High-prevalence Borrelia miyamotoi infection among [corrected] wild turkeys (Meleagris gallopavo) in Tennessee

Borrelia miyamotoi: A Comprehensive Review

Borrelia miyamotoi is an emerging tick-borne pathogen in the Northern Hemisphere and is the causative agent of Borrelia miyamotoi disease (BMD). Borrelia miyamotoi is vectored by the same hard-bodied ticks as Lyme disease Borrelia, yet phylogenetically groups with relapsing fever Borrelia, and thus, has been uniquely labeled a hard tick-borne relapsing fever Borrelia. Burgeoning research has uncovered new aspects of B. miyamotoi in human patients, nature, and the lab. Of particular interest are novel findings on disease pathology, prevalence, diagnostic methods, ecological maintenance, transmission, and genetic characteristics. Herein, we review recent literature on B. miyamotoi, discuss how findings adapt to current Borrelia doctrines, and briefly consider what remains unknown about B. miyamotoi.

Evaluation of Immunocompetent Mouse Models for Borrelia miyamotoi Infection

Borrelia miyamotoi is a relapsing fever spirochete that is harbored by Ixodes spp. ticks and is virtually uncharacterized, compared to other relapsing fever Borrelia vectored by Ornithodoros spp. ticks. There is not an immunocompetent mouse model for studying B. miyamotoi infection in vivo or for transmission in the vector-host cycle. Our goal was to evaluate B. miyamotoi infections in multiple mouse breeds/strains as a prelude to the ascertainment of the best experimental infection model. Two B. miyamotoi strains, namely, LB-2001 and CT13-2396, as well as three mouse models, namely, CD-1, C3H/HeJ, and BALB/c, were evaluated. We were unable to observe B. miyamotoi LB-2001 spirochetes in the blood via darkfield microscopy or to detect DNA via real-time PCR post needle inoculation in the CD-1 and C3H/HeJ mice. However, LB-2001 DNA was detected via real-time PCR in the blood of the BALB/c mice after needle inoculation, although spirochetes were not observed via microscopy. CD-1, C3H/HeJ, and BALB/c mice generated an antibody response to B. miyamotoi LB-2001 following needle inoculation, but established infections were not detected, and the I. scapularis larvae failed to acquire spirochetes from the exposed CD-1 mice. In contrast, B. miyamotoi CT13-2396 was visualized in the blood of the CD-1 and C3H/HeJ mice via darkfield microscopy and detected by real-time PCR post needle inoculation. Both mouse strains seroconverted. However, no established infection was detected in the mouse organs, and the I. scapularis larvae failed to acquire Borrelia after feeding on CT13-2396 exposed CD-1 or C3H/HeJ mice. These findings underscore the challenges in establishing an experimental B. miyamotoi infection model in immunocompetent laboratory mice. IMPORTANCE Borrelia miyamotoi is a causative agent of hard tick relapsing fever, was first identified in the early 1990s, and was characterized as a human pathogen in 2011. Unlike other relapsing fever Borrelia species, B. miyamotoi spread by means of Ixodes ticks. The relatively recent recognition of this human pathogen means that B. miyamotoi is virtually uncharacterized, compared to other Borrelia species. Currently there is no standard mouse-tick model with which to study the interactions of the pathogen within its vector and hosts. We evaluated two B. miyamotoi isolates and three immunocompetent mouse models to identify an appropriate model with which to study tick-host-pathogen interactions. With the increased prevalence of human exposure to Ixodes ticks, having an appropriate model with which to study B. miyamotoi will be critical for the future development of diagnostics and intervention strategies.

Transmission patterns of tick-borne pathogens among birds and rodents in a forested park in southeastern Canada

Ixodes scapularis ticks are expanding their range in parts of northeastern North America, bringing with them pathogens of public health concern. While rodents like the white-footed mouse, Peromyscus leucopus, are considered the primary reservoir of many emerging tick-borne pathogens, the contribution of birds, as alternative hosts and reservoirs, to local transmission cycles has not yet been firmly established. From 2016 to 2018, we collected host-seeking ticks and examined rodent and bird hosts for ticks at 48 sites in a park where blacklegged ticks are established in Quebec, Canada, in order to characterize the distribution of pathogens in ticks and mammalian and avian hosts. We found nearly one third of captured birds (n = 849) and 70% of small mammals (n = 694) were infested with I. scapularis. Five bird and three mammal species transmitted Borrelia burgdorferi to feeding larvae (n larvae tested = 2257) and we estimated that about one fifth of the B. burgdorferi-infected questing nymphs in the park acquired their infection from birds, the remaining being attributable to mice. Ground-foraging bird species were more parasitized than other birds, and species that inhabited open habitat were more frequently infested and were more likely to transmit B. burgdorferi to larval ticks feeding upon them. Female birds were more likely to transmit infection than males, without age differentiation, whereas in mice, adult males were more likely to transmit infection than juveniles and females. We also detected Borrelia miyamotoi in larvae collected from birds, and Anaplasma phagocytophilum from a larva collected from a white-footed mouse. This study highlights the importance of characterising the reservoir potential of alternative reservoir hosts and to quantify their contribution to transmission dynamics in different species assemblages. This information is key to identifying the most effective host-targeted risk mitigation actions.

