Detection and identification of Borrelia burgdorferi sensu lato genospecies in ticks from three different regions in Slovakia

Spatial and Temporal Variability in Prevalence Rates of Members of the Borrelia burgdorferi Species Complex in Ixodes ricinus Ticks in Urban, Agricultural and Sylvatic Habitats in Slovakia

Lyme borreliosis (LB) is the most prevalent tick-borne human infection in Europe, with increasing incidence during the latest decades. Abundant populations of Ixodes ricinus, the main vector of the causative agent, spirochetes from the Borrelia burgdorferi sensu lato (Bbsl) complex, have been observed in urban and suburban areas of Europe, in general, and Slovakia, particularly. Understanding the spread of infectious diseases is crucial for implementing effective control measures. Global changes affect contact rates of humans and animals with Borrelia-infected ticks and increase the risk of contracting LB. The aim of this study was to investigate spatial and temporal variation in prevalence of Bbsl and diversity of its species in questing I. ricinus from three sites representing urban/suburban, natural and agricultural habitat types in Slovakia. Ixodes ricinus nymphs and adults were collected by dragging the vegetation in green areas of Bratislava town (urban/suburban habitat), in the Small Carpathians Mountains (natural habitat) (south-western Slovakia) and in an agricultural habitat at Rozhanovce in eastern Slovakia. Borrelia presence in ticks was detected by PCR and Bbsl species were identified by restriction fragment length polymorphism (RFLP). Borrelia burgdorferi s.l. species in coinfected ticks were identified by reverse line blot. Significant spatial and temporal variability in prevalence of infected ticks was revealed in the explored habitats. The lowest total prevalence was detected in the urban/suburban habitat, whereas higher prevalence was found in the natural and agricultural habitat. Six Bbsl species were detected by RFLP in each habitat type -B. burgdorferi sensu stricto (s.s.), B. afzelii, B. garinii, B. valaisiana, B. lusitaniae and B. spielmanii. Coinfections accounted for 3% of the total infections, whereby B. kurtenbachii was identified by RLB and sequencing in mixed infection with B. burgdorferi s.s, B. garinii and B. valaisiana. This finding represents the first record of B. kurtenbachii in questing I. ricinus in Slovakia and Europe. Variations in the proportion of Bbsl species were found between nymphs and adults, between years and between habitat types. Spatial variations in prevalence patterns and proportion of Bbsl species were also confirmed between locations within a relatively short distance in the urban habitat. Habitat-related and spatial variations in Borrelia prevalence and distribution of Bbsl species are probably associated with the local environmental conditions and vertebrate host spectrum. Due to the presence of Borrelia species pathogenic to humans, all explored sites can be ranked as areas with high epidemiological risk.

