| tick-borne relapsing fever: an interstate outbreak originating at grand canyon national park. | during the 1973 summer season, 27 employees and 35 overnight guests at the north rim, grand canyon national park, arizona, acquired febrile illnesses compatibel with relapsing fever. sixteen cases were confirmed by finding borrelia spirochetes in peripheral blood smears or inoculated swiss mice. retrospective surveys of 278 employees and 7247 guests at the park revealed that acquisition of illness was significantly associated with the persons sleeping in rustic log cabins and acquiring bites of ... | 1977 | 871120 |
| identification of the tick-borne relapsing fever spirochete borrelia hermsii by using a species-specific monoclonal antibody. | borrelia hermsii causes a relapsing fever in humans and is one of several species of tick-borne spirochetes known to occur in the western united states. spirochetes observed in the peripheral blood of patients acutely ill have been presumptively identified in the past by the geographic location of exposure and the probable species of tick vector. we describe a monoclonal antibody (h9826) that bound to the flagellar protein of b. hermsii but not to those of any of the other species tested, which ... | 1992 | 1572965 |
| ticks and borrelia: model systems for investigating pathogen-arthropod interactions. | blood-feeding arthropods transmit numerous types of infectious agent and parasite that have a tremendous impact on human health and mortality throughout the world. these vector-borne pathogens display a wide array of evolutionary patterns that allow them to infect and to be successfully transmitted by ticks, mites, and hematophagous insects. the vector's method of feeding, type of development, and host preference are also critical factors for the transfer of zoonotic agents from wild animal rese ... | 1996 | 8805079 |
| population structure of the relapsing fever spirochete borrelia hermsii as indicated by polymorphism of two multigene families that encode immunogenic outer surface lipoproteins. | the tick-borne relapsing fever spirochete borrelia hermsii evades the mammalian immune system by periodically switching expression among members of two multigene families that encode immunogenic, antigenically distinct outer surface proteins. the type strain, b. hermsii hs1, has at least 40 complete genes and pseudogenes that participate in this multiphasic antigenic variation. originally termed vmp (for variable major protein) genes, they have been reclassified as vsp (for variable small protei ... | 1998 | 9453591 |
| bloodstream- versus tick-associated variants of a relapsing fever bacterium. | the relapsing fever spirochete, borrelia hermsii, alternates infections between a mammal and a tick vector. whether the spirochete changes phenotypically in the different hosts was examined by allowing the tick vector ornithodoros hermsi to feed on mice infected with serotype 7 or serotype 8 of b. hermsii. upon infection of ticks, the spirochetal serotype-specific variable major proteins (vmps) 7 and 8 became undetectable and were replaced by vmp33. this switch from a bloodstream- to tick-associ ... | 1998 | 9632392 |
| tick-borne relapsing fever in british columbia, canada: first isolation of borrelia hermsii. | the spirochete that causes tick-borne relapsing fever, borrelia hermsii, was isolated in pure culture during 1995 and 1996 from three acutely ill human patients infected in southern british columbia, canada. the geographic area of exposure is a known focus of this disease dating back to 1930 when the first case was recognized in a human. analyses of plasmid dna, protein profiles, and reactivity with a species-specific monoclonal antibody identified the new isolates of spirochetes as b. hermsii, ... | 1998 | 9817862 |
| in vitro activities of the everninomicin sch 27899 and other newer antimicrobial agents against borrelia burgdorferi. | the in vitro activity of the everninomicin antibiotic sch 27899 against 17 isolates of borrelia spp. was investigated. mics ranged from 0.06 to 0.5 microg/ml. time-kill studies with the b31 strain of b. burgdorferi demonstrated >/=3-log10-unit killing after 72 h with concentrations representing four times the mic. the in vitro activity of four other newer antimicrobial agents, meropenem, cefepime, quinupristin-dalfopristin, and linezolid, was also tested against the b31 strain. meropenem was the ... | 1999 | 10390242 |
| the relapsing fever spirochete borrelia hermsii contains multiple, antigen-encoding circular plasmids that are homologous to the cp32 plasmids of lyme disease spirochetes. | borrelia hermsii, an agent of tick-borne relapsing fever, was found to contain multiple circular plasmids approximately 30 kb in size. sequencing of a dna library constructed from circular plasmid fragments enabled assembly of a composite dna sequence that is homologous to the cp32 plasmid family of the lyme disease spirochete, b. burgdorferi. analysis of another relapsing fever bacterium, b. parkeri, indicated that it contains linear homologs of the b. hermsii and b. burgdorferi cp32 plasmids. ... | 2000 | 10858201 |
