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

There Goes the Neighbourhood-A Multi-City Study Reveals Ticks and Tick-Borne Pathogens Commonly Occupy Urban Green Spaces

INTRODUCTION

Humans acquire tick-borne pathogens (TBPs) from infected ticks contacted during outdoor activities. Outdoor activity is at its highest in urban green spaces, where the presence of tick populations has increasingly been observed. Consequently, more insight into factors influencing the presence of ticks therein is needed. Here, we assess the occurrence of ticks and several TBPs in urban green spaces in Finland, estimate related human hazard and assess how landscape features influence tick and TBP occurrence therein.

METHODS

Ticks collected from five cities during 2019-2020 were utilised. Borrelia, Rickettsia, Neoehrlichia mikurensis, Anaplasma phagocytophilum , Babesia and TBEV were screened from ticks using qPCR. Various landscape features were calculated and utilised in generalised linear mixed models to assess their contribution towards tick and TBP occurrence in green spaces. Finally, human population density proximate to each study site was calculated and used to create population-weighted risk indices.

RESULTS

Borrelia were the most common pathogens detected, with 22% of nymphs and 43% of adults infected. Increasing forest cover had a positive effect on the densities of nymphs and adults, whereas forest size had a negative effect. Middling percentages of artificial surfaces predicted higher nymph densities than low or high values. Human population-weighted risk estimates were highly varied, even within cities. A positive correlation was observed between total city population and risk indices.

CONCLUSIONS

Ticks and TBPs are commonplace in urban green spaces in Finland. Enzootic cycles for Borrelia and Rickettsia appear to be well maintained within cities, leading to widespread risk of infection therein. Our results suggest that nymph densities are highest in urban forests of medium size, whereas small or large forests show reduced densities. Green spaces of roughly similar risk can be found in cities of different sizes, emphasising that the identification of areas of particularly high hazard is important for effective mitigation actions.

Different environmental factors predict the occurrence of tick-borne encephalitis virus (TBEV) and reveal new potential risk areas across Europe via geospatial models

BACKGROUND

Tick-borne encephalitis (TBE) is the most serious tick-borne viral disease in Europe. Identifying TBE risk areas can be difficult due to hyper focal circulation of the TBE virus (TBEV) between mammals and ticks. To better define TBE hazard risks and elucidate regional-specific environmental factors that drive TBEV circulation, we developed two machine-learning (ML) algorithms to predict the habitat suitability (maximum entropy), and occurrence of TBEV (extreme gradient boosting) within distinct European regions (Central Europe, Nordics, and Baltics) using local variables of climate, habitat, topography, and animal hosts and reservoirs.

METHODS

Geocoordinates that reported the detection of TBEV in ticks or rodents and anti-TBEV antibodies in rodent reservoirs in 2000 or later were extracted from published and grey literature. Region-specific ML models were defined via K-means clustering and trained according to the distribution of extracted geocoordinates relative to explanatory variables in each region. Final models excluded colinear variables and were evaluated for performance.

RESULTS

521 coordinates (455 ticks; 66 rodent reservoirs) of TBEV occurrence (2000-2022) from 100 records were extracted for model development. The models had high performance across regions (AUC: 0.72-0.92). The strongest predictors of habitat suitability and TBEV occurrence in each region were associated with different variable categories: climate variables were the strongest predictors of habitat suitability in Central Europe; rodent reservoirs and elevation were strongest in the Nordics; and animal hosts and land cover contributed most to the Baltics. The models predicted several areas with few or zero reported TBE incidence as highly suitable (≥ 60%) TBEV habitats or increased probability (≥ 25%) of TBEV occurrence including western Norway coastlines, northern Denmark, northeastern Croatia, eastern France, and northern Italy, suggesting potential capacity for locally-acquired autochthonous TBEV infections or possible underreporting of TBE cases based on reported human surveillance data.

CONCLUSIONS

This study shows how varying environmental factors drive the occurrence of TBEV within different European regions and identifies potential new risk areas for TBE. Importantly, we demonstrate the utility of ML models to generate reliable insights into TBE hazard risks when trained with sufficient explanatory variables and to provide high resolution and harmonized risk maps for public use.

Knowledge, attitudes, and practices towards vector-borne diseases in changing climate in Finland

With climate change, the geographic distribution of some VBDs has expanded, highlighting the need for adaptation, and managing the risks associated with emergence in new areas. We conducted a questionnaire survey on the knowledge, attitudes, and practices (KAP) about vector-borne diseases (VBDs) among sample of Finnish residents. The questions were scored and the level of KAP was determined based on scoring as poor, fair, good, or excellent. Binary logistic regression analysis was used to evaluate the associations of different KAP levels with sex, age, education, and possible previous VPD infection. We received 491/1995 (25%) responses across the country and detected generally good knowledge, but only fair practices towards VBDs. Sex and age of the respondents were most often significantly associated with the level of KAP (P > 0.05). Despite the generally good knowledge, we detected major gaps, especially regarding the distinction of tick-borne encephalitis and Lyme borreliosis (LB), risk of disease, and protective measures. Additionally, many respondents thought the vaccination protects against LB or tick bites. This calls for awareness raising on disease risk and prevention measures. With increasing cases and the effects of climate change, surveillance of VBDs communication to the general public should be strengthened.

An Updated Review on the Spatial Distribution of Borrelia burgdorferi Sensu Lato Across Ticks, Animals and Humans in Northeastern China and Adjacent Regions

BACKGROUND

Lyme disease is a tick-borne zoonotic disease caused by Borrelia burgdorferi sensu lato and is prevalent in northeastern Asia, particularly in the forested area of Northeastern China. However, a lack of systematic data on the spatial distribution of B. burgdorferi in this region hinders the prediction of its transmission risk across the landscape.

METHODS

To provide an updated overview and establish a comprehensive spatial distribution database, we conducted a systematic review of literature published between 2000 and 2022. We collected and compiled relevant data on B. burgdorferi in Northeastern China and its neighbouring regions, outlining its distribution in ticks, wild animals, livestock and humans. Spatial analysis was performed to identify spatial clusters of tick positivity and host infection rates.

RESULTS

From a total of 1823 literature, we selected 110 references to compile 626 detection records of B. burgdorferi, including 288 in ticks, 109 in wildlife, 111 in livestock and domestic animals and 100 in humans. The average detection rate of B. burgdorferi in ticks was approximately 20%, with wildlife, livestock and domestic animal host positivity rates below 50% and human seroprevalence rates varying from 0.94% to 44.18%.

CONCLUSIONS

The study identified the presence of 17 tick species and ten genotypes of B. burgdorferi in the region, indicating a broad distribution. Notably, B. burgdorferi exhibited notable clustering, particularly in the central and eastern areas of Jilin Province, warranting further investigation.