Tick borne relapsing fever - a systematic review and analysis of the literature

Tick borne relapsing fever (TBRF) is a zoonosis caused by various Borrelia species transmitted to humans by both soft-bodied and (more recently recognized) hard-bodied ticks. In recent years, molecular diagnostic techniques have allowed to extend our knowledge on the global epidemiological picture of this neglected disease. Nevertheless, due to the patchy occurrence of the disease and the lack of large clinical studies, the knowledge on several clinical aspects of the disease remains limited. In order to shed light on some of these aspects, we have systematically reviewed the literature on TBRF and summarized the existing data on epidemiology and clinical aspects of the disease. Publications were identified by using a predefined search strategy on electronic databases and a subsequent review of the reference lists of the obtained publications. All publications reporting patients with a confirmed diagnosis of TBRF published in English, French, Italian, German, and Hungarian were included. Maps showing the epidemiogeographic mosaic of the different TBRF Borrelia species were compiled and data on clinical aspects of TBRF were analysed. The epidemiogeographic mosaic of TBRF is complex and still continues to evolve. Ticks harbouring TBRF Borrelia have been reported worldwide, with the exception of Antarctica and Australia. Although only molecular diagnostic methods allow for species identification, microscopy remains the diagnostic gold standard in most clinical settings. The most suggestive symptom in TBRF is the eponymous relapsing fever (present in 100% of the cases). Thrombocytopenia is the most suggestive laboratory finding in TBRF. Neurological complications are frequent in TBRF. Treatment is with beta-lactams, tetracyclines or macrolids. The risk of Jarisch-Herxheimer reaction (JHR) appears to be lower in TBRF (19.3%) compared to louse-borne relapsing fever (LBRF) (55.8%). The overall case fatality rate of TBRF (6.5%) and LBRF (4-10.2%) appears to not differ. Unlike LBRF, where perinatal fatalities are primarily attributable to abortion, TBRF-related perinatal fatalities appear to primarily affect newborns.

Effective control of the motile stages of Amblyomma americanum and reduced Ehrlichia spp. prevalence in adults via permethrin treatment of white-tailed deer in coastal Connecticut, USA

The lone star tick, Amblyomma americanum, is a common human-biting species whose range has been largely restricted to the southeastern United States, until recent detections of established populations on Long Island, New York and throughout coastal southern New England. We evaluated the effectiveness of topical treatment of 10 % permethrin delivered via 4-poster devices to white-tailed deer, Odocoileus virginianus, in the management of a newly discovered A. americanum population in Norwalk, Connecticut. Using a high-density deployment of one 4-poster device/12.7 ha, we were successful in significantly reducing densities of host-seeking adults (93 % reduction), nymphs (92 %), and larvae (96 %) from 2018 to 2020. We also documented a significant reduction (87 %) in parasitizing adults and nymphs on white-tailed deer from 2018 to 2019. The prevalence of Ehrlichia chaffeensis and Ehrlichia ewingii combined in host-seeking adults declined significantly from 47 % at the time the A. americanum population was discovered in 2017 to 7% in 2020. However, the prevalence in nymphs remained static (∼9%) throughout the study period. These data demonstrate that, when properly deployed in a density-dependent manner in terms of deer abundance, 4-poster devices can effectively manage parasitizing and host-seeking A. americanum populations and reduce the prevalence of two ehrlichial species of public health importance.

Spatial and temporal patterns of the emerging tick-borne pathogen Borrelia miyamotoi in blacklegged ticks (Ixodes scapularis) in New York

Borrelia miyamotoi, a bacterium that causes relapsing fever, is found in ixodid ticks throughout the northern hemisphere. The first cases of human infection with B. miyamotoi were identified in 2011. In the eastern USA, blacklegged ticks (Ixodes scapularis) become infected by feeding on an infected vertebrate host, or through transovarial transmission. We surveyed B. miyamotoi prevalence in ticks within forested habitats in Dutchess County, New York, and identified possible reservoir hosts. To assess spatial variation in infection, we collected questing nymphal ticks at > 150 sites. To assess temporal variation in infection, we collected questing nymphs for 8 years at a single study site. We collected questing larval ticks from nine plots to estimate the amount of transovarial transmission. To evaluate potential reservoir hosts, we captured 14 species of mammal and bird hosts naturally infested with larval blacklegged ticks and held these hosts in the laboratory until ticks fed to repletion and molted to nymphs. We determined infection for all ticks using quantitative polymerase chain reaction. The overall infection prevalence of questing nymphal ticks across all sites was ~ 1%, but prevalence at individual sites was as high as 9.1%. We detected no significant increase in infection through time. Only 0.4% of questing larval ticks were infected. Ticks having fed as larvae from short-tailed shrews, red squirrels, and opossums tended to have higher infection prevalence than did ticks having fed on other hosts. Further studies of the role of hosts in transmission are warranted. The locally high prevalence of B. miyamotoi in the New York/New England landscape suggests the importance of vigilance by health practitioners and the public.

