Multispacer sequence typing relapsing fever Borreliae in Africa

Background

In Africa, relapsing fevers are neglected arthropod-borne infections caused by closely related Borrelia species. They cause mild to deadly undifferentiated fever particularly severe in pregnant women. Lack of a tool to genotype these Borrelia organisms limits knowledge regarding their reservoirs and their epidemiology.

Methodology/Principal Findings

Genome sequence analysis of Borrelia crocidurae, Borrelia duttonii and Borrelia recurrentis yielded 5 intergenic spacers scattered between 10 chromosomal genes that were incorporated into a multispacer sequence typing (MST) approach. Sequencing these spacers directly from human blood specimens previously found to be infected by B. recurrentis (30 specimens), B. duttonii (17 specimens) and B. crocidurae (13 specimens) resolved these 60 strains and the 3 type strains into 13 species-specific spacer types in the presence of negative controls. B. crocidurae comprised of 8 spacer types, B. duttonii of 3 spacer types and B. recurrentis of 2 spacer types.

Conclusions/Significance

Phylogenetic analyses of MST data suggested that B. duttonii, B. crocidurae and B. recurrentis are variants of a unique ancestral Borrelia species. MST proved to be a suitable approach for identifying and genotyping relapsing fever borreliae in Africa. It could be applied to both vectors and clinical specimens.     

Tick-borne relapsing fever Borreliosis,a major public health problem overlooked in Senegal

BackgroundTick-borne relapsing fever (TBRF) is the most common vector-borne bacterial disease in humans in West Africa. It is frequently clinically confused with malaria. Our study aims to determine, on a micro-geographic scale, the conditions for the maintenance and spread of TBRF in the Niakhar district of Senegal.Methodology/Principal findingsWe conducted clinical, entomological and animal reservoir investigations. Field surveys were carried out in order to investigate the presence of Ornithodoros sonrai vector ticks and to detect Borrelia spp. by qPCR using the 16S rRNA and glpQ genes, respectively. Micromammal trapping series were carried out inside homes and Borrelia infection was detected using brain tissue qPCR. Capillary blood samples from febrile patients were also tested for Borrelia using qPCR. More than 97% (40/41) of the villages surveyed were infested with O. sonrai ticks. The prevalence of Borrelia spp. infections in ticks was 13% (116/910), and over 73% (85/116) were positively confirmed as being Borrelia crocidurae. Borreliosis cases accounted for 12% (94/800) of episodes of fever and all age groups were infected, with children and young people between the ages of 8–14 and 22–28 being the most infected by the disease (16% and 18.4%). TBRF cases occurred in all seasons, with a peak in August. In two species of small rodents that were found to be infected (Arvicanthis niloticus, Mus musculus), the proportion of Borrelia infection was 17.5% (10/57), and the highest prevalence of infection (40.9%, 9/22) was observed in A. niloticus.Conclusion/SignificanceOur study indicates that TBRF is an endemic disease in the Niakhar district, where children and young people are the most infected. Arvicanthis niloticus and O. sonrai ticks are massively present and appear to be the main epidemiological reservoirs causing its extensive spread to humans.     

Isolation and genetic characterization of a relapsing fever spirochete isolated from Ornithodoros puertoricensis collected in central Panama

Tick-borne relapsing fever (TBRF) spirochetes are likely an overlooked cause of disease in Latin America. In Panama, the pathogens were first reported to cause human disease in the early 1900s. Recent collections of Ornithodoros puertoricensis from human dwellings in Panama prompted our interest to determine whether spirochetes still circulate in the country. Ornithodoros puertoricensis ticks were collected at field sites around the City of Panama. In the laboratory, the ticks were determined to be infected with TBRF spirochetes by transmission to mice, and we report the laboratory isolation and genetic characterization of a species of TBRF spirochete from Panama. Since this was the first isolation of a species of TBRF spirochete from Central America, we propose to designate the bacteria as Borrelia puertoricensis sp. nov. This is consistent with TBRF spirochete species nomenclature from North America that are designated after their tick vector. These findings warrant further investigations to assess the threat B. puertoricensis sp. nov. may impose on human health.     

