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.     

Human-pathogenic relapsing fever Borrelia found in bats from Central China phylogenetically clustered together with relapsing fever borreliae reported in the New World

Bats can harbor zoonotic pathogens causing emerging infectious diseases, but their status as hosts for bacteria is limited. We aimed to investigate the distribution, prevalence and genetic diversity of Borrelia in bats and bat ticks in Hubei Province, China, which will give us a better understanding of the risk of Borrelia infection posed by bats and their ticks. During 2018–2020, 403 bats were captured from caves in Hubei Province, China, 2 bats were PCR-positive for Borrelia. Sequence analysis of rrs, flaB and glpQ genes of positive samples showed 99.55%-100% similarity to Candidatus Borrelia fainii, a novel human-pathogenic relapsing fever Borrelia species recently reported in Zambia, Africa and Eastern China, which was clustered together with relapsing fever Borrelia species traditionally reported only in the New World. Multilocus sequence typing (MLST) and pairwise genetic distances further confirmed the Borrelia species in the bats from Central China as Candidatus Borrelia fainii. No Borrelia DNA was detected in ticks collected from bats. The detection of this human-pathogenic relapsing fever Borrelia in bats suggests a wide distribution of this novel relapsing fever Borrelia species in China, which may pose a threat to public health in China.     

Disease Risk & Landscape Attributes of Tick-Borne Borrelia Pathogens in the San Francisco Bay Area,California

Habitat heterogeneity influences pathogen ecology by affecting vector abundance and the reservoir host communities. We investigated spatial patterns of disease risk for two human pathogens in the Borrelia genus–B. burgdorferi and B. miyamotoi–that are transmitted by the western black-legged tick, Ixodes pacificus. We collected ticks (349 nymphs, 273 adults) at 20 sites in the San Francisco Bay Area, California, USA. Tick abundance, pathogen prevalence and density of infected nymphs varied widely across sites and habitat type, though nymphal western black-legged ticks were more frequently found, and were more abundant in coast live oak forest and desert/semi-desert scrub (dominated by California sagebrush) habitats. We observed Borrelia infections in ticks at all sites where we able to collect >10 ticks. The recently recognized human pathogen, B. miyamotoi, was observed at a higher prevalence (13/349 nymphs = 3.7%, 95% CI = 2.0–6.3; 5/273 adults = 1.8%, 95% CI = 0.6–4.2) than recent studies from nearby locations (Alameda County, east of the San Francisco Bay), demonstrating that tick-borne disease risk and ecology can vary substantially at small geographic scales, with consequences for public health and disease diagnosis.     

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.     

Seasonal dynamics of tick burden and associated Borrelia burgdorferi s.l. and Borrelia miyamotoi infections in rodents in a Dutch forest ecosystem

Ixodes ricinus ticks transmit Borrelia burgdorferi sensu lato (s.l.) as well as Borrelia miyamotoi. Larvae become infected when feeding on infected rodents, with horizontal transmission of B. burgdorferi and horizontal and vertical transmission of B. miyamotoi. We studied seasonal dynamics of infection rates of I. ricinus and their rodent hosts, and hence transmission risk of these two distinctly different Borrelia species. Rodents were live-trapped and inspected for ticks from May to November in 2013 and 2014 in a forest in The Netherlands. Trapped rodents were temporarily housed in the laboratory and detached ticks were collected. Borrelia infections were determined from the trapped rodents and collected ticks. Borrelia burgdorferi s.l. and B. miyamotoi were found in ticks as well as in rodents. Rodent density was higher in 2014, whereas tick burden as well as the Borrelia infection rates in rodents were higher in 2013. The density of B. miyamotoi-infected nymphs did not differ between the years. Tick burdens were higher on Apodemus sylvaticus than on Myodes glareolus, and higher on males than on females. Borrelia-infection rate of rodents varied strongly seasonally, peaking in summer. As the larval tick burden also peaked in summer, the generation of infected nymphs was highest in summer. We conclude that the heterogeneity of environmental and host-specific factors affects the seasonal transmission of Borrelia spp., and that these effects act more strongly on horizontally transmitted B. burgdorferi spp. than on the vertically transmitted B. miyamotoi.