| surface protein variation by expression site switching in the relapsing fever agent borrelia hermsii. | borrelia hermsii, an agent of relapsing fever, undergoes antigenic variation of serotype-specifying membrane proteins during mammalian infections. when b. hermsii is cultivated in broth medium, one serotype, 33, eventually predominates in the population. serotype 33 has also been found to be dominant in ticks but not in mammalian hosts. we investigated the biology and genetics of two independently derived clonal populations of serotype 33 of b. hermsii. both isolates infected immunodeficient mic ... | 2000 | 11083837 |
| antigen polymorphism in borrelia hermsii, a clonal pathogenic bacterium. | the relapsing fever spirochete, borrelia hermsii, escapes immune selection by alternating expression of surface lipoprotein alleles. the switch results from a duplicative transposition of one of several surface lipoprotein-encoding nucleotide sequences into the singular expression site. these nucleotide sequences constitute a large gene family whose diversity originated, in some cases, before the major divergences of borrelia species. we have examined the b. hermsii vsp subfamily of alleles, whi ... | 2001 | 11742066 |
| vector interactions and molecular adaptations of lyme disease and relapsing fever spirochetes associated with transmission by ticks. | pathogenic spirochetes in the genus borrelia are transmitted primarily by two families of ticks. the lyme disease spirochete, borrelia burgdorferi, is transmitted by the slow-feeding ixodid tick ixodes scapularis, whereas the relapsing fever spirochete, b. hermsii, is transmitted by ornithodoros hermsi, a fast-feeding argasid tick. lyme disease spirochetes are generally restricted to the midgut in unfed i. scapularis. when nymphal ticks feed, the bacteria pass through the hemocoel to the salivar ... | 2002 | 11897061 |
| glycerol-3-phosphate acquisition in spirochetes: distribution and biological activity of glycerophosphodiester phosphodiesterase (glpq) among borrelia species. | relapsing-fever spirochetes achieve high cell densities (>10(8)/ml) in their host's blood, while lyme disease spirochetes do not (<10(5)/ml). this striking contrast in pathogenicity of these two groups of bacteria suggests a fundamental difference in their ability to either exploit or survive in blood. borrelia hermsii, a tick-borne relapsing-fever spirochete, contains orthologs to glpq and glpt, genes that encode glycerophosphodiester phosphodiesterase (glpq) and glycerol-3-phosphate transporte ... | 2003 | 12562805 |
| 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. | 2003 | 14519254 |
| 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 b ... | 2004 | 15004063 |
| typing of borrelia relapsing fever group strains. | partial sequencing of the 16s-23s rdna intergenic spacer showed two to four genotypes each for borrelia hermsii and b. turicatae, both relapsing fever agents transmitted by argasid ticks, and for b. miyamotoi and b. lonestari, transmitted by ixodid ticks. field surveys of ixodes ticks in connecticut and sweden showed limited local diversity for b. miyamotoi. | 2004 | 15498172 |
| 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 ... | 2005 | 15845510 |
| 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 f ... | 2005 | 16081922 |
| 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 ident ... | 2005 | 16177341 |
| susceptibility of various species of rodents to the relapsing fever spirochete, borrelia hermsii. | in a study to determine susceptibility to borrelia hermsii of various rodents commonly found in or near places where human cases of relapsing fever occurred, chipmunks (eutamias amoenus), pine squirrels (tamiasciurus hudsonicus richardsoni), flying squirrels (glaucomys sabrinus), columbian ground squirrels (spermophilus columbianus columbianus), golden-mantled ground squirrels (s. lateralis tescorum), wood rats (neotoma cinerea cinerea), white-footed deer mice (peromyscus maniculatus), and meado ... | 1970 | 16557828 |
| purine salvage pathways among borrelia species. | genome sequencing projects on two relapsing fever spirochetes, borrelia hermsii and borrelia turicatae, revealed differences in genes involved in purine metabolism and salvage compared to those in the lyme disease spirochete borrelia burgdorferi. the relapsing fever spirochetes contained six open reading frames that are absent from the b. burgdorferi genome. these genes included those for hypoxanthine-guanine phosphoribosyltransferase (hpt), adenylosuccinate synthase (pura), adenylosuccinate lya ... | 2007 | 17502392 |
| 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 the ... | 2007 | 17552097 |
| 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 org ... | 2008 | 18755384 |
