Seasonal and habitat variation in the prevalence of Rickettsia helvetica in Ixodes ricinus ticks from Denmark

Uneven temporal distribution of piroplasms (Piroplasmida: Babesiidae, Theileriidae) in Haemaphysalis concinna in an urban biotope of the Western Palearctic focus region of this tick species

Haemaphysalis concinna is a Palearctic tick species known as a potential or proven vector of several pathogens, including a broad spectrum of Babesia and Theileria species. The aim of this study was to examine the monthly presence of these piroplasms in H. concinna specimens collected from the vegetation of an urban habitat in Budapest, Hungary, in 2019 and 2020. The questing abundance of H. concinna was highest in June. By contrast, the occurrence of T. capreoli in unfed H. concinna peaked in April, and was significantly more common in the spring, than in the rest of the year. Among the detected eleven Babesia genotypes, two were present only in nymphs and adults of H. concinna. These were identical in the amplified part of their 18S rRNA gene to piroplasms reported from the Far East. Three further Babesia genotypes, however, showed genetic heterogeneity and were also carried by larvae. Babesia-infected nymphs and adults were most common in May and July. In conclusion, the results of this study show that in a questing population of H. concinna the highest monthly prevalence of Babesia and Theileria spp. may be different from each other and from the peak abundance of carrier ticks. Based on previous reports on the effect of tick-borne pathogens on other species of ticks, the factors that may influence this phenomenon in H. concinna may include changes in the metabolism and behavior (host finding and feeding success) as well as survival rate of infected ticks. Further studies will be necessary to clarify this.

Prevalence and diversity of spotted fever group Rickettsia species in ixodid ticks from domestic dogs in Chad, Africa

Tick-borne pathogens in the genus Rickettsia are the causative agents of severe and potentially fatal spotted fever group (SFG) and typhus group diseases in dogs and humans. Climate, habitat, and land-use changes are impacting vector ranges, with expansions potentially resulting in novel pathogens being introduced into naïve locations. Despite the public health importance of SFG Rickettsia, there are relatively few data on the prevalence and diversity of rickettsial pathogens in sub-Saharan Africa. The aim of this study was to characterize the SFG Rickettsia prevalence and diversity in ixodid ticks (104 Amblyomma spp., 160 Rhipicephalus spp., and one Hyalomma truncatum) collected from domestic dogs in Chad, Africa. Ticks were screened for Rickettsia spp. using a nested PCR targeting the 17-kDa gene. Species identification was through bidirectional Sanger sequencing of the 17-kDa, ompA, ompB, and/or gltA gene targets. A total of 43.3 % (115/265) ticks were positive for Rickettsia spp. and six Rickettsia species were identified: R. africae, R. massiliae, R. conorii, R. felis, R. monacensis and Candidatus Rickettsia muridii. Seven additional samples were positive for Rickettsia of undetermined species. Rickettsia africae, an important zoonotic pathogen, was found in 81 % (79/97) of A. variegatum and 29 % (2/7) of an A. marmoreum complex species, a group that infests a wide range of birds and mammals, including humans. Finally, we detected a high diversity of Rickettsia spp., most of which were zoonotic, in Rh. muhsamae. Collectively these data indicate there is a risk of rickettsiosis in Chad and further studies on ticks and rickettsial pathogens in this region are warranted.

Spatial and temporal variation of five different pathogens and symbionts in Ixodes ricinus nymphs in the Netherlands

The incidence of diseases caused by pathogens transmitted by the tick Ixodes ricinus vary over time and space through incompletely understood mechanisms. An important determinant of the disease risk is the density of infected ticks, which is the infection prevalence times the density of questing ticks. We therefore investigated the spatial and temporal variation of four pathogens and one of the most abundant symbionts in Ixodes ricinus in questing nymphs over four years of monthly collections in 12 locations in the Netherlands. The infection prevalence of all microbes showed markedly different patterns with significant spatial variation for Borrelia burgdorferi (s.l.), Neoehrlichia mikurensis, Rickettsia helvetica, and Midichloria mitochondrii, significant seasonal variation of B. burgdorferi (s.l.), N. mikurensis, and M. mitochondrii and a significant interannual variation of R. helvetica. Despite its ubiquitous presence, no spatio-temporal variation was observed for the infection prevalence of B. miyamotoi. The variation in infection prevalence was generally smaller than the variation in the density of nymphs, which fluctuated substantially both seasonally and between locations. This means that the variation in the densities of infected nymphs for all pathogens was mostly the result of the variation in densities of nymphs. We also investigated whether there were positive or negative associations between the symbionts, and more specifically whether ticks infected with vertically transmitted symbionts like M. mitochondrii and R. helvetica, have a higher prevalence of horizontally transmitted symbionts, such as B. burgdorferi (s.l.) and N. mikurensis. We indeed found a clear positive association between M. mitochondrii and B. burgdorferi (s.l.). The positive association between R. helvetica and B. burgdorferi (s.l.) was less clear and was only shown in two locations. Additionally, we found a clear positive association between B. burgdorferi (s.l.) and N. mikurensis, which are both transmitted by rodents. Our longitudinal study indicated strong between-location variation, some seasonal patterns and hardly any differences between years for most symbionts. Positive associations between symbionts were observed, suggesting that infection with a (vertically transmitted) symbiont may influence the probability of infection with other symbionts, or that there is a common underlying mechanism (e.g. feeding on rodents).

