An interstate outbreak of tick-borne relapsing fever among vacationers at a Rocky Mountain cabin

Borrelia nietonii sp. nov.: Relapsing Fever Spirochetes Transmitted By the Tick Ornithodoros hermsi Designated Previously as Borrelia hermsii Genomic Group II

Background: The taxonomic status of the relapsing fever spirochete Borrelia hermsii in western North America was established in 1942 and based solely on its specific association with the soft tick vector Ornithodoros hermsi. Multilocus sequence typing (MLST) of the 16S rRNA, flaB, gyrB, glpQ, and 16S-23S rRNA intergenic spacer of B. hermsii isolates collected over many years from various geographic locations and biological sources identified two distinct clades designated previously as B. hermsii Genomic Group I (GGI) and Genomic Group II (GGII). To better assess the taxonomic relationship of these two genomic groups to each other and other species of Borrelia, DNA sequences of the entire linear chromosome were determined. Materials and Methods: Genomic DNA samples were prepared from 11 spirochete isolates grown in Barbour-Stoenner-Kelly-H medium. From these preparations, DNA sequences of the entire linear chromosome of two isolates of B. hermsii belonging to each genomic group and seven additional species were determined. Results: Chromosomal sequences of four isolates of B. hermsii contained 919,212 to 922,307 base pairs. DNA sequence identities between the two genomic groups of B. hermsii were 95.86-95.99%, which were more divergent than chromosomal sequences comparing Borrelia parkeri and Borrelia turicatae (97.13%), Borrelia recurrentis and Borrelia duttonii (97.07%), and Borrelia crocidurae and B. duttonii (97.09%). The 3' end of the chromosome of the two GGII isolates also contained a unique intact oppA gene absent from all other species examined. Conclusion: Previous MLST and the chromosomal sequences presented herein support the division of the B. hermsii species complex into two species, B. hermsii sensu stricto ( = GGI) and Borrelia nietonii sp. nov. ( = GGII). We name this unique relapsing fever spirochete in honor of our late friend and colleague Dr. Nathan Nieto for his outstanding contributions to our understanding of tick-borne relapsing fever.

A serological assay to detect and differentiate rodent exposure to soft tick and hard tick relapsing fever infections in the United States

Human cases of relapsing fever (RF) in North America are caused primarily by Borrelia hermsii and Borrelia turicatae, which are spread by argasid (soft) ticks, and by Borrelia miyamotoi, which is transmitted by ixodid (hard) ticks. In some regions of the United States, the ranges of the hard and soft tick RF species are known to overlap; in many areas, recorded ranges of RF spirochetes overlap with Lyme disease (LD) group Borrelia spirochetes. Identification of RF clusters or cases detected in unusual geographic localities might prompt public health agencies to investigate environmental exposures, enabling prevention of additional cases through locally targeted mitigation. However, exposure risks and mitigation strategies differ among hard and soft tick RF, prompting a need for additional diagnostic strategies that differentiate hard tick from soft tick RF. We evaluated the ability of new and previously described recombinant antigens in serological assays to differentiate among prior exposures in mice to LD, soft or hard tick RF spirochetes. We extracted whole-cell protein lysates from RF Borrelia cultures and synthesized six recombinant RF antigens (Borrelia immunogenic protein A (BipA) derived from four species of RF Borrelia, glycerophosphodiester phosphodiesterase (GlpQ), and Borrelia miyamotoi membrane antigen A (BmaA)) to detect reactivity in laboratory derived (Peromyscus sp. and Mus sp.) mouse serum infected with RF and LD Borrelia species. Among 44 Borrelia exposed mouse samples tested, all five mice exposed to LD spirochetes were correctly differentiated from the 39 mice exposed to RF Borrelia using the recombinant targets. Of the 39 mice exposed to RF spirochetes, 28 were accurately categorized to species of exposure (71%). Segregation among soft tick RF species (Borrelia hermsii, Borrelia parkeri and Borrelia turicatae) was inadequate (58%) owing to observed cross-reactivity among recombinant BipA protein targets. However, among the 28 samples accurately separated to species, all were accurately assigned to soft tick or hard tick RF type. Although not adequately specific to accurately categorize exposure to soft tick RF species, the recombinant BipA protein targets from soft and hard tick RF species show utility in accurately discriminating mouse exposures to LD or RF Borrelia, and accurately segregate hard tick from soft tick RF Borrelia exposure.

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.

First Record of Carios kelleyi (Acari: Ixodida: Argasidae) in New Jersey, United States and Implications for Public Health

The soft tick Carios kelleyi (Cooley and Kohls), a parasite of bats known to occur in at least 29 of the 48 conterminous U.S. states, is here reported from New Jersey for the first time, based on larvae collected from big brown bats, Eptesicus fuscus. Although thought to be widespread in North America, the ecology of C. kelleyi is not well understood, despite reports of this species feeding on humans and its consequent potential as a disease vector. The association of C. kelleyi with bat species that regularly roost in human-made structures, such as attics and barns, and recent isolations from this tick of pathogens capable of infecting humans, companion animals, and livestock underscore the need for further studies of these bat ectoparasites.