P66 porins are present in both Lyme disease and relapsing fever spirochetes: A comparison of the biophysical properties of P66 porins from six Borrelia species

The genus Borrelia is the cause of the two human diseases: Lyme disease (LD) and relapsing fever (RF). Both LD and RF Borrelia species are obligate parasites and are dependent on nutrients provided by their hosts. The first step of nutrient uptake across the outer membrane of these Gram-negative bacteria is accomplished by water-filled channels, so-called porins. The knowledge of the porin composition in the outer membranes of the different pathogenic Borrelia species is limited. Only one porin has been described in relapsing fever spirochetes to date, whereas four porins are known to be present in Lyme disease agents. From these, the Borrelia burgdorferi outer membrane channel P66 is known to act as an adhesin and was well studied as a porin. To investigate if P66 porins are expressed and similarly capable of pore formation in other Borrelia causing Lyme disease or relapsing fever three LD species (B. burgdorferi, B. afzelii, B. garinii) and three RF species (B. duttonii, B. recurrentis and B. hermsii) were investigated for outer membrane proteins homologous to P66. A search in current published RF genomes, comprising the ones of B. duttonii, B. recurrentis and B. hermsii, indicated that they all contained P66 homologues. The P66 homologues of the six Borrelia species were purified to homogeneity and their pore-forming abilities as well as the biophysical properties of the pores were analyzed using the black lipid bilayer assay.     

New World relapsing fever Borrelia found in Ornithodoros porcinus ticks in central Tanzania

Ticks were collected from 8 houses in Mvumi Mission village, near Dodoma, Tanzania. All ticks were examined for Borrelia infestation by flagellin gene-based nested polymerase chain reaction. All houses were highly infested with ticks, and all ticks collected were of the Ornithodoros porcinus species. Fifty-one out of 120 ticks were infected with spirochetes, and a flagellin gene sequence comparison showed that most of the spirochetes belonged to Borrelia duttonii, which is the causative agent of tick-borne relapsing fever in East Africa. The rest of the spirochetes were quite different from B. duttonii and instead resembled the New World tick-borne relapsing fever borreliae. Phylogenetic analysis using 16S ribosomal RNA gene sequences also supported the interpretation that the spirochete was a Borrelia species distinct from previously described members of the genus.     

Molecular detection of pathogens from ectoparasites recovered from peri-domestic animals,and the first description of a Candidatus Midichloria sp. from Haemaphysalis wellingtoni from rural communities in Malaysia

Rural communities in Malaysia have been shown to be exposed to Coxiella, Borrelia and rickettsial infections in previous seroprevalence studies. Further research is necessary to identify the actual causative agents and the potential vectors of these infections. The arthropods parasitizing peri-domestic animals in these communities may serve as the vector in transmitting arthropod-borne and zoonotic agents to the humans.Molecular screening of bacterial and zoonotic pathogens from ticks and fleas collected from dogs, cats and chickens from six rural communities in Malaysia was undertaken. These communities were made up of mainly the indigenous people of Malaysia, known as the Orang Asli, as well as settlers in oil palm plantations. The presence of Coxiella burnetii, Borrelia, and rickettsial agents, including Rickettsia and Anaplasma, was investigated by performing polymerase chain reaction (PCR) and DNA sequencing.Candidatus Rickettsia senegalensis was detected in one out of eight pools of Ctenocephalides felis fleas. A relapsing fever group Borrelia sp. was identified from one of seven Haemaphysalis hystricis ticks tested. The results from the PCR screening for Anaplasma unexpectedly revealed the presence of Candidatus Midichloria sp., a potential tick endosymbiont, in two out of fourteen Haemaphysalis wellingtoni ticks tested. C. burnetii was not detected in any of the samples tested.The findings here provide evidence for the presence of potentially novel strains of rickettsial and borrelial agents in which their impact on public health risks among the rural communities in Malaysia merit further investigation. The detection of a potential endosymbiont of ticks also suggest that the presence of tick endosymbionts in the region is not fully explored.     

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.     