Perpetuation of Borreliae

With one exception (epidemic relapsing fever), borreliae are obligately maintained in nature by ticks. Although some Borrelia spp. may be vertically transmitted to subsequent generations of ticks, most require amplification by a vertebrate host because inheritance is not stable. Enzootic cycles of borreliae have been found globally; those receiving the most attention from researchers are those whose vectors have some degree of anthropophily and, thus, cause zoonoses such as Lyme disease or relapsing fever. To some extent, our views on the synecology of the borreliae has been dominated by an applied focus, viz., analyses that seek to understand the elements of human risk for borreliosis. But, the elements of borrelial perpetuation do not necessarily bear upon risk, nor do our concepts of risk provide the best structure for analyzing perpetuation. We identify the major global themes for the perpetuation of borreliae, and summarize local variations on those themes, focusing on key literature to outline the factors that serve as the basis for the distribution and abundance of borreliae.

The Unexpected Holiday Souvenir: The Public Health Risk to UK Travellers from Ticks Acquired Overseas

Overseas travel to regions where ticks are found can increase travellers' exposure to ticks and pathogens that may be unfamiliar to medical professionals in their home countries. Previous studies have detailed non-native tick species removed from recently returned travellers, occasionally leading to travel-associated human cases of exotic tick-borne disease. There are 20 species of tick endemic to the UK, yet UK travellers can be exposed to many other non-native species whilst overseas. Here, we report ticks received by Public Health England's Tick Surveillance Scheme from humans with recent travel history between January 2006 and December 2018. Altogether, 16 tick species were received from people who had recently travelled overseas. Confirmed imports (acquired outside of the UK) were received from people who recently travelled to 22 countries. Possible imports (acquired abroad or within the UK) were received from people who had recently travelled to eight European countries. Species-specific literature reviews highlighted nine of the sixteen tick species are known to vector at least one tick-borne pathogen to humans in the country of acquisition, suggesting travellers exposed to ticks may be at risk of being bitten by a species that is a known vector, with implications for novel tick-borne disease transmission to travellers.

A new Borrelia on the block: Borrelia miyamotoi - a human health risk?

Background

Borrelia miyamotoi clusters phylogenetically among relapsing fever borreliae, but is transmitted by hard ticks. Recent recognition as a human pathogen has intensified research into its ecology and pathogenic potential.

Aims

We aimed to provide a timely critical integrative evaluation of our knowledge on B. miyamotoi, to assess its public health relevance and guide future research.

Methods

This narrative review used peer-reviewed literature in English from January 1994 to December 2018.

Results

Borrelia miyamotoi occurs in the world’s northern hemisphere where it co-circulates with B. burgdorferi sensu lato, which causes Lyme disease. The two borreliae have overlapping vertebrate and tick hosts. While ticks serve as vectors for both species, they are also reservoirs for B. miyamotoi. Three B. miyamotoi genotypes are described, but further diversity is being recognised. The lack of sufficient cultivable isolates and vertebrate models compromise investigation of human infection and its consequences. Our understanding mainly originates from limited case series. In these, human infections mostly present as influenza-like illness, with relapsing fever in sporadic cases and neurological disease reported in immunocompromised patients. Unspecific clinical presentation, also occasionally resulting from Lyme- or other co-infections, complicates diagnosis, likely contributing to under-reporting. Diagnostics mainly employ PCR and serology. Borrelia miyamotoi infections are treated with antimicrobials according to regimes used for Lyme disease.

Conclusions

With co-infection of tick-borne pathogens being commonplace, diagnostic improvements remain important. Developing in vivo models might allow more insight into human pathogenesis. Continued ecological and human case studies are key to better epidemiological understanding, guiding intervention strategies.

