Interaction and Transmission of Two Borrelia burgdorferi Sensu Stricto Strains in a Tick-Rodent Maintenance System

In the northeastern United States, the Lyme disease agent, Borrelia burgdorferi sensu stricto, is maintained by enzoonotic transmission, cycling between white-footed mice (Peromyscus leucopus) and black-legged ticks (Ixodes scapularis). B. burgdorferi sensu stricto is genetically variable and has been divided into three major genotypes based on 16S-23S ribosomal DNA spacer (RST) analysis. To better understand how genetic differences in B. burgdorferi sensu stricto may influence transmission dynamics in nature, we investigated the interaction between an RST1 and an RST3 strain in a laboratory system with P. leucopus mice and I. scapularis ticks. Two groups of mice were infected with either BL206 (RST1) or B348 (RST3). Two weeks later, experimental mice were challenged with the opposite strain, while control mice were challenged with the same strain as that used for the primary infection. The transmission of BL206 and B348 from infected mice was then determined by xenodiagnosis with uninfected larval ticks at weekly intervals for 42 days. Mice in both experimental groups were permissive for infection with the second strain and were able to transmit both strains to the xenodiagnostic ticks. However, the overall transmission efficiencies of BL206 and B348 were significantly different. BL206 was more efficiently transmitted than B348 to xenodiagnostic ticks. Significantly fewer double infections than expected were detected in xenodiagnostic ticks. The results suggest that some B. burgdorferi sensu stricto strains, such as BL206, may be preferentially maintained in transmission cycles between ticks and white-footed mice. Other strains, such as B348, may be more effectively maintained in different tick-vertebrate transmission cycles.     

Fitness Variation of Borrelia burgdorferi Sensu Stricto Strains in Mice

Lyme borreliosis in North America is caused by the tick-borne spirochete Borrelia burgdorferi, a zoonotic bacterium that is able to persistently infect a wide range of vertebrate species. Given the pronounced strain structure of B. burgdorferi in the northeastern United States, we asked whether the fitness of the different genotypes varies among susceptible vertebrate hosts. The transmission dynamics of two genetically divergent human isolates of B. burgdorferi, BL206 and B348, were analyzed experimentally in white-footed mice and in C3H/HeNCrl mice over a time period of almost 3 months. We found that the initially high transmission efficiency from white-footed mice to ticks declined sharply for isolate B348 but remained considerably high for isolate BL206. In contrast, in C3H/HeNCrl mice, high transmission efficiency persisted for both isolates. Our findings provide proof-of-principle evidence for intrinsic fitness variation of B. burgdorferi strains in vertebrate host species, perhaps indicating the beginnings of adaptive radiation.     

Inhibition of Borrelia burgdorferi-tick interactions in vivo by outer surface protein A antibody

Borrelia burgdorferi outer surface protein (Osp) A is preferentially expressed by spirochetes in the Ixodes scapularis gut and facilitates pathogen-vector adherence in vitro. Here we examined B. burgdorferi-tick interactions in vivo by using Abs directed against OspA from each of the three major B. burgdorferi sensu lato genospecies: B. burgdorferi sensu stricto, Borrelia afzelii, and Borrelia garinii. Abs directed against B. burgdorferi sensu stricto (isolate N40) destroy the spirochete and can protect mice from infection. In contrast, antisera raised against OspA from B. afzelii (isolate ACA-1) and B. garinii (isolate ZQ-1) bind to B. burgdorferi N40 but are not borreliacidal against the N40 isolate. Our present studies assess whether these selected OspA Abs interfere with B. burgdorferi-tick attachment in a murine model of Lyme disease with I. scapularis. We examined engorged ticks that had fed on B. burgdorferi N40-infected scid mice previously treated with OspA (N40, ACA-1, ZQ-1, or mAb C3.78) or control Abs. OspA-N40 antisera or mAb C3.78 destroyed B. burgdorferi N40 within the engorged ticks. In contrast, treatment of mice with OspA-ACA-1 and OspA-ZQ-1 antisera did not kill B. burgdorferi N40 within the ticks but did effectively interfere with B. burgdorferi-I. scapularis adherence, thereby preventing efficient colonization of the vector. These studies show that nonborreliacidal OspA Abs can inhibit B. burgdorferi attachment to the tick gut, highlighting the importance of OspA in spirochete-arthropod interactions in vivo.     