De novo RNA-seq and functional annotation of <Emphasis Type="Italic">Ornithonyssus bacoti</Emphasis>

Borrelia miyamotoi, a spirochete found in the hard tick Ixodes ricinus, is thought to cause relapsing fever. The disease caused by this bacterium can manifest with high fever, fatigue and other symptoms. It may also lead to central nervous system involvement with symptoms similar to meningoencephalitis. DNA from ticks from the greater Augsburg region in Germany was subjected to qPCR for Borrelia spp., followed by nested PCR and subsequent sequencing for species identification of the qPCR positive samples. From 112 ticks, 20 were found to be positive for Borrelia. The DNA sequenced showed 50% Borrelia afzelli, 15% Borrelia garinii, 5% Borrelia valaisiana and one sequence was identified as Borrelia miyamotoi. The positive identification of Borrelia miyamotoi is unlikely to be due to contamination. In conclusion, Borrelia miyamotoi has been found in a tick in the Augsburg region for the first time. This follows on from previous reports of a low incidence of this bacterium in southern Germany around Lake Constance and in the Munich region. This infectious agent should be taken into account when patients present with recurring fever or neurological symptoms which cannot be otherwise explained. Tick-borne relapsing fever should now be considered as a cause of such symptoms and medical professionals should contemplate differential Borrelia testing when presented with corresponding symptoms.     

Multiplex Real-Time PCR Diagnostic of Relapsing Fevers in Africa

Background

In Africa, relapsing fever borreliae are neglected arthropod-borne pathogens causing mild to deadly septicemia and miscarriage. The closely related Borrelia crocidurae, Borrelia duttonii, Borrelia recurrentis and Borrelia hispanica are rarely diagnosed at the species level, hampering refined epidemiological and clinical knowledge of the relapsing fevers. It would be hugely beneficial to have simultaneous detection and identification of Borrelia to species level directly from clinical samples.

Methodology/Principal Findings

We designed a multiplex real-time PCR protocol targeting the 16S rRNA gene detecting all four Borrelia, the glpQ gene specifically detecting B. crocidurae, the recN gene specifically detecting B. duttonii/B. recurrentis and the recC gene specifically detecting B. hispanica. Compared to combined 16S rRNA gene and flaB gene sequencing as the gold standard, multiplex real-time PCR analyses of 171 Borrelia-positive and 101 Borrelia-negative control blood specimens yielded 100% sensitivity and specificity for B. duttonii/B. recurrentis and B. hispanica and 99% sensitivity and specificity for B. crocidurae.

Conclusions/Significance

The multiplex real-time PCR developed in this study is a rapid technique for both molecular detection and speciation of relapsing fever borreliae from blood in Africa. It could be incorporated in point-of-care laboratory to confirm diagnosis and provide evidence of the burden of infection attributed to different species of known or potentially novel relapsing fever borreliae.     

The Epidemiology and Geographic Distribution of Relapsing Fever Borreliosis in West and North Africa,with a Review of the Ornithodoros erraticus Complex (Acari: Ixodida)

Background

Relapsing fever is the most frequent bacterial disease in Africa. Four main vector / pathogen complexes are classically recognized, with the louse Pediculus humanus acting as vector for B. recurrentis and the soft ticks Ornithodoros sonrai, O. erraticus and O. moubata acting as vectors for Borrelia crocidurae, B. hispanica and B. duttonii, respectively. Our aim was to investigate the epidemiology of the disease in West, North and Central Africa.

Methods And Findings

From 2002 to 2012, we conducted field surveys in 17 African countries and in Spain. We investigated the occurrence of Ornithodoros ticks in rodent burrows in 282 study sites. We collected 1,629 small mammals that may act as reservoir for Borrelia infections. Using molecular methods we studied genetic diversity among Ornithodoros ticks and Borrelia infections in ticks and small mammals. Of 9,870 burrows investigated, 1,196 (12.1%) were inhabited by Ornithodoros ticks. In West Africa, the southern and eastern limits of the vectors and Borrelia infections in ticks and small mammals were 13°N and 01°E, respectively. Molecular studies revealed the occurrence of nine different Ornithodoros species, including five species new for science, with six of them harboring Borrelia infections. Only B. crocidurae was found in West Africa and three Borrelia species were identified in North Africa: B. crocidurae, B. hispanica, and B. merionesi.

Conclusions

Borrelia Spirochetes responsible for relapsing fever in humans are highly prevalent both in Ornithodoros ticks and small mammals in North and West Africa but Ornithodoros ticks seem absent south of 13°N and small mammals are not infected in these regions. The number of Ornithodoros species acting as vector of relapsing fever is much higher than previously known.     

