Absence of Rickettsia rickettsii and Occurrence of Other Spotted Fever Group Rickettsiae in Ticks from Tennessee

Rocky Mountain spotted fever (RMSF) is the most common tick-borne illness in Tennessee. Little is known about the occurrence of R. rickettsii, the causative agent, in ticks in Tennessee. To better understand the prevalence and distribution of rickettsial agents in ticks, we tested 1,265 Amblyomma, Dermacentor, and Ixodes adult and nymphal ticks. Additionally, we tested 231 Amblyomma americanum larvae. Ticks were collected from 49 counties from humans, wild animals, domestic canines, and flannel drags. Spotted fever group rickettsiae (SFGR) DNA was detected by polymerase chain reaction (PCR) in 32% of adult and nymphal ticks. A total minimum infection rate of 85.63 was found in larval pools tested. Three rickettsial species, Rickettsia montana, Rickettsia amblyommii, and Rickettsia cooleyi were identified by molecular analysis. Rickettsia rickettsii was not detected. This study suggests that some RMSF cases reported in Tennessee may be caused by cross-reactivity with other SFGR antigenically related to R. rickettsii.     

High Prevalence of Rickettsia typhi and Bartonella Species in Rats and Fleas,Kisangani, Democratic Republic of the Congo

The prevalence and identity of Rickettsia and Bartonella in urban rat and flea populations were evaluated in Kisangani, Democratic Republic of the Congo (DRC) by molecular tools. An overall prevalence of 17% Bartonella species and 13% Rickettsia typhi, the agent of murine typhus, was found in the cosmopolitan rat species, Rattus rattus and Rattus norvegicus that were infested by a majority of Xenopsylla cheopis fleas. Bartonella queenslandensis, Bartonella elizabethae, and three Bartonella genotypes were identified by sequencing in rat specimens, mostly in R. rattus. Rickettsia typhi was detected in 72% of X. cheopis pools, the main vector and reservoir of this zoonotic pathogen. Co-infections were observed in rodents, suggesting a common mammalian host shared by R. typhi and Bartonella spp. Thus, both infections are endemic in DRC and the medical staffs need to be aware knowing the high prevalence of impoverished populations or immunocompromised inhabitants in this area.     

Rickettsia Sca2 has evolved formin-like activity through a different molecular mechanism

