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Virulence Dec 2022Rickettsiae include diverse Gram-negative microbial species that exhibit obligatory intracellular lifecycles between mammalian hosts and arthropod vectors. Human... (Review)
Review
Rickettsiae include diverse Gram-negative microbial species that exhibit obligatory intracellular lifecycles between mammalian hosts and arthropod vectors. Human infections with arthropod-borne continue to cause significant morbidity and mortality as recent environmental changes foster the proliferation of arthropod vectors and increased exposure to humans. However, the technical difficulties in working with have delayed our progress in understanding the molecular mechanisms involved in rickettsial pathogenesis and disease transmission. Recent advances in developing genetic tools for have enabled investigators to identify virulence genes, uncover molecular functions, and characterize host responses to rickettsial determinants. Therefore, continued efforts to determine virulence genes and their biological functions will help us understand the underlying mechanisms associated with arthropod-borne rickettsioses.
Topics: Animals; Humans; Mammals; Rickettsia; Rickettsia Infections; Virulence
PubMed: 36208040
DOI: 10.1080/21505594.2022.2132047 -
Microbes and Infection 2015Bacteria of the genera Rickettsia and Orientia (family rickettsiaceae, order rickettsiales) cause rickettsioses worldwide, and are transmitted by lice, fleas, ticks and... (Review)
Review
Bacteria of the genera Rickettsia and Orientia (family rickettsiaceae, order rickettsiales) cause rickettsioses worldwide, and are transmitted by lice, fleas, ticks and mites. In Europe, only Rickettsia spp. cause rickettsioses. With improvement of hygiene, the risk of louse-borne rickettsiosis (epidemic typhus) is low in Europe. Nevertheless, recrudescent form of Rickettsia prowazekii infection persists. There could be an epidemic typhus outbreak if a body lice epidemic occurs under unfavorable sanitary conditions. In Europe, endemic typhus or Rickettsia typhi infection, transmitted by rats and fleas, causes febrile illness. At the beginning of this century, flea-borne spotted fever cases caused by Rickettsia felis were diagnosed. Flea-borne rickettsiosis should be suspected after flea bites if fever, with or without rash, is developed. Tick-borne rickettsioses are the main source of rickettsia infections in Europe. Apart from Rickettsia conorii, the Mediterranean Spotted Fever (MSF) agent, other Rickettsia spp. cause MSF-like: Rickettsia helvetica, Rickettsia monacensis, Rickettsia massiliae or Rickettsia aeschlimannii. In the 1990s, two 'new' rickettsioses were diagnosed: Lymphangitis Associated Rickettsiosis (LAR) caused by Rickettsia sibirica mongolitimonae, and Tick-Borne Lymphadenopathy/Dermacentor-Borne-Necrosis-Erythema-Lymphadenopathy/Scalp Eschar Neck Lymphadenopathy (TIBOLA/DEBONEL/SENLAT), caused by Rickettsia slovaca, Candidatus Rickettsia rioja and Rickettsia raoultii. Lastly, European reports about mite-borne rickettsiosis are scarce.
Topics: Animals; Arthropods; Europe; Humans; Orientia tsutsugamushi; Rickettsia; Rickettsia Infections; Scrub Typhus
PubMed: 26384814
DOI: 10.1016/j.micinf.2015.09.009 -
Current Opinion in Microbiology Aug 2023Recent discoveries of basal extracellular Rickettsiales have illuminated divergent evolutionary paths to host dependency in later-evolving lineages. Family... (Review)
Review
Recent discoveries of basal extracellular Rickettsiales have illuminated divergent evolutionary paths to host dependency in later-evolving lineages. Family Rickettsiaceae, primarily comprised of numerous protist- and invertebrate-associated species, also includes human pathogens from two genera, Orientia and Rickettsia. Once considered sister taxa, these bacteria form distinct lineages with newly appreciated lifestyles and morphological traits. Contrasting other rickettsial human pathogens in Family Anaplasmataceae, Orientia and Rickettsia species do not reside in host-derived vacuoles and lack glycolytic potential. With only a few described mechanisms, strategies for commandeering host glycolysis to support cytosolic growth remain to be discovered. While regulatory systems for this unique mode of intracellular parasitism are unclear, conjugative transposons unique to Orientia and Rickettsia species provide insights that are critical for determining how these obligate intracellular pathogens overtake eukaryotic cytosol.