The influence of forest habitat type on Ixodes ricinus infections with Rickettsia spp. in south-western Poland

This study investigates the prevalence of Rickettsia spp. in Ixodes ricinus tick populations in different forest habitat types (broadleaf forest, mixed broadleaf and coniferous forest, and coniferous forest) in south-western Poland. During the survey periods from April to June 2018 and 2019 a total of 494 I. ricinus ticks, including 374 nymphs, 60 females and 60 males, were tested for Rickettsia infections by nested PCR targeting the gltA gene. The overall infection rate was 42.3%; however, we observed statistically significant year-to-year variation. Infection rates varied between tick developmental stages and were significantly influenced by forest habitat type. As assessed by a generalized linear mixed model (GLMM), the highest infection rates were observed in mixed broadleaf and coniferous forests, while coniferous forests had a significant negative effect on infection prevalence. DNA sequencing of selected samples confirmed the predominance of Rickettsia helvetica (91.2%) and less frequent Rickettsia monacensis (8.8%). This study suggests that the forest habitat types can influence Rickettsia spp. infection in tick populations; however, a comprehensive understanding of all factors influencing the level of infection requires future study.

Tick-Borne Bacterial Diseases in Europe: Threats to public health

BACKGROUND

Tick-borne diseases, caused by bacterial pathogens, pose a growing threat to public health in Europe. This paper provides an overview of the historical context of the discovery of the most impactful pathogens transmitted by ticks, including Borrelia burgdorferi sensu lato, Rickettsia spp., Anaplasma spp., Francisella spp., Ehrlichia spp., and Neoehrlichia mikurensis. Understanding the historical context of their discovery provides insight into the evolution of our understanding of these pathogens.

METHODS AND RESULTS

Systematic investigation of the prevalence and transmission dynamics of these bacterial pathogens is provided, highlighting the intricate relationships among ticks, host organisms, and the environment. Epidemiology is explored, providing an in-depth analysis of clinical features associated with infections. Diagnostic methodologies undergo critical examination, with a spotlight on technological advancements that enhance detection capabilities. Additionally, the paper discusses available treatment options, addressing existing therapeutic strategies and considering future aspects.

CONCLUSIONS

By integrating various pieces of information on these bacterial species, the paper aims to provide a comprehensive resource for researchers and healthcare professionals addressing the impact of bacterial tick-borne diseases in Europe. This review underscores the importance of understanding the complex details influencing bacterial prevalence and transmission dynamics to better combat these emerging public health threats.

Rickettsiosis in Denmark: A nation-wide survey

Rickettsia helvetica has been reported at varying prevalences in Danish and other European Ixodes ricinus populations. Though apparently widespread and with reported cases of human infection, the significance of the bacteria as a threat to public health remains unclear. We present a nation-wide survey of rickettsia in ticks, roe deer and humans in Denmark. Ticks were collected by flagging and screened for presence of rickettsial DNA by polymerase chain reaction. Sera from roe deer, hunters, neuroborreliosis patients and blood donors were analyzed for presence of anti-R. helvetica and Rickettsia felis antibodies by immunofluorescence microscopy. The Rickettsia minimum infection rate in ticks was 4.9 % (367/973 pools positive, 7510 ticks in total), with 3.9 % in nymphs and 9.3 % in adults. Rickettsia helvetica accounted for 4.17 % and Rickettsia monacensis for 0.03 %, 0.6 % comprised non-differentiable rickettsial DNA. The prevalence of antibodies against R. helvetica was 2.8 % (9/319) in roe deer, while no hunters (n = 536) or blood donors (n = 181) were positive. The prevalence of anti-R. helvetica antibodies among Lyme neuroborreliosis patients was 6 % (3/47), where it co-occurred with Anaplasma phagocytophilum. Based on our study autochthonous rickettsiosis is of limited concern to the public health in Denmark, but our finding of R. monacensis for the first time in Denmark illustrates the dynamic nature of tick-borne pathogens, emphasizing that continuous surveillance is necessary.

Spotted Fever Group Rickettsiae in Ticks and Small Mammals from Grassland and Forest Habitats in Central Germany

Rickettsiae of the spotted fever group (SFG) are zoonotic tick-borne pathogens. Small mammals are important hosts for the immature life stages of two of the most common tick species in Europe, Ixodes ricinus and Dermacentor reticulatus. These hosts and vectors can be found in diverse habitats with different vegetation types like grasslands and forests. To investigate the influence of environmental and individual factors on Rickettsia prevalence, this study aimed to analyse the prevalence of SFG rickettsiae in ticks and small mammals in different small-scale habitats in central Germany for the first time. Small mammals of ten species and ticks of two species were collected from grasslands and forests in the Hainich-Dün region, central Germany. After species identification, DNA samples from 1098 ticks and ear snips of 1167 small mammals were screened for Rickettsia DNA by qPCR targeting the gltA gene. Positive samples were retested by conventional PCR targeting the ompB gene and sequencing. Rickettsia DNA was detected in eight out of ten small mammal species. Small mammal hosts from forests (14.0%) were significantly more often infected than those from grasslands (4.4%) (p < 0.001). The highest prevalence was found in the mostly forest-inhabiting genus Apodemus (14.8%) and the lowest in Microtus (6.6%), which inhabits grasslands. The prevalence was higher in D. reticulatus (46.3%) than in the I. ricinus complex (8.6%). Adult ticks were more often infected than nymphs (p = 0.0199). All sequenced rickettsiae in I. ricinus complex ticks were R. helvetica, and the ones in D. reticulatus were R. raoultii. Unlike adults, questing nymphs have had only one blood meal, which explains the higher prevalence in I. ricinus adults. Interestingly, habitat type did influence infection probability in small mammals, but did not in ticks. A possible explanation may be the high prevalence in Apodemus flavicollis and A. sylvaticus which were more abundant in the forest.

Tick-borne diseases under the radar in the North Sea Region

The impact of tick-borne diseases caused by pathogens such as Anaplasma phagocytophilum, Neoehrlichia mikurensis, Borrelia miyamotoi, Rickettsia helvetica and Babesia species on public health is largely unknown. Data on the prevalence of these pathogens in Ixodes ricinus ticks from seven countries within the North Sea Region in Europe as well as the types and availability of diagnostic tests and the main clinical features of their corresponding diseases is reported and discussed. Raised awareness is needed to discover cases of these under-recognized types of tick-borne disease, which should provide valuable insights into these diseases and their clinical significance.

