Spotted Fever Group Rickettsial Infection Research Articles

Evaluation of a mimotope of the Rickettsia outer membrane protein A (OmpA) as an antigen in enzyme-linked immunosorbent assay to detect rickettsiosis in capybaras (Hydrochoerus hydrochaeris), horses (Equus caballus), and opossums (Didelphis sp.).

Rickettsia rickettsii is the etiological agent of Rocky Mountain spotted fever, which is an important tick-borne zoonosis and, in Brazil, it causes Brazilian spotted fever, which has high lethality rate. This study aimed to evaluate a synthetic peptide corresponding to a segment of the outer membrane protein A (OmpA) as an antigen in a serological test for the diagnosis of rickettsial infections. The amino acid sequence of the peptide was selected by predicting B cell epitopes using B Cell Epitope Prediction (Immune Epitope Database and Analysis Resource) and Epitopia and OmpA sequences of Rickettsia rickettsii strain 'Brazil' and Rickettsia parkeri strains 'Maculatum 20' and 'Portsmouth'. A peptide with amino acid sequence common to both Rickettsia species was synthesized and arbitrarily named OmpA-pLMC. To evaluate this peptide in enzyme-linked immunosorbent assay (ELISA), serum samples of capybara (Hydrochoerus hydrochaeris), horse (Equus caballus), and opossum (Didelphis albiventris) that had been previously tested by indirect immunofluorescence assay (IFA) for rickettsial infection were separated into IFA-positive and IFA-negative groups and used in the assay. There were no significant differences in ELISA optical density (OD) values between IFA-positive and IFA-negative groups with horse samples. The mean OD values were significantly higher in the IFA-positive capybara serum samples (IFA-pos vs. IFA-neg = 2.389 ± 0.761 vs. 1.760 ± 0.840). However, receiver operating characteristic (ROC) curve analysis did not show significant diagnostic parameters. On the other hand, 12 out of 14 (85.7%) opossum samples of the IFA-positive group showed reactivity in ELISA, and this was significantly higher than of the IFA-negative group (0.7196 ± 0.440 vs. 0.2318 ± 0.098, respectively; 85.7% sensitivity, 100% specificity). Therefore, our results show that OmpA-pLMC has a potential to be used in immunodiagnostic assays to detect spotted fever group rickettsial infections.

Clinical characteristics of and antibody response to spotted fever group rickettsial infections in South India: Case series and serological cohort study.

The clinical and serological characteristics of spotted fever group rickettsial (SFGR) infections in South Asia are poorly understood. We studied the clinical presentation and the IgM/IgG response in cases enrolled at two health care centres in South India. We enrolled 77 patients. Fifty-seven of these patients were recruited at a tertiary care centre, the remaining 20 at a community hospital (secondary care level). Diagnostic tests included IgM and IgG enzyme-linked immunosorbent assay and polymerase chain reaction. Over a period of 1year, 41 cases were followed up for repeated sero-analysis. Median age was 9years (range 1-79). A rash was present in 74% of cases (57/77). In cases aged <15years, rash was present in 94% (44/47) vs. 43% (13/30) in cases aged ≥15years. An eschar was found in two cases (3%). Severe infection or complications occurred in 10 cases (13%). These included central nervous system infection (6/77, 8%), kidney injury (3/77, 4%), shock (3/77, 4%), lung involvement (2/77, 3%) and peripheral gangrene (2/77, 3%). IgM antibody levels increased faster after fever onset than IgG antibodies, peaking at 50 and 60days, respectively. After the peak, IgM and IgG levels showed a slow decline over one year with less than 50% of cases showing persistent IgG antibody levels. Spotted fever group rickettsial infections in South India may be under-diagnosed, as many cases may not develop a rash. The proportion of cases developing severe infection seems lower than for scrub typhus in this region. IgG seroprevalence may substantially underestimate the proportion in a population with past SFGR infection.

Spotted fever group rickettsial infection in dogs and their ticks from domestic-wildlife interface areas in southeastern Brazil.