Ticks and their epidemiological role in Slovakia: from the past till present

In Slovakia, 22 tick species have been found to occur to date. Among them, Ixodes ricinus, Dermacentor reticulatus, D. marginatus and marginally Haemaphysalis concinna, H. inermis and H. punctata have been identified as the species of public health relevance. Ticks in Slovakia were found to harbour and transmit zoonotic and/or potentially zoonotic agents such as tick-borne encephalitis virus (TBEV), spirochaetes of the Borrelia burgdorferi sensu lato (s.l.) complex, the relapsing fever sprirochaete Borrelia miyamotoi, bacteria belonging to the orders Rickettsiales (Rickettsia spp., Anaplasma phagocytophilum, Neoehrlichia mikurensis), Legionellales (Coxiella burnetii), and Thiotrichales (Francisella tularensis), and Babesia spp. parasites (order Piroplasmida). Ixodes ricinus is the principal vector of the largest variety of microorganisms including viruses, bacteria and piroplasms. TBEV, B. burgdorferi s.l., rickettsiae of the spotted fever group, C. burnetii and F. tularensis have been found to cause serious diseases in humans, whereas B. miyamotoi, A. phagocytophilum, N. mikurensis, Babesia microti, and B. venatorum pose lower or potential risk to humans. Distribution of TBEV has a focal character. During the last few decades, new tick-borne encephalitis (TBE) foci and their spread to new areas have been registered and TBE incidence rates have increased. Moreover, Slovakia reports the highest rates of alimentary TBE infections among the European countries. Lyme borreliosis (LB) spirochaetes are spread throughout the distribution range of I. ricinus. Incidence rates of LB have shown a slightly increasing trend since 2010. Only a few sporadic cases of human rickettsiosis, anaplasmosis and babesiosis have been confirmed thus far in Slovakia. The latest large outbreaks of Q fever and tularaemia were recorded in 1993 and 1967, respectively. Since then, a few human cases of Q fever have been reported almost each year. Changes in the epidemiological characteristics and clinical forms of tularaemia have been observed during the last few decades. Global changes and development of modern molecular tools led to the discovery and identification of emerging or new tick-borne microorganisms and symbionts with unknown zoonotic potential. In this review, we provide a historical overview of research on ticks and tick-borne pathogens in Slovakia with the most important milestones and recent findings, and outline future directions in the investigation of ticks as ectoparasites and vectors of zoonotic agents and in the study of tick-borne diseases.

Approaches for Reverse Line Blot-Based Detection of Microbial Pathogens in Ixodes ricinus Ticks Collected in Austria and Impact of the Chosen Method

Ticks transmit a large number of pathogens capable of causing human disease. In this study, the PCR-reverse line blot (RLB) method was used to screen for pathogens in a total of 554 Ixodes ricinus ticks collected from all provinces of Austria. These pathogens belong to the genera Borrelia, Rickettsiae, Anaplasma/Ehrlichia (including "Candidatus Neoehrlichia"), Babesia, and Coxiella The pathogens with the highest detected prevalence were spirochetes of the Borrelia burgdorferisensu lato complex, in 142 ticks (25.6%). Borrelia afzelii (80/142) was the most frequently detected species, followed by Borrelia burgdorferisensu stricto (38/142) and Borrelia valaisiana (36/142). Borrelia garinii/Borrelia bavariensis, Borrelia lusitaniae, and Borrelia spielmanii were found in 28 ticks, 5 ticks, and 1 tick, respectively. Rickettsia spp. were detected in 93 ticks (16.8%): R. helvetica (39/93), R. raoultii (38/93), R. monacensis (2/93), and R. slovaca (1/93). Thirteen Rickettsia samples remain uncharacterized. "Candidatus Neoehrlichia mikurensis," Babesia spp. (B. venatorum, B. divergens, B. microti), and Anaplasma phagocytophilum were found in 4.5%, 2.7%, and 0.7%, respectively. Coxiella burnetii was not detected. Multiple microorganisms were detected in 40 ticks (7.2%), and the cooccurrence of Babesia spp. and "Candidatus Neoehrlichia mikurensis" showed a significant positive correlation. We also compared different PCR-RLBs for detection of Borrelia burgdorferisensu lato and Rickettsia spp. and showed that different detection approaches provide highly diverse results, indicating that analysis of environmental samples remains challenging.IMPORTANCE This study determined the wide spectrum of tick-borne bacterial and protozoal pathogens that can be encountered in Austria. Surveillance of (putative) pathogenic microorganisms occurring in the environment is of medical importance, especially when those agents can be transmitted by ticks and cause disease. The observation of significant coinfections of certain microorganisms in field-collected ticks is an initial step to an improved understanding of microbial interactions in ticks. In addition, we show that variations in molecular detection methods, such as in primer pairs and target genes, can considerably influence the final results. For instance, detection of certain genospecies of borreliae may be better or worse by one method or the other, a fact of great importance for future screening studies.