Sca2 (surface cell antigen 2) is the only bacterial protein known to promote both actin filament nucleation and profilin-dependent elongation, mimicking eukaryotic formins to assemble actin comet tails for Rickettsia motility. We show that Sca2’s functional mimicry of formins is achieved through a unique mechanism. Unlike formins, Sca2 is monomeric, but has N- and C-terminal repeat domains (NRD and CRD) that interact with each other for processive barbed-end elongation. The crystal structure of NRD reveals a previously undescribed fold, consisting of helix–loop–helix repeats arranged into an overall crescent shape. CRD is predicted to share this fold and might form together with NRD, a doughnut-shaped formin-like structure. In between NRD and CRD, proline-rich sequences mediate the incorporation of profilin-actin for elongation, and WASP-homology 2 (WH2) domains recruit actin monomers for nucleation. Sca2’s α-helical fold is unusual among Gram-negative autotransporters, which overwhelmingly fold as β-solenoids. Rickettsia has therefore “rediscovered” formin-like actin nucleation and elongation.Many bacterial pathogens use the actin cytoskeleton of host eukaryotic cells for invasion and motility (1, 2). In so doing, bacteria often resort to mimicry by expressing proteins that adopt core functions of key actin cytoskeletal components, particularly actin filament nucleation and elongation factors. However, bacterial proteins tend to bypass the elaborate regulatory networks characteristic of their eukaryotic counterparts, offering a rare opportunity to dissect their functions within a simplified system (2, 3), with implications for our understanding of pathogenicity and the eukaryotic actin cytoskeleton alike.Rickettsiae are obligate intracellular Gram-negative pathogens that are transmitted to humans via arthropod vectors, such as ticks, fleas, and lice (4). Rickettsia species are responsible for a number of severe human diseases, including typhus and spotted fever (5). The spotted fever group, including Rickettsia parkeri, Rickettsia conorii, Rickettsia rickettsii, and over 20 other species throughout the world, uses the host-cell actin cytoskeleton to spread inter- and intracellularly. Similar to Listeria and Shigella, Rickettsia forms actin comet tails to propel its movement. However, the actin tails of Rickettsia consist of long and unbranched actin filaments, whereas those of Listeria and Shigella contain shorter and densely branched filaments (6, 7). These morphological differences stem from different molecular mechanisms for comet tail formation by these pathogens. Listeria and Shigella rely heavily on the activity of the host Arp2/3 complex that localizes uniformly along their tails (6). Although the Arp2/3 complex, activated by either host nucleation promoting factors (8) or the Rickettsia surface protein RickA (9, 10), is necessary for Rickettsia invasion (11), it is absent from Rickettsia tails (6). Another protein, Sca2 (surface cell antigen 2), has been implicated in comet tail formation by spotted fever group Rickettsia species (12, 13).Sca2 is an autotransporter protein, comprising a short N-terminal signal sequence, a large passenger domain, and a C-terminal translocator domain (Fig. 1A). The signal peptide targets autotransporter proteins for passage across the inner bacterial membrane. This first step is followed by insertion of the translocator domain into the outer membrane, where it forms a pore through which the passenger domain is translocated and either cleaved or held tethered on the surface of the bacterium (14). By immunofluorescence microscopy, Sca2 has been localized to the actin tail-associated surface of R. parkeri (13), and disruption of the sca2 gene in R. rickettsii inhibits actin-tail formation and motility (12), which also results in reduced virulence. Sca2 may play a separate role in mediating the association of Rickettsia pathogens with mammalian host cells. Thus, Escherichia coli cells expressing R. conorii Sca2 gain the ability to adhere and invade mammalian cells (15). The minimal domain sufficient for association with mammalian cells was recently mapped to Sca2 residues 34–556 (16).Open in a separate windowFig. 1.Actin polymerization activities of Sca2 constructs. (A) Domain organization of Sca2 and constructs used in this study (SS, signaling sequence; W, WH2 domains A, B and C; AC, autochaperone domain; TD, translocator domain. Constructs that were also made as Avi-tag fusions for Qdot labeling are highlighted in red. Constructs containing mutations in the proline-rich regions or WH2 domains are highlighted in magenta or maroon, respectively (the specific mutations are described in Fig. S2A). (B) Normalized time course of polymerization of 2 μM Mg-ATP-actin (6% pyrene-labeled) alone (black) or in the presence of 25 nM Sca2 constructs, as indicated. Initial polymerization rates were calculated between 0.1 and 0.3 of the normalized fluorescence and are shown in parenthesis. (C–F) Time course of polymerization of 2 μM Mg-ATP-actin (6% pyrene-labeled) alone (black) or with increasing concentrations of the Sca2 constructs shown in B (C), as well as constructs Sca421-670 (D), Sca34-1342 (E), and Sca1515-W_ABC (F), which are not shown in B.In vitro, Sca2 displays actin assembly properties that resemble those of eukaryotic formins; it nucleates unbranched actin filaments, processively associates with growing barbed ends, requires profilin-actin for efficient elongation, and inhibits the activity of capping protein (13). Although these activities led to the suggestion that Sca2 functionally mimics eukaryotic formins, it is unknown how this is mechanistically achieved. Here, we show that Rickettsia Sca2 has evolved formin-like activity through an entirely unique structural and functional mechanism.     