Surveillance for Borrelia spp. in Upland Game Birds in Pennsylvania, USA

The Borrelia genus contains two major clades, the Lyme borreliosis group, which includes the causative agents of Lyme disease/borreliosis (B. burgdorferi sensu stricto and other related B. burgdorferi sensu lato genospecies), and the relapsing fever borreliosis group (B. hermsii, B. turicatae, and B. parkeri). Other unclassified reptile- and echidna-associated Borrelia spp. (i.e., B. turcica and 'Candidatus Borrelia tachyglossi', respectively) do not belong in either of these two groups. In North America, Borrelia spp. from both of the major clades are important pathogens of veterinary and public health concern. Lyme disease is of particular interest because the incidence in the northeastern United States continues to increase in both dogs and humans. Birds have a potentially important role in the ecology of Borrelia species because they are hosts for numerous tick vectors and competent hosts for various Borrelia spp. Our goal was to investigate the prevalence of Borrelia spp. in four free-living species of upland game birds in Pennsylvania, USA including wild turkey (Meleagris gallopavo), ruffed grouse (Bonasa umbellus), ring-necked pheasants (Phasianus colchicus), and American woodcock (Scolopax minor). We tested 205 tissue samples (bone marrow and/or spleen samples) from 169 individuals for Borrelia using a flagellin gene (flab) nested PCR, which amplifies all Borrelia species. We detected Borrelia DNA in 12% (24/205) of samples, the highest prevalence was in wild turkeys (16%; 5/31), followed by ruffed grouse (13%; 16/126) and American woodcock (3%; 1/35). All pheasants (n = 13) were negative. We sequenced amplicons from all positive game birds and all were B. burgdorferi sensu stricto. Our results support previous work indicating that certain species of upland game birds are commonly infected with Borrelia species, but unlike previous studies, we did not find any relapsing fever borreliae.

Collaborative-Tick Surveillance Works: An Academic and Government Partnership for Tick Surveillance in the Southeastern United States (Acari: Ixodidae)

Tick surveillance provides essential information on distributions and encounter frequencies; it is a component of operational activities in public health practice. Our research objectives were a proof-of-concept for collaborative surveillance, which involved establishing an academic and government partnership to enhance tick surveillance efforts. The University of Tennessee (UT) collaborated with United States Department of Agriculture Forest Service, Southern Research Station Forest Inventory Analysis (FIA) in an Occupational Health and Safety partnership. UT provided FIA crews in the southeastern United States with vials containing 80% ethanol (July 2014-November 2017). Crew members were instructed to put all encountered ticks into the vials and return them to FIA headquarters. UT identified all submitted ticks to species and life stage, and screened Amblyomma americanum (L.) for Ehrlichia bacteria using a nested-PCR assay. From the 198 returned vials, 1,180 ticks were submitted, including A. americanum (90.51%; 202 larvae, 503 nymphs, and 363 adults), Dermacentor variabilis Say (7.12%; 1 nymph, 83 adults), Ixodes scapularis (Say) (1.61%; 19 adults), Amblyomma maculatum Koch (0.59%; 1 nymph, 6 adults), and Amblyomma cajennense (Fabricius) (0.17%; 1 nymph, 1 adult). FIA crews encountered A. americanum with Ehrlichia and collection information was used to generate baseline occurrence data of tick encounters. Results indicate that this collaborative-tick surveillance can be improved and used to generate useful data including pathogen detection, and because crews revisit these sites, changes in tick encounters can be monitored.

Simultaneous Occurrence of Borrelia miyamotoi, Borrelia burgdorferi Sensu Lato, Anaplasma phagocytophilum and Rickettsia helvetica in Ixodes ricinus Ticks in Urban Foci in Bratislava, Slovakia

BACKGROUND

Questing Ixodes ricinus ticks were collected in two urban parks (Železná studienka and Horský park) of the capital city of Slovakia, Bratislava, during two consecutive years in 2011 and 2012. A total of 932 ticks were analyzed for the presence of tick-borne agents: B. miyamotoi, B. burgdorferi s.l., A. phagocytophilum and R. helvetica.

RESULTS

PCR analysis confirmed the presence of all pathogens at both localities. The overall infection prevalence of B. miyamotoi, B. burgdorferi s.l., A. phagocytophilum and R. helvetica was 0.75, 13.2, 5.6 and 8.9%, respectively. B. burgdorferi s.l. positive samples were represented by six genospecies. The most frequent one was B. afzelii followed by B. garinii and B. valaisiana.

CONCLUSION

Our study confirms the presence of I. ricinus ticks and at least nine tick-borne bacterial agents in city forest parks, which are used for recreational purposes. Ordination analysis revealed significant differences in the composition of pathogens with respect to study site location, time of season and ambient temperature, despite the fact that both sites are located relatively close to one another within the city.

Tick-borne relapsing fever as a potential veterinary medical problem

Tick-borne relapsing fever (TBRF) caused by the bacteria Borrelia, is poorly documented in veterinary medicine. Given the widespread presence of the soft tick vectors - Ornithodoros and the recently discovered hard tick vectors, as well as their close association with animal hosts, it is highly likely that infection occurs, but is rarely reported to be of veterinary importance. Sporadic reports of canine infection, some being fatal through to probable cause of abortion in horses have been published. Some of these pathogens exist in regions where there are limited diagnostic facilities, hence, they are likely to be missed and their impact on productivity may be unquantified. Here we review available literatures on cases of TBRF in domestic and wild animals in order to show their potential veterinary medical impact. Future efforts using field and laboratory surveys are needed to determine pathogenesis, vector competence and distribution in animals, their impact on animal health and productivity as well as to prevent further spill to the human population, where it is already a public health problem in some parts of the world.