A phylogenomic and molecular marker based proposal for the division of the genus Borrelia into two genera: the emended genus Borrelia containing only the members of the relapsing fever Borrelia,and the genus Borreliella gen. nov. containing the members of the Lyme disease Borrelia (Borrelia burgdorferi sensu lato complex)

The genus Borrelia contains two groups of organisms: the causative agents of Lyme disease and their relatives and the causative agents of relapsing fever and their relatives. These two groups are morphologically indistinguishable and are difficult to distinguish biochemically. In this work, we have carried out detailed comparative genomic analyses on protein sequences from 38 Borrelia genomes to identify molecular markers in the forms of conserved signature inserts/deletions (CSIs) that are specifically found in the Borrelia homologues, and conserved signature proteins (CSPs) which are uniquely present in Borrelia species. Our analyses have identified 31 CSIs and 82 CSPs that are uniquely shared by all sequenced Borrelia species, providing molecular markers for this group of organisms. In addition, our work has identified 7 CSIs and 21 CSPs which are uniquely found in the Lyme disease Borrelia species and eight CSIs and four CSPs that are specific for members of the relapsing fever Borrelia group. Additionally, 38 other CSIs, in proteins which are uniquely found in Borrelia species, also distinguish these two groups of Borrelia. The identified CSIs and CSPs provide novel and highly specific molecular markers for identification and distinguishing between the Lyme disease Borrelia and the relapsing fever Borrelia species. We also report the results of average nucleotide identity (ANI) analysis on Borrelia genomes and phylogenetic analysis for these species based upon 16S rRNA sequences and concatenated sequences for 25 conserved proteins. These analyses also support the distinctness of the two Borrelia clades. On the basis of the identified molecular markers, the results from ANI and phylogenetic studies, and the distinct pathogenicity profiles and arthropod vectors used by different Borrelia spp. for their transmission, we are proposing a division of the genus Borrelia into two separate genera: an emended genus Borrelia, containing the causative agents of relapsing fever and a novel genus, Borreliella gen. nov., containing the causative agents of Lyme disease.     

MALDI-TOF Mass Spectrometry Detection of Pathogens in Vectors: The Borrelia crocidurae/Ornithodoros sonrai Paradigm

Background

In Africa, relapsing fever borreliae are neglected vector-borne pathogens that cause mild to deadly septicemia and miscarriage. Screening vectors for the presence of borreliae currently requires technically demanding, time- and resource-consuming molecular methods. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) has recently emerged as a tool for the rapid identification of vectors and the identification of cultured borreliae. We investigated whether MALDI-TOF-MS could detect relapsing fever borreliae directly in ticks.

Methodology/Principal Findings

As a first step, a Borrelia MALDI-TOF-MS database was created to house the newly determined Mean Spectrum Projections for four Lyme disease group and ten relapsing fever group reference borreliae. MALDI-TOF-MS yielded a unique protein profile for each of the 14 tested Borrelia species, with 100% reproducibility over 12 repeats. In a second proof-of-concept step, the Borrelia database and a custom software program that subtracts the uninfected O. sonrai profile were used to detect Borrelia crocidurae in 20 Ornithodoros sonrai ticks, including eight ticks that tested positive for B. crocidurae by PCR-sequencing. A B. crocidurae-specific pattern consisting of 3405, 5071, 5898, 7041, 8580 and 9757-m/z peaks was found in all B. crocidurae-infected ticks and not found in any of the un-infected ticks. In a final blind validation step, MALDI-TOF-MS exhibited 88.9% sensitivity and 93.75% specificity for the detection of B. crocidurae in 50 O. sonrai ticks, including 18 that tested positive for B. crocidurae by PCR-sequencing. MALDI-TOF-MS took 45 minutes to be completed.

Conclusions/Significance

After the development of an appropriate database, MALDI-TOF-MS can be used to identify tick species and the presence of relapsing fever borreliae in a single assay. This work paves the way for the use of MALDI-TOF-MS for the dual identification of vectors and vectorized pathogens.     

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.     