     

Tick Surveillance for Relapsing Fever Spirochete Borrelia miyamotoi in Hokkaido,Japan

During 2012–2013, a total of 4325 host-seeking adult ticks belonging to the genus Ixodes were collected from various localities of Hokkaido, the northernmost island of Japan. Tick lysates were subjected to real-time PCR assay to detect borrelial infection. The assay was designed for specific detection of the Relapsing fever spirochete Borrelia miyamotoi and for unspecific detection of Lyme disease-related spirochetes. Overall prevalence of B. miyamotoi was 2% (71/3532) in Ixodes persulcatus, 4.3% (5/117) in Ixodes pavlovskyi and 0.1% (1/676) in Ixodes ovatus. The prevalence in I. persulcatus and I. pavlovskyi ticks were significantly higher than in I. ovatus. Co-infections with Lyme disease-related spirochetes were found in all of the tick species. During this investigation, we obtained 6 isolates of B. miyamotoi from I. persulcatus and I. pavlovskyi by culture in BSK-M medium. Phylogenetic trees of B. miyamotoi inferred from each of 3 housekeeping genes (glpQ, 16S rDNA, and flaB) demonstrated that the Hokkaido isolates were clustered with Russian B. miyamotoi, but were distinguishable from North American and European B. miyamotoi. A multilocus sequence analysis using 8 genes (clpA, clpX, nifS, pepX, pyrG, recG, rplB, and uvrA) suggested that all Japanese B. miyamotoi isolates, including past isolates, were genetically clonal, although these were isolated from different tick and vertebrate sources. From these results, B. miyamotoi-infected ticks are widely distributed throughout Hokkaido. Female I. persulcatus are responsible for most human tick-bites, thereby I. persulcatus is likely the most important vector of indigenous relapsing fever from tick bites in Hokkaido.     

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.     

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.     

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.     

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.     

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.     

Large Linear Plasmids of Borrelia Species That Cause Relapsing Fever

Borrelia species of relapsing fever (RF) and Lyme disease (LD) lineages have linear chromosomes and both linear and circular plasmids. Unique to RF species, and little characterized to date, are large linear plasmids of ∼160 kb, or ∼10% of the genome. By a combination of Sanger and next-generation methods, we determined the sequences of large linear plasmids of two New World species: Borrelia hermsii, to completion of its 174-kb length, and B. turicatae, partially to 114 kb of its 150 kb. These sequences were then compared to corresponding sequences of the Old World species B. duttonii and B. recurrentis and to plasmid sequences of LD Borrelia species. The large plasmids were largely colinear, except for their left ends, about 27 kb of which was inverted in New World species. Approximately 60% of the B. hermsii lp174 plasmid sequence was repetitive for 6 types of sequence, and half of its open reading frames encoded hypothetical proteins not discernibly similar to proteins in the database. The central ∼25 kb of all 4 linear plasmids was syntenic for orthologous genes for plasmid maintenance or partitioning in Borrelia species. Of all the sequenced linear and circular plasmids in Borrelia species, the large plasmid''s putative partition/replication genes were most similar to those of the 54-kb linear plasmids of LD species. Further evidence for shared ancestry was the observation that two of the hypothetical proteins were predicted to be structurally similar to the LD species'' CspA proteins, which are encoded on the 54-kb plasmids.     