Prevalence and Geographic Distribution of Borrelia miyamotoi in Host-Seeking Ixodes pacificus (Acari: Ixodidae) Nymphs in Mendocino County, California

Borrelia miyamotoi is an increasingly recognized human pathogen transmitted by Ixodes ticks in the Northern Hemisphere. In North America, infection prevalences of B. miyamotoi are characteristically low (<10%) in Ixodes scapularis (Say; Acari: Ixodidae) and Ixodes pacificus (Cooley & Kohls; Acari: Ixodidae), both of which readily bite humans. We tested 3,255 host-seeking I. pacificus nymphs collected in 2004 from 79 sites throughout Mendocino County in north-coastal California for presence of B. miyamotoi. The collection sites represented a variety of forest types ranging from hot, dry oak woodlands in the southeast, to coastal redwoods in the west, and Ponderosa pine and Douglas fir-dominated areas in the northern part of the county. We found that B. miyamotoi was geographically widespread, but infected I. pacificus nymphs infrequently (cumulative prevalence of 1.4%). Infection prevalence was not significantly associated with geographic region or woodland type, and neither density of host-seeking nymphs, nor infection with Borrelia burgdorferi sensu stricto was associated with B. miyamotoi infection status in individual ticks. Because B. burgdorferi prevalence at the same sites was previously associated with woodland type and nymphal density, our results suggest that despite sharing a common vector, the primary modes of enzootic maintenance for the two pathogens are likely different.

Relapsing Fevers: Neglected Tick-Borne Diseases

Relapsing fever still remains a neglected disease and little is known on its reservoir, tick vector and physiopathology in the vertebrate host. The disease occurs in temperate as well as tropical countries. Relapsing fever borreliae are spirochaetes, members of the Borreliaceae family which also contain Lyme disease spirochaetes. They are mainly transmitted by Ornithodoros soft ticks, but some species are vectored by ixodid ticks. Traditionally a Borrelia species is associated with a specific vector in a particular geographical area. However, new species are regularly described, and taxonomical uncertainties deserve further investigations to better understand Borrelia vector/host adaptation. The medical importance of Borrelia miyamotoi, transmitted by Ixodes spp., has recently spawned new interest in this bacterial group. In this review, recent data on tick-host-pathogen interactions for tick-borne relapsing fevers is presented, with special focus on B. miyamotoi.

Distribution and host associations of ixodid ticks collected from wildlife in Florida, USA

A tick survey was conducted to document tick-host associations with Florida (USA) wildlife, and to determine the relative abundance and distribution of ixodid ticks throughout the state. The survey was conducted using collection kits distributed to licensed Florida hunters as well as the examination of archived specimens from ongoing state wildlife research programs. Collected tick samples were obtained from 66% of Florida counties and were collected from nine wildlife hosts, including black bear, bobcat, coyote, deer, gray fox, Florida panther, raccoon, swine, and wild turkey. In total, 4176 ticks were identified, of which 75% were Amblyomma americanum, 14% Ixodes scapularis, 8% A. maculatum, 3% Dermacentor variabilis, and < 1% were I. affinis and I. texanus. americanum, D. variabilis, and I. scapularis had the broadest host range, while A. maculatum, D. variabilis, and I. scapularis had the widest geographic distribution. While the survey data contribute to an understanding of tick-host associations in Florida, they also provide insight into the seasonal and geographic distribution of several important vector species in the southeastern USA.

Host Immune Evasion by Lyme and Relapsing Fever Borreliae: Findings to Lead Future Studies for Borrelia miyamotoi

The emerging pathogen, Borrelia miyamotoi, is a relapsing fever spirochete vectored by the same species of Ixodes ticks that carry the causative agents of Lyme disease in the US, Europe, and Asia. Symptoms caused by infection with B. miyamotoi are similar to a relapsing fever infection. However, B. miyamotoi has adapted to different vectors and reservoirs, which could result in unique physiology, including immune evasion mechanisms. Lyme Borrelia utilize a combination of Ixodes-produced inhibitors and native proteins [i.e., factor H-binding proteins (FHBPs)/complement regulator-acquiring surface proteins, p43, BBK32, BGA66, BGA71, CD59-like protein] to inhibit complement, while some relapsing fever spirochetes use C4b-binding protein and likely Ornithodoros-produced inhibitors. To evade the humoral response, Borrelia utilize antigenic variation of either outer surface proteins (Osps) and the Vmp-like sequences (Vls) system (Lyme borreliae) or variable membrane proteins (Vmps, relapsing fever borreliae). B. miyamotoi possesses putative FHBPs and antigenic variation of Vmps has been demonstrated. This review summarizes and compares the common mechanisms utilized by Lyme and relapsing fever spirochetes, as well as the current state of understanding immune evasion by B. miyamotoi.

