Markéta Derdáková

Driving forces for changes in geographical distribution of Ixodes ricinus ticks in Europe

Many factors are involved in determining the latitudinal and altitudinal spread of the important tick vector Ixodes ricinus (Acari: Ixodidae) in Europe, as well as in changes in the distribution within its prior endemic zones. This paper builds on published literature and unpublished expert opinion from the VBORNET network with the aim of reviewing the evidence for these changes in Europe and discusses the many climatic, ecological, landscape and anthropogenic drivers. These can be divided into those directly related to climatic change, contributing to an expansion in the tick’s geographic range at extremes of altitude in central Europe, and at extremes of latitude in Scandinavia; those related to changes in the distribution of tick hosts, particularly roe deer and other cervids; other ecological changes such as habitat connectivity and changes in land management; and finally, anthropogenically induced changes. These factors are strongly interlinked and often not well quantified. Although a change in climate plays an important role in certain geographic regions, for much of Europe it is non-climatic factors that are becoming increasingly important. How we manage habitats on a landscape scale, and the changes in the distribution and abundance of tick hosts are important considerations during our assessment and management of the public health risks associated with ticks and tick-borne disease issues in 21st century Europe. Better understanding and mapping of the spread of I. ricinus (and changes in its abundance) is, however, essential to assess the risk of the spread of infections transmitted by this vector species. Enhanced tick surveillance with harmonized approaches for comparison of data enabling the follow-up of trends at EU level will improve the messages on risk related to tick-borne diseases to policy makers, other stake holders and to the general public.

Blackbirds and song thrushes constitute a key reservoir of Borrelia garinii, the causative agent of borreliosis in Central Europe.

ABSTRACT Blackbirds (Turdus merula) and song thrushes (Turdus philomelos) were found to carry 95% of all spirochete-infected tick larvae among 40 bird species captured in Central Europe. More than 90% of the infections were typed as Borrelia garinii and Borrelia valaisiana. We conclude that thrushes are key players in the maintenance of these spirochete species in this region of Central Europe.

Genetic Variability within Borrelia burgdorferi Sensu Lato Genospecies Established by PCR-Single-Strand Conformation Polymorphism Analysis of the rrfA-rrlB Intergenic Spacer in Ixodes ricinus Ticks from the Czech Republic

ABSTRACT In Europe the Borrelia burgdorferi sensu lato complex is represented by five distinct genospecies: Borrelia burgdorferi sensu stricto, Borrelia afzelii, Borrelia garinii, Borrelia valaisiana, and Borrelia lusitaniae. These taxonomic entities are known to differ in their specific associations with vertebrate hosts and to provoke distinct clinical manifestations in human patients. However, exceptions to these rules have often been observed, indicating that strains belonging to a single genospecies may be more heterogeneous than expected. It is, therefore, important to develop alternative identification tools which are able to distinguish Borrelia strains not only at the specific level but also at the intraspecific level. DNA from a sample of 370 Ixodes ricinus ticks collected in the Czech Republic was analyzed by PCR for the presence of a ∼230-bp fragment of the rrfA-rrlB intergenic spacer of Borrelia spp. A total of 20.5% of the ticks were found to be positive. The infecting genospecies were identified by analyzing the amplified products by the restriction fragment length polymorphism (RFLP) method with restriction enzyme MseI and by single-strand conformation polymorphism (SSCP) analysis. The two methods were compared, and PCR-SSCP analysis appeared to be a valuable tool for rapid identification of spirochetes at the intraspecific level, particularly when large samples are examined. Furthermore, by using PCR-SSCP analysis we identified a previously unknown Borrelia genotype, genotype I-77, which would have gone unnoticed if RFLP analysis alone had been used.

Borrelia lusitaniae and green lizards (Lacerta viridis), Karst Region, Slovakia.

TOC summary line: The green lizard is implicated in the transmission cycle of B. lusitaniae.

Ixodes ricinus abundance and its infection with the tick-borne pathogens in urban and suburban areas of Eastern Slovakia.

BackgroundRaising 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.MethodsQuesting 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.ResultsIn 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.ConclusionsOur 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.

Candidatus Neoehrlichia mikurensis and its co-circulation with Anaplasma phagocytophilum in Ixodes ricinus ticks across ecologically different habitats of Central Europe

BackgroundCandidatus 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.FindingsCandidatus 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.ConclusionA 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.

