Associations of passerine birds, rabbits, and ticks with \u3cem\u3eBorrelia miyamotoi and Borrelia andersonii\u3c/em\u3e in Michigan, U.S.A.

Background Wild birds contribute to maintenance and dissemination of vectors and microbes, including those that impact human, domestic animal, and wildlife health. Here we elucidate roles of wild passerine birds, eastern cottontail rabbits (Sylvilagus floridanus), and Ixodes dentatus ticks in enzootic cycles of two spirochetes, Borrelia miyamotoi and B. andersonii in a region of Michigan where the zoonotic pathogen B. burgdorferi co-circulates. Methods Over a four-year period, wild birds (n = 19,631) and rabbits (n = 20) were inspected for tick presence and ear tissue was obtained from rabbits. Samples were tested for Borrelia spirochetes using nested PCR of the 16S-23S rRNA intergenic spacer region (IGS) and bidirectional DNA sequencing. Natural xenodiagnosis was used to implicate wildlife reservoirs. Results Ixodes dentatus, a tick that specializes on birds and rabbits and rarely bites humans, was the most common tick found, comprising 86.5% of the 12,432 ticks collected in the study. The relapsing fever group spirochete B. miyamotoi was documented for the first time in ticks removed from wild birds (0.7% minimum infection prevalence; MIP, in I. dentatus), and included two IGS strains. The majority of B. miyamotoi-positive ticks were removed from Northern Cardinals (Cardinalis cardinalis). Borrelia andersonii infected ticks removed from birds (1.6% MIP), ticks removed from rabbits (5.3% MIP), and rabbit ear biopsies (5%) comprised twelve novel IGS strains. Six species of wild birds were implicated as reservoirs for B. andersonii. Frequency of I. dentatus larval and nymphal co-feeding on birds was ten times greater than expected by chance. The relatively well-studied ecology of I. scapularis and the Lyme disease pathogen provides a context for understanding how the phenology of bird ticks may impact B. miyamotoi and B. andersonii prevalence and host associations. Conclusions Given the current invasion of I. scapularis, a human biting species that serves as a bridge vector for Borrelia spirochetes, human exposure to B. miyamotoi and B. andersonii in this region may increase. The presence of these spirochetes underscores the ecological complexity within which Borrelia organisms are maintained and the need for diagnostic tests to differentiate among these organisms

Diverse Borrelia burgdorferi Strains in a Bird-Tick Cryptic Cycle ▿ †

The blacklegged tick Ixodes scapularis is the primary vector of the most prevalent vector-borne zoonosis in North America, Lyme disease (LD). Enzootic maintenance of the pathogen Borrelia burgdorferi by I. scapularis and small mammals is well documented, whereas its “cryptic” maintenance by other specialist ticks and wildlife hosts remains largely unexplored because these ticks rarely bite humans. We quantified B. burgdorferi infection in a cryptic bird-rabbit-tick cycle. Furthermore, we explored the role of birds in maintaining and moving B. burgdorferi strains by comparing their genetic diversity in this cryptic cycle to that found in cycles vectored by I. scapularis. We examined birds, rabbits, and small mammals for ticks and infection over a 4-year period at a focal site in Michigan, 90 km east of a zone of I. scapularis invasion. We mist netted 19,631 birds that yielded 12,301 ticks, of which 86% were I. dentatus, a bird-rabbit specialist. No resident wildlife harbored I. scapularis, and yet 3.5% of bird-derived ticks, 3.6% of rabbit-derived ticks, and 20% of rabbit ear biopsy specimens were infected with B. burgdorferi. We identified 25 closely related B. burgdorferi strains using an rRNA gene intergenic spacer marker, the majority (68%) of which had not been reported previously. The presence of strains common to both cryptic and endemic cycles strongly implies bird-mediated dispersal. Given continued large-scale expansion of I. scapularis populations, we predict that its invasion into zones of cryptic transmission will allow for bridging of novel pathogen strains to humans and animals

Associations of passerine birds, rabbits, and ticks with <it>Borrelia miyamotoi and Borrelia andersonii</it> in Michigan, U.S.A.

<p>Abstract</p> <p>Background</p> <p>Wild birds contribute to maintenance and dissemination of vectors and microbes, including those that impact human, domestic animal, and wildlife health. Here we elucidate roles of wild passerine birds, eastern cottontail rabbits (<it>Sylvilagus floridanus</it>), and <it>Ixodes dentatus</it> ticks in enzootic cycles of two spirochetes, <it>Borrelia miyamotoi</it> and <it>B. andersonii</it> in a region of Michigan where the zoonotic pathogen <it>B. burgdorferi</it> co-circulates.</p> <p>Methods</p> <p>Over a four-year period, wild birds (n = 19,631) and rabbits (n = 20) were inspected for tick presence and ear tissue was obtained from rabbits. Samples were tested for <it>Borrelia</it> spirochetes using nested PCR of the 16S-23S rRNA intergenic spacer region (IGS) and bidirectional DNA sequencing. Natural xenodiagnosis was used to implicate wildlife reservoirs.</p> <p>Results</p> <p><it>Ixodes dentatus,</it> a tick that specializes on birds and rabbits and rarely bites humans, was the most common tick found, comprising 86.5% of the 12,432 ticks collected in the study. The relapsing fever group spirochete <it>B. miyamotoi</it> was documented for the first time in ticks removed from wild birds (0.7% minimum infection prevalence; MIP, in <it>I. dentatus</it>), and included two IGS strains. The majority of <it>B. miyamotoi</it>-positive ticks were removed from Northern Cardinals (<it>Cardinalis cardinalis</it>). <it>Borrelia andersonii</it> infected ticks removed from birds (1.6% MIP), ticks removed from rabbits (5.3% MIP), and rabbit ear biopsies (5%) comprised twelve novel IGS strains. Six species of wild birds were implicated as reservoirs for <it>B. andersonii.</it> Frequency of <it>I. dentatus</it> larval and nymphal co-feeding on birds was ten times greater than expected by chance. The relatively well-studied ecology of <it>I. scapularis</it> and the Lyme disease pathogen provides a context for understanding how the phenology of bird ticks may impact <it>B. miyamotoi</it> and <it>B. andersonii</it> prevalence and host associations.</p> <p>Conclusions</p> <p>Given the current invasion of <it>I. scapularis</it>, a human biting species that serves as a bridge vector for <it>Borrelia</it> spirochetes, human exposure to <it>B. miyamotoi</it> and <it>B. andersonii</it> in this region may increase. The presence of these spirochetes underscores the ecological complexity within which <it>Borrelia</it> organisms are maintained and the need for diagnostic tests to differentiate among these organisms.</p