Borrelia miyamotoi in vectors and hosts in The Netherlands

Ixodes ticks transmit Borrelia burgdorferi sensu lato (s.l.), the causative agent of Lyme borreliosis (LB). These tick species also transmit Borrelia miyamotoi, which was recently found to cause infections in humans. We were interested in the prevalence of B. miyamotoi infection in ticks and natural hosts in The Netherlands, and to what extent ticks are co-infected with B. burgdorferi. In addition, erythema migrans has been sporadically described in B. miyamotoi-infected patients, but these skin lesions might as well represent co-infections with B. burgdorferi s.l. We therefore investigated whether B. miyamotoi was present in LB-suspected skin lesions of patients referred to our tertiary Lyme disease clinic. 3360 questing Ixodes ricinus nymphs as well as spleen tissue of 74 rodents, 26 birds and 10 deer were tested by PCR for the presence of B. miyamotoi. Tick lysates were also tested for the presence of B. burgdorferi s.l. Next, we performed a PCR for B. miyamotoi in 31 biopsies from LB-suspected skin lesions in patients visiting our tertiary Lyme center. These biopsies had been initially tested for B. burgdorferi s.l. by PCR, and the skin lesions had been investigated by specialized dermatologists. Out of 3360 unfed (or questing) nymphs, 313 (9.3%) were infected with B. burgdorferi s.l., 70 (2.1%) were infected with B. miyamotoi, and 14 (0.4%) were co-infected with B. burgdorferi s.l. and B. miyamotoi. Co-infection of B. burgdorferi s.l. with B. miyamotoi occurred more often than expected from single infection prevalences (p=0.03). Both rodents (9%) and birds (8%) were found positive for B. miyamotoi by PCR, whereas the roe deer samples were negative. Out of 31 LB-suspected skin biopsies, 10 (32%) were positive for B. burgdorferi s.l. while none were positive for B. miyamotoi. The significant association of B. burgdorferi s.l. with B. miyamotoi in nymphs implies the existence of mutual reservoir hosts. Indeed, the presence of B. miyamotoi DNA indicates systemic infections in birds as well as rodents. However, their relative contributions to the enzootic cycle of B. miyamotoi requires further investigation. We could not retrospectively diagnose B. miyamotoi infection using biopsies of LB-suspected skin lesions, supporting the hypothesis that B. miyamotoi is not associated with LB-associated skin manifestations. However, this warrants further studies in larger sets of skin biopsies. A prospective study focused on acute febrile illness after a tick bite could provide insight into the incidence and clinical manifestations of B. miyamotoi infection in The Netherlands.

A quantitative synthesis of the role of birds in carrying ticks and tick-borne pathogens in North America

Birds play a central role in the ecology of tick-borne pathogens. They expand tick populations and pathogens across vast distances and serve as reservoirs that maintain and amplify transmission locally. Research into the role of birds for supporting ticks and tick-borne pathogens has largely been descriptive and focused in small areas. To expand inference beyond these studies, we conducted a quantitative review at the scale of North America to identify avian life history correlates of tick infestation and pathogen prevalence, calculate species-level indices of importance for carrying ticks, and identify research gaps limiting understanding of tick-borne pathogen transmission. Across studies, 78 of 162 bird species harbored ticks, yielding an infestation prevalence of 1981 of 38,929 birds (5.1 %). Avian foraging and migratory strategies interacted to influence infestation. Ground-foraging species, especially non-migratory ground foragers, were disproportionately likely to have high prevalence and intensity of tick infestation. Studies largely focused on Borrelia burgdorferi, the agent of Lyme disease, and non-migratory ground foragers were especially likely to carry B. burgdorferi-infected ticks, a finding that highlights the potential importance of resident birds in local pathogen transmission. Based on infestation indices, all "super-carrier" bird species were passerines. Vast interior areas of North America, many bird and tick species, and most tick-borne pathogens, remain understudied, and research is needed to address these gaps. More studies are needed that quantify tick host preferences, host competence, and spatiotemporal variation in pathogen prevalence and vector and host abundance. This information is crucial for predicting pathogen transmission dynamics under future global change.

Borrelia miyamotoi: A human tick-borne relapsing fever spirochete in Europe and its potential impact on public health

Borrelia miyamotoi is a tick-borne bacterium which has only recently been identified in Europe as a human pathogen causing relapsing fever and little is known about its local impact on human health. There are three types of B. miyamotoi: Asian (Siberian), European, and American. B. miyamotoi is transmitted by the same Ixodes ricinus-persulcatus species complex, which also transmits B. burgdorferi s.l., the Lyme borreliosis group. Both Borrelia groups are mostly maintained in natural rodent populations. The aim of this review is to summarize the available literature on B. miyamotoi, with the focus of attention falling on Europe, as well as to describe its presence in ticks, reservoir hosts, and humans and discuss its potential impact on public health.