Biodiversity in the Lyme-light: ecological restoration and tick-borne diseases in Europe

Biodiversity loss and the emergence of zoonotic diseases are two major global challenges. An urgent question is how ecosystems and wildlife communities can be restored whilst minimizing the risk of zoonotic diseases carried by wildlife. Here, we evaluate how current ambitions to restore Europe's natural ecosystems may affect the hazard of diseases vectored by the tick Ixodes ricinus at different scales. We find that effects of restoration efforts on tick abundance are relatively straightforward but that the interacting effects of vertebrate diversity and abundance on pathogen transmission are insufficiently known. Long-term integrated surveillance of wildlife communities, ticks, and their pathogens is needed to understand their interactions and to prevent nature restoration from increasing tick-borne disease (TBD) hazard.

The emergence and shift in seasonality of Lyme borreliosis in Northern Europe

Climate change has had a major impact on seasonal weather patterns, resulting in marked phenological changes in a wide range of taxa. However, empirical studies of how changes in seasonality impact the emergence and seasonal dynamics of vector-borne diseases have been limited. Lyme borreliosis, a bacterial infection spread by hard-bodied ticks, is the most common vector-borne disease in the northern hemisphere and has been rapidly increasing in both incidence and geographical distribution in many regions of Europe and North America. By analysis of long-term surveillance data (1995-2019) from across Norway (latitude 57°58'-71°08' N), we demonstrate a marked change in the within-year timing of Lyme borreliosis cases accompanying an increase in the annual number of cases. The seasonal peak in cases is now six weeks earlier than 25 years ago, exceeding seasonal shifts in plant phenology and previous model predictions. The seasonal shift occurred predominantly in the first 10 years of the study period. The concurrent upsurgence in case number and shift in case timing indicate a major change in the Lyme borreliosis disease system over recent decades. This study highlights the potential for climate change to shape the seasonal dynamics of vector-borne disease systems.

Molecular Detection of Rickettsia and Other Bacteria in Ticks and Birds in an Urban Fragment of Tropical Dry Forest in Magdalena, Colombia

Birds are important hosts in the life cycle of some species of ticks. In Colombia, there are few eco-epidemiological studies of tick-borne diseases; the existing ones have been focused on areas where unusual outbreaks have occurred. This study describes the identification of ticks collected from birds and vegetation, and the detection of bacteria in those ticks and in blood samples from birds in an urban fragment of tropical dry forest in the department of Magdalena, Colombia. Bird sampling was carried out monthly in 2021, and 367 birds, distributed among 41 species, were captured. All collected ticks were identified as Amblyomma sp. or Amblyomma dissimile. The presence of rickettsiae in ticks collected from birds was evaluated by molecular analysis of the gltA, ompA and sca1 genes. 16S rRNA meta-taxonomy was used to evaluate rickettsiae in ticks collected from vegetation and in blood samples from birds. The presence of the species "Candidatus Rickettsia colombianensi" was detected in ticks from birds. Bacteria of the family Rickettsiacea was the most abundant in ticks collected from vegetation. Bacteria of the families Staphylococcaceae, Comamonadaceae and Pseudomonadaceae were prevalent in the samples of blood from birds. Rickettsia spp. was also detected in low abundance in some of the bird blood samples.

Evaluation of factors influencing tick bites and tick-borne infections: a longitudinal study

BACKGROUND

Various tick-borne infections like borreliosis and rickettsiosis pose a health risk to humans in many parts of the world. We investigated seroprevalence of and seroconversion to Borrelia burgdorferi and Rickettsia spp. and relation to tick-bites, weather and clinical manifestations in Denmark.

METHODS

Blood donors were enrolled at the Hospital of Southern Jutland in June-July with follow-up November-February of 2018 and 2019. Blood samples were collected, and a questionnaire regarding tick bites, potential exposures and symptoms was completed at each visit. Samples were tested for presence of IgM and IgG antibodies directed against B. burgdorferi and Rickettsia spp. using R. helvetica and R. felis as antigens. Data were examined for correlation between tick bites, serological results, potential exposures and symptoms.

RESULTS

Two-hundred and fourteen (93 follow-ups) and 130 (38 follow-ups) blood donors were included in 2018 and 2019, respectively. The total borrelia seroconversion rate was 6.3% (CI 2.1-10.5), while the prevalence of IgM and IgG antibodies was 7.8% (CI 4.9-10.6) and 6.7% (CI 4-9.3), respectively. Seroconversion to Rickettsia spp. was detected in one participant. Tick bites and seroconversion were not significantly associated with the reported unspecific symptoms, but unspecific symptoms were common in the study population. There was no significant difference in number of tick bites or seroconversion/prevalence between seasons with highly alternating weather.

CONCLUSIONS

Results suggest that weather conditions in an individual year have a limited impact. Anti-Borrelia-antibodies do not seem to persist in serum for several years. Rickettsiosis is of limited concern in Denmark.

Spatial patterns of pathogen prevalence in questing Ixodes ricinus nymphs in southern Scandinavia, 2016

Tick-borne pathogens cause diseases in animals and humans, and tick-borne disease incidence is increasing in many parts of the world. There is a need to assess the distribution of tick-borne pathogens and identify potential risk areas. We collected 29,440 tick nymphs from 50 sites in Scandinavia from August to September, 2016. We tested ticks in a real-time PCR chip, screening for 19 vector-associated pathogens. We analysed spatial patterns, mapped the prevalence of each pathogen and used machine learning algorithms and environmental variables to develop predictive prevalence models. All 50 sites had a pool prevalence of at least 33% for one or more pathogens, the most prevalent being Borrelia afzelii, B. garinii, Rickettsia helvetica, Anaplasma phagocytophilum, and Neoehrlichia mikurensis. There were large differences in pathogen prevalence between sites, but we identified only limited geographical clustering. The prevalence models performed poorly, with only models for R. helvetica and N. mikurensis having moderate predictive power (normalized RMSE from 0.74-0.75, R2 from 0.43-0.48). The poor performance of the majority of our prevalence models suggest that the used environmental and climatic variables alone do not explain pathogen prevalence patterns in Scandinavia, although previously the same variables successfully predicted spatial patterns of ticks in the same area.

