High risk of tick bites in Dutch gardens

Assessing tick attachments to humans with citizen science data: spatio-temporal mapping in Switzerland from 2015 to 2021 using spatialMaxent

BACKGROUND

Ticks are the primary vectors of numerous zoonotic pathogens, transmitting more pathogens than any other blood-feeding arthropod. In the northern hemisphere, tick-borne disease cases in humans, such as Lyme borreliosis and tick-borne encephalitis, have risen in recent years, and are a significant burden on public healthcare systems. The spread of these diseases is further reinforced by climate change, which leads to expanding tick habitats. Switzerland is among the countries in which tick-borne diseases are a major public health concern, with increasing incidence rates reported in recent years.

METHODS

In response to these challenges, the "Tick Prevention" app was developed by the Zurich University of Applied Sciences and operated by A&K Strategy Ltd. in Switzerland. The app allows for the collection of large amounts of data on tick attachment to humans through a citizen science approach. In this study, citizen science data were utilized to map tick attachment to humans in Switzerland at a 100 m spatial resolution, on a monthly basis, for the years 2015 to 2021. The maps were created using a state-of-the-art modeling approach with the software extension spatialMaxent, which accounts for spatial autocorrelation when creating Maxent models.

RESULTS

Our results consist of 84 maps displaying the risk of tick attachments to humans in Switzerland, with the model showing good overall performance, with median AUC ROC values ranging from 0.82 in 2018 to 0.92 in 2017 and 2021 and convincing spatial distribution, verified by tick experts for Switzerland. Our study reveals that tick attachment to humans is particularly high at the edges of settlement areas, especially in sparsely built-up suburban regions with green spaces, while it is lower in densely urbanized areas. Additionally, forested areas near cities also show increased risk levels.

CONCLUSIONS

This mapping aims to guide public health interventions to reduce human exposure to ticks and to inform the resource planning of healthcare facilities. Our findings suggest that citizen science data can be valuable for modeling and mapping tick attachment risk, indicating the potential of citizen science data for use in epidemiological surveillance and public healthcare planning.

Understanding Ixodes ricinus occurrence in private yards: influence of yard and landscape features

BACKGROUND

Lyme borreliosis is the most frequent zoonotic disease in the northern hemisphere and is transmitted by ticks of the genus Ixodes. Although many people are bitten by ticks in private yards, our understanding of the factors associated with their presence in these areas remains limited. To address this gap, we used a citizen science approach to identify the local and landscape features associated with tick presence in yards.

METHODS

This study was conducted near Nancy, a city in northeastern France, from 2020 to 2022. Citizen scientists collected ticks in their yard on a single event (n = 185) and measured 13 yard features. Additionally, we computed 11 features related to the landscape composition and spatial configuration surrounding these yards. Using generalized linear mixed models, we determined the yard and landscape features associated with the presence of ticks and nymphal Ixodes ricinus (hereafter nymphs), the life stage, and species that mostly bite humans.

RESULTS

Despite a low density, ticks were found in 32% of the yards, including yards in urbanized areas. At the transect level, the likelihood of finding a nymph was nearly three times higher in transects shaded by vegetation compared to those in open areas, with no relationship between nymph occurrence and transect location or grass height. At the yard level, the occurrence of ticks and nymphs was related to both yard and landscape characteristics. Nymph and tick occurrence were more than twice as high in yards with signs of deer and a wood/brush pile compared to those without these characteristics, and increased with the connectivity of vegetation areas and the percentage of forest areas in the landscape.

CONCLUSIONS

Our study reveals that private yards across an urbanization gradient are locations of tick exposure with tick presence linked to both yard and landscape factors. These findings emphasize the importance of public awareness regarding tick exposure in yards and provide crucial insights for future public health prevention campaigns.

