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Didier Raoult - One of the best experts on this subject based on the ideXlab platform.
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reply to slesak et al so much about Rickettsia Felis infection to be discovered
Proceedings of the National Academy of Sciences of the United States of America, 2015Co-Authors: Philippe Parola, Constentin Dieme, Oleg Mediannikov, Didier RaoultAbstract:We read with great interest the comment by Slesak et al. (1) on our work (2), and agree that the number of animals, including leeches and arthropods, playing a role in the transmission of Rickettsia Felis might be greater than previously suspected. In the Slesak et al. (1) report, the leech that had bitten the patient diagnosed with R. Felis infection had not been kept to be tested by PCR, which would have provided a stronger argument for the case. An experimental model would be needed to support the potential role of leeches in the transmission of R. Felis, which has never been detected in these animals. Furthermore, it is necessary to discuss one method of transmission missing in this current case report. We suggest that R. Felis might have been already present on the skin of the patient and then have been inoculated by the bite of the leech or by scratching after the bite.
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two human cases of Rickettsia Felis infection thailand
Emerging Infectious Diseases, 2014Co-Authors: Sophie Edouard, Philippe Parola, Saithip Bhengsri, Scott F Dowell, George Watt, Didier RaoultAbstract:To the Editor: Rickettsia Felis is an emerging pathogen responsible for fleaborne spotted fever. This new species was first isolated in 2002 from the cat flea, Ctenocephalides Felis, which was then identified as the main vector of this Rickettsia (1). R. Felis has also been described in other flea, tick, chigger, and mite species (2) and more recently, in mosquitoes, which are strongly suspected to play a role in transmission of the bacterium (3,4). The first evidence of human pathogenicity of R. Felis was suspected in a patient from Texas, USA, in 1991 and was confirmed by 3 additional case-patients from Mexico in 2000 (5). Evidence suggests that this bacterium has a worldwide distribution; ≈100 reports of human cases have been published (2,6). Moreover, R. Felis was identified as a common (3%–15%) cause of fever among febrile patients in tropical Africa (7). The bacterium has also been described in Asia, but little is known about cases of infection in humans; only 1 human case was described in Thailand in 2003 (8). We enrolled febrile patients (≥7 years of age) who came to 4 community hospitals, 2 in Chiang Rai (northern Thailand) and 2 in Khon Kaen (northeastern Thailand) during 2002–2005. Acute-phase and convalescent-phase (3–5 weeks later) serum samples were obtained from 2,225 patients and tested for R. Felis by using an indirect immunofluorescence assay (9). Seventeen (0.8%) of 2,225 patients showed evidence of seroconversion (IgG titer ≥1:128 or IgM titer ≥1:64 or a ≥4-fold increase in titer). Specific real-time PCR (qPCR) for R. Felis was performed with acute-phase serum samples of these patients with primers and probes specific for orfB and vapB1 genes as described (7). DNA was extracted by using the Biorobot EZ1 Workstation (QIAGEN, Courtaboeuf, France), and qPCR was performed by using a CFX96 instrument (Bio-Rad, Marne-la-Coquette, France). DNA from R. Felis strain URRWFXCalT (1) was used as a positive control, and sterile water was used a negative control. The qPCR results were positive (cycle threshold ≤35) for the 2 genes for 2 of the 17 patients; the four 150-bp amplicons were sequenced. Sequences of orfB (150/150) and VapB1 (155/155) showed 100% similarity with the sequence from the complete genome of R. Felis URRWXCALT (GenBank accession no. {"type":"entrez-nucleotide","attrs":{"text":"CP000053","term_id":"67003925","term_text":"CP000053"}}CP000053). Patient 1, a 20-year-old woman, and patient 2, a 45-year-old man, were from Chiang Rai Province. They both had fever, myalgia, arthralgia, headache, abdominal pain, cough, and chest pain. No rashes, eschars, or lymphadenopathies were noted. In addition, patient 2 had photophobia, had vomited, and reported contact with cats. Both patients reported having contact with others animals and being bitten by insects, including mosquitoes (Table). Table Characteristics of 2 febrile patients with confirmed Rickettsia Felis infection, Chiang Rai Province, Thailand* R. Felis DNA was detected in serum samples from these 2 patients with acute febrile illness in Thailand. The immunofluorescent assay, the reference serologic method for diagnosis of infection with Rickettsia spp., is known to show cross-reactivity with other Rickettsia spp. Therefore, diagnosis of Rickettsial infection should be confirmed by Western blotting or molecular testing. Real-time PCRs are increasingly being used for diagnosis of rickettsioses, including those with R. Felis, and for vector and reservoir identification (2). The predominant rickettsioses reported in Asia are murine typhus and scrub typhus, which are caused by R. typhi and Orientia tsutsugamushi, respectively (8). To the best of our knowledge, only 12 human cases of R. Felis infection have been reported in Asia: 3 in Thailand (including these cases), 3 in Sri Lanka, 1 in Laos, 1 in Israel, 1 in Taiwan, and 3 in South Korea (2,8–10). The prevalence of R. Felis in fleas has been well studied in >20 countries, including Japan, Thailand, Indonesia, Laos, Taiwan, Israel, Afghanistan, and Lebanon (2). This bacterium has also been described in mites in Taiwan and South Korea, in chiggers in South Korea, and in ticks in Japan (2,9,10). The clinical signs and symptoms of R. Felis infection are now better understood. The more frequent clinical findings reported are nonspecific and include fever, asthenia, headache, maculopapular rash, and inoculation eschar. Neurologic, digestive, and respiratory symptoms are not commonly reported (2). These infections could be confused with other rickettsioses or other febrile illnesses, such as malaria. In most regions, laboratory tests are unavailable; consequently, R. Felis infections are largely underdiagnosed. The findings of this study indicate that R. Felis infections may be among the causes of febrile illness in Thailand and highlight the need for physicians to consider this pathogen in the differential diagnosis of diseases in tropical countries and in travelers. Further studies are needed to ascertain risk factors and confirm the causal association and pathology of fleaborne spotted fever in Asia.
