Trends in ixodid tick abundance and distribution in Great Britain

Coinfection of Babesia and Borrelia in the Tick Ixodes ricinus-A Neglected Public Health Issue in Europe?

Ixodes ricinus nymphs and adults removed from humans, and larvae and nymphs from birds, have been analysed for infection with Babesia species and Borrelia species previously in separately published studies. Here, we use the same data set to explore the coinfection pattern of Babesia and Borrelia species in the ticks. We also provide an overview of the ecology and potential public health importance in Sweden of I. ricinus infected both with zoonotic Babesia and Borrelia species. Among 1952 nymphs and adult ticks removed from humans, 3.1% were PCR-positive for Babesia spp. Of these Babesia-positive ticks, 43% were simultaneously Borrelia-positive. Among 1046 immatures of I. ricinus removed from birds, 2.5% were Babesia-positive, of which 38% were coinfected with Borrelia species. This study shows that in I. ricinus infesting humans or birds in Sweden, potentially zoonotic Babesia protozoa sometimes co-occur with human-pathogenic Borrelia spp. Diagnostic tests for Babesia spp. infection are rarely performed in Europe, and the medical significance of this pathogen in Europe could be underestimated.

The Impact of Host Abundance on the Epidemiology of Tick-Borne Infection

Tick-borne diseases are an increasing global public health concern due to an expanding geographical range and increase in abundance of tick-borne infectious agents. A potential explanation for the rising impact of tick-borne diseases is an increase in tick abundance which may be linked to an increase in density of the hosts on which they feed. In this study, we develop a model framework to understand the link between host density, tick demography and tick-borne pathogen epidemiology. Our model links the development of specific tick stages to the specific hosts on which they feed. We show that host community composition and host density have an impact on tick population dynamics and that this has a consequent impact on host and tick epidemiological dynamics. A key result is that our model framework can exhibit variation in host infection prevalence for a fixed density of one host type due to changes in density of other host types that support different tick life stages. Our findings suggest that host community composition may play a crucial role in explaining the variation in prevalence of tick-borne infections in hosts observed in the field.

Diversity and Geographic Distribution of Dog Tick Species in Sri Lanka and the Life Cycle of Brown Dog Tick, Rhipicephalus sanguineus Under Laboratory Conditions

PURPOSE

This study determined the diversity and distribution of tick species infesting domestic dogs and the life cycle parameters of the dominant dog tick species.

METHODS

An island-wide, cross-sectional survey of tick species infesting domestic dogs was carried out, and the life cycle of the most commonly occurring dog tick, Rhipicephalus sanguineus was studied under laboratory conditions.

RESULTS

A total of 3026 ticks were collected from 1219 dogs in all 25 districts. Eight species in five genera were identified: R. sanguineus (63.4%), R. haemaphysaloides (22.0%), Haemaphysalis bispinosa (12.5%), Haemaphysalis intermedia (0.9%), Haemaphysalis turturis (0.6%), Amblyomma integrum (0.4%), Dermacentor auratus (0.2%) and Hyalomma sp (0.1%). R. sanguineus was the dominant species in the Dry and Wet zones, while R. haemaphysaloides was the dominant species in the Intermediate Zone. Species diversity (Shannon diversity index H) was 1.135, 1.021and 0.849 in the Intermediate, Dry and Wet zones, respectively. The three-host life cycle of R. sanguineus was completed within 70-126 days, and all three stages successfully fed on New Zealand white rabbits under laboratory conditions. The Reproductive Efficiency Index (REI) and Reproductive Fitness Index (RFI) were 50.8 ± 9.69 and 9.1 ± 5.01, respectively. Larger females had higher reproductive success.

CONCLUSIONS

Of the eight species infesting domestic dogs in Sri Lanka, R. sanguineaus was the most frequently occurring tick species. The three-host life cycle of R. sanguineus was successfully completed within an average of 98 days on New Zealand white rabbits. The number of eggs laid, duration of the pre-oviposition period, incubation period and parasitic periods of all three life stages were lower than in previous records.

Predicting the current and future risk of ticks on livestock farms in Britain using random forest models

The most abundant tick species in northern Europe, Ixodes ricinus, transmits a range of pathogens that cause disease in livestock. As I. ricinus distribution is influenced by climate, tick-borne disease risk is expected to change in the future. The aims of this work were to build a spatial model to predict current and future risk of ticks on livestock farms across Britain. Variables relating both to tick hazard and livestock exposure were included, to capture a niche which may be missed by broader scale models. A random forest machine learning model was used due to its ability to cope with correlated variables and interactions. Data on tick presence and absence on sheep and cattle farms was obtained from a retrospective questionnaire survey of 926 farmers. The ROC of the final model was 0.80. The model outputs matched observed patterns of tick distribution, with areas of highest tick risk in southwest and northwest England, Wales, and west Scotland. Overall, the probability of tick presence on livestock farms was predicted to increase by 5-7 % across Britain under future climate scenarios. The predicted increase is greater at higher altitudes and latitudes, further increasing the risk of tick-borne disease on farms in these areas.

Predicting habitat suitability for Ixodes ricinus and Ixodes persulcatus ticks in Finland

Background

Ticks are responsible for transmitting several notable pathogens worldwide. Finland lies in a zone where two human-biting tick species co-occur: Ixodesricinus and Ixodespersulcatus. Tick densities have increased in boreal regions worldwide during past decades, and tick-borne pathogens have been identified as one of the major threats to public health in the face of climate change.

Methods

We used species distribution modelling techniques to predict the distributions of I.ricinus and I.persulcatus, using aggregated historical data from 2014 to 2020 and new tick occurrence data from 2021. By aiming to fill the gaps in tick occurrence data, we created a new sampling strategy across Finland. We also screened for tick-borne encephalitis virus (TBEV) and Borrelia from the newly collected ticks. Climate, land use and vegetation data, and population densities of the tick hosts were used in various combinations on four data sets to estimate tick species’ distributions across mainland Finland with a 1-km resolution.

Results

In the 2021 survey, 89 new locations were sampled of which 25 new presences and 63 absences were found for I.ricinus and one new presence and 88 absences for I.persulcatus. A total of 502 ticks were collected and analysed; no ticks were positive for TBEV, while 56 (47%) of the 120 pools, including adult, nymph, and larva pools, were positive for Borrelia (minimum infection rate 11.2%, respectively). Our prediction results demonstrate that two combined predictor data sets based on ensemble mean models yielded the highest predictive accuracy for both I.ricinus (AUC = 0.91, 0.94) and I.persulcatus (AUC = 0.93, 0.96). The suitable habitats for I.ricinus were determined by higher relative humidity, air temperature, precipitation sum, and middle-infrared reflectance levels and higher densities of white-tailed deer, European hare, and red fox. For I.persulcatus, locations with greater precipitation and air temperature and higher white-tailed deer, roe deer, and mountain hare densities were associated with higher occurrence probabilities. Suitable habitats for I.ricinus ranged from southern Finland up to Central Ostrobothnia and North Karelia, excluding areas in Ostrobothnia and Pirkanmaa. For I.persulcatus, suitable areas were located along the western coast from Ostrobothnia to southern Lapland, in North Karelia, North Savo, Kainuu, and areas in Pirkanmaa and Päijät-Häme.

Conclusions

This is the first study conducted in Finland that estimates potential tick species distributions using environmental and host data. Our results can be utilized in vector control strategies, as supporting material in recommendations issued by public health authorities, and as predictor data for modelling the risk for tick-borne diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05410-8.