Ten years of detecting Neoehrlichia mikurensis infections in Sweden: demographic, clinical and inflammatory parameters

PURPOSE

To increase knowledge about the varied clinical manifestations of human infection with the emerging tick-borne pathogen Neoehrlichia mikurensis.

METHODS

All patients diagnosed in Sweden with N. mikurensis infection during a 10-year period (2013-2023) were investigated regarding their demographic factors, risk factors, comorbidities, clinical signs and symptoms, and laboratory results. Multivariate models were generated using "Orthogonal Projections to Latent Structures-Discriminant Analysis" to identify clinical and immune parameters associated with N. mikurensis infection.

RESULTS

During the 10-year period, 134 patients were diagnosed with N. mikurensis infection, 102 of whom were included in this study. Most of the patients (79%) were immunosuppressed. The main comorbidities were malignant B-cell lymphomas, multiple sclerosis, and rheumatoid arthritis. Rituximab therapy (59%) and splenectomy (14%) featured prominently. All patients resided in the southern tick-endemic part of Sweden, yet one-third of them were diagnosed in wintertime when ticks are inactive. Two asymptomatically infected blood donors were identified but transfusion-transmitted infection was not confirmed. Increased levels of C-reactive protein, orosomucoid, and total IgM in serum were associated with neoehrlichiosis. Previously unreported symptoms such as ankle edema, neck pain, numbness, and sudden deafness were detected in some patients. One case of aplastic anemia partially improved after eradication of the infection.

CONCLUSIONS

Neoehrlichiosis is a multi-faceted emerging infectious disease.

Pathogens transmitted by Ixodes ricinus

Ixodes ricinus is the most important tick vector in central and western Europe and one of the most researched parasites. However, in the published literature on the tick and the pathogens it transmits, conjecture about specific transmission cycles and the clinical significance of certain microbes is not always clearly separated from confirmed facts. This article aims to present up-to-date, evidence-based information about the well-researched human pathogens tick-borne encephalitis virus, louping-ill virus, Anaplasma phagocytophilum, Borrelia burgdorferi sensu lato and several Babesia species, with a focus on their development in the tick, transmission dynamics and the reservoir hosts that support their circulation in the environment. Borrelia miyamotoi, Neoehrlichia mikurensis, Rickettsia helvetica and Rickettsia monacensis, which are much less common causes of disease but may affect immunocompromised patients, are also briefly discussed. Finally, the possible role of I. ricinus in the transmission of Coxiella burnetii, Francisella tularensis, Bartonella spp. and Spiroplasma ixodetis is reviewed.

The prevalence of pathogens in ticks collected from humans in Belgium, 2021, versus 2017

BACKGROUND

Ticks carry a variety of microorganisms, some of which are pathogenic to humans. The human risk of tick-borne diseases depends on, among others, the prevalence of pathogens in ticks biting humans. To follow-up on this prevalence over time, a Belgian study from 2017 was repeated in 2021.

METHODS

During the tick season 2021, citizens were invited to have ticks removed from their skin, send them and fill in a short questionnaire on an existing citizen science platform for the notification of tick bites (TekenNet). Ticks were morphologically identified to species and life stage level and screened using multiplex qPCR targeting, among others, Borrelia burgdorferi (sensu lato), Anaplasma phagocytophilum, Borrelia miyamotoi, Neoehrlichia mikurensis, Babesia spp., Rickettsia helvetica and tick-borne encephalitis virus (TBEV). The same methodology as in 2017 was used.

RESULTS

In 2021, the same tick species as in 2017 were identified in similar proportions; of 1094 ticks, 98.7% were Ixodes ricinus, 0.8% Ixodes hexagonus and 0.5% Dermacentor reticulatus. A total of 928 nymphs and adults could be screened for the presence of pathogens. Borrelia burgdorferi (s.l.) was detected in 9.9% (95% CI 8.2-12.0%), which is significantly lower than the prevalence of 13.9% (95% CI 12.2-15.7%) in 2017 (P = 0.004). The prevalences of A. phagocytophilum (4.7%; 95% CI 3.5-6.3%) and R. helvetica (13.3%; 95% CI 11.2-15.6%) in 2021 were significantly higher compared to 2017 (1.8%; 95% CI 1.3-2.7% and 6.8%; 95% CI 5.6-8.2% respectively) (P < 0.001 for both). For the other pathogens tested, no statistical differences compared to 2017 were found, with prevalences ranging between 1.5 and 2.9% in 2021. Rickettsia raoultii was again found in D. reticulatus ticks (n = 3/5 in 2021). Similar to 2017, no TBEV was detected in the ticks. Co-infections were found in 5.1% of ticks. When combining co-infection occurrence in 2017 and 2021, a positive correlation was observed between B. burgdorferi (s.l.) and N. mikurensis and B. burgdorferi (s.l.) and B. miyamotoi (P < 0.001 for both).

CONCLUSIONS

Although the 2021 prevalences fell within expectations, differences were found compared to 2017. Further research to understand the explanations behind these differences is needed.

Genomic signatures of hybridization between Ixodes ricinus and Ixodes persulcatus in natural populations

Identifying hybridization between common pathogen vectors is essential due to the major public health implications through risks associated with hybrid's enhanced pathogen transmission potential. The hard-ticks Ixodes ricinus and Ixodes persulcatus are the two most common vectors of tick-borne pathogens that affect human and animal health in Europe. Ixodes ricinus is a known native species in Finland with a well-known distribution, whereas I. persulcatus has expanded in range and abundance over the past 60 years, and currently it appears the most common tick species in certain areas in Finland. Here we used double-digest restriction site-associated DNA (ddRAD) sequencing on 186 ticks (morphologically identified as 92 I. ricinus, and 94 I. persulcatus) collected across Finland to investigate whether RAD generated single nucleotide polymorphisms (SNPs) can discriminate tick species and identify potential hybridization events. Two different clustering methods were used to assign specific species based on how they clustered and identified hybrids among them. We were able to discriminate between the two tick species and identified 11 putative hybrids with admixed genomic proportions ranging from approximately 24 to 76 percent. Four of these hybrids were morphologically identified as I. ricinus while the remaining seven were identified as I. persulcatus. Our results thus indicate that RAD SNPs are robust in identifying both species of the ticks as well as putative hybrids. These results further suggest ongoing hybridization between I. ricinus and I. persulcatus in their natural populations in Finland. The unique ability of RAD markers to discriminate between tick species and hybrids adds a useful aspect to tick evolutionary studies. Our findings align with previous studies and suggest a shared evolutionary history between the species, with instances of individuals possessing a considerable proportion of the other species' genome. This study is a significant step in understanding the formation of hybridization zones due to range expansion potentially associated with climate change.