Features in and around residential gardens affecting the presence and abundance of questing Ixodes ricinus ticks

People may be exposed to questing Ixodes ricinus ticks in urban settings, e.g. residential gardens. Little is known about the garden characteristics that support a tick population. To determine which features in and around residential gardens support or limit the occurrence and abundance of questing I. ricinus ticks, we sampled them in residential gardens in the Braunschweig region that differed in various intrinsic and extrinsic parameters. We recorded the number of questing nymphal and adult ticks on transects, and by using mixed-effects generalized linear regression models, we related their occurrence and abundance to garden characteristics, meteorological covariates, and landscape features in the vicinity. We detected questing I. ricinus ticks in about 90% of the 103 surveyed gardens. Our occurrence model (marginal R2 = 0.31) predicted the highest probability of questing ticks on transects with hedges or groundcover in gardens, which are located in neighborhoods with large proportions of forest. The abundance of questing ticks was similarly influenced. We conclude that I. ricinus ticks are frequent in residential gardens in Northern Germany and likely associated with intrinsic garden characteristics on a small scale, such as hedges, as well as extrinsic factors on a local scale, such as the proportion of nearby woodland.

Linking human tick bite risk with tick abundance in the environment: A novel approach to quantify tick bite risk using orienteers in Scotland

The rate that people are bitten by ticks is critical in determining the risk of tick-borne infections but is rarely quantified accurately. Often tick abundance in the environment is used as a proxy for tick bite risk, but the relationship with risk is poorly understood. We used a novel citizen science approach to measure tick bite rate in orienteers, to assess the relationship between tick abundance and tick bite risk and to identify risk factors for tick bites. Eleven orienteering events were attended in Scotland between August 2018 and September 2019. The number of tick bites in orienteers, and the time and distance of activity were collected using an online questionnaire. Tick abundance in the same areas used for the orienteering events was estimated by surveying ticks on ground vegetation using blanket drags. Among orienteers, mean incidence was 409 tick bites per 1,000 person-hours. Tick abundance and tick bite rate were strongly correlated, indicating that data from questing tick surveys is a useful proxy for the risk of human tick bites. Tick bite rate was better explained by the activity duration than distance covered and was higher in orienteers that ran earlier in the day, exposed to higher temperatures and in woodland habitats. This study highlights the value of the citizen science approach used, which crucially included submission of activity reports both with and without ticks, to generate robust data on tick bite rate. Accurately measuring tick bite rate and understanding environmental factors that influence it are essential in mitigating the risk of tick-borne diseases.

A One Health Evaluation of the Surveillance Systems on Tick-Borne Diseases in the Netherlands, Spain and Italy

Simple Summary

Ixodid ticks and tick-borne diseases are expanding their geographical range, but surveillance activities vary among countries. We analysed the surveillance systems in place in the Netherlands, Spain and Italy, to identify ideal elements to monitor tick-borne diseases, by using a One Health evaluation protocol. We identified differences among the three surveillance systems, with the Dutch initiative showing a high level of transdisciplinary collaboration, good identification of the actors and engagement of the public in research and education. Measurable outcomes have been generated, such as the reduction in tick bites and the discovery of new pathogens and tick species. In Italy and Spain, surveillance systems are based on compulsory notification to health authorities; legislation seems relevant but law enforcement alongside the availability of economic resources is rather fragmented and limited to the most severe diseases. The non-scientific community is marginally considered and collaborations are limited to local initiatives. Research activities in both countries have mostly contributed to gaining knowledge on the distribution of tick species and the discovery of new pathogens. Although all TBD surveillance plans comply with the EU regulations, the initiatives characterised by trans-disciplinary collaboration may be more effective for the surveillance and prevention of tick-transmitted diseases.

Abstract

To identify ideal elements for the monitoring and prevention of tick-borne diseases (TBD), we analysed the surveillance systems in place in the Netherlands, Spain and Italy. We applied a semi-quantitative evaluation to identify outcomes and assess the degree of One Health implementation. Differences emerged in the surveillance initiatives, as well as the One Health scores. The Dutch surveillance is dominated by a high level of transdisciplinary and trans-sectoral collaboration, enabling communication and data sharing among actors. Different project-based monitoring, research and educational activities are centrally coordinated and the non-scientific community is actively involved. All this yielded measurable health outcomes. In Italy and Spain, TBD surveillance and reporting systems are based on compulsory notification. Law enforcement, alongside dedicated time and availability of economic resources, is fragmented and limited to the most severe health issues. Veterinary and human medicine are the most involved disciplines, with the first prevailing in some contexts. Stakeholders are marginally considered and collaborations limited to local initiatives. Research activities have mostly contributed to gaining knowledge on the distribution of tick vectors and discovery of new pathogens. Although all TBD surveillance plans comply with EU regulations, initiatives characterised by transdisciplinary collaboration may be more effective for the surveillance and prevention of TBD.

