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Updates on Rickettsia and Coxiella
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Updates on Rickettsia and Coxiella (Closed)

A topical collection in Pathogens (ISSN 2076-0817). This collection belongs to the section "Parasitic Pathogens".

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Editors

Dr. John Stenos

E-Mail Website
Collection Editor
Australian Rickettsial Reference Laboratory, Geelong, Victoria, Australia
Interests: molecular diagnostics; microbial molecular biology; Q fever; Rickettsia infections; Rickettsiaceae; Coxiella burnetii; microbiology; ticks; zoonotic diseases; DNA
Dr. Mohammad Yazid Abdad

E-Mail Website
Collection Editor
1. Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, UK
2. Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Thailand
Interests: rickettsial organisms; tropical diseases; global health; arthropod-borne pathogens; zoonotic diseases; diagnostics development

Topical Collection Information

Dear Colleagues,

Rickettsiae and Coxiella are distinct bacterial groups, with the former an alphaproteobacterium and the later a gammaproteopbacterium, each with unique growth dynamics. Rickettsiae replicate in the cytosol or nucleus of eukaryotic cells while Coxiella grow in a pathogen-modified phagolysosome. These differences extend to their routes of transmission with rickettsiae mostly transmitted by arthropod vectors and Coxiella by air-borne transmission. However there is significant overlap in numerous aspects of their biology. This includes overlapping environmental niches, host and vector animals, and infection profiles in humans.

This Topic Collection, published by the journal Pathogens, will provide our small but productive community with an update on Coxiella and Rickettsiae. We are seeking papers from a wide scope, including epidemiological, species description and characterization, diagnostic assays, and vaccine development. We invite our colleagues from all disciplines, including clinical and basic research, to contribute their manuscripts for publication review in this Topic Collection of the journal dedicated to our favorite microbes. 

Dr. John Stenos
Dr. Mohammad Yazid Abdad
Collection Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the collection website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Pathogens is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Rickettsiae
  • Coxiella

Published Papers (28 papers)

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2023

Jump to: 2022, 2021, 2020

10 pages, 1001 KiB  
Article
A Novel Marine Mammal Coxiella burnetii—Genome Sequencing Identifies a New Genotype with Potential Virulence
by Brett R. Gardner, Nathan L. Bachmann, Adam Polkinghorne, Jasmin Hufschmid, Mythili Tadepalli, Marc Marenda, Stephen Graves, John P. Y. Arnould and John Stenos
Pathogens 2023, 12(7), 893; https://doi.org/10.3390/pathogens12070893 - 29 Jun 2023
Viewed by 1579
Abstract
The obligate intracellular bacterial pathogen Coxiella burnetii has been identified in a few species of marine mammals, some of which are showing population declines. It has been hypothesized that C. burnetii in marine mammals is a distinct genotype that varies significantly from the [...] Read more.
The obligate intracellular bacterial pathogen Coxiella burnetii has been identified in a few species of marine mammals, some of which are showing population declines. It has been hypothesized that C. burnetii in marine mammals is a distinct genotype that varies significantly from the typical terrestrial genotypes. It appears to lack an IS1111. Isolates originating from Australian marine animals have a distinctly non-Australian profile of multiple-locus variable-number tandem-repeat analysis (MLVA). Extracted Coxiella DNA of Australian fur seal placental origin was sequenced using the Novaseq platform. Illumina 150 bp paired-end reads were filtered and trimmed with Trimgalore. The microbial community present in the sequenced genome was evaluated with Kraken and Bracken software using the NCBI database. A phylogenetic analysis was performed using 1131 core genes. Core genes were identified using Panaroo and inputted into Iqtree to determine the maximum-likelihood tree. A second phylogenetic tree was created using Rickettsiella grylii and using seven housekeeping genes. Results were compared with the C. burnetii Nine Mile RSA439 virulent genome. This new Australian marine mammal isolate of Coxiella (PG457) appears to be a novel genotype that lacks IS1111 and has a distinct MLVA signature (ms26, ms27, ms28, ms30, and ms31). The presence of genes for multiple virulence factors appears to give this genotype sufficient pathogenicity for it to be considered a possible causative agent of abortion in Australian fur seals as well as a potential zoonotic risk. Full article
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14 pages, 3666 KiB  
Article
Orientia tsutsugamushi Infection in Wild Small Mammals in Western Yunnan Province, China
by Yun-Yan Luo, Si-Tong Liu, Qi-Nan He, Ru-Dan Hong, Jun-Jie Zhu, Zhi-Qiong Ai and Jia-Xiang Yin
Pathogens 2023, 12(1), 128; https://doi.org/10.3390/pathogens12010128 - 12 Jan 2023
Viewed by 1168
Abstract
Small mammals can transmit and serve as a reservoir for Orientia tsutsugamushi (Ot) in nature by carrying infected mites. In Yunnan, one of China’s main foci of scrub typhus, etiological evidence and genetic diversity for Ot is limited. A total of [...] Read more.
Small mammals can transmit and serve as a reservoir for Orientia tsutsugamushi (Ot) in nature by carrying infected mites. In Yunnan, one of China’s main foci of scrub typhus, etiological evidence and genetic diversity for Ot is limited. A total of 2538 small mammals were captured seasonally from 2015 to 2016 in the three counties of Yunnan, and the spleen or liver tissue was examined for Ot based on 56 kDa nPCR. The overall prevalence of Ot was 1.77%, ranging from 0.26 to 9.09% across different species. The Gilliam strain was found in 35.6% (16/45) of the wild small mammals, followed by the Karp 11.1% (5/45) and TA763 (1/45) strains, the last of which was discovered in western Yunnan for the first time. In Lianghe, Ot infection rates in wild small mammals were higher than in the other two counties. The infection rates of Eothenomys miletus with Ot were highest in the three dominant species. Ot infection rates in wild small mammals were higher in Lianghe (1200–1400 m) and Yulong (2800–3000 m). These findings could provide research clues for further confirmation of scrub typhus foci in western Yunnan or other similar natural environments. Full article
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2022