Topics: Humans; Rickettsia; Orientia; Gardens; Biological Evolution; Eukaryota
PubMed: 37080115
DOI: 10.1016/j.mib.2023.102318 -
Trends in Microbiology May 2022
Topics: Rickettsia
PubMed: 35115187
DOI: 10.1016/j.tim.2022.01.001 -
Frontiers in Cellular and Infection... 2023Rickettial agents are a diverse group of alpha-proteobacteria within the order Rickettsiales, which possesses two families with human pathogens, Rickettsiaceae and... (Review)
Review
Rickettial agents are a diverse group of alpha-proteobacteria within the order Rickettsiales, which possesses two families with human pathogens, Rickettsiaceae and Anaplasmataceae. These obligate intracellular bacteria are most frequently transmitted by arthropod vectors, a first step in the pathogens' avoidance of host cell defenses. Considerable study of the immune responses to infection and those that result in protective immunity have been conducted. Less study has focused on the initial events and mechanism by which these bacteria avoid the innate immune responses of the hosts to survive within and propagate from host cells. By evaluating the major mechanisms of evading innate immunity, a range of similarities among these bacteria become apparent, including mechanisms to escape initial destruction in phagolysosomes of professional phagocytes, those that dampen the responses of innate immune cells or subvert signaling and recognition pathways related to apoptosis, autophagy, proinflammatory responses, and mechanisms by which these microbes attach to and enter cells or those molecules that trigger the host responses. To illustrate these principles, this review will focus on two common rickettsial agents that occur globally, species and .
Topics: Humans; Rickettsia Infections; Immunity, Innate; Rickettsia; Anaplasma phagocytophilum; Autophagy
PubMed: 37228668
DOI: 10.3389/fcimb.2023.1187267 -
Trends in Parasitology Aug 2021Although Rickettsia species are molecularly detected among a wide range of arthropods, vector competence becomes an imperative aspect of understanding the... (Review)
Review
Although Rickettsia species are molecularly detected among a wide range of arthropods, vector competence becomes an imperative aspect of understanding the ecoepidemiology of these vector-borne diseases. The synergy between vector homeostasis and rickettsial invasion, replication, and release initiated within hours (insects) and days (ticks) permits successful transmission of rickettsiae. Uncovering the molecular interplay between rickettsiae and their vectors necessitates examining the multifaceted nature of rickettsial virulence and vector infection tolerance. Here, we highlight the biological differences between tick- and insect-borne rickettsiae and the factors facilitating the incidence of rickettsioses. Untangling the complex relationship between rickettsial genetics, vector biology, and microbial interactions is crucial in understanding the intricate association between rickettsiae and their vectors.
Topics: Animals; Arthropod Vectors; Host-Pathogen Interactions; Rickettsia
PubMed: 34162522
DOI: 10.1016/j.pt.2021.05.008 -
Ticks and Tick-borne Diseases Sep 2021This study addresses a meta-analysis of the distribution of Rickettsia spp. in the Neotropical region, as well as their associations with ticks and vertebrates. A total... (Meta-Analysis)
Meta-Analysis
This study addresses a meta-analysis of the distribution of Rickettsia spp. in the Neotropical region, as well as their associations with ticks and vertebrates. A total of 219 published reports on Rickettsia in ticks in the target region were compiled, providing 599 records of 31 species of Rickettsia recorded in 50 species of Ixodidae. The aim is to capture the phylogenetic relationships between rickettsiae and the ticks carrying them in the target region, with a focus on the co-speciation ticks-rickettsiae. We compared the phylogeny of ticks, the records of rickettsiae, the environmental gradients colonized by ticks and the effect of the phylogenetic composition of vertebrates feeding ticks on the detection of Rickettsia in ticks. Results show that differences in rickettsial composition in ticks do not depend on the vertebrate's blood-source. This is the first time this result is demonstrated. This study pinpoints that some Neotropical rickettsial organisms are associated with well-defined phylogenetical clusters of ticks. Secondarily, and probably only in a few cases, rickettsiae share species of phylogenetically distant ticks distributed along a gradient of environmental traits in which the ticks overlap (i.e., the different strains of Rickettsia parkeri sensu lato). We outline the importance of some ticks that share hosts and habitat: these ticks may act as "bridges" for the circulation of rickettsial species. There are also many species of Rickettsia that have been detected so far in only one tick species, pointing to a tight relationship or to the lack of data preventing conclusions about the detection of these bacteria in other ticks. Two species, namely Rickettsia amblyommatis and Rickettsia bellii have been recorded in the majority of ticks in the region (mainly Amblyomma spp.) and seem to be not associated with definite tick species because they may be an essential symbiont of the ticks. We conclude that an adequate analysis of rickettsiae-ticks-habitat is necessary to address the human health issues derived from the infections by rickettsiae.
