Anaplasma phagocytophilum and Rickettsia spp. infections in hard ticks (Ixodes ricinus) in the city of Hanover (Germany): revisited

Borrelia spp. and Anaplasma phagocytophilum in ruminant ticks - Borrelia prevalence declines only in female, but not nymphal ticks feeding on cervids

Tick-borne pathogen epidemiology involves vectors, in Europe mainly Ixodes ricinus, and vertebrate hosts. Ruminants are reservoirs for Anaplasma phagocytophilum, but not for Borrelia burgdorferi sensu lato (s.l.), possibly clearing the infection from ticks. However, such clearance is epidemiologically relevant mainly in nymphal ticks. Of 1874 ticks collected from wildlife in the present study, 1535 Ixodes spp. (796 nymphs, 739 females) were tested by qPCR, with a proportion of 26.3% (nymphs: 24.5%, females: 28.3%) positive for Borrelia spp. and 87.4% for A. phagocytophilum (nymphs: 62.8%, females: 92.4%). In female Ixodes spp. from deer (N = 720), but not nymphs (N = 785), the Borrelia frequency declined significantly with increasing engorgement duration as inferred by the coxal index. Borrelia spp. differentiation revealed B. burgdorferi s.l. in nine and B. miyamotoi in one of ten successfully analysed ticks having engorged for <48 hours, but only three B. burgdorferi s.l.- vs. six B. miyamotoi-positive and one coinfected tick among ten ticks with a longer engorgement. Borrelia copy numbers showed a U-shaped relationship with engorgement duration. Increasing A. phagocytophilum frequency during the rapid feeding phase in nymphs, and increasing copy numbers in females from deer confirmed their reservoir function. Of 101 I. ricinus from cattle, 4.0% were positive for Borrelia, whereby the species could not be determined, and 42.6% for A. phagocytophilum. In comparison, 13.8% and 11.9% of 428 questing ticks from the pastures were Borrelia- and A. phagocytophilum-positive, respectively. The results imply that feeding on cervids may not reduce Borrelia prevalence in nymphs, presumably due to the low overall blood volume ingested, insufficient for Borrelia clearance in this epidemiologically relevant stage. Further studies need to confirm that deer-fed nymphs contain infectious Borrelia and maintain the infection transstadially.

Molecular Detection of Anaplasma phagocytophilum in Cats in Europe and Associated Risk Factors

Infections with Anaplasma (A.) phagocytophilum in cats seem to be rare. The study aimed to determine whether infections in cats are underestimated and to identify the risk factors for infection. Blood samples of 1015 cats across Europe (2017-2022), sent to IDEXX Laboratories, Germany, were tested for A. phagocytophilum DNA. The influence of the cats' origin on A. phagocytophilum infection was assessed by univariable analysis, while multivariable logistic regression evaluated associations with the cats' sex and age, and the years, and seasonality of the samples' submission. Furthermore, univariable linear regression was used to determine patterns in PCR orders. The number of submitted samples increased significantly during the 6 years (p = 0.042). Anaplasma phagocytophilum DNA was detected in 76/1015 of cats (7.5%, 95% CI 6.0-9.3%). Infections were significantly more common in Northern compared to Central (p < 0.001, OR: 8.70) and Southern Europe (p < 0.001, OR: 39.94). A significantly higher likelihood for infections during the summer compared with winter (p = 0.047, OR: 3.13) was found. Bacteremia with A. phagocytophilum in European cats is not uncommon. Anaplasma phagocytophilum infection should be considered an important risk, particularly in Northern Europe. Effective tick prevention is crucial for managing feline health across Europe, not just in the Mediterranean region.

Prevalence of tick-borne bacterial pathogens in Germany-has the situation changed after a decade?

Introduction

Tick-borne pathogens, such as Borreliella spp., Rickettsia spp., and Anaplasma spp., are frequently detected in Germany. They circulate between animals and tick vectors and can cause mild to severe diseases in humans. Knowledge about distribution and prevalence of these pathogens over time is important for risk assessment of human and animal health.

Methods

Ixodes ricinus nymphs were collected at different locations in 2009/2010 and 2019 in Germany and analyzed for tick-borne pathogens by real-time PCR and sequencing.

Results

Borreliella spp. were detected with a prevalence of 11.96% in 2009/2010 and 13.10% in 2019 with B. afzelii and B. garinii as dominant species. Borrelia miyamotoi was detected in seven ticks and in coinfection with B. afzelii or B. garinii. Rickettsia spp. showed a prevalence of 8.82% in 2009/2010 and 1.68% in 2019 with the exclusive detection of R. helvetica. The prevalence of Anaplasma spp. was 1.00% in 2009/2010 and 7.01% in 2019. A. phagocytophilum was detected in seven tick samples. None of the nymphs were positive for C. burnetii.

Discussion

Here, observed changes in prevalence were not significant after a decade but require longitudinal observations including parameters like host species and density, climatic factors to improve our understanding of tick-borne diseases.

Endemisation and management of Babesia divergens on a beef production farm

The hard tick Ixodes ricinus transmits a variety of zoonotic pathogens, including Babesia divergens, the most common cause of bovine babesiosis in northern Europe. In endemic areas, cattle are rarely clinically affected, as animals up to the age of nine months are resistant against relevant clinical disease and develop protective premunity. However, outbreaks in immunologically naïve herds may lead to considerable losses. Such an outbreak with a high mortality rate occurred in 2018 on a northern German beef production farm, as previously reported. The present study provides an update on the epidemiological situation and management strategy of the farm. In spring 2022, blood samples were taken from 46 animals for PCR and serological testing before pasture turnout. Although no clinical cases had been noticed since 2019, B. divergens DNA was detected by quantitative real-time PCR (qPCR), followed by amplification and sequencing of the 18S rRNA gene, in 6.5% (3/46) of cattle blood samples. Presence of anti-B. divergens antibodies was confirmed in 26.1% (12/46) of animals, while further 10.9% (5/46) had a borderline antibody titre. The antibody status of 23 of these animals had already been determined in 2018 and/or 2020, revealing fluctuating titre patterns indicative of repeated pathogen exposure. Moreover, 457 questing I. ricinus specimens collected on the farm's pastures and 83 I. ricinus specimens detached from cattle were screened for Babesia spp. DNA by qPCR, followed by 18S rDNA amplification and sequencing. Endemisation of B. divergens was confirmed by 0.9% (4/457) positive questing I. ricinus, while the ticks detached from cattle were Babesia-negative. The farm's management strategy includes annual metaphylactic treatment with imidocarb dipropionate during the main tick exposure period in spring. However, the antibody titre fluctuations and the persistent infections at the end of the housing period indicate that the absence of clinical disease is primarily due to a rising level of premunity. Metaphylactic treatment with imidocarb seems to be a suitable management option to protect newly acquired immunologically naïve animals. The endemisation of B. divergens is also of public health significance, as the pastures are located close to a tourist destination in a popular hiking area.

Frequency of Anaplasma phagocytophilum, Borrelia spp., and coinfections in Ixodes ricinus ticks collected from dogs and cats in Germany

BACKGROUND

Changing geographical and seasonal activity patterns of ticks may increase the risk of tick infestation and tick-borne pathogen (TBP) transmission for both humans and animals.