Ticks - public health risks in urban green spaces

BACKGROUND

Urban green spaces are important for human health, but they may expose visitors to tick-borne diseases. This not only presents a potential public health challenge but also undermines the expected public health gains from urban green spaces. The aim of this study is to assess the public health risk of tick-borne diseases in an urban green space used for recreation in Stockholm, Sweden.

METHODS

We used a mixed method approach identifying both the magnitude of the tick hazard and the extent of the human exposure to tick-borne diseases. At six entry points to an urban green space, we sampled ticks and documented microhabitat conditions from five randomly assigned 2 m × 2 m plots. Surrounding habitat data was analyzed using geographical information system (GIS). Nymphs and adult ticks were tested for Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum using TaqMan qPCR. Positive B. burgdorferi (s.l.) ticks were further analyzed by nested PCR amplification and sequence analysis. Population census data and visitor count data were used to estimate the degree of human exposure to tick-borne diseases. To further understand the degree to which visitors get in contact with infected ticks we also conducted interviews with visitors to green spaces.

RESULTS

High tick densities were commonly found in humid broadleaved forest with low field vegetation. High pathogen prevalence was significantly correlated with increasing proportions of artificial areas. Integrating the tick hazard with human exposure we found that the public health risk of tick-borne diseases was moderate to high at most of the studied entry points. Many of the visitors frequently used urban green spaces. Walking was the most common activity, but visitors also engaged in activities with higher risk for tick encounters. Individual protective measures were connected to specific recreational activities such as picking berries or mushrooms.

CONCLUSIONS

The number of visitors can be combined with tick inventory data and molecular analyses of pathogen prevalence to make crude estimations of the public health risk of tick-borne diseases in urban green spaces. The risk of encountering infected ticks is omnipresent during recreational activities in urban green spaces, highlighting the need for public health campaigns to reduce the risk of tick-borne diseases.

Adult-Onset Encephalitis over Twelve Years in Easternmost Finland

INTRODUCTION

The epidemiology of encephalitis varies by region and time. Available Finnish data are outdated and there are no data from eastern parts of the country nor concerning the occurrence of autoimmune encephalitides.

MATERIALS AND METHODS

Patients with encephalitis were identified from mandatory administrative registries in North Karelia Central Hospital. The diagnoses were verified and data extracted by reviewing the patient records. Study period was 2010-2021. Only patients >16 years of age were included.

RESULTS

Fifty-one patients with a clinical encephalitis were identified (55% men) with a median age of 65 years (interquartile range 45, 73; total age range 16-88 years) indicating a crude incidence of 3.1/100,000 person-years for the entire study period. A specific aetiology could be identified in 31 cases (61%) with tick-borne encephalitis (TBE) being the most common one (20% of all 51 cases), followed by herpes simplex virus type 1 (HSV-1, 16%) and varicella zoster virus (VZV, 14%). Autoimmune aetiology was confirmed in 10%. TBE was most often found in the youngest age group (16-52 years of age) and the herpes viruses in the oldest group (71 years or older). A specific cause was most often identified in the oldest patients (78%). TBE patients were younger than patients with VZV (p = 0.0009) or HSV-1 (p = 0.0057), but there was no difference when they were compared to patients with autoimmune (p = 0.27) or unknown (p = 0.074) aetiology. At presentation, there were differences in the occurrence of some clinical signs and symptoms between aetiologies but nothing specific. Eight patients (16%) were immunosuppressed. Inpatient seizures occurred in 10 patients (20%). In these cases, the aetiology was HSV-1 in 50% and TBE or VZV in none. A full recovery was observed in 51% of all patients while 3 patients (6%) had died of the encephalitis while in hospital or shortly after discharge.

CONCLUSIONS

Adult-onset encephalitis was more common and the patients older in easternmost Finland than previously reported in other parts of the country. TBE, HSV-1, and VZV are the most commonly identified specific aetiologies whereas a fifth of the cases are probably caused by autoimmunity. Prognosis depended on aetiology but was very good in the majority of cases.

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.

Biting Back: Advances in Fighting Ticks and Understanding Tick-Borne Pathogens

Ticks are blood-feeding arthropods and obligate ectoparasites of virtually all animal species (except fish) and humans [...].

Crowdsourced tick observation data from across 60 years reveals major increases and northwards shifts in tick contact areas in Finland

There is mounting evidence of increases in tick (Acari: Ixodidae) contacts in Finland during the past few decades, highlighted by increases in the incidence of Lyme borreliosis and tick-borne encephalitis (TBE). While nationwide field studies to map distributions of ticks are not feasible, crowdsourcing provides a comprehensive method with which to assess large-scale changes in tick contact areas. Here, we assess changes in tick contact areas in Finland between 1958 and 2021 using three different nationwide crowdsourced data sets. The data revealed vast increases in tick contact areas, with ticks estimated to be contacted locally approximately 400 km further north in western and approximately 100 km further north in eastern Finland in 2021 than 1958. Tick contact rates appeared to be highest along the coastline and on the shores of large lakes, possibly indicating higher tick abundance therein. In general, tick observations per inhabitant increased from 2015 to 2021. Tick contact areas have expanded in Finland over the past 60 years. It appears that taiga ticks (Ixodes persulcatus) are behind most of the northwards shifts in tick contact areas, with Ixodes ricinus contributing mostly to new contact areas in the south. While ticks are now present in most of Finland, there are still areas where tick abundance is low and/or establishment not possible, mainly in northern Finland.

Molecular detection of pathogens from ticks collected from dogs and cats at veterinary clinics in Finland

BACKGROUND

Ticks carry microbes, some of which are pathogenic for humans and animals. To assess this One Health challenge, 342 ticks were collected from pet dogs and cats at 10 veterinary clinics in Finland as part of the European project "Protect Our Future Too".

METHODS

The tick species were identified, and ticks were screened with quantitative PCR (qPCR) for tick-borne pathogens, including Borrelia burgdorferi sensu lato, Borrelia miyamotoi, Ehrlichia canis, Anaplasma spp., Candidatus Neoehrlichia mikurensis, tick-borne encephalitis virus (TBEV), and Babesia spp. For comparison, a subset of tick DNA (20 qPCR-positive samples) was analysed with 16S next-generation sequencing (NGS).

RESULTS

Most ticks were Ixodes ricinus (289, 84.5%), followed by Ixodes persulcatus (51, 14.9%). One hybrid tick (I. ricinus/I. persulcatus, 0.3%) and one Rhipicephalus sanguineus tick (0.3%) were identified. We found one or more of the analysed pathogens in 17% (59/342) of the ticks. The most prevalent pathogen was B. burgdorferi s.l. (36, 10.5%), followed by Anaplasma phagocytophilum (12, 3.5%), B. miyamotoi (5, 1.5%), Babesia venatorum (4, 1.2%), and TBEV (1, 0.3%). Candidatus Neoehrlichia mikurensis DNA was amplified from three (0.9%) ticks. Ehrlichia canis was not detected. In the 16S NGS, six samples produced enough reads for the analysis. In these six samples, we confirmed all the positive qPCR findings of Borrelia spp. and Ca. N. mikurensis.

