In Europe, Ixodes ricinus is the vector of many pathogens of medical and veterinary relevance, among them Borrelia burgdorferi sensu lato and tick-borne encephalitis virus, which have been the subject of numerous investigations. Less is known about the occurrence of emerging tick-borne pathogens like Rickettsia spp., Babesia spp., “Candidatus Neoehrlichia mikurensis,” and Anaplasma phagocytophilum in questing ticks. In this study, questing nymph and adult I. ricinus ticks were collected at 11 sites located in Western Switzerland. A total of 1,476 ticks were analyzed individually for the simultaneous presence of B. burgdorferi sensu lato, Rickettsia spp., Babesia spp., “Candidatus Neoehrlichia mikurensis,” and A. phagocytophilum. B. burgdorferi sensu lato, Rickettsia spp., and “Candidatus Neoehrlichia mikurensis” were detected in ticks at all sites with global prevalences of 22.5%, 10.2%, and 6.4%, respectively. Babesia- and A. phagocytophilum-infected ticks showed a more restricted geographic distribution, and their prevalences were lower (1.9% and 1.5%, respectively). Species rarely reported in Switzerland, like Borrelia spielmanii, Borrelia lusitaniae, and Rickettsia monacensis, were identified. Infections with more than one pathogenic species, involving mostly Borrelia spp. and Rickettsia helvetica, were detected in 19.6% of infected ticks. Globally, 34.2% of ticks were infected with at least one pathogen. The diversity of tick-borne pathogens detected in I. ricinus in this study and the frequency of coinfections underline the need to take them seriously into consideration when evaluating the risks of infection following a tick bite.
To estimate the likelihood of people coming into contact with the recently described tick-borne agent “Candidatus Neoehrlichia mikurensis,” we compared its prevalence to those of Lyme disease spirochetes and Anaplasma phagocytophilum in questing adult Ixodes ricinus ticks collected in various Central European sites and examined ticks, which had been removed from people, for the presence of these pathogens. Whereas spirochetes infected questing adult ticks most frequently (22.3%), fewer than a third as many ticks were infected by “Ca. Neoehrlichia mikurensis” (6.2%), and about a sixth harbored A. phagocytophilum (3.9%). On average, every twelfth encounter of a person with an I. ricinus tick (8.1%) may bear the risk of acquiring “Ca. Neoehrlichia mikurensis.” Although a fifth of the people (20%) had removed at least one tick infected by “Ca. Neoehrlichia mikurensis,” none displayed symptoms described for this pathogen, suggesting that its transmission may not be immediate and/or that immunocompetent individuals may not be affected. Because immunosuppressed patients may be at a particular risk of developing symptoms, it should be considered that “Ca. Neoehrlichia mikurensis” appears to be the second most common pathogen in I. ricinus ticks. In our survey, only Borrelia afzelii appears to infect Central European vector ticks more frequently.
Ixodes ricinus transmits Borrelia burgdorferi sensu lato, the etiological agent of Lyme disease. Previous studies have also detected Rickettsia helvetica, Anaplasma phagocytophilum, Neoehrlichia mikurensis, and several Babesia species in questing ticks in The Netherlands. In this study, we assessed the acarological risk of exposure to several tick-borne pathogens (TBPs), in The Netherlands. Questing ticks were collected monthly between 2006 and 2010 at 21 sites and between 2000 and 2009 at one other site. Nymphs and adults were analysed individually for the presence of TBPs using an array-approach. Collated data of this and previous studies were used to generate, for each pathogen, a presence/absence map and to further analyse their spatiotemporal variation. R. helvetica (31.1%) and B. burgdorferi sensu lato (11.8%) had the highest overall prevalence and were detected in all areas. N. mikurensis (5.6%), A. phagocytophilum (0.8%), and Babesia spp. (1.7%) were detected in most, but not all areas. The prevalences of pathogens varied among the study areas from 0 to 64%, while the density of questing ticks varied from 1 to 179/100 m2. Overall, 37% of the ticks were infected with at least one pathogen and 6.3% with more than one pathogen. One-third of the Borrelia-positive ticks were infected with at least one other pathogen. Coinfection of B. afzelii with N. mikurensis and with Babesia spp. occurred significantly more often than single infections, indicating the existence of mutual reservoir hosts. Alternatively, coinfection of R. helvetica with either B. afzelii or N. mikurensis occurred significantly less frequent. The diversity of TBPs detected in I. ricinus in this study and the frequency of their coinfections with B. burgdorferi s.l., underline the need to consider them when evaluating the risks of infection and subsequently the risk of disease following a tick bite.
vector-borne disease; Borrelia burgdorferi; Candidatus Neoehrlichia mikurensis; Rickettsia helvetica; Rickettsia conorii; Anaplasma phagocytophilum; Babesia; Ixodes ricinus
‘Candidatus Neoehrlichia mikurensis’ is a tick-borne bacteria implicated in human health. To date, ‘Ca. Neoehrlichia mikurensis’ has been described in different countries from Africa, Asia and Europe, but never in Spain. However, according to the epidemiological features of the main vector in Europe, Ixodes ricinus, its circulation in our country was suspected.