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Rickettsia Felis and related bacteria an epidemiological enigma
International Journal of Infectious Diseases, 2014Co-Authors: Oleg Mediannikov, Hubert Bassene, M Aubadie, Didier RaoultAbstract:Background: Recent works identified a novel healthcare problem in Africa: acute Rickettsia Felis-induced fever that mimics malaria. The epidemiology of these diseases remains to be characterized. Indeed, the natural reservoirs of R. Felis are not known. Since the first clinical descriptions of R. Felis-associated fever, the cat and dog fleas Ctenocephalides Felis and C. canis were implicated as themost probable vectors inmany countries, but not in Senegal. Methods & Materials: Arthropods (ticks, mites, fleas, tsetse flies, biting midges, mosquitoes, bed bugs) and environmental samples (dust and water samples) were collected in the villages of Dielmo and Ndiop where R. Felis-associated acute fevers contribute up to 8% of all acute fevers with the incidence of 6.7 per 100 person-years. DNA extracted from all samples was tested by Rickettsia genus-specific qPCR and by two different R. Felis-specific qPCR. Positive environmental samples were subjected to PCR with the universal eukaryotic cytochrome oxydase I-based primers followedbycloningof theampliconswithpGemvectors. Isolationwas performed in XTC cell line using the shell-vial technique. Characterization of the isolated strainswas done by sequencing of gltA and 16S rRNA genes. Results: Arthropods (ticks, mites, fleas, tsetse flies, biting midges, mosquitoes, bed bugs) and environmental samples (dust and water samples) were collected in the villages of Dielmo and Ndiop where R. Felis-associated acute fevers contribute up to 8% of all acute fevers with the incidence of 6.7 per 100 person-years. DNA extracted from all samples was tested by Rickettsia genusspecific qPCR and by two different R. Felis-specific qPCR. Positive environmental samples were subjected to PCR with the universal eukaryotic cytochrome oxydase I (COI)-based primers followed by cloning of the amplicons with pGem vectors. Isolation was performed in XTC cell line using the shell-vial technique. Characterization of the isolated strainswas done by sequencing of gltA and 16S rRNA genes. Conclusion: This is the first evidence of the presence of R. Felis in arthropods in the endemic focus or R. Felis infection in Senegal. The roles of Siteroptidae mites in the hosting and transmission of the R. Felis is to be further investigated
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molecular detection of Rickettsia Felis and bartonella henselae in dog and cat fleas in central oromia ethiopia
American Journal of Tropical Medicine and Hygiene, 2014Co-Authors: Bersissa Kumsa, Didier Raoult, Philippe Parola, Cristina SocolovschiAbstract: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.
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description of yaaf the vesicular fever caused by acute Rickettsia Felis infection in senegal
Journal of Infection, 2013Co-Authors: Oleg Mediannikov, Hubert Bassene, Adama Tall, Jean-françois Trape, Cheikh Sokhna, Florence Fenollar, Didier RaoultAbstract:Rickettsiosis caused by Rickettsia Felis is an emerging infection in Africa and may account for 3-4% of ambulatory febrile fevers. We report herein a case of R. Felis infection, for which we propose the name "yaaf", meaning vesicle, in an 8-month-old girl who was diagnosed in the field by real-time PCR analysis of a skin lesion; these PCR analysis was performed at a local experimental point-of-care laboratory. The clinical presentation was polymorphous skin lesions, including papules, vesicles, erosions and ulcers. The patient did not produce antibodies against Rickettsia. We suggest that this disease may be a primary infection caused by R. Felis.
Kevin R Macaluso - One of the best experts on this subject based on the ideXlab platform.