One Health Approach to Tick and Tick-Borne Disease Surveillance in the United Kingdom

Where ticks are found, tick-borne diseases can present a threat to human and animal health. The aetiology of many of these important diseases, including Lyme disease, bovine babesiosis, tick-borne fever and louping ill, have been known for decades whilst others have only recently been documented in the United Kingdom (UK). Further threats such as the importation of exotic ticks through human activity or bird migration, combined with changes to either the habitat or climate could increase the risk of tick-borne disease persistence and transmission. Prevention of tick-borne diseases for the human population and animals (both livestock and companion) is dependent on a thorough understanding of where and when pathogen transmission occurs. This information can only be gained through surveillance that seeks to identify where tick populations are distributed, which pathogens are present within those populations, and the periods of the year when ticks are active. To achieve this, a variety of approaches can be applied to enhance knowledge utilising a diverse range of stakeholders (public health professionals and veterinarians through to citizen scientists). Without this information, the application of mitigation strategies to reduce pathogen transmission and impact is compromised and the ability to monitor the effects of climate change or landscape modification on the risk of tick-borne disease is more challenging. However, as with many public and animal health interventions, there needs to be a cost-benefit assessment on the most appropriate intervention applied. This review will assess the challenges of tick-borne diseases in the UK and argue for a cross-disciplinary approach to their surveillance and control.

Successful Deer Management in Scotland Requires Less Conflict Not More

What would successful deer management look like in Scotland? To some, flourishing populations of native wild deer represent success. But to others, negative impacts such as damage to woodlands and peatlands, agricultural and forestry losses, deer-vehicle collisions, and facilitating Lyme disease spread represent failure. Conflicting interests and incentives among people involved in deer management mean a common definition of success, and therefore clear management targets, remain elusive. While some environmental groups urgently call for an increase in the number of deer culled (shot) each year, other stakeholders aim to maximize deer numbers. Overcoming this governance failure will require clearly articulated, scientifically valid, and socially acceptable socio-ecological objectives to be co-produced by a broad range of stakeholders. Systematic monitoring of deer impacts will also be needed to evaluate the ability of specific management interventions to achieve defined objectives. Reintroducing Eurasian lynx (Lynx lynx) has been suggested as a means to reduce deer numbers and their negative ecological and socioeconomic impacts. However, evidence of lynx impacts on deer numbers, deer impacts, and social conflicts over deer suggest lynx reintroduction alone would not effectively reduce negative impacts of deer in Scotland, though it could be part of a broader solution. In the short-term, achieving sustainable numbers of deer in Scotland will require a substantial increase in the number of deer culled and effective changes to the way deer management is incentivized, regulated, implemented, and monitored.

Ticks infesting humans and associated pathogens: a cross-sectional study in a 3-year period (2017-2019) in northwest Italy

BACKGROUND

Tick-borne diseases are common throughout Europe. Ticks transmit pathogens to the host while feeding and together with mosquitoes, they are major vectors of infectious agents worldwide. In recent years, there has been a marked increase in the incidence of tick-bite events and tick-borne disease in northwest Italy, but information on the prevalence of tick-borne pathogens in ticks removed from humans remains scarce. To fill this gap, we report here the prevalence of tick bites and tick-borne pathogens documented for humans in Piedmont, northwest Italy, in the 3-year period 2017-2019.

METHODS

Ticks attached to humans during 2017-2019 were collected from residents of urban and rural area by physicians and veterinarians working with local veterinary agencies. All ticks (n = 1290) were morphologically identified to the species level. A subset of ticks removed from children (age 0-18 years) and the elderly (> 70 years), both age groups considered to be at-risk populations, was screened by biomolecular analysis to detect pathogens (e.g. Rickettsia spp., Borrelia spp., Anaplasma spp.). Pathogen identity was confirmed by Sanger sequencing.

RESULTS

Ticks were taxonomically assigned to ten species of six genera (Amblyomma, Dermacentor, Haemaphysalis, Hyalomma, Ixodes and Rhipicephalus). Most belonged to the genus Ixodes: 1009 ticks (78.22%) were classified as Ixodes ricinus. A subset of 500 ticks collected from the two at-risk populations were subjected to PCR assay to determine the presence of Rickettsia spp., Borrelia spp., and Anaplasma spp. The overall prevalence of infection was 22.8% (n = 114; 95% confidence interval [CI]: 19.19-26.73%), meaning that at least one pathogen was detected: Rickettsia spp. (prevalence 15%, n = 76; 95% CI 12.17-18.65%); Borrelia spp. (prevalence 6.4%, n = 32; 95% CI 4.42-8.92%); and Anaplasma spp. (prevalence 1.2%, n = 6; 95% CI 0.44-2.6%).

CONCLUSIONS

Our data underline the importance of surveillance in the epidemiology of tick-borne diseases and the implementation of strategies to control tick infestation and associated pathogens.

The Impacts of Climate Change on Ticks and Tick-Borne Disease Risk

Ticks exist on all continents and carry more zoonotic pathogens than any other type of vector. Ticks spend most of their lives in the external environment away from the host and are thus expected to be affected by changes in climate. Most empirical and theoretical studies demonstrate or predict range shifts or increases in ticks and tick-borne diseases, but there can be a lot of heterogeneity in such predictions. Tick-borne disease systems are complex, and determining whether changes are due to climate change or other drivers can be difficult. Modeling studies can help tease apart and understand the roles of different drivers of change. Predictive models can also be invaluable in projecting changes according to different climate change scenarios. However, validating these models remains challenging, and estimating uncertainty in predictions is essential. Another focus for future research should be assessing the resilience of ticks and tick-borne pathogens to climate change.

Do bank voles (Myodes glareolus) trapped in live and lethal traps show differences in tick burden?

In studies assessing tick abundance, the use of live traps to capture and euthanize rodent hosts is a commonly used method to determine their burden. However, captive animals can experience debilitating or fatal capture stress as a result prior to collection. An alternative method is the use of lethal traps, but this can potentially lead to tick drop-off between the time of capture and collection. In this study, in order to determine whether subjecting animals to capture stress is inevitable, we tested the difference in sheep tick (Ixodes ricinus) larval burdens between bank voles (Myodes glareolus) captured alive and euthanized, and lethally trapped bank voles. During 2017 and 2018, 1318 bank voles were captured using live (Ugglan Special no. 2) and lethal (Rapp2 Mousetrap) traps during two consecutive years over three seasons in two locations in Norway. Voles captured alive would remain captive until euthanized, while lethally trapped voles were killed instantly upon capture. Log-linear models, accounting for overdispersion, were used to determine whether trap type was influencing observed tick burden. Bank voles captured in lethal traps carried 5.7% more larvae compared to euthanized voles captured in live traps, but this difference was not significant (p = 0.420). Males were overall captured 2.7 times more frequently than females, and the sex ratio was equal in both trap types. This study shows that the use of lethal traps to determine tick burden of rodents is sufficiently reliable, without having to subject animals to potentially lethal stress, hereby reducing some ethical concerns of animal suffering and the results thereof, without compromising accuracy. Lethal trapping is also often more economical and practical, further favoring this collection method.

Decline in Distribution and Abundance: Urban Hedgehogs under Pressure

Simple Summary

Hedgehogs have been found in higher densities in urban compared to rural areas. Recent dramatic declines in rural hedgehog numbers lead us to pose the question: how are hedgehogs faring in urban areas? In this study, we examined how hedgehog numbers have changed in the city of Zurich, Switzerland, in the last 25 years. We compared data collected through citizen science projects conducted in 1992 and 2016–2018, including: observations of hedgehogs, data from footprint tunnels, and capture-mark recapture studies. We found that hedgehog numbers have declined by 41%, from the former average of more than 30 individuals per km², in the last 25 years. In the same time span, hedgehogs have lost 18% of their former urban distribution. The reasons for this decline are still unknown. Intensification of urban buildup, reduction of green space quality, the use of pesticides, parasites, or diseases, as well as increasing numbers of badgers, which are hedgehog predators, in urban areas are discussed as potential causes. Worryingly, these results suggest that hedgehogs are now under increasing pressure not only in rural but also in urban areas, their former refuges.