Tick-Borne Encephalitis Risk Increases with Dog Ownership, Frequent Walks, and Gardening: A Case-Control Study in Germany 2018-2020

In Germany, tick-borne encephalitis (TBE) infections mainly occur in southern regions. Despite recent increases in incidence, TBE vaccination coverage remains low, necessitating additional preventive strategies against TBE. Our case-control study in Southern Germany from 2018 to 2020 mapped knowledge/application of tick-protective strategies and identified TBE risk factors. We calculated odds ratios (OR), with 95% confidence intervals (CI). We interviewed 581 cases and 975 matched controls. Most participants recalled lifetime tick bites, mainly while walking, gardening, or hiking. However, only 45% of cases noticed ticks during exposure time; another 12% reported unpasteurized milk intake. While tick-protection knowledge was satisfactory, application lagged behind. Risk factors included dog ownership (OR = 2.45, 95% CI: 1.85−3.24), walks ≥ 4×/week (OR = 2.11, 95% CI: 1.42−3.12), gardening ≥ 4×/week (OR = 1.83, 95% CI: 1.11−3.02), and garden proximity < 250 m of forests (OR = 2.54, 95% CI: 1.82−3.56). Applying ≥2 tick-protective strategies (OR = 0.52, 95% CI: 0.40−0.68) and keeping lawns mowed (OR = 0.63, 95% CI: 0.43−0.91) were inversely associated with TBE. In 2020 (likely pandemic-related), cases reported significantly more walks than previously, potentially explaining the record high case numbers. Our findings provide guidance on targets for TBE prevention. Persons with gardens near forests, frequent outdoor activities, or dogs could particularly benefit from targeted information, including on vaccination and preventing tick bites.

Geo-Spatial Characteristics of 567 Places of Tick-Borne Encephalitis Infection in Southern Germany, 2018-2020

Tick-borne encephalitis (TBE) is a growing public health problem with increasing incidence and expanding risk areas. Improved prevention requires better understanding of the spatial distribution and ecological determinants of TBE transmission. However, a TBE risk map at sub-district level is still missing for Germany. We investigated the distribution and geo-spatial characteristics of 567 self-reported places of probable TBE infection (POI) from 359 cases notified in 2018-2020 in the study area of Bavaria and Baden-Wuerttemberg, compared to 41 confirmed TBE foci and 1701 random comparator places. We built an ecological niche model to interpolate TBE risk to the entire study area. POI were distributed heterogeneously at sub-district level, as predicted probabilities varied markedly across regions (range 0-93%). POI were spatially associated with abiotic, biotic, and anthropogenic geo-spatial characteristics, including summer precipitation, population density, and annual frost days. The model performed with 69% sensitivity and 63% specificity at an optimised probability threshold (0.28) and an area under the curve of 0.73. We observed high predictive probabilities in small-scale areas, consistent with the known circulation of the TBE virus in spatially restricted microfoci. Supported by further field work, our findings may help identify new TBE foci. Our fine-grained risk map could supplement targeted prevention in risk areas.

Spatial tick bite exposure and associated risk factors in Scandinavia

Tick-borne diseases are emerging and re-emerging threats causing public health concerns in Europe and North America. Prevention and control requires understanding of human exposure and behaviour. The aim was to measure exposure to tick bites across Scandinavia, its spatial distribution and the associated risk factors. Methods We sent a web-based survey to a randomly chosen population and analysed answers by Principal Component Analysis and Chi-Square. Individual responses were aggregated at the municipality level to assess the spatial distribution of bites. Results Nearly 60% of adults reported bites at low levels (1-5 bites); however, the majority were not in their resident municipality. We found two spatial profiles: In their home municipalities, people were most often bitten in less, but not the least, urbanized areas. When visiting other municipalities, people were most frequently bitten in peri-urban areas. Running/walking in the forest, gardening, and paddling/rowing were activities most strongly associated with bites. Conclusion Tick bites affect the entire Scandinavian population, with a higher risk in Sweden compared to Denmark and Norway. The frequency of observation of ticks in the environment or on pets might be used as a proxy for the actual risk of exposure to tick bites. Our results indicates that urban-dwelling outdoor enthusiasts and inhabitants of rural areas must be equally targeted for prevention campaigns.