Molecular evidence of piroplasm infection in companion animals in Hunan Province, China

BACKGROUND

Feline and canine babesiosis is an important tick-borne disease caused by parasites of the genus Babesia. The disease has a worldwide distribution and causes serious health problems in domestic and wild canidae and felidae.

RESULTS

Genomic DNA was isolated from blood samples, which were randomly collected from pet dogs (n = 115) and cats (n = 25) in Changsha city of Hunan Province, China. Results of nested PCR assay targeting 18S rRNA gene and partial gene sequencing revealed that seven animals were infected with Babesia species, five dogs (5/115, 4.3%) and two cats (2/25, 8.0%). Sequence analysis showed that four dogs (3.5%) were positive for Babesia canis, and the other one for Babesia vogeli (0.87%). The two cats were infected by Babesia hongkongensis.

CONCLUSIONS

The findings of this study will expand knowledge of the distribution of Babesia species and provide important epidemiological information for the control of animal babesiosis in China.

Laboratory Diagnostics of Rickettsia Infections in Denmark 2008-2015

Rickettsiosis is a vector-borne disease caused by bacterial species in the genus Rickettsia. Ticks in Scandinavia are reported to be infected with Rickettsia, yet only a few Scandinavian human cases are described, and rickettsiosis is poorly understood. The aim of this study was to determine the prevalence of rickettsiosis in Denmark based on laboratory findings. We found that in the Danish individuals who tested positive for Rickettsia by serology, the majority (86%; 484/561) of the infections belonged to the spotted fever group. In contrast, we could confirm 13 of 41 (32%) PCR-positive individuals by sequencing and identified all of these as R. africae, indicating infections after travel exposure. These 13 samples were collected from wound/skin material. In Denmark, approximately 85 individuals test positive for Rickettsia spp. annually, giving an estimated 26% (561/2147) annual prevalence among those suspected of rickettsiosis after tick bites. However, without clinical data and a history of travel exposure, a true estimation of rickettsiosis acquired endemically by tick bites cannot be made. Therefore, we recommend that both clinical data and specific travel exposure be included in a surveillance system of Rickettsia infections.

Monitoring of ticks and tick-borne pathogens through a nationwide research station network in Finland

In 2015 a long-term, nationwide tick and tick-borne pathogen (TBP) monitoring project was started by the Finnish Tick Project and the Finnish Research Station network (RESTAT), with the goal of producing temporally and geographically extensive data regarding exophilic ticks in Finland. In the current study, we present results from the first four years of this collaboration. Ticks were collected by cloth dragging from 11 research stations across Finland in May-September 2015-2018 (2012-2018 in Seili). Collected ticks were screened for twelve different pathogens by qPCR: Borrelia afzelii, Borrelia garinii, Borrelia valaisiana, Borrelia burgdorferi sensu stricto, Borrelia miyamotoi, Babesia spp., Anaplasma phagocytophilum, Rickettsia spp., Candidatus Neoehrlichia mikurensis, Francisella tularensis, Bartonella spp. and tick-borne encephalitis virus (TBEV). Altogether 15 067 Ixodes ricinus and 46 Ixodes persulcatus were collected during 68 km of dragging. Field collections revealed different seasonal activity patterns for the two species. The activity of I. persulcatus adults (only one nymph detected) was unimodal, with activity only in May-July, whereas Ixodes ricinus was active from May to September, with activity peaks in September (nymphs) or July-August (adults). Overall, tick densities were higher during the latter years of the study. Borrelia burgdorferi sensu lato were the most common pathogens detected, with 48.9 ± 8.4% (95% Cl) of adults and 25.3 ± 4.4% of nymphs carrying the bacteria. No samples positive for F. tularensis, Bartonella or TBEV were detected. This collaboration project involving the extensive Finnish Research Station network has ensured enduring and spatially extensive, long-term tick data collection to the foreseeable future.

Multiple infections in questing nymphs and adult female Ixodes ricinus ticks collected in a recreational forest in Denmark

During its lifecycle, the generalist Ixodes ricinus takes up three blood meals from a wide selection of vertebrate hosts, some of which are reservoirs for multiple vector-associated pathogens. Since I. ricinus also readily bites humans, pets, and livestock, these hosts are at risk of becoming infected with more than one tick-borne pathogen. Multiple tick-borne infections are a public health concern, since they may increase diversity and duration of symptoms and complicate differential diagnosis and therapy. We used an existing Fluidigm real-time PCR chip to identify the minimum risk of exposure to infected/co-infected ticks in Denmark. We screened 509 nymphs and 504 adult female I. ricinus ticks for 17 different vector-associated pathogenic agents. The questing ticks were collected by flagging during the same season in two consecutive years in Grib forest in the capital region of Copenhagen. Overall, 19.1% of the nymphs and 52.2% of the adult female ticks harbored at least one zoonotic pathogen. The main agents were Borrelia spp., Anaplasma phagocytophilum and Rickettsia helvetica, while Candidatus Neoehrlichia mikurensis and Babesia venatorum both were present in less than 1% of the ticks. In 3.5% of the nymphs and 12.3% of adults we found more than one tick-borne pathogen. Of these, 15% were potentially triple or quadruple infections. Whereas mixed infections with Borrelia were equally distributed among both life stages, the adult ticks hosted 84.5% of the co-infections with different species of tick-borne pathogens, chiefly involving Borrelia species in combination with either R. helvetica or A. phagocytophilum. Statistical analyses indicated non-random co-occurrence of Borrelia spielmanii/Borrelia garinii in both life stages and B. garinii/Borrelia afzelii and B. garinii/Borrelia valaisiana in the nymphs. Although the overall prevalence of ticks hosting more than one infection only constituted 7.9% at the particular site investigated in this study, our results still underline that co-infections should be considered in diagnosis and treatment of tick-borne diseases in northern Europe.