Effectiveness of Metarhizium anisopliae (Deuteromycetes) against Ixodes scapularis (Acari: Ixodidae) engorging on Peromnyscus leucopus.

With the incidence of Lyme disease increasing throughout the United States, reducing risk of exposure to the disease is of the utmost concern. In the northeastern U.S., the blacklegged tick, Ixodes scapularis, is the primary vector and the white-footed mouse, (Peromyscus leucopus), the primary reservoir for Borrelia burgdorteri, the bacterium causing Lyme disease. Targeting I. scapularis engorging on white-footed mice with an effective biological control agent, such as the fungus Metarhizium anisopliae, could be an effective and relatively safe control technique. In 2002-2003, we performed laboratory and field experiments to determine whether M anisopliae-treated nesting material could effectively control larval I. scapularis ticks engorging on white-footed mice, and therefore reduce the number of infected nymphal I. scapularis questing the following summer. Our laboratory experiment demonstrated a strong negative effect of M. anisopliae-treated nesting material on survival of I. scapularis larvae feeding on P. leucopus, with 75% versus 35% larval mortality in treatment versus control nests. Our field trials caused only modest, localized reductions in nymphal abundance and had no effect on the proportion of nymphal I. scapularis infected with B. burgdorferi. Field results probably could be improved by increasing the density of nestboxes to allow fungal delivery to a higher proportion of the mouse population and by deploying nestboxes in an area with lower mammalian diversity, such as a suburban landscape.     

Bacteriolytic activity of selected vertebrate sera for Borrelia burgdorferi sensu stricto and Borrelia bissettii

An in vitro assay to evaluate the bacteriolytic activity of the complement pathway was applied to 2 strains of Borrelia bissettii, CO501 and DN127, and compared with that of B. burgdorferi sensu stricto B31. Sera from mule deer (Odocoileus hemionus) and the Western Fence lizard (Sceloporus occidentalis) were completely borreliacidal for B. burgdorferi and for both strains of B. bissettii. Serum from Bobwhite quail (Colinus virginianus) was nonlytic for B. burgdorferi and partially lytic for B. bissettii strains, CO-501 and DN127. Serum from a New Zealand White rabbit (Oryctolagus cuniculus) was partially lytic for all 3 strains of Borrelia, whereas serum from white-footed mice (Peromyscus leucopus) were nonlytic for all 3 Borrelia strains. The spectrum of complement sensitivity of B. bissettii appears to be similar to that of European B. afzelii in that tested rodent serum is not lytic to these 2 genospecies. Interestingly, both B. bissettii and B. afzelii have been found to be closely associated with rodents. Complement sensitivity demonstrated in these experiments may suggest and possibly predict specific reservoir-host associations.     

Coinfection with Borrelia burgdorferi sensu stricto and Borrelia garinii alters the course of murine Lyme borreliosis

Ixodes ricinus ticks and mice can be infected with both Borrelia burgdorferi sensu stricto and Borrelia garinii. The effect of coinfection with these two Borrelia species on the development of murine Lyme borreliosis is unknown. Therefore, we investigated whether coinfection with the nonarthritogenic B. garinii strain PBi and the arthritogenic B. burgdorferi sensu stricto strain B31 alters murine Lyme borreliosis. Mice simultaneously infected with PBi and B31 showed significantly more paw swelling and arthritis, long-standing spirochetemia, and higher numbers of B31 spirochetes than did mice infected with B31 alone. However, the number of PBi spirochetes was significantly lower in coinfected mice than in mice infected with PBi alone. In conclusion, simultaneous infection with B. garinii and B. burgdorferi sensu stricto results in more severe Lyme borreliosis. Moreover, we suggest that competition of the two Borrelia species within the reservoir host could have led to preferential maintenance, and a rising prevalence, of B. burgdorferi sensu stricto in European I. ricinus populations.     