Rickettsia rickettsii is the causative agent of Brazilian spotted fever (BSF), for which humans and dogs are both susceptible. Dogs are sentinels in serological surveys, however, canine disease is rarely reported. Therefore, we aimed to evaluate natural infection by spotted fever group (SFG) Rickettsia spp. in dogs and ticks collected from domiciles close to forest fragments, featuring domestic-wildlife interface areas. Samples from 115 dogs and 135 ixodids were assessed by polymerase chain reactions (PCR) targeting the gltA gene for Rickettsia spp. and the ompA gene for the SFG rickettsial species. One dog (0.87%; 1/115) was positive for R. rickettsii. This dog presented nonspecific laboratory and clinical abnormalities (thrombocytopenia, hyperproteinemia, lymph node enlargement, emaciation, anorexia, and lethargy). Rickettsia parkeri was identified in 2.96% (4/135) of the ticks (Amblyomma sculptum, A. aureolatum, and Rhipicephalus sanguineus). This study confirmed the presence of SFG bacteria in non-endemic and preserved locations, where domestic and wild populations interact. We reinforce the fact that the dog is susceptible to natural R. rickettsii infection. Although this is a rare finding, preventive measures should be taken against BSF in the studied areas. Finally, R. parkeri infection is possibly being demonstrated in A. sculptum for the first time.

Serological Evidence of Spotted Fever Group Rickettsial infection in North Karnataka Region

Background: Rickettsial diseases are important reoccurring infections that mostly go unnoticed or misdiagnosed due to low manifestation, non specific signs, symptoms and absence of widely available sensitive and specific tests. Failure of timely diagnosis leads to significant morbidity and mortality. Though the disease is rampant throughout the world, only few case reports and studies have been reported from only some states of India in the past 15-20 yrs. Aim and Objectives: To demonstrate the serological evidence for the existence of Spotted fever group Rickettsial infections in North Karnataka region and to develop a preliminary understanding of the distribution of these infections. Materials and Methods: During the period of 2015-16, a total of 231 patients sample presenting with consistent fever of more than 8 days, headache, myalgia, rashes and eschar were examined for Rickettsial infections by Weil Felix agglutination test. Further all the WF positive samples were screened for corresponding antibodies to SFG R. conorii by specific serological test IgM/ IgG ELISA. Results obtained with both the methods were tabulated. Results: Out of 231 cases, 105 samples showed agglutinins with Weil Felix antigens. 84 (36.36%) samples had titres ranging from 1:80 to 1:320 with OX2 antigen alone, 5 (2.16%) samples had titres of 1:80 and above for OX19 antigen and 16 (6.92%) samples had titres of 1:80 and above with both OX2 AND OX19 antigens. In R. conorii specific IgM ELISA 27 (25.7%) samples were positive with index >11 and 4 samples had equivocal index value. 74 samples were negative for R. conorii specific antibodies by ELISA. Conclusion: Findings of our study clearly demonstrated that among Rickettsial infections, SFG R. conorii infection seems to be common infection in and around Vijayapur. Inclusion of specific IgM ELISA method in routine diagnostic course is highly necessary for the proper treatment and patient management.

Molecular and serological evidence of flea-associated typhus group and spotted fever group rickettsial infections in Madagascar

BackgroundRickettsiae are obligate intracellular bacteria responsible for many febrile syndromes around the world, including in sub-Saharan Africa. Vectors of these pathogens include ticks, lice, mites and fleas. In order to assess exposure to flea-associated Rickettsia species in Madagascar, human and small mammal samples from an urban and a rural area, and their associated fleas were tested.ResultsAnti-typhus group (TGR)- and anti-spotted fever group rickettsiae (SFGR)-specific IgG were detected in 24 (39%) and 21 (34%) of 62 human serum samples, respectively, using indirect ELISAs, with six individuals seropositive for both. Only two (2%) Rattus rattus out of 86 small mammals presented antibodies against TGR. Out of 117 fleas collected from small mammals, Rickettsia typhi, a TGR, was detected in 26 Xenopsylla cheopis (24%) collected from rodents of an urban area (n = 107), while two of these urban X. cheopis (2%) were positive for Rickettsia felis, a SFGR. R. felis DNA was also detected in eight (31%) out of 26 Pulex irritans fleas.ConclusionsThe general population in Madagascar are exposed to rickettsiae, and two flea-associated Rickettsia pathogens, R. typhi and R. felis, are present near or in homes. Although our results are from a single district, they demonstrate that rickettsiae should be considered as potential agents of undifferentiated fever in Madagascar.