A total of 200 I. ricinus ticks collected in the North of Spain were analyzed. DNAs were extracted and used as templates for PCRs targeting fragment genes for Anaplasma/Ehrlichia detection. The amplified products were sequenced and analyzed.
‘Ca. Neoehrlichia mikurensis’ was amplified in two specimens. Furthermore, Anaplasma phagocytophilum was detected in 61 samples analyzed.
The detection of ‘Ca. Neoehrlichia mikurensis’ in I. ricinus ticks from Spain indicates its circulation and the potential risk of contracting a human infection in this country.
‘Candidatus Neoehrlichia mikurensis’; Anaplasma phagocytophilum; Ixodes ricinus; Spain
In The Netherlands, the incidence of Lyme borreliosis is on the rise. Besides its causative agent, Borrelia burgdorferi s.l., other potential pathogens like Rickettsia, Babesia and Ehrlichia species are present in Ixodes ricinus ticks. The risk of disease associated with these microorganisms after tick-bites remains, however, largely unclear. A prospective study was performed to investigate how many persons with tick-bites develop localized or systemic symptoms and whether these are associated with tick-borne microorganisms.
In total, 297 Ixodes ricinus ticks were collected from 246 study participants who consulted a general practitioner on the island of Ameland for tick bites. Ticks were subjected to PCR to detect DNA of Borrelia burgdorferi s.l., Rickettsia spp., Babesia spp. or Ehrlichia/Anaplasma spp.. Sixteen percent of the collected ticks were positive for Borrelia burgdorferi s.l., 19% for Rickettsia spp., 12% for Ehrlichia/Anaplasma spp. and 10% for Babesia spp.. At least six months after the tick bite, study participants were interviewed on symptoms by means of a standard questionnaire. 14 out of 193 participants (8.3%) reported reddening at the bite site and 6 participants (4.1%) reported systemic symptoms. No association between symptoms and tick-borne microorganisms was found. Attachment duration ≥24 h was positively associated with reddening at the bite site and systemic symptoms. Using logistic regression techniques, reddening was positively correlated with presence of Borrelia afzelii, and having 'any symptoms' was positively associated with attachment duration.
The risk of contracting acute Lyme borreliosis, rickettsiosis, babesiosis or ehrlichiosis from a single tick bite was <1% in this study population.
Raising abundance of ticks and tick-borne diseases in Europe is the result of multiple factors including climate changes and human activities. Herein, we investigated the presence and seasonal activity of Ixodes ricinus ticks from 10 urban and suburban sites in two different geographical areas of southeastern and northeastern Slovakia during 2008–2010. Our aim was to study the abundance of ticks in correlation with the environmental factors and their infection with Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum and Neoehrlichia mikurensis.
Questing I. ricinus ticks were collected from ten urban and suburban sites in Eastern Slovakia. A total of 670 ticks were further analysed for the presence of B. burgdorferi s.l., A. phagocytophilum and N. mikurensis by molecular methods. Tick site and environmental relations were analysed using General Linear Models (LM). The differences between the number of Lyme borreliosis cases between the Košice and Bardejov regions during a ten-year period were tested by Wilcoxon matched pairs test.
In total, 2921 (1913 nymphs, 1008 adults) I. ricinus ticks were collected from 10 study sites during the main questing season. Tick activity and relative abundance differed between locations and months. Temperature and humidity were the main factors affecting the tick abundance and questing activity. Out of 670 examined ticks, 10.15% were infected with spirochetes from B. burgdorferi s.l. complex (represented by B. afzelii, B. garinii, B.valaisiana and B. burgdorferi s.s.), 2.69% with the A. phagocytophilum and 2.39% with N. mikurensis. The number of Lyme borreliosis cases per 100,000 inhabitants in the Bardejov region was significantly higher than in the Košice region.
Our data indicate that the risk of infection with tick-borne pathogens in Eastern Slovakia is common since 15.2% of ticks were infected at least with one of the tested microorganisms. Even though the abundance of ticks was affected by the microclimatic conditions and the prevalence of pathogens differed between the habitats, the infection risk for humans is also affected by human activities leading to an increased contact with infected ticks.
