Publications by authors named "Hein Sprong"

179 Publications

No molecular detection of tick-borne pathogens in the blood of patients with erythema migrans in Belgium.

Parasit Vectors 2022 Jan 20;15(1):27. Epub 2022 Jan 20.

Centre for Infectious Disease Control, National Institute for Public Health and Environment (RIVM), Bilthoven, The Netherlands.

Background: A number of tick-borne pathogens circulate in the Belgian tick population in addition to the causative agent of Lyme borreliosis. However, so far, only a few patients with tick-borne diseases other than Lyme borreliosis have been reported in Belgium. The aim of this study was to investigate the occurrence of other human tick-borne infections in Belgium and their possible clinical manifestation.

Methods: Patients with fever (> 37.5 °C) after a tick bite or those with erythema migrans (EM) were included in the study. EDTA-blood samples were screened for the presence of DNA from Borrelia burgdorferi sensu lato, Borrelia miyamotoi, Anaplasma phagocytophilum, Neoehrlichia mikurensis, spotted fever group rickettsiae (genus Rickettsia), Babesia spp., Bartonella spp., Spiroplasma ixodetis and tick-borne encephalitis virus, using multiplex PCR methods. A questionnaire on, among others, demographics and clinical symptoms, was also filled in.

Results: Over a period of 3 years, 119 patients with EM and 14 patients with fever after a recent tick bite were enrolled in the study. Three samples initially tested positive for N. mikurensis by quantitative PCR (qPCR), but the results could not be confirmed by other PCR methods, and repetition of the DNA extraction procedure and qPCR test was not successful. The qPCR test results for the other tick-borne pathogens were negative.

Conclusions: In general, only a few patients with fever after a tick bite could be identified. Although no tick-borne pathogens were detected, their occurrence cannot be excluded based on the limited number of patients and the limitations inherent to current methodologies. This study underscores the possibility of false-positive PCR results and the necessity for the development of multiple independent tools for the sensitive and specific detection of emerging tick-borne pathogens.
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http://dx.doi.org/10.1186/s13071-021-05139-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8772185PMC
January 2022

The Genetic Diversity of Rickettsiella Symbionts in Ixodes ricinus Throughout Europe.

Microb Ecol 2021 Sep 28. Epub 2021 Sep 28.

Centre for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), Antonie van Leeuwenhoeklaan 9, 3720 BA, Bilthoven, The Netherlands.

Rickettsiella species are bacterial symbionts that are present in a great variety of arthropod species, including ixodid ticks. However, little is known about their genetic diversity and distribution in Ixodes ricinus, as well as their relationship with other tick-associated bacteria. In this study, we investigated the occurrence and the genetic diversity of Rickettsiella spp. in I. ricinus throughout Europe and evaluated any preferential and antagonistic associations with Candidatus Midichloria mitochondrii and the pathogens Borrelia burgdorferi sensu lato and Borrelia miyamotoi. Rickettsiella spp. were detected in most I. ricinus populations investigated, encompassing a wide array of climate types and environments. The infection prevalence significantly differed between geographic locations and was significantly higher in adults than in immature life stages. Phylogenetic investigations and protein characterization disclosed four Rickettsiella clades (I-IV). Close phylogenetic relations were observed between Rickettsiella strains of I. ricinus and other arthropod species. Isolation patterns were detected for Clades II and IV, which were restricted to specific geographic areas. Lastly, although coinfections occurred, we did not detect significant associations between Rickettsiella spp. and the other tick-associated bacteria investigated. Our results suggest that Rickettsiella spp. are a genetically and biologically diverse facultative symbiont of I. ricinus and that their distribution among tick populations could be influenced by environmental components.
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http://dx.doi.org/10.1007/s00248-021-01869-7DOI Listing
September 2021

Occurrence of tick-borne pathogens in questing Ixodes ricinus ticks from Wester Ross, Northwest Scotland.

Parasit Vectors 2021 Aug 26;14(1):430. Epub 2021 Aug 26.

Institute of Terrestrial Ecosystems, Department of Environmental Systems Science, ETH Zürich, Universitätstrasse 16, 8092, Zürich, Switzerland.

Background: Lyme borreliosis and other tick-borne diseases emerge from increased interactions between humans, other animals, and infected ticks. The risk of acquiring a tick-borne infection varies across space and time, so knowledge of the occurrence and prevalence of pathogens in ticks can facilitate disease diagnosis in a specific area and the implementation of mitigation measures and awareness campaigns. Here we identify the occurrence and prevalence of several pathogens in Ixodes ricinus ticks in Wester Ross, Northwest Scotland, a region of high tourism and tick exposure, yet data-poor in terms of tick-borne pathogens.

Methods: Questing I. ricinus nymphs (n = 2828) were collected from 26 sites in 2018 and 2019 and tested for the presence of tick-borne pathogens using PCR-based methods. Prevalence was compared with other regions of Scotland, England, Wales, and the Netherlands.

Results: Anaplasma phagocytophilum (4.7% prevalence), Borrelia burgdorferi sensu lato (s.l.) (2.2%), Babesia from clade X (0.2%), Rickettsia helvetica (0.04%), and Spiroplasma ixodetis (0.4%) were detected, but no Neoehrlichia mikurensis, Borrelia miyamotoi, or Babesia microti. Typing of A. phagocytophilum using a fragment of the GroEL gene identified the presence of both ecotype I and ecotype II. Genospecies identification of Borrelia burgdorferi s.l. revealed B. afzelii (53% of infected nymphs), B. garinii (9%), B. burgdorferi sensu stricto (7%), and B. valaisiana (31%). We found similar prevalence of A. phagocytophilum in Wester Ross as in the Netherlands, but higher than in other parts of Great Britain. We found lower B. burgdorferi s.l. prevalence than in England or the Netherlands, and similar to some other Scottish studies. We found higher prevalence of B. valaisiana and lower prevalence of B. garinii than in other Scottish studies. We found S. ixodetis at much lower prevalence than in the Netherlands, and R. helvetica at much lower prevalence than in England and the Netherlands.

Conclusions: As far as we know, this is the first description of S. ixodetis in Great Britain. The results are relevant for disease surveillance and management for public and veterinary health. The findings can also aid in designing targeted public health campaigns and in raising awareness among outdoor recreationists and professionals.
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http://dx.doi.org/10.1186/s13071-021-04946-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8393815PMC
August 2021

Detection of Anaplasma phagocytophilum in European brown hares (Lepus europaeus) using three different methods.

Zoonoses Public Health 2021 Dec 11;68(8):917-925. Epub 2021 Aug 11.

CEITEC-Central European Institute of Technology, University of Veterinary Sciences Brno, Brno, Czech Republic.