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Rickettsia Felis: A Review of Transmission Mechanisms of an Emerging Pathogen
MDPI AG, 2017Co-Authors: Kelsey P. Legendre, Kevin R MacalusoAbstract:Rickettsia Felis is an emerging pathogen of the transitional group of Rickettsia species and an important cause of febrile illness in Africa. Since the organism’s original discovery in the early 1990s, much research has been directed towards elucidating transmission mechanisms within the primary host and reservoir, the cat flea (Ctenocephalides Felis). Several mechanisms for vertical and horizontal transmission within this vector have been thoroughly described, as well as transmission to other arthropod vectors, including other species of fleas. However, while a growing number of human cases of flea-borne spotted fever are being reported throughout the world, a definitive transmission mechanism from arthropod host to vertebrate host resulting in disease has not been found. Several possible mechanisms, including bite of infected arthropods and association with infectious arthropod feces, are currently being investigated
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Rickettsia Felis, an Emerging Flea-Borne Rickettsiosis
Current Tropical Medicine Reports, 2016Co-Authors: Lisa D. Brown, Kevin R MacalusoAbstract:Rickettsia Felis is an emerging insect-borne Rickettsial pathogen and the causative agent of flea-borne spotted fever. First described as a human pathogen from the USA in 1991, R. Felis is now identified throughout the world and considered a common cause of fever in Africa. The cosmopolitan distribution of this pathogen is credited to the equally widespread occurrence of cat fleas ( Ctenocephalides Felis ), the primary vector and reservoir of R. Felis . Although R. Felis is a relatively new member of the pathogenic Rickettsia , limited knowledge of basic R. Felis biology continues to hinder research progression of this unique bacterium. This is a comprehensive review examining what is known and unknown relative to R. Felis transmission biology, epidemiology of the disease, and genetics, with an insight into areas of needed investigation.
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genomic diversification in strains of Rickettsia Felis isolated from different arthropods
Genome Biology and Evolution, 2015Co-Authors: Joseph J Gillespie, Abdu F Azad, Timothy P Driscoll, Victoria I Verhoeve, Tadanobu Utsuki, Claudia Husseneder, Vladimir N Chouljenko, Kevin R MacalusoAbstract:Rickettsia Felis (Alphaproteobacteria: Rickettsiales) is the causative agent of an emerging flea-borne rickettsiosis with worldwide occurrence. Originally described from the cat flea, Ctenocephalides Felis, recent reports have identified R. Felis from other flea species, as well as other insects and ticks. This diverse host range for R. Felis may indicate an underlying genetic variability associated with host-specific strains. Accordingly, to determine a potential genetic basis for host specialization, we sequenced the genome of R. Felis str. LSU-Lb, which is an obligate mutualist of the parthenogenic booklouse Liposcelis bostrychophila (Insecta: Psocoptera). We also sequenced the genome of R. Felis str. LSU, the second genome sequence for cat flea-associated strains (cf. R. Felis str. URRWXCal2), which are presumably facultative parasites of fleas. Phylogenomics analysis revealed R. Felis str. LSU-Lb diverged from the flea-associated strains. Unexpectedly, R. Felis str. LSU was found to be divergent from R. Felis str. URRWXCal2, despite sharing similar hosts. Although all three R. Felis genomes contain the pRF plasmid, R. Felis str. LSU-Lb carries an additional unique plasmid, pLbaR (plasmid of L. bostrychophila associated Rickettsia), nearly half of which encodes a unique 23-gene integrative conjugative element. Remarkably, pLbaR also encodes a repeats-in-toxin-like type I secretion system and associated toxin, heretofore unknown from other Rickettsiales genomes, which likely originated from lateral gene transfer with another obligate intracellular parasite of arthropods, Cardinium (Bacteroidetes). Collectively, our study reveals unexpected genomic diversity across three R. Felis strains and identifies several diversifying factors that differentiate facultative parasites of fleas from obligate mutualists of booklice.
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dissemination of bloodmeal acquired Rickettsia Felis in cat fleas ctenocephalides Felis
Parasites & Vectors, 2013Co-Authors: Supanee Hirunkanokpun, Chutima Thepparit, Lane D. Foil, Vsevolod L Popov, Kevin R MacalusoAbstract:Cat fleas, Ctenocephalides Felis, are known biological vectors for Rickettsia Felis. Rickettsial transmission can be vertical via transovarial transmission within a flea population, as well as horizontal between fleas through a bloodmeal. The previously undescribed infection kinetics of bloodmeal-acquired R. Felis in cat fleas provides insight into the R. Felis-flea interaction. In the present study, dissemination of R. Felis in previously uninfected cat fleas fed an R. Felis-infected bloodmeal was investigated. At weekly intervals for 28 days, Rickettsial propagation, accumulation, and dissemination in gut epithelial cells, specifically in the hindgut and the specialized cells in the neck region of midgut, were observed on paraffin sections of infected cat fleas by immunofluorescence assay (IFA) and confirmed by PCR detection of R. Felis 17-kDa antigen gene. IFA results demonstrate ingested Rickettsiae in vacuoles during early infection of the gut; lysosomal activity, indicated by lysosome marker staining of freshly-dissected gut, suggests the presence of phagolysosome-associated vacuoles. Subsequent to infection in the gut, Rickettsiae spread to the hemocoel and other tissues including reproductive organs. Densely-packed Rickettsiae forming mycetome-like structures were observed in the abdomen of infected male cat fleas during late infection. Ultrastructural analysis by transmission electron microscopy (TEM) confirmed the presence and infection characteristics of Rickettsia including Rickettsial destruction in the phagolysosome, Rickettsial division, and accumulation in the flea gut. This study intimately profiles R. Felis dissemination in cat fleas and further illuminates the mechanisms of Rickettsial transmission in nature.