Ixodes ricinus; Borrelia burgdorferi sensu lato; Anaplasma phagocytophilum; Neoehrlichia mikurensis; PCR-RFLP; Lyme borreliosis; Anaplasmosis
Only limited information is available about the occurrence of ticks and tick-borne pathogens in public parks, which are areas strongly influenced by human beings. For this reason, Ixodes ricinus were collected in public parks of different Bavarian cities in a 2-year survey (2009 and 2010) and screened for DNA of Babesia spp., Rickettsia spp. and Bartonella spp. by PCR. Species identification was performed by sequence analysis and alignment with existing sequences in GenBank. Additionally, coinfections with Anaplasma phagocytophilum were investigated.
The following prevalences were detected: Babesia spp.: 0.4% (n = 17, including one pool of two larvae) in 2009 and 0.5 to 0.7% (n = 11, including one pool of five larvae) in 2010; Rickettsia spp.: 6.4 to 7.7% (n = 285, including 16 pools of 76 larvae) in 2009. DNA of Bartonella spp. in I. ricinus in Bavarian public parks could not be identified. Sequence analysis revealed the following species: Babesia sp. EU1 (n = 25), B. divergens (n = 1), B. divergens/capreoli (n = 1), B. gibsoni-like (n = 1), R. helvetica (n = 272), R. monacensis IrR/Munich (n = 12) and unspecified R. monacensis (n = 1). The majority of coinfections were R. helvetica with A. phagocytophilum (n = 27), but coinfections between Babesia spp. and A. phagocytophilum, or Babesia spp. and R. helvetica were also detected.
I. ricinus ticks in urban areas of Germany harbor several tick-borne pathogens and coinfections were also observed. Public parks are of particularly great interest regarding the epidemiology of tick-borne pathogens, because of differences in both the prevalence of pathogens in ticks as well as a varying species arrangement when compared to woodland areas. The record of DNA of a Babesia gibsoni-like pathogen detected in I. ricinus suggests that I. ricinus may harbor and transmit more Babesia spp. than previously known. Because of their high recreational value for human beings, urban green areas are likely to remain in the research focus on public health issues.
The importance of established and emerging tick-borne pathogens in Central and Northern Europe is steadily increasing. In 2007, we collected Ixodes ricinus ticks feeding on birds (n = 211) and rodents (n = 273), as well as host-seeking stages (n = 196), in a habitat in central Germany. In order to find out more about their natural transmission cycles, the ticks were tested for the presence of Lyme disease borreliae, Anaplasma phagocytophilum, spotted fever group (SFG) rickettsiae, Francisella tularensis, and babesiae. Altogether, 20.1% of the 680 ticks examined carried at least one pathogen. Bird-feeding ticks were more frequently infected with Borrelia spp. (15.2%) and A. phagocytophilum (3.2%) than rodent-feeding ticks (2.6%; 1.1%) or questing ticks (5.1%; 0%). Babesia spp. showed higher prevalence rates in ticks parasitizing birds (13.2%) and host-seeking ticks (10.7%), whereas ticks from small mammals were less frequently infected (6.6%). SFG rickettsiae and F. tularensis were also found in ticks collected off birds (2.1%; 1.2%), rodents (1.8%; 1.5%), and vegetation (4.1%; 1.6%). Various combinations of coinfections occurred in 10.9% of all positive ticks, indicating interaction of transmission cycles. Our results suggest that birds not only are important reservoirs for several pathogens but also act as vehicles for infected ticks and might therefore play a key role in the dispersal of tick-borne diseases.
Candidatus Neoehrlichia mikurensis is a newly emerging tick-borne bacterium from the family Anaplasmataceae. Its presence in Ixodes ricinus ticks was reported from various European countries, however, it’s ecology and co-circulation with another member of the same family, Anaplasma phagocytophilum has not been rigorously studied yet.
Candidatus N. mikurensis was detected in all sampling sites. In total, 4.5% of ticks were positive including larvae. The highest positivity was detected in Austria with a prevalence of 23.5%. The probability of Candidatus N. mikurensis occurrence increased with the proportion of ticks infected with Anaplasma phagocytophilum.
A positive association between the occurrences of Candidatus N. mikurensis and A. phagocytophilum indicates that both bacteria share similar ecology for their natural foci in Central Europe.
Candidatus Neoehrlichia mikurensis; Anaplasma phagocytophilum; Ixodes ricinus; Human granulocytic anaplasmosis; Neoehrlichiosis
Although Ixodes spp. are the most common ticks in North-Western Europe, recent reports indicated an expanding geographical distribution of Dermacentor reticulatus in Western Europe. Recently, the establishment of a D. reticulatus population in Belgium was described. D. reticulatus is an important vector of canine and equine babesiosis and can transmit several Rickettsia species, Coxiella burnetii and tick-borne encephalitis virus (TBEV), whilst Ixodes spp. are vectors of pathogens causing babesiosis, borreliosis, anaplasmosis, rickettsiosis and TBEV.
