Serologic Evidence for<i>Borrelia hermsii</i>Infection in Rodents on Federally Owned Recreational Areas in California

Relapsing fever spirochetes are tick- and louse-borne pathogens that primarily afflict those in impoverished countries. Historically the pathogens have had a significant impact on public health, yet currently they are often overlooked because of the nonspecific display of disease. In this review, we discuss aspects of relapsing fever (RF) spirochete pathogenesis including the: (1) clinical manifestation of disease; (2) ability to diagnose pathogen exposure; (3) the pathogen’s life cycle in the tick and mammal; and (4) ecological factors contributing to the maintenance of RF spirochetes in nature.

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“…), and pine squirrels ( Tamiasciurus spp.) are suitable hosts to varying degrees [ 48 , 49 , 68 , 70 , 72 , 73 , 74 ].…”

Section: Ecology Of Abrf In North Americamentioning

confidence: 99%

Tick-Borne Relapsing Fever Spirochetes in the Americas

López

Krishnavahjala

Garcia

et al. 2016

Veterinary Sciences

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“…The susceptibility experiments suggest these animals had been infected with GGII spirochetes however, our serological tests do not discriminate between the genomic groups of B. hermsii that caused the infection. In the only other large serological study investigating the presence of anti- B. hermsii antibodies in wild rodents, only 2 of 133 (1.5 %) deer mice tested in California were seropositive [29]. Yet, during a site investigation on Mt.…”

Section: Discussionmentioning

confidence: 99%

“…Yellow-pine chipmunks were far less abundant and rarely captured, yet two of only five individuals we tested were seropositive. This species extends south into the northeastern mountainous half of California [49], where two serological surveys found 36 % (4 of 11) and 47.2 % (34 of 72) of these animals seropositive with anti- B. hermsii antibodies [28, 29]. Subsequent to our field study at Flathead Lake, we found seropositive yellow-pine and red-tailed chipmunks in the Bitterroot Valley to the south in western Montana, and one yellow-pine chipmunk was infected with a GGI A B. hermsii [31].…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2016

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BackgroundAn 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. MethodsSmall 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.ResultsEighteen 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.ConclusionsPine 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.

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“…Unfed larvae, which feed on white-footed mice too but are not infected transovarially [ 88 ], and adult ticks that feed on much larger mammals like deer [ 47 ], play no direct role in the chain of infection [ 89 ]. In striking contrast, every active stage of O. hermsi has the potential to transmit B. hermsii when they feed on their hosts, primarily squirrels and chipmunks ( Tamiasciurus spp and Tamias spp) [ 90 , 91 ]. Larvae may become infected transovarially [ 92 , 93 ], although the frequency of this event needs further study.…”

Section: Discussionmentioning

confidence: 99%

Vaccination with the variable tick protein of the relapsing fever spirochete Borrelia hermsii protects mice from infection by tick-bite

et al. 2015

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BackgroundTick-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 mammals, and replacing it with the variable tick protein (Vtp) following their acquisition by ticks. Based on this reversion to Vtp in ticks, we produced experimental vaccines comprised on this protein and tested them in mice challenged by infected ticks.MethodsThe vtp gene from two isolates of B. hermsii that encoded antigenically distinct types of proteins were cloned, expressed, and the recombinant Vtp proteins were purified and used to vaccinate mice. Ornithodoros hermsi ticks that were infected with one of the two strains of B. hermsii from which the vtp gene originated were used to challenge mice that received one of the two Vtp vaccines or only adjuvant. Mice were then followed for infection and seroconversion.ResultsThe Vtp vaccines produced protective immune responses in mice challenged with O. hermsi ticks infected with B. hermsii. However, polymorphism in Vtp resulted in mice being protected only from the spirochete strain that produced the same Vtp used in the vaccine; mice challenged with spirochetes producing the antigenically different Vtp than the vaccine succumbed to infection.ConclusionsWe demonstrate that by having knowledge of the phenotypic changes made by B. hermsii as the spirochetes are acquired by ticks from infected mammals, an effective vaccine was developed that protected mice when challenged with infected ticks. However, the Vtp vaccines only protected mice from infection when challenged with that strain producing the identical Vtp. A vaccine containing multiple Vtp types may have promise as an oral vaccine for wild mammals if applied to geographic settings such as small islands where the mammal diversity is low and the Vtp types in the B. hermsii population are defined.

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Serologic Evidence forBorrelia hermsiiInfection in Rodents on Federally Owned Recreational Areas in California

Cited by 18 publications

References 17 publications

Tick-Borne Relapsing Fever Spirochetes in the Americas

Tick-Borne Relapsing Fever Spirochetes in the Americas

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

Vaccination with the variable tick protein of the relapsing fever spirochete Borrelia hermsii protects mice from infection by tick-bite

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