Modelling tick bite risk by combining random forests and count data regression models

The socio-economic and demographic changes that occurred over the past 50 years have dramatically expanded urban areas around the globe, thus bringing urban settlers in closer contact with nature. Ticks have trespassed the limits of forests and grasslands to start inhabiting green spaces within metropolitan areas. Hence, the transmission of pathogens causing tick-borne diseases is an important threat to public health. Using volunteered tick bite reports collected by two Dutch initiatives, here we present a method to model tick bite risk using human exposure and tick hazard predictors. Our method represents a step forward in risk modelling, since we combine a well-known ensemble learning method, Random Forest, with four count data models of the (zero-inflated) Poisson family. This combination allows us to better model the disproportions inherent in the volunteered tick bite reports. Unlike canonical machine learning models, our method can capture the overdispersion or zero-inflation inherent in data, thus yielding tick bite risk predictions that resemble the original signal captured by volunteers. Mapping model predictions enables a visual inspection of the spatial patterns of tick bite risk in the Netherlands. The Veluwe national park and the Utrechtse Heuvelrug forest, which are large forest-urban interfaces with several cities, are areas with high tick bite risk. This is expected, since these are popular places for recreation and tick activity is high in forests. However, our model can also predict high risk in less-intensively visited recreational areas, such as the patchy forests in the northeast of the country, the natural areas along the coastline, or some of the Frisian Islands. Our model could help public health specialists to design mitigation strategies for tick-borne diseases, and to target risky areas with awareness and prevention campaigns.

Seasonality and anatomical location of human tick bites in the United Kingdom

Tick bites on humans can occur in a variety of habitats and may result in the transmission of tick-borne pathogens, such as the causative agent of Lyme borreliosis (LB), Borrelia burgdorferi sensu lato. As the risk of transmission of this pathogen to the host increases with the duration of tick feeding, the recognition and removal of ticks as soon as possible following attachment is important for reducing the risk of infection. Performing a thorough body examination for ticks following potential exposure is recommended by tick awareness campaigns. Knowledge of where on the body feeding ticks are frequently found, and at which times of year peak tick exposure occurs, provides important information for public health messaging and may aid those bitten by ticks to engage more effectively with tick-checking behaviour. This paper summarizes human tick bites in the United Kingdom (UK) during 2013-2018 reported to Public Health England's passive Tick Surveillance Scheme and further examines the anatomical location and seasonality of bites from the most commonly encountered tick and LB vector Ixodes ricinus. A total of 1,328 tick records from humans were received of which 93% were I. ricinus. Humans were most commonly bitten by I. ricinus nymphs (70% bites). Tick bites were recorded on all parts of the body, but there were significant differences in their anatomical location on adults and children. Most tick bites on adults occurred on the legs (50%), whereas on children tick bites were mostly on the head and neck (43%). Bites from I. ricinus were recorded throughout the year but were most numerous during May to August. This study adds to the body of research on the seasonality and anatomical location of human tick bites in temperate Europe and highlights the importance of data collected through passive surveillance in addition to research and epidemiological studies.

Seropositivity to Midichloria mitochondrii (order Rickettsiales) as a marker to determine the exposure of humans to tick bite