METHODS

To estimate TBP exposure of dogs and cats, 3000 female I. ricinus from these hosts were investigated for Anaplasma phagocytophilum and Borrelia species.

RESULTS

qPCR inhibition, which was observed for ticks of all engorgement stages but not questing ticks, was eliminated at a template volume of 2 µl. In ticks from dogs, A. phagocytophilum and Borrelia spp. prevalence amounted to 19.0% (285/1500) and 28.5% (427/1500), respectively, while ticks from cats showed significantly higher values of 30.9% (464/1500) and 55.1% (827/1500). Accordingly, the coinfection rate with both A. phagocytophilum and Borrelia spp. was significantly higher in ticks from cats (17.5%, 262/1500) than dogs (6.9%, 104/1500). Borrelia prevalence significantly decreased with increasing engorgement duration in ticks from both host species, whereas A. phagocytophilum prevalence decreased only in ticks from dogs. While A. phagocytophilum copy numbers in positive ticks did not change significantly over the time of engorgement, those of Borrelia decreased initially in dog ticks. In ticks from cats, copy numbers of neither A. phagocytophilum nor Borrelia spp. were affected by engorgement. Borrelia species differentiation was successful in 29.1% (365/1254) of qPCR-positive ticks. The most frequently detected species in ticks from dogs were B. afzelii (39.3% of successfully differentiated infections; 70/178), B. miyamotoi (16.3%; 29/178), and B. valaisiana (15.7%; 28/178), while B. afzelii (40.1%; 91/227), B. spielmanii (21.6%; 49/227), and B. miyamotoi (14.1%; 32/227) occurred most frequently in ticks from cats.

CONCLUSIONS

The differences in pathogen prevalence and Borrelia species distribution between ticks collected from dogs and cats may result from differences in habitat overlap with TBP reservoir hosts. The declining prevalence of A. phagocytophilum with increasing engorgement duration, without a decrease in copy numbers, could indicate transmission to dogs over the time of attachment. The fact that this was not observed in ticks from cats may indicate less efficient transmission. In conclusion, the high prevalence of A. phagocytophilum and Borrelia spp. in ticks collected from dogs and cats underlines the need for effective acaricide tick control to protect both animals and humans from associated health risks.

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

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

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

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

Co-Infection of Potential Tick-Borne Pathogens of the Order Rickettsiales and Borrelia burgdorferi s. l. and Their Link to Season and Area in Germany

The prevalence of potential human pathogenic members of the order Rickettsiales differs between Borrelia burgdorferi sensu lato-positive and -negative tick microbiomes. Here, co-infection of members of the order Rickettsiales, such as Rickettsia spp., Anaplasma phagocytophilum, Wolbachia pipientis, and Neoehrlichia mikurensis as well as B. burgdorferi s.l. in the tick microbiome was addressed. This study used conventional PCRs to investigate the diversity and prevalence of the before-mentioned bacteria in 760 nucleic acid extracts of I. ricinus ticks detached from humans, which were previously tested for B. burgdorferi s.l.. A gltA gene-based amplicon sequencing approach was performed to identify Rickettsia species. The prevalence of Rickettsia spp. (16.7%, n = 127) and W. pipientis (15.9%, n = 121) were similar, while A. phagocytophilum was found in 2.8% (n = 21) and N. mikurensis in 0.1% (n = 1) of all ticks. Co-infection of B. burgdorferi s. l. with Rickettsia spp. was most frequent. The gltA gene sequencing indicated that Rickettsia helvetica was the dominant Rickettsia species in tick microbiomes. Moreover, R, monacensis and R. raoultii were correlated with autumn and area south, respectively, and a negative B. burgdorferi s. l. finding. Almost every fifth tick carried DNA of at least two of the human pathogenic bacteria studied here.

Revealing the Tick Microbiome: Insights into Midgut and Salivary Gland Microbiota of Female Ixodes ricinus Ticks

The ectoparasite Ixodes ricinus is an important vector for many tick-borne diseases (TBD) in the northern hemisphere, such as Lyme borreliosis, rickettsiosis, human granulocytic anaplasmosis, or tick-borne encephalitis virus. As climate change will lead to rising temperatures in the next years, we expect an increase in tick activity, tick population, and thus in the spread of TBD. Consequently, it has never been more critical to understand relationships within the microbial communities in ticks that might contribute to the tick's fitness and the occurrence of TBD. Therefore, we analyzed the microbiota in different tick tissues such as midgut, salivary glands, and residual tick material, as well as the microbiota in complete Ixodes ricinus ticks using 16S rRNA gene amplicon sequencing. By using a newly developed DNA extraction protocol for tick tissue samples and a self-designed mock community, we were able to detect endosymbionts and pathogens that have been described in the literature previously. Further, this study displayed the usefulness of including a mock community during bioinformatic analysis to identify essential bacteria within the tick.

15-year Borrelia prevalence and species distribution monitoring in Ixodes ricinus/inopinatus populations in the city of Hanover, Germany

Lyme borreliosis, caused by Borrelia burgdorferi sensu lato (s.l.) spirochaetes, is the most common tick-borne disease (TBD) in the Northern Hemisphere. Rising incidences indicate that its epidemiology may be affected by global changes. Therefore, the current study aimed to assess changes in tick infection rates with Borrelia spp. over a 15-year monitoring period in the city of Hanover, Germany, as a follow-up to previous prevalence studies (years 2005, 2010 and 2015). To assess the epidemiological risk, ticks of the Ixodes ricinus/inopinatus-complex were sampled from April to October 2020 by the flagging method at 10 frequently visited recreation areas in Hanover. Analysis by quantitative real-time PCR of 2100 individual ticks revealed an overall Borrelia prevalence of 25.5% (535/2100). Regarding different tick developmental stages, nymphs showed a significantly lower Borrelia prevalence (18.4% [193/1050]) than adult ticks (32.6% [342/1050]). Comparison with previous years revealed a stable total Borrelia prevalence along with consistent infection rates in the different developmental stages over the 15-year monitoring period. Borrelia species differentiation by Reverse Line Blot was successful in 67.3% of positive ticks collected in 2020, with B. afzelii being the dominating species (59.2% of the differentiated infections), besides B. burgdorferi sensu stricto (s.s.), B. garinii, B. valaisiana, B. spielmanii, B. bavariensis and B. bissettiae and the relapsing fever spirochaete B. miyamotoi. Additionally, the proportion of infections attributed to B. afzelii showed a significant increase in 2020 compared to 2005 and 2015 (59.2% vs. 37.6% and 32.0% of successfully differentiated infections, respectively). Coinfections with Anaplasma phagocytophilum and Rickettsia spp. stayed stable comparing 2020 with previous years. Therefore, although changes in the Borrelia prevalence in questing ticks were not observed throughout the 15-year monitoring period, shifts in Borrelia species distribution may alter the epidemiological risk.