Molecular detection and genetic diversity of Babesia canis canis in pet dogs in Henan Province, China

Canine babesiosis is an important tick-borne disease caused by Babesia spp. A total of 130 blood samples were randomly collected from pet dogs in Zhengzhou city, Henan Province, China, and screened for the presence of piroplasms with nested PCR and gene sequencing targeting the 18S rRNA gene. On the basis of blast analysis of the 18S rRNA gene sequences, our results revealed that seven dogs (5.4%) were infected with Babesia canis canis. The sequences were compared with those in GenBank, and alignments showed that all B. canis canis isolates belonged to genotype B. This is the first report of B. canis canis infection in dogs in China.

The importance of study duration and spatial scale in pathogen detection-evidence from a tick-infested island

Ticks (Acari: Ixodoidea) are among the most common vectors of zoonotic pathogens worldwide. While research on tick-borne pathogens is abundant, few studies have thoroughly investigated small-scale spatial differences in their occurrence. Here, we used long-term cloth-dragging data of Ixodes ricinus and its associated, known and putative pathogens (Borrelia burgdorferi s.l., Borrelia miyamotoi, Anaplasma phagocytophilum, Rickettsia spp., Candidatus Neoehrlichia mikurensis, Bartonella spp., Babesia spp., and tick-borne encephalitis virus, TBEV) from a small, well-studied island in southwestern Finland to analyze potential temporal and spatial differences in pathogen prevalence and diversity between and within different biotopes. We found robust evidence indicating significant dissimilarities in B. burgdorferi s.l., A. phagocytophilum, Rickettsia, and Ca. N. mikurensis prevalence, even between proximal study areas on the island. Moreover, during the 6 years of the ongoing study, we witnessed the possible emergence of TBEV and Ca. N. mikurensis on the island. Finally, the stable occurrence of a protozoan pathogen that has not been previously reported in Finland, Babesia venatorum, was observed on the island. Our study underlines the importance of detailed, long-term tick surveys for public health. We propose that by more precisely identifying different environmental factors associated with the emergence and upkeep of enzootic pathogen populations through rigorous longitudinal surveys, we may be able to create more accurate models for both current and future pathogen distributions.

High prevalence of Rickettsia helvetica in wild small mammal populations in Germany

Since the beginning of the 21st century, spotted fever rickettsioses are known as emerging diseases worldwide. Rickettsiae are obligately intracellular bacteria transmitted by arthropod vectors. The ecology of Rickettsia species has not been investigated in detail, but small mammals are considered to play a role as reservoirs. Aim of this study was to monitor rickettsiae in wild small mammals over a period of five years in four federal states of Germany. Initial screening of ear pinna tissues of 3939 animals by Pan-Rick real-time PCR targeting the citrate synthase (gltA) gene revealed 296 rodents of seven species and 19 shrews of two species positive for rickettsial DNA. Outer membrane protein gene (ompB, ompAIV) PCRs based typing resulted in the identification of three species: Rickettsia helvetica (90.9%) was found as the dominantly occurring species in the four investigated federal states, but Rickettsia felis (7.8%) and Rickettsia raoultii (1.3%) were also detected. The prevalence of Rickettsia spp. in rodents of the genus Apodemus was found to be higher (approximately 14%) than in all other rodent and shrew species at all investigated sites. General linear mixed model analyses indicated that heavier (older) individuals of yellow-necked mice and male common voles seem to contain more often rickettsial DNA than younger ones. Furthermore, rodents generally collected in forests in summer and autumn more often carried rickettsial DNA. In conclusion, this study indicated a high prevalence of R. helvetica in small mammal populations and suggests an age-dependent increase of the DNA prevalence in some of the species and in animals originating from forest habitats. The finding of R. helvetica and R. felis DNA in multiple small mammal species may indicate frequent trans-species transmission by feeding of vectors on different species. Further investigations should target the reason for the discrepancy between the high rickettsial DNA prevalence in rodents and the so far almost absence of clinical apparent human infections.

Rickettsioses in Denmark: A retrospective survey of clinical features and travel history

Rickettsia spp. can be found across the globe and cause disease of varying clinical severity, ranging from life-threatening infections with widespread vasculitis to milder, more localized presentations. Vector and, to some degree, reservoir are hematophagous arthropods, with most species harboured by ticks. In Denmark, rickettsiae are known as a cause of imported travel-related infections, but are also found endemically in ticks across the country. Data are, however, lacking on the geographical origin and clinical features of diagnosed cases. In this study, we have examined the travel history and clinical features of two groups of patients; 1) hospital-patients diagnosed with rickettsioses in the years 2010-2015 and 2) patients from primary health care (PHC) centers in Denmark having demonstrated anti-rickettsia antibodies in the years 2012-2015. The patients were identified using the Danish National Patient Registry (DNPR) and through the serological database at the State Serum Institute, where the laboratory diagnosis of rickettsioses is currently centralized. Data were collected for 86 hospital patients and 26 PHC center patients by reviewing hospital medical records and performing telephone interviews with PHC centers. Of the hospital patients, 91% (78/86) had a history of international travel 14 days prior to symptom start, with most having imported their infection from southern Africa, South Africa in particular (65%), and presenting with a clinical picture most compatible with African tick-bite fever caused by R. africae. Only two patients presented with a CRP > 100 mg/L and no mortalities were reported. At the PHC centers, most patients presented with mild flu-like symptoms and had an unknown (50%) or no history (19%) of international travel, raising the possibility of endemic rickettsioses. In view of our findings, rickettsioses do not appear to constitute a major public health problem in Denmark, with most cases being imported infections and potential endemic cases presenting as mild infections.

