Prevalence of Borrelia burgdorferi sensu lato and Anaplasmataceae members in Ixodes ricinus ticks in Alsace, a focus of Lyme borreliosis endemicity in France

Due to the high Lyme borreliosis incidence in Alsace, in northeastern France, we investigated in 2003-2004 three cantons in this region in order to determine the density of Ixodes ricinus ticks infected by Borrelia burgdorferi sensu lato and Anaplasmataceae. The peak density of nymphs infected by B. burgdorferi sensu lato at Munster and Guebwiller, where the disease incidence was high, was among the highest reported in Europe (105 and 114 per 100 m(2), respectively). In contrast, the peak density of infected nymphs was low in the canton of Dannemarie (5/100 m(2)), where the disease incidence was low. The two main species detected in ticks were Borrelia afzelii, more frequent in nymphs, and Borrelia garinii, more frequent in adult ticks. The rates of tick infection by Anaplasma phagocytophilum were 0.4% and 1.2% in nymphs and adults, respectively.     

Identification of a New Borrelia Species among Small Mammals in Areas of Northern Spain Where Lyme Disease Is Endemic

The role of small mammals as reservoir hosts for Borrelia burgdorferi was investigated in several areas where Lyme disease is endemic in northern Spain. A low rate of infestation by Ixodes ricinus nymphs was found in the small mammal populations studied that correlated with the near-absence of B. burgdorferi sensu lato in 184 animals tested and with the lack of transmission of B. burgdorferi sensu lato to I. ricinus larvae that fed on them. In contrast, questing ticks collected at the same time and in the same areas were found to carry a highly variable B. burgdorferi sensu lato repertoire (B. burgdorferi sensu stricto, Borrelia garinii, Borrelia valaisiana, and Borrelia afzelii). Interestingly, the only isolate obtained from small mammals (R57, isolated from a bank vole) grouped by phylogenetic analyses with other Borrelia species but in a separate clade from the Lyme disease and relapsing fever organisms, suggesting that it is a new species. This new agent was widely distributed among small mammals, with infection rates of 8.5 to 12% by PCR. Moreover, a high seroprevalence to B. burgdorferi sensu lato was found in the animal sera, suggesting cross-reactivity between B. burgdorferi sensu lato and R57. Although small mammals do not seem to play an important role as reservoirs for B. burgdorferi sensu lato in the study area, they seem to be implicated in the maintenance of spirochetes similar to R57.     

Substantial Rise in the Prevalence of Lyme Borreliosis Spirochetes in a Region of Western Germany over a 10-Year Period

More than a decade after a study on the transmission cycle of Borrelia burgdorferi sensu lato in the Siebengebirge, a nature reserve near Bonn, Germany, questing nymphal and adult Ixodes ricinus ticks were collected again in three selected areas of the same low mountain range and examined for infection with B. burgdorferi sensu lato. Between May and October 2001, a total of 1,754 ticks were collected by blanket dragging; 374 ticks were analyzed for B. burgdorferi sensu lato by both an immunofluorescence assay (IFA) and at least two different PCR tests, whereas 171 ticks were analyzed by PCR only. By combining all assays, an average of 14% of the ticks tested positive for B. burgdorferi sensu lato, 5.5, 15.8, and 21.8% in the three collection areas. Of the nymphs and adults examined, 12.9 and 21.1%, respectively, were found to be spirochete infected. A lower total infection prevalence was obtained by IFA (14.4%) than by a nested PCR approach (16.5%), but both were higher than that obtained by a simple PCR approach (11.9%). Compared with data collected over a decade ago, the mean infection prevalence of B. burgdorferi sensu lato in the ticks was significantly higher for all three biotopes, whereas a similar pattern of habitat-specific infection prevalence was observed. Genotyping of B. burgdorferi sensu lato revealed high relative prevalences of B. valaisiana (identified in 43.1% of infected ticks) and B. garinii (32.3%), whereas B. afzelii (12.3%) and B. burgdorferi sensu stricto (1.5%) were relatively rare. We conclude that B. burgdorferi sensu lato infection has increased in this region over the last 15 years due to presently unknown changes in ecological conditions, perhaps related to climate change or wildlife management.     