CONCLUSIONS

The high prevalence of pathogenic microorganisms in the ticks of this study emphasizes the importance of awareness of ticks and tick-borne diseases and prevention. Furthermore, the results show that veterinary surveillance can facilitate early detection of tick-borne pathogens and new tick species and draw attention to possible co-infections that should be considered both in symptomatic humans and animals after tick bites.

Voles, shrews and red squirrels as sources of tick blood meals and tick-borne pathogens on an island in southwestern Finland

Molecular identification of the previous blood meal source of a questing tick (Acari: Ixodidae) from blood meal fragments was proposed a few decades ago. Following this, several blood meal assays have been developed and published, but none of them have been taken into widespread use. Recently, novel retrotransposon-based qPCR assays designed for detecting blood meal fragments of North American host species were published. We wanted to assess their function with host species present in Finland. Questing ticks were collected by cloth dragging in August-September 2021 from an island in southwestern Finland. DNA was extracted from Ixodes ricinus nymphs (n=438) and qPCR assays applied to identify larval blood meal sources (voles, shrews and red squirrels) and screen for several tick-borne human pathogens and other microbes with pathogenic potential [Borrelia spp. (including specific assays for Borrelia afzelii, Borrelia garinii, Borrelia valaisiana), Anaplasma phagocytophilum, Babesia spp., Rickettsia spp., and Neoehrlichia mikurensis]. The probability of a nymph having fed as larva on either a vole, shrew or red squirrel was 0.34 (0.30 - 0.38; 95% confidence interval). Bacteria of the genus Borrelia were the most common pathogens detected, with host-specific probabilities of carrying Borrelia of 0.30 (0.18 - 0.44) for nymphs that had fed on voles, 0.23 (0.14 - 0.35) for nymphs that had fed on shrews, and 0.42 (0.28 - 0.58) for nymphs that had fed on red squirrels. Other microbes were rarely acquired from these hosts, apart from N. mikurensis from voles. This study highlights that shrews and red squirrels may equal voles as blood meal sources for I. ricinus larvae. Overall, variation in proportions of blood meals provided by these animals may be high across even proximate study areas. All studied host species appeared to be important sources for particularly Borrelia afzelii, and voles also for N. mikurensis.

The AxBioTick Study: Borrelia Species and Tick-Borne Encephalitis Virus in Ticks, and Clinical Responses in Tick-Bitten Individuals on the Aland Islands, Finland

The AxBioTick study was initiated to investigate the prevalence of ticks and tick-borne pathogens and their impact on antibody and clinical responses in tick-bitten individuals on the Aland Islands. This geographical area is hyperendemic for both Lyme borreliosis (LB) and Tick-borne encephalitis (TBE). Blood samples and ticks were collected from 100 tick-bitten volunteers. A total of 425 ticks was collected, all determined to Ixodes ricinus using molecular tools. Of them 20% contained Borrelia species, of which B. garinii and B. afzelii were most common. None contained the TBE virus (TBEV). Blood samples were drawn in conjunction with the tick bite, and eight weeks later. Sera were analyzed for Borrelia- and TBEV-specific antibodies using an ELISA and a semiquantitative antibody assay. In total 14% seroconverted in Borrelia C6IgG1, 3% in TBEV IgG, and 2% in TBEV IgM. Five participants developed clinical manifestations of LB. The high seroprevalence of both Borrelia (57%) and TBEV (52%) antibodies are likely attributed to the endemic status of the corresponding infections as well as the TBE vaccination program. Despite the similar prevalence of Borrelia spp. detected in ticks in other parts of Europe, the infection rate in this population is high. The AxBioTick study is continuing to investigate more participants and ticks for co-infections, and to characterize the dermal immune response following a tick bite.

Borrelia miyamotoi: A Comprehensive Review

Borrelia miyamotoi is an emerging tick-borne pathogen in the Northern Hemisphere and is the causative agent of Borrelia miyamotoi disease (BMD). Borrelia miyamotoi is vectored by the same hard-bodied ticks as Lyme disease Borrelia, yet phylogenetically groups with relapsing fever Borrelia, and thus, has been uniquely labeled a hard tick-borne relapsing fever Borrelia. Burgeoning research has uncovered new aspects of B. miyamotoi in human patients, nature, and the lab. Of particular interest are novel findings on disease pathology, prevalence, diagnostic methods, ecological maintenance, transmission, and genetic characteristics. Herein, we review recent literature on B. miyamotoi, discuss how findings adapt to current Borrelia doctrines, and briefly consider what remains unknown about B. miyamotoi.

Does environmental adaptation or dispersal history explain the geographical distribution of Ixodes ricinus and Ixodes persulcatus ticks in Finland?

In Finland, the distribution area of the taiga tick, Ixodes persulcatus (Schulze, 1930), is nested within a broader area of distribution of a congeneric species, the sheep tick, Ixodes ricinus (Linnaeus, 1758) (Acari: Ixodidae). We assess whether distinct environmental adaptations or dispersal history provides a more parsimonious explanation for the differences in the distributions of the two common and medically important ixodids in Finland. We used an innovative spatially constrained randomization procedure to analyze whether crowdsourced occurrence data points of the two tick species had statistically different associations with any of the 28 environmental variables. Using points of presence in a region of species co-occurrence, we built Maxent models to examine whether environmental factors or dispersal history could explain the absence of I. persulcatus in a part of the range of I. ricinus in Finland. Five environmental variables-number of inhabitants, road length, elevation above sea level, proportion of barren bedrock and boulders, and proportion of unsorted glacial deposits-were significant at p ≤ .05, indicating greater between-species difference in original than in the randomized data. Of these variables, only the optimum value for unsorted glacial deposits was higher for I. persulcatus than for I. ricinus. Maxent models also predicted high relative habitat suitability (suitability >80%) for I. persulcatus south of its current, sharply bounded distribution range, suggesting that the species has not fulfilled its distribution potential in Finland. The two most common and medically relevant ixodids in Finland may colonize habitats with different environmental conditions. On the contrary, the recent establishment and ongoing dispersion of I. persulcatus in Fennoscandia rather than environmental conditions cause the southernmost distribution limit of the species in Finland.