A survey was conducted in 2008-2009 to investigate the presence of different tick species and associated pathogens on dogs and cats in Belgium. Ticks were collected from dogs and cats in 75 veterinary practices, selected by stratified randomization. All collected ticks were morphologically determined and analysed for the presence of Babesia spp., Borrelia spp., Anaplasma phagocytophilum and Rickettsia DNA.
In total 2373 ticks were collected from 647 dogs and 506 cats. Ixodes ricinus (76.4%) and I. hexagonus (22.6%) were the predominant species. Rhipicephalus sanguineus (0.3%) and D. reticulatus (0.8%) were found in low numbers on dogs only. All dogs infested with R. sanguineus had a recent travel history, but D. reticulatus were collected from a dog without a history of travelling abroad. Of the collected Ixodes ticks, 19.5% were positive for A. phagocytophilum and 10.1% for Borrelia spp. (B. afzelii, B. garinii, B. burgdorferi s.s., B. lusitaniae, B. valaisiana and B. spielmanii). Rickettsia helvetica was found in 14.1% of Ixodes ticks. All Dermacentor ticks were negative for all the investigated pathogens, but one R. sanguineus tick was positive for Rickettsia massiliae.
D. reticulatus was confirmed to be present as an indigenous parasite in Belgium. B. lusitaniae and R. helvetica were detected in ticks in Belgium for the first time.
Ticks; Dermacentor reticulatus; Dogs; Cats; Belgium; Borrelia; Anaplasma; Rickettsia
Worldwide, ticks are important vectors of human and animal pathogens. Besides Lyme Borreliosis, a variety of other bacterial and protozoal tick-borne infections are of medical interest in Europe. In this study, 553 questing and feeding Ixodes ricinus (n = 327) and Dermacentor reticulatus ticks (n = 226) were analysed by PCR for Borrelia, Rickettsia, Anaplasma, Coxiella, Francisella and Babesia species. Overall, the pathogen prevalence in ticks was 30.6% for I. ricinus and 45.6% for D. reticulatus. The majority of infections were caused by members of the spotted-fever group rickettsiae (24.4%), 9.4% of ticks were positive for Borrelia burgdorferi sensu lato, with Borrelia afzelii being the most frequently detected species (40.4%). Pathogens with low prevalence rates in ticks were Anaplasma phagocytophilum (2.2%), Coxiella burnetii (0.9%), Francisella tularensis subspecies (0.7%), Bartonella henselae (0.7%), Babesia microti (0.5%) and Babesia venatorum (0.4%). On a regional level, hotspots of pathogens were identified for A. phagocytophilum (12.5–17.2%), F. tularensis ssp. (5.5%) and C. burnetii (9.1%), suggesting established zoonotic cycles of these pathogens at least at these sites. Our survey revealed a high burden of tick-borne pathogens in questing and feeding I. ricinus and D. reticulatus ticks collected in different regions in Belarus, indicating a potential risk for humans and animals. Identified hotspots of infected ticks should be included in future surveillance studies, especially when F. tularensis ssp. and C. burnetii are involved.
In Europe, ixodid ticks are important arthropod vectors of human and animal pathogens, but comprehensive studies of the prevalence of all relevant pathogens in Central Europe are scarce. As a result of ecological changes, the incidences of tick-borne infections are expected to increase. In this study, 1,394 nymphal and adult Ixodes ricinus ticks sampled monthly during the active season from 33 ecologically distinct collection sites throughout Luxembourg were screened for all human tick-borne pathogens relevant in Central Europe. Species were identified by sequence analysis of detection PCR amplicons. Mean infection rates of ticks were 11.3% for Borrelia burgdorferi sensu lato, 5.1% for Rickettsia sp., 2.7% for Babesia sp., and 1.9% for Anaplasma phagocytophilum. No tick was found to be infected with Coxiella sp., Francisella tularensis subsp., or Tick-borne encephalitis virus (TBEV). A total of 3.2% of ticks were infected with more than one pathogen species, including mixed Borrelia infections (1.5%). Seasonal variations of tick infection rates were observed for Borrelia, Babesia, and Anaplasma, possibly reflecting a behavioral adaptation strategy of questing ticks. A positive correlation between the grade of urbanization and Borrelia infection rate of ticks was observed, suggesting an established urban zoonotic cycle. We also found Hepatozoon canis (0.1%) and Bartonella henselae (0.3%), which so far have not been found in questing Ixodes ricinus ticks in Central Europe.