Borrelia miyamotoi and Co-Infection with Borrelia afzelii in Ixodes ricinus Ticks and Rodents from Slovakia

Borrelia miyamotoi causes relapsing fever in humans. The occurrence of this spirochete has been reported in Ixodes ricinus and wildlife, but there are still gaps in the knowledge of its eco-epidemiology and public health impact. In the current study, questing I. ricinus (nymphs and adults) and skin biopsies from rodents captured in Slovakia were screened for the presence of B. miyamotoi and Borrelia burgdorferi s.l. DNA. The prevalence of B. miyamotoi and B. burgdorferi s.l. in questing ticks was 1.7 and 16.9%, respectively. B. miyamotoi was detected in Apodemus flavicollis (9.3%) and Myodes glareolus (4.4%). In contrast, B. burgdorferi s.l. was identified in 11.9% of rodents, with the highest prevalence in Microtus arvalis (68.4%) and a lower prevalence in Apodemus spp. (8.4%) and M. glareolus (12.4%). Borrelia afzelii was the prevailing genospecies infecting questing I. ricinus (37.9%) and rodents (72.2%). Co-infections of B. miyamotoi and B. burgdorferi s.l. were found in 24.1 and 9.3% of the questing ticks and rodents, respectively, whereas the proportion of ticks and rodents co-infected with B. miyamotoi and B. afzelii was 6.9 and 7.0%, respectively. The results suggest that B. miyamotoi and B. afzelii share amplifying hosts. The sequences of the B. miyamotoi glpQ gene fragment from our study showed a high degree of identity with sequences of the gene amplified from ticks and human patients in Europe. The results seem to suggest that humans in Slovakia are at risk of contracting tick-borne relapsing fever, and in some cases together with Lyme borreliosis.

DNA-based identification and OspC serotyping in cultures of Borrelia burgdorferi s.l. isolated from ticks collected in the Moravia (Czech Republic)

Two different genetic loci, flaB and ospC, were employed to assign genospecies and OspC phylogenetic type to 18 strains isolated from ticks collected in Pisárky, a suburban park in the city of Brno, Czech Republic. The RFLP analysis revealed three different genospecies (B. afzelii, B. garinii, and B. valaisiana). Three samples from the collection contained more than one genospecies. In the other 15 strains, nucleotide sequences of flaB and ospC were determined. The following phylogenetic analysis assigned 12 isolates to genospecies B. garinii and three to B. afzelii. These isolates were further subdivided into seven distinct ospC groups. The most related OspC types were G2, G4, and G5 (B. garinii) and A3 and A8 (B. afzelii).

Coexistence of Borrelia burgdorferi s.l. genospecies within Ixodes ricinus ticks from central and eastern Poland

The purpose of the study was to assess the prevalence and coinfection rates of Borrelia burgdorferi sensu lato genotypes in Ixodes ricinus (L.) ticks sampled from diverse localities in central and eastern regions of Poland. In years 2009-2011, questing nymphs and adults of I. ricinus were collected using a flagging method at 18 localities representing distinct ecosystem types: urban green areas, suburban forests and rural woodlands. Molecular detection of B. burgdorferi s.l. genospecies was based on amplification of a fla gene using nested PCR technique, subsequent PCR-RFLP analysis and bidirectional sequencing. It was revealed that 45 samples (2.1%) harboured two different B. burgdorferi s.l. genospecies, whereas triple infections with various spirochetes was found in 11 (0.5%) individuals. Generally, the highest average coinfection rates were evidenced in arachnids gathered at rural woodlands, intermediate at suburban forests, while the lowest were recorded at urban green areas. Overall, single spirochete infections were noted in 16.3% (n = 352/2,153) ticks. Importantly, it is the first report evidencing the occurrence of Borrelia miyamotoi (0.3%, n = 7/2153) in I. ricinus populations within central Poland. Circumstantial variability of B. burgdorferi s.l. genospecies in the common tick individuals sampled at various habitat types in central and eastern Poland was displayed. The coexistence of two or three different spirochete genospecies in single adult ticks, as well as the presence of B. miyamotoi were demonstrated. Therefore, further studies uncovering the co-circulation of the tested bacteria and other human pathogens in I. ricinus ticks are required.