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horizontal transmission of Rickettsia Felis between cat fleas ctenocephalides Felis
Molecular Ecology, 2011Co-Authors: Supanee Hirunkanokpun, Chutima Thepparit, Lane D. Foil, Kevin R MacalusoAbstract:Rickettsia Felis is a Rickettsial pathogen primarily associated with the cat flea, Ctenocephalides Felis. Although laboratory studies have confirmed that R. Felis is maintained by transstadial and transovarial transmission in C. Felis, distinct mechanisms of horizontal transmission of R. Felis among cat fleas are undefined. Based on the inefficient vertical transmission of R. Felis by cat fleas and the detection of R. Felis in a variety of haematophagous arthropods, we hypothesize that R. Felis is horizontally transmitted between cat fleas. Towards testing this hypothesis, flea transmission of R. Felis via a bloodmeal was assessed weekly for 4 weeks. Rhodamine B was used to distinguish uninfected recipient and R. Felis-infected donor fleas in a Rickettsial horizontal transmission bioassay, and quantitative real-time PCR assay was used to measure transmission frequency; immunofluorescence assay also confirmed transmission. Female fleas acquired R. Felis infection more readily than male fleas after feeding on a R. Felis-infected bloodmeal for 24 h (69.3% and 43.3%, respectively) and both Rickettsia-uninfected recipient male and female fleas became infected with R. Felis after cofeeding with R. Felis-infected donor fleas (3.3-40.0%). Distinct bioassays were developed to further determine that R. Felis was transmitted from R. Felis-infected to uninfected fleas during cofeeding and copulation. Vertical transmission of R. Felis by infected fleas was not demonstrated in this study. The demonstration of horizontal transmission of R. Felis between cat fleas has broad implications for the ecology of R. Felis rickettsiosis.
Philippe Parola - One of the best experts on this subject based on the ideXlab platform.
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Rickettsia Felis the complex journey of an emergent human pathogen
Trends in Parasitology, 2016Co-Authors: Emmanouil Angelakis, Oleg Mediannikov, Philippe ParolaAbstract:Rickettsia Felis is an obligate intracellular bacterium that is different from other officially recognized Rickettsial species. It has multiple genes of different origins, an incubation temperature of less than 32°C, and a conjugative plasmid. This Rickettsia is commonly detected in febrile patients in sub-Saharan Africa. R. Felis is frequently detected in cat fleas, but recently mosquitoes have been suspected to be able to transmit the bacterium. However, many aspects of the ecology and epidemiology of R. Felis are not completely understood and remain to be uncovered. We aim here to give an update of the current knowledge about this fascinating organism.
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reply to slesak et al so much about Rickettsia Felis infection to be discovered
Proceedings of the National Academy of Sciences of the United States of America, 2015Co-Authors: Philippe Parola, Constentin Dieme, Oleg Mediannikov, Didier RaoultAbstract:We read with great interest the comment by Slesak et al. (1) on our work (2), and agree that the number of animals, including leeches and arthropods, playing a role in the transmission of Rickettsia Felis might be greater than previously suspected. In the Slesak et al. (1) report, the leech that had bitten the patient diagnosed with R. Felis infection had not been kept to be tested by PCR, which would have provided a stronger argument for the case. An experimental model would be needed to support the potential role of leeches in the transmission of R. Felis, which has never been detected in these animals. Furthermore, it is necessary to discuss one method of transmission missing in this current case report. We suggest that R. Felis might have been already present on the skin of the patient and then have been inoculated by the bite of the leech or by scratching after the bite.