Abstract

Increasing urbanization and densification are two of the largest global threats to biodiversity. However, certain species thrive in urban spaces. Hedgehogs Erinaceus europaeus have been found in higher densities in green areas of settlements as compared to rural spaces. With recent studies pointing to dramatically declining hedgehog numbers in rural areas, we pose the question: how do hedgehogs fare in urban spaces, and do these spaces act as refuges? In this study, recent (2016–2018) and past (1992) hedgehog abundance and distribution were compared across the city of Zurich, Switzerland using citizen science methods, including: footprint tunnels, capture-mark recapture, and incidental sightings. Our analyses revealed consistent negative trends: Overall hedgehog distribution decreased by 17.6% ± 4.7%, whereas abundance declined by 40.6% (mean abundance 32 vs. 19 hedgehogs/km², in past and recent time, respectively), with one study plot even showing a 91% decline in this period (78 vs. 7 hedgehogs/km², respectively). We discuss possible causes of this rapid decline: increased urban densification, reduction of insect biomass, and pesticide use, as well as the role of increasing populations of badgers (a hedgehog predator) and parasites or diseases. Our results suggest that hedgehogs are now under increasing pressure not only in rural but also in urban areas, their former refuges.

Distribution and prevalence of ticks and tick-borne disease on sheep and cattle farms in Great Britain

INTRODUCTION

The most abundant and widespread tick species in Great Britain, Ixodes ricinus, is responsible for the transmission of a range of pathogens that cause disease in livestock. Empirical data on tick distribution and prevalence are required to inform farm management strategies. However, such data are largely unavailable; previous surveys have been rare and are usually relatively localised.

METHODS

A retrospective questionnaire survey of farmers was used to assess the reported prevalence of ticks on livestock across Great Britain. Spatial scan statistics and kernel density maps were used to assess spatial clustering and identify areas of significantly elevated risk, independent of the underlying distribution of respondents. Logistic regression models were used to identify risk factors for tick presence.

RESULTS

Tick infection risk to livestock is shown to be spatially aggregated, with areas of significantly elevated risk in north Wales, northwest England and western Scotland. Overall, the prevalence of farms reporting tick presence was 13% for sheep farms and 6% for cattle farms, but in "hot spot" clusters prevalence ranged between 48-100%. The prevalence of farms reporting tick-borne disease overall was 6% for sheep and 2% for cattle, but on farms reporting ticks, prevalence was 44% and 33% for sheep and cattle farms, respectively. Upland farming, larger flock sizes, region and the presence of sheep on cattle farms were all significant risk factors for tick presence.

CONCLUSIONS

These data have important implications for assessing both the risk of tick-borne disease in livestock and optimising approaches to disease management. In particular, the study highlights the need for effective livestock tick control in upland regions and the southwest, and provides evidence for the importance of sheep as tick maintenance hosts.

Using imperfect data in predictive mapping of vectors: a regional example of Ixodes ricinus distribution

BACKGROUND

Knowledge of Ixodes ricinus tick distribution is critical for surveillance and risk management of transmissible tick-borne diseases such as Lyme borreliosis. However, as the ecology of I. ricinus is complex, and robust long-term geographically extensive distribution tick data are limited, mapping often relies on datasets collected for other purposes. We compared the modelled distributions derived from three datasets with information on I. ricinus distribution (quantitative I. ricinus count data from scientific surveys; I. ricinus presence-only data from public submissions; and a combined I. ricinus dataset from multiple sources) to assess which could be reliably used to inform Public Health strategy. The outputs also illustrate the strengths and limitations of these three types of data, which are commonly used in mapping tick distributions.

METHODS

Using the Integrated Nested Laplace algorithm we predicted I. ricinus abundance and presence-absence in Scotland and tested the robustness of the predictions, accounting for errors and uncertainty.

RESULTS

All models fitted the data well and the covariate predictors for I. ricinus distribution, i.e. deer presence, temperature, habitat, index of vegetation, were as expected. Differences in the spatial trend of I. ricinus distribution were evident between the three predictive maps. Uncertainties in the spatial models resulted from inherent characteristics of the datasets, particularly the number of data points, and coverage over the covariate range used in making the predictions.

CONCLUSIONS

Quantitative I. ricinus data from scientific surveys are usually considered to be gold standard data and we recommend their use where high data coverage can be achieved. However in this study their value was limited by poor data coverage. Combined datasets with I. ricinus distribution data from multiple sources are valuable in addressing issues of low coverage and this dataset produced the most appropriate map for national scale decision-making in Scotland. When mapping vector distributions for public-health decision making, model uncertainties and limitations of extrapolation need to be considered; these are often not included in published vector distribution maps. Further development of tools to better assess uncertainties in the models and predictions are necessary to allow more informed interpretation of distribution maps.

Impact of vertebrate communities on Ixodes ricinus-borne disease risk in forest areas

Background

The density of questing ticks infected with tick-borne pathogens is an important parameter that determines tick-borne disease risk. An important factor determining this density is the availability of different wildlife species as hosts for ticks and their pathogens. Here, we investigated how wildlife communities contribute to tick-borne disease risk. The density of Ixodes ricinus nymphs infected with Borrelia burgdorferi (sensu lato), Borrelia miyamotoi, Neoehrlichia mikurensis and Anaplasma phagocytophilum among 19 forest sites were correlated to the encounter probability of different vertebrate hosts, determined by encounter rates as measured by (camera) trapping and mathematical modeling.

Result

We found that the density of any tick life stage was proportional to the encounter probability of ungulates. Moreover, the density of nymphs decreased with the encounter probability of hare, rabbit and red fox. The density of nymphs infected with the transovarially-transmitted B. miyamotoi increased with the density of questing nymphs and the encounter probability of bank vole. The density of nymphs infected with all other pathogens increased with the encounter probability of competent hosts: bank vole for Borrelia afzelii and N. mikurensis, ungulates for A. phagocytophilum and blackbird for Borrelia garinii and Borrelia valaisiana. The negative relationship we found was a decrease in the density of nymphs infected with B. garinii and B. valaisiana with the encounter probability of wood mouse.

Conclusions

Only a few animal species drive the densities of infected nymphs in forested areas. There, foxes and leporids have negative effects on tick abundance, and consequently on the density of infected nymphs. The abundance of competent hosts generally drives the abundances of their tick-borne pathogen. A dilution effect was only observed for bird-associated Lyme spirochetes.

Sheep tick Ixodes ricinus management on Welsh hill farms of designated conservation importance: implications for nationally declining birds

Impacts of sheep ticks Ixodes ricinus on livestock, gamebirds and wildlife are of concern across Europe. The present study describes livestock and tick management by 36 farmers from three upland sites of conservation importance in North Wales, where farmers consider that ticks have increased during the last 25 years. Sheep, average densities of 2.0 animals per ha were treated with pour-on acaricides in spring, again in July, and also when removed from the moor in autumn. Given acaricide efficacy rates, sheep were susceptible to tick bites for half the period on the moor. Sheep from 17 farms were examined for ticks. Infestations were similar between farms and in relation to the acaricide used, averaging 9.3 ticks per sheep, although they were lower where the interval between successive acaricide treatments was shorter. Repeated sampling of sheep and red grouse chicks showed no annual difference in tick burdens on grouse chicks, which averaged 6.2 ticks per chick, although there were three-fold fewer ticks on sheep in 2018 than in previous years. Tick bite rates on sheep and grouse were higher than elsewhere in the U.K. Most farmers interviewed would aim to improve their tick management using longer-lasting acaricides and treating sheep more frequently, although they would need advice and financial help, which is currently unavailable via Government funded agri-environment schemes.