Paired real-time PCR assays for detection of Borrelia miyamotoi in North American Ixodes scapularis and Ixodes pacificus (Acari: Ixodidae)

Borrelia miyamotoi is an emerging, tick-borne human pathogen. In North America, it is primarily associated with Ixodes scapularis and Ixodes pacificus, two species known to bite humans. Here we describe the development and evaluation of a pair of real-time TaqMan PCR assays designed to detect B. miyamotoi in North American ticks. We sought to achieve sensitivity to B. miyamotoi strains associated with ticks throughout North America, the full genetic diversity of which is unknown, by targeting sequences that are largely conserved between B. miyamotoi strains from the eastern United States and genetically distinct B. miyamotoi strains from Japan. The two assays target different loci on the B. miyamotoi chromosome and can be run side by side under identical cycling conditions. One of the assays also includes a tick DNA target that can be used to verify the integrity of tick-derived samples. Using both recombinant plasmid controls and genomic DNA from North American and Japanese strains, we determined that both assays reliably detect as few as 5 copies of the B. miyamotoi genome. We verified that neither detects B. burgdorferi, B. lonestari or B. turicatae. This sensitive and specific pair of assays successfully detected B. miyamotoi in naturally-infected, colony-reared nymphs and in field-collected I. scapularis and I. pacificus from the Northeast and the Pacific Northwest respectively. These assays will be useful in screening field-collected Ixodes spp. from varied regions of North America to assess the risk of human exposure to this emerging pathogen.

Prevalence of Borrelia miyamotoi in Ixodes ticks in Europe and the United States

Infection rates of Ixodes ticks with Borrelia miyamotoi in Europe and the United States vary greatly based upon location.

Borrelia miyamotoi, a relapsing fever-related spirochete transmitted by Ixodes ticks, has been recently shown to be a human pathogen. To characterize the prevalence of this organism in questing Ixodes ticks, we tested 2,754 ticks for a variety of tickborne pathogens by PCR and electrospray-ionization mass spectrometry. Ticks were collected from California, New York, Connecticut, Pennsylvania, and Indiana in the United States and from Germany and the Czech Republic in Europe from 2008 through 2012. In addition, an isolate from Japan was characterized. We found 3 distinct genotypes, 1 for North America, 1 for Europe, and 1 for Japan. We found B. miyamotoi infection in ticks in 16 of the 26 sites surveyed, with infection prevalence as high as 15.4%. These results show the widespread distribution of the pathogen, indicating an exposure risk to humans in areas where Ixodes ticks reside.

Borrelia miyamotoi: a widespread tick-borne relapsing fever spirochete

Borrelia miyamotoi is a relapsing fever spirochete that has only recently been identified as a human pathogen. Borrelia miyamotoi is genetically and ecologically distinct from Borrelia burgdorferi sensu lato, while both are present in Ixodes ticks. Over 50 patients with an acute febrile illness have been described with a B. miyamotoi infection, and two infected immunocompromised patients developed a meningoencephalitis. Seroprevalence studies indicate exposure in the general population and in specific risk groups, such as patients initially suspected of having human granulocytic anaplasmosis. Here, we review the available literature on B. miyamotoi, describing its presence in ticks, reservoir hosts, and humans, and discussing its potential impact on public health.

Remarkable diversity of tick or mammalian-associated Borreliae in the metropolitan San Francisco Bay Area, California

The diversity of Lyme disease (LD) and relapsing fever (RF)-group spirochetes in the metropolitan San Francisco Bay area in northern California is poorly understood. We tested Ixodes pacificus, I. spinipalpis, and small mammals for presence of borreliae in Alameda County in the eastern portion of San Francisco Bay between 2009 and 2012. Analyses of 218 Borrelia burgdorferi sensu lato (Bb sl) culture or DNA isolates recovered from host-seeking I. pacificus ticks revealed that the human pathogen Bb sensu stricto (hereinafter, B. burgdorferi) had the broadest habitat distribution followed by B. bissettii. Three other North American Bb sl spirochetes, B. americana, B. californiensis and B. genomospecies 2, also were detected at lower prevalence. OspC genotyping of the resultant 167 B. burgdorferi isolates revealed six ospC alleles (A, D, E3, F, H and K) in I. pacificus. A novel spirochete belonging to the Eurasian Bb sl complex, designated CA690, was found in a questing I. spinipalpis nymph. Borrelia miyamotoi, a relapsing-fever (RF) group spirochete recently implicated as a human pathogen, was detected in 24 I. pacificus. Three rodent species were infected with Bb sl: the fox squirrel (Sciurus niger) with B. burgdorferi, and the dusky-footed wood rat (Neotoma fuscipes) and roof rat (Rattus rattus) with B. bissettii. Another spirochete that clustered phylogenetically with the Spanish R57 Borrelia sp. in a clade distinct from both the LD and RF groups infected some of the roof rats. Together, eight borrelial genospecies were detected in ticks or small mammals from a single Californian county, two of which were related phylogenetically to European spirochetes.

