Search Results (9)

Introduction: Spotted fever group (SFG) rickettsioses are tick-transmitted infections caused by Gram-negative, obligately intracellular bacteria in the genus Rickettsia. They present as an acute undifferentiated febrile illness, and they are often accompanied by rash and/or eschar. Although the rash of SFG rickettsioses usually consists of macules and papules, some, like in Rickettsia parkeri rickettsiosis, can also manifest with papulovesicular or pustular lesions. Case: We herein present a case of SFG rickettsiosis, due to R. parkeri, that masqueraded as Sweet syndrome (the prototype neutrophilic dermatosis) after the initial results of a shave biopsy. Further investigation of the biopsy specimen by immunohistochemical and PCR analysis would eventually confirm SFG rickettsiosis, with R. parkeri being detected by real-time PCR. Discussion:Rickettsia parkeri is transmitted by the Gulf Coast tick (Amblyomma maculatum) and is an increasingly recognized cause of SFG rickettsiosis in the United States. Rickettsia parkeri should be considered in those with an acute undifferentiated febrile illness with lesions that are pustular or papulovesicular, as prompt recognition and empirical administration of doxycycline results in the rapid resolution of symptoms. Full article

Brazilian spotted fever (BSF) is the most important tick-borne diseases affecting humans in Brazil. Cases of BSF have recently been reported in the Goiás state, midwestern Brazil. All cases have been confirmed by reference laboratories by seroconversion to Rickettsia rickettsii antigens. Because serological cross-reactions among different rickettsial species that belong to the spotted fever group (SFG) are common, the agent responsible for BSF cases in Goiás remains unknown. From March 2020 to April 2022, ticks and plasma were collected from dogs, horses and capybaras (Hydrochoerus hydrochaeris), and from the vegetation in an area where BSF cases have been reported and two areas under epidemiological surveillance in Goiás. Horses were infested by Amblyomma sculptum, Dermacentor nitens and Rhipicephalus microplus; dogs by Rhipicephalus sanguineus sensu lato (s.l.), Amblyomma ovale and A. sculptum, and capybaras by A. sculptum and Amblyomma dubitatum. Adults of A. sculptum, A. dubitatum, Amblyomma rotundatum and immature stages of A. sculptum and A. dubitatum, and Amblyomma spp. were collected from the vegetation. DNA of Rickettsia that did not belong to the SFG was detected in A. dubitatum, which was identified by DNA sequencing as Rickettsia bellii. Seroreactivity to SFG and Rickettsia bellii antigens was detected in 25.4% (42/165) of dogs, 22.7% (10/44) of horses and 41.2% (7/17) of capybaras, with higher titers for R. bellii in dogs and capybaras. The seropositivity of animals to SFG Rickettsia spp. antigens demonstrates the circulation of SFG rickettsiae in the region. Further research is needed to fully determine the agent responsible for rickettsiosis cases in this area. Full article

Mediterranean spotted fever (MSF) is an emerging tick-borne rickettsiosis of the spotted fever group (SFG), endemic in the Mediterranean basin. By virtue of technological innovations in molecular genetics, it has been determined that the causative agent of MSF is Rickettsia conorii subspecies conorii. The arthropod vector of this bacterium is the brown dog tick Rhipicephalus sanguineus. The true nature of the reservoir of R. conorii conorii has not been completely deciphered yet, although many authors theorize that the canine population, other mammals, and the ticks themselves could potentially contribute as reservoirs. Typical symptoms of MSF include fever, maculopapular rash, and a characteristic eschar (“tache noire”). Atypical clinical features and severe multi-organ complications may also be present. All of these manifestations arise from the disseminated infection of the endothelium by R. conorii conorii. Several methods exist for the diagnosis of MSF. Serological tests are widely used and molecular techniques have become increasingly available. Doxycycline remains the treatment of choice, while preventive measures are focused on modification of human behavior and vector control strategies. The purpose of this review is to summarize the current knowledge on the epidemiology, pathogenesis, clinical features, diagnosis, and treatment of MSF. Full article