The importance of wildlife in the ecology and epidemiology of the TBE virus in Sweden: incidence of human TBE correlates with abundance of deer and hares

Background

Tick-borne encephalitis (TBE) is one tick-transmitted disease where the human incidence has increased in some European regions during the last two decades. We aim to find the most important factors causing the increasing incidence of human TBE in Sweden. Based on a review of published data we presume that certain temperature-related variables and the population densities of transmission hosts, i.e. small mammals, and of primary tick maintenance hosts, i.e. cervids and lagomorphs, of the TBE virus vector Ixodes ricinus, are among the potentially most important factors affecting the TBE incidence. Therefore, we compare hunting data of the major tick maintenance hosts and two of their important predators, and four climatic variables with the annual numbers of human cases of neuroinvasive TBE. Data for six Swedish regions where human TBE incidence is high or has recently increased are examined by a time-series analysis. Results from the six regions are combined using a meta-analytical method.

Results

With a one-year time lag, the roe deer (Capreolus capreolus), red deer (Cervus elaphus), mountain hare (Lepus timidus) and European hare (Lepus europaeus) showed positive covariance; the Eurasian elk (moose, Alces alces) and fallow deer (Dama dama) negative covariance; whereas the wild boar (Sus scrofa), lynx (Lynx lynx), red fox (Vulpes vulpes) and the four climate parameters showed no significant covariance with TBE incidence. All game species combined showed positive covariance.

Conclusions

The epidemiology of TBE varies with time and geography and depends on numerous factors, i.a. climate, virus genotypes, and densities of vectors, tick maintenance hosts and transmission hosts. This study suggests that the increased availability of deer to I. ricinus over large areas of potential tick habitats in southern Sweden increased the density and range of I. ricinus and created new TBEV foci, which resulted in increased incidence of human TBE. New foci may be established by TBE virus-infected birds, or by birds or migrating mammals infested with TBEV-infected ticks. Generally, persistence of TBE virus foci appears to require presence of transmission-competent small mammals, especially mice (Apodemus spp.) or bank voles (Myodes glareolus).

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3057-4) contains supplementary material, which is available to authorized users.

The effects of acaricide treatment of sheep on red grouse Lagopus lagopus scotica tick burdens and productivity in a multi-host system

Ixodes ricinus (Ixodida: Ixodidae) ticks are of economic and pathogenic importance across Europe. Within the uplands of the U.K., management to reduce ticks is undertaken to benefit red grouse Lagopus lagopus scotica (Galliformes: Phasianidae). Management strategies focus on the acaricide treatment of domestic sheep Ovis aries (Artiodactyla: Bovidae), but the effectiveness of this is less certain in the presence of wild hosts, particularly red deer Cervus elaphus (Artiodactyla: Cervidae) and mountain hare Lepus timidus (Lagomorpha: Leporidae). This study examines the effects of sheep management on grouse tick burdens and productivity using sites with a range of wild host densities. Sites at which applications of acaricide were more frequent had lower tick burdens; this relationship was similar on sites with a range of deer densities. However, no direct link was detected between acaricide treatment interval and grouse productivity. Sites with higher deer densities had higher grouse tick burdens and lower productivity [mean ± standard error (SE) young : adult ratio: 1.2 ± 0.2] compared with sites with lower deer densities (mean ± SE young : adult ratio: 1.8 ± 0.1). Sites with higher grouse brood sizes and higher proportions of hens with broods were also those with higher mountain hare abundance indices. This study highlights the importance of the frequent treatment of sheep with acaricide to reduce tick burdens on grouse, even in the presence of wild hosts.

Surveillance of British ticks: An overview of species records, host associations, and new records of Ixodes ricinus distribution

Public Health England's passive Tick Surveillance Scheme (TSS) records the distribution, seasonality and host associations of ticks submitted from across the United Kingdom (UK), and helps to inform the UK government on emerging tick-borne disease risks. Here we summarise data collected through surveillance during 2010-2016, and compare with previous TSS data from 2005 to 2009, particularly in relation to the primary Lyme borreliosis vector Ixodes ricinus. 4173 records were submitted, constituting >14,000 ticks; 97% were endemic tick records (13,833 ticks of 11 species), with an additional 97 records of imported ticks (438 ticks of 17 species). Tick submissions were mainly from veterinary professionals (n = 1954; 46.8%) and members of the public and amateur entomologists (n = 1600; 38.3%), as well as from academic institutions (n = 249; 6.0%), wildlife groups (n = 239; 5.7%) and health professionals (n = 131; 3.1%). The most commonly reported hosts of endemic ticks were dogs (n = 1593; 39.1% of all records), humans (n = 835; 20.5%) and cats (n = 569; 14%). New host associations were recorded for a number of tick species. Ixodes ricinus was the most frequently recorded endemic tick species (n = 2413; 59.2% of all records), followed by I. hexagonus (n = 1355; 33.2%), I. canisuga (n = 132; 3.2%) and I. frontalis (n = 56; 1.4%), with other species each making up <1% total records. 81% of I. ricinus recorded from humans were nymphs, whereas 93.4% of I. ricinus from companion animals were adults. Recent TSS records of I. ricinus in the UK add a considerable amount of new presence data for this species, particularly in the southern regions of England, and confirm that this species is widespread across the UK. The scheme remains a valuable method of collecting continuous national distribution data on ticks from a variety of host species.

Europe-Wide Meta-Analysis of Borrelia burgdorferi Sensu Lato Prevalence in Questing Ixodes ricinus Ticks

Lyme borreliosis is the most common zoonotic disease transmitted by ticks in Europe and North America. Despite having multiple tick vectors, the causative agent, Borrelia burgdorferisensu lato, is vectored mainly by Ixodes ricinus in Europe. In the present study, we aimed to review and summarize the existing data published from 2010 to 2016 concerning the prevalence of B. burgdorferi sensu lato spirochetes in questing I. ricinus ticks. The primary focus was to evaluate the infection rate of these bacteria in ticks, accounting for tick stage, adult tick gender, region, and detection method, as well as to investigate any changes in prevalence over time. The data obtained were compared to the findings of a previous metastudy. The literature search identified data from 23 countries, with 115,028 ticks, in total, inspected for infection with B. burgdorferi sensu lato We showed that the infection rate was significantly higher in adults than in nymphs and in females than in males. We found significant differences between European regions, with the highest infection rates in Central Europe. The most common genospecies were B. afzelii and B. garinii, despite a negative correlation of their prevalence rates. No statistically significant differences were found among the prevalence rates determined by conventional PCR, nested PCR, and real-time PCR.IMPORTANCEBorrelia burgdorferisensu lato is a pathogenic bacterium whose clinical manifestations are associated with Lyme borreliosis. This vector-borne disease is a major public health concern in Europe and North America and may lead to severe arthritic, cardiovascular, and neurological complications if left untreated. Although pathogen prevalence is considered an important predictor of infection risk, solitary isolated data have only limited value. Here we provide summarized information about the prevalence of B. burgdorferi sensu lato spirochetes among host-seeking Ixodes ricinus ticks, the principal tick vector of borreliae in Europe. We compare the new results with previously published data in order to evaluate any changing trends in tick infection.