DNA analysis of blood meals from unfed nymphal Ixodes ricinus allows for the identification of tick host and tick-borne pathogens in the host species. The recognition of host species for tick larvae and the reservoirs of Borrelia, Rickettsia and Anaplasma species were simultaneously carried out by analysis of the blood meals of 880 questing nymphal I. ricinus ticks collected in forest parks of Szczecin city and rural forests in northwestern Poland that are endemic areas for Lyme borreliosis. The results obtained from the study indicate that I. ricinus larvae feed not only on small or medium animals but also on large animals and they (i.e. roe deer, red deer and wild boars) were the most prevalent in all study areas as the essential hosts for larvae of I. ricinus. The composition of medium and small vertebrates (carnivores, rodents, birds and lizards) provided a more diverse picture depending on study site. The reservoir species that contain the most pathogens are the European roe deer Capreolus capreolus, in which two species of Rickettsia and two species of Borrelia were identified, and Sus scrofa, in which one Rickettsia and three Borrelia species were identified. Rickettsia helvetica was the most common pathogen detected, and other included species were the B. burgdorferi s.l. group and B. miyamotoi related to relapsing fever group. Our results confirmed a general association of B. garinii with birds but also suggested that such associations may be less common in the transmission cycle in natural habitats than what was thought previously.
Blood meal; Borrelia; Anaplasma; Rickettsia; Reservoir; Ixodes ricinus
Neoehrlichia mikurensis s an emerging and vector-borne zoonosis: The first human disease cases were reported in 2010. Limited information is available about the prevalence and distribution of Neoehrlichia mikurensis in Europe, its natural life cycle and reservoir hosts. An Ehrlichia-like schotti variant has been described in questing Ixodes ricinus ticks, which could be identical to Neoehrlichia mikurensis.
Three genetic markers, 16S rDNA, gltA and GroEL, of Ehrlichia schotti-positive tick lysates were amplified, sequenced and compared to sequences from Neoehrlichia mikurensis. Based on these DNA sequences, a multiplex real-time PCR was developed to specifically detect Neoehrlichia mikurensis in combination with Anaplasma phagocytophilum in tick lysates. Various tick species from different life-stages, particularly Ixodes ricinus nymphs, were collected from the vegetation or wildlife. Tick lysates and DNA derived from organs of wild rodents were tested by PCR-based methods for the presence of Neoehrlichia mikurensis. Prevalence of Neoehrlichia mikurensis was calculated together with confidence intervals using Fisher's exact test.
The three genetic markers of Ehrlichia schotti-positive field isolates were similar or identical to Neoehrlichia mikurensis. Neoehrlichia mikurensis was found to be ubiquitously spread in the Netherlands and Belgium, but was not detected in the 401 tick samples from the UK. Neoehrlichia mikurensis was found in nymphs and adult Ixodes ricinus ticks, but neither in their larvae, nor in any other tick species tested. Neoehrlichia mikurensis was detected in diverse organs of some rodent species. Engorging ticks from red deer, European mouflon, wild boar and sheep were found positive for Neoehrlichia mikurensis.
Ehrlichia schotti is similar, if not identical, to Neoehrlichia mikurensis. Neoehrlichia mikurensis is present in questing Ixodes ricinus ticks throughout the Netherlands and Belgium. We propose that Ixodes ricinus can transstadially, but not transovarially, transmit this microorganism, and that different rodent species may act as reservoir hosts. These data further imply that wildlife and humans are frequently exposed to Neoehrlichia mikurensis-infected ticks through tick bites. Future studies should aim to investigate to what extent Neoehrlichia mikurensis poses a risk to public health.
Vector-borne disease; Emerging zoonoses; Candidatus N. mikurensis; I. ricinus; Anaplasma phagocytophylum
Tick-borne Anaplasma phagocytophilum and Rickettsia spp. are considered to be emerging human pathogens, but only limited data are available on their occurrence in Sweden. Two real-time PCR assays followed by nested PCR and sequence analysis were carried out to investigate the prevalence of A. phagocytophilum and spotted fever rickettsiae in ticks from seven areas in Sweden.
In 139 pooled samples, representing a total of 1245 Ixodes ricinus ticks (204 larvae, 963 nymphs, 38 males, 40 females), the overall positive mean infection prevalence was 1.3-15.0% for A. phagocytophilum and 1.5-17.3% for R. helvetica. A. phagocytophilum was only detected in nymphs (1.7-19.4%), whereas R. helvetica was detected in all three tick stages. Support for vertical and transstadial transmission was only obtained for R. helvetica. Both agents showed similar infection rates across study areas, although infection rates were greater in coastal areas.
The results show that both pathogens occurred in all seven locations, indicating that they are prevalent in Sweden and should be considered etiological agents in patients recently bitten by ticks.
“Candidatus Neoehrlichia mikurensis” (Anaplasmataceae) is an emerging pathogen transmitted by Ixodes ticks. Conventional PCR and the newly developed high-resolution melt PCR were used to detect and discriminate “Candidatus Neoehrlichia mikurensis” and Anaplasma phagocytophilum. Both bacterial species were frequently found in Ixodes ricinus and Ixodes hexagonus but virtually absent from Dermacentor reticulatus. In rodents, “Candidatus N. mikurensis” was significantly more prevalent than A. phagocytophilum, whereas in cats, only A. phagocytophilum was found.
