The rare ospC allele L of Borrelia burgdorferi sensu stricto, commonly found among samples collected in a coastal plain area of the southeastern United States, is associated with ixodes affinis ticks and local rodent hosts Peromyscus gossypinus and Sigmodon hispidus

Ixodes spp. from Dogs and Cats in the United States: Diversity, Seasonality, and Prevalence of Borrelia burgdorferi and Anaplasma phagocytophilum

Ixodes spp. are commonly found on dogs and cats throughout the world. In the eastern United States, 16S rDNA sequence of Ixodes scapularis, the predominant species, reveals two clades-American and Southern. To confirm the species and clades of Ixodes spp. ticks submitted from pets, we examined ticks morphologically and evaluated 16S rDNA sequence from 500 ticks submitted from 253 dogs, 99 cats, 1 rabbit, and 1 ferret from 41 states. To estimate pathogen prevalence, flaB of Borrelia burgdorferi (Bb) sensu stricto and 16S rDNA of Anaplasma phagocytophilum (Ap) were amplified and sequenced. Most Ixodes spp. from the Northeast (n = 115/115; 100%) and the Midwest (n = 77/80; 96.3%) were I. scapularis, American clade. Borrelia spp. were identified in 34 of 192 (17.8%) and Ap in 5 of 192 (2.6%) I. scapularis. Two Ixodes cookei and one Ixodes texanus were identified from Ohio, Illinois, and Michigan. In contrast, 156 of 261 (59.8%) Ixodes spp. from the Southeast were I. scapularis, American clade; 86 of 261 (33.0%) were I. scapularis, Southern clade; 9 of 261 (3.4%) were Ixodes affinis; and 10 of 261 (3.8%) were I. cookei. Southern clade was significantly more common in Florida and less common in the upper South (p < 0.0001). One I. scapularis (1/242; 0.4%) from the Southeast (Kentucky) tested positive for Bb and 6 of 242 (2.5%) were positive for Ap. In the West, most (34/44; 77.3%) Ixodes spp. were Ixodes pacificus, with Ixodes angustus (n = 6) submitted from dogs in Alaska, Washington, and Oregon and Ixodes haerlei (n = 4) preliminarily identified from a dog in Montana. Pathogens were not detected in any ticks from the West. Although I. scapularis, American clade, predominated in the Northeast and Midwest, additional Ixodes spp. were found on dogs and cats in other regions and pathogens were less commonly detected. The role of less common Ixodes spp. as disease vectors, if any, warrants continued investigation.

Progress in the molecular diagnosis of Lyme disease

INTRODUCTION

Current laboratory testing of Lyme borreliosis mostly relies on serological methods with known limitations. Diagnostic modalities enabling direct detection of pathogen at the onset of the clinical signs could overcome some of the limitations. Molecular methods detecting borrelial DNA seem to be the ideal solution, although there are some aspects that need to be considered. Areas covered: This review represent summary and discussion of the published data obtained from literature searches from PubMed and The National Library of Medicine (USA) together with our own experience on molecular diagnosis of Lyme disease. Expert commentary: Molecular methods are promising and currently serve as supporting diagnostic testing in Lyme borreliosis. Since the field of molecular diagnostics is under rapid development, molecular testing could become an important diagnostic modality.

Invasive potential of Borrelia burgdorferi sensu stricto ospC type L strains increases the possible disease risk to humans in the regions of their distribution

BACKGROUND

Analysis of Borrelia burgdorferi ospC types from the southeastern U.S.A. supported the common belief that various ospC types are geographically restricted and host specific. Being widely distributed in the region, the southeastern population of B. burgdorferi is represented by a surprisingly small number of ospC types. Types B, G and H are dominant or common and are invasive, while scarce type L, restricted mostly to the southeastern U.S.A., is believed to rarely if ever cause human Lyme disease. OspC type B and L strains are represented in the region at the same rate, however their distribution among tick vectors and vertebrate hosts is unequal.