Jump to: 2023, 2021, 2020

26 pages, 1700 KiB  
Concept Paper
The Troublesome Ticks Research Protocol: Developing a Comprehensive, Multidiscipline Research Plan for Investigating Human Tick-Associated Disease in Australia
by Amanda D. Barbosa, Michelle Long, Wenna Lee, Jill M. Austen, Mike Cunneen, Andrew Ratchford, Brian Burns, Prasad Kumarasinghe, Rym Ben-Othman, Tobias R. Kollmann, Cameron R. Stewart, Miles Beaman, Rhys Parry, Roy Hall, Ala Tabor, Justine O’Donovan, Helen M. Faddy, Marjorie Collins, Allen C. Cheng, John Stenos, Stephen Graves, Charlotte L. Oskam, Una M. Ryan and Peter J. Irwinadd Show full author list remove Hide full author list
Pathogens 2022, 11(11), 1290; https://doi.org/10.3390/pathogens11111290 - 03 Nov 2022
Cited by 1 | Viewed by 3431
Abstract
In Australia, there is a paucity of data about the extent and impact of zoonotic tick-related illnesses. Even less is understood about a multifaceted illness referred to as Debilitating Symptom Complexes Attributed to Ticks (DSCATT). Here, we describe a research plan for investigating [...] Read more.
In Australia, there is a paucity of data about the extent and impact of zoonotic tick-related illnesses. Even less is understood about a multifaceted illness referred to as Debilitating Symptom Complexes Attributed to Ticks (DSCATT). Here, we describe a research plan for investigating the aetiology, pathophysiology, and clinical outcomes of human tick-associated disease in Australia. Our approach focuses on the transmission of potential pathogens and the immunological responses of the patient after a tick bite. The protocol is strengthened by prospective data collection, the recruitment of two external matched control groups, and sophisticated integrative data analysis which, collectively, will allow the robust demonstration of associations between a tick bite and the development of clinical and pathological abnormalities. Various laboratory analyses are performed including metagenomics to investigate the potential transmission of bacteria, protozoa and/or viruses during tick bite. In addition, multi-omics technology is applied to investigate links between host immune responses and potential infectious and non-infectious disease causations. Psychometric profiling is also used to investigate whether psychological attributes influence symptom development. This research will fill important knowledge gaps about tick-borne diseases. Ultimately, we hope the results will promote improved diagnostic outcomes, and inform the safe management and treatment of patients bitten by ticks in Australia. Full article
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12 pages, 2564 KiB  
Article
Genetic Diversity of Coxiella burnetii in Iran by Multi-Spacer Sequence Typing
by Ashraf Mohabati Mobarez, Neda Baseri, Mohammad Khalili, Ehsan Mostafavi, John Stenos and Saber Esmaeili
Pathogens 2022, 11(10), 1175; https://doi.org/10.3390/pathogens11101175 - 11 Oct 2022
Cited by 2 | Viewed by 1828
Abstract
Coxiella burnetii, the zoonotic agent of Q fever, has a worldwide distribution including Iran. However, no information regarding the circulating genotype of this infection has been reported in Iran. This study aimed to evaluate the genetic diversity of C. burnetii in Iran [...] Read more.
Coxiella burnetii, the zoonotic agent of Q fever, has a worldwide distribution including Iran. However, no information regarding the circulating genotype of this infection has been reported in Iran. This study aimed to evaluate the genetic diversity of C. burnetii in Iran using the multi-spacer sequence typing (MST) method. First, 14 positive C. burnetii samples (collected from four sheep, three goats, and seven cattle) were confirmed using quantitative polymerase chain reaction (qPCR) targeting the IS1111 gene. Then, ten spacers (Cox 2, 5, 18, 20, 22, 37, 51, 56, 57, and 61) were amplified using PCR for future MST analysis. The in-silico MST genotyping analysis of domestic ruminant samples revealed two new alleles (Cox5.11 and Cox56.15) in Cox5 and Cox56 loci that led to the emergence of four novel MST genotypes (MST62, 63, 64, and 65) and one MST genotype that has been previously described (MST61). This study showed the circulation of five MST C. burnetii genotypes among Iranian domestic ruminants. Understanding the C. burnetii genotypic profiles is critical in determining and preventing Q fever outbreaks. Full article
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14 pages, 14747 KiB  
Article
Investigation of Rickettsia conorii in Patients Suspected of Having Crimean-Congo Hemorrhagic Fever
by Neda Baseri, Mostafa Salehi-Vaziri, Ehsan Mostafavi, Fahimeh Bagheri Amiri, Mina Latifian, John Stenos and Saber Esmaeili
Pathogens 2022, 11(9), 973; https://doi.org/10.3390/pathogens11090973 - 26 Aug 2022
Cited by 4 | Viewed by 1677
Abstract
Rickettsia conorii is the causative agent of Mediterranean spotted fever (MSF). Misdiagnosis of MSF may occur with febrile syndromes associated with rash and thrombocytopenia, such as Crimean-Congo hemorrhagic fever (CCHF). This study aimed to determine the prevalence of R. conorii among serum samples [...] Read more.
Rickettsia conorii is the causative agent of Mediterranean spotted fever (MSF). Misdiagnosis of MSF may occur with febrile syndromes associated with rash and thrombocytopenia, such as Crimean-Congo hemorrhagic fever (CCHF). This study aimed to determine the prevalence of R. conorii among serum samples obtained from 260 suspected CCHF patients with features of MSF in Iran (2018–2020). The quantitative polymerase chain reaction (qPCR) method detected three (1.15%) positive 16S rDNA Rickettsia spp. samples that were classified as R. conorii subsp. conorii, R. conorii subsp. Israelensis, and R. helvetica using the sequencing of gltA, ompA, and 17kDa genes. Furthermore, R. conorii IgM antibodies presented in 38 (14.62%) patients by the enzyme-linked immunosorbent assay (ELISA) method. Out of 97 MSF patients with available paired serum samples, IgM seroconversion and a four-fold increase were observed in 14 (14.43%) and 12 (12.37%) patients, respectively. We concluded that rickettsial agents are present in Iran and may be misdiagnosed with other febrile syndromes. Full article
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10 pages, 401 KiB  
Article
Leptospira interrogans Sensu Lato in Wild Small Mammals in Three Moravian Localities of the Czech Republic
by Alena Žákovská, František Treml, Helena Nejezchlebová, Jiří Nepeřený, Marie Budíková and Eva Bártová
Pathogens 2022, 11(8), 888; https://doi.org/10.3390/pathogens11080888 - 08 Aug 2022
Cited by 1 | Viewed by 1376
Abstract
Leptospirosis is a widespread zoonosis, affecting humans, domestic animals and wildlife, with small mammals as a reservoir of this infection. In recent years, this disease has been re-emerging and affects approximately 1 million people all over the world each year. Due to this [...] Read more.