Detection and Genetic Characterization of Relapsing Fever Spirochete Borrelia miyamotoi in Estonian Ticks

During the years 2008–2010 I. ricinus and I. persulcatus ticks were collected from 64 sites in mainland Estonia and on the island Saaremaa. Presence of B. miyamotoi was found in 0.9% (23/2622) of ticks. The prevalence in I. persulcatus and I. ricinus ticks differed significantly, 2.7% (15/561) and 0.4% (8/2061), respectively. The highest prevalence rates were in found South-Eastern Estonia in an area of I. persulcatus and I. ricinus sympatry and varied from 1.4% (1/73) to 2.8% (5/178). Co-infections with B. burgdorferi s.l. group spirochetes and tick-borne encephalitis virus were also revealed. Genetic characterization of partial 16S rRNA, p66 and glpQ genes demonstrated that Estonian sequences belong to two types of B. miyamotoi and cluster with sequences from Europe and the European part of Russia, as well as with sequences from Siberia, Asia and Japan, here designated as European and Asian types, respectively. Estonian sequences of the European type were obtained from I. ricinus ticks only, whereas the Asian type of B. miyamotoi was shown for both tick species in the sympatric regions.     

Infestation of taiga ticks with borrelias in the territory of Novosibirsk Scientific Center (Siberian Branch,Russian Academy of Sciences)

Borrelia specimens were revealed in taiga ticks Ixodes persulcatus collected in the wild by flagging and also in ticks provided by the Vaccination section of the Novosibirsk Scientific Center, Siberian Branch of the Russian Academy of Sciences (NSC); these ticks were obtained from patients attacked by ticks. Isolation of borrelias in the BSK-H medium had demonstrated the presence of B. garinii, B. afzelii, and B. miyamotoi in the territory of NCS. B. miyamotoi isolates were unstable, loosing their growth ability during subsequent cultivation. DNA of the three above species was detected by PCR in tick samples collected by flagging and obtained from humans. DNA of B. garinii was recorded in ticks more often; DNA of B. afzelii was found less frequently; B. miyamotoi DNA was detected in the smallest number of ticks. In ticks collected by flagging, DNA of B. garinii, B. afzelii, and B. miyamotoi was detected in 38.6%, 9.9%, and in 3.9% of specimens, respectively. In ticks collected from attacked humans, the number of positive tests was lower; e.g., DNA of B. garinii, B. afzelii, and B. miyamotoi was detected in 24.2%, 6.9%, and in 5.6% of samples, respectively. Mixed infection of ticks with two Borrelia species was also detected; DNA of B. miyamotoi and of B. garinii was detected in mixed infections more frequently.     

Host and pathogen DNA identification in blood meals of nymphal Ixodes ricinus ticks from forest parks and rural forests of Poland

DNA analysis of blood meals from unfed nymphal Ixodes ricinus allows for the identification of tick host and tick-borne pathogens in the host species. The recognition of host species for tick larvae and the reservoirs of Borrelia, Rickettsia and Anaplasma species were simultaneously carried out by analysis of the blood meals of 880 questing nymphal I. ricinus ticks collected in forest parks of Szczecin city and rural forests in northwestern Poland that are endemic areas for Lyme borreliosis. The results obtained from the study indicate that I. ricinus larvae feed not only on small or medium animals but also on large animals and they (i.e. roe deer, red deer and wild boars) were the most prevalent in all study areas as the essential hosts for larvae of I. ricinus. The composition of medium and small vertebrates (carnivores, rodents, birds and lizards) provided a more diverse picture depending on study site. The reservoir species that contain the most pathogens are the European roe deer Capreolus capreolus, in which two species of Rickettsia and two species of Borrelia were identified, and Sus scrofa, in which one Rickettsia and three Borrelia species were identified. Rickettsia helvetica was the most common pathogen detected, and other included species were the B. burgdorferi s.l. group and B. miyamotoi related to relapsing fever group. Our results confirmed a general association of B. garinii with birds but also suggested that such associations may be less common in the transmission cycle in natural habitats than what was thought previously.     

Borrelia crocidurae in Ornithodoros ticks from northwestern Morocco: a range extension in relation to climatic change?