Ticks and Tick-Borne Diseases of Colorado, Including New State Records for Argas radiatus (Ixodida: Argasidae) and Ixodes brunneus (Ixodida: Ixodidae)

We report 28 species of ticks (Acari: Ixodida) from Colorado (CO). We include the soft ticks (Argasidae) Argas (Argas) cooleyi Kohls and Hoogstraal, Argas (Persicargas) radiatus Railliet, Carios (Alectorobius) concanensis (Cooley and Kohls), Carios (Alectorobius) kelleyi (Cooley and Kohls), Ornithodoros (Pavlovskyella) hermsi Wheeler et al., Ornithodoros (Pavlovskyella) parkeri Cooley, Ornithodoros (Pavlovskyella) turicata (Dugès), Otobius (Otobius) lagophilus Cooley and Kohls, and Otobius (Otobius) megnini (Dugès). We include the metastriate hard ticks (Ixodidae) Dermacentor (Americentor) albipictus (Packard), Dermacentor (Dermacentor) andersoni Stiles, Dermacentor (Dermacentor) parumapertus Neumann, Dermacentor (Dermacentor) variabilis (Say), Haemaphysalis (Aboimisalis) chordeilis (Packard), Haemaphysalis (Gonixodes) leporispalustris (Packard), and Rhipicephalus (Rhipicephalus) sanguineus Latreille. Prostriate hard ticks include Ixodes (Ixodiopsis) angustus Neumann, Ixodes (Phoeloioxdes) baergi Cooley and Kohls, Ixodes (Trichotoixodes) brunneus Koch, Ixodes (Scaphixodes) howelli Cooley and Kohls, Ixodes (Phoeloioxdes) kingi Bishopp, Ixodes (Phoeloioxdes) marmotae Cooley and Kohls, Ixodes (Ixodiopsis) ochotonae Gregson, Ixodes (Phoeloioxdes) sculptus Neumann, Ixodes (Ixodiopsis) soricis Gregson, Ixodes (Ixodes) spinipalpis Hadwen and Nuttall, Ixodes (Phoeloioxdes) texanus Banks, and Ixodes (Ixodiopsis) woodi Bishopp. Argas radiatus and Ixodes brunneus represent new state records. Review of collection reports revealed that inclusion of Ixodes (Multidentatus) auritulus (Neumann), Ixodes (Phoeloioxdes) cookei Packard, Ixodes (Phoeloioxdes) marxi Banks, and Ixodes (Ixodes) pacificus Cooley and Kohls is dubious or unconfirmed and, conversely, that C. concanensis and H. chordeilis have distributions that include CO. We list an additional five species occasionally detected and 13 exotic species intercepted in CO. Tick-host associations, geographical distributions, and medical/veterinary importance are included.

Identification of Host Bloodmeal Source in Ornithodoros turicata Dugès (Ixodida: Argasidae) Using DNA-Based and Stable Isotope-Based Techniques

The ecology and host feeding patterns of many soft ticks (Ixodida: Argasidae) remain poorly understood. To address soft tick-host feeding associations, we fed Ornithodoros turicata Dugès on multiple host species and evaluated quantitative PCR (qPCR) and stable isotope analyses to identify the vertebrate species used for the bloodmeal. The results showed that a qPCR with host-specific probes for the cytochrome b gene successfully identified bloodmeals from chicken (Gallus gallus L.), goat (Capra aegagrus hircus L), and swine (Sus scrofa domesticus) beyond 330 days post-feeding and through multiple molting. Also, qPCR-based bloodmeal analyses could detect multiple host species within individual ticks that fed upon more than one species. The stable isotope bloodmeal analyses were based on variation in the natural abundance of carbon (13C/12C) and nitrogen (15N/14N) isotopes in ticks fed on different hosts. When compared to reference isotope signatures, this method discerned unique δ13C and δ15N signatures in the ticks fed on each host taxa yet could not discern multiple host species from O. turicata that fed on more than one host species. Given the significance of soft tick-borne zoonoses and animal diseases, elucidating host feeding patterns from field-collected ticks using these methods may provide insight for an ecological basis to disease management.

Evaluating the risk of tick-borne relapsing fever among occupational cavers-Austin, TX, 2017

Tick-borne relapsing fever (TBRF) is a potentially serious spirochetal infection caused by certain species of Borrelia and acquired through the bite of Ornithodoros ticks. In 2017, Austin Public Health, Austin, TX, identified five cases of febrile illness among employees who worked in caves. A cross-sectional serosurvey and interview were conducted for 44 employees at eight organizations that conduct cave-related work. Antibodies against TBRF-causing Borrelia were detected in the serum of five participants, four of whom reported recent illness. Seropositive employees entered significantly more caves (Median 25 [SD: 15] versus Median 4 [SD: 16], p = 0.04) than seronegative employees. Six caves were entered more frequently by seropositive employees posing a potentially high risk. Several of these caves were in public use areas and were opened for tours. Education of area healthcare providers about TBRF and prevention recommendations for cavers and the public are advised.

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.

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.

Ecological niche modeling and distribution of Ornithodoros hermsi associated with tick-borne relapsing fever in western North America

Tick-borne relapsing fever in western North America is a zoonosis caused by the spirochete bacterium, Borrelia hermsii, which is transmitted by the bite of infected Ornithodoros hermsi ticks. The pathogen is maintained in natural cycles involving small rodent hosts such as chipmunks and tree squirrels, as well as the tick vector. In order for these ticks to establish sustained and viable populations, a narrow set of environmental parameters must exist, primarily moderate temperatures and moderate to high amounts of precipitation. Maximum Entropy Species Distribution Modeling (Maxent) was used to predict the species distribution of O. hermsi and B. hermsii through time and space based on current climatic trends and future projected climate changes. From this modeling process, we found that the projected current distributions of both the tick and spirochete align with known endemic foci for the disease. Further, global climate models predict a shift in the distribution of suitable habitat for the tick vector to higher elevations. Our predictions are useful for targeting surveillance efforts in areas of high risk in western North America, increasing the efficiency and accuracy of public health investigations and vector control efforts.