Borrelia Infections in Ageing Ticks: Relationship with Morphometric Age Ratio in Field-Collected Ixodes ricinus Nymphs

In Europe, Ixodes ricinus plays a major role as a vector of Borrelia burgdorferi sensu lato (s.l.) spirochaetes, the causative agents of Lyme borreliosis, among other pathogens. In unfed ticks, Borrelia spirochaetes experience prolonged nutrient restriction. However, only few studies exist with regard to Borrelia infections in unfed ticks of different physiological ages. Changing body dimensions of unfed ticks, due to the consumption of energy reserves, allow physiological age estimation. The present study investigated the relationship of morphometric age with Borrelia prevalence and spirochaete load in 1882 questing I. ricinus nymphs, collected at two different locations in northern Germany in 2020. In addition, Borrelia species composition was investigated by employing a reverse line blot (RLB) probe panel suitable for the detection of ten different B. burgdorferi s.l. species, as well as the relapsing-fever spirochaete B. miyamotoi. Overall, Borrelia prevalence was 25.8% (485/1882). Whilst there was no statistically significant difference in Borrelia prevalence between the different morphometric age groups, Borrelia infection intensity as determined by probe-based quantitative real-time PCR significantly declined with increasing morphometric age. Borrelia species differentiation by RLB was successful in 29.5% of positive ticks, and revealed B. afzelii as the dominating species (65.0% of the differentiated infections). Additionally, B. garinii, B. valaisiana, B. burgdorferi sensu stricto, B. spielmanii, and B. miyamotoi were detected.

Regional, seasonal, biennial and landscape-associated distribution of Anaplasma phagocytophilum and Rickettsia spp. infections in Ixodes ticks in northern Germany and implications for risk assessment at larger spatial scales

Tick-associated Rickettsiales are important pathogens with relevance for public and animal health; therefore, knowledge regarding their distribution is essential for risk assessment and disease prevention. To investigate the prevalence of Anaplasma phagocytophilum and Rickettsia spp. in northern Germany, Ixodes ticks were flagged monthly from April to October in 2018 and 2019 at three collection sites each in the regions of Bremen, Emsland, Hanover, Kassel and Uelzen. A total of 3150 ticks (1052 females, 1048 males and 1050 nymphs) were individually examined for rickettsial infections using probe-based quantitative real-time PCR. Overall prevalence of A. phagocytophilum was 6.4 % (202/3150; 6.7 % [71/1052] in females, 7.5 % [79/1048] in males and 5.0 % [52/1050] in nymphs). For Rickettsia spp., the overall prevalence was 29.6 % (931/3150; 33.4 % [351/1052] in females, 28.3 % [297/1048] in males and 27.0 % [283/1050] in nymphs). Rickettsia species identification by real-time pyrosequencing on a subset of 409 positive samples was successful in 407 cases (99.5 %). Rickettsia helvetica was the predominant species with a detection rate of 99.8 % (406/407). Additionally, Rickettsia monacensis was detected in one tick (0.2 %). Generalized linear mixed models showed significant regional as well as monthly differences regarding the prevalence of both pathogens. In addition, the prevalence of both pathogens was significantly higher in 2018 (A. phagocytophilum: 8.0 % [126/1575], Rickettsia spp.: 35.4 % [558/1575]) than in 2019 (A. phagocytophilum: 4.8 % [76/1575], Rickettsia spp.: 23.9 % [373/1575]). In contrast, no effect of landscape type on pathogen prevalence was found. As Rickettsia spp.-detection was based on the single-copy gene gltA, it was possible to calculate the individual pathogen load per tick, which was significantly higher in female ticks than in nymphs (mean values: 8.19 × 10⁴ vs. 9.58 × 10³). Regional, seasonal and biennial prevalence differences of tick-transmitted Rickettsiales show the necessity to investigate ticks from multiple locations, over several months and in more than one year to reliably assess the infection risk on a larger geographical scale.

Emergence and Epidemiology of Bovine Babesiosis Due to Babesia divergens on a Northern German Beef Production Farm

Babesia divergens, transmitted by the tick Ixodes ricinus, is the most common cause of bovine babesiosis in northern Europe and plays a role as a zoonotic pathogen. However, several studies have indicated a decline of B. divergens prevalence in Europe during the last decades. Here, we investigate the epidemiology of bovine babesiosis on a beef production farm in northern Germany, which had not been affected by babesiosis until an initial outbreak in 2018. In June 2018, 21 adult cattle died, showing classical symptoms of babesiosis. Babesia divergens merozoites were detected in blood smears of clinically affected animals and the species was confirmed by PCR and sequencing of a part of the 18S rRNA gene. In 2018, screening of the farm's entire stock by PCR revealed that Babesia-positive animals were present in only one of five herds grazing on different pastures. In the following year, further babesiosis cases occurred in multiple herds. In March 2020, 95 cattle were tested for anti-B. divergens antibodies and 36 of them (37.89%) had positive titres. To investigate the local Babesia prevalence in ticks, 1,430 questing I. ricinus ticks (555 larvae, 648 nymphs, 227 adults) were collected on the farm's pastures and subjected to PCR for Babesia detection. Babesia divergens DNA could not be detected, but Babesia microti showed an overall prevalence of 0.49% (7/1,430; 0.88% [2/227] of adult ticks, 0.77% [5/648] of nymphs, 0.00% [0/555] of larvae). Babesia venatorum was detected in 0.42% (6/1,430) of ticks (0.44% [1/227] of adult ticks, 0.77% [5/648] of nymphs, 0.00% [0/555] of larvae) and B. capreoli in 0.07% (1/1,430) of ticks (0.00% [0/227] of adult ticks, 0.15% [1/648] of nymphs, 0.00% [0/555] of larvae). Despite the fact that no B. divergens-positive ticks were found, the collected data suggest a geographical spread of the pathogen on the farm. Bovine babesiosis remains a disease of veterinary importance in Europe and may cause considerable economic losses when (re-)emerging in non-endemic areas, especially as awareness for the disease among veterinarians and farmers declines.

Two-year monitoring of tick abundance and influencing factors in an urban area (city of Hanover, Germany)

Ticks may transmit a variety of human and animal pathogens. Prevalence of Borrelia spp., Rickettsia spp. and Anaplasma phagocytophilum in ticks has been monitored in the city of Hanover, Germany, since 2005. However, to determine the infection risk for humans and animals, not only pathogen prevalence, but also tick abundance and seasonality need to be taken into account. Therefore, the aim of this study was to investigate tick abundance at ten different collection sites in the city of Hanover, Germany. Collection of questing ticks was performed by the flagging method in the first and second half of each month during the tick season (April-October) in 2017 and 2018. At each 200 m² collection site, one of four 50 m² fields was sampled per visit on a rotational basis, resulting in 100 m² sampled per month. In addition, data on weather conditions, near-ground temperature, relative humidity and vegetation composition were noted at each collection event. In 2017, a total of 1770 ticks were collected, while 1866 ticks were collected in 2018. Ixodes ricinus was the most prevalent species (97.0 % of all ticks, 98.0 % of nymphs, 91.6 % of adults) followed by I. inopinatus (2.3 % of all ticks, 1.1 % of nymphs, 8.0 % of adults), I. frontalis (0.6 % of all ticks, 0.6 % of nymphs, 0.3 % of adults) and I. hexagonus (0.03 % of all ticks, 0.03 % of nymphs, 0.0 % of adults). Using generalized linear mixed modeling, density of I. ricinus and I. inopinatus in 2017 was significantly higher than in 2018. Regarding different landscape types, ticks were significantly more abundant in mixed forests than in parks, with more than 50 ticks/100 m² on average in both years. In urban parks, average tick density amounted to 15 ticks/100 m² in 2017 and 11 ticks/100 m² in 2018 and in broad-leaved forests average tick density was 13 and 18 ticks/100 m² in 2017 and 2018, respectively. Tick density showed a marked peak in June 2017 and in May 2018 at most sites, whereas a less pronounced peak was recognizable in September. Tick density varied considerably between collection sites. However, no statistically significant effect of (micro-)climatic variables, including near-ground temperature, relative humidity and saturation deficit, was found. Thus, further factors, such as the abundance of wildlife hosts, need to be considered in future studies to explain the differences between collection sites.

