Borrelia burgdorferi sensu lato (s.l.) is maintained in nature by complex zoonotic transmission cycles, involving a large variety of vertebrates as hosts and hard ticks of the genus Ixodes as vectors. Recent studies suggest that the genospecies of B. burgdorferi s.l. and sometimes their subtypes are propagated by different spectra of hosts, mainly birds and rodents. In order to test the concept of host-association, we analysed the relationships between Borrelia genospecies, rodent hosts and I. ricinus ticks in an endemic focus of Lyme borreliosis in western Slovakia. Rodents and questing ticks were collected at a forested low land locality near Bratislava. Tick infestation levels on rodents were determined, and spirochaete infections in ticks and in ear punch biopsies were analysed by PCR followed by genotyping. Mice were more heavily infested with ticks than bank voles, and a higher proportion of mice was infected with spirochactes than voles. However, the infectivity of soles was much higher than that of mice. The vast majority of infections detected in the skin and in ticks feeding on the rodents represented B. afzelii. In contrast, more than half of all infections in questing ticks collected in the same region of Slovakia were identified as B. valaisiana and B. garinii. In conclusion, whilst the study reveals that mice and voles play different quantitative roles in the ecology of Lyme borreliosis, it demonstrates that B. afzelii is specifically maintained by European rodents, validating the concept of host-association of B. burgdorferi s.l.

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.Lyme borreliosis is the most frequent arthropod-borne disease in humans living in moderate climates. Under the umbrella of the wider taxon Borrelia burgdorferi sensu lato, the bacteria constitute a group of 11 named genospecies, which were delineated based on DNA-DNA hybridization and sequence divergence of selected loci (2,32,34,39,40). In Europe, six genospecies are recorded as infecting Ixodes ricinus ticks (8,15,25), and the most prevalent genospecies are B. afzelii, B. garinii, and B. valaisiana (13, 25). In contrast to the case in northern America, B. burgdorferi sensu stricto and B. bissettii are relatively rare in Europe (8,13,15,25). B. lusitaniae seems to be restricted to the western Mediterranean Basin, where its infection prevalence in ticks has been reported to be very high locally (3).Since the delineation of genospecies in B. burgdorferi sensu lato, it has been discussed whether the species complex is differentiated ecologically (4,17,18,26,44 B. valaisiana (12, 17, 19, 27, 29). The transmission model also predicts that bird-and rodent-associated ecotypes of B. burgdorferi sensu lato segregate in individual questing ticks, a prediction that has also been validated (25).The present work was carried out in a region of Europe where B. afzelii, B. garinii, and B. valaisiana are prevalent in questing ticks. In a previous study carried out in the same region, we have demonstrated that rodents are the reservoir hosts of B. afzelii but not of B. garinii and B. valaisiana (13). For this reason, hosts other than rodents must contribute to the prevalence of B. garinii and B. valaisiana in questing tic...