Vigilância de ambientes da febre maculosa: explorando as áreas silenciosas do Brasil

This study described the interventions in quiet areas of Brazil, from the aspect of health promotion. The areas were evaluated from 2014 to 2015, including the following Federal Units: Mato Grosso do Sul, Alagoas, Pernambuco, Rondonia, Roraima, Rio Grande do Norte and Maranhao. Data on surveillance spotted fever were evaluated by notification forms available in the Notifiable Diseases Information System (SINAN), as well as vectors and the spotted fever group rickettsial infections (SFGR). A total of 1,528 vectors were collected from ten different species, whose the highest diversity was observed in Rondonia. In this study, 85% of States which were investigated showed SFGR in vectors or human, and Mato Grosso do Sul, Rondonia and Pernambuco were the most prevalent ones. The results showed the necessity of ongoing training of health and environment professionals in order to improve data about the presence of Rocky Mountain spotted fever among us.

Spotted fever group rickettsia in ticks infesting humans, wild and domesticated animals of Sri Lanka: one health approach

Spotted fever group rickettsial infections are considered an emerging infectious disease in Sri Lanka. The present study examined the potential role of tick vectors carrying the infection from sylvatic reservoirs to humans via domesticated animals. Ticks infesting humans, dogs and wild animals were collected island-wide and were identified. Presence of spotted fever group rickettsia in the tick blood meal was determined using PCR in a sub-sample of ticks collected. A total of 30,933 ticks were collected from 30 different hosts and free living stages from the ground. The collection consisted of 25 tick species recording 12 species from humans, 19 from domesticated animals and 22 from wild animals. Of the total collection randomly selected a sub-sample of 80 ticks were used to identify rickettsia pathogens. This comprised of fifty ticks from 50 wild animals belonged to 15 species (wild boar, pangolin, porcupine, barking deer, star tortoise, mouse deer, samber, spotted deer, monkey, civet cat, bandicoot, elephant, fishing cat, rabbit, flying squirrel; and 20 ticks from 15 dogs especially from areas where spotted fever cases were reported and 10 ticks from 10 humans. Results showed that rickettsial infections were found in four tick species, Amblyomma testudinarium collected from a wild boar, Riphicephalus sanguineus from a dog, Amblyomma clypeolatum from a star tortoise and Amblyomma javanense from a pangolin. Except for A. javanense, other three tick species are generalists infesting humans as well as domestic and wild animals. There is a high potential that these infections can spread easily to humans via the domesticated animals. This is the first report of ticks infesting domesticated and wild animals carrying spotted fever rikettsia and it underscores the possibility of spread of infection from wild reservoirs to human in the animal/human health interface.

Comparative value of blood and skin samples for diagnosis of spotted fever group rickettsial infection in model animals

The definitive diagnosis of spotted fever group (SFG) rickettsioses in humans is challenging due to the retrospective nature and cross reactivity of the serological methods and the absence of reliable and consistent samples for molecular diagnostics. Existing data indicate the transient character of bacteremia in experimentally infected animals. The ability of arthropod vectors to acquire rickettsial infection from the laboratory animals in the absence of systemic infection and known tropism of rickettsial agents to endothelial cells of peripheral blood vessels underline the importance of local infection and consequently the diagnostic potential of skin samples. In order to evaluate the diagnostic sensitivity of rickettsial DNA detection in blood and skin samples, we compared results of PCR testing in parallel samples collected from model laboratory animals infected with Rickettsia rickettsii, Rickettsia parkeri and Rickettsia slovaca-like agent at different time points after infection. Skin samples were collected from ears – away from the site of tick placement and without eschars. Overall, testing of skin samples resulted in a higher proportion of positive results than testing of blood samples. Presented data from model animals demonstrates that testing of skin samples from sites of rickettsial proliferation can provide definitive molecular diagnosis of up to 60–70% of tick-borne SFG rickettsial infections during the acute stage of illness. Detection of pathogen DNA in cutaneous samples is a valuable alternative to blood-PCR at least in model animals.