Diversity and distribution of the tick-borne relapsing fever spirochete Borrelia turicatae

Borrelia turicatae is a causative agent of tick-borne relapsing fever (TBRF) in the subtropics and tropics of the United States and Latin America. Historically, B. turicatae was thought to be maintained in enzootic cycles in rural areas. However, there is growing evidence that suggests the pathogen has established endemic foci in densely populated regions of Texas. With the growth of homelessness in the state and human activity in city parks, it was important to implement field collection efforts to identify areas where B. turicatae and its vector circulate. Between 2017 and 2020 we collected Ornithodoros turicata ticks in suburban and urban areas including public and private parks and recreational spaces. Ticks were fed on naïve mice and spirochetes were isolated from the blood. Multilocus sequence typing (MLST) was performed on eight newly obtained isolates and included previously reported sequences. The four chromosomal loci targeted for MLST were 16S ribosomal RNA (rrs), flagellin B (flaB), DNA gyrase B (gyrB), and the intergenic spacer (IGS). Given the complexity of Borrelia genomes, plasmid diversity was also evaluated. These studies indicate that the IGS locus segregates B. turicatae into four genomic types and plasmid diversity is extensive between isolates. Furthermore, B. turicatae and its vector have established endemic foci in parks and recreational areas in densely populated settings of Texas.     

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. recurrentis, and B. turicatae. The pore-forming protein was purified by hydroxyapatite chromatography and designated Oms38, for outer membrane-spanning protein of 38 kDa. Biophysical characterization of Oms38 was done by using the black lipid bilayer method, demonstrating that Oms38 forms small, water-filled channels of 80 pS in 1 M KCl that did not exhibit voltage-dependent closure. The Oms38 channel is slightly selective for anions and shows a ratio of permeability for cations over anions of 0.41 in KCl. Analysis of the deduced amino acid sequences demonstrated that Oms38 contains an N-terminal signal sequence which is processed under in vivo conditions. Oms38 is highly conserved within the four studied relapsing fever species, sharing an overall amino acid identity of 58% and with a strong indication for the presence of amphipathic β-sheets.     

Multiple and Diverse vsp and vlp Sequences in Borrelia miyamotoi,a Hard Tick-Borne Zoonotic Pathogen

Based on chromosome sequences, the human pathogen Borrelia miyamotoi phylogenetically clusters with species that cause relapsing fever. But atypically for relapsing fever agents, B. miyamotoi is transmitted not by soft ticks but by hard ticks, which also are vectors of Lyme disease Borrelia species. To further assess the relationships of B. miyamotoi to species that cause relapsing fever, I investigated extrachromosomal sequences of a North American strain with specific attention on plasmid-borne vsp and vlp genes, which are the underpinnings of antigenic variation during relapsing fever. For a hybrid approach to achieve assemblies that spanned more than one of the paralogous vsp and vlp genes, a database of short-reads from next-generation sequencing was supplemented with long-reads obtained with real-time DNA sequencing from single polymerase molecules. This yielded three contigs of 31, 16, and 11 kb, which each contained multiple and diverse sequences that were homologous to vsp and vlp genes of the relapsing fever agent B. hermsii. Two plasmid fragments had coding sequences for plasmid partition proteins that differed from each other from paralogous proteins for the megaplasmid and a small plasmid of B. miyamotoi. One of 4 vsp genes, vsp1, was present at two loci, one of which was downstream of a candiate prokaryotic promoter. A limited RNA-seq analysis of a population growing in the blood of mice indicated that of the 4 different vsp genes vsp1 was the one that was expressed. The findings indicate that B. miyamotoi has at least four types of plasmids, two or more of which bear vsp and vlp gene sequences that are as numerous and diverse as those of relapsing fever Borrelia. The database and insights from these findings provide a foundation for further investigations of the immune responses to this pathogen and of the capability of B. miyamotoi for antigenic variation.     

Mechanism of Borrelia immune evasion by FhbA-related proteins

Immune evasion facilitates survival of Borrelia, leading to infections like relapsing fever and Lyme disease. Important mechanism for complement evasion is acquisition of the main host complement inhibitor, factor H (FH). By determining the 2.2 Å crystal structure of Factor H binding protein A (FhbA) from Borrelia hermsii in complex with FH domains 19–20, combined with extensive mutagenesis, we identified the structural mechanism by which B. hermsii utilizes FhbA in immune evasion. Moreover, structure-guided sequence database analysis identified a new family of FhbA-related immune evasion molecules from Lyme disease and relapsing fever Borrelia. Conserved FH-binding mechanism within the FhbA-family was verified by analysis of a novel FH-binding protein from B. duttonii. By sequence analysis, we were able to group FH-binding proteins of Borrelia into four distinct phyletic types and identified novel putative FH-binding proteins. The conserved FH-binding mechanism of the FhbA-related proteins could aid in developing new approaches to inhibit virulence and complement resistance in Borrelia.     