Leptospirosis is a widespread zoonosis, affecting humans, domestic animals and wildlife, with small mammals as a reservoir of this infection. In recent years, this disease has been re-emerging and affects approximately 1 million people all over the world each year. Due to this disease having a significant health impact, it is important to identify the source and method of infection. The risk of Leptospira sp. infection is higher mainly in the cities of developed and industrialised countries. The aim of the study was the detection of antibodies against Leptospira sp. in some wild small mammals captured in the Czech Republic. In total, samples of 855 animals captured in three locations of Moravia during a six-year study (2010–2015) were examined by a microscopic agglutination test, using eight serovars of Leptospira interrogans sensu lato, representing serogroups Grippotyphosa, Icterohaemorrhagiae, Australis, Canicola, Sejroe, Javanica, Pomona and Pyrogenes, as antigens. Antibodies to Leptospira sp. were detected in 6.1% (52/855) of animals, with a prevalence of 6.4% (51/801) and 1.9% (1/54) in rodents and insectivores, respectively. The only statistically significant difference (p ≤ 0.05) was in prevalence between individual species (0–33%), while there were no differences in sex (6.7% in females and 5.1% in males), locality (1.8–8%) and year of trapping (0–8.4%). Only two serovars, L. interrogans serovar Pomona and L. interrogans serovar Grippotyphosa, were detected in 5.5% and 0.5% of animals, respectively. The prevailing serovar of pathogenic L. interrogans s.l. can be identified in a number of infected people in the Czech Republic. The composition of vaccines should be based on the current occurrence of Leptospira serovars in the actual territory. For this reason, the occurrence of Leptospira and its serovars should therefore be regularly monitored. Full article
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12 pages, 1476 KiB  
Article
Profiling Risk Factors for Household and Community Spatiotemporal Clusters of Q Fever Notifications in Queensland between 2002 and 2017
by Tatiana Proboste, Nicholas J. Clark, Sarah Tozer, Caitlin Wood, Stephen B. Lambert and Ricardo J. Soares Magalhães
Pathogens 2022, 11(8), 830; https://doi.org/10.3390/pathogens11080830 - 25 Jul 2022
Cited by 2 | Viewed by 1589
Abstract
Q fever, caused by the bacterium Coxiella burnetii, is an important zoonotic disease worldwide. Australia has one of the highest reported incidences and seroprevalence of Q fever, and communities in the state of Queensland are at highest risk of exposure. Despite Australia’s [...] Read more.
Q fever, caused by the bacterium Coxiella burnetii, is an important zoonotic disease worldwide. Australia has one of the highest reported incidences and seroprevalence of Q fever, and communities in the state of Queensland are at highest risk of exposure. Despite Australia’s Q fever vaccination programs, the number of reported Q fever cases has remained stable for the last few years. The extent to which Q fever notifications cluster in circumscribed communities is not well understood. This study aimed to retrospectively explore and identify the spatiotemporal variation in Q fever household and community clusters in Queensland reported during 2002 to 2017, and quantify potential within cluster drivers. We used Q fever notification data held in the Queensland Notifiable Conditions System to explore the geographical clustering patterns of Q fever incidence, and identified and estimated community Q fever spatiotemporal clusters using SatScan, Boston, MA, USA. The association between Q fever household and community clusters, and demographic and socioeconomic characteristics was explored using the chi-squared statistical test and logistic regression analysis. From the total 2175 Q fever notifications included in our analysis, we found 356 Q fever hotspots at a mesh-block level. We identified that 8.2% of Q fever notifications belonged to a spatiotemporal cluster. Within the spatiotemporal Q fever clusters, we found 44 (61%) representing household clusters and 20 (27.8%) were statistically significant with an average cluster size of 3 km radius. Our multivariable model shows statistical differences between cases belonging to clusters in comparison with cases outside clusters based on the type of reported exposure. In conclusion, our results demonstrate that clusters of Q fever notifications are temporally stable and geographically circumscribed, indicating a persistent common exposure. Furthermore, within individuals in household and community clusters, abattoir exposure (a traditional occupational exposure) was rarely reported by individuals. Full article
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12 pages, 2092 KiB  
Article
Skin in the Game: An Assay to Monitor Leukocyte Infiltration in Dermal Lesions of a Guinea Pig Model for Tick-Borne Rickettsiosis
by Claire E. Cross, John V. Stokes, Navatha Alugubelly, Anne-Marie L. Ross, Bridget V. Willeford, Jamie D. Walker and Andrea S. Varela-Stokes
Pathogens 2022, 11(2), 119; https://doi.org/10.3390/pathogens11020119 - 20 Jan 2022
Cited by 3 | Viewed by 1871
Abstract
Intact, the skin typically serves as an effective barrier to the external world; however, once pathogens have breached this barrier via a wound, such as a tick bite, the surrounding tissues must recruit immune cells from the blood to neutralize the pathogen. With [...] Read more.
Intact, the skin typically serves as an effective barrier to the external world; however, once pathogens have breached this barrier via a wound, such as a tick bite, the surrounding tissues must recruit immune cells from the blood to neutralize the pathogen. With innate and adaptive immune systems being similar between the guinea pig and human systems, the ability of guinea pigs to show clinical signs of many infectious diseases, and the large size of guinea pigs relative to a murine model, the guinea pig is a valuable model for studying tick-borne and other pathogens that invade the skin. Here, we report a novel assay for assessing guinea pig leukocyte infiltration in the skin. Briefly, we developed an optimized six-color/eight-parameter polychromatic flow cytometric panel that combines enzymatic and mechanical dissociation of skin tissue with fluorescent antibody staining to allow for the immunophenotyping of guinea pig leukocytes that have migrated into the skin, resulting in inflammation. We designed this assay using a guinea pig model for tick-borne rickettsiosis to further investigate host–pathogen interactions in the skin, with preliminary data demonstrating immunophenotyping at skin lesions from infected ticks. We anticipate that future applications will include hypothesis testing to define the primary immune cell infiltrates responding to exposure to virulent, avirulent tick-borne rickettsiae, and tick-borne rickettsiae of unknown virulence. Other relevant applications include skin lesions resulting from other vector-borne pathogens, Staphylococcus aureus infection, and Buruli ulcer caused by Mycobacterium ulcerans. Full article
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2021