The model presented here provides valuable epidemiological information on tick-borne relapsing fever in western North America. The inference gleaned from these models represents areas where human infection with B. hermsii is likely to occur. The predicted distribution of O. hermsi and B. hermsii may allow health officials to decrease human disease burden by implementing targeted surveillance efforts, thus better utilizing resources. The models we created predict the current distribution of O. hermsi and B. hermsii, as well as the predicted distribution in 2050 under medium and high greenhouse gas (GHG) concentration trajectories. Understanding how the distribution of the pathogen and its vector expand or contract in response to GHG concentrations is necessary for understanding human risk of infection with this debilitating disease both now and in the future.

Tick-Borne Relapsing Fever in Southwest Colorado: A Case Report

BACKGROUND

Tick-borne relapsing fever (TBRF) is a zoonosis caused by spirochetes of the genus Borrelia. The zoonosis is endemic in higher-elevation coniferous forests of the western United States.

CASE REPORT

We discuss the case of a 44-year-old male residing in the San Juan Mountains of Western Colorado who presented with fever, myalgia, vomiting, and "violent chills" to an emergency department. Laboratory studies were notable for bandemia and thrombocytopenia with mild hyperbilirubinemia. Peripheral smear demonstrated multiple Borrelia spirochetes. The patient was treated with parenteral ceftriaxone and discharged with oral doxycycline therapy and recovered uneventfully. We discuss the clinical and epidemiological features of TBRF and the salient points for clinical diagnosis and management of this rare but important disease entity. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: TBRF is a rare and potentially life-threatening infectious process, which presents with nonspecific findings and often poses a diagnostic challenge. TBRF should be considered in the differential diagnosis for patients residing or vacationing in high-altitude forested areas in the western United States.

Host associations and genomic diversity of Borrelia hermsii in an endemic focus of tick-borne relapsing fever in western North America

Background

An unrecognized focus of tick-borne relapsing fever caused by Borrelia hermsii was identified in 2002 when five people became infected on Wild Horse Island in Flathead Lake, Montana. The terrestrial small mammal community on the island is composed primarily of pine squirrels (Tamiasciurus hudsonicus) and deer mice (Peromyscus maniculatus), neither of which was known as a natural host for the spirochete. Thus a 3-year study was performed to identify small mammals as hosts for B. hermsii.

Methods

Small mammals were captured alive on two island and three mainland sites, blood samples were collected and examined for spirochetes, and serological tests performed to detect anti-B. hermsii antibodies. Ornithodoros hermsi ticks were collected and fed on laboratory mice to assess infection. Genomic DNA samples from spirochetes isolated from infected mammals and ticks were analyzed by multilocus sequence typing.

Results

Eighteen pine squirrels and one deer mouse had detectable spirochetemias when captured, from which 12 isolates of B. hermsii were established. Most pine squirrels were seropositive, and the five species of sciurids combined had a significantly higher prevalence of seropositive animals than did the other six small mammal species captured. The greater diversity of small mammals on the mainland in contrast to the islands demonstrated that other species in addition to pine squirrels were also involved in the maintenance of B. hermsii at Flathead Lake. Ornithodoros hermsi ticks produced an additional 12 isolates of B. hermsii and multilocus sequence typing identified both genomic groups of B. hermsii described previously, and identified a new genomic subdivision. Experimental infections of deer mice with two strains of B. hermsii demonstrated that these animals were susceptible to infection with spirochetes belonging to Genomic Group II but not Genomic Group I.

Conclusions

Pine squirrels are the primary hosts for the maintenance of B. hermsii on the islands in Flathead Lake, however serological evidence showed that numerous additional species are also involved on the mainland. Future studies testing the susceptibility of several small mammal species to infection with different genetic types of B. hermsii will help define their role as hosts in this and other endemic foci.

Tick-Borne Relapsing Fever Outbreak Among a High School Football Team at an Outdoor Education Camping Trip, Arizona, 2014

During August 2014, five high school students who had attended an outdoor education camp were hospitalized with a febrile illness, prompting further investigation. Ten total cases of tick-borne relapsing fever (TBRF) were identified-six cases confirmed by culture or visualization of spirochetes on blood smear and four probable cases with compatible symptoms (attack rate: 23%). All patients had slept in the campsite's only cabin. Before the camp, a professional pest control company had rodent proofed the cabin, but no acaricides had been applied. Cabin inspection after the camp found rodents and Ornithodoros ticks, the vector of TBRF. Blood samples from a chipmunk trapped near the cabin and from patients contained Borrelia hermsii with identical gene sequences (100% over 630 base pairs). Health departments in TBRF endemic areas should consider educating cabin owners and pest control companies to apply acaricides during or following rodent proofing, because ticks that lack rodents for a blood meal might feed on humans.