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transmission potential of Rickettsia Felis infection by anopheles gambiae mosquitoes
Proceedings of the National Academy of Sciences of the United States of America, 2015Co-Authors: Constentin Dieme, Gilles Audoly, Yassina Bechah, Cristina Socolovschi, Ousmane Faye, Jean Michel Berenger, Philippe ParolaAbstract:A growing number of recent reports have implicated Rickettsia Felis as a human pathogen, paralleling the increasing detection of R. Felis in arthropod hosts across the globe, primarily in fleas. Here Anopheles gambiae mosquitoes, the primary malarial vectors in sub-Saharan Africa, were fed with either blood meal infected with R. Felis or infected cellular media administered in membrane feeding systems. In addition, a group of mosquitoes was fed on R. Felis-infected BALB/c mice. The acquisition and persistence of R. Felis in mosquitoes was demonstrated by quantitative PCR detection of the bacteria up to day 15 postinfection. R. Felis was detected in mosquito feces up to day 14. Furthermore, R. Felis was visualized by immunofluorescence in salivary glands, in and around the gut, and in the ovaries, although no vertical transmission was observed. R. Felis was also found in the cotton used for sucrose feeding after the mosquitoes were fed infected blood. Natural bites from R. Felis-infected An. gambiae were able to cause transient rickettsemias in mice, indicating that this mosquito species has the potential to be a vector of R. Felis infection. This is particularly important given the recent report of high prevalence of R. Felis infection in patients with “fever of unknown origin” in malaria-endemic areas.
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First molecular detection of Rickettsia Felis in fleas from Algeria. Am J Trop Med Hyg. 2006;74:532–5. Address for correspondence: Jeremie Gilles, Department of Entomology, University of Kentucky, S225 Agricultural Science Center North
2015Co-Authors: Idir Bitam, Philippe Parola, Katharina Dittmar, De La Cruz, Koutaro MatsumotoAbstract:Abstract. Fleas collected in Algeria in the district of Oran between July and September 2003 were tested by polymerase chain reaction for the presence of Rickettsia spp. DNA using primers amplifying gltA and OmpA genes. Two gltA sequences identical to those of an emerging pathogen, Rickettsia Felis, were detected including i) R. Felis California 2 in Ctenocephalides canis from rodents and ii) R. Felis RF2125 in Archeopsylla erinacei from hedgehogs
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two human cases of Rickettsia Felis infection thailand
Emerging Infectious Diseases, 2014Co-Authors: Sophie Edouard, Philippe Parola, Saithip Bhengsri, Scott F Dowell, George Watt, Didier RaoultAbstract:To the Editor: Rickettsia Felis is an emerging pathogen responsible for fleaborne spotted fever. This new species was first isolated in 2002 from the cat flea, Ctenocephalides Felis, which was then identified as the main vector of this Rickettsia (1). R. Felis has also been described in other flea, tick, chigger, and mite species (2) and more recently, in mosquitoes, which are strongly suspected to play a role in transmission of the bacterium (3,4). The first evidence of human pathogenicity of R. Felis was suspected in a patient from Texas, USA, in 1991 and was confirmed by 3 additional case-patients from Mexico in 2000 (5). Evidence suggests that this bacterium has a worldwide distribution; ≈100 reports of human cases have been published (2,6). Moreover, R. Felis was identified as a common (3%–15%) cause of fever among febrile patients in tropical Africa (7). The bacterium has also been described in Asia, but little is known about cases of infection in humans; only 1 human case was described in Thailand in 2003 (8). We enrolled febrile patients (≥7 years of age) who came to 4 community hospitals, 2 in Chiang Rai (northern Thailand) and 2 in Khon Kaen (northeastern Thailand) during 2002–2005. Acute-phase and convalescent-phase (3–5 weeks later) serum samples were obtained from 2,225 patients and tested for R. Felis by using an indirect immunofluorescence assay (9). Seventeen (0.8%) of 2,225 patients showed evidence of seroconversion (IgG titer ≥1:128 or IgM titer ≥1:64 or a ≥4-fold increase in titer). Specific real-time PCR (qPCR) for R. Felis was performed with acute-phase serum samples of these patients with primers and probes specific for orfB and vapB1 genes as described (7). DNA was extracted by using the Biorobot EZ1 Workstation (QIAGEN, Courtaboeuf, France), and qPCR was performed by using a CFX96 instrument (Bio-Rad, Marne-la-Coquette, France). DNA from R. Felis strain URRWFXCalT (1) was used as a positive control, and sterile water was used a negative control. The qPCR results were positive (cycle threshold ≤35) for the 2 genes for 2 of the 17 patients; the four 150-bp amplicons were sequenced. Sequences of orfB (150/150) and VapB1 (155/155) showed 100% similarity with the sequence from the complete genome of R. Felis URRWXCALT (GenBank accession no. {"type":"entrez-nucleotide","attrs":{"text":"CP000053","term_id":"67003925","term_text":"CP000053"}}CP000053). Patient 1, a 20-year-old woman, and patient 2, a 45-year-old man, were from Chiang Rai Province. They both had fever, myalgia, arthralgia, headache, abdominal pain, cough, and chest pain. No rashes, eschars, or lymphadenopathies were noted. In addition, patient 2 had photophobia, had vomited, and reported contact with cats. Both patients reported having contact with others animals and being bitten by insects, including mosquitoes (Table). Table Characteristics of 2 febrile patients with confirmed Rickettsia Felis infection, Chiang Rai Province, Thailand* R. Felis DNA was detected in serum samples from these 2 patients with acute febrile illness in Thailand. The immunofluorescent assay, the