Spotted Fever Group Rickettsia in Small Rodents from Areas of Low Endemicity for Brazilian Spotted Fever in the Eastern Region of Minas Gerais State,Brazil

We investigated the humoral immune response against different species of Rickettsia in serum samples from small rodents collected in two areas of a silent focus for Brazilian spotted fever in the eastern region of Minas Gerais State, Brazil. Sera samples were analyzed by indirect immunofluorescence assay using antigens from Rickettsia species of the spotted fever, ancestral, and transition groups. Titers ≥ 1:64 were considered positive. In Santa Cruz do Escalvado, 94% (30 of 32) of the samples collected from Rattus rattus, 22% (5 of 23) from Nectomys squamipes, and 80% (4 of 5) from Akodon sp., reacted by indirect immunofluorescence assay with Rickettsia antigens of the spotted fever group. In the municipality of Pingo D''Água, 84% (26 of 31) of the samples collected from R. rattus, 86% (6 of 7) of the samples from Oryzomys subflavus, 86% (6 of 7) from N. squamipes, and 100% (1 of 1) from Bolomys sp. contained antibodies that reacted with rickettsial antigens of the spotted fever group. These results demonstrated the previous exposure of small rodents to spotted fever group Rickettsia, suggesting the participation of these animals in the natural history of these rickettsiae in this region.     

Molecular Detection of Rickettsia felis and Bartonella henselae in Dog and Cat Fleas in Central Oromia,Ethiopia

Fleas are important vectors of several Rickettsia and Bartonella spp. that cause emerging zoonotic diseases worldwide. In this study, 303 fleas collected from domestic dogs and cats in Ethiopia and identified morphologically as Ctenocephalides felis felis, C. canis, Pulex irritans, and Echidnophaga gallinacea were tested for Rickettsia and Bartonella DNA by using molecular methods. Rickettsia felis was detected in 21% of fleas, primarily C. felis, with a similar prevalence in fleas from dogs and cats. A larger proportion of flea-infested dogs (69%) than cats (37%) harbored at least one C. felis infected with R. felis. Rickettsia typhi was not detected. Bartonella henselae DNA was detected in 6% (2 of 34) of C. felis collected from cats. Our study highlights the likelihood of human exposure to R. felis, an emerging agent of spotted fever, and B. henselae, the agent of cat-scratch disease, in urban areas in Ethiopia.     

Molecular Detection of Rickettsia felis in Different Flea Species from Caldas,Colombia

Rickettsioses caused by Rickettsia felis are an emergent global threat. Historically, the northern region of the province of Caldas in Colombia has reported murine typhus cases, and recently, serological studies confirmed high seroprevalence for both R. felis and R. typhi. In the present study, fleas from seven municipalities were collected from dogs, cats, and mice. DNA was extracted and amplified by polymerase chain reaction (PCR) to identify gltA, ompB, and 17kD genes. Positive samples were sequenced to identify the species of Rickettsia. Of 1,341 fleas, Ctenocephalides felis was the most prevalent (76.7%). Positive PCR results in the three genes were evidenced in C. felis (minimum infection rates; 5.3%), C. canis (9.2%), and Pulex irritans (10.0%). Basic Local Alignment Search Tool (BLAST) analyses of sequences showed high identity values (> 98%) with R. felis, and all were highly related by phylogenetic analyses. This work shows the first detection of R. felis in fleas collected from animals in Colombia.     