Jump to: 2023, 2022, 2020

14 pages, 1544 KiB  
Article
Seroepidemiological Study of Spotted Fever Group Rickettsiae and Identification of a Putative New Species, Rickesttsia sp. Da-1, in Gongliao, Northeast Taiwan
by Tsai-Ying Yen, Hsi-Chieh Wang, Yin-Chao Chang, Chien-Ling Su, Shu-Fen Chang, Pei-Yun Shu and Kun-Hsien Tsai
Pathogens 2021, 10(11), 1434; https://doi.org/10.3390/pathogens10111434 - 04 Nov 2021
Cited by 4 | Viewed by 2114
Abstract
Tick-borne spotted fever group (SFG) rickettsioses were neglected in Taiwan. The study reported a seroepidemiological survey of SFG rickettsiae in residents in Gongliao District, Northeast Taiwan. Blood samples were examined for antibodies against SFG rickettsiae by enzyme-linked immunosorbent assay and immunofluorescence assay. Risk [...] Read more.
Tick-borne spotted fever group (SFG) rickettsioses were neglected in Taiwan. The study reported a seroepidemiological survey of SFG rickettsiae in residents in Gongliao District, Northeast Taiwan. Blood samples were examined for antibodies against SFG rickettsiae by enzyme-linked immunosorbent assay and immunofluorescence assay. Risk factors were assessed using logistic regression. Ticks parasitizing dogs were collected within a 2 km radius from the houses of seropositive participants, and PCR was performed to detect possible tick-borne pathogens. Of 1108 participants, 75 (6.8%) had antibodies against SFG rickettsiae. Residents were more likely to be seropositive if they were older than 65 years, recruited by Dr. Enjoy’s Clinic, or resided in Jilin village. A total of 184 ticks including 5 species (Rhipicephalus sanguineus, Rhipicephalus haemaphysaloides, Dermacentor auratus, Haemaphysalis hystricis, Haemaphysalis ornithophila) were collected. Rickettsia spp. were detected in 6.5% (12/184) of ticks. Rickettsia sp. TwKM01 was found in 6 R. sanguineus and 4 R. haemaphysaloides; while Rickettsia sp. TwKM03 was identified in 1 R. sanguineus. Moreover, gene-based pairwise analysis indicated identification of a putative new species, Rickettsia sp. Da-1, in D. auratus. These findings provided evidence of SFG rickettsiae infection in ticks and suggested SFG rickettsiae exposure in the residents. Full article
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11 pages, 288 KiB  
Review
An Update on the Laboratory Diagnosis of Rickettsia spp. Infection
by Adam G. Stewart and Alexandra G. A. Stewart
Pathogens 2021, 10(10), 1319; https://doi.org/10.3390/pathogens10101319 - 13 Oct 2021
Cited by 26 | Viewed by 4169
Abstract
Rickettsia species causing human illness are present globally and can cause significant disease. Diagnosis and identification of this intracellular bacteria are challenging with many available diagnostic modalities suffering from several shortcomings. Detection of antibodies directed against Rickettsia spp. via serological methods remains widely [...] Read more.
Rickettsia species causing human illness are present globally and can cause significant disease. Diagnosis and identification of this intracellular bacteria are challenging with many available diagnostic modalities suffering from several shortcomings. Detection of antibodies directed against Rickettsia spp. via serological methods remains widely used with a broad range of sensitivity and specificity values reported depending on the assay. Molecular methods, including polymerase chain reaction (PCR) testing, enables species-specific identification with a fast turnaround time; however, due to resource requirements, use in some endemic settings is limited. Reports on the use of next-generation sequencing (NGS) and metagenomics to diagnose Rickettsia spp. infection have been increasing. Despite offering several potential advantages in the diagnosis and surveillance of disease, genomic approaches are currently only limited to reference and research laboratories. Continued development of Rickettsia spp. diagnostics is required to improve disease detection and epidemiological surveillance, and to better understand transmission dynamics. Full article
18 pages, 1274 KiB  
Article
Identification of Immunogenic Linear B-Cell Epitopes in C. burnetii Outer Membrane Proteins Using Immunoinformatics Approaches Reveals Potential Targets of Persistent Infections
by Sílvia da Silva Fontes, Fernanda de Moraes Maia, Laura Santa’Anna Ataides, Fernando Paiva Conte, Josué da Costa Lima-Junior, Tatiana Rozental, Matheus Ribeiro da Silva Assis, Adonai Alvino Pessoa Júnior, Jorlan Fernandes, Elba Regina Sampaio de Lemos and Rodrigo Nunes Rodrigues-da-Silva
Pathogens 2021, 10(10), 1250; https://doi.org/10.3390/pathogens10101250 - 28 Sep 2021
Cited by 3 | Viewed by 1944
Abstract
Coxiella burnetii is a global, highly infectious intracellular bacterium, able to infect a wide range of hosts and to persist for months in the environment. It is the etiological agent of Q fever—a zoonosis of global priority. Currently, there are no national surveillance [...] Read more.
Coxiella burnetii is a global, highly infectious intracellular bacterium, able to infect a wide range of hosts and to persist for months in the environment. It is the etiological agent of Q fever—a zoonosis of global priority. Currently, there are no national surveillance data on C. burnetii’s seroprevalence for any South American country, reinforcing the necessity of developing novel and inexpensive serological tools to monitor the prevalence of infections among humans and animals—especially cattle, goats, and sheep. In this study, we used immunoinformatics and computational biology tools to predict specific linear B-cell epitopes in three C. burnetii outer membrane proteins: OMP-H (CBU_0612), Com-1 (CBU_1910), and OMP-P1 (CBU_0311). Furthermore, predicted epitopes were tested by ELISA, as synthetic peptides, against samples of patients reactive to C. burnetii in indirect immunofluorescence assay, in order to evaluate their natural immunogenicity. In this way, two linear B-cell epitopes were identified in each studied protein (OMP-H(51–59), OMP-H(91–106), Com-1(57–76), Com-1(191–206), OMP-P1(197–209), and OMP-P1(215–227)); all of them were confirmed as naturally immunogenic by the presence of specific antibodies in 77% of studied patients against at least one of the identified epitopes. Remarkably, a higher frequency of endocarditis cases was observed among patients who presented an intense humoral response to OMP-H and Com-1 epitopes. These data confirm that immunoinformatics applied to the identification of specific B-cell epitopes can be an effective strategy to improve and accelerate the development of surveillance tools against neglected diseases. Full article
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17 pages, 723 KiB  
Review
Q Fever Vaccine Development: Current Strategies and Future Considerations
by Carrie Mae Long
Pathogens 2021, 10(10), 1223; https://doi.org/10.3390/pathogens10101223 - 22 Sep 2021
Cited by 18 | Viewed by 2944
Abstract
Q fever is a zoonotic disease caused by the intracellular pathogen Coxiella burnetii. This disease typically manifests as a self-limiting, febrile illness known as acute Q fever. Due to the aerosol transmissibility, environmental persistence, and infectivity of C. burnetii, this pathogen [...] Read more.
Q fever is a zoonotic disease caused by the intracellular pathogen Coxiella burnetii. This disease typically manifests as a self-limiting, febrile illness known as acute Q fever. Due to the aerosol transmissibility, environmental persistence, and infectivity of C. burnetii, this pathogen is a notable bioterrorism threat. Despite extensive efforts to develop next-generation human Q fever vaccines, only one vaccine, Q-Vax®, is commercially available. Q-Vax® is a phase I whole-cell vaccine, and its licensed use is limited to Australia, presumably due to the potential for a post-vaccination hypersensitivity response. Pre-clinical Q fever vaccine development is a major area of interest, and diverse approaches have been undertaken to develop an improved Q fever vaccine. Following a brief history of Q fever vaccine development, current approaches will be discussed along with future considerations for an improved Q fever vaccine. Full article