Multiple tick-associated bacteria in Ixodes ricinus from Slovakia

Eighty Ixodes ricinus ticks collected in the Rovinka forest in Slovakia were tested by real-time and routine single-step PCR for the presence of different pathogenic and endosymbiotic bacteria. No evidence of Coxiella burnetii, Diplorickettsia massiliensis, or Bartonella spp. was found. However, we identified, as the pathogenic bacteria, Anaplasma phagocytophilum in 8%, Rickettsia helvetica in 11%, Borrelia afzelii in 9%, Bo. garinii in 8%, Bo. burgdorferi sensu stricto in 5%, Bo. valaisiana in 3%, and Bo. miyamotoi in 1% of ticks. Other bacteria with unknown or suspected pathogenicity for humans were also identified: Arsenophonus nasoniae in 25%, Spiroplasma ixodetis in 3%, Candidatus Midichloria mitochondrii in 4%, Wolbachia aff. pipientis in 14%, and Ehrlichia muris in 3% of ticks. A. nasoniae was found almost exclusively in nymphs, and E. muris was only found in adult ticks. In total, 65% of ticks contained at least one species of bacteria, and 16% contained 2 or more species.

Are birds reservoir hosts for Borrelia afzelii?

It is known that birds are competent reservoir hosts of particular Borrelia species like B. garinii and B. valaisiana but not for B. afzelii, a rodent-associated genospecies. Since they can carry infected ticks over long distances, they are also important covectors for Lyme borreliosis spirochaetes. To assess the role of different bird species in transmission and dispersal of Borrelia OspA types, we examined 191 Ixodes ricinus ticks from 99 birds, captured on a German conservation island in the Baltic Sea in spring 2007. Surprisingly, more than one third of the 27 positive samples were identified as B. afzelii. The cause for this unusually high prevalence remains unknown, indicating the need of further studies on bird-feeding ticks that should include a higher sample size.

Spatial distribution of Dermacentor reticulatus tick in Slovakia in the beginning of the 21st century

A new field survey monitoring the spatial distribution of Dermacentor (D.) reticulatus (Fabricius, 1794) tick in Slovakia was carried out in 2005-2008 in order to record changes in its distribution when compared to former studies. Last surveys on the geographical distribution were conducted in 1950s and 1970s and the presence of D. reticulatus was determined along the rivers in the south-east (Latorica) as well as in the south-west (Morava, Dunaj) Slovakia. In the present survey new areas with D. reticulatus occurrence were detected, providing evidence that this tick species has extended its range in the surroundings of its former habitats but also by at least 200 km further North and by 300 m of elevation into higher altitudes. D. reticulatus is known to transmit Babesia spp. causing babesiosis in cattle and dogs. Expansion of D. reticulatus range is therefore likely to bring a spread of babesiosis, which can be severe or fatal especially for dogs.

Serological and molecular detection of Borrelia burgdorferi sensu lato and Anaplasmataceae in rodents

The presence of Anaplasma spp. and Borrelia burgdorferi sensu lato in rodents from Eastern Slovakia were followed by serological and molecular methods. The seroprevalence for Borrelia was detected in 16.6 %, for Anaplasmataceae (APT) in 13.2 % and co-occurrence of Borrelia and APT in 7.5 %. Out of 110 ear biopsies of rodents, 5 were B. afzelii-positive. Five biopsies tested positive with the Ehr521-Ehr747 primers amplifying all the members of the family APT. A. phagocytophilum was detected in 1.8 %, 2.7 % were infected with Anaplasma-like organisms. Co-occurrence of Borrelia and Anaplasma in ear biopsies was found in 1.8 %. The circulation of both Borrelia and Anaplasma in the region of Eastern Slovakia was confirmed.