Ixodes ricinus is the most common tick species parasitizing humans in Europe, and the main vector of Borrelia burgdorferi sensu lato, the causative agent of Lyme disease in the continent. This tick species also harbors the endosymbiont Midichloria mitochondrii, and there is strong evidence that this bacterium is inoculated into the vertebrate host during the blood meal. A high proportion of tick bites remains unnoticed due to rarity of immediate symptoms, implying the risk of occult tick-borne infections in turn a potential risk factor for the onset of chronic-degenerative diseases. Since suitable tools to determine the previous exposure to I. ricinus bites are needed, this work investigated whether seropositivity toward a protein of M. mitochondrii (rFliD) could represent a marker for diagnosis of I. ricinus bite. We screened 274 sera collected from patients from several European countries, at different risk of tick bite, using an ELISA protocol. Our results show a clear trend indicating that positivity to rFliD is higher where the tick bite can be regarded as certain/almost certain, and lower where there is an uncertainty on the bite, with the highest positivity in Lyme patients (47.30%) and the lowest (2.00%) in negative controls. According to the obtained results, M. mitochondrii can be regarded as a useful source of antigens, with the potential to be used to assess the exposure to ticks harboring this bacterium. In prospect, additional antigens from M. mitochondrii and tick salivary glands should be investigated and incorporated in a multi-antigen test for tick bite diagnosis.

Time of year and outdoor recreation affect human exposure to ticks in California, United States

Interactions between humans and ticks are often measured indirectly, using surveillance of tick population abundance and pathogen prevalence, or reported human disease data. We used data garnered as part of a free national citizen science research effort to describe actual human exposures to ticks in California. Human-biting ticks (n = 1,905) submitted for identification were predominantly western black-legged ticks (Ixodes pacificus) (68%), American dog ticks (Dermacentor variabilis) (24%), and Pacific Coast ticks (Dermacentor occidentalis) (7%). Tick exposure occurred predominantly during recreational use of the outdoors, rather than exposure near the home environment. Tick submissions peaked in May, but human exposure to ticks occurred throughout the year. Adult I. pacificus were most frequently found on humans during March-May, though previous research demonstrates that questing adults on vegetation are more abundant earlier in the winter.

Lyme Disease Risks in Europe under Multiple Uncertain Drivers of Change

BACKGROUND

Debates over whether climate change could lead to the amplification of Lyme disease (LD) risk in the future have received much attention. Although recent large-scale disease mapping studies project an overall increase in Lyme disease risk as the climate warms, such conclusions are based on climate-driven models in which other drivers of change, such as land-use/cover and host population distribution, are less considered.

OBJECTIVES

The main objectives were to project the likely future ecological risk patterns of LD in Europe under different assumptions about future socioeconomic and climate conditions and to explore similarity and uncertainty in the projected risks.

METHODS

An integrative, spatially explicit modeling study of the ecological risk patterns of LD in Europe was conducted by applying recent advances in process-based modeling of tick-borne diseases, species distribution mapping, and scenarios of land-use/cover change. We drove the model with stakeholder-driven, integrated scenarios of plausible future socioeconomic and climate change [the Shared Socioeconomic Pathway (SSPs) combined with the Representative Concentration Pathways (RCPs)].

RESULTS

The model projections suggest that future temperature increases may not always amplify LD risk: Low emissions scenarios (RCP2.6) combined with a sustainability socioeconomic scenario (SSP1) resulted in reduced LD risk. The greatest increase in risk was projected under intermediate (RCP4.5) rather than high-end (RCP8.5) climate change scenarios. Climate and land-use change were projected to have different roles in shaping the future regional dynamics of risk, with climate warming being likely to cause risk expansion in northern Europe and conversion of forest to agriculture being likely to limit risk in southern Europe.

CONCLUSIONS

Projected regional differences in LD risk resulted from mixed effects of temperature, land use, and host distributions, suggesting region-specific and cross-sectoral foci for LD risk management policy. The integrated model provides an improved explanatory tool for the system mechanisms of LD pathogen transmission and how pathogen transmission could respond to combined socioeconomic and climate changes. https://doi.org/10.1289/EHP4615.

[Ecology of Lyme disease]

Diseases spread by ticks are complex and typically come under the One Health approach because the implications for human, animal and environmental health are so intricately interconnected. In Europe and North America, these diseases, particularly the emblematic case of Lyme disease, are constantly on the rise. They are associated with a very strong emotional element in Western societies, where citizens are preoccupied by this upsurge and call on governments and health services to act. There is no vaccine against Lyme disease. This is the backdrop against which scientists are looking for alternative solutions based on the identification of ecological factors that are liable to better control tick populations and the movements of pathogens within ecosystems. This article describes the main knowledge already acquired about the ecology of Lyme disease and then provides a list of a number of instruments that can be leveraged to limit the risks and improve control.