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7 pages, 423 KiB  
Article
Preliminary Evidence of Rickettsia slovaca and Rickettsia conorii Infection in the Sera of Sheep, Dogs and Deer from an Area of Northern Spain
by Lourdes Lledó and Consuelo Giménez-Pardo
Pathogens 2021, 10(7), 836; https://doi.org/10.3390/pathogens10070836 - 03 Jul 2021
Cited by 1 | Viewed by 1689
Abstract
Limited information is available on the presence of rickettsial infection in animal reservoirs in Spain. Antibodies against Rickettsia slovaca and Rickettsia conorii were therefore sought in the sera of farm, domestic and wild animals (n = 223 samples) in an area of [...] Read more.
Limited information is available on the presence of rickettsial infection in animal reservoirs in Spain. Antibodies against Rickettsia slovaca and Rickettsia conorii were therefore sought in the sera of farm, domestic and wild animals (n = 223 samples) in an area of northern Spain. Indirect immunofluorescence assays showed: (A) 17/120 and 16/120 (14.2% and 13.3%) of serum samples from sheep (farm animals) reacted with R. slovaca and R. conorii antigens, respectively; (B) 10/73 and 10/73 (13.7% and 13.7%) of samples from dogs (domestic animals) did the same; (C) as did 22/30 and 20/30 (73.3% and 66.6%) of samples from deer (wild animals) (overall titre range: 1/40 to 1/1280). The prevalence of both types of infection was significantly greater in the wild animals than either the farm or domestic animals. The largest titres were recorded for R. slovaca in all three groups. Full article
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16 pages, 5915 KiB  
Article
Molecular Detection and Genotyping of Coxiella-Like Endosymbionts in Ticks Collected from Animals and Vegetation in Zambia
by Toshiya Kobayashi, Elisha Chatanga, Yongjin Qiu, Martin Simuunza, Masahiro Kajihara, Bernard Mudenda Hang’ombe, Yoshiki Eto, Ngonda Saasa, Akina Mori-Kajihara, Edgar Simulundu, Ayato Takada, Hirofumi Sawa, Ken Katakura, Nariaki Nonaka and Ryo Nakao
Pathogens 2021, 10(6), 779; https://doi.org/10.3390/pathogens10060779 - 21 Jun 2021
Cited by 6 | Viewed by 3037
Abstract
Ticks are obligate ectoparasites as they require to feed on their host blood during some or all stages of their life cycle. In addition to the pathogens that ticks harbor and transmit to vertebrate hosts, they also harbor other seemingly nonpathogenic microorganisms including [...] Read more.
Ticks are obligate ectoparasites as they require to feed on their host blood during some or all stages of their life cycle. In addition to the pathogens that ticks harbor and transmit to vertebrate hosts, they also harbor other seemingly nonpathogenic microorganisms including nutritional mutualistic symbionts. Tick nutritional mutualistic symbionts play important roles in the physiology of the host ticks as they are involved in tick reproduction and growth through the supply of B vitamins as well as in pathogen maintenance and propagation. Coxiella-like endosymbionts (CLEs) are the most widespread endosymbionts exclusively reported in ticks. Although CLEs have been investigated in ticks in other parts of the world, there is no report of their investigation in ticks in Zambia. To investigate the occurrence of CLEs, their maintenance, and association with host ticks in Zambia, 175 ticks belonging to six genera, namely Amblyomma, Argas, Haemaphysalis, Hyalomma, Ornithodoros, and Rhipicephalus, were screened for CLEs, followed by characterization of CLEs by multi-locus sequence typing of the five Coxiella housekeeping genes (dnaK, groEL, rpoB, 16S rRNA, and 23S rRNA). The results showed that 45.7% (n = 80) were positive for CLEs. The comparison of the tick 16S rDNA phylogenetic tree with that of the CLEs concatenated sequences showed that there was a strong correlation between the topology of the trees. The results suggest that most of the CLEs have evolved within tick species, supporting the vertical transmission phenomenon. However, the negative results for CLE in some ticks warrants further investigations of other endosymbionts that the ticks in Zambia may also harbor. Full article
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11 pages, 1128 KiB  
Article
Wild Small Mammals and Ticks in Zoos—Reservoir of Agents with Zoonotic Potential?
by Pavlína Pittermannová, Alena Žákovská, Petr Váňa, Jiřina Marková, František Treml, Lenka Černíková, Marie Budíková and Eva Bártová
Pathogens 2021, 10(6), 777; https://doi.org/10.3390/pathogens10060777 - 21 Jun 2021
Cited by 3 | Viewed by 2549
Abstract
Wild small mammals and ticks play an important role in maintaining and spreading zoonoses in nature, as well as in captive animals. The aim of this study was to monitor selected agents with zoonotic potential in their reservoirs and vectors in a zoo, [...] Read more.
Wild small mammals and ticks play an important role in maintaining and spreading zoonoses in nature, as well as in captive animals. The aim of this study was to monitor selected agents with zoonotic potential in their reservoirs and vectors in a zoo, and to draw attention to the risk of possible contact with these pathogens. In total, 117 wild small mammals (rodents) and 166 ticks were collected in the area of Brno Zoo. Antibodies to the bacteria Coxiella burnetii, Francisella tularensis, and Borrelia burgdorferi s.l. were detected by a modified enzyme-linked immunosorbent assay in 19% (19/99), 4% (4/99), and 15% (15/99) of rodents, respectively. Antibodies to Leptospira spp. bacteria were detected by the microscopic agglutination test in 6% (4/63) of rodents. Coinfection (antibodies to more than two agents) were proved in 14.5% (15/97) of animals. The prevalence of C. burnetii statistically differed according to the years of trapping (p = 0.0241). The DNAs of B. burgdorferi s.l., Rickettsia sp., and Anaplasma phagocytophilum were detected by PCR in 16%, 6%, and 1% of ticks, respectively, without coinfection and without effect of life stage and sex of ticks on positivity. Sequencing showed homology with R. helvetica and A. phagocytophilum in four and one positive samples, respectively. The results of our study show that wild small mammals and ticks in a zoo could serve as reservoirs and vectors of infectious agents with zoonotic potential and thus present a risk of infection to zoo animals and also to keepers and visitors to a zoo. Full article
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18 pages, 683 KiB  
Article
Serological Evidence of Exposure to Spotted Fever Group and Typhus Group Rickettsiae in Australian Wildlife Rehabilitators
by Karen O. Mathews, David Phalen, Jacqueline M. Norris, John Stenos, Jenny-Ann Toribio, Nicholas Wood, Stephen Graves, Paul A. Sheehy, Chelsea Nguyen and Katrina L. Bosward
Pathogens 2021, 10(6), 745; https://doi.org/10.3390/pathogens10060745 - 12 Jun 2021
Cited by 1 | Viewed by 2412
Abstract
Rickettsioses are arthropod-borne zoonotic diseases, several of which occur in Australia. This study aimed to assess the exposure levels and risk factors for Rickettsia spp. among Australian wildlife rehabilitators (AWRs) using serology, PCR and a questionnaire. Antibody titres against Spotted Fever Group (SFG), [...] Read more.
Rickettsioses are arthropod-borne zoonotic diseases, several of which occur in Australia. This study aimed to assess the exposure levels and risk factors for Rickettsia spp. among Australian wildlife rehabilitators (AWRs) using serology, PCR and a questionnaire. Antibody titres against Spotted Fever Group (SFG), Typhus Group (TG) and Scrub Typhus Group (STG) antigens were determined using an immunofluorescence assay. PCR targeting the gltA gene was performed on DNA extracts from whole blood and serum. Logistic regression was used to identify risk factors associated with seropositivity. Of the 27 (22.1%; 27/122) seropositive participants all were seropositive for SFG, with 5/27 (4.1%) also positive for TG. Of the 27 positive sera, 14.8% (4/27) were further classified as exposure to R. australis, 3.7% (1/27) to R. honei, 3.7% (1/27) to R. felis and 77.8% (21/27) were classified as ‘indeterminate’—most of which (85.7%; 18/21) were indeterminate R. australis/R. honei exposures. Rickettsia DNA was not detected in whole blood or serum. Rehabilitators were more likely to be seropositive if more than one household member rehabilitated wildlife, were older than 50 years or had occupational animal contact. These findings suggest that AWRs are at increased risk of contracting Rickettsia-related illnesses, however the source of the increased seropositivity remains unclear. Full article
