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.200314519254
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 ...200516177341
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 ...201121845950
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 ...200919624916
susceptibility of various species of rodents to the relapsing fever spirochete, borrelia 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 ...197016557828
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 ...200415004063
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 ...19989632392
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 ...19968805079
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 ...19921572965
tickborne relapsing fever, bitterroot valley, montana, 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 ...201525625502
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 ...201323488454
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 ...201323716615
host associations and genomic diversity of borrelia hermsii in an endemic focus of tick-borne relapsing fever in western north 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.201627832805
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 ...201526490040
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 ...201424699793
first isolation of the relapsing fever spirochete, borrelia hermsii, from a domestic 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 ...201324252262
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 ...201121965393
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 ...201121995265
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 ...201021175068
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 ...200919443544
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 ...200717552097
Displaying items 1 - 21 of 21