Modeling Relapsing Disease Dynamics in a Host-Vector Community

Vector-borne diseases represent a threat to human and wildlife populations and mathematical models provide a means to understand and control epidemics involved in complex host-vector systems. The disease model studied here is a host-vector system with a relapsing class of host individuals, used to investigate tick-borne relapsing fever (TBRF). Equilibrium analysis is performed for models with increasing numbers of relapses and multiple hosts and the disease reproduction number, R₀, is generalized to establish relationships with parameters that would result in the elimination of the disease. We show that host relapses in a single competent host-vector system is needed to maintain an endemic state. We show that the addition of an incompetent second host with no relapses increases the number of relapses needed for maintaining the pathogen in the first competent host system. Further, coupling of the system with hosts of differing competencies will always reduce R₀, making it more difficult for the system to reach an endemic state.

An important development in the study of infectious diseases is the application of mathematical models to understand the interplay between various factors that determine epidemiological processes. Vector-borne diseases are additionally complex with interactions between multiple host and vector species. Understanding the transmission dynamics of vector-borne diseases is an important step towards controlling outbreaks and mitigating human infection risk. Identifying the biotic and abiotic interactions and mechanisms that may contribute to disease emergence, establishment and persistence is necessary for assessing current and future disease risk, as well as developing effective control strategies. Tick-borne relapsing fever (TBRF) is found around the world and is caused by several species of Borrelia spirochetes, which are vectored by soft ticks of the genus Ornithodoros. TBRF is a cryptic disease that still causes significant morbidity and mortality, especially in some African countries. Here, we develop and adapt a compartmentalized mathematical model (SIR) with a relapsing component to investigate the dynamics of TBRF.

Relapsing Fever Borreliae: A Global Review

Relapsing fever borreliae were notorious and feared infectious agents that earned their place in history through their devastating impact as causes of both epidemic and endemic infection. They are now considered more as an oddity, and their burden of infection is largely overshadowed by other infections such as malaria, which presents in a similar clinical way. Despite this, they remain the most common bacterial infection in some developing countries. Transmitted by soft ticks or lice, these fascinating spirochetes have evolved a myriad of mechanisms to survive within their diverse environments.

Tickborne relapsing fever, Bitterroot Valley, Montana, USA

In July 2013, a resident of the Bitterroot Valley in western Montana, USA, contracted tickborne relapsing fever caused by an infection with the spirochete Borrelia hermsii. The patient's travel history and activities before onset of illness indicated a possible exposure on his residential property on the eastern side of the valley. An onsite investigation of the potential exposure site found the vector, Ornithodoros hermsi ticks, and 1 chipmunk infected with spirochetes, which on the basis of multilocus sequence typing were identical to the spirochete isolated from the patient. Field studies in other locations found additional serologic evidence and an infected tick that demonstrated a wider distribution of spirochetes circulating among the small mammal populations. Our study demonstrates that this area of Montana represents a previously unrecognized focus of relapsing fever and poses a risk for persons of acquiring this tickborne disease.

Relapsing fever group Borrelia in Southern California rodents

Wild rodent reservoir host species were surveyed prospectively for infection with Borrelia hermsii, the causative agent of tick-borne relapsing fever in the western United States. Trapping occurred during the summer of 2009-2012 at field sites surrounding Big Bear Lake, CA, a region where human infection has been reported for many years. Using quantitative polymerase chain reaction (qPCR), we tested 207 rodents from 11 species and found chipmunks (Tamias spp.) and a woodrat (Neotoma macrotis) infected. Chipmunks represented the majority of captures at these sites. Sixteen of the 207 (7.7%; CI = 4.6-12.4) animals were qPCR-positive for Borrelia spp. associated with relapsing fever, and of those, we obtained bacterial DNA sequences from eight. The phylogram made from these sequences depict a clear association with B. hermsii genomic group I. In addition, we identified an infection with Borrelia coriaceae in a Tamias merriami, a potentially nonpathogenic member of the tick-borne relapsing fever group. Our findings support the hypothesis that chipmunk species play an important role in the maintenance of Borrelia species that cause tick-borne relapsing fever in the western United States, and therefore the risk of infection to people.

First isolation of the relapsing fever spirochete, Borrelia hermsii, from a domestic dog

In North America, tick-borne relapsing fever of humans is most frequently caused by infection with the spirochete Borrelia hermsii. Prior to our investigation, this spirochete was not known to infect dogs although another species, Borrelia turicatae, has been isolated from domestic canids in Florida and Texas. A clinically ill dog in Washington, USA, was spirochetemic upon examination. Spirochetes were isolated from the dog's serum and examined by PCR and multi-locus sequence typing. DNA sequences for 7 loci all typed the spirochete as B. hermsii and a member of genomic group II of this species. Therefore, companion dogs that reside in rustic cabins in higher elevation forests are at risk of infection with B. hermsii.