reference serologic method for diagnosis of infection with Rickettsia spp., is known to show cross-reactivity with other Rickettsia spp. Therefore, diagnosis of Rickettsial infection should be confirmed by Western blotting or molecular testing. Real-time PCRs are increasingly being used for diagnosis of rickettsioses, including those with R. Felis, and for vector and reservoir identification (2). The predominant rickettsioses reported in Asia are murine typhus and scrub typhus, which are caused by R. typhi and Orientia tsutsugamushi, respectively (8). To the best of our knowledge, only 12 human cases of R. Felis infection have been reported in Asia: 3 in Thailand (including these cases), 3 in Sri Lanka, 1 in Laos, 1 in Israel, 1 in Taiwan, and 3 in South Korea (2,8–10). The prevalence of R. Felis in fleas has been well studied in >20 countries, including Japan, Thailand, Indonesia, Laos, Taiwan, Israel, Afghanistan, and Lebanon (2). This bacterium has also been described in mites in Taiwan and South Korea, in chiggers in South Korea, and in ticks in Japan (2,9,10). The clinical signs and symptoms of R. Felis infection are now better understood. The more frequent clinical findings reported are nonspecific and include fever, asthenia, headache, maculopapular rash, and inoculation eschar. Neurologic, digestive, and respiratory symptoms are not commonly reported (2). These infections could be confused with other rickettsioses or other febrile illnesses, such as malaria. In most regions, laboratory tests are unavailable; consequently, R. Felis infections are largely underdiagnosed. The findings of this study indicate that R. Felis infections may be among the causes of febrile illness in Thailand and highlight the need for physicians to consider this pathogen in the differential diagnosis of diseases in tropical countries and in travelers. Further studies are needed to ascertain risk factors and confirm the causal association and pathology of fleaborne spotted fever in Asia.
Rebecca J Traub - One of the best experts on this subject based on the ideXlab platform.
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the epidemiology of Rickettsia Felis infecting fleas of companion animals in eastern australia
Parasites & Vectors, 2018Co-Authors: Yen Thon Teoh, Sze Fui Hii, Stephen Graves, Robert Rees, John Stenos, Rebecca J TraubAbstract:Flea-borne spotted fever (FBSF) caused by Rickettsia Felis is an arthropod-borne zoonosis. This study aimed to determine the prevalence, primary species and genotype(s) of R. Felis infecting fleas from dogs and cats. All fleas were identified as Ctenocephalides Felis Felis. All Rickettsial DNA detected in fleas was identified as being 100% homologous to R. Felis URRWXCal2, with positivity within tropical, subtropical and temperate regions noted at 6.7%, 13.2% and 15.5%, respectively. Toy/small breed dogs were found to be at a lower odds of harboring R. Felis-positive fleas compared with large breed dogs on univariate analysis, while DMH and pedigree breed cats were at a lower odds compared to DSH cats. Cooler minimum temperature ranges of between 15 to 20 °C and between 8 to 15 °C increased the odds of R. Felis positivity in fleas, as did a constrained maximum temperature range of between 27 to 30 °C on multivariable analysis. Environmental temperature may play a part in influencing R. Felis prevalence and infectivity within its flea host. Regional climatic differences need to be considered when approaching public health risk mitigation strategies for FBSF.
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serological evidence of exposure to Rickettsia Felis and Rickettsia typhi in australian veterinarians
Parasites & Vectors, 2017Co-Authors: Yen Thon Teoh, Sze Fui Hii, Mark Stevenson, Stephen Graves, Robert Rees, John Stenos, Rebecca J TraubAbstract:Background Rickettsia Felis and Rickettsia typhi are emerging arthropod-borne zoonoses causing fever and flu-like symptoms. Seroprevalence and risk factors associated with exposure to these organisms was explored in Australian veterinarians.
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serological evidence of exposure to Rickettsia Felis and Rickettsia typhi in australian veterinarians
Parasites & Vectors, 2017Co-Authors: Yen Thon Teoh, Sze Fui Hii, Mark Stevenson, Stephen Graves, Robert Rees, John Stenos, Rebecca J TraubAbstract:Rickettsia Felis and Rickettsia typhi are emerging arthropod-borne zoonoses causing fever and flu-like symptoms. Seroprevalence and risk factors associated with exposure to these organisms was explored in Australian veterinarians. One hundred and thirty-one veterinarians from across Australia were recruited to participate in a cross-sectional survey. Veterinarians provided a single blood sample and answered a questionnaire on potential risk factors influencing their exposure to R. Felis and R. typhi. Indirect microimmunofluorescence antibody testing (IFAT) was used to identify evidence of serological exposure of the participants to R. Felis and R. typhi. Results were analyzed and a logistical regression model performed to predict risk factors associated with seropositivity. In total, 16.0% of participants were seropositive to R. Felis, 4.6% to R. typhi and 35.1% seropositive to both, where cross-reactivity of the IFAT between R. Felis and R. typhi precluded a definitive diagnosis. Veterinarians residing within the south-eastern states of Victoria and Tasmania were at a higher risk of exposure to R. Felis or generalised R. Felis or R. typhi exposure. Older veterinarians and those that recommended flea treatment to their clients were found to be significantly protected from exposure. The high exposure to R. Felis amongst veterinary professionals suggests that flea-borne spotted fever is an important cause of undifferentiated fever conditions that may not be adequately recognized in Australia.