Pathogens in Ixodes persulcatus and Ixodes ricinus ticks (Acari, Ixodidae) in Karelia (Russia)

Ixodid ticks (Acarina, Ixodidae) are vectors of dangerous human infections. The main tick species that determine the epidemiological situation for tick-borne diseases in northern Europe are Ixodes ricinus and Ixodes persulcatus. In recent years, significant changes in the number and distribution of these species have been observed, accompanied by an expansion of the sympatric range. This work summarizes the data of long-term studies carried out in Karelia since 2007 on the infection of I. persulcatus and I. ricinus ticks with various pathogens, including new viruses with unclear pathogenic potential. As a result, tick-borne encephalitis virus (TBEV, Siberian genotype), Alongshan virus, several representatives of the family Phenuiviridae, Borrelia afzelii, Borrelia garinii, Ehrlichia muris, Candidatus Rickettsia tarasevichiae and Candidatus Lariskella arthropodarum were identified. Data were obtained on the geographical and temporal variability of tick infection rates with these main pathogens. The average infection rates of I. persulcatus with TBEV and Borrelia burgdorferi sensu lato were 4.4% and 23.4% and those of I. ricinus were 1.1% and 11.9%, respectively. We did not find a correlation between the infection rate of ticks with TBEV, B. burgdorferi s.l. and Ehrlichia muris/chaffeensis with the sex of the vector. In general, the peculiarities of the epidemiological situation in Karelia are determined by the wide distribution and high abundance of I. persulcatus ticks and by their relatively high infection rate with TBEV and B. burgdorferi s.l. in most of the territory, including the periphery of the range.

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: Ixodes ricinus and Ixodes persulcatus. 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.

Epidemiology of Ticks and Tick-Borne Pathogens in Domestic Ruminants across Southern African Development Community (SADC) Region from 1980 until 2021: A Systematic Review and Meta-Analysis

Ticks are hematophagous ectoparasites that are capable of infesting a wide range of mammals, including domestic animals, ruminants, wildlife, and humans across the world, and they transmit disease-causing pathogens. Numerous individual epidemiological studies have been conducted on the distribution and prevalence of ticks and tick-borne diseases (TBDs) in the Southern African Developing Community (SADC) region, but no effort has been undertaken to synchronize findings, which would be helpful in the implementation of consolidated tick control measures. With the aim of generating consolidated pooled prevalence estimates of ticks and TBDs in the SADC region, we performed a systematic review and meta-analysis of published articles using the PRISMA 2020 guidelines. A deep search was performed on five electronic databases, namely, PubMed, ScienceDirect, Google Scholar, AJOL, and Springer Link. Of the 347 articles identified, only 61 of the articles were eligible for inclusion. In total, 18,355 tick specimens were collected, belonging to the genera Amblyomma, Haemaphysalis, Hyalomma, and Rhipicephalus (including Boophilus) across several countries, including South Africa (n = 8), Tanzania (n = 3), Zambia (n = 2), Zimbabwe (n = 2), Madagascar (n = 2), Angola (n = 2), Mozambique (n = 1), and Comoros (n = 1). The overall pooled prevalence estimate (PPE) of TBPs in livestock was 52.2%, with the highest PPE in cattle [51.2%], followed by sheep [45.4%], and goats [29.9%]. For bacteria-like and rickettsial TBPs, Anaplasma marginale had the highest PPE of 45.9%, followed by A. centrale [14.7%], A. phagocytophilum [2.52%], and A. bovis [0.88%], whilst Ehrlichia ruminantium had a PPE of 4.2%. For piroplasmids, Babesia bigemina and B. bovis had PPEs of 20.8% and 20.3%, respectively. Theileria velifera had the highest PPE of 43.0%, followed by T. mutans [29.1%], T. parva [25.0%], and other Theileria spp. [14.06%]. Findings from this study suggest the need for a consolidated scientific approach in the investigation of ticks, TBPs, and TBDs in the whole SADC region, as most of the TBDs are transboundary and require a regional control strategy.

The impact of climatic factors on tick-related hospital visits and borreliosis incidence rates in European Russia

Tick-borne diseases are among the challenges associated with warming climate. Many studies predict, and already note, expansion of ticks' habitats to the north, bringing previously non-endemic diseases, such as borreliosis and encephalitis, to the new areas. In addition, higher temperatures accelerate phases of ticks' development in areas where ticks have established populations. Earlier works have shown that meteorological parameters, such as temperature and humidity influence ticks' survival and define their areas of habitat. Here, we study the link between climatic parameters and tick-related hospital visits as well as borreliosis incidence rates focusing on European Russia. We have used yearly incidence rates of borreliosis spanning a period of 20 years (1997-2016) and weekly tick-related hospital visits spanning two years (2018-2019). We identify regions in Russia characterized by similar dynamics of incidence rates and dominating tick species. For each cluster, we find a set of climatic parameters that are significantly correlated with the incidence rates, though a linear regression approach using exclusively climatic parameters to incidence prediction was less than 50% effective. On a weekly timescale, we find correlations of different climatic parameters with hospital visits. Finally, we trained two long short-term memory neural network models to project the tick-related hospital visits until the end of the century, under the RCP8.5 climate scenario, and present our findings in the evolution of the tick season length for different regions in Russia. Our results show that the regions with an expected increase in both tick season length and borreliosis incidence rates are located in the southern forested areas of European Russia. Oppositely, our projections suggest no prolongation of the tick season length in the northern areas with already established tick population.

Co-infections with multiple pathogens in natural populations of Ixodes persulcatus ticks in Mongolia

Background

In Mongolia, the taiga tick Ixodes persulcatus is the major vector of tick-borne pathogens. Knowledge about co-infections of these pathogens in ticks is necessary both for understanding their persistence in nature and for diagnosing and treating tick-borne diseases.

Methods

The prevalence of seven tick-borne infections in 346 I. persulcatus collected from the Selenge and Bulgan provinces of Mongolia was evaluated using real-time PCR. Quantification of Borrelia spp. was performed using multiplex quantitative PCR targeting the 16S rRNA gene. Genetic analysis of Borrelia spp. in 11 ticks infected with Borrelia miyamotoi, including six ticks co-infected with Borrelia burgdorferi sensu lato (s.l.), was performed by high-throughput sequencing of the flaB gene fragment.

Results

Six ticks (1.7%) were infected with tick-borne encephalitis virus (TBEV); 171 (49.4%), with B. burgdorferi sensu lato; 17 (4.9%), with B. miyamotoi; 47 (13.6%), with Anaplasma phagocytophilum; and 56 (16.2%), with Ehrlichia sp. Neither Rickettsia sibirica nor R. heilongjiangensis were detected. Borrelia burgdorferi s.l. occurred as co-infection in 55 (32.2%) of all infected ticks. The other pathogens co-infected ticks in 58.8–70.2% of cases. No pairwise associations between co-infecting pathogens were observed, with the exception of a positive association between A. phagocytophilum and Ehrlichia sp. infections. The spirochete loads of B. miyamotoi were significantly higher than those of B. burgdorferi s.l. (mean: 5.2 vs 4.0 log10 genome copies/tick, respectively). Ten isolates of B. miyamotoi belonged to the Siberian lineage. Borrelia burgdorferi s.l was represented by nine isolates of B. afzelii, B. bavariensis and B. garinii.