Serologic evidence for Borrelia hermsii infection in rodents on federally owned recreational areas in California

Tick-borne relapsing fever (TBRF) is endemic in mountainous regions of the western United States. In California, the principal agent is the spirochete Borrelia hermsii, which is transmitted by the argasid tick Ornithodoros hermsi. Humans are at risk of TBRF when infected ticks leave an abandoned rodent nest in quest of a blood meal. Rodents are the primary vertebrate hosts for B. hermsii. Sciurid rodents were collected from 23 sites in California between August, 2006, and September, 2008, and tested for serum antibodies to B. hermsii by immunoblot using a whole-cell sonicate and a specific antigen, glycerophosphodiester phosphodiesterase (GlpQ). Antibodies were detected in 20% of rodents; seroprevalence was highest (36%) in chipmunks (Tamias spp). Seroprevalence in chipmunks was highest in the Sierra Nevada (41%) and Mono (43%) ecoregions and between 1900 and 2300 meters elevation (43%). The serological studies described here are effective in implicating the primary vertebrate hosts involved in the maintenance of the ticks and spirochetes in regions endemic for TBRF.

Zoonotic infections among employees from Great Smoky Mountains and Rocky Mountain National Parks, 2008-2009

U.S. National Park Service employees may have prolonged exposure to wildlife and arthropods, placing them at increased risk of infection with endemic zoonoses. To evaluate possible zoonotic risks present at both Great Smoky Mountains (GRSM) and Rocky Mountain (ROMO) National Parks, we assessed park employees for baseline seroprevalence to specific zoonotic pathogens, followed by evaluation of incident infections over a 1-year study period. Park personnel showed evidence of prior infection with a variety of zoonotic agents, including California serogroup bunyaviruses (31.9%), Bartonella henselae (26.7%), spotted fever group rickettsiae (22.2%), Toxoplasma gondii (11.1%), Anaplasma phagocytophilum (8.1%), Brucella spp. (8.9%), flaviviruses (2.2%), and Bacillus anthracis (1.5%). Over a 1-year study period, we detected incident infections with leptospirosis (5.7%), B. henselae (5.7%), spotted fever group rickettsiae (1.5%), T. gondii (1.5%), B. anthracis (1.5%), and La Crosse virus (1.5%) in staff members at GRSM, and with spotted fever group rickettsiae (8.5%) and B. henselae (4.3%) in staff at ROMO. The risk of any incident infection was greater for employees who worked as resource managers (OR 7.4; 95% CI 1.4,37.5; p=0.02), and as law enforcement rangers/rescue crew (OR 6.5; 95% CI 1.1,36.5; p=0.03), relative to those who worked primarily in administration or management. The results of this study increase our understanding of the pathogens circulating within both parks, and can be used to inform the development of effective guidelines and interventions to increase visitor and staff awareness and help prevent exposure to zoonotic agents.

Genetic transformation of the relapsing fever spirochete Borrelia hermsii: stable integration and expression of green fluorescent protein from linear plasmid 200

Tick-borne relapsing fever (TBRF) is a spirochetal disease caused by at least 15 different Borrelia species. It is a serious human health concern in regions of endemicity throughout the world. Transmission to humans occurs through the bites of infected Ornithodoros ticks. In North America, the primary Borrelia species associated with human disease are B. hermsii and B. turicatae. Direct demonstration of the role of putative TBRF spirochete virulence factors in the disease process has been hindered by the lack of a genetic manipulation system and complete genome sequences. Expanding on recent developments in these areas, here we demonstrate the successful generation of a clone of B. hermsii YOR that constitutively produces green fluorescent protein (GFP) (B. hermsii YOR::kan gfp). This strain was generated through introduction of a kan-gfp cassette into a noncoding region of the 200-kb B. hermsii linear plasmid lp200. Genetic manipulation did not affect the growth rate or trigger the loss of native plasmids. B. hermsii YOR::kan gfp retained infectivity and elicited host seroconversion. Stable production of GFP was demonstrated both in vitro and in vivo. This study represents a significant step forward in the development of tools that can be employed to study the virulence mechanisms of TBRF spirochetes.

Tick talk: unusually severe case of tick-borne relapsing fever with acute respiratory distress syndrome--case report and review of the literature

Borrelia hermsii causes tick-borne relapsing fever (TBRF) in the Pacific Northwest. There are few reports of TBRF-associated acute respiratory distress syndrome. One such unusually severe case is described. Literature is reviewed including diagnosis, treatment, and prevention.

Warmer weather linked to tick attack and emergence of severe rickettsioses

The impact of climate on the vector behaviour of the worldwide dog tick Rhipicephalus sanguineus is a cause of concern. This tick is a vector for life-threatening organisms including Rickettsia rickettsii, the agent of Rocky Mountain spotted fever, R. conorii, the agent of Mediterranean spotted fever, and the ubiquitous emerging pathogen R. massiliae. A focus of spotted fever was investigated in France in May 2007. Blood and tissue samples from two patients were tested. An entomological survey was organised with the study of climatic conditions. An experimental model was designed to test the affinity of Rh. sanguineus for biting humans in variable temperature conditions. Serological and/or molecular tools confirmed that one patient was infected by R. conorii, whereas the other was infected by R. massiliae. Dense populations of Rh. sanguineus were found. They were infected with new genotypes of clonal populations of either R. conorii (24/133; 18%) or R. massiliae (13/133; 10%). April 2007 was the warmest since 1950, with summer-like temperatures. We show herein that the human affinity of Rh. sanguineus was increased in warmer temperatures. In addition to the originality of theses cases (ophthalmic involvements, the second reported case of R. massiliae infection), we provide evidence that this cluster of cases was related to a warming-mediated increase in the aggressiveness of Rh. sanguineus, leading to increased human attacks. From a global perspective, we predict that as a result of globalisation and warming, more pathogens transmitted by the brown dog tick may emerge in the future.