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Evidence of exposure to Rickettsia Felis in Australian patients
Elsevier, 2016Co-Authors: Yen Thon Teoh, Sze Fui Hii, Stephen Graves, Robert Rees, John Stenos, Rebecca J TraubAbstract:Rickettsia Felis is an emerging zoonosis, causing flea-borne spotted fever (FBSF). Serological diagnosis is typically confounded by cross-reactivity with typhus group Rickettsiae and prior to the development of specific serological methods, cases of FBSF in Australia were misdiagnosed. Patient sera tested between August 2010 and December 2013 and known to be seropositive to R. typhi by immunofluorescence antibody testing (IFAT) were subsequently retested against R. Felis using an R. Felis-specific IFAT. Sera of 49 patients were of a sufficient quality to be included in re-analysis. A classification of FBSF and murine typhus (MT) was attributed to fourteen and seven patients respectively, based on a minimum four-fold higher antibody titre to R. Felis than to R. typhi and vice versa. Twenty-eight patients were classified as indeterminate for either R. Felis or R. typhi (antibody titres within two-fold of one another). Historically, it is likely that Australian patients clinically ill with FBSF were misdiagnosed. It is important that medical practitioners consider FBSF as part of their differential diagnoses, and obtain relevant history with regard to patient's exposure to domestic pets and their fleas. Australian microbiology diagnostic laboratories should include serological testing for R. Felis as part of the diagnostic panel for febrile diseases. Veterinarians are encouraged to increase their awareness of this emerging zoonosis and advocate flea control in pets
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seroprevalence and risk factors for Rickettsia Felis exposure in dogs from southeast queensland and the northern territory australia
Parasites & Vectors, 2013Co-Authors: Sze Fui Hii, Robert Rees, John Stenos, Mohammad Yazid Abdad, Steven Kopp, Rebecca J TraubAbstract:Background: The recent detection of Rickettsia Felis DNA in dogs in Australia suggests that dogs are potential mammalian reservoir hosts for this emerging Rickettsia. To date, there is no published report addressing the seroprevalence of R. Felis in dogs in Australia. Methods: Antigens for R. Felis were produced by inoculating confluent XTC-2 monolayer cell cultures with three pools of cat flea (Ctenocephalides Felis) homogenates. Infection was confirmed by real-time (qPCR), conventional or nested PCRs targeting the ompB, gltA, 17 kDa and ompA genes. Two hundred and ninety-two dogs from Southeast Queensland and the Northern Territory were tested for the presence of R. Felis antibodies using a microimmunofluorescence (IF) test and the seroprevalence and associated risk factors for exposure were determined using both uni- and multi-variate analyses. Results: Rickettsia Felis was successfully isolated in cell culture from all three cat-flea pools. One hundred and fortyeight dogs (50.7%) showed seropositivity with titres ≥64 and 54 (18.5%) with titres ≥128. At antibody titres ≥64, dogs with active ectoparasite control were less likely to be seropositive to R. Felis (OR: 2.60; 95% CI: 1.20 - 5.56). Conclusions: This first reported isolation of R. Felis in cell culture in Australia allowed for the production of antigen for serological testing of dogs. Results of this serological testing reflects the ubiquitous exposure of dogs to R. Felis and advocate for owner vigilance with regards to ectoparasite control on domestic pets.
Lane D. Foil - One of the best experts on this subject based on the ideXlab platform.