European brown hare (Lepus europaeus Pallas 1778) is a broadly distributed lagomorph species in Europe, recognized as a host for Ixodes ricinus and reservoir of a wide range of pathogens with zoonotic potential. Even though Lepus europaeus represents an important game animal in Central Europe, the data available on Anaplasma phagocytophilum in this lagomorph are scarce. In this study, three populations of brown hare from distinct localities in the Czech Republic were analysed for the presence of Anaplasma phagocytophilum DNA. We used standard qPCR, targeting the msp2 gene and adapted the same assay also for digital droplet PCR. Out of 91 samples, these two methods identified 9 and 12 as positive, respectively. For taxonomic analysis, we amplified the groEL gene from five of six samples that were found positive by both methods. In phylogenetic analyses, this haplotype belongs to ecotype 1, and to the subclade with isolates from cervids and I. ricinus. Our findings underline the importance of correct result interpretation and positivity cut-off set-up for different detection methods of A. phagocytophilum. This bacterium is characterized by a high intraspecific variability and highly sensitive detection itself, is not enough. Detailed molecular typing is necessary to define the zoonotic potential of different strains and their natural reservoirs.
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http://dx.doi.org/10.1111/zph.12883DOI Listing
December 2021

Wild ungulate species differ in their contribution to the transmission of Ixodes ricinus-borne pathogens.

Parasit Vectors 2021 Jul 10;14(1):360. Epub 2021 Jul 10.

Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences, 901 83, Umeå, Sweden.

Background: Several ungulate species are feeding and propagation hosts for the tick Ixodes ricinus as well as hosts to a wide range of zoonotic pathogens. Here, we focus on Anaplasma phagocytophilum and Borrelia burgdorferi (s.l.), two important pathogens for which ungulates are amplifying and dilution hosts, respectively. Ungulate management is one of the main tools to mitigate human health risks associated with these tick-borne pathogens. Across Europe, different species of ungulates are expanding their ranges and increasing in numbers. It is currently unclear if and how the relative contribution to the life-cycle of I. ricinus and the transmission cycles of tick-borne pathogens differ among these species. In this study, we aimed to identify these relative contributions for five European ungulate species.

Methods: We quantified the tick load and collected ticks and spleen samples from hunted fallow deer (Dama dama, n = 131), moose (Alces alces, n = 15), red deer (Cervus elaphus, n = 61), roe deer (Capreolus capreolus, n = 30) and wild boar (Sus scrofa, n = 87) in south-central Sweden. We investigated the presence of tick-borne pathogens in ticks and spleen samples using real-time PCR. We determined if ungulate species differed in tick load (prevalence and intensity) and in infection prevalence in their tissue as well as in the ticks feeding on them.

Results: Wild boar hosted fewer adult female ticks than any of the deer species, indicating that deer are more important as propagation hosts. Among the deer species, moose had the lowest number of female ticks, while there was no difference among the other deer species. Given the low number of infected nymphs, the relative contribution of all ungulate species to the transmission of B. burgdorferi (s.l.) was low. Fallow deer, red deer and roe deer contributed more to the transmission of A. phagocytophilum than wild boar.

Conclusions: The ungulate species clearly differed in their role as a propagation host and in the transmission of B. burgdorferi and A. phagocytophilum. This study provides crucial information for ungulate management as a tool to mitigate zoonotic disease risk and argues for adapting management approaches to the local ungulate species composition and the pathogen(s) of concern.
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http://dx.doi.org/10.1186/s13071-021-04860-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8272276PMC
July 2021

Hedgehogs and Squirrels as Hosts of Zoonotic Species.

Pathogens 2021 Jun 1;10(6). Epub 2021 Jun 1.

Department of Parasitology, Faculty of Science, Charles University, 12800 Prague, Czech Republic.

Free-living animals frequently play a key role in the circulation of various zoonotic vector-borne pathogens. Bacteria of the genus are transmitted by blood-feeding arthropods and infect a large range of mammals. Although only several species have been identified as causative agents of human disease, it has been proposed that any species found in animals may be capable of infecting humans. Within a wide-ranging survey in various geographical regions of the Czech Republic, cadavers of accidentally killed synurbic mammalian species, namely Eurasian red squirrel (), European hedgehog () and Northern white-breasted hedgehog (), were sampled and tested for presence using multiple PCR reaction approach targeting several DNA loci. We demonstrate that cadavers constitute an available and highly useful source of biological material for pathogen screening. High infection rates of spp., ranging from 24% to 76%, were confirmed for all three tested mammalian species, and spleen, ear, lung and liver tissues were demonstrated as the most suitable for DNA detection. The wide spectrum of spp. that were identified includes three species with previously validated zoonotic potential, , and , accompanied by ' B. rudakovii' and two putative novel species, sp. ERIN and sp. SCIER.
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http://dx.doi.org/10.3390/pathogens10060686DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8229113PMC
June 2021

Pitfalls in Tick and Tick-Borne Pathogens Research, Some Recommendations and a Call for Data Sharing.

Pathogens 2021 Jun 7;10(6). Epub 2021 Jun 7.

Research Group in Emerging Zoonoses, Instituto Agroalimentario de Aragón-IA2 (Universidad de Zaragoza-CITA), 50013 Zaragoza, Spain.

An understanding of the relationships of ticks and tick-borne pathogens can only be achieved by integrating data from multiple studies. The publication of raw material is a necessary step for wide-area meta-analyses and study design, data collection and reporting require harmonization. This is an opinion paper, not a consensus position, and is open to debate. This work reflects our view about how data should be communicated in mainstream journals. We indicate rules that should be observed in recording weather data, to avoid serendipitous correlations between the density of ticks and climate variables and recommend the inclusion of raw data in reports. We stress the need for standardized methods to collect ticks that cannot be obtained by standard flagging. The reporting of infection rates of pathogens in ticks should avoid conclusions based on pure molecular findings in feeding ticks. Studies demonstrating the vectorial capacity of ticks should not be supported only by molecular surveys of feeding ticks. Vacuous conclusions about vectorial or reservoir status based solely on the finding of genomic material of a pathogen should be discouraged. We stress that phylogenetic studies based on random selection of sequences from GenBank are unsuitable. We firmly support the development of a dedicated server of curated sequences of ticks and pathogens as a standard for future studies.
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http://dx.doi.org/10.3390/pathogens10060712DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8229135PMC
June 2021

Imported Hyalomma ticks in the Netherlands 2018-2020.

Parasit Vectors 2021 May 7;14(1):244. Epub 2021 May 7.

Centre for Infectious Disease Control (CIb), National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands.