Rickettsia are significant sources of tick-borne diseases in humans worldwide. In North America, two species in the spotted fever group of Rickettsia have been conclusively associated with disease of humans: Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever, and Rickettsia parkeri, the cause of R. parkeri rickettsiosis. Previous work in our lab demonstrated non-endothelial parasitism by another pathogenic SFG Rickettsia species, Rickettsia conorii, within THP-1-derived macrophages, and we have hypothesized that this growth characteristic may be an underappreciated aspect of rickettsial pathogenesis in mammalian hosts. In this work, we demonstrated that multiple other recognized human pathogenic species of Rickettsia, including R. rickettsii, R. parkeri, Rickettsia africae, and Rickettsiaakari can grow within target endothelial cells as well as within PMA-differentiated THP-1 cells. In contrast, Rickettsia bellii, a Rickettsia species not associated with disease of humans, and R. rickettsii strain Iowa, an avirulent derivative of pathogenic R. rickettsii, could invade both cell types but proliferate only within endothelial cells. Further analysis revealed that similar to previous studies on R. conorii, other recognized pathogenic Rickettsia species could grow within the cytosol of THP-1-derived macrophages and avoided localization with two different markers of lysosomal compartments; LAMP-2 and cathepsin D. R. bellii, on the other hand, demonstrated significant co-localization with lysosomal compartments. Collectively, these findings suggest that the ability of pathogenic rickettsial species to establish a niche within macrophage-like cells could be an important factor in their ability to cause disease in mammals. These findings also suggest that analysis of growth within mammalian phagocytic cells may be useful to predict the pathogenic potential of newly isolated and identified Rickettsia species. Full article

Spotted fever group (SFG) rickettsiae causes febrile illness in humans worldwide. Since SFG rickettsiosis’s clinical presentation is nonspecific, it is frequently misdiagnosed as other febrile diseases, especially malaria, and complicates proper treatment. Aiming at rapid, simple, and simultaneous detection of SFG Rickettsia spp. and Plasmodium spp., we developed a novel multiple pathogen detection system by combining a loop-mediated isothermal amplification (LAMP) method and dipstick DNA chromatography technology. Two primer sets detecting SFG Rickettsia spp. and Plasmodium spp. were mixed, and amplified products were visualized by hybridizing to dipstick DNA chromatography. The multiplex LAMP with dipstick DNA chromatography distinguished amplified Rickettsia and Plasmodium targeted genes simultaneously. The determined sensitivity using synthetic nucleotides was 1000 copies per reaction for mixed Rickettsia and Plasmodium genes. When genomic DNA from in vitro cultured organisms was used, the sensitivity was 100 and 10 genome equivalents per reaction for Rickettsia monacensis and Plasmodium falciparum, respectively. Although further improvement will be required for more sensitive detection, our developed simultaneous diagnosis technique will contribute to the differential diagnosis of undifferentiated febrile illness caused by either SFG Rickettsia spp. or Plasmodium spp. in resource-limited endemic areas. Importantly, this scheme is potentially versatile for the simultaneous detection of diverse infectious diseases. Full article

Rickettsia spp. are the second most common pathogens detected in Ixodes ricinus ticks in Austria after Borrelia burgdorferi sensu lato. Species belonging to the spotted fever group (SFG) are the causative agents for tick-borne rickettsiosis across the world. So far, only four SFG Rickettsia spp. were detected in Austria, namely R. helvetica, R. raoultii, R. monacensis and R. slovaca. Here, we describe the identification of a new SFG Rickettsia species detected in an I. ricinus tick. Sequencing of various rickettsial genes revealed a nucleotide sequence similarity of 99.6%, 98.5%, 97.3% and 98.5% to the gltA, ompA, ompB, and sca4 genes, respectively, of known and validated species. Additionally, sequencing of the htrA gene and 23S-5S intergenic spacer region also only showed 99.6% and 99.2%, respectively, similarity to known species. Therefore, and in accordance with current criteria for Rickettsia species discrimination, we hereby describe a new species of the SFG with putative pathogenic potential. We propose the name “Candidatus Rickettsia thierseensis” based on the village Thiersee in the Austrian province of Tyrol, where the carrying tick was found. Full article