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dissemination of bloodmeal acquired Rickettsia Felis in cat fleas ctenocephalides Felis
Parasites & Vectors, 2013Co-Authors: Supanee Hirunkanokpun, Chutima Thepparit, Lane D. Foil, Vsevolod L Popov, Kevin R MacalusoAbstract:Cat fleas, Ctenocephalides Felis, are known biological vectors for Rickettsia Felis. Rickettsial transmission can be vertical via transovarial transmission within a flea population, as well as horizontal between fleas through a bloodmeal. The previously undescribed infection kinetics of bloodmeal-acquired R. Felis in cat fleas provides insight into the R. Felis-flea interaction. In the present study, dissemination of R. Felis in previously uninfected cat fleas fed an R. Felis-infected bloodmeal was investigated. At weekly intervals for 28 days, Rickettsial propagation, accumulation, and dissemination in gut epithelial cells, specifically in the hindgut and the specialized cells in the neck region of midgut, were observed on paraffin sections of infected cat fleas by immunofluorescence assay (IFA) and confirmed by PCR detection of R. Felis 17-kDa antigen gene. IFA results demonstrate ingested Rickettsiae in vacuoles during early infection of the gut; lysosomal activity, indicated by lysosome marker staining of freshly-dissected gut, suggests the presence of phagolysosome-associated vacuoles. Subsequent to infection in the gut, Rickettsiae spread to the hemocoel and other tissues including reproductive organs. Densely-packed Rickettsiae forming mycetome-like structures were observed in the abdomen of infected male cat fleas during late infection. Ultrastructural analysis by transmission electron microscopy (TEM) confirmed the presence and infection characteristics of Rickettsia including Rickettsial destruction in the phagolysosome, Rickettsial division, and accumulation in the flea gut. This study intimately profiles R. Felis dissemination in cat fleas and further illuminates the mechanisms of Rickettsial transmission in nature.
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horizontal transmission of Rickettsia Felis between cat fleas ctenocephalides Felis
Molecular Ecology, 2011Co-Authors: Supanee Hirunkanokpun, Chutima Thepparit, Lane D. Foil, Kevin R MacalusoAbstract:Rickettsia Felis is a Rickettsial pathogen primarily associated with the cat flea, Ctenocephalides Felis. Although laboratory studies have confirmed that R. Felis is maintained by transstadial and transovarial transmission in C. Felis, distinct mechanisms of horizontal transmission of R. Felis among cat fleas are undefined. Based on the inefficient vertical transmission of R. Felis by cat fleas and the detection of R. Felis in a variety of haematophagous arthropods, we hypothesize that R. Felis is horizontally transmitted between cat fleas. Towards testing this hypothesis, flea transmission of R. Felis via a bloodmeal was assessed weekly for 4 weeks. Rhodamine B was used to distinguish uninfected recipient and R. Felis-infected donor fleas in a Rickettsial horizontal transmission bioassay, and quantitative real-time PCR assay was used to measure transmission frequency; immunofluorescence assay also confirmed transmission. Female fleas acquired R. Felis infection more readily than male fleas after feeding on a R. Felis-infected bloodmeal for 24 h (69.3% and 43.3%, respectively) and both Rickettsia-uninfected recipient male and female fleas became infected with R. Felis after cofeeding with R. Felis-infected donor fleas (3.3-40.0%). Distinct bioassays were developed to further determine that R. Felis was transmitted from R. Felis-infected to uninfected fleas during cofeeding and copulation. Vertical transmission of R. Felis by infected fleas was not demonstrated in this study. The demonstration of horizontal transmission of R. Felis between cat fleas has broad implications for the ecology of R. Felis rickettsiosis.
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acquisition of Rickettsia Felis by cat fleas during feeding
Vector-borne and Zoonotic Diseases, 2011Co-Authors: Kathryn E Reif, Lane D. Foil, Michael T Kearney, Kevin R MacalusoAbstract:Abstract Evidence for horizontal routes of transmission for Rickettsia Felis has come from detection of R. Felis infection in vertebrates and multiple blood-feeding arthropods; however, infection o...
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prevalence and infection load dynamics of Rickettsia Felis in actively feeding cat fleas
PLOS ONE, 2008Co-Authors: Kathryn E Reif, Lane D. Foil, Rhett W Stout, Gretchen C Henry, Kevin R MacalusoAbstract:Background Rickettsia Felis is a flea-associated Rickettsial pathogen recurrently identified in both colonized and wild-caught cat fleas, Ctenocephalides Felis. We hypothesized that within colonized fleas, the intimate relationship between R. Felis and C. Felis allows for the coordination of Rickettsial replication and metabolically active periods during flea bloodmeal acquisition and oogenesis.
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identification of Rickettsia Felis in the salivary glands of cat fleas
Vector-borne and Zoonotic Diseases, 2008Co-Authors: Kevin R Macaluso, Walairat Pornwiroon, Vsevolod L Popov, Lane D. FoilAbstract:Rickettsia Felis, a flea-associated Rickettsial pathogen, has been identified in many tissues, including the digestive and reproductive tissues, within the cat flea, Ctenocephalides Felis. We utilized transmission electron microscopy and polymerase chain reaction to identify R. Felis in the salivary glands of fed fleas and further define the distribution of R. Felis within the arthropod host. We identified Rickettsia-like organisms in salivary glands using electron microscopy. Sequence analysis of portions of the Rickettsia genus-specific 17-kDa antigen gene and R. Felis plasmid confirmed the morphological identification of R. Felis in cat flea salivary glands. This is the first report of R. Felis in tissues critical for horizontal transmission of Rickettsiae.