Blackbirds (Turdus merula) and song thrushes (Turdus philomelos) were found to carry 95% of all spirocheteinfected 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.Lyme borreliosis is a tick-transmitted zoonosis caused by spirochete bacteria from the genus Borrelia. This genus comprises 13 named species, and at least 4 of these cause disease in humans, namely, Borrelia burgdorferi, Borrelia spielmanii, Borrelia afzelii, and Borrelia garinii (1,14). All known strains of Lyme borreliosis spirochetes are maintained in nature by vertebrate hosts and ixodid ticks, with humans being ecological dead-end hosts.For Europe, pheasants (Phasianus colchicus), a few seabird species, and some passerine bird species have been shown to be reservoir competent for B. garinii and B. valaisiana but not for B. afzelii, a rodent specialist (4,5,6,7,13). However, little is known about the roles of the numerous European woodland bird species in the ecology of Lyme borreliosis spirochetes (2, 13). Therefore, we captured birds of a wide range of species, many of which are migratory, and determined their importance as hosts to ticks and as reservoirs for Lyme borreliosis spirochetes in selected sites of Central Europe.Ticks were collected from birds captured in four woodlands in Slovakia (16) during 2001 and 2002 and, in 2003, at one woodland in the southeastern Czech Republic. Questing adult and nymphal Ixodes ricinus ticks were collected from Slovak sites. Extracted DNA (3) was subjected to nested PCR targeting the 5S-23S intergenic spacer and also, in some cases, the flaB gene of Lyme borreliosis spirochetes (8, 15). Spirochete infections determined in ticks were assigned to species by the reverse line blot assay (5,8,15) or by DNA sequencing.Risk factors for tick infestation and infection with B. burgdorferi genospecies were investigated in negative binomial and logistic regression models, respectively. Explanatory variables were month, year, site, and bird species. Data from the Czech Republic were excluded because of differences in collection year and bird species range. The level of significance was set at a P value of Ͻ0.05. Because of the poor fit of Poisson regression models, the negative binomial models were used. For detailed statistical methods and results, see the supplemental material.Tick infestations of birds. Of 529 birds captured (345 and 184 at sites in Slovakia and the Czech Republic, respectively, comprising 40 species of 17 families), 187 (145 in Slovakia and 42 in the Czech Republic) carried I. ricinus (463 and 157 larvae and 375 and 495 nymphs in Slovakia and the Czech Republic, respectively) (Table 1). In Slovakia, blackbirds (Turdus merula), song thrushes (Turdus philomelos), and European robins (Erithacus rubecula) carried 55.6% of all collected I. ricinus ticks. In the Czech Republic, Europea...

Borrelia spirochetes in bird-feeding ticks were studied in the Czech Republic. During the postbreeding period (July to September 2005), 1,080 passerine birds infested by 2,240 Ixodes ricinus subadult ticks were examined. Borrelia garinii was detected in 22.2% of the ticks, Borrelia valaisiana was detected in 12.8% of the ticks, Borrelia afzelii was detected in 1.6% of the ticks, and Borrelia burgdorferi sensu stricto was detected in 0.3% of the ticks. After analysis of infections in which the blood meal volume and the stage of the ticks were considered, we concluded that Eurasian blackbirds (Turdus merula), song thrushes (Turdus philomelos), and great tits (Parus major) are capable of transmitting B. garinii; that juvenile blackbirds and song thrushes are prominent reservoirs for B. garinii spirochetes; that some other passerine birds investigated play minor roles in transmitting B. garinii; and that the presence B. afzelii in ticks results from infection in a former stage. Thus, while B. garinii transmission is associated with only a few passerine bird species, these birds have the potential to distribute millions of Lyme disease spirochetes between urban areas.Lyme borreliosis, the most frequent tick-borne human disease in the northern hemisphere, is a multisystemic disorder caused by spirochetes belonging to the genus Borrelia (12). At least seven Borrelia species have been obtained from the tick Ixodes ricinus (Acari: Ixodidae) in Europe: B. afzelii, B. bissettii, B. burgdorferi, B. garinii, B. lusitaniae, B. spielmanii, and B. valaisiana (30,33). Various reservoir hosts seem to harbor different Borrelia species, which is explained by differential properties of the hosts' complement systems (17). Generally, B. afzelii is a rodent specialist, B. garinii and B. valaisiana are associated with birds, and B. lusitaniae is associated with lizards (7,16,22,32). The clinical manifestations of Lyme borreliosis in humans differ depending on the Borrelia species; B. garinii is associated with neurological diseases, while B. burgdorferi and B. afzelii are more likely to cause arthritis and cutaneous symptoms, respectively (2, 4, 5, 36).Ixodid ticks may attach to a host for 24 to 48 h, which is sufficient time for some birds to travel hundreds of kilometers along migration routes before ticks complete their feeding and drop off (31). The role of migratory birds in distributing Lyme disease spirochetes to new areas has been established in North America (25,28,37).Recently, it has become clear that the bird host competency for maintaining and transmitting Borrelia spirochetes is different in different bird species. Pheasants in the United Kingdom (15, 16) and blackbirds and song thrushes in Central Europe (13, 35) have been shown to be important reservoirs of B. garinii and B. valaisiana. However, little is known about the other migrating passerine bird species with respect to their competence as Lyme disease reservoirs and transmission abilities.Here we characterized tick infestation in migratory passerine bird species ...