Background: Ticks of the genus Hyalomma, which are vectors for several tick-borne diseases, are occasionally found in areas outside their endemic range including northern parts of Europe. The objective of this study was to analyse adult Hyalomma ticks that were recently found in the Netherlands.

Methods: Hyalomma ticks were morphologically identified. Cluster analysis, based upon sequence data (cox1 barcoding) for molecular identification, and pathogen detection were performed. Additionally, a cross-sectional survey of horses was conducted to actively search for Hyalomma ticks in summer 2019. Analysis of temperature was done to assess the possibility of (i) introduced engorged nymphs moulting to adults and (ii) establishment of populations in the Netherlands.

Results: Seventeen adult Hyalomma ticks (one in 2018, eleven in 2019, five in 2020) were found by citizens and reported. Fifteen ticks were detected on horses and two on humans. Twelve were identified as H. marginatum, one as H. rufipes and four, of which only photographic images were available, as Hyalomma sp. No Crimean-Congo haemorrhagic fever virus or Babesia/Theileria parasites were detected. One adult tick tested positive for Rickettsia aeschlimannii. In the cross-sectional horse survey, no Hyalomma ticks were found. Analysis of temperatures showed that engorged nymphs arriving on migratory birds in spring were able to moult to adults in 2019 and 2020, and that cumulative daily temperatures in the Netherlands were lower than in areas with established H. marginatum populations.

Conclusions: Our results show that Hyalomma ticks are regularly introduced in the Netherlands as nymphs. Under the Dutch weather conditions, these nymphs are able to develop to the adult stage, which can be sighted by vigilant citizens. Only one human pathogen, Rickettsia aeschlimannii, was found in one of the ticks. The risk of introduction of tick-borne diseases via Hyalomma ticks on migratory birds is considered to be low. Establishment of permanent Hyalomma populations is considered unlikely under the current Dutch climatic conditions.
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http://dx.doi.org/10.1186/s13071-021-04738-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8106226PMC
May 2021

Circulation of Species and Their Exposure to Humans through .

Pathogens 2021 Mar 24;10(4). Epub 2021 Mar 24.

Centre for Infectious Disease Control, National Institute for Public Health and the Environment, 3720 BA Bilthoven, The Netherlands.

Human babesiosis in Europe has been attributed to infection with and, to a lesser extent, with and which are all transmitted to humans through a bite of . These species circulate in the Netherlands, but autochthonous human babesiosis cases have not been reported so far. To gain more insight into the natural sources of these species, their presence in reservoir hosts and in was examined. Moreover, part of the ticks were tested for co-infections with other tick borne pathogens. In a cross-sectional study, qPCR-detection was used to determine the presence of species in 4611 tissue samples from 27 mammalian species and 13 bird species. Reverse line blotting (RLB) and qPCR detection of species were used to test 25,849 questing . Fragments of the 18S rDNA and cytochrome c oxidase subunit I (COI) gene from PCR-positive isolates were sequenced for confirmation and species identification and species-specific PCR reactions were performed on samples with suspected mixed infections. was found in two widespread rodent species: and , whereas was detected in the geographically restricted and , and occasionally in free-ranging . was detected in the ubiquitous , and occasionally in free-ranging . pecies-specific PCR revealed co-infections in and resulting in higher prevalence of and than disclosed by qPCR detection, followed by 18S rDNA and COI sequencing. The non-zoonotic species found were , sp. deer clade and badger-associated species. The infection rate of zoonotic species in questing ticks was higher for clade I (2.6%) than clade X (1.9%). Co-infection of with sensu lato and in questing nymphs occurred more than expected, which reflects their mutual reservoir hosts, and suggests the possibility of co-transmission of these three pathogens to humans during a tick bite. The ubiquitous spread and abundance of and in their reservoir hosts and questing ticks imply some level of human exposure through tick bites. The restricted distribution of the wild reservoir hosts for and its low infection rate in ticks might contribute to the absence of reported autochthonous cases of human babesiosis in the Netherlands.
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http://dx.doi.org/10.3390/pathogens10040386DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8063829PMC
March 2021

Seasonal patterns and spatial variation of Borrelia burgdorferi (sensu lato) infections in Ixodes ricinus in the Netherlands.

Parasit Vectors 2021 Feb 24;14(1):121. Epub 2021 Feb 24.

Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.

Background: The incidence of Lyme borreliosis varies over time and space through as yet incompletely understood mechanisms. In Europe, Lyme borreliosis is caused by infection with a Borrelia burgdorferi (s.l.) genospecies, which is primarily transmitted by a bite of Ixodes ricinus nymphs. The aim of this study was to investigate the spatial and temporal variation in nymphal infection prevalence of B. burgdorferi (s.l.) (NIP), density of questing nymphs (DON) and the resulting density of infected nymphs (DIN).

Methods: We investigated the infection rates in I. ricinus nymphs that were collected monthly between 2009 and 2016 in 12 locations in the Netherlands. Using generalized linear mixed models, we explored how the NIP, DON and DIN varied during the seasons, between years and between locations. We also determined the genospecies of the Borrelia infections and investigated whether the genospecies composition differed between locations.

Results: The overall NIP was 14.7%. A seasonal pattern in infection prevalence was observed, with higher estimated prevalences in the summer than in the spring and autumn. This, combined with higher nymphal densities in summer, resulted in a pronounced summer peak in the estimated DIN. Over the 7.5-year study period, a significant decrease in infection prevalence was found, as well as a significant increase in nymphal density. These two effects appear to cancel each other out; the density of infected nymphs, which is the product of NIP × DON, showed no significant trend over years. Mean infection prevalence (NIP, averaged over all years and all months) varied considerably between locations, ranging from 5 to 26%. Borrelia genospecies composition differed between locations: in some locations almost all infections consisted of B. afzelii, whereas other locations had more diverse genospecies compositions.

Conclusion: In the Netherlands, the summer peak in DIN is a result of peaks in both NIP and DON. No significant trend in DIN was observed over the years of the study, and variations in DIN between locations were mostly a result of the variation in DON. There were considerable differences in acarological risk between areas in terms of infection prevalence and densities of ticks as well as in Borrelia genospecies composition.
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http://dx.doi.org/10.1186/s13071-021-04607-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7905678PMC
February 2021

The Role of Peridomestic Animals in the Eco-Epidemiology of Anaplasma phagocytophilum.

Microb Ecol 2021 Oct 5;82(3):602-612. Epub 2021 Feb 5.

Department of Pathology and Parasitology, Faculty of Veterinary Medicine, University of Veterinary and Pharmaceutical Sciences, Palackého třída 1946/1, Brno, Czech Republic.

