, systematic virus prevalence measurements from 1997 to 2002 in field-collected ticks in German high-risk areas do not indicate any risk increase nor do they suggest a downward trend. Studies on virus prevalence in questing versus partially engorged ticks indicate that we neither exactly know nor understand the real quantitative relations between the virus and the host. In a first study, virus prevalence in Ixodes ricinus removed from humans was examined. Humans which were exposed in some districts near Passau in Bavaria. In the autumn of 2001, virus prevalence of unengorged free-living nymphs (n = 820) in this area was 0.38 (0.08-1.1)% and of adults (n = 90) 1.17 (0.03-6.38)%. Surprisingly, virus prevalence in partially engorged ticks from the same area collected during the same period was significantly higher (nymphs, n = 86, 6.9% and adults, n = 129, 9.3%). Virus-positive partially engorged ticks were only found in districts known as risk areas. Nucleotide and deduced amino acid sequence data of the PCR products have confirmed the presence of virus prototype Neudoerfl only.

DP015 Identification of a new class of mutants of the leader region of the ermA methylase

Tick-borne encephalitis (TBE) and Lyme borreliosis are the most common tick-borne zooanthroponoses in Germany. The federal risk map for TBE in this country is based on recorded cases of human infection, whereas information on the vector-based prevalence of either pathogen is fragmentary. In this study, a total of 12,497 host-seeking nymphal and adult Ixodes ricinus ticks (Acari: Ixodidae) were collected from March to October 2009 and April to June 2010, in 5 TBE non-risk and 4 TBE risk areas of the Rhine-Main region (Hesse) via flagging. A total of 3615 ticks was examined for infection with Borrelia burgdorferi sensu lato and 9115 ticks were analyzed for TBE virus (TBEV). Pathogens were detected by real-time polymerase chain reaction. Among 3615 questing ticks, 344 (9.5%) were found infected with B. burgdorferi sensu lato. Five Borrelia genospecies were identified by sequencing the OspA gene: B. afzelii (81.3%), B. garinii (14.0%), B. valaisiana (2.7%), B. spielmanii (1.3%), and B. bavariensis (0.7%). TBE infection of ticks differed between areas classified as TBE risk and TBE non-risk areas. While the prevalence of TBEV was between 0 and 0.2% (3 of 3947 ticks) in the TBE risk areas, no TBEV-infected tick was detected from TBE non-risk areas. The results show that B. burgdorferi sensu lato occurred in all 9 examined locations, indicating that Lyme borreliosis is prevalent in the Rhine-Main region, whereas TBEV was detected only in previously classified risk areas.