The aims of this study were to evaluate the host-tick-pathogen interface of Babesia spp. and Anaplasma phagocytophilum in restored areas in both questing and host-attached Ixodes ricinus and Dermacentor reticulatus and their small mammalian hosts.
Questing ticks were collected from 5 sites within the city of Leipzig, Germany, in 2009. Small mammals were trapped at 3 of the 5 sites during 2010 and 2011. DNA extracts of questing and host-attached I. ricinus and D. reticulatus and of several tissue types of small mammals (the majority bank voles and yellow-necked mice), were investigated by PCR followed by sequencing for the occurrence of DNA of Babesia spp. and by real-time PCR for A. phagocytophilum. A selected number of samples positive for A. phagocytophilum were further investigated for variants of the partial 16S rRNA gene. Co-infection with Rickettsia spp. in the questing ticks was additionally investigated.
4.1% of questing I. ricinus ticks, but no D. reticulatus, were positive for Babesia sp. and 8.7% of I. ricinus for A. phagocytophilum. Sequencing revealed B. microti, B. capreoli and Babesia spp. EU1 in Leipzig and sequence analysis of the partial 16S RNA gene of A. phagocytophilum revealed variants either rarely reported in human cases or associated with cervid hosts. The statistical analysis revealed significantly less ticks infected with A. phagocytophilum in a city park in Leipzig as compared to the other sampling sites. A. phagocytophilum-DNA was detected in 2 bank voles, DNA of B. microti in 1 striped field-mouse and of Babesia sp. EU1 in the skin tissue of a mole. Co-infections were detected.
Our results show the involvement of small mammals in the natural endemic cycles of tick-borne pathogens. A more thorough understanding of the interactions of ticks, pathogens and hosts is the essential basis for effective preventive control measures.
Babesia spp; Anaplasma phagocytophilum; Ixodes ricinus; Dermacentor reticulatus; Bank vole; Yellow-necked mouse; Recreational area; Host survey; Vector-host relation
Lyme borreliosis is the most prevalent tick-borne disease in Europe. Ixodes ricinus also carries other pathogenic bacteria, but corresponding human diseases are rarely reported. Here, we compared the exposure to Rickettsia helvetica and Rickettsia monacensis with that to Lyme borreliosis spirochetes. We assumed that their exposure corresponds to their infection rate in questing I. ricinus.
Three Rickettsia species were detected in ticks with a total prevalence of 7.9%, of which the majority was R. helvetica (78%) and R. monacensis (21%). From the same geographic area, skin biopsies of erythema migrans patients were investigated for possible co-infections with Rickettsia spp.. Forty-seven out of 67 skin biopsies were PCR positive for Borrelia burgdorferi s.l. and one sample was positive for R. monacensis. The Borrelia genospecies from the R. monacensis positive patient was identified as Borrelia afzelii. The patient did not show any symptoms associated with rickettsiosis.
Co-infections of I. ricinus with Rickettsia spp. and B. burgdorferi s.l. were as high as expected from the individual prevalence of both pathogens. Co-infection rate in erythema migrans patients corresponded well with tick infection rates. To our knowledge, this is the first reported co-infection of B. afzelii and R. monacensis.
Borrelia burgdorferi; Rickettsia monacensis; Rickettsia helvetica; Erythema migrans; Co-infection
Candidatus Neoehrlichia mikurensis (CNM) has been described in the hard tick Ixodes ricinus and rodents as well as in some severe cases of human disease. The aims of this study were to identify DNA of CNM in small mammals, the ticks parasitizing them and questing ticks in areas with sympatric existence of Ixodes ricinus and Dermacentor reticulatus in Germany.
Blood, transudate and organ samples (spleen, kidney, liver, skin) of 91 small mammals and host-attached ticks from altogether 50 small mammals as well as questing I. ricinus ticks (n=782) were screened with a real-time PCR for DNA of CNM.
52.7% of the small mammals were positive for CNM-DNA. The majority of the infected animals were yellow-necked mice (Apodemus flavicollis) and bank voles (Myodes glareolus). Small mammals with tick infestation were more often infected with CNM than small mammals without ticks. Compared with the prevalence of ~25% in the questing I. ricinus ticks, twice the prevalence in the rodents provides evidence for their role as reservoir hosts for CNM.
The high prevalence of this pathogen in the investigated areas in both rodents and ticks points towards the need for more specific investigation on its role as a human pathogen.