Conclusions

In populations of I. persulcatus inhabiting the Selenge and Bulgan provinces of Mongolia, five vector-borne pathogens, i.e. TBEV, B. burgdorferi s.l., B. miyamotoi, A. phagocytophilum and Ehrlichia sp., persist independently from each other, with the exception of A. phagocytophilum and Ehrlichia sp. which seem to share the circulation mode. The discrepancies in B. burgdorferi s.l. and B. miyamotoi prevalence and spirochete load per tick suggest that different ecological niches are occupied by Lyme disease and relapsing fever agents. High-throughput sequencing allows genetic identification of borreliae species in co-infected ticks.

Graphical Abstract

Differentiation of Laboratory-Obtained Ixodes ricinus × Ixodes persulcatus Hybrid Ticks: Selection of Suitable Genes

Ixodes ricinus and Ixodes persulcatus ticks are the main vectors of tick-borne encephalitis virus and some bacterial pathogens. The regions where these tick species live overlap, forming large sympatric areas. It has previously been shown that these tick species have no morphological barrier, and interspecies crossing is possible with the appearance of sterile hybrids. It has also been shown that hybrid larvae and nymphs can be differentiated using discriminant functions based on a set of morphological features. However, such an approach is laborious and rather ineffective with adult ticks, making a molecular approach necessary. In the current work, we tested the ability of different systems to differentiate laboratory-obtained hybrid ticks. Our data suggest that commonly used primer sets that target rRNA are unsuitable for hybrid tick determination, likely due to the rRNA region being linked with the X chromosome in I. ricinus and I. persulcatus ticks. We tested several primer sets targeting different non rRNA genes to assess their ability to determine hybrids. The best primer set, Toll_R, targeting the putative Toll gene, showed little to no bias when used for DNA amplification from hybrid ticks. Thus, Toll gene can be further used for hybrid detection.

The influence of local environmental factors in southwestern Poland on the abundance of Ixodes ricinus and prevalence of infection with Borrelia burgdorferi s.l. and B. miyamotoi

Ticks are important ectoparasites and vectors of pathogens that cause disease in humans and animals. The natural habitat of Ixodes ricinus ticks is forests, which are convenient habitats to search for hosts, including reservoir hosts, and therefore can be an important habitat source of tick-borne pathogens. The aim of the study was to assess the usefulness of detailed forest habitat-type maps to estimate the tick-borne risk at a local scale (Lower Silesia, SW Poland). For the purposes of estimating tick abundance, we used the land cover maps available from the Forest Data Bank. For I. ricinus collection, nine sites located in three forest habitat types were chosen: broadleaf forest, mixed broadleaf and coniferous forest and coniferous forest. Ticks were collected once a month from April to June 2018 and 2019 using the standard flagging method. At each of the nine sites, ticks were collected in four plots, of 100 m² each. Tick abundance was analysed using general linear mixed models (GLMM). A total of 2196 (10.1/100 m²) ticks were collected, including 2093 Ixodes ricinus (95.3%; 9.6/100 m²), 46 Dermacentor reticulatus (2.1%; 0.2/100 m²) and 57 Haemaphysalis concinna (2.6%; 0.3/100 m²). Among the collected I. ricinus were 589 larvae (28.1%; 2.7/100 m²), 1261 nymphs (60.3%; 5.8/100 m²), 128 females (6.1%; 0.6/100 m²) and 115 males (5.5%; 0.5/100 m²). We found a highly significant effect of forest habitat type on the density of ticks for broadleaf forest (coefficient = 1.87267, p-value = 2.79e - 07). Additionally, a significant influence of air temperature and relative humidity on the abundance of ticks was observed. During spring, the peak activity of I. ricinus was recorded in May and June. For DNA amplification of Borrelia burgdorferi s.l., a nested PCR method was used. Out of 494 I. ricinus, 83 (16.8%) were positive for Borrelia spp. The RFLP method showed the occurrence of five species including four belonging to the B. burgdorferi s.l. complex: B. afzelii (30.1%), B. garinii (38.6%), B. valaisiana (2.4%) and B. lusitaniae (18.1%). Furthermore, B. miyamotoi (9.6%), a species belonging to bacteria that cause relapsing fever as well as co-infection of B. miyamotoi/B.lusitaniae (1.2%) were found. The differences in the infection level of Borrelia spp. between broadleaf forest and mixed broadleaf and coniferous forest were statistically significant.

The Ixodes scapularis Symbiont Rickettsia buchneri Inhibits Growth of Pathogenic Rickettsiaceae in Tick Cells: Implications for Vector Competence

Ixodes scapularis is the primary vector of tick-borne pathogens in North America but notably does not transmit pathogenic Rickettsia species. This tick harbors the transovarially transmitted endosymbiont Rickettsia buchneri, which is widespread in I. scapularis populations, suggesting that it confers a selective advantage for tick survival such as providing essential nutrients. The R. buchneri genome includes genes with similarity to those involved in antibiotic synthesis. There are two gene clusters not found in other Rickettsiaceae, raising the possibility that these may be involved in excluding pathogenic bacteria from the tick. This study explored whether the R. buchneri antibiotic genes might exert antibiotic effects on pathogens associated with I. scapularis. Markedly reduced infectivity and replication of the tick-borne pathogens Anaplasma phagocytophilum, R. monacensis, and R. parkeri were observed in IRE11 tick cells hosting R. buchneri. Using a fluorescent plate reader assay to follow infection dynamics revealed that the presence of R. buchneri in tick cells, even at low infection rates, inhibited the growth of R. parkeri by 86-100% relative to R. buchneri-free cells. In contrast, presence of the low-pathogenic species R. amblyommatis or the endosymbiont R. peacockii only partially reduced the infection and replication of R. parkeri. Addition of host-cell free R. buchneri, cell lysate of R. buchneri-infected IRE11, or supernatant from R. buchneri-infected IRE11 cultures had no effect on R. parkeri infection and replication in IRE11, nor did these treatments show any antibiotic effect against non-obligate intracellular bacteria E. coli and S. aureus. However, lysate from R. buchneri-infected IRE11 challenged with R. parkeri showed some inhibitory effect on R. parkeri infection of treated IRE11, suggesting that challenge by pathogenic rickettsiae may induce the antibiotic effect of R. buchneri. This research suggests a potential role of the endosymbiont in preventing other rickettsiae from colonizing I. scapularis and/or being transmitted transovarially. The confirmation that the observed inhibition is linked to R. buchneri's antibiotic clusters requires further investigation but could have important implications for our understanding of rickettsial competition and vector competence of I. scapularis for rickettsiae.