Case Report: A Patient from Argentina Infected with Rickettsia massiliae

The first confirmed case of Rickettsia massiliae infection in the New World (Buenos Aires, Argentina) is described. To date, only two cases of human infection had been reported in Europe. The patient, a woman, had a fever, a palpable purpuric rash on the upper and lower extremities, and a skin lesion (eschar) on the right leg compatible with tache noire. When interviewed, she reported having had contact with dog ticks. After treatment with doxycycline for 12 days, her symptoms resolved. Rickettsia massiliae infection was diagnosed by molecular-based detection of the microorganism in a biopsy specimen of the eschar.Rickettsia massiliae is a spotted fever group Rickettsia broadly distributed around the world and is associated with Rhipicephalus ticks.^1–4 Its pathogenic role was suspected because its seroprevalence in humans was observed, and some authors reported that this Rickettsia could be the causative agent of some cases of Mediterranean spotted fever (MSF).⁵ To date, only two human cases of R. massiliae infection in Europe have been documented and confirmed with molecular methods. The first case was detected in a blood sample from a patient diagnosed with MSF in Italy; the blood sample had been stored for 20 years before the case was detected.⁶ The second case was in a patient with spotted fever and acute loss of vision in southern France.⁷On July 1, 2005, a 56-year-old woman living in Buenos Aires, Argentina, was admitted to the emergency department of a hospital in Villagarcía de Arosa, Galicia, Spain, because of fever, chills, and malaise for 72 hours and a rash that was present for a few hours. The patient had arrived in Spain 48 hours earlier on a flight from Argentina. She had a history of convulsions related to arterio-venous malformation in the frontal brain area and was treated with phenobarbital. She had a fever (40°C) and a palpable purpuric rash all over the trunk and on the upper and lower extremities with the palms and soles affected (Figure 1).Open in a separate windowFigure 1.Purpuric rash on lower extremities of the patient, which affected the soles of her feet. This figure appears in color at www.ajtmh.org.Hemocultures were prepared and treatment was initiated with amoxicillin-clavulanic acid and an infusion of amikacin. An allergic reaction was suspected, phenobarbital was discontinued, and gabapentin treatment was initiated. Laboratory evaluation showed a leukocyte count of 1.83 × 10⁴ cells/µL with 18% immature forms, a prothrombin ratio of 73%, an aspartate aminotransferase level of 111 IU/L, an alanine aminotransferase level of 449 IU/L, a gamma-glutamyl transpeptidase level of 1,102 IU/L, an alkaline phosphatase level of 546 U/L, and a lactate dehydrogenase level of 1,132 U/L. The patient reported the next day that she removed ticks from her dog one week earlier and found several engorged ticks in her garden. Doxycycline (100 mg every 12 hours) was then administered.The same day, a skin lesion on the right leg compatible with tache noire was observed (Figure 2). The patient had a torpid course and a pleural effusion was developed. Treatment with prednisone was prescribed. A biopsy specimen was obtained from the lesion (eschar). On day 12, the patient was afebrile and recovered. Blood cultures and results of serologic testing for hepatitis A, B, and C viruses, Epstein-Barr virus, cytomegalovirus, Rickettsia conorii, Coxiella burnetti, Borrellia burgdorferi, and human immunodeficiency virus (performed with a serum sample obtained the day after her admission to hospital) were negative. The absence of antibodies against R. conorii could have been the result of the antibiotic treatment, which may have reduced the antibody response.Open in a separate windowFigure 2.Tache noire on the right leg of the patient. This figure appears in color at www.ajtmh.org.The biopsy sample of the eschar was sent to the Department of Infectious Diseases at the Hospital San Pedro–Centro de Investigación Biomédica de La Rioja in La Rioja, Spain, because rickettsiosis was suspected. DNA was extracted from the biopsy specimen by using QIAamp Tissue Kit (Qiagen, Hilden, Germany). Presumptive diagnosis of rickettsiosis was confirmed by nested polymerase chain reaction (PCR) assays that amplified fragments of the citrate synthase (gltA) and outer membrane protein (ompB) rickettsial genes (8^,9 Negative controls (one with template DNA but without primers and the other with primers and water instead of template DNA) and a positive control (DNA from R. conorii strain Malish #7) were included in all PCR assays. To minimize the potential for DNA contamination, three separate, designated areas were used for extraction of DNA and preparation of PCRs. Amplicons of the expected size were subjected to sequence determination. The nucleotide sequences obtained were found to share > 99% similarity with the corresponding gltA and ompB fragments of R. massiliae.