Sequence Analysis and Serological Responses against Borrelia turicatae BipA,a Putative Species-Specific Antigen

Background

Relapsing fever spirochetes are global yet neglected pathogens causing recurrent febrile episodes, chills, nausea, vomiting, and pregnancy complications. Given these nonspecific clinical manifestations, improving diagnostic assays for relapsing fever spirochetes will allow for identification of endemic foci and expedite proper treatment. Previously, an antigen designated the Borrelia immunogenic protein A (BipA) was identified in the North American species Borrelia hermsii. Thus far, BipA appears unique to relapsing fever spirochetes. The antigen remains unidentified outside of these pathogens, while interspecies amino acid identity for BipA in relapsing fever spirochetes is only 24–36%. The current study investigated the immunogenicity of BipA in Borrelia turicatae, a species distributed in the southern United States and Latin America.

Methodology/Principal Findings

bipA was amplified from six isolates of Borrelia turicatae, and sequence analysis demonstrated that the gene is conserved among isolates. A tick transmission system was developed for B. turicatae in mice and a canine, two likely vertebrate hosts, which enabled the evaluation of serological responses against recombinant BipA (rBipA). These studies indicated that BipA is antigenic in both animal systems after infection by tick bite, yet serum antibodies failed to bind to B. hermsii rBipA at a detectable level. Moreover, mice continued to generate an antibody response against BipA one year after the initial infection, further demonstrating the protein''s potential toward identifying endemic foci for B. turicatae.

Conclusions/Significance

These initial studies support the hypothesis that BipA is a spirochete antigen unique to a relapsing fever Borrelia species, and could be used to improve efforts for identifying B. turicatae endemic regions.     

Serologic survey of Eptesicus fuscus from Georgia, U.S.A. for Rickettsia and Borrelia and laboratory transmission of a Rickettsia by bat ticks.

Bats and their ectoparasites are associated with bacterial agents of unknown pathogenicity. We tested sera from 56 Eptesicus fuscus from Georgia against Borrelia hermsii, Orientia tsutsugamushi, Rickettsia conorii, and Rickettsia rickettsii. We detected antibodies reactive against a relapsing fever Borrelia and spotted fever group Rickettsia in 3/56 and 1/56 bats, respectively. We attempted to culture Bartonella from the blood of these bats but were unsuccessful. In addition, we fed bat ticks, Carios kelleyi, infected with Rickettsia on a specific pathogen-free guinea pig. The guinea pig had a weak seroconversion to R. rickettsii with a peak titer of 1:32 starting on day 14. Rickettsia was not detected in any of the tissue samples from the guinea pig by molecular means. Our results indicate that E. fuscus is naturally exposed to both a spotted fever group Rickettsia and a relapsing fever group Borrelia. If these agents are transmitted by bat ticks, then people living in close proximity to bat ticks might be exposed.     

Endemic Foci of the Tick-Borne Relapsing Fever Spirochete Borrelia crocidurae in Mali,West Africa,and the Potential for Human Infection

Background

Tick-borne relapsing fever spirochetes are maintained in endemic foci that involve a diversity of small mammals and argasid ticks in the genus Ornithodoros. Most epidemiological studies of tick-borne relapsing fever in West Africa caused by Borrelia crocidurae have been conducted in Senegal. The risk for humans to acquire relapsing fever in Mali is uncertain, as only a few human cases have been identified. Given the high incidence of malaria in Mali, and the potential to confuse the clinical diagnosis of these two diseases, we initiated studies to determine if there were endemic foci of relapsing fever spirochetes that could pose a risk for human infection.

Methodology/Principal Findings

We investigated 20 villages across southern Mali for the presence of relapsing fever spirochetes. Small mammals were captured, thin blood smears were examined microscopically for spirochetes, and serum samples were tested for antibodies to relapsing fever spirochetes. Ornithodoros sonrai ticks were collected and examined for spirochetal infection. In total, 11.0% of the 663 rodents and 14.3% of the 63 shrews tested were seropositive and 2.2% of the animals had active spirochete infections when captured. In the Bandiagara region, the prevalence of infection was higher with 35% of the animals seropositive and 10% infected. Here also Ornithodoros sonrai were abundant and 17.3% of 278 individual ticks tested were infected with Borrelia crocidurae. Fifteen isolates of B. crocidurae were established and characterized by multi-locus sequence typing.

Conclusions/Significance

The potential for human tick-borne relapsing fever exists in many areas of southern Mali.