Ticks (Acari: Ixodidae) parasitizing migrating and local breeding birds in Finland

Ticks are globally renowned vectors for numerous zoonoses, and birds have been identified as important hosts for several species of hard ticks (Acari: Ixodidae) and tick-borne pathogens. Many European bird species overwinter in Africa and Western Asia, consequently migrating back to breeding grounds in Europe in the spring. During these spring migrations, birds may transport exotic tick species (and associated pathogens) to areas outside their typical distribution ranges. In Finland, very few studies have been conducted regarding ticks parasitizing migrating or local birds, and existing data are outdated, likely not reflecting the current situation. Consequently, in 2018, we asked volunteer bird ringers to collect ticks from migrating and local birds, to update current knowledge on ticks found parasitizing birds in Finland. In total 430 ticks were collected from 193 birds belonging to 32 species, caught for ringing between 2018 and 2020. Furthermore, four Ixodes uriae were collected from two roosting islets of sea birds in 2016 and 2020. Ticks collected on birds consisted of: Ixodes ricinus (n = 421), Ixodes arboricola (4), Ixodes lividus (2) and Hyalomma marginatum (3). Ixodes ricinus loads (nymphs and larvae) were highest on thrushes (Passeriformes: Turdidae) and European robins (Erithacus rubecula). The only clearly imported exotic tick species was H. marginatum. This study forms the second report of both I. uriae and I. arboricola from Finland, and possibly the northernmost observation of I. arboricola from Europe. The importation of exotic tick species by migrating birds seems a rare occurrence, as over 97% of all ticks collected from birds arriving in Finland during their spring migrations were I. ricinus, a species native to and abundant in Finland.

The specificity of Babesia-tick vector interactions: recent advances and pitfalls in molecular and field studies

Background

Babesia spp. are protozoan parasites of great medical and veterinary importance, especially in the northern Hemisphere. Ticks are known vectors of Babesia spp., although some Babesia-tick interactions have not been fully elucidated.

Methods

The present review was performed to investigate the specificity of Babesia-tick species interactions that have been identified using molecular techniques in studies conducted in the last 20 years under field conditions. We aimed to indicate the main vectors of important Babesia species based on published research papers (n = 129) and molecular data derived from the GenBank database.

Results

Repeated observations of certain Babesia species in specific species and genera of ticks in numerous independent studies, carried out in different areas and years, have been considered epidemiological evidence of established Babesia-tick interactions. The best studied species of ticks are Ixodes ricinus, Dermacentor reticulatus and Ixodes scapularis (103 reports, i.e. 80% of total reports). Eco-epidemiological studies have confirmed a specific relationship between Babesia microti and Ixodes ricinus, Ixodes persulcatus, and Ixodes scapularis and also between Babesia canis and D. reticulatus. Additionally, four Babesia species (and one genotype), which have different deer species as reservoir hosts, displayed specificity to the I. ricinus complex. Eco-epidemiological studies do not support interactions between a high number of Babesia spp. and I. ricinus or D. reticulatus. Interestingly, pioneering studies on other species and genera of ticks have revealed the existence of likely new Babesia species, which need more scientific attention. Finally, we discuss the detection of Babesia spp. in feeding ticks and critically evaluate the data on the role of the latter as vectors.

Conclusions

Epidemiological data have confirmed the specificity of certain Babesia-tick vector interactions. The massive amount of data that has been thus far collected for the most common tick species needs to be complemented by more intensive studies on Babesia infections in underrepresented tick species.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05019-3.

Estimation of Ixodes ricinus (Acari: Ixodidae) Populations of Kaylaka Park in the Town of Pleven, Bulgaria

(1) Background: Ticks are vectors of a large number of pathogenic microorganisms, which cause serious diseases in both humans and animals. Kaylaka Park is located in northern Bulgaria close to the city of Pleven. Part of the park is urbanized and visited daily by many citizens. The aim of our study was to determine the presence and distribution of hard ticks in the park area by surveying and comparing four urbanized with four wild areas. (2) Methods: Ticks were collected by flagging from 2016 to 2020 during the spring-summer season (March-July). Air temperature, relative humidity, collection time and flagging area were measured during the campaign. (3) Results: A total of 622 ticks were collected: 285 females (46%), 272 (44%) males and 64 (10%) nymphs. All were identified as Ixodes ricinus. Wild areas showed statistically significant higher values of ticks collected per minute (p = 0.009) and nymph densities (p = 0.003) compared to urbanized sampling sites. Other densities indices did not have a significant difference between urban and wild areas. Highest numbers of Ixodes ticks were collected at a temperature of 20 °C and at 60% relative humidity. The active questing began in March, peaked in end of April and declined in June. (4) Conclusions: In the present study, we found that ecological factors in the Kaylaka Park area are favourable for the development and distribution of tick populations. The results give us reason to consider that there is a high risk to visitors from tick bites in the Kaylaka Park area.

Absence of Francisella tularensis in Finnish Ixodes ricinus and Ixodes persulcatus ticks

Francisella tularensis subsp. holarctica is the causative agent of tularaemia in Europe. Finland is a high-incidence region for tularaemia, with mosquito bites as the most common sources of infection. However, in Central and Western Europe, ticks (Acari: Ixodidae) have been suggested as the main vectors. Indeed, several studies have reported the pathogen from the locally most common human-biting tick species, Ixodes ricinus. In Finland, the occurrence of the pathogen in ticks has started receiving attention only recently. Here, we collate previous tick screening data from Finland regarding F. tularensis as well as present the results from a novel screening of roughly 15 000 I. ricinus and I. persulcatus collected from across the country. In total, 14 878 ticks collected between 2015 and 2020 were screened for F. tularensis using a TaqMan-based qPCR assay targeting the 23 KDa gene. The combined screening efforts of the current and previous studies, encompassing roughly 20 000 ticks, did not find any positive ticks. Given the negative results despite the considerable sample size, it appears that the pathogen is not circulating in local tick populations in Finland. We discuss some possible reasons for the lack of the bacterium in ticks in this high-incidence region of tularaemia.