Candidatus Neoehrlichia mikurensis; Bank vole; Yellow-necked mouse; Ixodes ricinus; Dermacentor reticulatus; Recreational area; Host survey; Vector-host relation
The importance of Ixodes ricinus in the transmission of tick-borne pathogens is well recognized in the United Kingdom and across Europe. However, the role of coexisting Ixodes species, such as the widely distributed species Ixodes trianguliceps, as alternative vectors for these pathogens has received little attention. This study aimed to assess the relative importance of I. ricinus and I. trianguliceps in the transmission of Anaplasma phagocytophilum and Babesia microti among United Kingdom field voles (Microtus agrestis), which serve as reservoir hosts for both pathogens. While all instars of I. trianguliceps feed exclusively on small mammals, I. ricinus adults feed primarily on larger hosts such as deer. The abundance of both tick species and pathogen infection prevalence in field voles were monitored at sites surrounded with fencing that excluded deer and at sites where deer were free to roam. As expected, fencing significantly reduced the larval burden of I. ricinus on field voles and the abundance of questing nymphs, but the larval burden of I. trianguliceps was not significantly affected. The prevalence of A. phagocytophilum and B. microti infections was not significantly affected by the presence of fencing, suggesting that I. trianguliceps is their principal vector. The prevalence of nymphal and adult ticks on field voles was also unaffected, indicating that relatively few non-larval I. ricinus ticks feed upon field voles. This study provides compelling evidence for the importance of I. trianguliceps in maintaining these enzootic tick-borne infections, while highlighting the potential for such infections to escape into alternative hosts via I. ricinus.
Ixodes ricinus ticks transmit Babesia species to vertebrate hosts. Using molecular tools we were able to detect the presence of this piroplasmid in its vector. The aims of this study were to investigate the prevalence and identity of Babesia species in questing ticks collected in various areas of Norway.
DNA from questing l. ricinus ticks were examined with a realtime PCR for the presence of Babesia. Positive samples of tick DNA were identified to species using PCR, and sequence analysis.
From a total of 1908 questing l. ricinus ticks, 17 (0.9%) indicated the presence of Babesia spp. after realtime-PCR screening. Ixodes ricinus harbouring Babesia spp. was detected in 9 out of 22 localities. Further molecular analyses of DNA from these positive ticks indicate the presence of Babesia venatorum, B. divergens, B. capreoli and a currently undescribed Babesia in Norwegian ticks. The most prevalent was B. venatorum found in 71% of the positive ticks.
A total of 17 out of 1908 (0.9%) ticks were positive for Babesia. Our data confirm that there are several Babesia species in ticks in Norway. Babesia venatorum was the most prevalent. This species has a zoonotic potential and may cause human babesiosis following a tick bite.
Babesia spp; Questing Ixodes ricinus; Zoonosis; Piroplasmosis; Realtime PCR; Prevalence; Sequencing
Concurrent infections with vector-borne pathogens affected a cattle herd in Switzerland, and one of the pathogens was identified as Babesia bigemina, which had never been observed in this country before. Therefore, a survey of the occurrence of ruminant Babesia spp. and their tick vectors in Switzerland was conducted. A total of 2,017 ticks were collected from sheep, goats, cattle, and wild ruminants (deer, roe deer, and chamois) in southern parts of Switzerland and identified morphologically. The vast majority of the ticks (99.2%) were Ixodes ricinus, but 14 ticks from sheep and goats were identified as Dermacentor marginatus and two ticks from wild ruminants were identified as Hemaphysalis punctata. PCR analyses of 700 ticks revealed the presence of Babesia divergens (n = 6), Babesia sp. genotype EU1 (n = 14), and B. major (n = 2), whose suggested occurrence was confirmed in this study by molecular analysis, and the presence of novel Babesia sp. genotype CH1 (n = 4), which is closely related to B. odocoilei and to Babesia sp. genotype RD61 reported from North America. The identification of B. divergens and B. major in ticks collected from wild ruminants cast doubt on the postulated strict host specificity of these bovine Babesia species. Furthermore, the zoonotic Babesia sp. genotype EU1 was detected in ticks collected from domestic animals but was obtained predominantly from ticks collected from wild ruminants. More than one tick containing DNA of different Babesia spp. were collected from two red deer. Hence, the role of these game animals as reservoir hosts of Babesia spp. seems to be important but requires further investigation.
