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

Investigating the importance of vertebrate hosts for Lyme disease ecology : a natural experiment presented by Lake Michigan islands at Sleeping Bear Dunes National Lakeshore

ABSTRACTINVESTIGATING THE IMPORTANCE OF VERTEBRATE HOSTS FOR LYME DISEASE ECOLOGY: A NATURAL EXPERIMENT PRESENTED BY LAKE MICHIGAN ISLANDS AT SLEEPING BEAR DUNES NATIONAL LAKESHORE ByJennifer Lois Sidge In eastern North America, Lyme disease is caused by the bacterium, Borrelia burgdorferi, and is transmitted by the blacklegged tick, Ixodes scapularis. In Michigan\u2019s Lower Peninsula, the blacklegged tick and the bacterium are invading from the southwest corner, northward along the Lake Michigan coast with the presumed leading edge at Sleeping Bear Dunes National Lakeshore (SLBE). How the tick spreads and becomes established is of great public health importance. White-tailed deer (Odocoileus virginianus) are believed to be the most important hosts for adult I. scapularis and critical for its spread and maintenance, but few opportunities exist to investigate tick and pathogen dynamics in their absence. Two Lake Michigan islands, at SLBE, one with deer and one without, presented this opportunity. The overall objective of this dissertation was to establish a baseline of abundance for the tick and pathogen on both islands and compare it to the ecologically diverse mainland, and assess the role of other mammals as alternative hosts for the adult stage of the tick in areas absent of deer. My hypothesis was that in locations devoid of deer, the blacklegged tick would not be established and/or would exist at much lower densities in comparison to areas with resident deer populations. Also, other medium-sized mammals would serve as hosts for the adult ticks that theoretically could support a tick population. In Chapter 1, I continued to track the invasion of the Lyme disease pathogen and vector at SLBE over a nine-year period. I found that there was a four year delay between the first detection of blacklegged ticks and the presence of B. burgdorferi and there was a trend illustrating an increase in I. scapularis and B. burgdorferi over time. At an additional site on SLBE\u2019s mainland, the tick and the pathogen were detected at the same time supporting the \u201cdual-invasion\u201d scenario of invasion, yet, this may have been a consequence of when sampling began. At recently-invaded Lyme disease areas, such as these two SLBE mainland locations, I found eastern chipmunks (Tamias striatus) to be an earlier indicator of the pathogen\u2019s presence in comparison to white-footed mice (Peromyscus leucopus). SLBE\u2019s two offshore islands, one with white-tailed deer and the other devoid, were the focus of Chapter 2 as a means to evaluate the success of mammalian hosts for maintaining I. scapularis in the absence of deer. I found that although the island with the deer had a greater density of ticks and greater B. burgdorferi infection prevalence, the island that was deer-free had all three life stages of the blacklegged tick and B. burgdorferi was present. Thus, alternative hosts for the adult tick, including snowshoe hares (Lepus americanus), passerine birds, and coyotes (Canis latrans), were captured and it was determined that coyotes were maintaining the established tick population on the island. Eastern chipmunks played a crucial role with maintaining the juvenile stages of the tick on the islands. Chapter 3 then compared SLBE\u2019s host-diverse mainland to the host-limited islands, testing the dilution and multiple niche polymorphism hypotheses. In order to test the dilution effect, the larval I. scapularis prevalence on white-footed mice between the two locations was compared. The proportion of mice infested with at least one I. scapularis larvae nor the larval burden on the mice supported the dilution hypothesis. However, on the islands and the mainland, more eastern chipmunks were captured than anticipated and this consequently reduced the larval burden on the mice in each community, thus, supporting the dilution effect at the location level. Host-seeking I. scapularis adult/nymphal infection prevalence and adult/nymphal density of infected ticks were greater on the host-limited islands, supporting the dilution hypothesis. However, B. burgdorferi IGS strain diversity was greater on the islands in comparison to the host-diverse mainland, which was unlike what was predicted by the multiple niche polymorphism hypothesis. Future studies to better estimate the island mammalian population sizes and diversity, in addition to comparing the B. burgdorferi island diversity to an area with a known long-established population of ticks would be advantageous to further our Lake Michigan island Lyme disease ecology knowledge. Also, given that SLBE is now most likely not at the leading edge of the Lyme disease invasion, future work should evaluate if the tick and bacterium have spread into neighboring counties.Thesis (Ph. D.)--Michigan State University. Comparative Medicine and Integrative Biology, 2016Includes bibliographical reference

The Contribution of Wildlife Hosts to the Rise of Ticks and Tick-Borne Diseases in North America

Abstract Wildlife vertebrate hosts are integral to enzootic cycles of tick-borne pathogens, and in some cases have played key roles in the recent rise of ticks and tick-borne diseases in North America. In this forum article, we highlight roles that wildlife hosts play in the maintenance and transmission of zoonotic, companion animal, livestock, and wildlife tick-borne pathogens. We begin by illustrating how wildlife contribute directly and indirectly to the increase and geographic expansion of ticks and their associated pathogens. Wildlife provide blood meals for tick growth and reproduction; serve as pathogen reservoirs; and can disperse ticks and pathogens—either through natural movement (e.g., avian migration) or through human-facilitated movement (e.g., wildlife translocations and trade). We then discuss opportunities to manage tick-borne disease through actions directed at wildlife hosts. To conclude, we highlight key gaps in our understanding of the ecology of tick–host interactions, emphasizing that wildlife host communities are themselves a very dynamic component of tick–pathogen–host systems and therefore complicate management of tick-borne diseases, and should be taken into account when considering host-targeted approaches. Effective management of wildlife to reduce tick-borne disease risk further requires consideration of the ‘human dimensions’ of wildlife management. This includes understanding the public’s diverse views and values about wildlife and wildlife impacts—including the perceived role of wildlife in fostering tick-borne diseases. Public health agencies should capitalize on the expertise of wildlife agencies when developing strategies to reduce tick-borne disease risks.</jats:p

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

Probable locally acquired babesia divergens-like infection in woman, Michigan, USA

We report an asplenic patient who was infected with Babesia divergens-like/MO-1. The clinical course was complicated by multiorgan failure that required intubation and dialysis. The patient recovered after an exchange transfusion and antimicrobial drug therapy. Physicians should be alert for additional cases, particularly in asplenic persons

Probable Locally Acquired Babesia divergens–Like Infection in Woman, Michigan, USA

We report an asplenic patient who was infected with Babesia divergens–like/MO-1. The clinical course was complicated by multiorgan failure that required intubation and dialysis. The patient recovered after an exchange transfusion and antimicrobial drug therapy. Physicians should be alert for additional cases, particularly in asplenic persons