Assessing the Need for Multiplex and Multifunctional Tick-Borne Disease Test in Routine Clinical Laboratory Samples from Lyme Disease and Febrile Patients with a History of a Tick Bite

Human polymicrobial infections in tick-borne disease (TBD) patients is an emerging public health theme. However, the requirement for holistic TBD tests in routine clinical laboratories is ambiguous. TICKPLEX® PLUS is a holistic TBD test utilized herein to assess the need for multiplex and multifunctional diagnostic tools in a routine clinical laboratory. The study involved 150 specimens categorized into Lyme disease (LD)-positive (n = 48), LD-negative (n = 30), and febrile patients from whom borrelia serology was requested (n = 72, later "febrile patients") based on reference test results from United Medix, Finland. Reference tests from DiaSorin, Immunetics, and Mikrogen Diagnostik followed the two-tier LD testing system. A comparison between the reference tests and TICKPLEX® PLUS produced 86%, 88%, and 87% positive, negative, and overall agreement, respectively. Additionally, up to 15% of LD and 11% of febrile patients responded to TBD related coinfections and opportunistic microbes. The results demonstrated that one (TICKPLEX® PLUS) test can aid in a LD diagnosis instead of four tests. Moreover, TBD is not limited to just LD, as the specimens produced immune responses to several TBD microbes. Lastly, the study indicated that the screening of febrile patients for TBDs could be a missed opportunity at reducing unreported patient cases.

Global Distribution of Babesia Species in Questing Ticks: A Systematic Review and Meta-Analysis Based on Published Literature

Babesiosis caused by the Babesia species is a parasitic tick-borne disease. It threatens many mammalian species and is transmitted through infected ixodid ticks. To date, the global occurrence and distribution are poorly understood in questing ticks. Therefore, we performed a meta-analysis to estimate the distribution of the pathogen. A deep search for four electronic databases of the published literature investigating the prevalence of Babesia spp. in questing ticks was undertaken and obtained data analyzed. Our results indicate that in 104 eligible studies dating from 1985 to 2020, altogether 137,364 ticks were screened with 3069 positives with an estimated global pooled prevalence estimates (PPE) of 2.10%. In total, 19 different Babesia species of both human and veterinary importance were detected in 23 tick species, with Babesia microti and Ixodesricinus being the most widely reported Babesia and tick species, respectively. Regardless of species, adult ticks with 2.60% had the highest infection rates, while larvae had the least with 0.60%. Similarly, female ticks with 4.90% were infected compared to males with 3.80%. Nested-polymerase chain reaction (PCR) 2.80% had the highest prevalence among the molecular techniques employed. In conclusion, results obtained indicate that Babesia species are present in diverse questing tick species at a low prevalence, of which some are competent vectors.

One out of ten: low sampling efficiency of cloth dragging challenges abundance estimates of questing ticks

Hard ticks (Acari: Ixodidae) act as important vectors of zoonotic pathogens. For instance, Borrelia burgdorferi s.l. spirochetes pose a severe health risk as aetiological agents of Lyme borreliosis. Commonly, to study the abundance of questing (host-seeking) ticks, a 1 m² piece of cloth is dragged over vegetation for a determined distance. Here, we designed a tick-sampling study to estimate the sampling efficiency of this standard method. We established 10 m dragging transects in a hemiboreal mixed forest patch in SW Finland for a 5-day monitoring period. Five of the transects were cloth-dragged 3× a day, whereas another five transects were dragged 6× a day in a manner that after each morning, midday and afternoon dragging, a second dragging was conducted on the same transect immediately. Captured Ixodes ricinus ticks were subsequently analysed for tick-borne pathogens. The initial population size of nymphal ticks on a transect was approximated by the accumulated nymph catch from the dragging sessions. The sampling efficiency of the cloth dragging was low, as a single dragging in a previously untouched vegetation strip always caught less than 12% (mean 6%) of the estimated population of active nymphs that were assumed to be questing during the study. Clear results were not found for daily activity rhythm, as ticks were caught in all daily dragging sessions. Approximately every third nymph and every second adult carried a pathogen, but nothing indicated that the occurrence of a pathogen affected the likelihood of the tick being caught by cloth dragging. Our results suggest that only a minority of active ticks can be caught by a single cloth dragging. The abundance estimates in many tick investigations might thus be downward biased.

Baltic Group Tick-Borne Encephalitis Virus Phylogeography: Systemic Inconsistency Pattern between Genetic and Geographic Distances

Tick-Borne Encephalitis Virus (TBEV) is a dangerous arbovirus widely distributed in Northern Eurasia. The area of this pathogen changes over time. At the beginning of the 2000s, the Ixodes tick populations in Karelia increased. At the same time, the area of I. persulcatus, the main vector of the Siberian TBEV subtype, also expanded. Herein, we sequenced 10 viruses isolated from ticks collected in three locations from the Karelia region in 2008-2018. PCR positive samples were passaged in suckling mice or pig embryo kidney cells (PEK). After the second passage in suckling, mice viral RNA was isolated and E-gene fragment was sequenced. Viral sequences were expected to be similar or nearly identical. Instead, there was up to a 4.8% difference in nucleotide sequence, comparable with the most diverse viruses belonging to the Baltic subgroup in Siberian TBEV subtype (Baltic TBEV-Sib). To reveal whether this was systemic or incidental, a comprehensive phylogeographical analysis was conducted. Interestingly, viruses within each geographic region demonstrated comparable diversity to the whole Baltic TBEV-Sib. Moreover, Baltic TBEV-Sib has a distribution area limited by three ecological regions. This means that active virus mixing occurs in the vast geographic area forming one common virus pool. The most plausible explanation is the involvement of flying animals in the TBEV spread.

Enhanced threat of tick-borne infections within cities? Assessing public health risks due to ticks in urban green spaces in Helsinki, Finland

Most tick‐related studies in Europe have been conducted in nonurban areas, but ticks and tick‐borne pathogens also occur in urban green spaces. From a public health perspective, risks regarding tick‐borne infections should be studied in these urban areas, where contacts between infected ticks and humans may be more frequent than elsewhere, due to high human activity. We examined the risk of encountering an infected tick in urban green spaces in Helsinki, Finland. We collected ticks at nine sites throughout Helsinki, recorded the prevalence of several pathogens and identified areas with a high potential for contacts between infected ticks and humans. Moreover, we explored the relationship between the density of Borrelia burgdorferi sensu lato‐infected ticks and locally diagnosed cases of borreliosis and compared the potential for human‐tick encounters in Helsinki to those in nonurban areas in south‐western Finland. During 34.8 km of cloth dragging, 2,417 Ixodes ricinus were caught (402 adults, 1,399 nymphs and 616 larvae). From analysed nymphs, we found 11 distinct tick‐borne pathogens, with 31.5% of nymphs carrying at least one pathogen. Tick activity was highest in August and September, leading to the density of nymphs infected with B. burgdorferi s.l., and concurrently infection risk, to also be highest during this time. Nymph densities varied between the sampling sites, with obvious implications to spatial variation in infection risk. While ticks and tick‐borne pathogens were found in both Helsinki and nonurban areas in south‐western Finland, the estimates of human activity were generally higher in urban green spaces, leading to a higher potential for human‐tick contacts therein. The presence of ticks and tick‐borne pathogens and high local human activity in urban green spaces suggest that they form potential foci regarding the acquisition of tick‐borne infections. Risk areas within cities should be identified and knowledge regarding urban ticks increased.