Conspicuous impacts of inconspicuous hosts on the Lyme disease epidemic

Emerging zoonotic pathogens are a constant threat to human health throughout the world. Control strategies to protect public health regularly fail, due in part to the tendency to focus on a single host species assumed to be the primary reservoir for a pathogen. Here, we present evidence that a diverse set of species can play an important role in determining disease risk to humans using Lyme disease as a model. Host-targeted public health strategies to control the Lyme disease epidemic in North America have focused on interrupting Borrelia burgdorferi sensu stricto (ss) transmission between blacklegged ticks and the putative dominant reservoir species, white-footed mice. However, B. burgdorferi ss infects more than a dozen vertebrate species, any of which could transmit the pathogen to feeding ticks and increase the density of infected ticks and Lyme disease risk. Using genetic and ecological data, we demonstrate that mice are neither the primary host for ticks nor the primary reservoir for B. burgdorferi ss, feeding 10% of all ticks and 25% of B. burgdorferi-infected ticks. Inconspicuous shrews feed 35% of all ticks and 55% of infected ticks. Because several important host species influence Lyme disease risk, interventions directed at a multiple host species will be required to control this epidemic.     

Improving the specificity of 16S rDNA-based polymerase chain reaction for detecting Borrelia burgdorferi sensu lato-causative agents of human Lyme disease

AIMS: 16S rDNA sequences of Borrelia burgdorferi sensu lato were aligned with the 16S rDNA sequences of Borrelia hermsii, Borrelia turicatae, and Borrelia lonestari in order to identify primers that might be used to more specifically identify agents of human Lyme disease in ticks in human skin samples. METHODS AND RESULTS: Standard polymerase chain reaction (PCR), using an oligonucleotide sequence, designated TEC1, was shown, in combination with a previously developed primer (LD2) to amplify strains of B. burgdorferi sensu stricto, Borrelia afzelii, and Borrelia garinii, but not the non-Lyme causing B. hermsii or B. turicatae. This primer pair, designated Bbsl, was successfully used to amplify B. burgdorferi sensu lato from skin biopsies of patients with Lyme disease symptoms as well as from Ixodes scapularis, Amblyomma americanum and Dermacentor variabilis ticks. CONCLUSIONS: The primer set Bbsl allows for the rapid detection and differentiation of B. burgdorferi sensu lato from non-Lyme disease-causing Borrelia species in ticks and human tissues. SIGNIFICANCE AND IMPACT OF THE STUDY: The PCR primer set, Bbsl, will greatly facilitate detection of the causative agents of Lyme disease in infected ticks and human skin samples assisting in epidemiological studies, and potentially allowing for a more rapid diagnosis of the disease in patients.     

Comparison of the spirochete Borrelia burgdorferi S. L. isolated from the tick Ixodes scapularis in southeastern and northeastern United States

Thirty-five strains of the Lyme disease spirochete Borrelia burgdorferi sensu lato (B. burgdorferi s. l.) were isolated from the blacklegged tick vector Ixodes scapularis in South Carolina, Georgia, Florida, and Rhode Island. They were characterized by PCR-restriction fragment length polymorphism (RFLP) analysis of rrf (5S)-rrl (23S) intergenic spacer amplicons. PCR-RFLP analysis indicated that the strains represented at least 3 genospecies (including a possible novel genospecies) and 4 different restriction patterns. Thirty strains belonged to the genospecies B. burgdorferi sensu stricto (B. burgdorferi s. s.), 4 southern strains were identified as B. bissettii, and strain SCCH-5 from South Carolina exhibited MseI and DraI restriction patterns different from those of previously reported genospecies. Complete sequences of rrf-rrl intergenic spacers from 14 southeastern and northeastern strains were determined and the phylogenetic relationships of these strains were compared. The 14 strains clustered into 3 separate lineages on the basis of sequence analysis. These results were confirmed by phylogenetic analysis based on 16S rDNA sequence analysis.     

Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum, Francisella tularensis and their co-infections in host-seeking Ixodes ricinus ticks collected in Serbia

To evaluate the prevalence rate of tick-borne bacterial pathogens, unfed adult Ixodes ricinus ticks were collected from vegetation in 2001, 2003, and 2004 at 18 localities throughout Serbia. A total of 287 ticks were examined by PCR technique for the presence of Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum, and Francisella tularensis. The highest prevalence rate was that for B. burgdorferi sensu lato (42.5%), followed by A. phagocytophilum (13.9%) and F. tularensis (3.8%). The presence of five B. burgdorferi sensu lato genospecies, namely, B. burgdorferi sensu stricto, B. afzelii, B. garinii, B. lusitaniae, and B. valaisiana was identified by restriction fragment length polymorphism (RFLP) analysis. The most frequent B. burgdorferi sensu lato genospecies was B. lusitaniae, followed by B. burgdorferi sensu stricto. Co-infection by B. burgdorferi sensu stricto and B. lusitaniae was frequently observed. Co-infection by B. burgdorferi sensu lato and A. phagocytophilum and co-infection by B. burgdorferi sensu lato and F. tularensis appeared in 24 ticks. Sequencing of p44/msp2 paralogs of Serbian A. phagocytophilum showed that they were unique and distinct from those of A. phagocytophilum in US and UK. This is the first report of B. garinii, B. lusitaniae, B. valaisiana, as well as A. phagocytophilum and F. tularensis infected ticks in Serbia. These findings indicate a public health threat in Serbia of tick-borne diseases caused by B. burgdorferi sensu lato, A. phagocytophilum and F. tularensis.     

Rapid introduction of Lyme disease spirochete, Borrelia burgdorferi sensu stricto, in Ixodes scapularis (Acari: Ixodidae) established at Turkey Point Provincial Park, Ontario, Canada

Borrelia burgdorferi sensu stricto (s.s.) was isolated from questing adult Ixodes scapularis Say ticks collected from Turkey Point Provincial Park (TPPP), Ontario, Canada during 2005-2006. DNA from ten (67%) of 15 pools of ticks was confirmed positive for B. burgdorferi s.s. using polymerase chain reaction (PCR) by targeting the rrf (5S)-rrl (23S) intergenic spacer region and OspA genes. This significant infection rate indicates an accelerated development of B. burgdorferi s.s. in TPPP, because this pathogen was not detected five years previously during sampling of the three motile life stages of I. scapularis. Our study provides the initial report of the presence of B. burgdorferi s.s. in TPPP, which is now endemic for Lyme disease. Ultimately, people and domestic animals are at risk of contracting Lyme disease when they frequent this park.     

Genetic diversity of Borrelia burgdorferi sensu stricto in Peromyscus leucopus, the primary reservoir of Lyme disease in a region of endemicity in southern Maryland

In the north central and northeastern United States, Borrelia burgdorferi sensu stricto, the etiologic agent of Lyme disease (LD), is maintained in an enzootic cycle between the vector, Ixodes scapularis, and the primary reservoir host, Peromyscus leucopus. Genetic diversity of the pathogen based on sequencing of two plasmid-located genes, those for outer surface protein A (ospA) and outer surface protein C (ospC), has been examined in both tick and human specimens at local, regional, and worldwide population scales. Additionally, previous studies have only been conducted with tick or human specimens at the local population level in areas with high LD transmission rates. This study examined the genetic diversity of circulating borreliae in the reservoir population from a large region of the western coastal plains of southern Maryland, where moderate numbers of human LD cases are reported. Six ospA mobility classes, including two that were not previously described, and eight ospC groups were found among the P. leucopus samples. Twenty-five percent of all specimens were infected with more than one ospA or ospC variant. The frequency distribution of variants was homogeneous, both locally and spatially. The spirochete diversity found in Maryland was not as high as that observed among northern tick populations, yet similar genotypes were observed in both populations. These results also show that mice are important for maintaining Borrelia variants, even rare variants, and that reservoir populations should therefore be considered when assessing the diversity of B. burgdorferi.     