Comparison of tick-borne pathogen prevalence in Ixodes ricinus ticks collected in urban areas of Europe

Tick-borne diseases are a major threat to human and animal health. An increasing number of natural habitats have been transformed into urban areas by human activity; hence, the number of reported tick bites in urban and suburban areas has risen. This retrospective analysis evaluated 53 scientific reports concerning infections of Ixodes ricinus ticks collected from urban and suburban areas of Europe between 1991 and 2017. The results indicate significant differences in many variables, including a higher number of Anaplasma phagocytophilum infections in Eastern Europe than in Western Europe. The opposite result was observed for Candidatus Neoehrlichia mikurensis infections. A comparison of climate zones revealed that Borrelia burgdorferi s.l. infections have the greatest median incidence rate in subtropical climate zones. No statistical significance was found when comparing other tick-borne pathogens (TBPs), such as Borrelia miyamotoi, Rickettsia spp., Babesia spp., Bartonella spp., Ehrlichia spp., Coxiella burnetii and Francisella tularensis. The analysis also showed significant differences in the overall prevalence of TBPs according to average temperatures and rainfall across Europe. This retrospective study contributes to the knowledge on the occurrence and prevalence of TBPs in urbanized areas of Europe and their dependence on the habitats and geographical distributions of ticks. Due to the increased risk of tick bites, it is of great importance to investigate infections in ticks from urban and suburban areas.

Transovarial transmission of Borrelia spp., Rickettsia spp. and Anaplasma phagocytophilum in Ixodes ricinus under field conditions extrapolated from DNA detection in questing larvae

Background

Ixodes ricinus constitutes the main European vector tick for the Lyme borreliosis pathogen Borrelia burgdorferi (sensu lato), the relapsing fever borrelia Borrelia miyamotoi, as well as Anaplasma phagocytophilum and several Rickettsia species. Under laboratory conditions, a transovarial transmission to the next tick generation is described for Rickettsia spp. and Borrelia spp., especially regarding B. miyamotoi, whereas the efficiency of transovarial transfer under field conditions is largely unstudied.

Methods

In order to better estimate the potential infection risk by tick larvae for humans and animals, 1500 I. ricinus larvae from 50 collected “nests” (larvae adhering to the flag in a clumped manner) were individually examined for Borrelia, Rickettsia and A. phagocytophilum DNA using quantitative real-time PCR (qPCR).

Results

Thirty-nine of 50 nests each (78.0%, 95% CI: 64.0–88.5%) were positive for Borrelia spp. and Rickettsia spp. DNA, and in three nests (6.0%, 95% CI: 1.3–16.5%) A. phagocytophilum DNA was detected. Overall, DNA from at least one pathogen could be detected in 90.0% (45/50, 95% CI: 78.2–96.7%) of the nests. Of the 1500 larvae, 137 were positive for Borrelia spp. DNA (9.1%, 95% CI: 7.7–10.7%), 341 for Rickettsia spp. DNA (22.7%, 95% CI: 20.6–24.9%) and three for A. phagocytophilum DNA (0.2%, 95% CI: 0–0.6%). Quantity of Borrelia spp. and Anaplasma spp. DNA in positive larvae was low, with 2.7 × 10⁰Borrelia 5S-23S gene copies and 2.4 × 10¹A. phagocytophilum msp2/p44 gene copies detected on average, while Rickettsia-positive samples contained on average 5.4 × 10²gltA gene copies. Coinfections were found in 66.0% (33/50, 95% CI: 51.2–78.8%) of the nests and 8.6% (38/443, 95% CI: 6.1–11.6%) of positive larvae. In fact, larvae had a significantly higher probability of being infected with Borrelia spp. or Rickettsia spp. when both pathogens were present in the nest.

Conclusions

This study provides evidence for transovarial transmission of Rickettsia spp. and Borrelia spp. in I. ricinus under field conditions, possibly facilitating pathogen persistence in the ecosystem and reducing the dependence on the presence of suitable reservoir hosts. Further studies are needed to prove transovarial transmission and to explain the surprisingly high proportion of nests containing Rickettsia and/or Borrelia DNA-positive larvae compared to infection rates in adult ticks commonly reported in other studies.

Borrelia prevalence and species distribution in ticks removed from humans in Germany, 2013-2017

Lyme borreliosis caused by spirochaetes of the Borrelia burgdorferi sensu lato (s.l.) complex is the most common tick-borne disease in Europe. In addition, the relapsing-fever spirochaete Borrelia miyamotoi, which has been associated with febrile illness and meningoencephalitis in immunocompromised persons, is present in Europe. This study investigated Borrelia prevalence and species distribution in ticks removed from humans and sent as diagnostic material to the Institute for Parasitology, University of Veterinary Medicine Hannover, in 2013-2017. A probe-based real-time PCR was carried out and Borrelia-positive samples were subjected to species determination by reverse line blot (RLB), including a B. miyamotoi-specific probe. The overall Borrelia-infection rate as determined by real-time PCR was 20.02 % (510/2547, 95 % CI: 18.48-21.63 %), with annual prevalences ranging from 17.17 % (90/524, 95 % CI: 14.04-20.68 %) in 2014 to 24.12 % (96/398, 95 % CI: 19.99-28.63 %) in 2015. In total, 271/475 (57.1 %) positive samples available for RLB were successfully differentiated. Borrelia afzelii was detected in 30.53 % of cases (145/475, 95 % CI: 26.41-34.89), followed by B. garinii/B. bavariensis (13.26 % [63/475], 95 % CI: 10.34-16.65). Borrelia valaisiana occurred in 5.89 % (28/475, 95 % CI: 3.95-8.41), B. spielmanii in 4.63 % (22/475, 95 % CI: 2.93-6.93), B. burgdorferi sensu stricto (s.s.)/B. carolinensis in 2.32 % (11/475, 95 % CI: 1.16-4.11), B. lusitaniae in 0.63 % (3/475, 95 % CI: 0.13-1.83) and B. bisettiae in 0.42 % (2/475, 95 % CI: 0.05-1.51) of positive ticks. Borrelia kurtenbachii was not detected, while B. miyamotoi was identified in 7.37 % (35/475, 95 % CI: 5.19-10.10) of real-time PCR-positive samples. Sanger sequencing of B. garinii/B. bavariensis-positive ticks revealed that the majority were B. garinii-infections (50/52 successfully amplified samples), while only 2 ticks were infected with B. bavariensis. Furthermore, 6/12 B. burgdorferi s.s./B. carolinensis-positive samples could be differentiated; all of them were identified as B. burgdorferi sensu stricto. Thirty-nine ticks (8.21 %, 95 % CI: 5.90-11.05) were coinfected with two different species. Comparison of the species distribution between ticks removed from humans in 2015 and questing ticks collected in the same year and the same area revealed a significantly higher B. afzelii-prevalence in diagnostic tick samples than in questing ticks, confirming previous observations. The obtained data indicate that Borrelia prevalence fluctuated in the same range as observed in a previous study, analysing the period from 2006 to 2012. Detection of B. miyamotoi in 7.37 % of Borrelia-positive samples points to the fact that clinicians should be aware of this pathogen as a differential diagnosis in cases of febrile illness.