The passive surveillance of ticks using companion animal electronic health records

Ticks represent a large global reservoir of zoonotic disease. Current surveillance systems can be time and labour intensive. We propose that the passive surveillance of companion animal electronic health records (EHRs) could provide a novel methodology for describing temporal and spatial tick activity. A total of 16 58 857 EHRs were collected over a 2-year period (31 March 2014 and 29 May 2016) from companion animals attending a large sentinel network of 192 veterinary clinics across Great Britain (the Small Animal Veterinary Surveillance Network - SAVSNET). In total, 2180 EHRs were identified where a tick was recorded on an animal. The relative risk of dogs presenting with a tick compared with cats was 0·73 (95% confidence intervals 0·67-0·80). The highest number of tick records were in the south central regions of England. The presence of ticks showed marked seasonality with summer peaks, and a secondary smaller peak in autumn for cats; ticks were still being found throughout most of Great Britain during the winter. This suggests that passive surveillance of companion animal EHRs can describe tick activity temporally and spatially in a large cohort of veterinary clinics across Great Britain. These results and methodology could help inform veterinary and public health messages as well as increase awareness of ticks and tick-borne diseases in the general population.

Can acaricide-impregnated leg bands fitted to female red grouse reduce sheep tick parasitization of chicks and increase chick survival?

In parts of northern England, North Wales and the Scottish Highlands, increasing numbers of sheep ticks Ixodes ricinus (Ixodida: Ixodidae), and the louping ill virus they can carry, are considered to be important factors that reduce red grouse Lagopus lagopus scotica productivity. The present study tested this hypothesis by fitting adult female grouse with leg bands impregnated with the acaricide cypermethrin to experimentally control ticks on their chicks on two managed grouse moors in northeast Scotland. The chicks of females fitted with acaricide leg bands showed reduced tick infestations and improved survival in one of the two study years, relative to chicks of control females. Acaricide leg bands constitute a potential management technique that may be adopted by grouse moor managers in circumstances of high tick infestations on grouse chicks.

Ticks infesting domestic dogs in the UK: a large-scale surveillance programme

Background

Recent changes in the distribution of tick vectors and the incidence of tick-borne disease, driven variously by factors such as climate change, habitat modification, increasing host abundance and the increased movement of people and animals, highlight the importance of ongoing, active surveillance. This paper documents the results of a large-scale survey of tick abundance on dogs presented to veterinary practices in the UK, using a participatory approach that allows relatively cost- and time-effective extensive data collection.

Methods

Over a period of 16 weeks (April–July 2015), 1094 veterinary practices were recruited to monitor tick attachment to dogs and provided with a tick collection and submission protocol. Recruitment was encouraged through a national publicity and communication initiative. Participating practices were asked to select five dogs at random each week and undertake a thorough, standardized examination of each dog for ticks. The clinical history and any ticks were then sent to the investigators for identification.

Results

A total of 12,000 and 96 dogs were examined and 6555 tick samples from infested dogs were received. Ixodes ricinus (Linnaeus) was identified on 5265 dogs (89 %), Ixodes hexagonus Leach on 577 (9.8 %) and Ixodes canisuga Johnston on 46 (0.8 %). Ten dogs had Dermacentor reticulatus (Fabricius), one had Dermacentor variabilis (Say), three had Haemaphysalis punctata Canesteini & Fanzago and 13 had Rhipicephalus sanguineus Latreille. 640 ticks were too damaged for identification. All the R. sanguineus and the single D. variabilis were on dogs with a recent history of travel outside the UK. The overall prevalence of tick attachment was 30 % (range 28–32 %). The relatively high prevalence recorded is likely to have been inflated by the method of participant recruitment.

Conclusion

The data presented provide a comprehensive spatial understanding of tick distribution and species abundance in the UK against which future changes can be compared. Relative prevalence maps show the highest rates in Scotland and south west England providing a valuable guide to tick-bite risk in the UK.

Observations on changes in abundance of questing Ixodes ricinus, castor bean tick, over a 35-year period in the eastern part of its range (Russia, Tula region)

Ixodes ricinus (Acari: Ixodidae) L. transmit a wide variety of pathogens to vertebrates including viruses, bacteria and protozoa. Understanding of the epidemiology of tick-borne infections requires basic knowledge of the regional and local factors influencing tick population dynamics. The present study describes the results of monitoring of a questing I. ricinus population, conducted over 35 years (1977-2011) in the eastern, poorly studied part of its range (Russia, Tula region). We have found that the multiannual average abundance of ticks is small and varies depending on the biotope and degree of urban transformation. Tick abundance for the first 14 years of observations (1977-1990) was at the lower limit of the sensitivity of our methods throughout the study area (0.1-0.9 specimens per 1-km transect). In the following 21 years (1991-2011), a manifold increase in abundance was observed, which reached 18.1 ± 1.8 individuals per 1-km transect in moist floodplain terraces, and 4.8 ± 0.9 in xerophylic hill woods. Long-term growth of tick abundance occurred in spite of a relatively constant abundance of small mammals and only minor fluctuations in the abundance of large wild animals. Climate and anthropogenic changes appear to be the main contributors to increased abundance of the tick.

Threat of attacks of Ixodes ricinus ticks (Ixodida: Ixodidae) and Lyme borreliosis within urban heat islands in south-western Poland

Background

The increased incidence of Lyme disease in Europe necessitates permanent monitoring of the occurrence and activity of its vector. Therefore, in this study, we have investigated the presence and seasonal activity of Ixodes ricinus ticks in various habitats of a large industrial region in south-western Poland in correlation with environmental factors present in urban heat islands. Additionally, the risk of borreliosis in this part of Poland has been assessed.

Methods

The investigations were carried out at two-week intervals between April and October 2001 and 2002. Ticks were collected from four localities in Upper Silesia, i.e. in a city park (CH), on the outskirts of two large cities (KO, MI), and in a forest (KL). We analysed the impact of temperature and humidity measured during the collection period in the I. ricinus habitats, the climatic conditions prevailing in the study area, and the degree of environmental contamination on the abundance and activity of these ticks in the respective sites. The degree of borreliosis risk in the region was determined on the basis of the results of research on the prevalence of Borrelia burgdorferi s.l. in ticks and reports from sanitary-epidemiological stations.

Results

In total, 2061 I. ricinus ticks, including 606 nymphs and 1455 adults, were collected in the study area. The number and activity of the ticks varied during the collection in the different sites. In the urban locality CH, tick abundance was the lowest (455 throughout the investigation period), and the seasonal activity of females was unimodal and persisted for as long as 4 months. In the suburban localities KO and MI, tick abundance was higher (485 and 481 specimens, respectively) and the activity of females was unimodal. The highest abundance (640 ticks) and a bimodal pattern of female activity were reported from the forest locality KL. In all the localities, the activity of nymphs was unimodal. Humidity was found to be a factor influencing I. ricinus abundance and activity, whereas temperature did not affect their number and behaviour significantly. The climate parameters within the urban heat islands noted during the investigations contributed to dispersal of dust and gas pollutants. The analysis of the data reveals that there is a risk of borreliosis in the entire study area; however, it is higher in the urban localities than in the suburban sites.

Conclusions

Environmental conditions (habitat, climate, and dust and gas pollution) prevailing within urban heat islands may exert an impact on tick abundance and activity and the prevalence of Lyme disease in the study area. The greatest effect of the environmental factors on ticks was found in the city park, where the risk of human infection with B. burgdorferi s.l. spirochetes is the highest as well.

Ticks and associated diseases: a retrospective review

This is a retrospective review of contributions to the understanding of ticks and associated diseases published in Medical and Veterinary Entomology since its first issue. It highlights the large and significant changes in the style and conduct of this field over the last 25 years. The selected papers refer to disease-related categories of host immunity to ticks, population dynamics, pathogen transmission and tick control.