The cell-mediated immune response to Borrelia afzelii, garinii and burgdorferi in C57BL/6 mice is dependent on antigen specificity

Inbred C57BL/6 mice were challenged with Borrelia afzelii, Borrelia garinii and Borrelia burgdorferi sensu stricto and tested for antigen-specific T-cell response in vitro. The sonicated preparations of in vitro grown spirochetes were capable of stimulating polyclonal proliferation and specific cell-mediated response, depending on duration of the cell culture. Murine splenocytes previously sensitized to B. burgdorferi sensu lato (s.l. ), but not those from control mice, could be induced for antigen-specific proliferation in vitro. Moreover, detectable cell-mediated response could be induced only with antigen preparations derived from a corresponding strain but not with those obtained from other Borrelia genospecies as revealed by the [(3)H]thymidine incorporation assay. The current study considers that the strict B. burgdorferi s.l. antigen-specific response may also be expected in infections in humans and contributes to the explanation of the frequently poor antibody- and cell-mediated immune response observed in patients diagnosed with Lyme disease.     

Refractoriness of the western fence lizard (Sceloporus occidentalis) to the Lyme disease group spirochete Borrelia bissettii

The western fence lizard, Sceloporus occidentalis, is refractory to experimental infection with Borrelia burgdorferi sensu stricto, one of several Lyme disease spirochetes pathogenic for humans. Another member of the Lyme disease spirochete complex, Borrelia bissettii, is distributed widely throughout North America and a similar, if not identical, spirochete has been implicated as a human pathogen in southern Europe. To determine the susceptibility of S. occidentalis to B. bissettii, 6 na?ve lizards were exposed to the feeding activities of Ixodes pacificus nymphs experimentally infected with this spirochete. None of the lizards developed spirochetemias detectable by polymerase chain reaction for up to 8 wk post-tick feeding, infected nymphs apparently lost their B. bissettii infections within 1-2 wk after engorgement, and xenodiagnostic L. pacificus larvae that co-fed alongside infected nymphs did not acquire and maintain spirochetes. In contrast, 3 of 4 na?ve deer mice (Peromyscus maniculatus) exposed similarly to feeding by 1 or more B. bissettii-infected nymphs developed patent infections within 4 wk. These and previous findings suggest that the complement system of S. occidentalis typically destroys B. burgdorferi sensu lato spirochetes present in tissues of attached and feeding I. pacificus nymphs, thereby potentially reducing the probability of transmission of these bacteria to humans or other animals by the resultant adult ticks.     

Cell-mediated immune response to high-passage Borrelia spirochetes in C57bl/6 mice is strictly dependent on antigen specificity

Inbred C57bl/6 mice were challenged with high-passage Borrelia afzelii, Borrelia garinii and Borrelia burgdorferi sensu stricto and tested for antigen specific T-cell response in vitro. Sonicated preparations of washed spirochetes were potent cell activators, capable of stimulating polyclonal proliferation after 72h of culture while increasing the incubation time up to 120h provoked specific cell-mediated response. Isolated murine spleocytes previously sensitized to B. burgdorferi sensu lato but not those from control mice could be induced for antigen-specific proliferation in vitro, as revealed by [3H]thymidine incorporation assay, Moreover, in mice presensitized to B. burgdorferi sensu lato, detectable cell-mediated response could be induced only with antigen preparations derived from a corresponding strain but not with those obtained from other Borrelia genospecies. The current study emphasises that the B. burgdorferi antigen-specific response may also be expected in different genospecies infections in men.     

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.     

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.     