Compartmentalized, functional role of angiogenin during spotted fever group rickettsia-induced endothelial barrier dysfunction: evidence of possible mediation by host tRNA-derived small noncoding RNAs

BackgroundMicrovascular endothelial barrier dysfunction is the central enigma in spotted fever group (SFG) rickettsioses. Angiogenin (ANG) is one of the earliest identified angiogenic factors, of which some are relevant to the phosphorylation of VE-cadherins that serve as endothelial adherens proteins. Although exogenous ANG is known to translocate into the nucleus of growing endothelial cells (ECs) where it plays a functional role, nuclear ANG is not detected in quiescent ECs. Besides its nuclear role, ANG is thought to play a cytoplasmic role, owing to its RNase activity that cleaves tRNA to produce small RNAs. Recently, such tRNA-derived RNA fragments (tRFs) have been shown to be induced under stress conditions. All these observations raise an intriguing hypothesis about a novel cytoplasmic role of ANG, which is induced upon infection with Rickettsia and generates tRFs that may play roles in SFG rickettsioses.MethodsC3H/HeN mice were infected intravenously with a sublethal dose of R. conorii. At days 1, 3, and 5 post infection (p.i.), liver, lung and brain were collected for immunofluorescence (IF) studies of R. conorii and angiogenin (ANG). Human umbilical vein endothelial cells (HUVECs) were infected with R. conorii for 24, 48, and 72 hrs before incubation with 1μg/ml recombinant human ANG (rANG) in normal medium for 2 hrs. HUVEC samples were subjected to IF, exogenous ANG translocation, endothelial permeability, and immunoprecipitation phosphorylation assays. To identify small non-coding RNAs (sncRNAs) upon rickettsial infection, RNAs from pulverized mouse lung tissues and HUVECs were subjected to library preparation and deep sequencing analysis using an Illumina 2000 instrument. Identified sncRNAs were confirmed by Northern hybridization, and their target mRNAs were predicted in silico using BLAST and RNA hybrid programs.ResultsIn the present study, we have demonstrated endothelial up-regulation of ANG, co-localized with SFG rickettsial infection in vivo. We also have provided direct evidence that rickettsial infection sensitizes human ECs to the translocation of exogenous ANG in a compartmentalized pattern at different times post-infection. Typically, exogenous ANG translocates into the nucleus at 24 hrs and to the cytoplasm at 72 hrs post-infection. The ANG cytoplasmic translocation enhances phosphorylation and destabilization of VE-cadherin and attenuates endothelial barrier function. Of note, deep sequencing analysis detected tRFs, mostly derived from the 5'-halves of host tRNAs, that are induced by ANG. Northern hybridization validates the two most abundantly cloned tRFs derived from tRNA-ValGTG and tRNA-GlyGCC, in both mouse tissues and human cells. Bioinformatics analysis predicted that these tRFs may interact with transcripts associated with the endothelial barrier, the host cell inflammatory response, and autophagy.ConclusionsOur data provide new insight into the role of compartmentalized ANG during SFG rickettsioses, and highlight its possible mediation through tRFs.

Rickettsiae Induce Microvascular Hyperpermeability via Phosphorylation of VE-Cadherins: Evidence from Atomic Force Microscopy and Biochemical Studies

The most prominent pathophysiological effect of spotted fever group (SFG) rickettsial infection of microvascular endothelial cells (ECs) is an enhanced vascular permeability, promoting vasogenic cerebral edema and non-cardiogenic pulmonary edema, which are responsible for most of the morbidity and mortality in severe cases. To date, the cellular and molecular mechanisms by which SFG Rickettsia increase EC permeability are largely unknown. In the present study we used atomic force microscopy (AFM) to study the interactive forces between vascular endothelial (VE)-cadherin and human cerebral microvascular EC infected with R. montanensis, which is genetically similar to R. rickettsii and R. conorii, and displays a similar ability to invade cells, but is non-pathogenic and can be experimentally manipulated under Biosafety Level 2 (BSL2) conditions. We found that infected ECs show a significant decrease in VE-cadherin-EC interactions. In addition, we applied immunofluorescent staining, immunoprecipitation phosphorylation assay, and an in vitro endothelial permeability assay to study the biochemical mechanisms that may participate in the enhanced vascular permeability as an underlying pathologic alteration of SFG rickettsial infection. A major finding is that infection of R. montanensis significantly activated tyrosine phosphorylation of VE-cadherin beginning at 48 hr and reaching a peak at 72 hr p.i. In vitro permeability assay showed an enhanced microvascular permeability at 72 hr p.i. On the other hand, AFM experiments showed a dramatic reduction in VE-cadherin-EC interactive forces at 48 hr p.i. We conclude that upon infection by SFG rickettsiae, phosphorylation of VE-cadherin directly attenuates homophilic protein–protein interactions at the endothelial adherens junctions, and may lead to endothelial paracellular barrier dysfunction causing microvascular hyperpermeability. These new approaches should prove useful in characterizing the antigenically related SFG rickettsiae R. conorii and R. rickettsii in a BSL3 environment. Future studies may lead to the development of new therapeutic strategies to inhibit the VE-cadherin-associated microvascular hyperpermeability in SFG rickettsioses.