A look into the Medical and Veterinary Entomology crystal ball

Medical and Veterinary Entomology (MVE) represents a leading periodical in its field and covers many aspects of the biology and control of insects, ticks, mites and other arthropods of medical and veterinary importance. Since the first issue of the journal, researchers working in both developed and developing countries have published in MVE, with direct impact on current knowledge in the field. An increasing number of articles dealing with the epidemiology and transmission of vector-borne pathogens have been published in MVE, reflecting rapid changes in vector distribution, pathogen transmission and host-arthropod interactions. This article represents a gaze into the crystal ball in which we identify areas of increasing interest, discuss the main changes that have occurred in the epidemiology of parasitic arthropods since the first issue of MVE, and predict the principal scientific topics that might arise in the next 25 years for scientists working in medical and veterinary entomology.

Ticks infesting humans in Italy and associated pathogens

Background

Ticks may transmit a large variety of pathogens, which cause illnesses in animals and humans, commonly referred to as to tick-borne diseases (TBDs). The incidence of human TBDs in Italy is underestimated because of poor surveillance and the scant amount of studies available.

Methods

Samples (n = 561) were collected from humans in four main geographical areas of Italy (i.e., northwestern, northeastern, southern Italy, and Sicily), which represent a variety of environments. After being morphologically identified, ticks were molecularly tested with selected protocols for the presence of pathogens of the genera Rickettsia, Babesia, Theileria, Candidatus Neoehrlichia mikurensis, Borrelia and Anaplasma.

Results

Ticks belonged to 16 species of the genera Argas, Dermacentor, Haemaphysalis, Hyalomma, Ixodes and Rhipicephalus, with Ixodes ricinus (59.5%) being the species most frequently retrieved, followed by Rhipicephalus sanguineus sensu lato (21.4%). Nymphs were the life stage most frequently retrieved (41%), followed by adult females (34.6%). The overall positivity to any pathogen detected was 18%. Detected microorganisms were Rickettsia spp. (17.0%), Anaplasma phagocytophilum (0.8%), Borrelia afzelii (0.5%), Borrelia valaisiana (0.3%), C. N. mikurensis (0.5%) and Babesia venatorum (0.6%).

Conclusions

Results indicate that people living in the Italian peninsula are at risk of being bitten by different tick species, which may transmit a plethora of TBD causing pathogens and that co-infections may also occur.

Changes in the activity of adult stages of Dermacentor reticulatus (Ixodida: Amblyommidae) induced by weather factors in eastern Poland

Background

The host-seeking activity in Dermacentor reticulatus ticks undergoes rhythmical changes correlated with environmental conditions. Therefore, this study is focused on investigating the activity of adult stages of the species during weather changes occurring in winter months in eastern Poland, i.e. a period of tick diapause.

Methods

D. reticulatus ticks were collected in a meadow ecosystem near Lublin (eastern Poland, 51°36'N, 22°58'E) between the third decade of November 2011 and the third decade of January 2012. During each collection, temperature and humidity were measured at the soil surface and at a height of 25 cm and the differences (delta) in the parameters between the two measurement points were calculated.

Results

During one hour of our observation, from 0 to 42 specimens were collected, with the greatest numbers (25-40 specimens) between late November and mid- December. The activity of adult D. reticulatus (females and males in total) depended on soil and air temperature (r = -0.6986, p < 0.05). Soil and air humidity did not exert an impact on the questing behaviour of adult stages. In turn, the greater the moisture delta between these two measurement points was, the greater the activity of the adult tick stages was observed.

Our investigations have demonstrated differences in the questing behaviour between D. reticulatus females and males correlated with environmental conditions. The temperatures of soil and air increased the migratory activity in females but did not affect migration of male ticks. In turn, the deltas of temperatures (r = -0.6986, p < 0.05) and humidity (r = 0.6829, p < 0.05) did not have a statistically significant effect on stimulation of female activity but they induced significant changes on the behaviour of males, for which we found a highly negative correlation between the number of active specimens and the temperature delta (r = -0.7276, p < 0.05) and a highly positive correlation with the humidity delta (r = 0.8199, p < 0.01).

Conclusions

Weather changes can be accompanied by activity of adult D. reticulatus even in their winter diapause period. Therefore, there is an increased threat to human and animal health posed by tick-borne diseases.

Multilocus sequence typing using mitochondrial genes (mtMLST) reveals geographic population structure of Ixodes ricinus ticks

The hard tick Ixodes ricinus is the principal vector of Lyme borreliosis (LB) group spirochaetes in Europe, but it also transmits a large number of other microbial pathogens that are of importance to animal and human health. Here, we characterise geographically distinct populations of this important ectoparasite based on multilocus sequence typing (MLST) of multiple mitochondrial (mt) genes (mtMLST). Internal fragments of approximately 500 bp were amplified and sequenced for 6 protein-encoding and ribosomal genes (atp6, coi, coii, coiii, cytB, and 12s). The samples analysed consisted of 506 questing nymphs collected in Britain and Latvia in 2006-2008 and in Latvia in 2002. Although little genetic structure has previously been observed in I. ricinus ticks among Europe, our data could clearly differentiate these 2 populations. Here, we argue that this novel scheme provides additional phylogenetic resolution which is important for understanding the genetic and geographic structure of I. ricinus populations. This in turn will benefit monitoring and management of tick-borne diseases.

Tick infestation risk for dogs in a peri-urban park

BACKGROUND

Increases in the abundance and distribution of ticks and tick borne disease (TBD) within Europe have been reported extensively over the last 10-20 years. Changes in climate, habitat management, economic patterns and changes in the abundance of hosts, particularly deer, may all have influenced this change to varying extents. Increasing abundances of tick populations in urban and peri-urban environments, such as parks, are of particular concern. In these sites, suitable habitat, wildlife hosts, tick populations, people and their pets may be brought into close proximity and hence may provide foci for tick infestation and, ultimately, disease transmission.

METHODS

The distribution and abundance of ticks were examined in an intensively used, peri-urban park. First the seasonal and spatial distribution and abundance of ticks in various habitat types were quantified by blanket dragging. Then the pattern of pet dog movement in the park was mapped by attaching GPS recorders to the collars of dogs brought to the park for exercise, allowing their walking routes to be tracked. Information about the dog, its park use and its history of tick attachment were obtained from the dog-owners.

RESULTS

Ticks were found predominantly in woodland, woodland edge and deer park areas and were least abundant in mown grassland. Tick infestation of dogs was a relatively frequent occurrence with, on average, one case of tick attachment reported per year for a dog walked once per week, but for some dogs walked daily, infestation 4-5 times per week was reported. All dogs appeared to be at equal risk, regardless of walk route or duration and infestation was primarily influenced by the frequency of exposure.

CONCLUSIONS

In peri-urban green spaces, tick-biting risk for dogs may be high and here was shown to be related primarily to exposure frequency. While tick-biting is of direct veterinary importance for dogs, dogs also represent useful sentinels for human tick-exposure.

Seroprevalence of Borrelia burgdorferi sensu lato in roe deer (Capreolus capreolus) from northwestern Spain

In the present study, the seroprevalence of Borrelia burgdorferi sensu lato in roe deer in relation to different parameters in northwestern Spain was investigated. A total of 154 roe deer hunted between April 2007 and October 2008 from different localities of Galicia (northwest Spain) were examined. From each animal, a blood sample and all attached ticks found were collected. All the specimens for tick stages (larva, nymph, and adult) were speciated based on reference keys. Antibodies against B. burgdorferi were detected by indirect immunofluorescence (titer > or = 1:64). The percentage of roe deer seropositive for B. burgdorferi was 68.8% (106/ 154), of which 88.7% (94/106) were parasitized by ticks. Ixodes ricinus was the only species identified and was detected in 83.1% of roe deer with a mean (standard deviation [SD]) intensity of 46 +/- 47 ticks. Individual host characteristics such as age or sex did not have any effect on the prevalence of B. burgdorferi, but significant seasonal variation was observed, with higher prevalences in April-July than in August-October. Antibodies against B. burgdorferi were related to the presence of ticks. When analyzing all the factors together, the total number of ticks parasitizing roe deer was found as the most influential factor on B. burgdorferi prevalence. The results of this study have shown that roe deer in the northwest of Spain are highly exposed to B. burgdorferi and that exposure is related to the presence of I. ricinus.