Differential Transmission of the Genospecies of Borrelia burgdorferi Sensu Lato by Game Birds and Small Rodents in England

The genetic diversity of Borrelia burgdorferi sensu lato was assessed in a focus of Lyme borreliosis in southern Britain dominated by game birds. Ticks, rodents, and pheasants were analyzed for spirochete infections by PCR targeting the 23S-5S rRNA genes, followed by genotyping by the reverse line blot method. In questing Ixodes ricinus ticks, three genospecies of B. burgdorferi sensu lato were detected, with the highest prevalences found for Borrelia garinii and Borrelia valaisiana. B. burgdorferi sensu stricto was rare (<1%) in all tick stages. Borrelia afzelii was not detected in any of the samples. More than 50% of engorged nymphs collected from pheasants were infected with borreliae, mainly B. garinii and/or B. valaisiana. Although 19% of the rodents harbored B. burgdorferi sensu stricto and/or B. garinii in internal organs, only B. burgdorferi sensu stricto was transmitted to xenodiagnostic tick larvae (it was transmitted to 1% of the larvae). The data indicate that different genospecies of B. burgdorferi sensu lato can be maintained in nature by distinct transmission cycles involving the same vector tick species but different vertebrate host species. Wildlife management may have an influence on the relative risk of different clinical forms of Lyme borreliosis.     

Molecular Identification and Analysis of Borrelia burgdorferi Sensu Lato in Lizards in the Southeastern United States

Lyme borreliosis (LB) group spirochetes, collectively known as Borrelia burgdorferi sensu lato, are distributed worldwide. Wild rodents are acknowledged as the most important reservoir hosts. Ixodes scapularis is the primary vector of B. burgdorferi sensu lato in the eastern United States, and in the southeastern United States, the larvae and nymphs mostly parasitize certain species of lizards. The primary aim of the present study was to determine whether wild lizards in the southeastern United States are naturally infected with Lyme borreliae. Blood samples obtained from lizards in Florida and South Carolina were tested for the presence of LB spirochetes primarily by using B. burgdorferi sensu lato-specific PCR assays that amplify portions of the flagellin (flaB), outer surface protein A (ospA), and 66-kDa protein (p66) genes. Attempts to isolate spirochetes from a small number of PCR-positive lizards failed. However, PCR amplification and sequence analysis of partial flaB, ospA, and p66 gene fragments confirmed numerous strains of B. burgdorferi sensu lato, including Borrelia andersonii, Borrelia bissettii, and B. burgdorferi sensu stricto, in blood from lizards from both states. B. burgdorferi sensu lato DNA was identified in 86 of 160 (54%) lizards representing nine species and six genera. The high infection prevalence and broad distribution of infection among different lizard species at different sites and at different times of the year suggest that LB spirochetes are established in lizards in the southeastern United States.     

Ticks and Lyme borreliosis in an alpine area in northeast Italy

A 2‐year study was conducted in a mountainous area of northeast Italy to evaluate the occurrence and distribution of ticks, as well as to assess the prevalence of the spirochaete Borrelia burgdorferi sensu lato. All ticks collected were Ixodes ricinus L. (Parasitiformes: Ixodidae). In general, most nymphs and adult ticks were collected from April to July. Tick density was highly variable among sites; however, two areas with different infestation levels were recognized. Prevalences of B. burgdorferi s.l. in nymphal stages were rather variable between sites; overall the prevalence of infected nymphs in the whole area was slightly higher than 20%. The prevalence of B. burgdorferi s.l. in nymphs does not seem to be correlated with nymph density. The correlation between the incidence of Lyme borreliosis (reported human cases/1000 inhabitants/year) and Borrelia prevalence in nymphs was not significant, although a significant correlation was found between borreliosis incidence and nymph density.     