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9 pages, 1155 KiB  
Article
High Prevalence and New Genotype of Coxiella burnetii in Ticks Infesting Camels in Somalia
by Dimitrios Frangoulidis, Claudia Kahlhofer, Ahmed Shire Said, Abdinasir Yusuf Osman, Lidia Chitimia-Dobler and Yassir Adam Shuaib
Pathogens 2021, 10(6), 741; https://doi.org/10.3390/pathogens10060741 - 12 Jun 2021
Cited by 8 | Viewed by 3389
Abstract
Coxiella burnetii is the causative agent of Q fever. It can infect animals, humans, and birds, as well as ticks, and it has a worldwide geographical distribution. To better understand the epidemiology of C. burnetii in Somalia, ticks infesting camels were collected from [...] Read more.
Coxiella burnetii is the causative agent of Q fever. It can infect animals, humans, and birds, as well as ticks, and it has a worldwide geographical distribution. To better understand the epidemiology of C. burnetii in Somalia, ticks infesting camels were collected from five different regions, including Bari, Nugaal, Mudug, Sool, and Sanaag, between January and March 2018. Collected ticks were tested for C. burnetii and Coxiella-like endosymbiont DNA by using IS1111, icd, and Com1-target PCR assays. Moreover, sequencing of the 16S-rRNA was conducted. Molecular characterization and typing were done by adaA-gene analysis and plasmid-type identification. Further typing was carried out by 14-marker Multi-Locus Variable-Number Tandem Repeats (MLVA/VNTR) analysis. The investigated ticks (n = 237) were identified as Hyalomma spp. (n = 227, 95.8%), Amblyomma spp. (n = 8, 3.4%), and Ripicephalus spp. (n = 2, 0.8%), and 59.1% (140/237) of them were positive for Coxiella spp. While Sanger sequencing and plasmid-type identification revealed a C. burnetii that harbours the QpRS-plasmid, MLVA/VNTR genotyping showed a new genotype which was initially named D21. In conclusion, this is the first report of C. burnetii in ticks in Somalia. The findings denote the possibility that C. burnetii is endemic in Somalia. Further epidemiological studies investigating samples from humans, animals, and ticks within the context of “One Health” are warranted. Full article
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11 pages, 1939 KiB  
Article
Geographical Variation in Coxiella burnetii Seroprevalence in Dairy Farms Located in South-Western Ethiopia: Understanding the Broader Community Risk
by Tatiana Proboste, Feyissa Begna Deressa, Yanjin Li, David Onafruo Kal, Benti Deressa Gelalcha and Ricardo J. Soares Magalhães
Pathogens 2021, 10(6), 646; https://doi.org/10.3390/pathogens10060646 - 23 May 2021
Cited by 5 | Viewed by 2900
Abstract
Q fever is a zoonotic disease that is caused by Coxiella burnetii and leads to abortion and infertility in ruminants and debilitating disease in humans. Jimma zone, including Jimma town, located in the Oromia region of Ethiopia, was affected by an outbreak of [...] Read more.
Q fever is a zoonotic disease that is caused by Coxiella burnetii and leads to abortion and infertility in ruminants and debilitating disease in humans. Jimma zone, including Jimma town, located in the Oromia region of Ethiopia, was affected by an outbreak of abortions in ruminants related to Q fever infection between 2013 and 2015. This study aimed to investigate the geo-clustering of C. burnetii seroprevalence in dairy farms of Jimma town and identify the environmental risk factors associated with seroprevalence distribution. A total of 227 cattle were tested for antibodies against C. burnetii in 25 farms. We explored the clustering of C. burnetii seroprevalence using semivariograms. A geostatistical regression-based model was implemented to quantify the risk factors and to predict the geographical variation in C. burnetii seroprevalence at unsampled locations in Jimma town using OpenBugs. Our results demonstrated that the risk of exposure in dairy cattle varied across the landscape of Jimma town and was associated with environmental risk factors. The predictive map of C. burnetii seroprevalence showed that communities in the eastern part of Jimma town had the highest risk of exposure. Our results can inform community-level investigations of human seroprevalence in the high-risk areas to the east of Jimma. Full article
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12 pages, 1893 KiB  
Review
From Coxiella burnetii Infection to Pregnancy Complications: Key Role of the Immune Response of Placental Cells
by Sandra Madariaga Zarza, Soraya Mezouar and Jean-Louis Mege
Pathogens 2021, 10(5), 627; https://doi.org/10.3390/pathogens10050627 - 19 May 2021
Cited by 5 | Viewed by 2974
Abstract
The infection of pregnant animals and women by Coxiella burnetii, an intracellular bacterium, compromises both maternal health and foetal development. The placenta is targeted by C. burnetii, as demonstrated by bacteriological and histological evidence. It now appears that placental strains of C. [...] Read more.
The infection of pregnant animals and women by Coxiella burnetii, an intracellular bacterium, compromises both maternal health and foetal development. The placenta is targeted by C. burnetii, as demonstrated by bacteriological and histological evidence. It now appears that placental strains of C. burnetii are highly virulent compared to reference strains and that placental injury involves different types of placental cells. Trophoblasts, the major placental cells, are largely infected by C. burnetii and may represent a replicating niche for the bacteria. The placenta also contains numerous immune cells, including macrophages, dendritic cells, and mast cells. Placental macrophages are infected and activated by C. burnetii in an unusual way of M1 polarisation associated with bacterial elimination. Placental mast cells eliminate bacteria through a mechanism including the release of extracellular actin filaments and antimicrobial peptides. In contrast, C. burnetii impairs the maturation of decidual dendritic cells, favouring bacterial pathogenicity. Our aim is to review C. burnetii infections of human placentas, paying special attention to both the action and function of the different cell types, immune cells, and trophoblasts targeted by C. burnetii in relation to foetal injury. Full article
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17 pages, 15886 KiB  
Article
Correlating Genotyping Data of Coxiella burnetii with Genomic Groups
by Claudia M. Hemsley, Angela Essex-Lopresti, Isobel H. Norville and Richard W. Titball
Pathogens 2021, 10(5), 604; https://doi.org/10.3390/pathogens10050604 - 14 May 2021
Cited by 12 | Viewed by 2929
Abstract
Coxiella burnetii is a zoonotic pathogen that resides in wild and domesticated animals across the globe and causes a febrile illness, Q fever, in humans. Several distinct genetic lineages or genomic groups have been shown to exist, with evidence for different virulence potential [...] Read more.