A model to test how ticks and louping ill virus can be controlled by treating red grouse with acaricide

Ticks are the most important vectors of disease-causing pathogens in Europe. In the U.K., Ixodes ricinus L. (Ixodida: Ixodidae) transmits louping ill virus (LIV; Flaviviridae), which kills livestock and red grouse, Lagopus lagopus scoticus Lath. (Galliformes: Phasianidae), a valuable game bird. Tick burdens on grouse have been increasing. One novel method to reduce ticks and LIV in grouse may be acaricide treatment. Here, we use a mathematical model parameterized with empirical data to investigate how the acaricide treatment of grouse might theoretically control ticks and LIV in grouse. Assuming a situation in which ticks and LIV impact on the grouse population, the model predicts that grouse density will depend on deer density because deer maintain the tick population. In low deer densities, no acaricide treatment is predicted to be necessary because abundances of grouse will be high. However, at higher deer densities, the model predicts that grouse densities will increase only if high numbers of grouse are treated, and the efficacy of acaricide is high and lasts 20 weeks. The qualitative model predictions may help to guide decisions on whether to treat grouse or cull deer depending on deer densities and how many grouse can be treated. The model is discussed in terms of practical management implications.

Distribution of Borrelia burgdorferi sensu lato in Ixodes ricinus populations across central Britain

Lyme borreliosis is rapidly emerging in the United Kingdom, with over 1000 cases per annum now reported. Lyme borreliosis is caused by the Borrelia burgdorferi sensu lato (s.l.) group of spirochetes, which are transmitted by ixodid ticks. In the United Kingdom, Ixodes ricinus is recognized as the principal vector of the spirochetes, and this tick species is widely distributed across the country. However, as yet, it is unclear whether the distribution of B. burgdorferi essentially mirrors that of its vector, or if there are marked differences between the 2. The aim of this survey was to investigate the prevalence of B. burgdorferi in I. ricinus populations across northern England, north Wales, and the Scottish Border region. We surveyed for questing I. ricinus nymphs and adults at 17 sites, encountering ticks at 12. At 8 sites, large numbers (>160) ticks were collected, and at 3 of these sites B. burgdorferi infection prevalence was significantly higher (>7.5%) than the other 5 (<1.0%). Habitat type was associated with B. burgdorferi prevalence, with ticks from deciduous and mixed woodland being significantly more likely to be infected than those from other habitat types. Identification of infecting Borrelia species indicated that Borrelia valaisiana was the most common and widespread species encountered. B. garinii was common at sites where infection prevalence was high, and B. afzelii was also occasionally encountered at these sites. The survey revealed a surprisingly uneven distribution of B. burgdorferi s.l. across the region, thereby indicating that the presence of ticks does not necessarily mean the presence of the pathogen. Indeed, the spirochete appears to be absent or very rare at some sites where ticks are abundant.

Driving forces for changes in geographical distribution of Ixodes ricinus ticks in Europe

Many factors are involved in determining the latitudinal and altitudinal spread of the important tick vector Ixodes ricinus (Acari: Ixodidae) in Europe, as well as in changes in the distribution within its prior endemic zones. This paper builds on published literature and unpublished expert opinion from the VBORNET network with the aim of reviewing the evidence for these changes in Europe and discusses the many climatic, ecological, landscape and anthropogenic drivers. These can be divided into those directly related to climatic change, contributing to an expansion in the tick's geographic range at extremes of altitude in central Europe, and at extremes of latitude in Scandinavia; those related to changes in the distribution of tick hosts, particularly roe deer and other cervids; other ecological changes such as habitat connectivity and changes in land management; and finally, anthropogenically induced changes. These factors are strongly interlinked and often not well quantified. Although a change in climate plays an important role in certain geographic regions, for much of Europe it is non-climatic factors that are becoming increasingly important. How we manage habitats on a landscape scale, and the changes in the distribution and abundance of tick hosts are important considerations during our assessment and management of the public health risks associated with ticks and tick-borne disease issues in 21(st) century Europe. Better understanding and mapping of the spread of I. ricinus (and changes in its abundance) is, however, essential to assess the risk of the spread of infections transmitted by this vector species. Enhanced tick surveillance with harmonized approaches for comparison of data enabling the follow-up of trends at EU level will improve the messages on risk related to tick-borne diseases to policy makers, other stake holders and to the general public.

Abundance of Ixodes ricinus and prevalence of Borrelia burgdorferi s.l. in the nature reserve Siebengebirge, Germany, in comparison to three former studies from 1978 onwards

BACKGROUND

During the last decades, population densities of Ixodes ricinus and prevalences of Borrelia burgdorferi s.l. have increased in different regions in Europe. In the present study, we determined tick abundance and the prevalence of different Borrelia genospecies in ticks from three sites in the Siebengebirge, Germany, which were already examined in the years 1987, 1989, 2001 and 2003. Data from all investigations were compared.

METHODS

In 2007 and 2008, host-seeking I. ricinus were collected by monthly blanket dragging at three distinct vegetation sites in the Siebengebirge, a nature reserve and a well visited local recreation area near Bonn, Germany. In both years, 702 ticks were tested for B. burgdorferi s.l. DNA by nested PCR, and 249 tick samples positive for Borrelia were further genotyped by reverse line blotting.

RESULTS

A total of 1046 and 1591 I. ricinus were collected in 2007 and 2008, respectively. In comparison to previous studies at these sites, the densities at all sites increased from 1987/89 and/or from 2003 until 2008. Tick densities and Borrelia prevalences in 2007 and 2008, respectively, were not correlated for all sites and both years. Overall, Borrelia prevalence of all ticks decreased significantly from 2007 (19.5%) to 2008 (16.5%), thus reaching the same level as in 2001 two times higher than in 1987/89 (7.6%). Since 2001, single infections with a Borrelia genospecies predominated in all collections, but the number of multiple infections increased, and in 2007, for the first time, triple Borrelia infections occurred. Prevalences of Borrelia genospecies differed considerably between the three sites, but B. garinii or B. afzelii were always the most dominant genospecies. B. lusitaniae was detected for the first time in the Siebengebirge, also in co-infections with B. garinii or B. valaisiana.

CONCLUSIONS

Over the last two centuries tick densities have changed in the Siebengebirge at sites that remained unchanged by human activity since they belong to a nature reserve. Abiotic and biotic conditions most likely favored the host-seeking activity of I. ricinus and the increase of multiple Borrelia infections in ticks. These changes have led to a potential higher risk of humans and animals to be infected with Lyme borreliosis.

The effect of deer management on the abundance of Ixodes ricinus in Scotland

The management of wildlife hosts for controlling parasites and disease has a history of mixed success. Deer can be important hosts for ticks, such as Ixodes ricinus, which is the primary vector of disease-causing zoonotic pathogens in Europe. Deer are generally managed by culling and fencing for forestry protection, habitat conservation, and commercial hunting, and in this study we test whether these deer management methods can be useful for controlling ticks, with implications for tick-borne pathogens. At different spatial scales and habitats we tested the hypotheses that tick abundance is reduced by (1) culling deer and (2) deer exclusion using fencing. We compared abundance indices of hosts and questing I. ricinus nymphs using a combination of small-scale fencing experiments on moorland, a large-scale natural experiment of fenced and unfenced pairs of forests, and cross-sectional surveys of forest and moorland areas with varying deer densities. As predicted, areas with fewer deer had fewer ticks, and fenced exclosures had dramatically fewer ticks in both large-scale forest and small-scale moorland plots. Fencing and reducing deer density were also associated with higher ground vegetation. The implications of these results on other hosts, pathogen prevalence, and disease risk are discussed. This study provides evidence of how traditional management methods of a keystone species can reduce a generalist parasite, with implications for disease risk mitigation.