Seasonal dynamics of tick burden and associated Borrelia burgdorferi s.l. and Borrelia miyamotoi infections in rodents in a Dutch forest ecosystem

Ixodes ricinus ticks transmit Borrelia burgdorferi sensu lato (s.l.) as well as Borrelia miyamotoi. Larvae become infected when feeding on infected rodents, with horizontal transmission of B. burgdorferi and horizontal and vertical transmission of B. miyamotoi. We studied seasonal dynamics of infection rates of I. ricinus and their rodent hosts, and hence transmission risk of these two distinctly different Borrelia species. Rodents were live-trapped and inspected for ticks from May to November in 2013 and 2014 in a forest in The Netherlands. Trapped rodents were temporarily housed in the laboratory and detached ticks were collected. Borrelia infections were determined from the trapped rodents and collected ticks. Borrelia burgdorferi s.l. and B. miyamotoi were found in ticks as well as in rodents. Rodent density was higher in 2014, whereas tick burden as well as the Borrelia infection rates in rodents were higher in 2013. The density of B. miyamotoi-infected nymphs did not differ between the years. Tick burdens were higher on Apodemus sylvaticus than on Myodes glareolus, and higher on males than on females. Borrelia-infection rate of rodents varied strongly seasonally, peaking in summer. As the larval tick burden also peaked in summer, the generation of infected nymphs was highest in summer. We conclude that the heterogeneity of environmental and host-specific factors affects the seasonal transmission of Borrelia spp., and that these effects act more strongly on horizontally transmitted B. burgdorferi spp. than on the vertically transmitted B. miyamotoi.

     

Association of Borrelia garinii and B. valaisiana with Songbirds in Slovakia

In Europe, 6 of the 11 genospecies of Borrelia burgdorferi sensu lato are prevalent in questing Ixodes ricinus ticks. In most parts of Central Europe, B. afzelii, B. garinii, and B. valaisiana are the most frequent species, whereas B. burgdorferi sensu stricto, B. bissettii, and B. lusitaniae are rare. Previously, it has been shown that B. afzelii is associated with European rodents. Therefore, the aim of this study was to identify reservoir hosts of B. garinii and B. valaisiana in Slovakia. Songbirds were captured in a woodland near Bratislava and investigated for engorged ticks. Questing I. ricinus ticks were collected in the same region. Both tick pools were analyzed for spirochete infections by PCR, followed by DNA-DNA hybridization and, for a subsample, by nucleotide sequencing. Three of the 17 captured songbird species were infested with spirochete-infected ticks. Spirochetes in ticks that had fed on birds were genotyped as B. garinii and B. valaisiana, whereas questing ticks were infected with B. afzelii, B. garinii, and B. valaisiana. Furthermore, identical ospA alleles of B. garinii were found in ticks that had fed on the birds and in questing ticks. The data show that songbirds are reservoir hosts of B. garinii and B. valaisiana but not of B. afzelii. This and previous studies confirm that B. burgdorferi sensu lato is host associated and that this bacterial species complex contains different ecotypes.     

Prevalence of Borrelia burgdorferi Sensu Lato in Ticks Collected from Migratory Birds in Switzerland

The prevalence of ticks infected by Borrelia burgdorferi sensu lato on birds during their migrations was studied in Switzerland. A total of 1,270 birds captured at two sites were examined for tick infestation. Ixodes ricinus was the dominant tick species. Prevalences of tick infestation were 6% and 18.2% for birds migrating northward and southward, respectively. Borrelia valaisiana was the species detected most frequently in ticks, followed by Borrelia garinii and Borrelia lusitaniae. Among birds infested by infected ticks, 23% (6/26) were infested by B. lusitaniae-infected larvae. Migratory birds appear to be reservoir hosts for B. lusitaniae.     

The importance of passerine birds as tick hosts and in the transmission of Borrelia burgdorferi,the agent of Lyme disease: a case study from Scotland

Borrelia burgdorferi sensu lato (s.l.) is the causative agent of Lyme borreliosis, the most common tick‐borne zoonosis of humans in Europe and North America. Here, we assessed the relative importance of different passerine bird species as tick hosts and their contribution to the B. burgdorferi s.l. transmission cycle in a rural residential area in Scotland. We caught 1229 birds of 22 species during the tick‐questing season. On average, 29% carried larval ticks (0.8 larvae per individual) and 5% carried nymph ticks (0.06 nymphs per individual). All attached ticks tested were Ixodes ricinus. Using a nested‐PCR, we found that 20% of nymphs tested positive to B. burgdorferi s.l. and all these were of the genospecies Borrelia garinii. We identified two new bird species carrying infected nymphs: Eurasian Siskin Carduelis spinus and European Greenfinch Carduelis chloris. Ground‐foraging species were more important than arboreal species in hosting I. ricinus nymphs and B. burgdorferi s.l. Common Blackbirds Turdus merula were the most common hosts, with Song Thrushes Turdus philomelos, Dunnocks Prunella modularis, European Greenfinches and Chaffinches Fringilla coelebs also hosting high rates of infection.     