Tick‐borne relapsing fever (TBRF) is caused by Borrelia spirochetes transmitted to humans by Argasid soft ticks of the genus Ornithodoros. We investigated the presence of Ornithodoros ticks in rodent burrows in nine sites of the Gharb region of northwestern Morocco where we recently documented a high incidence of TBRF in humans. We assessed the Borrelia infection rate by nested PCR and sequencing. All sites investigated were colonized by ticks of the Ornithodoros marocanus complex and a high proportion of burrows (38.4%) were found to be infested. Borrelia infections were observed in 6.8% of the ticks tested. Two Borrelia species were identified by sequencing: B. hispanica and B. crocidurae. The discovery in northwestern Morocco of Ornithodoros ticks infected by B. crocidurae represents a 350 km range extension of this Sahelo‐Saharan spirochete in North Africa. The spread of B. crocidurae may be related to the increasing aridity of northwestern Morocco in relation to climate change.     

Genomic Characteristics of Chinese Borrelia burgdorferi Isolates

In China, B. burgdorferi, B.garinii, B. afzelii and B. yangtze sp. nov have been reported; B.garinii and B. afzelii are the main pathogenic genotypes. But until now only one Chinese strain was reported with whole genome sequence. In order to further understand the genomic characteristics and diversity of Chinese Borrelia strains, 5 isolates from China were sequenced and compared with the whole genome sequences of strains in other areas. The results showed a high degree of conservation within the linear chromosome of Chinese strains, whereas plasmid showed a much larger diversity according to the majority genomic information of plasmids. The genome sequences of the five Chinese strains were compared with the corresponding reference strains, respectively, according to the genospecies. Pairwise analysis demonstrates that there are only 70 SNPs between the genomes of CS4 and B31. However, there are many more SNPs between the genomes of QX-S13 and VS116, PD91 and PBi, FP1 and PKo, R9 and Pko, respectively. Gene comparison showed some important different genes. OspA was one of the important different genes. Comparative genomic studies have found that OspA gene sequences of PD91 and R9 had great differences compared with the sequence of B31. OspA gene sequence of R9 had a 96bp deletion; OspA gene of PD91 had two deletions: 9bp and 10 bp. To conclude, we showed the genomic characteristics of four genotype Chinese B. burgdorferi strains. The genomic sequence of B. yangtze sp. nov and differences from B. valaisiana were first reported. Comparative analysis of Chinese strains with the different Borrelia species from other areas will help us to understand evolution and pathogenesis of Chinese Borrelia burgdorferi strains.     

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.     

Epidemiology of Tick-Borne Borreliosis in Morocco

Background

The presence in Morocco of Argasid ticks of the Ornithodoros erraticus complex, the vector of tick-borne relapsing fever (TBRF) in North Africa, has been known since 1919, but the disease is rarely diagnosed and few epidemiological data are available.

Methodology/Principal Findings

Between 2006 and 2011, we investigated the presence of Ornithodoros ticks in rodent burrows in 34 sites distributed across Morocco. We also collected small mammals in 10 sites and we investigated TBRF in febrile patients in Kenitra district. The prevalence of Borrelia infections was assessed by nested PCR amplification in ticks and the brain tissue of small mammals, and by evaluation of thick blood films in patients. A high proportion of burrows were infested with ticks of the O. erraticus complex in all regions of Morocco, with a mean of 39.5% for the whole country. Borrelia infections were found in 39/382 (10.2%) of the ticks and 12/140 (8.6%) of the rodents and insectivores studied by PCR amplification, and 102 patients tested positive by thick blood film. Five small mammalian species were found infected: Dipodillus campestris, Meriones shawi, Gerbillus hoogstrali, Gerbillus occiduus and Atelerix algirus. Three Borrelia species were identified in ticks and/or rodents: B. hispanica, B. crocidurae and B. merionesi.

Conclusions/Significance

Tick populations belonging to O. erraticus complex are widely distributed in Morocco and a high proportion of ticks and small mammals are infected by Borrelia species. Although rarely diagnosed, TBRF may be a common cause of morbidity in all regions of Morocco.