Molecular evidence of Rickettsia felis infection in dogs from northern territory, Australia

The prevalence of spotted fever group rickettsial infection in dogs from a remote indigenous community in the Northern Territory (NT) was determined using molecular tools. Blood samples collected from 130 dogs in the community of Maningrida were subjected to a spotted fever group (SFG)-specific PCR targeting the ompB gene followed by a Rickettsia felis-specific PCR targeting the gltA gene of R. felis. Rickettsia felis ompB and gltA genes were amplified from the blood of 3 dogs. This study is the first report of R. felis infection in indigenous community dogs in NT.

Identification of potential hosts and vectors of scrub typhus and tick-borne spotted fever group rickettsiae in eastern Taiwan

Scrub typhus and tick-borne spotted fever group (SFG) rickettsioses are transmitted by chiggers (larval trombiculid mites) and hard ticks, respectively. We assessed exposure to these disease vectors by extensively sampling both chiggers and ticks and their small mammal hosts in eastern Taiwan during 2007 and 2008. The striped field mouse Apodemus agrarius Pallas (Rodentia: Muridae) was the most common of the small mammals (36.1% of 1393 captures) and presented the highest rate of infestation with both chiggers (47.8% of 110 760) and ticks (78.1% of 1431). Leptotrombidium imphalum Vercammen-Grandjean & Langston (Trombidiformes: Trombiculidae) and immature Rhipicephalus haemaphysaloides Supino (Ixodida: Ixodidae) were the most abundant chiggers (84.5%) and ticks (>99%) identified, respectively. Immunofluorescent antibody assay revealed high seropositive rates of rodents against Orientia tsutsugamushi Hyashi (Rickettsiales: Rickettsiaceae), the aetiological agent of scrub typhus (70.0% of 437 rodents), and tick-borne SFG rickettsiae (91.9% of 418 rodents). The current study represents a first step towards elucidating the potential hosts and vectors in the enzootic transmission of O. tsutsugamushi and tick-borne SFG rickettsiae in Taiwan. Further studies should focus on characterizing pathogens in L. imphalum and R. haemaphysaloides, as well as the proclivity of both vectors to humans. Uncovering the main hosts of adult ticks is also critical for the prevention of SFG rickettsial infections.

Survey of tick fauna possessing the ability to act as vectors of rickettsiosis in Toyama Prefecture, Japan

During 1991-2007 a total of 3,562 ixodid ticks were collected by flagging at altitudes from 20 to 1,470m in Toyama Prefecture. Two genera and nine species were identified as follows: Haemaphysalis flava, H. japonica, H. kitaokai, H. longicornis, H. megaspinosa, Ixodes monospinosus, I. nipponensis, I. ovatus, and I. persulcatus. Ixodes ovatus was the most dominant species at elevations of 400m and above, but was also distributed at the low altitudes. Haemaphysalis flava was predominant below 401m above sea level. Haemaphysalis kitaokai, H. megaspinosa, and I. monospinosus were newly recorded in Toyama Prefecture. Rickettsial DNA detected from I. monospinosus was closely related to Rickettsia helvetica, indicating a potential threat of spotted fever group rickettsial infection in Toyama Prefecture.

Severe Spotted Fever Group Rickettsiosis, Australia

We report 3 cases of spotted fever group rickettsial infection (presumed Queensland tick typhus) in residents of northern Queensland, Australia, who had unusually severe clinical manifestations. Complications included renal failure, purpura fulminans, and severe pneumonia. Clinical illness caused by Rickettsia australis may not be as benign as previously described.