Longitudinal Analysis of Tick Densities and Borrelia, Anaplasma, and Ehrlichia Infections of Ixodes ricinus Ticks in Different Habitat Areas in The Netherlands

From 2000 to 2004, ticks were collected by dragging a blanket in four habitat areas in The Netherlands: dunes, heather, forest, and a city park. Tick densities were calculated, and infection with Borrelia burgdorferi and Anaplasma and Ehrlichia species was investigated by reverse line blot analysis. The lowest tick density was observed in the heather area (1 to 8/100 m²). In the oak forest and city park, the tick densities ranged from 26 to 45/100 m². The highest tick density was found in the dune area (139 to 551/100 m²). The infection rates varied significantly for the four study areas and years, ranging from 0.8 to 11. 5% for Borrelia spp. and 1 to 16% for Ehrlichia or Anaplasma (Ehrlichia/Anaplasma) spp. Borrelia infection rates were highest in the dunes, followed by the forest, the city park, and heather area. In contrast, Ehrlichia/Anaplasma was found most often in the forest and less often in the city park. The following Borrelia species were found: Borrelia sensu lato strains not identified to the species level (2.5%), B. afzelii (2.5%), B. valaisiana (0.9%), B. burgdorferi sensu stricto (0.13%), and B. garinii (0.13%). For Ehrlichia/Anaplasma species, Ehrlichia and Anaplasma spp. not identified to the species level (2.5%), Anaplasma schotti variant (3.5%), Anaplasma phagocytophilum variant (0.3%), and Ehrlichia canis (0.19%) were found. E. canis is reported for the first time in ticks in The Netherlands in this study. Borrelia lusitaniae, Ehrlichia chaffeensis, and the human granylocytic anaplasmosis agent were not detected. About 1.6% of the ticks were infected with both Borrelia and Ehrlichia/Anaplasma, which was higher than the frequency predicted from the individual infection rates, suggesting hosts with multiple infections or a possible selective advantage of coinfection.     

Ecological Factors Characterizing the Prevalence of Bacterial Tick-Borne Pathogens in Ixodes ricinus Ticks in Pastures and Woodlands