The impact of climate on the behaviour of the worldwide dog tick Rhipicephalus sanguineus is a cause of concern. This tick is a vector for life-threatening organisms including Rickettsia rickettsii, the agent of Rocky Mountain spotted fever, R. conorii, the agent of Mediterranean spotted fever, and the ubiquitous emerging pathogen R. massiliae. A focus of spotted fever was investigated in France in May 2007. One patient was found to be infected by R. conorii, whereas the other was infected by R. massiliae. Theses cases were original because of ophthalmic involvements, and the report of the second case of R. massiliae infection in the scientific literature. During an entomological survey, dense populations of Rh. sanguineus were found in the house where the patient had been bitten by ticks. Ticks were infected with either R. conorii or R. massiliae. Interestingly, April 2007 was the warmest since 1950, with summer-like temperatures. In this work, we show that the human affinity of Rh. sanguineus is increased in warmer temperatures, and provide evidence that this cluster of cases was related to a warming-mediated increase in the aggressiveness of Rh. sanguineus, leading to increased human attacks. From a global perspective, we predict that as a result of globalisation and warming, more pathogens transmitted by the brown dog tick may emerge in the future.

Tick-borne relapsing fever

Each year, many residents of and visitors to endemic regions of the western United States are exposed to the tick vectors of tick-borne relapsing fever (TBRF), Ornithodoros hermsi, Ornithodoros turicata, or Ornithodoros parkeri. This disease is remarkable because the human host is unaware of the tick bite, usually becomes very ill, may experience an exacerbation of symptoms rather than improvement shortly after beginning appropriate treatment, and, despite often high numbers of the etiologic organism in the blood, rarely dies as a result of the illness. Although relapsing fever is acquired in many parts of the world, this article focuses primarily on knowledge about TBRF in North America.

Identification of an antiparallel coiled-coil/loop domain required for ligand binding by the Borrelia hermsii FhbA protein: additional evidence for the role of FhbA in the host-pathogen interaction

Borrelia hermsii, an etiological agent of tick-borne relapsing fever in North America, binds host-derived serum proteins including factor H (FH), plasminogen, and an unidentified 60-kDa protein via its FhbA protein. Two distinct phylogenetic types of FhbA have been delineated (FhbA1 and FhbA2). These orthologs share a conserved C-terminal domain that contains two alpha helices with a high predictive probability of coiled-coil formation that are separated by a 14-amino-acid loop domain. Through site-directed mutagenesis, we have identified residues within these domains that influence the binding of both mouse and human FH, plasminogen, and/or the 60-kDa protein. To further investigate the involvement of FhbA in the host-pathogen interaction, strains that are either FhbA(+) (isolate YOR) or FhbA(-) (isolate REN) were tested for serum sensitivity. Significant differences were observed, with YOR and REN being serum resistant and serum sensitive (intermediate), respectively. To test the abilities of these strains to infect and persist in mice, mice were needle inoculated, and infectivity and persistence were then assessed. While both strains REN and YOR infected mice, only the FhbA(+) YOR strain persisted beyond day 4. Survival of the YOR isolate in blood correlated with the upregulation of the fhbA gene, as demonstrated by real-time reverse transcriptase PCR. These data advance our understanding of the unique interactions of FhbA with individual serum proteins and provide support for the hypothesis that FhbA is an important contributor to the pathogenesis of the relapsing fever spirochete B. hermsii.

Diversity and distribution of Borrelia hermsii

Borrelia hermsii is the most common cause of tickborne relapsing fever in North America. DNA sequences of the 16S-23S rDNA noncoding intergenic spacer (IGS) region were determined for 37 isolates of this spirochete. These sequences distinguished the 2 genomic groups of B. hermsii identified previously with other loci. Multiple IGS genotypes were identified among isolates from an island, which suggested that birds might play a role in dispersing these spirochetes in nature. In support of this theory, all stages of the tick vector Ornithodoros hermsi fed successfully on birds in the laboratory and advanced in their life cycle. B. hermsii produced a detectable spirochetemia in 1 chicken inoculated subcutaneously. Additional work is warranted to explore the role of birds as enzootic hosts for this relapsing fever spirochete.

Epidemiology of relapsing fever borreliosis in Europe

Tick-borne relapsing fever is a bacterial infection caused by spirochetes of the genus Borrelia. This zoonotic disease is transmitted to humans through the bite of soft ticks of the genus Ornithodoros. It is responsible for recurring fever access associated with spirochetemia. We present here an overview of tick-borne relapsing fever occurring in Europe, as well as of the potential threat to travellers.