FINDINGS

Direct diagnostics was used to analyze the ability of B. burgdorferi ospC type L strains to disseminate into host tissues. Mice were infected by subcutaneous injections of B. burgdorferi strains of various ospC types with different invasive capability. Spirochete levels were examined in ear, heart, bladder and joint tissues. Noninfected I. ricinus larvae were fed on infected mice until repletion. Infection rates were determined in molted nymphs. Infected nymphs were then fed on naïve mice, and spirochete transmission from infected nymphs to mice was confirmed.

CONCLUSIONS

B. burgdorferi ospC type L strains from the southeastern U.S.A. have comparable potential to disseminate into host tissues as ospC types strains commonly associated with human Lyme disease in endemic European and North American regions. We found no difference in the invasive ability of ospC type B and L strains originated either from tick vectors or vertebrate hosts.

Divergence of Borrelia burgdorferi sensu lato spirochetes could be driven by the host: diversity of Borrelia strains isolated from ticks feeding on a single bird

BACKGROUND

The controversy surrounding the potential impact of birds in spirochete transmission dynamics and their capacity to serve as a reservoir has existed for a long time. The majority of analyzed bird species are able to infect larval ticks with Borrelia. Dispersal of infected ticks due to bird migration is a key to the establishment of new foci of Lyme borreliosis. The dynamics of infection in birds supports the mixing of different species, the horizontal exchange of genetic information, and appearance of recombinant genotypes.

METHODS

Four Borrelia burgdorferi sensu lato strains were cultured from Ixodes minor larvae and four strains were isolated from Ixodes minor nymphs collected from a single Carolina Wren (Thryothorus ludovicianus). A multilocus sequence analysis that included 16S rRNA, a 5S-23S intergenic spacer region, a 16S-23S internal transcribed spacer, flagellin, p66, and ospC separated 8 strains into 3 distinct groups. Additional multilocus sequence typing of 8 housekeeping genes, clpA, clpX, nifS, pepX, pyrG, recG, rplB, and uvrA was used to resolve the taxonomic status of bird-associated strains.

RESULTS

Results of analysis of 14 genes confirmed that the level of divergence among strains is significantly higher than what would be expected for strains within a single species. The presence of cross-species recombination was revealed: Borrelia burgdorferi sensu stricto housekeeping gene nifS was incorporated into homologous locus of strain, previously assigned to B. americana.

CONCLUSIONS

Genetically diverse Borrelia strains are often found within the same tick or same vertebrate host, presenting a wide opportunity for genetic exchange. We report the cross-species recombination that led to incorporation of a housekeeping gene from the B. burgdorferi sensu stricto strain into a homologous locus of another bird-associated strain. Our results support the hypothesis that recombination maintains a majority of sequence polymorphism within Borrelia populations because of the re-assortment of pre-existing sequence variants. Even if our findings of broad genetic diversity among 8 strains cultured from ticks that fed on a single bird could be the exception rather than the rule, they support the theory that the diversity and evolution of LB spirochetes is driven mainly by the host.

Detection of Borrelia burgdorferi sensu stricto ospC alleles associated with human lyme borreliosis worldwide in non-human-biting tick Ixodes affinis and rodent hosts in Southeastern United States

Comparative analysis of ospC genes from 127 Borrelia burgdorferi sensu stricto strains collected in European and North American regions where Lyme disease is endemic and where it is not endemic revealed a close relatedness of geographically distinct populations. ospC alleles A, B, and L were detected on both continents in vectors and hosts, including humans. Six ospC alleles, A, B, L, Q, R, and V, were prevalent in Europe; 4 of them were detected in samples of human origin. Ten ospC alleles, A, B, D, E3, F, G, H, H3, I3, and M, were identified in the far-western United States. Four ospC alleles, B, G, H, and L, were abundant in the southeastern United States. Here we present the first expanded analysis of ospC alleles of B. burgdorferi strains from the southeastern United States with respect to their relatedness to strains from other North American and European localities. We demonstrate that ospC genotypes commonly associated with human Lyme disease in European and North American regions where the disease is endemic were detected in B. burgdorferi strains isolated from the non-human-biting tick Ixodes affinis and rodent hosts in the southeastern United States. We discovered that some ospC alleles previously known only from Europe are widely distributed in the southeastern United States, a finding that confirms the hypothesis of transoceanic migration of Borrelia species.