| oms38 is the first identified pore-forming protein in the outer membrane of relapsing fever spirochetes. | relapsing fever is a worldwide, endemic disease caused by several spirochetal species belonging to the genus borrelia. during the recurring fever peaks, borreliae proliferate remarkably quickly compared to the slow dissemination of lyme disease borrelia and therefore require efficient nutrient uptake from the blood of their hosts. this study describes the identification and characterization of the first relapsing fever porin, which is present in the outer membranes of b. duttonii, b. hermsii, b. ... | 2008 | 18757545 |
| identification of conserved antigens for early serodiagnosis of relapsing fever borrelia. | borrelia hermsii is a blood-borne pathogen transmitted by the argasid tick ornithodoros hermsi. since spirochaete clearance in mice is associated with an igm-mediated response, an immunoproteomic analysis was used to identify proteins reactive with igm. we report that igm from both mice and human patients infected with b. hermsii not only reacted with the previously identified variable membrane proteins but also identified candidate antigens including heat-shock proteins, an adhesin protein, abc ... | 2009 | 19443544 |
| tick-borne relapsing fever and borrelia hermsii, los angeles county, california, usa. | the primary cause of tick-borne relapsing fever in western north america is borrelia hermsii, a rodent-associated spirochete transmitted by the fast-feeding soft tick ornithodoros hermsi. we describe a patient who had an illness consistent with relapsing fever after exposure in the mountains near los angeles, california, usa. the patient's convalescent-phase serum was seropositive for b. hermsii but negative for several other vector-borne bacterial pathogens. investigations at the exposure site ... | 2009 | 19624916 |
| identical strains of borrelia hermsii in mammal and bird. | | 2009 | 19961706 |
| a novel surface antigen of relapsing fever spirochetes can discriminate between relapsing fever and lyme borreliosis. | in a previous immunoproteome analysis of borrelia hermsii, candidate antigens that bound igm antibodies from mice and patients infected with relapsing fever spirochetes were identified. one candidate that was identified is a hypothetical protein with a molecular mass of 57 kda that we have designated borrelia immunogenic protein a (bipa). this protein was further investigated as a potential diagnostic antigen for b. hermsii given that it is absent from the borrelia burgdorferi genome. the bipa l ... | 2010 | 20147497 |
| molecular characterization of the interaction of borrelia parkeri and borrelia turicatae with human complement regulators. | in north america, tick-borne relapsing fever is caused by the species borrelia hermsii, b. parkeri, and b. turicatae, which are transmitted to humans through the bite of the respective infected tick vectors. here we describe the identification and functional characterization of a surface lipoprotein of b. parkeri, designated bpca, that binds the human complement regulators factor h and factor h-related protein 1 and, simultaneously, the host protease plasminogen. in contrast, the homologous b. t ... | 2010 | 20231403 |
| phylogenetic analysis of a virulent borrelia species isolated from patients with relapsing fever. | multilocus sequence analysis (mlsa) was used to clarify the taxonomic status of a virulent borrelia organism previously isolated from patients with relapsing fever and from ticks in spain that is designated the spanish relapsing fever (srf) borrelia. this species has been used extensively in experimental infection models because of its continued virulence. seven genes were amplified to analyze the phylogenetic relationships among several spanish isolates of srf borrelia and other relapsing fever ... | 2010 | 20463158 |
| bloodmeal size and spirochete acquisition of ornithodoros hermsi (acari: argasidae) during feeding. | ornithodoros hermsi wheeler (acari: argasidae) is the vector of borrelia hermsii, the primary cause of tick-borne relapsing fever in north america. this tick is one of the smallest ornithodoros species involved with the biological transmission of spirochetes; yet, the amount of blood ingested while feeding is unknown. therefore, we determined the amount of blood o. hermsi ingested during a bloodmeal to establish its potential for spirochete acquisition while feeding on an infected host. ticks at ... | 2010 | 21175068 |
| Acquisition and subsequent transmission of Borrelia hermsii by the soft tick Ornithodoros hermsi. | Tick-borne relapsing fever is caused by spirochetes within the genus Borrelia. The hallmark of this disease is recurrent febrile episodes and high spirochete densities in mammalian blood resulting from immune evasion. Between episodes of spirochetemia when bacterial densities are low, it is unknown whether ticks can acquire the spirochetes, become colonized by the bacteria, and subsequently transmit the bacteria once they feed again. We addressed these questions by feeding ticks, Omnithodoros he ... | 2011 | 21845950 |