Immunological and molecular analyses of the Borrelia hermsii factor H and factor H-like protein 1 binding protein, FhbA: demonstration of its utility as a diagnostic marker and epidemiological tool for tick-borne relapsing fever

It has been demonstrated that Borrelia hermsii, a causative agent of relapsing fever, produces a factor H (FH) and FH-like protein 1 (FHL-1) binding protein. The binding protein has been designated FhbA. To determine if FH/FHL-1 binding is widespread among B. hermsii isolates, a diverse panel of strains was tested for the FH/FHL-1 binding phenotype and FhbA production. Most isolates (23/24) produced FhbA and bound FH/FHL-1. Potential variation in FhbA among isolates was analyzed by DNA sequence analyses. Two genetically distinct FhbA types, designated fhbA1 and fhbA2, were delineated, and type-specific PCR primers were generated to allow for rapid differentiation. Pulsed-field gel electrophoresis and hybridization analyses demonstrated that all isolates that possess the gene carry it on a 200-kb linear plasmid (lp200), whereas isolates that lack the gene lack lp200 and instead carry an lp170. To determine if FhbA is antigenic during infection and to assess the specificity of the response, recombinant FhbA1 (rFhbA1) and rFhbA2 were screened with serum from infected mice and humans. FhbA was found to be expressed and antigenic and to elicit a potentially type-specific FhbA response. To localize the epitopes of FhbA1 and FhbA2, truncations were generated and screened with infection serum. The epitopes were determined to be conformationally defined. Collectively, these analyses indicate that FH/FHL-1 binding is a widespread virulence mechanism for B. hermsii and provide insight into the genetic and antigenic structure of FhbA. The data also have potential implications for understanding the epidemiology of relapsing fever in North America and can be applied to the future development of species-specific diagnostic tools.

Borrelia hermsii causing relapsing Fever and uveitis

PURPOSE

To describe a case of uveitis that is associated with Borrelia hermsii relapsing fever.

DESIGN

Interventional case report.

METHODS

A 12-year-old boy with two weeks of relapsing fevers 10 days after camping in remote eastern Oregon was examined. Borrelia hermsii immunoglobulin M and G levels were markedly elevated. Intravenous ceftriaxone, followed by four weeks of oral cephuroxime was administered, but the patient developed unilateral floaters and blurred vision in association with anterior and intermediate uveitis.

RESULTS

Doxycycline was administered for presumed residual infection. Four weeks later, the visual acuity had improved. The anterior chamber was quiet, and topical corticosteroid was tapered successfully.

CONCLUSION

Although rare, Borrelia hermsii should be included in the list of spirochetal diseases that are associated with uveitis.

Variable tick protein in two genomic groups of the relapsing fever spirochete Borrelia hermsii in western North America

Borrelia hermsii is the primary cause of tick-borne relapsing fever in North America. When its tick vector, Ornithodoros hermsi, acquires these spirochetes from the blood of an infected mammal, the bacteria switch their outer surface from one of many bloodstream variable major proteins (Vmps) to a unique protein, Vtp (Vsp33). Vtp may be critical for successful tick transmission of B. hermsii; however, the gene encoding this protein has been described previously in only one isolate. Here we identified and sequenced the vtp gene in 31 isolates of B. hermsii collected over 40 years from localities throughout much of its known geographic distribution. Seven major Vtp types were found. Little or no sequence variation existed within types, but between them significant variation was observed, similar to the pattern of diversity described for the outer surface protein C (OspC) gene in Lyme disease spirochetes. The pattern of sequence relatedness among the Vtp types was incongruent in two branches compared to two genomic groups identified among the isolates by multilocus sequence typing of the 16S rRNA, flaB, gyrB, and glpQ genes. Therefore, both horizontal transfer and recombination within and between the two genomic groups were responsible for some of the variation observed in the vtp gene. O. hermsi ticks were capable of transmitting spirochetes in the newly identified genomic group. Therefore, given the longevity of the tick vector and persistent infection of spirochetes in ticks, these arthropods rather than mammals may be the likely host where the exchange of spirochetal DNA occurs.

Phylogenetic analysis of the spirochetes Borrelia parkeri and Borrelia turicatae and the potential for tick-borne relapsing fever in Florida

Isolates of Borrelia turicatae, Borrelia parkeri, and the Florida canine borrelia (FCB) were examined to further phylogenetically characterize the identities of these spirochetes in the United States. DNA sequences of four chromosomal loci (the 16S rRNA gene, flaB, gyrB, and glpQ) were determined for eight isolates of B. turicatae and six isolates of B. parkeri, which grouped the spirochetes into two distinct but closely related taxa (>98% sequence identity) separate from Borrelia hermsii. The FCB was clearly separated with the group identified as B. turicatae, confirming this bacterium as a relapsing fever spirochete. Therefore, the potential for tick-borne relapsing fever in humans and other animals exists in Florida and future efforts are needed to determine the enzootic hosts and distribution of this spirochete in the southeastern United States. Analysis of plasmids demonstrated both linear and circular forms in B. turicatae but only linear plasmids in B. parkeri, which should be of interest to investigators concerned with plasmid diversity and evolution within this group of spirochetes.

Relapsing fever spirochetes contain chromosomal genes with unique direct tandemly repeated sequences

Genome sequencing of the relapsing fever spirochetes Borrelia hermsii and Borrelia turicatae identified three open reading frames (ORFs) on the chromosomes that contained internal, tandemly repeated amino acid sequences that were absent in the Lyme disease spirochete Borrelia burgdorferi. The predicted amino acid sequences of these genes (BH0209, BH0512, and BH0553) have hydrophobic N termini, indicating that these proteins may be secreted. B. hermsii transcribed the three ORFs in vitro, and the BH0512- and BH0553-encoded proteins (PBH-512 and PBH-553) were produced in vitro and in experimentally infected mice. PBH-512 and PBH-553 were on the spirochete's outer surface, and antiserum to these proteins reduced the adherence of B. hermsii to red blood cells. PCR analyses of 28 isolates of B. hermsii and 8 isolates of B. turicatae demonstrated polymorphism in each gene correlated with the number of repeats. Serum samples from relapsing fever patients reacted with recombinant PBH-512 and PBH-553, suggesting that these proteins are produced during human infection. These polymorphic proteins may be involved in the pathogenicity of these relapsing fever spirochetes and provide a mechanism for antigenic heterogeneity within their populations.