Ixodes inopinatus in northern Germany: occurrence and potential vector role for Borrelia spp., Rickettsia spp., and Anaplasma phagocytophilum in comparison with Ixodes ricinus

In 2014, a new tick species, Ixodes inopinatus, was described, which is closely related to Ixodes ricinus. So far, I. inopinatus has been found in Tunisia, Morocco, Spain, Portugal, Romania, Austria, and southern Germany. No data is yet available regarding occurrence of I. inopinatus in northern Germany and the potential role of I. inopinatus as a vector for tick-borne pathogens. Therefore, 3845 DNA samples from Ixodes ticks collected for prevalence studies on Borrelia spp., Rickettsia spp., and Anaplasma phagocytophilum during the years 2010-2015 in the northern German cities of Hamburg and Hanover were differentiated into I. ricinus or I. inopinatus by sequencing a part of the 16S rRNA gene. In total, 4% (137/3845) of the sequenced ticks were assigned to the species I. inopinatus and 96% (3708/3845) to I. ricinus. The prevalence of Borrelia spp., Rickettsia spp., and A. phagocytophilum DNA in I. inopinatus was 34% (46/137), 46% (63/137), and 3% (4/137), respectively, whereas the prevalence of these bacteria in I. ricinus was 25% (919/3708), 47% (1729/3708), and 4% (135/3708), respectively. Compared with I. ricinus, significantly more I. inopinatus ticks tested positive for Borrelia. To the best of our knowledge, this is the first report of I. inopinatus in northern Germany. Detection of the DNA of Borrelia spp., Rickettsia spp., and A. phagocytophilum in questing I. inopinatus indicates a potential role of this tick species as a vector of these pathogens, which needs to be confirmed by transmission experiments.

Detection of Rickettsia monacensis and Rickettsia amblyommatis in ticks collected from dogs in Costa Rica and Nicaragua

The neotropical climate of Central America provides ideal conditions for ticks, which may transmit several human pathogens, including spotted-fever group Rickettsia. Dogs may act as sentinels or reservoirs for human tick-borne diseases due to shared tick species. Here, ticks were collected from 680 client-owned dogs in Nicaragua and Costa Rica, and a total of 316 tick pools were investigated for Rickettsia infection by quantitative real-time PCR (qPCR) targeting the gltA gene. Subsequently, up to six further genomic targets (16S rDNA, gltA, sca4, ompA, ompB and the 23S-5S intergenic spacer) were investigated for Rickettsia species determination. The predominant tick species was Rhipicephalus sanguineus sensu lato (s.l.) (19.9% of dogs infested in Costa Rica, 48.0% in Nicaragua), followed by Ixodes boliviensis (3.1% in Costa Rica / none in Nicaragua) and Amblyomma ovale (4.8% in Costa Rica, 0.9% in Nicaragua). In total, 22 of 316 tick pools containing 60 of 1023 individual ticks were Rickettsia-positive as determined by qPCR, resulting in a minimum infection rate (MIR) of 2.2%. In detail, MIR in Rh. sanguineus s.l. was 0.7% (7/281 pools), in I. boliviensis 33.3% (12/13 pools) and in A. ovale 9.7% (3/22 pools). For 11 of 12 positive I. boliviensis pools and one of six positive Rh. sanguineus s.l. pools, the species could be determined as R. monacensis. R. amblyommatis was identified in one Rh. sanguineus s.l. pool from Costa Rica and one A. ovale pool from Nicaragua. Nine of 12 R. monacensis-positive tick pools were collected in San Rafael de Heredia, Costa Rica, indicating a high local occurrence in this area. This study supports recent evidence that R. monacensis is present on the American continent. Its high local occurrence among dog-associated I. boliviensis, which may also parasitize humans, in Costa Rica gives cause for concern, as R. monacensis is also pathogenic to humans.

Shifts in Borrelia burgdorferi (s.l.) geno-species infections in Ixodes ricinus over a 10-year surveillance period in the city of Hanover (Germany) and Borrelia miyamotoi-specific Reverse Line Blot detection

BACKGROUND

Lyme borreliosis caused by spirochetes of the Borrelia burgdorferi (sensu lato) complex is still the most common tick-borne disease in Europe, posing a considerable threat to public health. The predominant vector in Europe is the widespread hard tick Ixodes ricinus, which also transmits the relapsing fever spirochete B. miyamotoi as well as pathogenic Rickettsiales (Anaplasma phagocytophilum, Rickettsia spp.). To assess the public health risk, a long-term monitoring of tick infection rates with the named pathogens is indispensable.

METHODS

The present study is the first German 10-year follow-up monitoring of tick infections with Borrelia spp. and co-infections with Rickettsiales. Furthermore, a specific Reverse Line Blot (RLB) protocol for detection of B. miyamotoi and simultaneous differentiation of B. burgdorferi (s.l.) geno-species was established.

RESULTS

Overall, 24.0% (505/2100) of ticks collected in the city of Hanover were infected with Borrelia. In detail, 35.4% (203/573) of adult ticks [38.5% females (111/288) and 32.3% males (92/285)] and 19.8% nymphs (302/1527) were infected, representing consistent infection rates over the 10-year monitoring period. Geno-species differentiation using RLB determined B. miyamotoi in 8.9% (45/505) of positive ticks. Furthermore, a significant decrease in B. afzelii and B. spielmanii infection rates from 2010 to 2015 was observed. Co-infections with Rickettsia spp. and A. phagocytophilum increased between 2010 and 2015 (7.3 vs 10.9% and 0.3 vs 1.1%, respectively).

CONCLUSIONS

Long-term monitoring is an essential part of public health risk assessment to capture data on pathogen occurrence over time. Such data will reveal shifts in pathogen geno-species distribution and help to answer the question whether or not climate change influences tick-borne pathogens.

A 10-year surveillance of Rickettsiales (Rickettsia spp. and Anaplasma phagocytophilum) in the city of Hanover, Germany, reveals Rickettsia spp. as emerging pathogens in ticks

BACKGROUND

Rickettsiales (Rickettsia spp. and Anaplasma phagocytophilum) transmitted by ticks are considered (re-)emerging pathogens posing a risk to public health. Nevertheless, year-long monitoring studies on prevalences of these pathogens in questing ticks to contribute to public health risk assessment are rare.

METHODS

The current study extends previous prevalence surveillances (2005 and 2010) by 2015 to a 10-year monitoring. Therefore, 2100 questing Ixodes ricinus were collected from April to October 2015 at ten different recreation sites in the city of Hanover, Germany, to determine potential changes in tick infection rates with Rickettsiales.