| detection of relapsing fever spirochetes (borrelia hermsii and borrelia coriaceae) in free-ranging mule deer (odocoileus hemionus) from nevada, united states. | abstract surveillance of mule deer (odocoileus hemionus, rafinesque, 1917) populations for tick-borne diseases has helped define the distribution of these pathogens and their subsequent risk of transmission to humans and domestic animals. we surveyed three mule deer herds across the state of nevada for infection with relapsing fever borrelia spp. spirochetes. bacterial prevalence varied by the county where deer were sampled but borrelia spirochetes were detected in 7.7% of all deer sampled. in ... | 2011 | 21995265 |
| cotransmission of divergent relapsing fever spirochetes by artificially infected ornithodoros hermsi. | the soft tick ornithodoros hermsi, which ranges in specific arboreal zones of western north america, acts as a vector for the relapsing fever spirochete borrelia hermsii. two genomic groups (genomic group i [ggi] and ggii) of b. hermsii are differentiated by multilocus sequence typing yet are codistributed in much of the vector's range. to test whether the tick vector can be infected via immersion, noninfected, colony-derived o. hermsi larvae were exposed to reduced-humidity conditions before im ... | 2011 | 21965393 |
| 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 sequenc ... | 2013 | 24252262 |
| development of genetic system to inactivate a borrelia turicatae surface protein selectively produced within the salivary glands of the arthropod vector. | borrelia turicatae, an agent of tick-borne relapsing fever, is an example of a pathogen that can adapt to disparate conditions found when colonizing the mammalian host and arthropod vector. however, little is known about the genetic factors necessary during the tick-mammalian infectious cycle, therefore we developed a genetic system to transform this species of spirochete. we also identified a plasmid gene that was up-regulated in vitro when b. turicatae was grown in conditions mimicking the tic ... | 2013 | 24205425 |
| what is the risk for exposure to vector-borne pathogens in united states national parks? | united states national parks attract > 275 million visitors annually and collectively present risk of exposure for staff and visitors to a wide range of arthropod vector species (most notably fleas, mosquitoes, and ticks) and their associated bacterial, protozoan, or viral pathogens. we assessed the current state of knowledge for risk of exposure to vector-borne pathogens in national parks through a review of relevant literature, including internal national park service documents and organismal ... | 2013 | 23540107 |
| large scale spatial risk and comparative prevalence of borrelia miyamotoi and borrelia burgdorferi sensu lato in ixodes pacificus. | borrelia miyamotoi is a newly described emerging pathogen transmitted to people by ixodes species ticks and found in temperate regions of north america, europe, and asia. there is limited understanding of large scale entomological risk patterns of b. miyamotoi and of borreila burgdorferi sensu stricto (ss), the agent of lyme disease, in western north america. in this study, b. miyamotoi, a relapsing fever spirochete, was detected in adult (n=70) and nymphal (n=36) ixodes pacificus ticks collecte ... | 2014 | 25333277 |
| inactivation of genes for antigenic variation in the relapsing fever spirochete borrelia hermsii reduces infectivity in mice and transmission by ticks. | borrelia hermsii, a causative agent of relapsing fever of humans in western north america, is maintained in enzootic cycles that include small mammals and the tick vector ornithodoros hermsi. in mammals, the spirochetes repeatedly evade the host's acquired immune response by undergoing antigenic variation of the variable major proteins (vmps) produced on their outer surface. this mechanism prolongs spirochete circulation in blood, which increases the potential for acquisition by fast-feeding tic ... | 2014 | 24699793 |
| transmission dynamics of borrelia turicatae from the arthropod vector. | with the global distribution, morbidity, and mortality associated with tick and louse-borne relapsing fever spirochetes, it is important to understand the dynamics of vector colonization by the bacteria and transmission to the host. tick-borne relapsing fever spirochetes are blood-borne pathogens transmitted through the saliva of soft ticks, yet little is known about the transmission capability of these pathogens during the relatively short bloodmeal. this study was therefore initiated to unders ... | 2014 | 24699275 |