Molecular evidence of Rickettsia spp. in ixodid ticks and rodents in suburban, natural and rural habitats in Slovakia

BACKGROUND

Natural foci of tick-borne spotted fever group (SFG) rickettsiae of public health concern have been found in Slovakia, but the role of rodents in their circulation is unclear. Ticks (Ixodes ricinus, Ixodes trianguliceps, Dermacentor marginatus, Dermacentor reticulatus, Haemaphysalis concinna and Haemaphysalis inermis) and tissues of rodents (Apodemus flavicollis, Apodemus sylvaticus, Myodes glareolus, Microtus arvalis, Microtus subterraneus and Micromys minutus) were examined for the presence of SFG rickettsiae and Coxiella burnetii by molecular methods. Suburban, natural and rural habitats were monitored to acquire information on the role of ticks and rodents in the agents' maintenance in various habitat types of Slovakia.

RESULTS

The overall prevalence of rickettsial infection in questing I. ricinus and D. marginatus was 6.6% and 21.4%, respectively. Rickettsia helvetica, R. monacensis and non-identified rickettsial species were detected in I. ricinus, whereas R. slovaca and R. raoultii were identified in D. marginatus. Rickettsia spp.-infected I. ricinus occurred during the whole tick questing period. Rickettsia helvetica dominated (80.5%) followed by R. monacensis (6.5%). The species were present in all studied habitats. Rickettsia slovaca (66.7%) and R. raoultii (33.3%) were identified in D. marginatus from the rural habitat. Apodemus flavicollis was the most infested rodent species with I. ricinus, but My. glareolus carried the highest proportion of Rickettsia-positive I. ricinus larvae. Only 0.5% of rodents (A. flavicollis) and 5.2% of engorged I. ricinus removed from My. glareolus, A. flavicollis and M. arvalis were R. helvetica- and R. monacensis-positive. Coxiella burnetii was not detected in any of the tested samples. We hypothesize that rodents could play a role as carriers of infected ticks and contribute to the maintenance of rickettsial pathogens in natural foci.

CONCLUSIONS

Long-term presence of SFG Rickettsia spp. was confirmed in questing ticks from different habitat types of Slovakia. The results suggest a human risk for infection with the pathogenic R. helvetica, R. monacensis, R. slovaca and R. raoultii.

Tick-borne bacterial pathogens in southwestern Finland

Background

Ixodes ricinus and Ixodes persulcatus are the main vectors of Lyme borreliosis spirochetes and several other zoonotic bacteria in northern Europe and Russia. However, few studies screening bacterial pathogens in Finnish ticks have been conducted. Therefore, reports on the occurrence and prevalence of several bacterial pathogens detected from ticks elsewhere in Europe and Russia are altogether missing from Finland. The main aim of the current study was to produce novel data on the occurrence and prevalence of several tick-borne bacterial pathogens in ticks collected from southwestern Finland.

Methods

Ticks were collected in 2013–2014 by blanket dragging from 25 localities around southwestern Finland, and additionally from a dog in Lempäälä. Collected ticks were molecularly identified and screened for Borrelia burgdorferi s.l., Borrelia miyamotoi, Rickettsia, Bartonella and Candidatus Neoehrlichia mikurensis using quantitative PCR. Furthermore, detected Rickettsia spp. were sequenced using conventional PCR to determine species.

Results

A total of 3169 ticks in 1174 DNA samples were screened for the listed pathogens. The most common bacteria detected was B. burgdorferi (s.l.) (18.5 % nymphal and 23.5 % adult ticks), followed by Rickettsia spp. (1.1 %; 5.1 %) and B. miyamotoi (0.51 %; 1.02 %). B. miyamotoi and Rickettsia spp. were also detected in larval samples (minimum infection rates 0.31 % and 0.21 %, respectively). Detected Rickettsia spp. were identified by sequencing as R. helvetica and R. monacensis. All screened samples were negative for Bartonella spp. and Ca. N. mikurensis.

Conclusions

In the current study we report for the first time the presence of Rickettsia in Finnish ticks. Furthermore, Rickettsia spp. and B. miyamotoi were found from larval tick samples, emphasizing the importance they may have as vectors of these pathogens. Comparisons of tick density estimates and B. burgdorferi (s.l.) prevalence made between the current study and a previous study conducted in 2000 in ten out of the 25 study localities suggest that an increase in tick abundance and B. burgdorferi (s.l.) prevalence has occurred in at least some of the study localities.

Seasonal analysis of Rickettsia species in ticks in an agricultural site of Slovakia

Many rickettsiae of the spotted fever group are emerging pathogens causing serious diseases associated with vertebrate hosts. Ixodidae ticks are known as their vectors. Investigation of the relative abundance of questing Ixodes ricinus and their infection with Rickettsia spp. in an agricultural site comprising a game reserve in Slovakia was the aim of this study. In total, 2198 I. ricinus (492 larvae, 1503 nymphs and 203 adults) were collected by flagging the vegetation along 100 m(2) transects in Rozhanovce (eastern Slovakia): 334, 595 and 1269 in 2011, 2012 and 2013, respectively. Considering questing nymphs and adults, the highest relative density of 81 individuals/100 m(2) was observed in May 2013, the lowest of 0.3 individuals/100 m(2) in March 2012. A total of 1056 ticks (853 nymphs, 100 females and 103 males; 2011: n = 329, 2012: n = 509 and 2013: n = 218) were individually screened by PCR-based methods for the presence of Rickettsia spp. The overall prevalences were 7.3% for nymphs, 15% for females, 7.8% for males; 7.0% in 2011, 8.4% in 2012, and 8.7% in 2013. The maximum prevalences were observed in July in nymphs and in May in adults. Sequencing showed infection with R. helvetica in 73 ticks (72.6% nymphs, 16.4% females, 11% males) and with R. monacensis in 11 ticks (8 nymphs, 3 females). The results showed the circulation of pathogenic Rickettsia species in the agricultural site and a potential risk for humans to encounter infected ticks.