Phylogeny of a relapsing fever Borrelia species transmitted by the hard tick Ixodes scapularis

The discovery of Borrelia species that were related to the agents of relapsing fever but were transmitted by hard ticks rather than soft ticks challenged previous taxonomies based largely on microbe-host specificities and geographic considerations. One of these newly-identified organisms is the Borrelia miyamotoi sensu lato strain LB-2001 from North America and transmitted by Ixodes scapularis. This or related strains have been identified as the cause of human disease, but comparatively little is known about their biology or genetics. Using recently acquired chromosome sequence of LB-2001 together with database sequences and additional sequences determined here, I carried out comparisons of the several species of Borrelia, including those in the two major clades: the relapsing fever group of species and the Lyme disease group of species. Phylogenetic inference at the species level was based on four data sets: whole chromosomes of ∼1Mb each, and concatenated sequences of 19 ribosomal protein genes, 3 conserved nucleic acid enzymes (rpoC, recC, and dnaE), and 4 contiguous genes for nucleotide salvage on a large plasmid. Analyses using neighbor-joining, maximum likelihood, and Bayesian methods were largely concordant for each of the trees. They showed that LB-2001 and related hard tick-associated organisms, like Borrelia lonestari, are deeply positioned within the RF group of species and that these organisms did not, as some earlier estimations had suggested, constitute a paraphyletic group. The analyses also provided further evidence that major changes in host ranges and life cycles, such as hard to soft ticks or vice versa, may not correlate well with overall sequence differences. The genetic differences between LB-2001 and B. miyamotoi sensu stricto justify provisional use of the "sensu lato" designation for LB-2001.

Are Apodemus spp. mice and Myodes glareolus reservoirs for Borrelia miyamotoi, Candidatus Neoehrlichia mikurensis, Rickettsia helvetica, R. monacensis and Anaplasma phagocytophilum?

In Europe, in addition to Borrelia burgdorferi sensu lato and tick-borne encephalitis (TBE) virus, other zoonotic pathogens, like B. miyamotoi, a species related to the relapsing fever spirochaetes, Candidatus Neoehrlichia mikurensis (N. mikurensis), Rickettsia helvetica, Rickettsia monacensis, and Anaplasma phagocytophilum have been reported in the ixodid tick Ixodes ricinus. No study was conducted to identify reservoir hosts for these pathogens. Here, we investigated the role played by wild rodents in the natural transmission cycle of B. miyamotoi, N. mikurensis, R. helvetica, R. monacensis, and A. phagocytophilum in Switzerland. In 2011 and 2012, small mammals were captured in an area where these pathogens occur in questing ticks. Ixodes ricinus ticks infesting captured small mammals were analysed after their moult by PCR followed by reverse line blot to detect the different pathogens. Xenodiagnostic larvae were used to evaluate the role of rodents as reservoirs and analysed after their moult. Most of the 108 captured rodents (95.4%) were infested by I. ricinus ticks; 4.9%, 3.9%, 24.0%, and 0% of the rodents were infested by Borrelia, N. mikurensis, Rickettsia spp., and A. phagocytophilum-infected larvae, respectively. Borrelia afzelii, B. miyamotoi, N. mikurensis, Rickettsia spp., and A. phagocytophilum were detected in 2.8%, 0.17%, 2.6%, 6.8%, and 0% of the ticks attached to rodents, respectively. Borrelia afzelii was transmitted by 4 rodents to 41.2% of the xenodiagnostic ticks, B. miyamotoi by 3 rodents to 23.8%, and N. mikurensis was transmitted by 6 rodents to 41.0% of the xenodiagnostic ticks. None of the tested rodent transmitted Rickettsia spp. or A. phagocytophilum to I. ricinus xenodiagnostic larvae. This study showed that rodents are reservoir hosts for B. miyamotoi and N. mikurensis in Europe.

Detection and genetic characterization of relapsing fever spirochete Borrelia miyamotoi in Estonian ticks

During the years 2008–2010 I. ricinus and I. persulcatus ticks were collected from 64 sites in mainland Estonia and on the island Saaremaa. Presence of B. miyamotoi was found in 0.9% (23/2622) of ticks. The prevalence in I. persulcatus and I. ricinus ticks differed significantly, 2.7% (15/561) and 0.4% (8/2061), respectively. The highest prevalence rates were in found South-Eastern Estonia in an area of I. persulcatus and I. ricinus sympatry and varied from 1.4% (1/73) to 2.8% (5/178). Co-infections with B. burgdorferi s.l. group spirochetes and tick-borne encephalitis virus were also revealed. Genetic characterization of partial 16S rRNA, p66 and glpQ genes demonstrated that Estonian sequences belong to two types of B. miyamotoi and cluster with sequences from Europe and the European part of Russia, as well as with sequences from Siberia, Asia and Japan, here designated as European and Asian types, respectively. Estonian sequences of the European type were obtained from I. ricinus ticks only, whereas the Asian type of B. miyamotoi was shown for both tick species in the sympatric regions.

Associations of passerine birds, rabbits, and ticks with Borrelia miyamotoi and Borrelia andersonii 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.