RESULTS

Of the collected ticks, 288 were adult females, 285 adult males and 1527 nymphs. Overall, 3.8% (79/2100) of ticks were infected with A. phagocytophilum, 50.8% (1066/2100) with Rickettsia spp. and 2.2% (46/2100) with both pathogens. Statistical analyses revealed stagnating A. phagocytophilum infection rates over the 10-year monitoring period, whereas Rickettsia infections increased significantly (33.3% in 2005 and 26.2% in 2010 vs 50.8% in 2015). This increase was also characterized by prominent seasonality with higher prevalences from July to October.

CONCLUSIONS

As increased tick infection rates result in an increased risk for public health, the long-term data reported here provide significant implications for the understanding of progressing Rickettsiales distribution in ticks and essentially contribute to reliable public health risk assessments.

Association of Borrelia and Rickettsia spp. and bacterial loads in Ixodes ricinus ticks

In recent years, awareness of coinfections has increased as synergistic or antagonistic effects on interacting bacteria have been observed. To date, several reports on coinfections of ticks with Rickettsia and Borrelia spp. are available. However, associations are rarely described and studies are based on rather low sample sizes. In the present study, coinfections of Ixodes ricinus with these pathogens were investigated by determining their association in a meta-analysis. A total of 5079 tick samples examined for Rickettsia and Borrelia spp. via probe-based quantitative real-time PCR in previous prevalence studies or as submitted diagnostic material were included. In Borrelia-positive ticks, genospecies were determined by Reverse Line Blot. Determination of bacterial loads resulted in an increase between developmental tick stages with highest mean bacterial loads in female ticks (7.96×10⁴ in Borrelia single-infected, 4.87×10⁵ in Rickettsia single-infected and 3.22×10⁵ in Borrelia-Rickettsia coinfected females). The determined Borrelia-Rickettsia tick coinfection rate was 12.3% (626/5079) with a significant difference to the expected coinfection rate of 9.0% (457/5079). A significant slight association as well as correlation between Borrelia and Rickettsia were determined. In addition, a significant interrelation of the bacterial load in coinfected ticks was shown. At the level of Borrelia genospecies, significant weak associations with Rickettsia spp. were detected for B. afzelii, B. garinii/bavariensis, B. valaisiana and B. lusitaniae. The positive association provides evidence for interactions between Borrelia and Rickettsia spp. in the tick vector, presumably resulting in higher bacterial replication rates in the tick vector and possibly the reservoir host. However, coinfection may impact the vector negatively as indicated by an absent increase in coinfection rates from nymphs to adults. Future studies are needed to investigate the underlying mechanisms of the positive association in ticks and possible associations in the vertebrate host as well as the potential influence of environmental factors.

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

BACKGROUND

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

RESULTS

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

CONCLUSIONS

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

Emergence of tick-borne pathogens (Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum, Ricketsia raoultii and Babesia microti) in the Kyiv urban parks, Ukraine

To date, only limited data about the presence of ticks and circulation of tick-borne pathogens in urban parks of Kyiv in northern Ukraine are available. In total, 767 ticks (696 Ixodes ricinus and 69 Dermacentor reticulatus) collected in seven urban parks and one suburban oak wood park in Kyiv were individually analyzed by the PCR assays. Tick-borne pathogens, namely spirochetes from Borrelia burgdorferi sensu lato complex, Anaplasma phagocytophilum, and Babesia microti, were detected in 11.1% of tested I. ricinus ticks. In total, 4% of I. ricinus ticks tested positive for the presence of B. burdorferi s.l. (Borrelia afzelii and Borrelia garinii), 5.2% for A. phagocytophilum, and Ba. microti was confirmed in 1.9% of examined ticks. Mixed infections were recorded in four DNA samples, representing the prevalence of 0.6%. One female and two I. ricinus nymphs were simultaneously infected with B. afzelii and A. phagocytophilum, and one female carried B. afzelii and Ba. microti. In addition, 10.1% of D. reticulatus ticks tested positive for Rickettsia raoultii. Identification of infectious agents and their diversity, assessment of the relative epidemiological importance and determination of the prevalence in questing ticks from central parts of the cities are crucial steps towards the tick-borne diseases surveillance in urban environment.

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

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

Tick survey for prevalent pathogens in peri-urban recreation sites in Saarland and Rhineland-Palatinate (Germany)

Ixodid ticks are important vectors of human pathogens in Central Europe. Despite this fact, prevalence studies are scarce, especially with regard to much-frequented peri-urban recreation sites. In this pilot study, 4.014 larvae, nymphs and adult ticks sampled monthly during the active seasons in 2011 and 2012 from 14 distinct collection sites in two German states (Saarland and Rhineland-Palatinate) were screened for Borrelia spp., Anaplasma spp. and tick-borne encephalitis virus. Mean prevalence rates were 19.8 % for Borrelia spp., 1.9 % for Anaplasma spp. and 0.1 % for tick-borne encephalitis virus (TBEV), which are in accordance with those reported from other regions in Germany and neighbouring countries. Nevertheless, the detection of TBEV-infected ticks is the first positive result after several unsuccessful efforts over the previous years in official "TBE-risk" zones of Saarland and Rhineland-Palatinate which supports the presumption of the origin of observed local infection. Besides ixodid ticks a non-engorged adult female tick of the invading species Dermacentor reticulatus has been found reflecting the appearance of another vector eventually jeopardising the health of host animals as well as humans.

Borrelia burgdorferi sensu lato and co-infections with Anaplasma phagocytophilum and Rickettsia spp. in Ixodes ricinus in Hamburg, Germany

To obtain initial data on Borrelia burgdorferi sensu lato (Spirochaetales: Spirochaetaceae) in Ixodes ricinus (Ixodida: Ixodidae) ticks in Hamburg, Germany, 1400 questing ticks were collected by flagging at 10 different public recreation areas in 2011 and analysed using probe-based quantitative real-time polymerase chain reaction. The overall rate of infection with B. burgdorferi s.l. was 34.1%; 30.0% of adults were infected (36.7% of females and 26.0% of males), as were 34.5% of nymphs. Significant differences in tick infection rates were observed between the spring and summer/autumn months, as well as among sampling locations. Borrelia genospecies identification by reverse line blotting was successful in 43.6% of positive tick samples. The most frequent genospecies was Borrelia garinii/Borrelia bavariensis, followed by Borrelia afzelii, Borrelia valaisiana, B. burgdorferi sensu stricto, Borrelia spielmanii, Borrelia bissettii and Borrelia lusitaniae. Based on previously published data, co-infection of Borrelia and Rickettsiales spp. was determined in 25.8% of ticks. Overall, 22.9% of ticks were co-infected with Rickettsia spp. (Rickettsiales: Rickettsiaceae), 1.7% with Anaplasma phagocytophilum (Rickettsiales: Anaplasmataceae), and 1.2% with both pathogens. Study results show a high prevalence of Borrelia-positive ticks in recreation areas in the northern German city of Hamburg and the potential health risk to humans in these areas should not be underestimated.