Table 1

Primers used for amplification of partial rickettsial genes^*

Seroepidemiological Study of Outdoor Recreationists' Exposure to Spotted Fever Group Rickettsia in Western Australia

Bushland activity has previously been linked to rickettsial exposure in eastern and central regions of Australia, whereas little is known about the risks in Western Australia. The isolation of Rickettsia gravesii sp. nov. from Amblyomma triguttatum ticks and anecdotal reports of low-grade illness among bush recreationists raised the possibility of rickettsial transmission in the State. This study investigated rickettsial seroprevalence and potential risk of exposure to the spotted fever group rickettsiae in rogainers. Our results showed that rogainers active in the bush had a significantly higher risk of seropositivity (immunofluorescence total antibody titer ≥ 128) for the spotted fever group Rickettsia (odds ratio [OR] = 14.02, 95% confidence interval [CI] = 1.38–142.07) compared with a reference population, the overall seroprevalence in the rogainer group being 23.1%.     

Rickettsia and Bartonella Species in Fleas from Reunion Island

Rickettsia felis, Rickettsia typhi, and Bartonella DNA was detected by molecular tools in 12% of Rattus rattus fleas (Xenopsylla species) collected from Reunion Island. One-third of the infested commensal rodents captured during 1 year carried at least one infected flea. As clinical signs of these zoonoses are non-specific, they are often misdiagnosed.     

Prevalence of Human-Active and Variant 1 Strains of the Tick-Borne Pathogen Anaplasma phagocytophilum in Hosts and Forests of Eastern North America

Anaplasmosis is an emerging infectious disease caused by infection with the bacterium Anaplasma phagocytophilum. In the eastern United States, A. phagocytophilum is transmitted to hosts through the bite of the blacklegged tick, Ixodes scapularis. We determined the realized reservoir competence of 14 species of common vertebrate hosts for ticks by establishing the probability that each species transmits two important strains of A. phagocytophilum (A. phagocytophilum human-active, which causes human cases, and A. phagocytophilum variant 1, which does not) to feeding larval ticks. We also sampled questing nymphal ticks from ∼150 sites in a single county over 2 years and sampled over 6 years at one location. White-footed mice (Peromyscus leucopus) and Eastern chipmunks (Tamias striatus) were the most competent reservoirs for infection with the A. phagocytophilum human-active strain. Across the county, prevalence in ticks for both strains together was 8.3%; ticks were more than two times as likely to be infected with A. phagocytophilum human-active as A. phagocytophilum variant 1.     

法国野猪中Rickettsia raoultii的流行

目的调查和鉴定法国野猪身上Rickettsiaraoultii的流行情况以及野猪作为贮存宿主所起的作用。方法收集法国2007年9月到11）1的野猪身上的边缘革蜱163只。应用柠檬酸合成酶基因和外膜蛋白基因进行实时定量PCR、普通PCR技术及序列分析方法检测立克次体。结果113只（69．3％）边缘革蜱立克次检测阳性。进一步鉴定为斑点热的两类病原,其中R．raoultii占57．5％（存在于65只蜱中）和R．slovaca占42．5％（存在于48只蜱中）。结论证明R．raoultii是野猪身上边缘革蜱的主要病原,边缘革蜱中感染率较高。应警惕野猪对立克次体的传播作用。     

Whole Genome Sequence Analysis of a Prototype Strain of the Novel Putative Rotavirus Species L

Rotaviruses infect humans and animals and are a main cause of diarrhea. They are non-enveloped viruses with a genome of 11 double-stranded RNA segments. Based on genome analysis and amino acid sequence identities of the capsid protein VP6, the rotavirus species A to J (RVA-RVJ) have been defined so far. In addition, rotaviruses putatively assigned to the novel rotavirus species K (RVK) and L (RVL) have been recently identified in common shrews (Sorex araneus), based on partial genome sequences. Here, the complete genome sequence of strain KS14/0241, a prototype strain of RVL, is presented. The deduced amino acid sequence for VP6 of this strain shows only up to 47% identity to that of RVA to RVJ reference strains. Phylogenetic analyses indicate a clustering separated from the established rotavirus species for all 11 genome segments of RVL, with the closest relationship to RVH and RVJ within the phylogenetic RVB-like clade. The non-coding genome segment termini of RVL showed conserved sequences at the 5′-end (positive-sense RNA strand), which are common to all rotaviruses, and those conserved among the RVB-like clade at the 3′-end. The results are consistent with a classification of the virus into a novel rotavirus species L.     