Identification of Rickettsiae, Uganda and Djibouti

To the Editor: Tickborne rickettsioses are caused by obligate intracellular gram-negative bacteria that belong to the spotted fever group of the genus Rickettsia. These zoonoses share characteristic clinical features, including fever, headache, rash, and sometimes eschar formation at the site of the bite (1). Although rickettsioses are important emerging vectorborne infections of humans worldwide, little is known about rickettsioses in sub-Saharan Africa (1,2). In 2002, 94 ticks were collected in Djibouti: 5 Amblyomma lepidum, 1 A. variegatum, 5 Hyalomma marginatum rufipes, 40 Rhipicephalus pulchellus, and 10 Rh. evertsi evertsi from cattle that had just arrived from Ethiopia; 30 H. dromedarii from dromedaries; and 3 Rh. sanguineus group ticks from cheetahs. In 2003, 57 ticks were collected from dogs in Kampala, Uganda: 1 A. variegatum, 9 Haemaphysalis punctaleachi, 28 Rh. praetextatus, and 19 Rh. sanguineus. All ticks were partially or fully engorged adults. This convenience sample of ticks was obtained as part of other ongoing studies. Ticks were identified by using taxonomic keys (3) and kept in 70% ethanol before being tested. DNA of each tick was extracted, and rickettsial DNA was detected by PCR that used primers Rp.877p and Rp.1258r, which amplify a 396-bp fragment of the citrate synthase gene (gltA) of rickettsia, as described (4). Rickettsia-positive samples were tested by a second PCR that used Rr.190.70p and Rr.190.701n primers, which amplify a 629–632 bp fragment of ompA gene (4). Controls (2 negative [DNA extracted from noninfected laboratory ticks and distilled water] and 1 positive [R. montanensis DNA]) were included in each test. The sequences of PCR products were obtained and compared with those available in GenBank (4). One specimen of Ha. punctaleachi from Uganda and 1 A. lepidum from Djibouti, as well as positive controls, were positive according to PCR using both primer pairs. No signal was obtained from negative controls. The sequence of a 474-bp fragment of ompA obtained from Ha. punctaleachi showed 99.8% (473/474) similarity with R. conorii (GenBank accession no. {type:entrez-nucleotide,attrs:{text:AY346453,term_id:76152011}}AY346453); those of a 340-bp segment of gltA showed 100% similarity with that of R. conorii ({type:entrez-nucleotide,attrs:{text:AE008677,term_id:25307999}}AE008677). The sequences of a 517-bp segment of ompA and a 341-bp segment of gltA amplified from A. lepidum showed 100% similarity to the corresponding sequences of R. africae ({type:entrez-nucleotide,attrs:{text:U83436,term_id:62861416}}U83436 and {type:entrez-nucleotide,attrs:{text:U59733,term_id:1389980}}U59733, respectively). To our knowledge, this is the first detection of R. conorii, the agent of Mediterranean spotted fever, in Uganda. Although the main vector of this rickettsia is Rh. sanguineus, the few ticks of this species we tested were negative (1). It is also the first detection of R. conorii in Ha. punctaleachi, although it has been detected in the closely related Ha. leachi in Zimbabwe (5). Ha. punctaleachi prefers warm and humid conditions but can exist wherever rodent hosts for its immature stages and canine hosts for its adult stages are present (6). Adults are found throughout the year; peak numbers occur either from winter to early summer or from spring to late summer (7). Although the detection of R. conorii in Ha. punctaleachi does not mean that this tick is an efficient vector (8), clinicians in Uganda should be aware of the presence of Mediterranean spotted fever in their country. This is also, to our knowledge, the first detection of R. africae, the agent of African tick bite fever, in Djibouti. R. africae was also detected in 1 A. lepidum collected in Sudan (4), but it is more frequently detected in A. variegatum and A. hebraeum with high infection rates throughout sub-Saharan Africa (7). A. lepidum, which coexists with A. variegatum in limited locations, is chiefly a cattle parasite. It will also attach to smaller domestic animals and a few wild herbivores, but it attacks humans less frequently than A. variegatum or A. hebraeum. A. lepidum occurs in a variety of climatic regions but most commonly inhabits semiarid regions in eastern Africa. The cattle in our study had been imported from Ethiopia, and the ticks may have infested these animals before their arrival in Djibouti. Indeed, in 1973 Burgdorfer obtained an isolate from A. variegatum in Ethiopia, which was thereafter shown to be indistinguishable from the rickettsia described as R. africae (7,9). Again, clinicians should be aware of the presence of R. africae in Djibouti and that it could affect their patients, both local and international, including French and American soldiers based in this country (10). Because we did not do systematic sampling, our results cannot address the prevalence and distribution of R. conorii and R. africae in Uganda and Djibouti, respectively. However, healthcare workers who treat persons who live in or have traveled to these countries should be alert for spotted fever group rickettsial infections in their patients (1).