Estimating Ixodes ricinus densities on the landscape scale

Background

The study describes the estimation of the spatial distribution of questing nymphal tick densities by investigating Ixodes ricinus in Southwest Germany as an example. The production of high-resolution maps of questing tick densities is an important key to quantify the risk of tick-borne diseases. Previous I. ricinus maps were based on quantitative as well as semi-quantitative categorisations of the tick density observed at study sites with different vegetation types or indices, all compiled on local scales. Here, a quantitative approach on the landscape scale is introduced.

Methods

During 2 years, 2013 and 2014, host-seeking ticks were collected each month at 25 sampling sites by flagging an area of 100 square meters. All tick stages were identified to species level to select nymphal ticks of I. ricinus, which were used to develop and calibrate Poisson regression models. The environmental variables height above sea level, temperature, relative humidity, saturation deficit and land cover classification were used as explanatory variables.

Results

The number of flagged nymphal tick densities range from zero (mountain site) to more than 1,000 nymphs/100 m². Calibrating the Poisson regression models with these nymphal densities results in an explained variance of 72 % and a prediction error of 110 nymphs/100 m² in 2013. Generally, nymphal densities (maximum 374 nymphs/100 m²), explained variance (46 %) and prediction error (61 nymphs/100 m²) were lower in 2014. The models were used to compile high-resolution maps with 0.5 km² grid size for the study region of the German federal state Baden-Württemberg. The accuracy of the mapped tick densities was investigated by leave-one-out cross-validation resulting in root-mean-square-errors of 227 nymphs/100 m² for 2013 and 104 nymphs/100 m² for 2014.

Conclusions

The methodology introduced here may be applied to further tick species or extended to other study regions. Finally, the study is a first step towards the spatial estimation of tick-borne diseases in Central Europe.

Electronic supplementary material

The online version of this article (doi:10.1186/s12942-015-0015-7) contains supplementary material, which is available to authorized users.

Anaplasma phagocytophilum prevalence in ticks and rodents in an urban and natural habitat in South-Western Slovakia

Background

Ixodes ricinus is the principal vector of Anaplasma phagocytophilum, the ethiological agent of granulocytic anaplasmosis in Europe. Anaplasmosis is an emerging zoonotic disease with a natural enzootic cycle. The reservoir competence of rodents is unclear. Monitoring of A. phagocytophilum prevalence in I. ricinus and rodents in various habitat types of Slovakia may contribute to the knowledge about the epidemiology of anaplasmosis in Central Europe.

Methods

Over 4400 questing ixodid ticks, 1000 rodent-attached ticks and tissue samples of 606 rodents were screened for A. phagocytophilum DNA by real-time PCR targeting the msp2 gene. Ticks and rodents were captured along six transects in an urban/suburban and natural habitat in south-western Slovakia during 2011–2014. Estimates of wildlife (roe deer, red deer, fallow deer, mouflon, wild boar) densities in the study area were taken from hunter’s yearly reports. Spatial and temporal differences in A. phagocytophilum prevalence in questing I. ricinus and relationships with relative abundance of ticks and wildlife were analysed.

Results

Overall prevalence of A. phagocytophilum in questing I. ricinus was significantly higher in the urban/suburban habitat (7.2 %; 95 % CI: 6.1–8.3 %) compared to the natural habitat (3.1 %; 95 % CI: 2.5–3.9 %) (χ² = 37.451; P < 0.001). Significant local differences in prevalence of infected questing ticks were found among transects within each habitat as well as among years and between seasons. The trapped rodents belonged to six species. Apodemus flavicollis and Myodes glareolus prevailed in both habitats, Microtus arvalis was present only in the natural habitat. I. ricinus comprised 96.3 % of the rodent-attached ticks, the rest were Haemaphysalis concinna, Ixodes trianguliceps and Dermacentor reticulatus. Only 0.5 % of rodent skin and 0.6 % of rodent-attached ticks (only I. ricinus) were infected with A. phagocytophilum. Prevalence of A. phagocytophilum in questing I. ricinus did not correlate significantly with relative abundance of ticks or with abundance of wildlife in the area.

Conclusion

The study confirms that urban I. ricinus populations are infected with A. phagocytophilum at a higher rate than in a natural habitat of south-western Slovakia and suggests that rodents are not the main reservoirs of the bacterium in the investigated area.

High Prevalence of Anaplasma spp. in Small Ruminants in Morocco

The prevalence of infection by Anaplasma spp. (including Anaplasma phagocytophilum) was determined using blood smear microscopy and PCR through screening of small ruminant blood samples collected from seven regions of Morocco. Co-infections of Anaplasma spp., Babesia spp, Theileria spp. and Mycoplasma spp. were investigated and risk factors for Anaplasma spp. infection assessed. A total of 422 small ruminant blood samples were randomly collected from 70 flocks. Individual animal (breed, age, tick burden and previous treatment) and flock data (GPS coordinate of farm, size of flock and livestock production system) were collected. Upon examination of blood smears, 375 blood samples (88.9%) were found to contain Anaplasma-like erythrocytic inclusion bodies. Upon screening with a large spectrum PCR targeting the Anaplasma 16S rRNA region, 303 (71%) samples were found to be positive. All 303 samples screened with the A. phagocytophilum-specific PCR, which targets the msp2 region, were found to be negative. Differences in prevalence were found to be statistically significant with regard to region, altitude, flock size, livestock production system, grazing system, presence of clinical cases and application of tick and tick-borne diseases prophylactic measures. Kappa analysis revealed a poor concordance between microscopy and PCR (k = 0.14). Agreement with PCR is improved by considering microscopy and packed cell volume (PCV) in parallel. The prevalence of double infections was found to be 1.7, 2.5 and 24% for Anaplasma-Babesia, Anaplasma-Mycoplasma and Anaplasma-Theileria, respectively. Co-infection with three or more haemoparasites was found in 1.6% of animals examined. In conclusion, we demonstrate the high burden of anaplasmosis in small ruminants in Morocco and the high prevalence of co-infections of tick-borne diseases. There is an urgent need to improve the control of this neglected group of diseases.

Serological differentiation of antibodies against Rickettsia helvetica, R. raoultii, R. slovaca, R. monacensis and R. felis in dogs from Germany by a micro-immunofluorescent antibody test

Background

Spotted Fever Group (SFG) Rickettsiae can cause febrile diseases with or without rash in humans worldwide. In Germany only limited data are available about their medical significance. Serological screening tests for antibodies against rickettsiae usually only distinguish between SFG and Typhus Group (TG) Rickettsiae due to the strong cross reactivities within the groups. Seroprevalence rates in dogs, as possible sentinels for tick-borne diseases, could serve as an indicator for the distribution of different Rickettsia species.

Methods

In this study, a micro-immunofluorescence assay (micro-IFA) was established for detection and differentiation of antibodies against five Rickettsia species in dogs (R. helvetica, R. raoultii, R. slovaca, R. monacensis and R. felis). Dogs that never left Germany (n = 605) previously investigated with an SFG-ELISA were included in this study and screened at a 1:128 dilution. Endpoint titres of fifty randomly selected seropositive samples of each of the five investigated regions in Germany were determined in order to allow a differentiation of the causative Rickettsia species. Sensitivity and specificity of the micro-IFA were compared with ELISA results of the previous study.