Anaplasma phagocytophilum is an important tick-borne zoonotic agent of human granulocytic anaplasmosis (HGA). In Europe, the Ixodes ticks are the main vector responsible for A. phagocytophilum transmission. A wide range of wild animals is involved in the circulation of this pathogen in the environment. Changes in populations of vertebrates living in different ecosystems impact the ecology of ticks and the epidemiology of tick-borne diseases. In this study, we investigated four species, Western European hedgehog (Erinaceus europaeus), northern white-breasted hedgehog (Erinaceus roumanicus), Eurasian red squirrel (Sciurus vulgaris), and the common blackbird (Turdus merula), to describe their role in the circulation of A. phagocytophilum in urban and periurban ecosystems. Ten different tissues were collected from cadavers of the four species, and blood and ear/skin samples from live blackbirds and hedgehogs. Using qPCR, we detected a high rate of A. phagocytophilum: Western European hedgehogs (96.4%), northern white-breasted hedgehogs (92.9%), Eurasian red squirrels (60%), and common blackbirds (33.8%). In the groEL gene, we found nine genotypes belonging to three ecotypes; seven of the genotypes are associated with HGA symptoms. Our findings underline the role of peridomestic animals in the ecology of A. phagocytophilum and indicate that cadavers are an important source of material for monitoring zoonotic pathogens. Concerning the high prevalence rate, all investigated species play an important role in the circulation of A. phagocytophilum in municipal areas; however, hedgehogs present the greatest anaplasmosis risk for humans. Common blackbirds and squirrels carry different A. phagocytophilum variants some of which are responsible for HGA.
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http://dx.doi.org/10.1007/s00248-021-01704-zDOI Listing
October 2021

Red and fallow deer determine the density of Ixodes ricinus nymphs containing Anaplasma phagocytophilum.

Parasit Vectors 2021 Jan 19;14(1):59. Epub 2021 Jan 19.

Centre for Zoonoses and Environmental Microbiology Centre for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands.

Background: The density of Ixodes ricinus nymphs infected with Anaplasma phagocytophilum is one of the parameters that determines the risk for humans and domesticated animals to contract anaplasmosis. For this, I. ricinus larvae need to take a bloodmeal from free-ranging ungulates, which are competent hosts for A. phagocytophilum.

Methods: Here, we compared the contribution of four free-ranging ungulate species, red deer (Cervus elaphus), fallow deer (Dama dama), roe deer (Capreolus capreolus), and wild boar (Sus scrofa), to A. phagocytophilum infections in nymphs. We used a combination of camera and live trapping to quantify the relative availability of vertebrate hosts to questing ticks in 19 Dutch forest sites. Additionally, we collected questing I. ricinus nymphs and tested these for the presence of A. phagocytophilum. Furthermore, we explored two potential mechanisms that could explain differences between species: (i) differences in larval burden, which we based on data from published studies, and (ii) differences in associations with other, non-competent hosts.

Results: Principal component analysis indicated that the density of A. phagocytophilum-infected nymphs (DIN) was higher in forest sites with high availability of red and fallow deer, and to a lesser degree roe deer. Initial results suggest that these differences are not a result of differences in larval burden, but rather differences in associations with other species or other ecological factors.

Conclusions: These results indicate that the risk for contracting anaplasmosis in The Netherlands is likely highest in the few areas where red and fallow deer are present. Future studies are needed to explore the mechanisms behind this association.
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http://dx.doi.org/10.1186/s13071-020-04567-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7814456PMC
January 2021

Hedgehogs, Squirrels, and Blackbirds as Sentinel Hosts for Active Surveillance of and Complex in Urban and Rural Environments.

Microorganisms 2020 Nov 30;8(12). Epub 2020 Nov 30.

Institute of Parasitology, Biology Center, Czech Academy of Sciences (CAS), 37005 Ceske Budejovice, Czech Republic.

Lyme borreliosis (LB), caused by spirochetes of the sensu lato (s.l.) complex, is one of the most common vector-borne zoonotic diseases in Europe. Knowledge about the enzootic circulation of pathogens between ticks and their vertebrate hosts is epidemiologically important and enables assessment of the health risk for the human population. In our project, we focused on the following vertebrate species: European hedgehog (), Northern white-breasted hedgehog (), Eurasian red squirrel (), and Common blackbird (). The cadavers of accidentally killed animals used in this study constitute an available source of biological material, and we have confirmed its potential for wide monitoring of s.l. presence and genospecies diversity in the urban environment. High infection rates (90% for , 73% for , 91% for , and 68% for ) were observed in all four target host species; mixed infections by several genospecies were detected on the level of individuals, as well as in particular tissue samples. These findings show the usefulness of multiple tissue sampling as tool for revealing the occurrence of several genospecies within one animal and the risk of missing particular s.l. genospecies when looking in one organ alone.
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http://dx.doi.org/10.3390/microorganisms8121908DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7760222PMC
November 2020

A combined transcriptomic approach to identify candidates for an anti-tick vaccine blocking B. afzelii transmission.

Sci Rep 2020 11 18;10(1):20061. Epub 2020 Nov 18.

Center for Experimental and Molecular Medicine, Amsterdam Infection and Immunity, Amsterdam UMC, Location Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.

Ixodes ricinus is the vector for Borrelia afzelii, the predominant cause of Lyme borreliosis in Europe, whereas Ixodes scapularis is the vector for Borrelia burgdorferi in the USA. Transcription of several I. scapularis genes changes in the presence of B. burgdorferi and contributes to successful infection. To what extend B. afzelii influences gene expression in I. ricinus salivary glands is largely unknown. Therefore, we measured expression of uninfected vs. infected tick salivary gland genes during tick feeding using Massive Analysis of cDNA Ends (MACE) and RNAseq, quantifying 26.179 unique transcripts. While tick feeding was the main differentiator, B. afzelii infection significantly affected expression of hundreds of transcripts, including 465 transcripts after 24 h of tick feeding. Validation of the top-20 B. afzelii-upregulated transcripts at 24 h of tick feeding in ten biological genetic distinct replicates showed that expression varied extensively. Three transcripts could be validated, a basic tail protein, a lipocalin and an ixodegrin, and might be involved in B. afzelii transmission. However, vaccination with recombinant forms of these proteins only marginally altered B. afzelii infection in I. ricinus-challenged mice for one of the proteins. Collectively, our data show that identification of tick salivary genes upregulated in the presence of pathogens could serve to identify potential pathogen-blocking vaccine candidates.
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http://dx.doi.org/10.1038/s41598-020-76268-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7674437PMC
November 2020

Commentary: : 43 Cases Diagnosed in France by Real-Time PCR in Patients With Persistent Polymorphic Signs and Symptoms.

Front Med (Lausanne) 2020 2;7:474. Epub 2020 Sep 2.