Coxiella burnetii is a zoonotic pathogen that resides in wild and domesticated animals across the globe and causes a febrile illness, Q fever, in humans. Several distinct genetic lineages or genomic groups have been shown to exist, with evidence for different virulence potential of these lineages. Multispacer Sequence Typing (MST) and Multiple-Locus Variable number tandem repeat Analysis (MLVA) are being used to genotype strains. However, it is unclear how these typing schemes correlate with each other or with the classification into different genomic groups. Here, we created extensive databases for published MLVA and MST genotypes of C. burnetii and analysed the associated metadata, revealing associations between animal host and human disease type. We established a new classification scheme that assigns both MST and MLVA genotypes to a genomic group and which revealed additional sub-lineages in two genomic groups. Finally, we report a novel, rapid genomotyping method for assigning an isolate into a genomic group based on the Cox51 spacer sequence. We conclude that by pooling and streamlining existing datasets, associations between genotype and clinical outcome or host source were identified, which in combination with our novel genomotyping method, should enable an estimation of the disease potential of new C. burnetii isolates. Full article
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9 pages, 491 KiB  
Article
National Seroprevalence of Coxiella burnetii in Chile, 2016–2017
by Teresa Tapia, María Fernanda Olivares, John Stenos, Rodrigo Iglesias, Nora Díaz, Natalia Vergara, Viviana Sotomayor, Doris Gallegos, Ricardo J Soares Magalhães, Johanna Acevedo, Pamela Araya, Stephen R Graves and Juan Carlos Hormazabal
Pathogens 2021, 10(5), 531; https://doi.org/10.3390/pathogens10050531 - 28 Apr 2021
Cited by 9 | Viewed by 1866
Abstract
Coxiella burnetii is an intracellular bacterium and the cause of the zoonotic infection, Q fever. National surveillance data on C. burnetii seroprevalence is currently not available for any South American country, making efforts of public health to implement strategies to mitigate infections in [...] Read more.
Coxiella burnetii is an intracellular bacterium and the cause of the zoonotic infection, Q fever. National surveillance data on C. burnetii seroprevalence is currently not available for any South American country, making efforts of public health to implement strategies to mitigate infections in different at-risk groups within the population extremely challenging. In the current study, we used two commercial anti-C. burnetii immunoassays to screen sera collected from a sample of the Chilean population as part of a 2016–2017 national health survey (n = 5166), nationwide and age-standardized. The seroprevalence for C. burnetii for persons ≥ 15 years was estimated to be 3.0% (95% CI 2.2–4.0), a level similar to national surveys from The Netherlands (2.4%) and USA (3.1%), but lower than Australia (5.6%). A linear increase of C. burnetii seropositivity was associated with an individual’s age, with the peak seroprevalence 5.6% (95% CI 3.6–8.6) observed in the ≥65 years’ group. C. burnetii seropositivity was significantly higher in the southern macro-zone 6.0% (95% CI 3.3–10.6) compared to metropolitan region 1.8% (95% CI 0.9–3.3), the former region being home to significant livestock industries, particularly dairy farming. These data will be useful to inform targeted strategies for the prevention of Q fever in at-risk populations in Chile. Full article
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7 pages, 2057 KiB  
Article
Scrub Typhus and Molecular Characterization of Orientia tsutsugamushi from Central Nepal
by Rajendra Gautam, Keshab Parajuli, Mythili Tadepalli, Stephen Graves, John Stenos and Jeevan Bahadur Sherchand
Pathogens 2021, 10(4), 422; https://doi.org/10.3390/pathogens10040422 - 01 Apr 2021
Cited by 2 | Viewed by 2814
Abstract
Scrub typhus is a vector-borne, acute febrile illness caused by Orientia tsutsugamushi. Scrub typhus continues to be an important but neglected tropical disease in Nepal. Information on this pathogen in Nepal is limited to serological surveys with little information available on molecular [...] Read more.
Scrub typhus is a vector-borne, acute febrile illness caused by Orientia tsutsugamushi. Scrub typhus continues to be an important but neglected tropical disease in Nepal. Information on this pathogen in Nepal is limited to serological surveys with little information available on molecular methods to detect O. tsutsugamushi. Limited information exists on the genetic diversity of this pathogen. A total of 282 blood samples were obtained from patients with suspected scrub typhus from central Nepal and 84 (30%) were positive for O. tsutsugamushi by 16S rRNA qPCR. Positive samples were further subjected to 56 kDa and 47 kDa molecular typing and molecularly compared to other O. tsutsugamushi strains. Phylogenetic analysis revealed that Nepalese O. tsutsugamushi strains largely cluster together and cluster away from other O. tsutsugamushi strains from Asia and elsewhere. One exception was the sample of Nepal_1, with its partial 56 kDa sequence clustering more closely with non-Nepalese O. tsutsugamushi 56 kDa sequences, potentially indicating that homologous recombination may influence the genetic diversity of strains in this region. Knowledge on the circulating strains in Nepal is important to the development of diagnostic tests and vaccines to support public health measures to control scrub typhus in this country. Full article
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10 pages, 714 KiB  
Article
Murine Typhus Infection in Pregnancy: Case Series and Literature Review
by Melinda B. Tanabe, Lucas S. Blanton, Mauricio La Rosa and Camille M. Webb
Pathogens 2021, 10(2), 219; https://doi.org/10.3390/pathogens10020219 - 18 Feb 2021
Cited by 4 | Viewed by 3309
Abstract
Murine typhus is a flea-borne disease of worldwide distribution with a recent reemergence in the United States of America. There are limited data about the presentation, treatment, and outcomes in the pregnant population. We report on two cases of murine typhus during pregnancy [...] Read more.
Murine typhus is a flea-borne disease of worldwide distribution with a recent reemergence in the United States of America. There are limited data about the presentation, treatment, and outcomes in the pregnant population. We report on two cases of murine typhus during pregnancy and review the literature to compile previously reported cases. A comprehensive search was performed via the PubMed database for published articles between 1990 and 2020. Seven articles met the criteria of symptomatic pregnant murine typhus infection. A total of 37 patients were identified. Patients frequently presented with a prolonged duration of fevers prior to presentation, headache, and elevated hepatic transaminases. The diagnosis was predominantly based on serology. Treatment varied. Overall, the pregnancy outcome was favorable. Murine typhus can mimic other pregnancy-related pathologies. More exclusive and large-scale studies are needed to learn more of murine typhus during pregnancy. Full article
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11 pages, 1735 KiB  
Article
Amplicon-Based Next Generation Sequencing for Rapid Identification of Rickettsia and Ectoparasite Species from Entomological Surveillance in Thailand
by Suwanna Chaorattanakawee, Achareeya Korkusol, Bousaraporn Tippayachai, Sommai Promsathaporn, Betty K. Poole-Smith and Ratree Takhampunya
Pathogens 2021, 10(2), 215; https://doi.org/10.3390/pathogens10020215 - 16 Feb 2021
Cited by 9 | Viewed by 2587
Abstract
Background: Next generation sequencing (NGS) technology has been used for a wide range of epidemiological and surveillance studies. Here, we used amplicon-based NGS to species identify Rickettsia and their arthropod hosts from entomological surveillance. Methods: During 2015–2016, we screened 1825 samples of rodents [...] Read more.