The clinical features of spotted fever group (SFG) Rickettsia induced disease range from a mild to severe illness. The clinical complexity is even greater due to the fact that the disease can be caused by different species with varying degrees of virulence. Current knowledge asserts that the Israeli SFG (ISF) strain Rickettsia conorii israelensis is the only human pathogenic SFG member in Israel. Current diagnostic procedures distinguish between SFG and the typhus group rickettsiosis, assuming all SFG-positive clinical samples positive for ISF. Molecular studies on questing ticks over the past decade have uncovered the existence of other SFG strains besides ISF in Israel and the region. This study describes the first documented analysis of SFG-positive samples from Israeli patients with the goal of distinguishing between ISF and non-ISF SFG strains. We managed to identify a new Rickettsia isolate from three independent clinical samples in Israel which was shown to be an as-yet unknown SFG member, showing no absolute identity with any known Rickettsia species present in the NCBI database. Full article

Rickettsiae have worldwide occurrence and rickettsiosis are widely recognized as emerging infections in several parts of the world. For decades, it was thought that a single pathogenic tick-borne spotted fever group (SFG), Rickettsia, occurred in each continent. Nowadays, thanks to molecular biology, new species of Rickettsia responsible for disease in humans are continuously identified worldwide. In a framework of diagnostic activities of the Istituto Zooprofilattico Sperimentale dell’Abruzzo e del Molise “G. Gaporale” and considering some reports of suspected human clinical cases of rickettsiosis, a survey on ticks collected form animals and humans was carried out with the aim to identify the Rickettsia species circulating in Abruzzi and Molise regions. A total of 603 ticks, previously identified at species level by morphology, pooled into 178 tick samples, were tested by pan-Rickettsia RealTime PCR. DNA from specimens positive for Rickettsia spp. was then sequenced in order to identify the Rickettsia species involved. The highest infection rate was detected in Dermacentor marginatus followed by Ixodes ricinus. The selected targets for this purpose were OmpA and gltA. Rickettsia slovaca, Rickettsia monacensis, Rickettsia massiliae, Rickettsia conorii, Rickettsia aeschlimannii, Rickettsia helvetica, Rickettsia raoultii, and Rickettsia felis – like organisms were identified in this study. These are the first data available in the literature for the circulation of SFG Rickettsia species in the selected geographical area. Results made evidence of high rate of infection in ticks. All Rickettsia species detected have been previously involved in human infection. The diversity of Rickettsia detected, and tick species collected reflects the biodiversity in term of wildlife and environment of the area. An association between Rickettsia species, ticks, and the relationships with vertebrate host species are discussed. Due to the peculiar eco-biology of each Rickettsia species, the use of diagnostic tools able to identify Rickettsia at the species level is thus recommended in order to assess the risk for humans and to elucidate more precise etiological diagnosis in clinical cases. Full article

Anaplasma phagocytophilum and Rickettsia spp. are tick-borne bacteria of veterinary and human concern. In view of the One-Health concept, the present study wanted to evaluate the spreading of these pathogens in horses living in central Italy. In particular, the aim of the investigation was to verify the exposure to A. phagocytophilum in order to update the prevalence of this pathogen in the equine population from this area, and to spotted fever group (SFG) Rickettsia spp. to evaluate a possible role of horses in the epidemiology of rickettsiosis. Indirect immunofluorescent assay was carried out to detect antibodies against A. phagocytophilum and SFG (spotted fever group) Rickettsia spp. in blood serum samples collected from 479 grazing horses living in central Italy during the period from 2013 to 2018. One hundred and nine (22.75%) horses were positive for A. phagocytophilum, 72 (15.03%) for SFG Rickettsia spp., and 19 (3.96%) for both antigens. The obtained results confirm the occurrence of A. phagocytophilum in equine populations, and also suggest the involvement of horses in the epidemiology of SFG rickettsiosis. In both cases, in view of the zoonotic aspect of these pathogens and the frequent contact between horses and humans, the monitoring of equine populations could be useful for indication about the spreading of the tick-borne pathogens in a certain geographic area. Full article