First report of Anaplasma phagocytophilum and its co-infections with Borrelia burgdorferi sensu lato in Ixodes ricinus ticks (Acari: Ixodidae) from Republic of Moldova

We examined 198 questing Ixodes ricinus ticks collected in Chisinau City, Republic of Moldova by PCR assays for Anaplasma phagocytophilum, Borrelia burgdorferi sensu lato and co-infection of both pathogens, which were detected in 9%, 25.2% and 2.5% of tested ticks, respectively. B. burgdorferi s.l. genotyping revealed the presence of five genospecies with dominance of B. garinii. Our preliminary study provides evidence about occurrence of both pathogens in this populated area, which represent a potential health risk for inhabitants.

Genetic and Ecologic Variability among Anaplasma phagocytophilum Strains, Northern Italy

To the Editor: The tick-borne pathogen Anaplasma phagocytophilum is an increasing potential public health threat across Europe. Its intraspecific genetic variability is associated with different reservoir host and vector tick species (1–4); however, the roles of various vertebrates as competent reservoirs of A. phagocytophilum in Europe need clarification (1). During March 2011–June 2013, we studied the prevalence and genetic variability of A. phagocytophilum in 821 questing Ixodes ricinus ticks (155 adults [A], 666 nymphs [N] collected by standard blanket dragging) and 284 engorged ixodid ticks (61A, 191N, 21 larvae [L]) collected from humans, dogs, sheep, hunted wild ungulates, live-trapped birds, and rodents. Blood samples from 1,295 rodents (yellow-necked mice [Apodemus flavicollis]), bank voles [Myodes glareolus], and harvest mice [Moscardinus avellanarius]) were also analyzed. All animal-handling procedures and ethical issues were approved by the Provincial Wildlife Management Committee (authorization n. 595 issued on 04.05.2011). The study site, Valle dei Laghi (northeastern Italian Alps), is a well-studied focus of emerging tick-borne pathogens in northern Italy (4).

Emergence and genetic variability of Anaplasma species in small ruminants and ticks from Central Europe.

Anaplasmoses are common tick-borne zoonotic bacterial diseases of livestock and free-living ungulates from the genus Anaplasma that are recently emerging in Central Europe. The main aim of this study was to analyze the prevalence and genetic variability of Anaplasma phagocytophilum and Anaplasma ovis in small ruminants and questing ticks from six different sites in Slovakia and the Czech Republic using the PCR of the msp4 gene followed by the sequence analysis. At two farms from southeastern Slovakia, 66.1% small ruminants were infected with A. ovis in contrast to one positive animal from both sites in northern Slovakia. It was represented by two different genotypes. A. phagocytophilum was present in all tested flocks with the infection prevalence ranging from 0.9% to 5.7%. None of the tested questing ticks carried A. ovis. A. phagocytophilum was detected in 1.1% and 7.8% of questing Ixodes ricinus ticks collected around the farms located in southeastern and northern Slovakia, respectively. A. phagocytophilum revealed higher intraspecific diversity than A. ovis.

Rickettsial infection in Ixodes ricinus ticks in urban and natural habitats of Slovakia.

A total of 1810 Ixodes ricinus ticks was collected from the vegetation from 2 different habitat types: urban and natural. Urban habitats were represented by cemeteries and public parks in the following towns: Bratislava, Malacky, and Martin at 150 m and 400 m above sea level. Natural habitats were selected in the mountain forest of the Martinské hole Mts. in Central Slovakia at 3 different altitudinal levels, i.e. 600 m, 800 m and 1000 ma.s.l. All ticks were tested for the presence of spotted fever group rickettsiae. The DNA of Rickettsia spp. was identified in 9% of all tested ticks. Rickettsia-infected ticks were present in both, urban and sylvatic sites at all studied altitudes. Four different species of Rickettsia were present in positive I. ricinus ticks. Rickettsia helvetica was identified in 77 out of 87 Rickettsia-positive I. ricinus ticks, followed by 8 samples that belonged to Rickettsia monacensis and 2 of the positive ticks were infected with different unidentified Rickettsia spp. Due to the association of R. helvetica and R. monacensis with human infections, it is essential to understand which species of Rickettsia circulate in the natural foci of Slovakia. Circulation of pathogenic rickettsiae in urban as well as natural habitats at different altitudinal levels in Slovakia emphasizes that infection risk is very common throughout this Central European country.