Using volunteered observations to map human exposure to ticks

Lyme borreliosis (LB) is the most prevalent tick-borne disease in Europe and its incidence has steadily increased over the last two decades. In the Netherlands alone, more than 20,000 citizens are affected by LB each year. Because of this, two Dutch citizen science projects were started to monitor tick bites. Both projects have collected nearly 50,000 geo-located tick bite reports over the period 2006–2016. The number of tick bite reports per area unit is a proxy of tick bite risk. This risk can also be modelled as the result of the interaction of hazard (e.g. tick activity) and human exposure (e.g. outdoor recreational activities). Multiple studies have focused on quantifying tick hazard. However, quantifying human exposure is a harder task. In this work, we make a first step to map human exposure to ticks by combining tick bite reports with a tick hazard model. Our results show human exposure to tick bites in all forested areas of the Netherlands. This information could facilitate the cooperation between public health specialists and forest managers to create better mitigation campaigns for tick-borne diseases, and it could also support the design of improved plans for ecosystem management.

Incidence of notified Lyme borreliosis in Germany, 2013-2017

Lyme borreliosis (LB) is the most commonly reported tick-borne disease in Germany. In 9/16 states, notification of erythema migrans (EM), acute neuroborreliosis (NB) and Lyme arthritis (LA) is mandatory. We describe incidence measures, time trends, geographical distribution and frequencies of manifestations to better understand LB epidemiology and target prevention measures. We used cases notified in the 9 states and confirmed by local health offices, 2013-2017, to calculate incidences by time, place and person. Altogether, we observed 56,446 cases. Disease onset peaked yearly in July. Incidence ranged from 26/100,000 (2015) to 41/100,000 (2013) with mean annual incidences 2013-2017 on district level between 0.5/100,000 and 138/100,000. Median age was 54 years with peaks in boys (5-9 years, mean incidence 36/100,000) and women (50-69 years, mean incidence 57/100,000). 95% experienced EM only, 2.7% NB and 2.1% LA. 54% were female, but more men had NB (56%) and LA (53%, p < 0.001). Hospitalisation was recorded for 10% of LA and 71% of NB cases. LB remains an important public health concern in Germany with marked regional variation. To facilitate early diagnosis and treatment, health authorities should raise awareness among physicians and promote prevention strategies among the general population: tick-bite-protection, prompt tick removal and medical consultation.

Neglected vector-borne zoonoses in Europe: Into the wild

Wild vertebrates are involved in the transmission cycles of numerous pathogens. Additionally, they can affect the abundance of arthropod vectors. Urbanization, landscape and climate changes, and the adaptation of vectors and wildlife to human habitats represent complex and evolving scenarios, which affect the interface of vector, wildlife and human populations, frequently with a consequent increase in zoonotic risk. While considerable attention has focused on these interrelations with regard to certain major vector-borne pathogens such as Borrelia burgdorferi s.l. and tick-borne encephalitis virus, information regarding many other zoonotic pathogens is more dispersed. In this review, we discuss the possible role of wildlife in the maintenance and spread of some of these neglected zoonoses in Europe. We present case studies on the role of rodents in the cycles of Bartonella spp., of wild ungulates in the cycle of Babesia spp., and of various wildlife species in the life cycle of Leishmania infantum, Anaplasma phagocytophilum and Rickettsia spp. These examples highlight the usefulness of surveillance strategies focused on neglected zoonotic agents in wildlife as a source of valuable information for health professionals, nature managers and (local) decision-makers. These benefits could be further enhanced by increased collaboration between researchers and stakeholders across Europe and a more harmonised and coordinated approach for data collection.

Melting pot of tick-borne zoonoses: the European hedgehog contributes to the maintenance of various tick-borne diseases in natural cycles urban and suburban areas

Background

European hedgehogs (Erinaceus europaeus) are urban dwellers and host both Ixodes ricinus and Ixodes hexagonus. These ticks transmit several zoonotic pathogens like Borrelia burgdorferi (sensu lato), Anaplasma phagocytophilum, Rickettsia helvetica, Borrelia miyamotoi and “Candidatus Neoehrlichia mikurensis”. It is unclear to what extent hedgehogs in (sub) urban areas contribute to the presence of infected ticks in these areas, which subsequently pose a risk for acquiring a tick-borne disease. Therefore, it is important to investigate to what extent hedgehogs contribute to the enzootic cycle of these tick-borne pathogens, and to shed more light at the mechanisms of the transmission cycles involving hedgehogs and both ixodid tick species.