Section of Infectious Diseases, Department of Internal Medicine, Amsterdam UMC, Amsterdam, Netherlands.

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http://dx.doi.org/10.3389/fmed.2020.00474DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7492646PMC
September 2020

Ticks climb the mountains: Ixodid tick infestation and infection by tick-borne pathogens in the Western Alps.

Ticks Tick Borne Dis 2020 09 8;11(5):101489. Epub 2020 Jun 8.

Department of Veterinary Sciences, University of Turin, Largo Braccini, 2, 10095 Grugliasco, TO, Italy. Electronic address:

In mountain areas of northwestern Italy, ticks were rarely collected in the past. In recent years, a marked increase in tick abundance has been observed in several Alpine valleys, together with more frequent reports of Lyme borreliosis. We then carried out a four-year study to assess the distribution and abundance of ticks and transmitted pathogens and determine their altitudinal limit in a natural park area in Piedmont region. Ixodes ricinus and Dermacentor marginatus were collected from both the vegetation and hunted wild ungulates. Tick abundance was significantly associated with altitude, habitat type and signs of animal presence, roe deer's in particular. Ixodes ricinus prevailed in distribution and abundance and, although their numbers decreased with increasing altitude, we recorded the presence of all active life stages of up to around 1700 m a.s.l., with conifers as the second most infested habitat after deciduous woods. Molecular analyses demonstrated the infection of questing I. ricinus nymphs with B. burgdorferi sensu lato (15.5 %), Rickettsia helvetica and R. monacensis (20.7 %), Anaplasma phagocytophilum (1.9 %), Borrelia miyamotoi (0.5 %) and Neoehrlichia mikurensis (0.5 %). One third of the questing D. marginatus were infected with R. slovaca. We observed a spatial aggregation of study sites infested by B. burgdorferi s.l. infected ticks below 1400 m. Borrelia-infected nymphs prevailed in open areas, while SFG rickettsiae prevalence was higher in coniferous and deciduous woods. Interestingly, prevalence of SFG rickettsiae in ticks doubled above 1400 m, and R. helvetica was the only pathogen detected above 1800 m a.s.l. Tick infestation on hunted wild ungulates indicated the persistence of tick activity during winter months and, when compared to past studies, confirmed the recent spread of I. ricinus in the area. Our study provides new insights into the population dynamics of ticks in the Alps and confirms a further expansion of ticks to higher altitudes in Europe. We underline the importance of adopting a multidisciplinary approach in order to develop effective strategies for the surveillance of tick-borne diseases, and inform the public about the hazard posed by ticks, especially in recently invaded areas.
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http://dx.doi.org/10.1016/j.ttbdis.2020.101489DOI Listing
September 2020

Tripartite Interactions among , and Deer: Differential Interference with Transmission Cycles of Tick-Borne Pathogens.

Pathogens 2020 Apr 30;9(5). Epub 2020 Apr 30.

Zoology Section, Department of Biology, Ege University Faculty of Science, Bornova Izmir 35040, Turkey.

For the development of sustainable control of tick-borne diseases, insight is needed in biological factors that affect tick populations. Here, the ecological interactions among , , and two vertebrate species groups were investigated in relation to their effects on tick-borne disease risk. In 1129 questing ticks, DNA was detected more often in nymphs (4.4%) than in larvae (0.5%) and not in adults. Therefore, we determined the infestation rate of in nymphs from 19 forest sites, where vertebrate, tick, and tick-borne pathogen communities had been previously quantified. We found higher than expected co-occurrence rates of with deer-associated , and lower than expected rates with rodent-associated and . The prevalence of in nymphs varied between 0% and 16% and was positively correlated with the encounter probability of ungulates and the densities of all life stages of . Lastly, we investigated the emergence of from artificially fed, field-collected nymphs. Adult wasps emerged from seven of the 172 fed nymphs. From these observations, we inferred that is parasitizing larvae that are feeding on deer, rather than on rodents or in the vegetation. Since populations depend on deer abundance, the main propagation host of , these wasps have no apparent effect on tick populations. The presence of may directly interfere with the transmission cycle of , but not with that of or .
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http://dx.doi.org/10.3390/pathogens9050339DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7281138PMC
April 2020

Mitochondrial sequences of Rhipicephalus and Coxiella endosymbiont reveal evidence of lineages co-cladogenesis.

FEMS Microbiol Ecol 2020 06;96(6)

Centre for Environmental and Marine Studies (CESAM), Departamento de Biologia Animal, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal.

Rhipicephalus ticks are competent vectors of several pathogens, such as Spotted Fever Group Rickettsiae (SFGR) and many Babesia species. Within this genus, different R. sanguineus s.l. lineages show an unequal vector competence and resistance regarding some pathogenic strains. Current literature supports that tick endosymbionts may play an essential role in the transmission ability of a vector. Indeed, the microbial community of Rhipicephalus seems to be dominated by Coxiella-like endosymbionts (CLE). Still, their co-evolutionary associations with the complicated phylogeny of Rhipicephalus lineages and their transmissible pathogens remain unclear. We performed a phylogenetic congruence analysis to address whether divergent R. sanguineus s.l. lineages had a different symbiont composition. For that, we applied a PCR based approach to screen part of the microbial community present in 279 Rhipicephalus ticks from the Iberian Peninsula and Africa. Our analyses detected several qPCR-positive signals for both SFGR and Babesia species, of which we suggest R. sanguineus-tropical lineage as a natural vector of Babesia vogeli and R. sanguineus-temperate lineage of SFGR. The acquisition of 190 CLE sequences allowed to evaluate co-phylogenetic associations between the tick and the symbiont. With this data, we observed a strong but incomplete co-cladogenesis between CLE strains and their Rhipicephalus tick lineages hosts.
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http://dx.doi.org/10.1093/femsec/fiaa072DOI Listing
June 2020

Assessment of Borrelia miyamotoi in febrile patients and ticks in Alsace, an endemic area for Lyme borreliosis in France.

Parasit Vectors 2020 Apr 17;13(1):199. Epub 2020 Apr 17.

University of Strasbourg, Virulence bactérienne précoce UR7290-Lyme borreliosis group, FMTS - CHRU Strasbourg, Institut de Bactériologie, Strasbourg, France.

Background: Borrelia miyamotoi is a relapsing fever Borrelia species transmitted by ticks of the Ixodes ricinus complex. Human disease caused by B. miyamotoi was first described in Russia and later in the USA and Japan. Additionally, five cases of meningoencephalitis in immunocompromised patients and one case in an apparently immunocompetent patient were described.