Results

A total of 93.9% of the dogs were positive for antibodies of the SFG Rickettsiae at the screening titer of 1:128. Differentiation of SFG Rickettsiae with the micro-IFA was possible in 70.4%, but in 29.6% of the cases the detected antibodies were not differentiable. Considering a clear differentiation by a twofold titre difference between observed reactions, the seroprevalence rates were 66.0% for R. helvetica, 2.8% for R. raoultii, 1.6% for R. slovaca, but no serological reaction could be clearly attributed to R. monacensis or R. felis. No statistically significant regional differences were found for R. helvetica, R. slovaca and R. raoultii comparing the five regions of Germany. Comparison of micro-IFA with ELISA revealed a sensitivity of 82.0% and a specificity of 83.8% for the Rickettsia SFG ELISA.

Conclusions

The micro-IFA is a useful serological tool to differentiate antibodies against different Rickettsia species in dogs. Seroprevalence rates in dogs correspond to the prevalence rates and distribution of Rickettsia-carrying tick species.

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

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

The first German map of georeferenced ixodid tick locations

BACKGROUND

Georeferenced locations of ixodid ticks are required to depict the observed distribution of species. Further, they are used as input data for species distribution models also known as niche models. The latter were applied to describe current and future (projected) tick distributions. Beside model assumptions and selected climate parameters, the number of georeferenced tick locations available as a digital dataset is of fundamental importance for the reliability of such models. For Germany, however, no comprehensive dataset of ixodid tick species exists. The goal of this study was to put together all the available information on ixodid tick locations in Germany to produce such a digital dataset and to visualize it in a map.

FINDINGS

A total of 2,044 georeferenced locations of ixodid ticks in Germany were compiled from two existing datasets (altogether 993 locations) and an extensive literature study (1,051 locations). The resulting digital dataset comprises the following tick species: Ixodes ricinus (1,855 locations), Ixodes apronophorus (1), Ixodes frontalis (1), Ixodes hexagonus (1), Ixodes trianguliceps (4), Dermacentor marginatus (77), Dermacentor reticulatus (96), Haemaphysalis concinna (8) and Hyalomma marginatum (1). The data were used to draw a tick map for Germany, showing I. ricinus occurring in the whole federal territory, while D. marginatus has been restricted to the climatically favoured region of the Rhine valley. Clustered locations of D. reticulatus were also documented in the Rhine valley as well as in Berlin and its vicinity.

CONCLUSIONS

The introduced map depicts for the first time the available geographical coordinates of ixodid tick locations in Germany. The digital dataset used to draw the map is provided to the scientific community as a basis for further investigations such as species distribution modelling.

Revisited: Borrelia burgdorferi sensu lato infections in hard ticks (Ixodes ricinus) in the city of Hanover (Germany)

Background

The present study investigated the prevalence of Borrelia burgdorferi sensu lato (s.l.) genospecies in Ixodes ricinus ticks collected in Hanover, Northern Germany, in 2010. At the same time the study served as fifth-year-follow-up study for data comparison with 2005.

Methods

A total of 2100 questing ticks were collected and analysed by quantitative real-time PCR (qPCR) with subsequent species differentiation via Reverse Line Blot and Sanger sequencing. Simultaneously, results obtained in 2010 were compared to infection rates from 2005 to evaluate the development of B. burgdorferi s.l. infection rates in Hanoverian ticks.

Results

Overall, 22.7% (476/2,100) of collected ticks were tested positive for B. burgdorferi s.l. infections. Adult ticks showed an infection rate of 33.3% (124/372), subdivided into 29.6% (58/196) positive males and 37.5% (66/176) positive females. Nymph and larvae infection rates were found to be 20.3% (344/1,697) and 25.8% (8/31), respectively. Species identification was successful for 59.2% (282/476) of positive ticks with B. afzelii as the most frequently detected genospecies, followed by B. garinii (including B. bavariensis) and B. spielmanii. B. burgdorferi sensu stricto (s.s.), B. bissettii, B. valaisiana and B. lusitaniae were also identified. Significant differences concerning seasonal fluctuations as well as local differences were observed. Comparing infection rates of Hanoverian ticks between years, a significant increase (P = 0.002) could be observed for larvae with 1.7% positives (2/60) in 2005 and 25.8% positives (8/31) in 2010. In the latter year, coinfections with Borrelia and Rickettsiales were detected in a total of 7.8% (163/2,100) of collected ticks. Of these, 7.3% (153/2,100) were coinfected with Rickettsia spp., 0.3% (7/2,100) with A. phagocytophilum and 0.1% (3/2,100) were coinfected with all three pathogens. Between years 2005 and 2010, no statistically significant differences in coinfection rates were found.

Conclusions

Comparing B. burgdorferi s.l. infections in Hanoverian I. ricinus ticks in 2010 with data from 2005, a statistically significant increase of infected larvae was noted, whereas the other stages revealed no statistically significant differences. Whether the increased larvae infection rate is an isolated event or results from factual circumstances, e.g. increasing effectiveness of transovarial transmission due to unknown factors, has to be evaluated in further studies.

Prevalence of Rickettsiales (Anaplasma phagocytophilum and Rickettsia spp.) in hard ticks (Ixodes ricinus) in the city of Hamburg, Germany

To narrow the gap of missing knowledge on Rickettsia spp. and Anaplasma phagocytophilum infections in ticks in northwestern Germany and, at the same time, to provide first prevalence data on these pathogens in the city of Hamburg, a total of 1,400 questing Ixodes ricinus ticks were collected at ten different public green areas from April until October 2011. Ticks were examined using probe-based quantitative real-time PCR. A percentage of 3.6% (51/1,400) ticks were tested positive for A. phagocytophilum infections divided into 2.1% (3/141) adults [1.7% (1/60) females and 2.5% (2/81) males] and 3.8% (48/1,259) nymphs. The percentage of infected ticks per sampling site varied statistically significantly from 0.7% (1/140) to 12.1% (17/140), whereas between sampling months, no statistically significant differences were observed (2.0-6.5%, 4-13/140). The overall Rickettsia spp. infection rate was 52.5% (735/1,400). In adult ticks, Rickettsia spp. infection rate was 56% (79/141) divided into 61.7% (37/60) infected females and 51.9% (42/81) infected males. Nymphs showed an infection rate of 52.1% (656/1,259). In contrast to A. phagocytophilum infections, no statistically significant differences in Rickettsia spp. infection rates among sampling sites (44.3-63.6%, 62-89/140) were observed, whereas seasonal variations were obvious: the percentage of Rickettsia-positive ticks was significantly lower in April (36.5%, 73/200) and May (29.5%, 59/200) compared to the summer and fall months (55.0-64.5%, 110-129/200). Rickettsia species differentiation via real-time pyrosequencing revealed Rickettsia helvetica as the only occurring species. Co-infections with both Rickettsia spp. and A. phagocytophilum were detected in 2.0% (28/1,400) of the ticks. The present study revealed that in the city of Hamburg, the tick infection rate with A. phagocytophilum is comparable with other German data, whereas the Rickettsia spp. infection rate of 52.5% is by far the highest prevalence detected in Germany so far. As the city of Hamburg has 1.8 million inhabitants and attracts millions of tourists every year, the potential health risk should not be underestimated.

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

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