| vaccination with the variable tick protein of the relapsing fever spirochete borrelia hermsii protects mice from infection by tick-bite. | tick-borne relapsing fevers of humans are caused by spirochetes that must adapt to both warm-blooded vertebrates and cold-blooded ticks. in western north america, most human cases of relapsing fever are caused by borrelia hermsii, which cycles in nature between its tick vector ornithodoros hermsi and small mammals such as tree squirrels and chipmunks. these spirochetes alter their outer surface by switching off one of the bloodstream-associated variable major proteins (vmps) they produce in mamm ... | 2015 | 26490040 |
| host associations and genomic diversity of borrelia hermsii in an endemic focus of tick-borne relapsing fever in western north america. | 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. | 2016 | 27832805 |
| assessment of the geographic distribution of ornithodoros turicata (argasidae): climate variation and host diversity. | ornithodoros turicata is a veterinary and medically important argasid tick that is recognized as a vector of the relapsing fever spirochete borrelia turicatae and african swine fever virus. historic collections of o. turicata have been recorded from latin america to the southern united states. however, the geographic distribution of this vector is poorly understood in relation to environmental variables, their hosts, and consequently the pathogens they transmit. | 2016 | 26829327 |
| alp, an arthropod-associated outer membrane protein of borrelia species that cause relapsing fever. | borrelia hermsii and other relapsing fever (rf) species are noted for their highly polymorphic surface antigens, the variable major proteins (vmp). less is known about other surface proteins of these pathogens in either their vertebrate reservoirs or arthropod vectors. to further characterize these proteins, we elicited antibodies against vmp-less cells, noted antibody reactions against whole cells and cell components, and then subjected selected antigens to mass spectroscopy for amino acid sequ ... | 2012 | 22354035 |
| borrelia hermsii acquisition order in superinfected ticks determines transmission efficiency. | multilocus sequence typing of borrelia hermsii isolates reveals its divergence into two major genomic groups (gg), but no differences in transmission efficiency or host pathogenicity are associated with these genotypes. to compare ggi and ggii in the tick-host infection cycle, we first determined if spirochetes from the two groups could superinfect the tick vector ornithodoros hermsi. we infected mice with isolates from each group and fed ticks sequentially on these mice. we then fed the infecte ... | 2013 | 23716615 |
| 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 te ... | 2013 | 23488454 |
| 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 mu ... | 2015 | 25625502 |
| scanning electron microscopy. | scanning electron microscopy (sem) remains distinct in its ability to allow topographical visualization of structures. key elements to consider for successful examination of biological specimens include appropriate preparative and imaging techniques. chemical processing induces structural artifacts during specimen preparation, and several factors need to be considered when selecting fixation protocols to reduce these effects while retaining structures of interest. particular care for proper dehy ... | 2012 | 22549162 |
| conspecific hyperparasitism: an alternative route for borrelia hermsii transmission by the tick ornithodoros hermsi. | ixodid and argasid ticks may hyperparasitize other individuals of their own species to acquire a blood meal, however most accounts are based on single observations and the behavior has rarely been studied. while maintaining laboratory colonies of ornithodoros species, we noticed that unfed ticks occasionally fed on other ticks that were feeding on mice, and unfed ticks parasitized engorged ticks when confined together in tubes. therefore, we investigated hyperparasitism by ornithodoros hermsi an ... | 2017 | 29174448 |
| colony formation in solid medium by the relapsing fever spirochetes borrelia hermsii and borrelia turicatae. | relapsing fever (rf) in north america is caused primarily by the spirochete borrelia hermsii and is associated with the bite of its tick vector ornithodoros hermsi. although this spirochete was known long before the discovery of the lyme disease (ld) spirochete, borrelia burgdorferi, basic methods to facilitate the study of b. hermsii have lagged behind. one important technique to expedite the study of the molecular biology and pathogenesis of b. hermsii would be a reliable method to grow and cl ... | 2017 | 29169853 |
| 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 moderat ... | 2017 | 29084219 |
| an atypical ornithodoros hermsi from utah (ixodoidea, argasidae). | | 1956 | 13332497 |
| laboratory and field studies on the biology of the relapsing fever tick vector (ornithodoros hermsi wheeler) in the high mountains of california. | | 1951 | 14829751 |