Methods: We investigated the presence of B. miyamotoi in I. ricinus nymphs and in patients suspected of human granulocytic anaplasmosis, in Alsace (France), an endemic area for I. ricinus ticks and Lyme borreliosis, using direct (PCR) and indirect diagnosis (glycerophosphoryldiester-phosphodiesterase (GlpQ) serology).

Results: Borrelia miyamotoi was found in 2.2% of 4354 ticks collected between 2013 and 2016. None of the 575 blood samples, collected from the patients suspected of HGA, was found positive for B. miyamotoi by PCR. Acute and late sera from 138 of these 575 patients were available. These paired sera were tested for IgM and IgG antibodies against the B. miyamotoi GlpQ antigen. A total of 14 out of 138 patients had at least one positive parameter (i.e. anti-GlpQ IgG and/or IgM). One patient seroconverted for IgG, and three had isolated IgM in the acute serum. These three patients were treated with doxycycline which could have prevented seroconversion. After reviewing clinical data and other biological tests performed, co-exposure among different microorganisms vectored by ticks or serological cross-reactivity could not be ruled out in these different cases. One patient had persistent IgG, which strongly suggests previous exposure to B. miyamotoi.

Conclusions: Humans can be exposed to B. miyamotoi through tick bites in Alsace. We present serological data for possible B. miyamotoi exposure or infection of patients with fever after tick bite. Future studies should determine the incidence, clinical course and burden of this emerging tick-borne disease in other parts of Western Europe.
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http://dx.doi.org/10.1186/s13071-020-04071-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7165395PMC
April 2020

[Tick-borne encephalitis in the Netherlands].

Ned Tijdschr Geneeskd 2020 02 25;164. Epub 2020 Feb 25.

Diakonessenhuis Utrecht, afd. Medische Microbiologie, Utrecht.

Tick-borne encephalitis (TBE) is endemic in South-Scandinavia, Central Europe and Eastern Europe. In 2016 the first patient was reported with TBE virus infection contracted in the Netherlands, in a forested area between Driebergen and Maarn (near Utrecht). At the time, field research did not identify any TBE-positive ticks at the supposed infection site. In the last two years, two patients have been diagnosed with TBE in the Diakonessenhuis Hospital in Utrecht; one patient was bitten by a tick in the Netherlands. This time round, tests on ticks from a different area near Utrecht (the forests around Zeist) did identify TBE-positive ticks. TBE infection is often asymptomatic. However, in a small proportion of patients, disease can develop and there is currently no curative therapy available. An effective vaccine is available. At the moment no vaccination recommendation is issued in the Netherlands. TBE should be considered in patients presenting with fever after a recent tick bite. When neurological symptoms appear, referral to a neurologist is necessary.
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February 2020

Serological testing for Lyme Borreliosis in general practice: A qualitative study among Dutch general practitioners.

Eur J Gen Pract 2020 12 11;26(1):51-57. Epub 2020 Mar 11.

Department of General Practice, Amsterdam UMC/University of Amsterdam, Amsterdam, Netherlands.

Concerns are raised about missed, delayed and inappropriate diagnosis of Lyme Borreliosis. Quantitative descriptive studies have demonstrated non-adherence to the guidelines for testing for Lyme Borreliosis. To gain insight into the diagnostic practices that general practitioners apply for Lyme Borreliosis, their motives for ordering tests and how they act upon test results. A qualitative study among 16 general practitioners using semi-structured interviews and thematic content analysis. Five themes were distinguished: (1) recognising localised Lyme Borreliosis and symptoms of disseminated disease, (2) use of the guideline, (3) serological testing in patients with clinically suspect Lyme Borreliosis, (4) serological testing without clinical suspicion of Lyme Borreliosis, and (5) dealing with the limited accuracy of the serological tests. Whereas the national guideline recommends using serological tests for diagnosing, general practitioners also use them for ruling out disseminated Lyme Borreliosis. Reasons for non-adherence to the guideline for testing were to reassure patients with non-specific symptoms or without symptoms who feared to have Lyme disease, confirmation of localised Lyme Borreliosis and routine work-up in patients with continuing unexplained symptoms. Some general practitioners referred all patients who tested positive to medical specialists, where others struggled with the explanation of the results. Both diagnosis and ruling out of disseminated Lyme Borreliosis can be difficult for general practitioners. General practitioners use serological tests to reassure patients and rule out Lyme Borreliosis, thereby deviating from the national guideline. Interpretation of test results in these cases can be difficult.
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http://dx.doi.org/10.1080/13814788.2020.1732347DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7144248PMC
December 2020

Evaluation of Disease Causality of Rare -Borne Infections in Europe.

Pathogens 2020 Feb 24;9(2). Epub 2020 Feb 24.

Centre for Infectious Diseases Research, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.

In Europe, ticks transmit pathogens such as sensu lato and tick-borne encephalitis virus (TBEV). In addition, there is evidence for transmission to humans from of , , , , and . However, whether infection with these potential tick-borne pathogens results in human disease has not been fully demonstrated for all of these tick-borne microorganisms. To evaluate the available evidence for a causative relation between infection and disease, the current study analyses European case reports published from 2008 to 2018, supplemented with information derived from epidemiological and experimental studies. The evidence for human disease causality in Europe found in this review appeared to be strongest for . and . Nonetheless, some knowledge gaps still exist. Importantly, comprehensive evidence for pathogenicity is lacking for the remaining tick-borne microorganisms. Such evidence could be gathered best through prospective studies, for example, studies enrolling patients with a fever after a tick bite, the development of specific new serological tools, isolation of these microorganisms from ticks and patients and propagation in vitro, and through experimental studies.
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http://dx.doi.org/10.3390/pathogens9020150DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7168666PMC
February 2020

The scale affects our view on the identification and distribution of microbial communities in ticks.

Parasit Vectors 2020 Jan 21;13(1):36. Epub 2020 Jan 21.

Faculty of Veterinary Medicine, University of Zaragoza, Zaragoza, Spain.

Ticks transmit the highest variety of pathogens impacting human and animal health worldwide. It is now well established that ticks also harbour a microbial complex of coexisting symbionts, commensals and pathogens. With the development of high throughput sequencing technologies, studies dealing with such diverse bacterial composition in tick considerably increased in the past years and revealed an unexpected microbial diversity. These data on diversity and composition of the tick microbes are increasingly available, giving crucial details on microbial communities in ticks and improving our knowledge on the tick microbial community. However, consensus is currently lacking as to which scales (tick organs, individual specimens or species, communities of ticks, populations adapted to particular environmental conditions, spatial and temporal scales) best facilitate characterizing microbial community composition of ticks and understanding the diverse relationships among tick-borne bacteria. Temporal or spatial scales have a clear influence on how we conduct ecological studies, interpret results, and understand interactions between organisms that build the microbiome. We consider that patterns apparent at one scale can collapse into noise when viewed from other scales, indicating that processes shaping tick microbiome have a continuum of variability that has not yet been captured. Based on available reports, this review demonstrates how much the concept of scale is crucial to be considered in tick microbial community studies to improve our knowledge on tick microbe ecology and pathogen/microbiota interactions.
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http://dx.doi.org/10.1186/s13071-020-3908-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6975024PMC
January 2020

Effect of rodent density on tick and tick-borne pathogen populations: consequences for infectious disease risk.