Detection of Rickettsia africae in patients and ticks along the coastal region of Cameroon

Rickettsia africae was identified in seven (6%) of 118 patients with acute fevers of unknown etiology proven not to be malaria or typhoid fever from clinics along the coastal region of Cameroon by polymerase chain reaction (PCR) amplification and sequencing of the citrate synthase (gltA) and outer membrane protein A (ompA) genes of Rickettsia. The majority (71%) of the patients were female. Clinical manifestations included fever (100%), headache (71%), myalgia (71%), arthralgia (43%), pulmonary involvement (29%), and diffuse rash (14%). Moreover, R. africae was detected by PCR amplification and sequence analysis of the gltA and ompA genes in 62 (75%) of 83 adult Amblyomma variegatum ticks collected from cattle in the same region. These results confirm the presence of a previously unrecognized infectious disease in the indigenous Cameroonian population, as well as extend the established range of R. africae.     

Tick-borne rickettiosis in Guadeloupe, the French West Indies: isolation of Rickettsia africae from Amblyomma variegatum ticks and serosurvey in humans, cattle, and goats.

Twenty-seven rickettsiae were isolated and/or detected from 100 Amblyomma variegatum ticks collected on Guadeloupe in the French West Indies. In this study, the polymerase chain reaction procedure appeared to be more sensitive in detecting rickettsiae in ticks than the shell-vial technique. Sequencing a portion of the outer membrane protein A-encoding gene showed that these rickettsiae appeared to be identical to Rickettsia africae, a member of the spotted fever group rickettsiae recently described as an agent of African tick-bite fever occurring in sub-Sahelian Africa. A high seroprevalence of antibodies to R. africae was demonstrated among mammals, particularly humans, cattle, and goats. These results and a recently reported case of an infection due to R. africae on Guadeloupe demonstrate that R. africae is present on this island. Although this disease has been underdiagnosed there, it may be frequent and may exist on other Caribbean islands where A. variegatum has propagated dramatically over recent years.     

Epidemiology of Spotted Fever Group and Typhus Group Rickettsial Infection in the Amazon Basin of Peru

A seroprevalence study for IgG antibodies against spotted fever group (SFGR) and typhus group (TGR) Rickettsia among humans and domestic pets was conducted in the city of Iquitos, located in the Amazon basin of Peru. Of 1,195 human sera analyzed, 521 (43.6%) and 123 (10.3%) were positive for SFGR and TGR antibodies, respectively. District of residence and participant age were associated with antibody positivity for both groups, whereas rodent sightings in the home were associated with TGR antibody positivity. Of the 71 canines tested, 42 (59.2%) were positive for SFGR antibodies, and two (2.8%) were positive for TGR antibodies; one active SFGR infection was detected by polymerase chain reaction. An uncharacterized SFGR species was detected in 95.9% (71/74) of Ctenocephalides felis pools collected from domestic pets. These data suggest that rickettsial transmission is widespread in Iquitos. Rickettsia species should be further explored as potential causes of acute febrile illnesses in the region.     

Usefulness of rickettsial PCR assays for the molecular diagnosis of human rickettsioses

Background

The effectiveness of PCR methods to amplify rickettsiae from clinical samples has still not been evaluated. Our aim was to determine the sensitivity and usefulness for Rickettsia species identification by PCR methods, targeting 16S rDNA, htrA, gltA, ompA, and ompB genes for molecular diagnosis of rickettsioses.

Methods

A total of 72 clinical samples (EDTA-blood, skin biopsies and ticks) taken from 52 patients in the early phase of the illness with PCR-confirmed rickettsioses were included. Single [16S rDNA, gltA (5′ end), and htrA genes] and sequential (nested or semi-nested) PCR assays [ompB, gltA (central region) and ompA genes] were performed.