Topics: Amblyomma; Animals; Biological Evolution; Ecosystem; Evolution, Molecular; Host-Parasite Interactions; Ixodidae; Nymph; Phylogeny; Rickettsia; South America; Tick Infestations
PubMed: 34126403
DOI: 10.1016/j.ttbdis.2021.101754 -
Journal of Clinical Microbiology Aug 2018Rickettsioses are globally distributed and caused by the family , which comprise a diverse and expanding list of organisms. These include two genera, and Serology has... (Review)
Review
Rickettsioses are globally distributed and caused by the family , which comprise a diverse and expanding list of organisms. These include two genera, and Serology has been traditionally the mainstay of diagnosis, although this has been limited by cross-reactions among closely related members and diminished sensitivity/utility in the acute phase of illness. Other techniques, such as nucleic acid amplification tests using blood specimens or tissue swabs/biopsy specimens, sequencing, and mass spectrometry, have emerged in recent years for both pathogen and vector identification. This paper provides a concise review of the rickettsioses and the traditional and newer technologies available for their diagnosis.
Topics: Animals; Arthropod Vectors; Humans; Microbiological Techniques; Molecular Diagnostic Techniques; Orientia tsutsugamushi; Rickettsia; Rickettsia Infections; Scrub Typhus; Serologic Tests
PubMed: 29769278
DOI: 10.1128/JCM.01728-17 -
PLoS Neglected Tropical Diseases Aug 2023The order Rickettsiales contains a group of vector-borne gram-negative obligate intracellular bacteria, which often cause human emerging infectious diseases and economic...
BACKGROUND
The order Rickettsiales contains a group of vector-borne gram-negative obligate intracellular bacteria, which often cause human emerging infectious diseases and economic losses for dairy and meat industries. The purpose of this study is to investigate the distribution of the pathogens including Rickettsia spp., Anaplasma spp., and Ehrlichia spp. in the order Rickettsiales in ticks from Yueyang, a prefecture-level city of Hunan Province in Sothern China, and assess the potentiality of transovarial transmission of these rickettsial organisms.
METHODS
Ticks were collected from cattle in a farm in Yueyang City and the tick DNA was used as template to amplify the htrA, rrs, gltA, ompA and ompB genes of Rickettsia as well as rrs and groEL genes of Anaplasma and Ehrlichia.
RESULTS
All ticks (465) collected were the cattle tick, Rhipicephalus microplus. PCR showed the minimum infection rate (MIR) was 1.5% (7/465) for Candidatus Rickettsia xinyangensis, 1.9% (9/465) for C. Anaplasma boleense, 1.3% (6/465) for Anaplasma platys, 0.6% (3/465) for A. marginale, and 1.17% (2/465) for each of A. bovis, Ehrlichia minasensis, and a non-classified Ehrlichia sp. A human pathogen, C. Rickettsia xinyangensis and A. platys were detected in 100% (3/3) and 33.3% (2/6) laboratory-hatched larval pools from infected females respectively.
CONCLUSION
Our study revealed a diversity of pathogenic rickettsial species in R. microplus ticks from Hunan Province suggesting a threat to people and animals in China. This study also provided the first molecular evidence for the potential transovarial transmission of C. Rickettsia xinyangensis and A. platys in R. microplus, indicating that R. microplus may act as the host of these two pathogens.
Topics: Animals; Female; Humans; Rhipicephalus; Rickettsia; Larva; Ehrlichia; Rickettsiales; Anaplasma; Coleoptera
PubMed: 37647577
DOI: 10.1371/journal.pntd.0011546 -
Microbiology Spectrum Oct 2022Rickettsiae are obligate intracellular bacteria that can cause life-threatening illnesses. There is an ongoing debate as to whether established infections by one...
Rickettsiae are obligate intracellular bacteria that can cause life-threatening illnesses. There is an ongoing debate as to whether established infections by one species preclude the maintenance of the second species in ticks. Here, we identified two species in inoculum from Haemaphysalis montgomeryi ticks and subsequently obtained pure isolates of each species by plaque selection. The two isolates were classified as a transitional group and spotted fever group rickettsiae and named Rickettsia hoogstraalii str CS and Rickettsia rhipicephalii str EH, respectively. The coinfection of these two species was detected in 25.6% of individual field-collected H. montgomeryi. In cell culture infection models, R. hoogstraalii str CS overwhelmed R. rhipicephalii str EH with more obvious cytopathic effects, faster plaque formation, and increased cellular growth when cocultured, and R. hoogstraalii str CS seemed to polymerize actin tails differently from R. rhipicephalii str EH . This work provides a model to investigate the mechanisms of both - and -vector interactions. The rickettsiae are a group of obligate intracellular Gram-negative bacteria that include human pathogens causing an array of clinical symptoms and even death. There is an important question in the field, that is whether one infection can block the superinfection of other rickettsiae. This work demonstrated the coinfection of two species in individual ticks and further highlighted that testing the rickettsial competitive exclusion hypothesis will undoubtedly be a promising area as methods for bioengineering and pathogen biocontrol become amenable for rickettsiae.
Topics: Animals; Humans; Ticks; Coinfection; Actins; Rickettsia; Ixodidae
PubMed: 36173317
DOI: 10.1128/spectrum.02323-22