Parasit Vectors 2020 Jan 20;13(1):34. Epub 2020 Jan 20.

Laboratory of Entomology, Wageningen University and Research Centre, Wageningen, The Netherlands.

Background: Rodents are considered to contribute strongly to the risk of tick-borne diseases by feeding Ixodes ricinus larvae and by acting as amplifying hosts for pathogens. Here, we tested to what extent these two processes depend on rodent density, and for which pathogen species rodents synergistically contribute to the local disease risk, i.e. the density of infected nymphs (DIN).

Methods: In a natural woodland, we manipulated rodent densities in plots of 2500 m by either supplementing a critical food source (acorns) or by removing rodents during two years. Untreated plots were used as controls. Collected nymphs and rodent ear biopsies were tested for the presence of seven tick-borne microorganisms. Linear models were used to capture associations between rodents, nymphs, and pathogens.

Results: Investigation of data from all plots, irrespective of the treatment, revealed a strong positive association between rodent density and nymphal density, nymphal infection prevalence (NIP) with Borrelia afzelii and Neoehrlichia mikurensis, and hence DIN's of these pathogens in the following year. The NIP, but not the DIN, of the bird-associated Borrelia garinii, decreased with increasing rodent density. The NIPs of Borrelia miyamotoi and Rickettsia helvetica were independent of rodent density, and increasing rodent density moderately increased the DINs. In addition, NIPs of Babesia microti and Spiroplasma ixodetis decreased with increasing rodent density, which had a non-linear association with DINs of these microorganisms.

Conclusions: A positive density dependence for all rodent- and tick-associated tick-borne pathogens was found, despite the observation that some of them decreased in prevalence. The effects on the DINs were variable among microorganisms, more than likely due to contrasts in their biology (including transmission modes, host specificity and transmission efficiency). The strongest associations were found in rodent-associated pathogens that most heavily rely on horizontal transmission. Our results draw attention to the importance of considering transmission mode of a pathogen while developing preventative measures to successfully reduce the burden of disease.
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http://dx.doi.org/10.1186/s13071-020-3902-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6971888PMC
January 2020

Host dispersal shapes the population structure of a tick-borne bacterial pathogen.

Mol Ecol 2020 02 9;29(3):485-501. Epub 2020 Jan 9.

CNRS - Department of Biometry and Evolutionary Biology (LBBE) - University Lyon 1, University of Lyon, Villeurbanne, France.

Birds are hosts for several zoonotic pathogens. Because of their high mobility, especially of longdistance migrants, birds can disperse these pathogens, affecting their distribution and phylogeography. We focused on Borrelia burgdorferi sensu lato, which includes the causative agents of Lyme borreliosis, as an example for tick-borne pathogens, to address the role of birds as propagation hosts of zoonotic agents at a large geographical scale. We collected ticks from passerine birds in 11 European countries. B. burgdorferi s.l. prevalence in Ixodes spp. was 37% and increased with latitude. The fieldfare Turdus pilaris and the blackbird T. merula carried ticks with the highest Borrelia prevalence (92 and 58%, respectively), whereas robin Erithacus rubecula ticks were the least infected (3.8%). Borrelia garinii was the most prevalent genospecies (61%), followed by B. valaisiana (24%), B. afzelii (9%), B. turdi (5%) and B. lusitaniae (0.5%). A novel Borrelia genospecies "Candidatus Borrelia aligera" was also detected. Multilocus sequence typing (MLST) analysis of B. garinii isolates together with the global collection of B. garinii genotypes obtained from the Borrelia MLST public database revealed that: (a) there was little overlap among genotypes from different continents, (b) there was no geographical structuring within Europe, and (c) there was no evident association pattern detectable among B. garinii genotypes from ticks feeding on birds, questing ticks or human isolates. These findings strengthen the hypothesis that the population structure and evolutionary biology of tick-borne pathogens are shaped by their host associations and the movement patterns of these hosts.
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http://dx.doi.org/10.1111/mec.15336DOI Listing
February 2020

Effects of cattle grazing on Ixodes ricinus-borne disease risk in forest areas of the Netherlands.

Ticks Tick Borne Dis 2020 03 6;11(2):101355. Epub 2019 Dec 6.

Resource Ecology Group, Wageningen University, Wageningen, The Netherlands.

Cattle grazing has been suggested to reduce the risk for Lyme borreliosis by decreasing the density of questing Ixodes ricinus infected with Borrelia burgdorferi sensu lato. We tested the hypotheses that cattle grazing used in woodland management decreases the density of questing I. ricinus, and that it decreases the nympal infection prevalence of B. burgdorferi sensu lato. We further expected the nympal infection prevalence of tick-borne pathogens that utilize cattle as amplifying hosts, namely Anaplasma phagocytophilum, and Babesia sensu stricto, to increase. To test these hypotheses, we compared the densities of questing I. ricinus between twenty pairs of plots in grazed and ungrazed forest areas. The density of I. ricinus adults, but not nymphs, was lower in areas grazed by cattle than in ungrazed areas. Nymphs were tested for the presence of Borrelia burgdorferi s.l., Borrelia miyamotoi, Anaplasma phagocytophilum, and Babesia s.s. DNA from twelve paired areas. Anaplasma phagocytophilum and Babesia s.s. from qPCR-positive tick lysates were identified further to the ecotype and species level, respectively, by DNA sequencing. The infection prevalence of A. phagocytophilum was lower, and infection prevalence of Babesia s.s., identified as Babesia venatorum, was higher in grazed areas. In contrast, infection prevalence with B. burgdorferi s.l. or B. miyamotoi did not differ between grazed and ungrazed areas. As a consequence, conventional cattle grazing in forested areas had no effect on the densities of questing nymphs infected with B. burgdorferi s.l. and B. miyamotoi. Similarly, we found no effect of cattle grazing on the density of infected nymphs with B. venatorum. The marked difference in the densities of questing nymphs infected with A. phagocytophilum could potentially be explained by the presence of a higher density of roe deer (Capreolus capreolus) in ungrazed areas, as the majority of typed A. phagocytophilum from ungrazed areas were the non-zoonotic ecotype II, which is associated with roe deer.
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http://dx.doi.org/10.1016/j.ttbdis.2019.101355DOI Listing
March 2020

Draft Whole-Genome Sequences of Two Western European Borrelia miyamotoi Isolates.