The complement regulator factor H binds to the surface protein OspE of Borrelia burgdorferi

Spirochete bacteria of the Borrelia burgdorferi sensu lato complex cause Lyme borreliosis. The three pathogenic subspecies Borrelia garinii, Borrelia afzelii, and Borrelia burgdorferi sensu stricto differ in their disease profiles and susceptibility to complement lysis. We investigated whether complement resistance of Borreliae could be due to acquisition of the main soluble inhibitors of the alternative complement pathway, factor H and the factor H-like protein 1. When exposed to nonimmune EDTA-plasma, the serum-resistant B. afzelii and B. burgdorferi sensu stricto strains bound factor H/factor H-like protein 1 to their surfaces. Assays with radiolabeled proteins showed that factor H bound strongly to the B. burgdorferi sensu stricto strain. To identify factor H ligands on the borrelial surface, we analyzed a panel of outer surface proteins of B. burgdorferi sensu stricto with the surface plasmon resonance technique. The outer surface lipoprotein OspE was identified as a specific ligand for factor H. Using recombinant constructs of factor H, the binding site for OspE was localized to the C-terminal short consensus repeat domains 15-20. Specific binding of factor H to B. burgdorferi sensu stricto OspE may help the pathogen to evade complement attack and phagocytosis.     

Impaired host defense to infection and Toll-like receptor 2-independent killing of Borrelia burgdorferi clinical isolates in TLR2-deficient C3H/HeJ mice

To investigate the role of Toll-like receptor 2 (TLR2)-mediated signaling in host innate defense and development of Lyme disease, the pathogenicity of Borrelia burgdorferi sensu stricto clinical isolates representing two distinct genotypes (RST1 and RST3A) was assessed in TLR2(-/-) C3H/HeJ mice. All TLR2(-/-) mice infected with a B. burgdorferi RST1 isolate developed severe arthritis. The numbers of spirochetes in heart, joint and ear biopsy specimens were significantly higher in TLR2(-/-) mice than in wild-type mice similarly infected as determined by real-time quantitative polymerase chain reaction. Interestingly, despite the higher spirochete levels in heart tissues, milder carditis was observed in TLR2(-/-) than in wild-type mice infected with this RST1 isolate (P=0.02). By contrast, no positive cultures were obtained from any of the blood and tissue specimens from TLR2(-/-) mice inoculated with two RST3A clinical isolates. The data suggest that there is impaired host innate defense against infection and TLR2-independent killing of B. burgdorferi clinical isolates in TLR2-deficient C3H/HeJ mice.     

Investigation of genotypes of Borrelia burgdorferi in Ixodes scapularis ticks collected during surveillance in Canada

The genetic diversity of Borrelia burgdorferi sensu stricto, the agent of Lyme disease in North America, has consequences for the performance of serological diagnostic tests and disease severity. To investigate B. burgdorferi diversity in Canada, where Lyme disease is emerging, bacterial DNA in 309 infected adult Ixodes scapularis ticks collected in surveillance was characterized by multilocus sequence typing (MLST) and analysis of outer surface protein C gene (ospC) alleles. Six ticks carried Borrelia miyamotoi, and one tick carried the novel species Borrelia kurtenbachii. 142 ticks carried B. burgdorferi sequence types (STs) previously described from the United States. Fifty-eight ticks carried B. burgdorferi of 1 of 19 novel or undescribed STs, which were single-, double-, or triple-locus variants of STs first described in the United States. Clonal complexes with founder STs from the United States were identified. Seventeen ospC alleles were identified in 309 B. burgdorferi-infected ticks. Positive and negative associations in the occurrence of different alleles in the same tick supported a hypothesis of multiple-niche polymorphism for B. burgdorferi in North America. Geographic analysis of STs and ospC alleles were consistent with south-to-north dispersion of infected ticks from U.S. sources on migratory birds. These observations suggest that the genetic diversity of B. burgdorferi in eastern and central Canada corresponds to that in the United States, but there was evidence for founder events skewing the diversity in emerging tick populations. Further studies are needed to investigate the significance of these observations for the performance of diagnostic tests and clinical presentation of Lyme disease in Canada.