Methods

Engorged ticks from hedgehogs were collected from (sub) urban areas via rehabilitating centres in Belgium. Ticks were screened individually for presence of Borrelia burgdorferi (sensu lato), Borrelia miyamotoi, Anaplasma phagocytophilum, Rickettsia helvetica and “Candidatus Neoehrlichia mikurensis” using PCR-based methods. Infection rates of the different pathogens in ticks were calculated and compared to infection rates in questing ticks.

Results

Both Ixodes hexagonus (n = 1132) and Ixodes ricinus (n = 73) of all life stages were found on the 54 investigated hedgehogs. Only a few hedgehogs carried most of the ticks, with 6 of the 54 hedgehogs carrying more than half of all ticks (624/1205). Borrelia miyamotoi, A. phagocytophilum, R. helvetica and B. burgdorferi genospecies (Borrelia afzelii, Borrelia bavariensis and Borrelia spielmanii) were detected in both I. hexagonus and I. ricinus. Anaplasma phagocytophilum, R. helvetica, B. afzelii, B. bavariensis and B. spielmanii were found significantly more in engorged ticks in comparison to questing I. ricinus.

Conclusions

European hedgehogs seem to contribute to the spread and transmission of tick-borne pathogens in urban areas. The relatively high prevalence of B. bavariensis, B. spielmanii, B. afzelii, A. phagocytophilum and R. helvetica in engorged ticks suggests that hedgehogs contribute to their enzootic cycles in (sub) urban areas. The extent to which hedgehogs can independently maintain these agents in natural cycles, and the role of other hosts (rodents and birds) remain to be investigated.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2065-0) contains supplementary material, which is available to authorized users.

The natural infection of birds and ticks feeding on birds with Rickettsia spp. and Coxiella burnetii in Slovakia

Ixodid ticks (Acari: Ixodidae) are known as primary vectors of many pathogens causing diseases in humans and animals. Ixodes ricinus is a common ectoparasite in Europe and birds are often hosts of subadult stages of the tick. From 2012 to 2013, 347 birds belonging to 43 species were caught and examined for ticks in three sites of Slovakia. Ticks and blood samples from birds were analysed individually for the presence of Rickettsia spp. and Coxiella burnetii by PCR-based methods. Only I. ricinus was found to infest birds. In total 594 specimens of bird-attached ticks were collected (451 larvae, 142 nymphs, 1 female). Altogether 37.2% (16/43) of bird species were infested by ticks and some birds carried more than one tick. The great tit, Parus major (83.8%, 31/37) was the most infested species. In total, 6.6 and 2.7% of bird-attached ticks were infected with Rickettsia spp. and C. burnetii, respectively. Rickettsia helvetica predominated (5.9%), whereas R. monacensis (0.5%) was only sporadically detected. Coxiella burnetii was detected in 0.9%, Rickettsia spp. in 8.9% and R. helvetica in 4.2% of bird blood samples. The great tit was the bird species most infested with I. ricinus, carried R. helvetica and C. burnetti positive tick larvae and nymphs and was found to be rickettsaemic in its blood. Further studies are necessary to define the role of birds in the circulation of rickettsiae and C. burnetii in natural foci.

Increasing Residential Proximity of Lyme Borreliosis Cases to High-Risk Habitats: A Retrospective Study in Central Bohemia, the Czech Republic, 1987-2010

An analysis of historical data on Lyme borreliosis in Central Bohemia between 1987-2010 has revealed that the rate of peri-domestic exposure, the proximity of patients' residences to high-risk habitats, and the number of disease cases have been interdependent variables and that their common upturn can be dated back to the start of the 1990s or earlier. The data indicate that the disease rise is attributable to translocation of part of the at-risk population nearer to natural environments, rather than to mere intensification of people's peri-domestic exposure at existing residential locations, or changes in the natural environment itself.