Microbiol Resour Announc 2019 Dec 12;8(50). Epub 2019 Dec 12.

Amsterdam University Medical Centers, Amsterdam, The Netherlands.

We report the draft whole-genome sequences of two strains isolated in The Netherlands. Using next-generation sequencing, we determined the complete sequence of the chromosomes and several plasmids. The two strains show a genotype typical of European strains, distinct from the genomes of strains from Asia or the United States.
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http://dx.doi.org/10.1128/MRA.01314-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6908798PMC
December 2019

Presence of Roe Deer Affects the Occurrence of Ecotypes in Questing in Different Habitat Types of Central Europe.

Int J Environ Res Public Health 2019 11 27;16(23). Epub 2019 Nov 27.

Institute of Zoology, Slovak Academy of Sciences, Dúbravská cesta 9, 84506 Bratislava, Slovakia.

The way in which European genetic variants of circulate in their natural foci and which variants cause disease in humans or livestock remains thus far unclear. Red deer and roe deer are suggested to be reservoirs for some European strains, and is their principal vector. Based on gene sequences, five ecotypes have been identified. Ecotype I is associated with the broadest host range, including strains that cause disease in domestic animals and humans. Ecotype II is associated with roe deer and does not include zoonotic strains. In the present study, questing were collected in urban, pasture, and natural habitats in the Czech Republic, Germany, and Slovakia. A fragment of the gene of was amplified by real-time PCR in DNA isolated from ticks. Positive samples were further analyzed by nested PCRs targeting fragments of the rRNA and genes, followed by sequencing. Samples were stratified according to the presence/absence of roe deer at the sampling sites. Geographic origin, habitat, and tick stage were also considered. The probability that is a particular ecotype was estimated by a generalized linear model. was identified by genetic typing in 274 ticks. The majority belonged to ecotype I (63.9%), 28.5% were ecotype II, and both ecotypes were identified in 7.7% of ticks. Ecotype II was more frequently identified in ticks originating from a site with presence of roe deer, whereas ecotype I was more frequent in adult ticks than in nymphs. Models taking into account the country-specific, site-specific, and habitat-specific aspects did not improve the goodness of the fit. Thus, roe deer presence in a certain site and the tick developmental stage are suggested to be the two factors consistently influencing the occurrence of a particular ecotype in a positive tick.
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http://dx.doi.org/10.3390/ijerph16234725DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6926711PMC
November 2019

Parasite Load and Site-Specific Parasite Pressure as Determinants of Immune Indices in Two Sympatric Rodent Species.

Animals (Basel) 2019 Nov 22;9(12). Epub 2019 Nov 22.

Resource Ecology Group, Wageningen University, Droevendaalsesteeg 3a, 6708PB Wageningen, The Netherlands.

Wildlife is exposed to parasites from the environment. This parasite pressure, which differs among areas, likely shapes the immunological strategies of animals. Individuals differ in the number of parasites they encounter and host, and this parasite load also influences the immune system. The relative impact of parasite pressure vs. parasite load on different host species, particularly those implicated as important reservoirs of zoonotic pathogens, is poorly understood. We captured bank voles () and wood mice () at four sites in the Netherlands. We sampled sub-adult males to quantify their immune function, infestation load for ecto- and gastrointestinal parasites, and infection status for vector-borne microparasites. We then used regression trees to test if variation in immune indices could be explained by among-site differences (parasite pressure), among-individual differences in infestation intensity and infection status (parasite load), or other intrinsic factors. Regression trees revealed splits among sites for haptoglobin, hemagglutination, and body-mass corrected spleen size. We also found splits based on infection/infestation for haptoglobin, hemolysis, and neutrophil to lymphocyte ratio. Furthermore, we found a split between species for hemolysis and splits based on body mass for haptoglobin, hemagglutination, hematocrit, and body-mass corrected spleen size. Our results suggest that both parasite pressure and parasite load influence the immune system of wild rodents. Additional studies linking disease ecology and ecological immunology are needed to understand better the complexities of host-parasite interactions and how these interactions shape zoonotic disease risk.
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http://dx.doi.org/10.3390/ani9121015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6940963PMC
November 2019

Prevalence of pathogens in ticks collected from humans through citizen science in Belgium.

Parasit Vectors 2019 Nov 21;12(1):550. Epub 2019 Nov 21.

Centre for Infectious Disease Control, National Institute for Public Health and Environment (RIVM), Bilthoven, The Netherlands.

Background: In order to evaluate the risk of human exposure to tick-borne pathogens in Belgium, a study on the prevalence of several pathogens was conducted on feeding ticks removed from humans in 2017.

Methods: Using a citizen science approach based on an existing notification tool for tick bites, a sample of ticks was collected across the country. Collected ticks were screened by PCR for the presence of the following pathogens: Anaplasma phagocytophilum, Babesia spp., Borrelia burgdorferi (sensu lato), Borrelia miyamotoi, Neoehrlichia mikurensis, Rickettsia helvetica and tick-borne encephalitis virus (TBEV).

Results: In total, 1599 ticks were included in the sample. The great majority of ticks belonged to Ixodes ricinus (99%); other tick species were identified as Ixodes hexagonus (0.7%) and Dermacentor reticulatus (0.3%). Borrelia burgdorferi (s.l.) was detected in 14% of nymphs and adult ticks. Adult ticks (20%) were more likely to be infected than nymphs (12%). The most common genospecies were B. afzelii (52%) and B. garinii (21%). Except for TBEV, the other tick-borne pathogens studied were all detected in the tick sample, although at a lower prevalence: 1.5% for Babesia spp.; 1.8% for A. phagocytophilum; 2.4% for B. miyamotoi; 2.8% for N. mikurensis; and 6.8% for R. helvetica. Rickettsia raoultii, the causative agent of tick-borne lymphadenopathy, was identified for the first time in Belgium, in two out of five D. reticulatus ticks. Co-infections were found in 3.9% of the examined ticks. The most common co-infection was B. burgdorferi (s.l.) + N. mikurensis.

Conclusions: Although for most of the tick-borne diseases in Belgium, other than Lyme borreliosis, no or few cases of human infection are reported, the pathogens causing these diseases were all (except for TBEV) detected in the tick study sample. Their confirmed presence can help raise awareness among citizens and health professionals in Belgium on possible diseases other than Lyme borreliosis in patients presenting fever or other non-characteristic symptoms after a tick bite.
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http://dx.doi.org/10.1186/s13071-019-3806-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6873681PMC
November 2019
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