Babesia spp. and other pathogens in ticks recovered from domestic dogs in Denmark

Background

Newly recognized endemic foci for human babesiosis include Europe, where Ixodes ricinus, a vector for several species of Babesia, is the most commonly identified tick. Vector-based surveillance provides an early warning system for the emergence of human babesiosis, which is likely to be under-reported at emerging sites. In the present study, we set out to screen I. ricinus collected from Danish domestic dogs for Babesia, in order to identify whether humans in Denmark are exposed to the parasite.

Findings

A total of 661 ticks (Ixodes spp.) were collected from 345 Danish domestic dogs during April-September 2011 and pooled, one sample per dog. DNA was extracted from each sample and examined by PCR and sequencing for Rickettsia spp., Borrelia burgdorferi sensu lato, Bartonella spp., Francisella tularensis, Candidatus Neoehrlichia mikurensis, and Babesia spp. In total, 34% of the samples were positive for tick-borne microorganisms potentially pathogenic to humans: Rickettsia spp. were detected in 16% of the pools, with 79% being R. helvetica. Borrelia burgdorferi sensu lato was found in 15%, with the main species identified as Borrelia afzelii (39%). Likewise, 8% of the samples were positive for Babesia spp. (Babesia microti, 82%; Babesia venatorum (‘EU1’), 18%). Lastly, 1% of the samples tested positive for Candidatus Neoehrlichia mikurensis, and 0.6% for Bartonella spp. No ticks were found to be infected with Francisella tularensis.

Conclusions

Our data are in support of endemic occurrence of potentially zoonotic Babesia in Denmark and confirms I. ricinus as a vector of multiple pathogens of public health concern.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-0843-0) contains supplementary material, which is available to authorized users.

Ixodes ricinus and Its Transmitted Pathogens in Urban and Peri-Urban Areas in Europe: New Hazards and Relevance for Public Health

Tick-borne diseases represent major public and animal health issues worldwide. Ixodes ricinus, primarily associated with deciduous and mixed forests, is the principal vector of causative agents of viral, bacterial, and protozoan zoonotic diseases in Europe. Recently, abundant tick populations have been observed in European urban green areas, which are of public health relevance due to the exposure of humans and domesticated animals to potentially infected ticks. In urban habitats, small and medium-sized mammals, birds, companion animals (dogs and cats), and larger mammals (roe deer and wild boar) play a role in maintenance of tick populations and as reservoirs of tick-borne pathogens. Presence of ticks infected with tick-borne encephalitis virus and high prevalence of ticks infected with Borrelia burgdorferi s.l., causing Lyme borreliosis, have been reported from urbanized areas in Europe. Emerging pathogens, including bacteria of the order Rickettsiales (Anaplasma phagocytophilum, "Candidatus Neoehrlichia mikurensis," Rickettsia helvetica, and R. monacensis), Borrelia miyamotoi, and protozoans (Babesia divergens, B. venatorum, and B. microti) have also been detected in urban tick populations. Understanding the ecology of ticks and their associations with hosts in a European urbanized environment is crucial to quantify parameters necessary for risk pre-assessment and identification of public health strategies for control and prevention of tick-borne diseases.

High-throughput screening of tick-borne pathogens in Europe

Due to increased travel, climatic, and environmental changes, the incidence of tick-borne disease in both humans and animals is increasing throughout Europe. Therefore, extended surveillance tools are desirable. To accurately screen tick-borne pathogens (TBPs), a large scale epidemiological study was conducted on 7050 Ixodes ricinus nymphs collected from France, Denmark, and the Netherlands using a powerful new high-throughput approach. This advanced methodology permitted the simultaneous detection of 25 bacterial, and 12 parasitic species (including; Borrelia, Anaplasma, Ehrlichia, Rickettsia, Bartonella, Candidatus Neoehrlichia, Coxiella, Francisella, Babesia, and Theileria genus) across 94 samples. We successfully determined the prevalence of expected (Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum, Rickettsia helvetica, Candidatus Neoehrlichia mikurensis, Babesia divergens, Babesia venatorum), unexpected (Borrelia miyamotoi), and rare (Bartonella henselae) pathogens in the three European countries. Moreover we detected Borrelia spielmanii, Borrelia miyamotoi, Babesia divergens, and Babesia venatorum for the first time in Danish ticks. This surveillance method represents a major improvement in epidemiological studies, able to facilitate comprehensive testing of TBPs, and which can also be customized to monitor emerging diseases.

Ixodes ricinus and Its Transmitted Pathogens in Urban and Peri-Urban Areas in Europe: New Hazards and Relevance for Public Health

Tick-borne diseases represent major public and animal health issues worldwide. Ixodes ricinus, primarily associated with deciduous and mixed forests, is the principal vector of causative agents of viral, bacterial, and protozoan zoonotic diseases in Europe. Recently, abundant tick populations have been observed in European urban green areas, which are of public health relevance due to the exposure of humans and domesticated animals to potentially infected ticks. In urban habitats, small and medium-sized mammals, birds, companion animals (dogs and cats), and larger mammals (roe deer and wild boar) play a role in maintenance of tick populations and as reservoirs of tick-borne pathogens. Presence of ticks infected with tick-borne encephalitis virus and high prevalence of ticks infected with Borrelia burgdorferi s.l., causing Lyme borreliosis, have been reported from urbanized areas in Europe. Emerging pathogens, including bacteria of the order Rickettsiales (Anaplasma phagocytophilum, "Candidatus Neoehrlichia mikurensis," Rickettsia helvetica, and R. monacensis), Borrelia miyamotoi, and protozoans (Babesia divergens, B. venatorum, and B. microti) have also been detected in urban tick populations. Understanding the ecology of ticks and their associations with hosts in a European urbanized environment is crucial to quantify parameters necessary for risk pre-assessment and identification of public health strategies for control and prevention of tick-borne diseases.