Modelling bovine babesiosis: a tool to simulate scenarios for pathogen spread and to test control measures for the disease

Tick-borne diseases are of increasing concern in many countries, particularly as a consequence of changes in land use and climate. Ticks are vectors of numerous pathogens (viruses, bacteria, protozoa) that can be harmful to humans and animals. In the context of animal health, bovine babesiosis poses a recurrent threat to cattle herds. In this study, we use a modeling approach to investigate the spread of babesiosis and evaluate control measures. A previously developed tick population dynamics model (here, Ixodes ricinus) is coupled with a pathogen spread model (here, the protozoan Babesia divergens), which describes pathogen spread in a dairy herd through the following processes: transmission, acquisition, transovarial transmission, transstadial persistence, and clearance of the pathogen. An assessment of the simulated B. divergens prevalence levels in ticks and cattle in the context of existing knowledge and data suggested that the model provides a realistic representation of pathogen spread. The model was then used to evaluate the influence of host density and the effect of acaricides on B. divergens prevalence in cattle. Increasing deer density results in an increase in prevalence in cattle whereas increasing cattle stocking rate results in a slight decrease. A potential increase in deer density would thus have an amplification effect on disease spread due to the increase in the number of infected ticks. Regular use of acaricides produces a reduction in pathogen prevalence in cattle. This model could be adapted to other tick-borne diseases.

Changes in the geographical distribution and abundance of the tick Ixodes ricinus during the past 30 years in Sweden

Background

Ixodes ricinus is the main vector in Europe of human-pathogenic Lyme borreliosis (LB) spirochaetes, the tick-borne encephalitis virus (TBEV) and other pathogens of humans and domesticated mammals. The results of a previous 1994 questionnaire, directed at people living in Central and North Sweden (Svealand and Norrland) and aiming to gather information about tick exposure for humans and domestic animals, suggested that Ixodes ricinus ticks had become more widespread in Central Sweden and the southern part of North Sweden from the early 1980s to the early 1990s. To investigate whether the expansion of the tick's northern geographical range and the increasing abundance of ticks in Sweden were still occurring, in 2009 we performed a follow-up survey 16 years after the initial study.

Methods

A questionnaire similar to the one used in the 1994 study was published in Swedish magazines aimed at dog owners, home owners, and hunters. The questionnaire was published together with a popular science article about the tick's biology and role as a pathogen vector in Sweden. The magazines were selected to get information from people familiar with ticks and who spend time in areas where ticks might be present.

Results

Analyses of data from both surveys revealed that during the near 30-year period from the early 1980s to 2008, I. ricinus has expanded its distribution range northwards. In the early 1990s ticks were found in new areas along the northern coastline of the Baltic Sea, while in the 2009 study, ticks were reported for the first time from many locations in North Sweden. This included locations as far north as 66°N and places in the interior part of North Sweden. During this 16-year period the tick's range in Sweden was estimated to have increased by 9.9%. Most of the range expansion occurred in North Sweden (north of 60°N) where the tick's coverage area doubled from 12.5% in the early 1990s to 26.8% in 2008. Moreover, according to the respondents, the abundance of ticks had increased markedly in LB- and TBE-endemic areas in South (Götaland) and Central Sweden.

Conclusions

The results suggest that I. ricinus has expanded its range in North Sweden and has become distinctly more abundant in Central and South Sweden during the last three decades. However, in the northern mountain region I. ricinus is still absent. The increased abundance of the tick can be explained by two main factors: First, the high availability of large numbers of important tick maintenance hosts, i.e., cervids, particularly roe deer (Capreolus capreolus) during the last three decades. Second, a warmer climate with milder winters and a prolonged growing season that permits greater survival and proliferation over a larger geographical area of both the tick itself and deer. High reproductive potential of roe deer, high tick infestation rate and the tendency of roe deer to disperse great distances may explain the range expansion of I. ricinus and particularly the appearance of new TBEV foci far away from old TBEV-endemic localities. The geographical presence of LB in Sweden corresponds to the distribution of I. ricinus. Thus, LB is now an emerging disease risk in many parts of North Sweden. Unless countermeasures are undertaken to keep the deer populations, particularly C. capreolus and Dama dama, at the relatively low levels that prevailed before the late 1970s - especially in and around urban areas where human population density is high - by e.g. reduced hunting of red fox (Vulpes vulpes) and lynx (Lynx lynx), the incidences of human LB and TBE are expected to continue to be high or even to increase in Sweden in coming decades.

Prevalence, distribution and risk associated with tick infestation of dogs in Great Britain

Current concerns over the potential impacts of climate change and the increased movement between countries of people and companion animals on the distribution of ectoparasites, highlight the need for accurate understanding of existing prevalence patterns. Without these future changes will not be detected. Here, the distribution and prevalence of tick infestations of domestic dogs in Great Britain were examined. A total of 173 veterinary practices were recruited to monitor tick attachment to dogs in their local areas between March and October 2009. Practices selected five dogs at random each week from those brought to the surgery and undertook a thorough, standardized examination for ticks. Each veterinary practice participated for 3 months before being replaced. Any ticks identified were collected and a sample sent to the investigators for identification, along with a clinical history of the dog. A total of 3534 dogs were examined; 810 dogs were found to be carrying at least one tick. Ixodes ricinus (Linnaeus) (Acari: Ixodidae) was identified in 72.1% of cases, Ixodes hexagonus Leach in 21.7% and Ixodes canisuga Johnston in 5.6% of cases. Five samples of Dermacentor reticulatus (Fabricius) (Acari: Ixodidae) were also found, adding to the growing evidence that an established population of D. reticulatus now exists in south-eastern England. Almost all the ticks found were adults. Overall, 19.2% of the veterinary practices reported no tick detections, 50% reported that ≥14.9% of the dogs seen were infested and 14.6% reported that >50% of the dogs inspected carried ticks. The estimated incidence of tick attachment was 0.013 per day in March (lowest) and 0.096 per day in June (highest). A number of risk factors affected the likelihood of tick attachment on dogs. Gundog, terrier and pastoral breed groups were more likely to carry ticks, as were non-neutered dogs. Dogs with shorter hair were less likely to have ticks, and dogs were most likely to carry a tick in June. This study is of value because, unusually, it presents the results of a randomized sample of dogs and gives a prevalence which is higher than those previously recorded in Great Britain.

Frameworks for risk communication and disease management: the case of Lyme disease and countryside users

Management of zoonotic disease is necessary if countryside users are to gain benefit rather than suffer harm from their activities, and to avoid disproportionate reaction to novel threats. We introduce a conceptual framework based on the pressure-state-response model with five broad responses to disease incidence. Influencing public behaviour is one response and requires risk communication based on an integration of knowledge about the disease with an understanding of how publics respond to precautionary advice. A second framework emphasizes how risk communication involves more than information provision and should address dimensions including points-of-intervention over time, place and audience. The frameworks are developed by reference to tick-borne Lyme borreliosis (also known as Lyme disease), for which informed precautionary behaviour is particularly relevant. Interventions to influence behaviour can be directed by knowledge of spatial and temporal variation of tick abundance, what constitutes risky behaviour, how people respond to information of varying content, and an understanding of the social practices related to countryside use. The frameworks clarify the response options and help identify who is responsible for risk communication. These aspects are not consistently understood, and may result in an underestimation of the role of land-based organizations in facilitating appropriate precautionary behaviour.