Results

For single-stage PCR assays, the greatest sensitivity (33.3%) was obtained using the gltA (5′ end), while for sequential assays, the most sensitive results were obtained using the ompB assay (83.3%). The highest sensitivity (100%) was achieved using the three sequential PCRs. The ompA PCR method was the most reliable for identifying Rickettsia species, according to clinical features.

Conclusions

PCR-based amplification methods are useful rickettsial diagnostic tools in the early phase of the illness. The three sequential PCR assays here investigated (ompB, gltA and ompA) appear to be useful tools for molecular diagnosis of rickettsioses. ompB PCR assay is effective for primary screening, since it detects a high percentage of positive samples. ompA assay is the most useful method to identify a Rickettsia species in human pathology. Nevertheless, epidemiology, clinical symptoms and the vector involved in the infection have to be taken into account for the diagnosis of rickettsioses.     

A modest model explains the distribution and abundance of Borrelia burgdorferi strains

The distribution and abundance of Borrelia burgdorferi, including human Lyme disease strains, is a function of its interactions with vertebrate species. We present a mathematical model describing important ecologic interactions affecting the distribution and abundance of B. burgdorferi strains, marked by the allele at the outer surface protein C locus, in Ixodes scapularis ticks, the principal vector. The frequency of each strain in ticks can be explained by the vertebrate species composition, the density of each vertebrate species, the number of ticks that feed on individuals of each species, and the rate at which those ticks acquire different strains. The model results are consistent with empirical data collected in a major Lyme disease focus in New England. An applicable extension of these results would be to predict the proportion of ticks carrying human infectious strains of B. burgdorferi from disease host densities and thus predict the local risk of contracting Lyme disease.     

A Prospective Evaluation of Real-Time PCR Assays for the Detection of Orientia tsutsugamushi and Rickettsia spp. for Early Diagnosis of Rickettsial Infections during the Acute Phase of Undifferentiated Febrile Illness

One hundred and eighty febrile patients were analyzed in a prospective evaluation of Orientia tsutsugamushi and Rickettsia spp. real-time polymerase chain reaction (PCR) assays for early diagnosis of rickettsial infections. By paired serology, 3.9% (7 of 180) and 6.1% (11 of 180) of patients were confirmed to have acute scrub or murine typhus, respectively. The PCR assays for the detection of O. tsutsugamushi and Rickettsia spp. had high specificity (99.4% [95% confidence interval (CI): 96.8–100] and 100% [95% CI: 97.8–100], respectively). The PCR results were also compared with immunoglobulin M (IgM) immunofluorescence assay (IFA) on acute sera. For O. tsutsugamushi, PCR sensitivity was twice that of acute specimen IgM IFA (28.6% versus 14.3%; McNemar''s P = 0.3). For Rickettsia spp., PCR was four times as sensitive as acute specimen IgM IFA (36.4% versus 9.1%; P = 0.08), although this was not statistically significant. Whole blood and buffy coat, but not serum, were acceptable specimens for these PCRs. Further evaluation of these assays in a larger prospective study is warranted.     

Investigation of Borrelia spp. in ticks (Acari: Ixodidae) at the border crossings between China and Russia in Heilongjiang Province, China

ObjectiveTo investigate the precise species of tick vector and the Borrelia spirochete pathogen at the Heilongjiang Province international border with Russia.MethodsIn this study, ticks were collected from 12 Heilongjiang border crossings (including grasslands, shrublands, forests, and plantantions) to determine the rate and species type of spirochete-infected ticks and the most prevalent spirochete genotypes.ResultsThe ticks represented three genera and four species of the Ixodidae family [Ixodes persulcatus, Dermacentor silvarum, Haemaphysalis concinna and Haemaphysalis japonica]. Ixodes persulcatus had the highest amount of Borrelia burgdorferi sensu lato infection of 25.6% and the most common species of Borrelia isolated from Ixodes persulcatus was Borrelia garinii, strain PD91.ConclusionsOur results suggest that Borrelia garinii PD91-infected Ixodes persulcatus may be the principal cause of Lyme disease in the border crossing areas of Heilongjiang Province.