Ecological changes are recognized as an important driver behind the emergence of infectious diseases. The prevalence of infection in ticks depends upon ecological factors that are rarely taken into account simultaneously. Our objective was to investigate the influences of forest fragmentation, vegetation, adult tick hosts, and habitat on the infection prevalence of three tick-borne bacteria, Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum, and Rickettsia sp. of the spotted fever group, in questing Ixodes ricinus ticks, taking into account tick characteristics. Samples of questing nymphs and adults were taken from 61 pastures and neighboring woodlands in central France. The ticks were tested by PCR of pools of nymphs and individual adults. The individual infection prevalence was modeled using multivariate regression. The highest infection prevalences were found in adult females collected in woodland sites for B. burgdorferi sensu lato and A. phagocytophilum (16.1% and 10.7%, respectively) and in pasture sites for Rickettsia sp. (8.7%). The infection prevalence in nymphs was lower than 6%. B. burgdorferi sensu lato was more prevalent in woodlands than in pastures. Forest fragmentation favored B. burgdorferi sensu lato and A. phagocytophilum prevalence in woodlands, and in pastures, the B. burgdorferi sensu lato prevalence was favored by shrubby vegetation. Both results are probably because large amounts of edges or shrubs increase the abundance of small vertebrates as reservoir hosts. The Rickettsia sp. prevalence was maximal on pasture with medium forest fragmentation. Female ticks were more infected by B. burgdorferi sensu lato than males and nymphs in woodland sites, which suggests an interaction between the ticks and the bacteria. This study confirms the complexity of the tick-borne pathogen ecology. The findings support the importance of small vertebrates as reservoir hosts and make a case for further studies in Europe on the link between the composition of the reservoir host community and the infection prevalence in ticks.Ecological modifications are recognized as one of the main forces behind the emergence of infectious diseases (37). As vectors and wildlife are very sensitive to environmental conditions, ecological changes are expected to have a particular impact on the epidemiology of vector-borne diseases and those with a wildlife origin (29, 48). Several studies have highlighted the influence of factors such as climate change and habitat fragmentation on the risk of tick-borne diseases (20, 67). The risk of a tick-borne disease being transmitted to humans or to animals is closely linked to the prevalence of pathogens in ticks questing for hosts (38, 58). In turn, infection prevalence directly depends on the probability of ticks feeding on an infected reservoir host. This probability results from a combination of the intrinsic characteristics of the species involved (e.g., the host species feeding preference of the tick and the ability of the pathogen to infect different host species) and the characteristics of the host community (e.g., the likelihood of contact between ticks and infected reservoir hosts) that vary in time and space. Due to the difficulty of directly assessing the host community, it may be characterized indirectly by studying landscape and habitat features (3, 9). The increased fragmentation of deciduous forests, for example, favors infection prevalence in ticks that are the agents of Lyme disease in the eastern United States because this fragmentation pattern favors the abundance of a highly competent host reservoir, the white-footed mouse (Peromyscus leucopus) (1, 12). However, studies of the effect of habitat fragmentation on different tick-borne pathogens are scarce (25, 40, 67). Most only report on the infection prevalence of pathogens in ticks according to sampling locations, the stage of tick development, and their sex (18, 56); few studies take into account the interplay or simultaneous effects of explanatory environmental factors (2).In Europe, the Ixodes ricinus tick is one of the most important vectors for animal and human pathogens, especially bacteria (21). These include pathogenic species of the complex Borrelia burgdorferi sensu lato, the agent of Lyme borreliosis, the most prevalent vector-borne human disease in Europe (57); Anaplasma phagocytophilum, the agent of human and animal granulocytic anaplasmosis, considered to be an emerging disease both in human and in animals (8, 61); and Rickettsia helvetica of the spotted fever group, known to be responsible for nonspecific fevers in humans (28).Although they share the same tick vector, B. burgdorferi sensu lato, A. phagocytophilum, and R. helvetica have different ecological cycles and transmission patterns which influence the infection prevalence at different stages of a tick''s life. For B. burgdorferi sensu lato, the maintenance cycle of the bacteria depends on immature stages of I. ricinus ticks feeding on infected reservoir hosts, mainly small rodents and birds that feed on the ground (36, 62). For A. phagocytophilum, small mammals and ruminants are reservoir hosts (16, 22, 69). In contrast to the other two pathogens, R. helvetica is transovarially and sexually transmitted in ticks (13, 33). Ticks are thus considered to be a reservoir host for the bacteria. Small rodents are also suspected to be reservoir hosts in Europe (45), while the role of ungulates remains unknown (60).It is increasingly recognized that a better understanding of the variation of the prevalence of pathogens in ticks within regions of endemicity is critical to the rational design and monitoring of control programs (47). Our objective was to run an exploratory analysis to test the influence of a range of factors on variations in the prevalence of B. burgdorferi sensu lato, A. phagocytophilum, and Rickettsia sp. of the spotted fever group in questing I. ricinus ticks. The factors considered were two habitats (pasture and woodland), forest fragmentation metrics, the vegetation around and near the pasture, and adult tick hosts (deer and cattle); and the analysis took into account factors linked to tick characteristics (tick sex, tick stage, and the density of questing nymphs). Consequently, we analyzed ticks collected in the field for the presence of DNA from the three bacteria and ran an exploratory statistical model using multivariate regression.     

Habitat-Specific Diversity of Borrelia burgdorferi Sensu Lato in Europe, Exemplified by Data from Latvia

The distribution of Borrelia burgdorferi sensu lato genospecies in questing Ixodes ricinus ticks from ecologically distinct habitats in Latvia was analyzed. A significant variation in the frequency of the genospecies across sites was observed, pointing to the importance of the host community in the ecology of Lyme borreliosis.     