Improving national surveillance of Lyme neuroborreliosis in Denmark through electronic reporting of specific antibody index testing from 2010 to 2012

Our aim was to evaluate the results of automated surveillance of Lyme neuroborreliosis (LNB) in Denmark using the national microbiology database (MiBa), and to describe the epidemiology of laboratory-confirmed LNB at a national level. MiBa-based surveillance includes electronic transfer of laboratory results, in contrast to the statutory surveillance based on manually processed notifications. Antibody index (AI) testing is the recommend laboratory test to support the diagnosis of LNB in Denmark. In the period from 2010 to 2012, 217 clinical cases of LNB were notified to the statutory surveillance system, while 533 cases were reported AI positive by the MiBa system. Thirty-five unconfirmed cases (29 AI-negative and 6 not tested) were notified, but not captured by MiBa. Using MiBa, the number of reported cases was increased almost 2.5 times. Furthermore, the reporting was timelier (median lag time: 6 vs 58 days). Average annual incidence of AI-confirmed LNB in Denmark was 3.2/100,000 population and incidences stratified by municipality ranged from none to above 10/100,000. This is the first study reporting nationwide incidence of LNB using objective laboratory criteria. Laboratory-based surveillance with electronic data-transfer was more accurate, complete and timely compared to the surveillance based on manually processed notifications. We propose using AI test results for LNB surveillance instead of clinical reporting.

Vector-borne disease intelligence: strategies to deal with disease burden and threats

Owing to the complex nature of vector-borne diseases (VBDs), whereby monitoring of human case patients does not suffice, public health authorities experience challenges in surveillance and control of VBDs. Knowledge on the presence and distribution of vectors and the pathogens that they transmit is vital to the risk assessment process to permit effective early warning, surveillance, and control of VBDs. Upon accepting this reality, public health authorities face an ever-increasing range of possible surveillance targets and an associated prioritization process. Here, we propose a comprehensive approach that integrates three surveillance strategies: population-based surveillance, disease-based surveillance, and context-based surveillance for EU member states to tailor the best surveillance strategy for control of VBDs in their geographic region. By classifying the surveillance structure into five different contexts, we hope to provide guidance in optimizing surveillance efforts. Contextual surveillance strategies for VBDs entail combining organization and data collection approaches that result in disease intelligence rather than a preset static structure.

Peri-urbanisation, counter-urbanisation, and an extension of residential exposure to ticks: a clue to the trends in Lyme borreliosis incidence in the Czech Republic?

The incidence of tick-borne human diseases (TBD) in the Czech Republic (CZ) is on the increase, driven by infections increasingly acquired in residential locations, earlier in spring and later in autumn, and among children and the elderly. To interpret these trends, data on Lyme borreliosis (LB) incidence between 1997 and 2010 were analysed in the context of population migration flows registered in the CZ during the same period. Analysis showed that a migration stream of families with children, and of the elderly, flowed from more urbanized and densely populated localities to those more rural and less populated, where the chance of acquiring LB in the home vicinity was greater than in the urban settings. By contrast, a stream of people in the life phase between early adulthood and family formation flowed reversely, corresponding to a prominent absence of this age category from the patient spectrum. The data further showed that the more the residential exposure became prevalent, the more people were in year-round (rather than in summertime only) contact with ticks, which accounts for an extension of the cases' seasonal distribution as well as for an overall increase in case numbers. Finally, the fact that majority of the urban-to-rural migrants could be categorised as wealthier people could explain the previously noticed lack of low-status people among TBD patients in the CZ.

ANTIDotE: anti-tick vaccines to prevent tick-borne diseases in Europe

Ixodes ricinus transmits bacterial, protozoal and viral pathogens, causing disease and forming an increasing health concern in Europe. ANTIDotE is an European Commission funded consortium of seven institutes, which aims to identify and characterize tick proteins involved in feeding and pathogen transmission. The knowledge gained will be used to develop and evaluate anti-tick vaccines that may prevent multiple human tick-borne diseases. Strategies encompassing anti-tick vaccines to prevent transmission of pathogens to humans, animals or wildlife will be developed with relevant stakeholders with the ultimate aim of reducing the incidence of tick-borne diseases in humans.