Endemic foci of the tick-borne relapsing fever spirochete Borrelia crocidurae in Mali, West Africa, and the potential for human infection.
ABSTRACT: 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.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.The potential for human tick-borne relapsing fever exists in many areas of southern Mali.
Project description:In West Africa, tick-borne relapsing fever is a neglected arthropod-borne infection caused by Borrelia crocidurae transmitted by the argasid tick Ornithodoros sonrai. From an epidemiological point of view, it is of interest to know whether some genotypes of the vector are specialized in carrying certain genotypes of the pathogen.Thirty-five O. sonrai ticks collected in Mali, Senegal, Mauritania and Morocco confirmed to be B. crocidurae-infected, were genotyped by 16S rRNA gene sequencing. B. crocidurae was genotyped by Multispacer Sequence Typing. The 35 O. sonrai ticks grouped into 12 genotypes with strong geographical structuration. MST resolved the 35 B. crocidurae isolates into 29 genotypes with pairwise divergence of 0.09 - 1.56 % without strict geographical structuration as genotype ST22 was found in Mali, Senegal and Mauritania. There was no evidence of tick-borrelia specialization as one O. sonrai genotype carried several B. crocidurae genotypes and one B. crocidurae genotype was found in different O. sonrai genotypes.This report illustrates a non-specialized circulation of B. crocidurae borreliae within O. sonrai ticks in West Africa.
Project description:<h4>Background</h4>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.<h4>Methodology/principal findings</h4>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.<h4>Conclusions/significance</h4>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.
Project description:<h4>Background</h4>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.<h4>Methods and findings</h4>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.<h4>Conclusions</h4>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.
Project description:<h4>Background</h4>Tick-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.<h4>Methodology/principal findings</h4>We 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.<h4>Conclusion/significance</h4>Our 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.
Project description: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 understand the transmission dynamics of the relapsing fever spirochete Borrelia turicatae from the vector Ornithodoros turicata, and the subsequent dissemination of the bacteria upon entry into murine blood.To determine the minimum number of ticks required to transmit spirochetes, one to three infected O. turicata were allowed to feed to repletion on individual mice. Murine infection and dissemination of the spirochetes was evaluated by dark field microscopy of blood, quantitative PCR, and immunoblotting against B. turicatae protein lysates and a recombinant antigen, the Borrelia immunogenic protein A. Transmission frequencies were also determined by interrupting the bloodmeal 15 seconds after tick attachment. Scanning electron microscopy (SEM) was performed on infected salivary glands to detect spirochetes within acini lumen and excretory ducts. Furthermore, spirochete colonization and dissemination from the bite site was investigated by feeding infected O. turicata on the ears of mice, removing the attachment site after engorment, and evaluating murine infection.Our findings demonstrated that three ticks provided a sufficient infectious dose to infect nearly all animals, and B. turicatae was transmitted within seconds of tick attachment. Spirochetes were also detected in acini lumen of salivary glands by SEM. Upon host entry, B. turicatae did not require colonization of the bite site to establish murine infection. These results suggest that once B. turicatae colonizes the salivary glands the spirochetes are preadapted for rapid entry into the mammal.
Project description: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.
Project description:Relapsing fever (RF) spirochetes colonize and are transmitted to mammals primarily by <i>Ornithodoros</i> ticks, and little is known regarding the pathogen's life cycle in the vector. To further understand vector colonization and transmission of RF spirochetes, <i>Borrelia turicatae</i> expressing a green fluorescent protein (GFP) marker (<i>B. turicatae-gfp</i>) was generated. The transformants were evaluated during the tick-mammal infectious cycle, from the third nymphal instar to adult stage. <i>B. turicatae-gfp</i> remained viable for at least 18 months in starved fourth-stage nymphal ticks, and the studies indicated that spirochete populations persistently colonized the tick midgut and salivary glands. Our generation of <i>B. turicatae-gfp</i> also revealed that within the salivary glands, spirochetes are localized in the ducts and lumen of acini, and after tick feeding, the tissues remained populated with spirochetes. The <i>B. turicatae-gfp</i> generated in this study is an important tool to further understand and define the mechanisms of vector colonization and transmission.<b>IMPORTANCE</b> In order to interrupt the infectious cycle of tick-borne relapsing fever spirochetes, it is important to enhance our understanding of vector colonization and transmission. Toward this, we generated a strain of <i>Borrelia turicatae</i> that constitutively produced the green fluorescent protein, and we evaluated fluorescing spirochetes during the entire infectious cycle. We determined that the midgut and salivary glands of <i>Ornithodoros turicata</i> ticks maintain the pathogens throughout the vector's life cycle and remain colonized with the spirochetes for at least 18 months. We also determined that the tick's salivary glands were not depleted after a transmission blood feeding. These findings set the framework to further understand the mechanisms of midgut and salivary gland colonization.
Project description:It is not uncommon that a child with a febrile illness of unknown etiology is admitted to the hospital. When the complete blood count reveals a pancytopenia, the diagnostic process can be a real challenge.A 13-year girl of Arab-Berber descent presented with abdominal pain and fever after a holiday in northwestern Morocco. A complete blood count revealed a pancytopenia and blood smear test results revealed spirochetes. Borrelia hispanica was identified by sequencing the 16S ribosomal ribonucleic acid gene. Our patient was treated with tetracyclines and during this treatment we saw full clinical and hematological recovery.Borrelia hispanica is a known cause of tick-borne relapsing fever and is transmitted to humans through the bite of soft ticks of the genus Ornithodoros (Alectorobius). Although the link between tick-borne relapsing fever and thrombocytopenia has been documented, there are only a few case reports of tick-borne relapsing fever presenting with pancytopenia. To the best of our knowledge, there is no previous report of Borrelia hispanica presenting with pancytopenia.
Project description:Borrelia spp. are pathogens responsible for worldwide tickborne relapsing fever (TBRF). In West Africa, TBRF is due to a single species, Borrelia crocidurae, transmitted by the soft-body tick Ornithodoros sonrai. We report a case of B crocidurae infection in a French tourist in Senegal, diagnosed by molecular biology using 16S rDNA, flaB, and the 16S-23S intergenic spacer. We found six imported cases reported in travellers (since 1999). We review here clinical and molecular aspects and pathophysiology, and discuss diagnostic methods and therapeutic regimens. In the coming years, this emerging disease will be of concern to more and more travellers returning from disease-endemic regions. Thus, physicians must be aware of its presentation and diagnosis, since the spontaneous outcome can be severe, and a simple treatment is effective.
Project description:Relapsing fever Borrelia spp. challenge microbiologic typing because they possess segmented genomes that maintain essential genes on large linear plasmids. Antigenic variation further complicates typing. Intergenic spacer (IGS, between 16S-23S genes) heterogeneity provides resolution among Lyme disease-associated and some relapsing fever spirochetes. We used an IGS fragment for typing East African relapsing fever Borrelia spp. Borrelia recurrentis and their louse vectors showed 2 sequence types, while 4 B. duttonii and their tick vectors had 4 types. IGS typing was unable to discriminate between the tick- and louseborne forms of disease. B. crocidurae, also present in Africa, was clearly resolved from the B. recurrentis/B. duttonii complex. IGS analysis of ticks showed relapsing fever Borrelia spp. and a unique clade, distant from those associated with relapsing fever, possibly equivalent to a novel species in ticks from this region. Clinical significance of this spirochete is undetermined.