Update on tick-borne rickettsioses around the world: a geographic approach

Tick-borne rickettsioses are caused by obligate intracellular bacteria belonging to the spotted fever group of the genus Rickettsia. These zoonoses are among the oldest known vector-borne diseases. However, in the past 25 years, the scope and importance of the recognized tick-associated rickettsial pathogens have increased dramatically, making this complex of diseases an ideal paradigm for the understanding of emerging and reemerging infections. Several species of tick-borne rickettsiae that were considered nonpathogenic for decades are now associated with human infections, and novel Rickettsia species of undetermined pathogenicity continue to be detected in or isolated from ticks around the world. This remarkable expansion of information has been driven largely by the use of molecular techniques that have facilitated the identification of novel and previously recognized rickettsiae in ticks. New approaches, such as swabbing of eschars to obtain material to be tested by PCR, have emerged in recent years and have played a role in describing emerging tick-borne rickettsioses. Here, we present the current knowledge on tick-borne rickettsiae and rickettsioses using a geographic approach toward the epidemiology of these diseases.

Use of DNA sequences for Rickettsia identification in Ixodes ricinus ticks: the first detection of Rickettsia monacensis in Poland

The cosmopolitan tick Ixodes ricinus inhabiting Europe, including Poland, is a vector for many pathogens, such as various Rickettsia species, which spread to new territories. They are present mainly in the Mediterranean countries, but have also been found in Central Europe at increasing frequency. In the present study, the gltA gene, encoding citrate synthase, and an internal transcribed spacer (ITS) were employed to detect the DNA and identify the species of tick-borne pathogens of the Rickettsia genus. The presence of bacterial DNA was detected in 9.5% of the examined I. ricinus individuals. Based on the nucleotide sequences of the analysed genomic fragments, most pathogens were identified as Rickettsia helvetica, while Rickettsia monacensis was revealed in one case. We have described for the first time, to our knowledge, the occurrence of this species in Poland. Both markers employed in the experiments were successful in species identification of R. helvetica. The newly described species R. monacensis may be identified by the protein-coding gene, but the ITS nucleotide sequences proved insufficient.

Contours of risk: spatializing human behaviors to understand disease dynamics in changing landscapes

We echo viewpoints presented in recent publications from EcoHealth and other journals arguing for the need to understand linkages between human health, disease ecology, and landscape change. We underscore the importance of incorporating spatialities of human behaviors and perceptions in such analyses to further understandings of socio-ecological interactions mediating human health. We use Buruli ulcer, an emerging necrotizing skin infection and serious health concern in central Ghana, to illustrate our argument.

Occurrence of Babesia spp., Rickettsia spp. and Bartonella spp. in Ixodes ricinus in Bavarian public parks, Germany

Background

Only limited information is available about the occurrence of ticks and tick-borne pathogens in public parks, which are areas strongly influenced by human beings. For this reason, Ixodes ricinus were collected in public parks of different Bavarian cities in a 2-year survey (2009 and 2010) and screened for DNA of Babesia spp., Rickettsia spp. and Bartonella spp. by PCR. Species identification was performed by sequence analysis and alignment with existing sequences in GenBank. Additionally, coinfections with Anaplasma phagocytophilum were investigated.

Results

The following prevalences were detected: Babesia spp.: 0.4% (n = 17, including one pool of two larvae) in 2009 and 0.5 to 0.7% (n = 11, including one pool of five larvae) in 2010; Rickettsia spp.: 6.4 to 7.7% (n = 285, including 16 pools of 76 larvae) in 2009. DNA of Bartonella spp. in I. ricinus in Bavarian public parks could not be identified. Sequence analysis revealed the following species: Babesia sp. EU1 (n = 25), B. divergens (n = 1), B. divergens/capreoli (n = 1), B. gibsoni-like (n = 1), R. helvetica (n = 272), R. monacensis IrR/Munich (n = 12) and unspecified R. monacensis (n = 1). The majority of coinfections were R. helvetica with A. phagocytophilum (n = 27), but coinfections between Babesia spp. and A. phagocytophilum, or Babesia spp. and R. helvetica were also detected.

Conclusions

I. ricinus ticks in urban areas of Germany harbor several tick-borne pathogens and coinfections were also observed. Public parks are of particularly great interest regarding the epidemiology of tick-borne pathogens, because of differences in both the prevalence of pathogens in ticks as well as a varying species arrangement when compared to woodland areas. The record of DNA of a Babesia gibsoni-like pathogen detected in I. ricinus suggests that I. ricinus may harbor and transmit more Babesia spp. than previously known. Because of their high recreational value for human beings, urban green areas are likely to remain in the research focus on public health issues.

Pathogenic landscapes: interactions between land, people, disease vectors, and their animal hosts

BACKGROUND

Landscape attributes influence spatial variations in disease risk or incidence. We present a review of the key findings from eight case studies that we conducted in Europe and West Africa on the impact of land changes on emerging or re-emerging vector-borne diseases and/or zoonoses. The case studies concern West Nile virus transmission in Senegal, tick-borne encephalitis incidence in Latvia, sandfly abundance in the French Pyrenees, Rift Valley Fever in the Ferlo (Senegal), West Nile Fever and the risk of malaria re-emergence in the Camargue, and rodent-borne Puumala hantavirus and Lyme borreliosis in Belgium.

RESULTS

We identified general principles governing landscape epidemiology in these diverse disease systems and geographic regions. We formulated ten propositions that are related to landscape attributes, spatial patterns and habitat connectivity, pathways of pathogen transmission between vectors and hosts, scale issues, land use and ownership, and human behaviour associated with transmission cycles.

CONCLUSIONS

A static view of the "pathogenecity" of landscapes overlays maps of the spatial distribution of vectors and their habitats, animal hosts carrying specific pathogens and their habitat, and susceptible human hosts and their land use. A more dynamic view emphasizing the spatial and temporal interactions between these agents at multiple scales is more appropriate. We also highlight the complementarity of the modelling approaches used in our case studies. Integrated analyses at the landscape scale allows a better understanding of interactions between changes in ecosystems and climate, land use and human behaviour, and the ecology of vectors and animal hosts of infectious agents.