Introduced Siberian chipmunks (Tamias sibiricus barberi) harbor more-diverse Borrelia burgdorferi sensu lato genospecies than native bank voles (Myodes glareolus)

Little attention has been given in scientific literature to how introduced species may act as a new host for native infectious agents and modify the epidemiology of a disease. In this study, we investigated whether an introduced species, the Siberian chipmunk (Tamias sibiricus barberi), was a potentially new reservoir host for Borrelia burgdorferi sensu lato, the causative agent of Lyme disease. First, we ascertained whether chipmunks were infected by all of the B. burgdorferi sensu lato genospecies associated with rodents and available in their source of infection, questing nymphs. Second, we determined whether the prevalence and diversity of B. burgdorferi sensu lato in chipmunks were similar to those of a native reservoir rodent, the bank vole (Myodes glareolus). Our research took place between 2006 and 2008 in a suburban French forest, where we trapped 335 chipmunks and 671 voles and collected 743 nymphs of ticks that were questing for hosts by dragging on the vegetation. We assayed for B. burgdorferi sensu lato with ear biopsy specimens taken from the rodents and in nymphs using PCR and restriction fragment length polymorphism (RFLP). Chipmunks were infected by the three Borrelia genospecies that were present in questing nymphs and that infect rodents (B. burgdorferi sensu stricto, B. afzelii, and B. garinii). In contrast, voles hosted only B. afzelii. Furthermore, chipmunks were more infected (35%) than voles (16%). These results may be explained by the higher exposure of chipmunks, because they harbor more ticks, or by their higher tolerance of other B. burgdorferi sensu lato genospecies than of B. afzelii. If chipmunks are competent reservoir hosts for B. burgdorferi sensu lato, they may spill back B. burgdorferi sensu lato to native communities and eventually may increase the risk of Lyme disease transmission to humans.     

Seroprevalence of <Emphasis Type="Italic">Borrelia burgdorferi</Emphasis> sensu lato and <Emphasis Type="Italic">Anaplasma phagocytophilum</Emphasis> in Danish horses

Background

Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum are able to infect horses. However, the extend to which Danish horses are infected and seroconvert due to these two bacteria is unknown. The aim of the present study was to evaluate the seroprevalence of B. burgdorferi sensu lato and A. phagocytophilum in Danish horses.

Methods

A total of 390 blood samples collected from all major regions of Denmark and with a geographical distribution corresponding to the density of the Danish horse population were analyzed. All samples were examined for the presence of antibodies against B. burgdorferi sensu lato and A. phagocytophilum by the use of the SNAP^®4DX ^® ELISA test.

Results

Overall, 29.0% of the horses were seropositive for B. burgdorferi sensu lato whereas 22.3% were seropositive for A. phagocytophilum.

Conclusions

Antibodies against B burgdorferi sensu lato and A. phagocytophilum are commonly found among Danish horses thus showing that Danish horses are frequently infected by these organisms.

     

First report of lyme disease spirochetes in ticks from Romania (Sibiu County)

We examined 200 questing Ixodes ricinus ticks (nymphs and adults) collected in three different sites in Sibiu County, Romania by polymerase chain reaction (PCR) followed by reverse line blot (RLB) for Borrelia burgdorferi s.l.. We detected the bacteria in 19% of the investigated ticks. The prevalence of infection was higher in nymphs (27%) than in adults (12%). Two B. burgdorferi sensu lato genospecies were detected: B. garinii (20%) and B. afzelii (80%). We did not detect any mixed infections in the investigated ticks. In two of the investigated sites B. burgdorferi prevalence values were comparable (25%), while in the third site the prevalence was lower (≈7%). Our preliminary study provides evidence that Lyme disease spirochetes are present in various areas and at a relatively high prevalence in their vectors, thus posing a risk of infection to human subjects that undergo work or leisure activities in those areas.     