Spotted Fever Group Rickettsial Infection in Dogs from Eastern Arizona

A serosurvey of free-roaming dogs for antibodies to spotted fever group rickettsiae was conducted using archival samples that had been collected in the White Mountain region of eastern Arizona during a plague study in 1996. Immunoglobulin G antibodies to Rickettsia rickettsii (5.1%) and to R. rhipicephali (3.6%) were demonstrated, and no cross-reactive samples were identified. This study indicates that R. rickettsii was likely present in the dog populations in this area prior to the recognition of human cases of Rocky Mountain spotted fever (RMSF). The role of dogs as short-term reservoirs and primary hosts for the vector tick, Rhipicephalus sanguineus, should receive closer attention.

Not only ‘Flinders Island’ spotted fever

To demonstrate that Flinders Island spotted fever (FISF), a spotted fever group rickettsial infection caused by Rickettsia honei, is found not only on Flinders Island (Bass Strait), Tasmania, but elsewhere in south-east Australia. Cases of FISF were identified by rickettsial serology, culture and the detection of rickettsial DNA via PCR. Isolates and PCR products were sequenced to identify the aetiological agent as R. honei. Three new cases of FISF were detected outside of Flinders Island. One on Schouten Island, south of the Freycinet Peninsula, Tasmania, and two in south-eastern South Australia (McLaren Vale and Goolwa). These cases show that FISF extends beyond Flinders Island and most likely has the same distribution across south-east Australia as its vector, the reptile tick Aponomma hydrosauri. FISF should be considered as a differential diagnosis in patients from south-eastern Australia presenting with fever, headache and rash following a tick bite.

Human Spotted Fever Rickettsial Infections

Serum specimens from patients at 4 sites in Peru were tested for evidence of spotted fever group rickettsial infection. Results showed that 30 (18%) of 170 patients had spotted fever group rickettsial infections, which likely caused their illnesses. These findings document laboratory-confirmed spotted fever from diverse areas of Peru.

EVIDENCE OF RICKETTSIAL AND LEPTOSPIRA INFECTIONS IN ANDEAN NORTHERN PERU

Between May and October 2002, a cluster of acute febrile illnesses occurred in the subtropical Andean foothills of Peru. Serologic evidence in villages where disease had been documented showed that the prevalence of IgM antibody to Leptospira ranged from 6% to 52%, that of IgM antibody to spotted fever group (SFG) rickettsia ranged from 10% to 19%, and that of IgM antibody to Coxiella burnetii from 1% to 15%. Measurement of IgG antibodies for SFG rickettsiae suggested that this disease was endemic. In contrast, IgG antibodies against C. burnetii were largely absent. In humans, microagglutination tests identified pathogenic variants of Leptospira. The presence of an SFG rickettsial infection was confirmed in four febrile patients following polymerase chain reaction and sequencing of the conserved 17-kD common antigen gene (htrA). Collectively, these analyses indicated that Rickettsia sp., C. burnetii, and Leptospira sp. were circulating in the region during the time of disease outbreak and implicate the involvement of an as yet undetermined SFG rickettsia in northwestern Peru.

Characterization of spotted fever group rickettsiae detected in dogs and ticks in Okinawa, Japan.

Spotted fever group (SFG) rickettsial DNAs were detected in 2.4% of 340 canine blood samples and a pool of 84 tick pool samples (229 ticks) collected in Okinawa, Japan by PCR using a citrate synthase and an SFG rickettsial 190-kDa surface antigen gene primer pair. The sequences of both genes from canine blood and tick samples showed high levels of similarity with those of Rickettsiajaponica and several SFG rickettsiae (R. aeschlimannii, R. massiliae, R. rhipicephali and Bar-29 strain). Phylogenesis of canine blood and tick samples was closely related to that of reference SFG rickettsiae. Serological evidence of SFG rickettsial infection in dogs and humans in Okinawa, where no clinical human cases have been reported, has been obtained. In this study, genetical characterization of SFG rickettsia in Okinawa was investigated phylogenetically.