Ixodes spp. tick-borne zoonotic diseases are present across the Holarctic in humans, domestic animals, and wildlife. Small mammals are reservoirs for the rickettsial pathogen Anaplasma phagocytophilum and tick vectors may include catholic-feeding bridge vectors as well as host-specialist or nidicolous ticks. Far western North American communities in which A. phagocytophilum is maintained are complex ecologically, with multiple reservoir host and tick species, multiple strains of the bacterial pathogen A. phagocytophilum and differences in dynamics of hosts and vectors across heterogeneous landscapes. We evaluated sites in northern California in order to identify primarily nidicolous ticks and the hosts they infest. A total of 667 ticks was found in 11 study sites, including 288 on flags and 379 attached to small mammals. Larvae were over-represented among attached ticks and adults on flags. The most abundant species was I. pacificus. Two-hundred fourteen nidicolous ticks were found, most abundantly I. angustus and I. spinipalpis. All adult I. ochotonae, I. auritulus, I. angustus, I. jellisoni, and I. woodi were female, while the male:female ratio of I. spinipalpis was 1.2:1 and 1:1 for I. pacificus. The greatest number of ticks was obtained from Tamias ochrogenys, Peromyscus spp., and Neotoma fuscipes. Of 234 small mammal individuals that were infested with Ixodes spp., only 81 (34.6%) were infested with I. pacificus. The remaining infested small mammals hosted nidicolous tick species. Eight ticks were PCR-positive, including 6 I. pacificus (one adult, one larva, and 6 nymphs), and 2 adult I. ochotonae and high PCR prevalences of 18% and 9% were detected in woodrats and chipmunks, respectively. Nymphal I. angustus ticks were active year-long with a possible increase in August while larval activity was only observed in December and spring months and adults only during spring and fall. Overall, we show high tick species richness and year-round high levels of infestation on rodents by several different nidicolous ticks in areas where A. phagocytophilum is enzootic, including on reported reservoir species.
Anaplasma phagocytophilum; Granulocytic anaplasmosis; Ixodes angustus; Ixodes ochotonae; Ixodes pacificus
Understanding the variation in prevalence of Borrelia burgdorferi sensu lato (Lyme Borreliosis Spirochaetes, LBS) and Anaplasma phagocytophilum (causing tick-borne fever in ruminants and human granulocytic ehrlichiosis) in ticks is vital from both a human and an animal disease perspective to target the most effective mitigation measures. From the host competence hypothesis, we predicted that prevalence of LBS would decrease with red deer density, while prevalence of A. phagocytophilum would increase.
Based on a sample of 112 adult and 686 nymphal Ixodes ricinus ticks collected with flagging during questing from 31 transects (4–500 m long) corresponding to individual seasonal home ranges of 41 red deer along the west coast of Norway, we tested whether there were spatial and seasonal variations in prevalence with a special emphasis on the population density of the most common large host in this area, the red deer (Cervus elaphus). We used a multiplex real-time PCR assay for detection of A. phagocytophilum and LBS.
Prevalence of LBS was higher in adult female ticks (21.6%) compared to adult male ticks (11.5%) and nymphs (10.9%), while prevalence was similar among stages for prevalence of A. phagocytophilum (8.8%). Only partly consistent with predictions, we found a lower prevalence of LBS in areas of high red deer density, while there was no relationship between red deer density and prevalence of A. phagocytophilum in ticks. Prevalence of both bacteria was much higher in ticks questing in May compared to August.
Our study provides support to the notion that spatial variation in host composition forms a role for prevalence of LBS in ticks also in a northern European ecosystem, while no such association was found for A. phagocytophilum. Further studies are needed to fully understand the similar seasonal pattern of prevalence of the two pathogens.
Anaplasma; Borrelia; Dilution effects; Host competence hypothesis; Ixodes ricinus; Lyme Borreliosis Spirochaetes; Prevalence; Red deer; Rodents; Ticks
Recent advances in climate research together with a better understanding of tick–pathogen interactions, the distribution of ticks and the diagnosis of tick-borne pathogens raise questions about the impact of environmental factors on tick abundance and spread and the prevalence and transmission of tick-borne pathogens. While undoubtedly climate plays a role in the changes in distribution and seasonal abundance of ticks, it is always difficult to disentangle factors impacting on the abundance of tick hosts from those exerted by human habits. All together, climate, host abundance, and social factors may explain the upsurge of epidemics transmitted by ticks to humans. Herein we focused on tick-borne pathogens that affect humans with epidemic potential. Borrelia burgdorferi s.l. (Lyme disease), Anaplasma phagocytophilum (human granulocytic anaplasmosis), and tick-borne encephalitis virus (tick-borne encephalitis) are transmitted by Ixodes spp. Crimean–Congo hemorrhagic fever virus (Crimean–Congo hemorrhagic fever) is transmitted by Hyalomma spp. In this review, we discussed how vector tick species occupy the habitat as a function of different climatic factors, and how these factors impact on tick survival and seasonality. How molecular events at the tick–pathogen interface impact on pathogen transmission is also discussed. Results from statistically and biologically derived models are compared to show that while statistical models are able to outline basic information about tick distributions, biologically derived models are necessary to evaluate pathogen transmission rates and understand the effect of climatic variables and host abundance patterns on pathogen transmission. The results of these studies could be used to build early alert systems able to identify the main factors driving the subtle changes in tick distribution and seasonality and the prevalence of tick-borne pathogens.
tick; model; genetics; climate; Borrelia; Anaplasma; virus