Organization of Ribosomal RNA Genes in Borrelia burgdorferi sensu lato Isolated from Ixodes ovatus in Japan

Borrelia burgdorferi sensu lato was obtained from adult ixodid ticks, Ixodes ovatus, collected in Nagano, Japan, and was named NT112. The genomic DNA was digested with enzymes, electrophoresed, blotted and hybridized with rRNA gene probes obtained from B. burgdorferi sensu stricto B31. The results showed that the borrelial chromosome contains a single rrs (16S rRNA gene) sequence and two copies of rrl/rrf (23S/5S rRNA genes) sequences. The rrl/rrf genes were tandemly repeated at intervals of 3.2 kb and were located separately from the rrs gene on the genome. Our findings indicate that the organization of rRNA genes in Borrelia from I. ovatus ticks is identical to that of B. burgdorferi sensu stricto.     

Local variations in the distribution and prevalence of Borrelia burgdorferi sensu lato genomospecies in Ixodes ricinus ticks.

Unfed nymphal and adult Ixodes ricinus ticks were collected from five locations within the 10,000-ha Killarney National Park, Ireland. The distribution and prevalence of the genomospecies of Borrelia burgdorferi sensu lato in the ticks were investigated by PCR amplification of the intergenic spacer region between the 5S and 23S rRNA genes and by reverse line blotting with genomospecies-specific oligonucleotide probes. The prevalence of ticks infected with B. burgdorferi sensu lato was significantly variable between the five locations, ranging from 11.5 to 28.9%. Four genomospecies were identified as B. burgdorferi sensu stricto, Borrelia afzelii, Borrelia garinii, and VS116. Additionally, untypeable B. burgdorferi sensu lato genomospecies were identified in two nymphs. VS116 was the most prevalent of the genomospecies and was identified in 50% of the infected ticks. Prevalences of B. garinii and B. burgdorferi sensu stricto were similar (17 and 18%, respectively); however, significant differences were observed in the prevalence of these genomospecies in mixed infections (58.8 and 23.5%, respectively). Notably, the prevalence of B. afzelii was low, comprising 9.6 and 7.4%, respectively, of single and mixed infections. Significant variability was observed in the distribution and prevalence of B. burgdorferi sensu lato genomospecies between locations in the park, and the diversity and prevalence of B. burgdorferi sensu lato genomospecies was typically associated with woodland. The distributions of B. burgdorferi sensu lato genomospecies were similar in wooded areas and in areas bordering woodland, although the prevalence of B. burgdorferi sensu lato infection was typically reduced. Spatial distributions vegetation composition, and host cenosis of the habitats were identified as factors which may affect the distribution and prevalence of B. burgdorferi sensu lato genomospecies within the park.     

Prevalence of Borrelia burgdorferi Sensu Lato Genospecies in Ixodes ricinus Ticks in Europe: a Metaanalysis

In Europe, Borrelia burgdorferi genospecies causing Lyme borreliosis are mainly transmitted by the tick Ixodes ricinus. Since its discovery, B. burgdorferi has been the subject of many epidemiological studies to determine its prevalence and the distribution of the different genospecies in ticks. In the current study we systematically reviewed the literature on epidemiological studies of I. ricinus ticks infected with B. burgdorferi sensu lato. A total of 1,186 abstracts in English published from 1984 to 2003 were identified by a PubMed keyword search and from the compiled article references. A multistep filter process was used to select relevant articles; 110 articles from 24 countries contained data on the rates of infection of I. ricinus with Borrelia in Europe (112,579 ticks), and 44 articles from 21 countries included species-specific analyses (3,273 positive ticks). These data were used to evaluate the overall rate of infection of I. ricinus with Borrelia genospecies, regional distributions within Europe, and changes over time, as well as the influence of different detection methods on the infection rate. While the infection rate was significantly higher in adults (18.6%) than in nymphs (10.1%), no effect of detection method, tick gender, or collection period (1986 to 1993 versus 1994 to 2002) was found. The highest rates of infection of I. ricinus were found in countries in central Europe. B. afzelii and B. garinii are the most common Borrelia species, but the distribution of genospecies seems to vary in different regions in Europe. The most frequent coinfection by Borrelia species was found for B. garinii and B. valaisiana.     

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

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.