Threats to international travellers posed by tick-borne diseases

To date, 14 tick-borne diseases have been reported in international travellers, the majority of cases being Lyme borreliosis caused by Borrelia burgdorferi sensu lato in North America and Eurasia, African tick bite fever caused by Rickettsia africae in sub-Saharan Africa and eastern Caribbean, and Central European encephalitis caused by tick-borne encephalitis virus in Europe. The clinical presentation is frequently non-specific, and tick-borne diseases should always, in the absence of other likely diagnoses, be suspected in travellers with flu-like symptoms following a recent visit to tick-infested areas. Feasible microbiological diagnostic tests are widely unavailable, at least outside areas of endemicity where many infected travellers present. Empiric treatment with doxycycline should be considered in suspected cases of tick-borne bacterial diseases. Since ecotourism and adventure travel are increasingly popular worldwide, the incidence of travel-associated tick-borne diseases is likely to increase in the future.

Isolation and characterization of Borrelia hermsii associated with two foci of tick-borne relapsing fever in California

Relapsing fever, caused by the spirochete Borrelia hermsii and transmitted by the soft tick Ornithodoros hermsi, is endemic in many rural mountainous areas of California. Between 1996 and 1998, 12 cases of relapsing fever associated with two exposure sites in northern California were investigated. Follow-up at exposure sites included collection of soft ticks and serum specimens from sylvatic rodents. Attempts to cultivate spirochetes were made through inoculation of patient blood into mice and by feeding Ornithodoros ticks on mice. Three isolates of B. hermsii were recovered from two blood specimens and one pool of ticks. The protein and plasmid profiles of the three isolates were comparable to those of previous B. hermsii isolates from the western United States. Western immunoblotting of patient sera demonstrated an expanding immunologic response to antigens within four distinct molecular weight regions by 3 to 4 weeks postonset. Antibody to B. hermsii was detected in sera from 4 of 11 yellow-pine chipmunks (Tamias amoenus); no other rodent species collected were seropositive.

Tick-borne relapsing fever caused by Borrelia hermsii, Montana

Five persons contracted tick-borne relapsing fever after staying in a cabin in western Montana. Borrelia hermsii was isolated from the blood of two patients, and Ornithodoros hermsi ticks were collected from the cabin, the first demonstration of this bacterium and tick in Montana. Relapsing fever should be considered when patients who reside or have vacationed in western Montana exhibit a recurring febrile illness.

Tick-borne relapsing fever in North America

Relapsing fever is characterized by recurring episodes of fever and nonspecific symptoms (e.g., headache, myalgia, arthralgia, shaking chills, and abdominal complaints). The illness is caused by an infection from the Borrelia species (spirochetes) that may be acquired through the bite of an infected tick (Ornithodoros species) or contact with the hemolymph of an infected human body louse (Pediculus humanus). In North America, most cases have been acquired in the western United States, southern British Columbia, and few cases have been reported from Mexico. Most cases have been acquired from exposure to rustic tick-infested cabins and caves. This article reviews relapsing fever, especially tick-borne relapsing fever in North America.

Isolation and characterization of Borrelia parkeri in Ornithodoros parkeri (Ixodida: Argasidae) collected in Colorado

This study describes the identification of Borrelia parkeri spirochetes in Colorado. Two isolates of B. parkeri (6230 and 6232) were recovered from Ornithodoros parkeri Cooley ticks collected at an inactive prairie dog town in Moffat County. Both isolates were partially characterized by sequencing and subsequent parsimony and neighbor-joining analyses of appropriate regions of the 16S ribosomal RNA, flagellin and P66 genes. Analyses of the 16S gene sequences from the Colorado isolates indicated that they were more closely related to B. parkeri and B. tucatae than to B. hermsii or the other species of Borrelia investigated in this study. Additional analyses of amino acid sequences for flagellin and P66, however, clearly demonstrated that isolates 6230 and 6232 were most closely related to B. parkeri. The possible significance of B. parkeri as an agent of human disease is discussed.

Report on ticks collected in the Southeast and Mid-West regions of Brazil: analyzing the potential transmission of tick-borne pathogens to man

Specimens of ticks were collected in 1993, 1996, 1997, and 1998, mostly from wild and domestic animals in the Southeast and Mid-West regions of Brazil. Nine species of Amblyommidae were identified: Anocentor nitens, Amblyomma cajennense, Amblyomma ovale, Amblyomma fulvum, Amblyomma striatum, Amblyomma rotundatum, Boophilus microplus, Boophilus annulatus, and Rhipicephalus sanguineus. The potential of these tick species as transmitters of pathogens to man was analyzed. A Flaviviridade Flavivirus was isolated from Amblyomma cajennense specimens collected from a sick capybara (Hydrochaeris hydrochaeris). Amblyomma cajennense is the main transmitter of Rickettsia rickettsii (=R. rickettsi), the causative agent of spotted fever in Brazil. Wild mammals, mainly capybaras and deer, infested by ticks and living in close contact with cattle, horses and dogs, offer the risk of transmission of wild zoonosis to these domestic animals and to man.