Background: Next generation sequencing (NGS) technology has been used for a wide range of epidemiological and surveillance studies. Here, we used amplicon-based NGS to species identify Rickettsia and their arthropod hosts from entomological surveillance. Methods: During 2015–2016, we screened 1825 samples of rodents and ectoparasites collected from rodents and domestic mammals (dog, cat, and cattle) across Thailand for Rickettsia. The citrate synthase gene was amplified to identify Rickettsia to species, while the Cytochrome Oxidase subunit I (COI) and subunit II (COII) genes were used as target genes for ectoparasite identification. All target gene amplicons were pooled for library preparation and sequenced with Illumina MiSeq platform. Result: The highest percentage of Rickettsia DNA was observed in fleas collected from domestic animals (56%) predominantly dogs. Only a few samples of ticks from domestic animals, rodent fleas, and rodent tissue were positive for Rickettisia DNA. NGS based characterization of Rickettsia by host identified Rickettsia asembonensis as the most common bacteria in positive fleas collected from dogs (83.2%) while “Candidatus Rickettsia senegalensis” was detected in only 16.8% of Rickettsia positive dog fleas. Sequence analysis of COI and COII revealed that almost all fleas collected from dogs were Ctenocephalides felis orientis. Other Rickettsia species were detected by NGS including Rickettsia heilongjiangensis from two Haemaphysalis hystricis ticks, and Rickettsia typhi in two rodent tissue samples. Conclusion: This study demonstrates the utility of NGS for high-throughput sequencing in the species characterization/identification of bacteria and ectoparasite for entomological surveillance of rickettsiae. A high percentage of C. f. orientis are positive for R. asembonensis. In addition, our findings indicate there is a risk of tick-borne Spotted Fever Group rickettsiosis, and flea-borne murine typhus transmission in Tak and Phangnga provinces of Thailand. Full article
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27 pages, 979 KiB  
Systematic Review
Rickettsiales in Italy
by Cristoforo Guccione, Claudia Colomba, Manlio Tolomeo, Marcello Trizzino, Chiara Iaria and Antonio Cascio
Pathogens 2021, 10(2), 181; https://doi.org/10.3390/pathogens10020181 - 08 Feb 2021
Cited by 20 | Viewed by 3906
Abstract
There is no updated information on the spread of Rickettsiales in Italy. The purpose of our study is to take stock of the situation on Rickettsiales in Italy by focusing attention on the species identified by molecular methods in humans, in bloodsucking arthropods [...] Read more.
There is no updated information on the spread of Rickettsiales in Italy. The purpose of our study is to take stock of the situation on Rickettsiales in Italy by focusing attention on the species identified by molecular methods in humans, in bloodsucking arthropods that could potentially attack humans, and in animals, possible hosts of these Rickettsiales. A computerized search without language restriction was conducted using PubMed updated as of December 31, 2020. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology was followed. Overall, 36 species of microorganisms belonging to Rickettsiales were found. The only species identified in human tissues were Anaplasma phagocytophilum,Rickettsia conorii, R. conorii subsp. israelensis, R. monacensis, R. massiliae, and R. slovaca. Microorganisms transmissible by bloodsucking arthropods could cause humans pathologies not yet well characterized. It should become routine to study the pathogens present in ticks that have bitten a man and at the same time that molecular studies for the search for Rickettsiales can be performed routinely in people who have suffered bites from bloodsucking arthropods. Full article
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9 pages, 969 KiB  
Article
Beyond the IFA: Revisiting the ELISA as a More Sensitive, Objective, and Quantitative Evaluation of Spotted Fever Group Rickettsia Exposure
by Navatha Alugubelly, John V. Stokes, Claire E. Cross, Anne-Marie L. Ross, Anna E. Crawford, Gabrielle F. Fiihr and Andrea S. Varela-Stokes
Pathogens 2021, 10(2), 88; https://doi.org/10.3390/pathogens10020088 - 20 Jan 2021
Cited by 4 | Viewed by 2192
Abstract
Based on limited serological studies, at least 10% of the US population has been exposed to spotted fever group Rickettsia (SFGR) species. The immunofluorescence antibody assay (IFA) has been the gold standard for the serodiagnosis of rickettsial infections such as spotted fever rickettsiosis [...] Read more.
Based on limited serological studies, at least 10% of the US population has been exposed to spotted fever group Rickettsia (SFGR) species. The immunofluorescence antibody assay (IFA) has been the gold standard for the serodiagnosis of rickettsial infections such as spotted fever rickettsiosis (SFR). However, the IFA is semi-quantitative and subjective, requiring a high level of expertise to interpret it correctly. Here, we developed an enzyme-linked immunosorbent assay (ELISA) for the serodiagnosis of Rickettsia parkeri infection in the guinea pig. Our ELISA is an objective, quantitative, and high-throughput assay that shows greater sensitivity and resolution in observed titers than the IFA. We methodically optimized relevant parameters in sequence for optimal signal-to-noise ratio and low coefficient of variation% values. We used a guinea pig model as it is a part of our overall research efforts to understand the immunological and clinical response to SFGR species after tick transmission. Guinea pigs are a useful model to study SFR and show clinical signs of SFR, such as fever and eschars. We anticipate that this assay will be easily adapted to other hosts, including humans and other SFGR species. Full article
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9 pages, 836 KiB  
Article
Molecular Evidence of Novel Spotted Fever Group Rickettsia Species in Amblyomma albolimbatum Ticks from the Shingleback Skink (Tiliqua rugosa) in Southern Western Australia
by Mythili Tadepalli, Gemma Vincent, Sze Fui Hii, Simon Watharow, Stephen Graves and John Stenos
Pathogens 2021, 10(1), 35; https://doi.org/10.3390/pathogens10010035 - 05 Jan 2021
Cited by 7 | Viewed by 2607
Abstract
Tick-borne infectious diseases caused by obligate intracellular bacteria of the genus Rickettsia are a growing global problem to human and animal health. Surveillance of these pathogens at the wildlife interface is critical to informing public health strategies to limit their impact. In Australia, [...] Read more.
Tick-borne infectious diseases caused by obligate intracellular bacteria of the genus Rickettsia are a growing global problem to human and animal health. Surveillance of these pathogens at the wildlife interface is critical to informing public health strategies to limit their impact. In Australia, reptile-associated ticks such as Bothriocroton hydrosauri are the reservoirs for Rickettsia honei, the causative agent of Flinders Island spotted fever. In an effort to gain further insight into the potential for reptile-associated ticks to act as reservoirs for rickettsial infection, Rickettsia-specific PCR screening was performed on 64 Ambylomma albolimbatum ticks taken from shingleback skinks (Tiliqua rugosa) located in southern Western Australia. PCR screening revealed 92% positivity for rickettsial DNA. PCR amplification and sequencing of phylogenetically informative rickettsial genes (ompA, ompB, gltA, sca4, and 17kda) suggested that the single rickettsial genotype detected represented a novel rickettsial species, genetically distinct from but closely related to Rickettsia gravesii and within the rickettsia spotted fever group (SFG). On the basis of this study and previous investigations, it would appear that Rickettsia spp. are endemic to reptile-associated tick species in Australia, with geographically distinct populations of the same tick species harboring genetically distinct SFG Rickettsia species. Further molecular epidemiology studies are required to understand the relationship between these diverse Rickettsiae and their tick hosts and the risk that they may pose to human and animal health. Full article
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2020

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10 pages, 242 KiB  
Article
Screening for Rickettsia, Coxiella and Borrelia Species in Ticks from Queensland, Australia
by Hazizul Hussain-Yusuf, John Stenos, Gemma Vincent, Amy Shima, Sandra Abell, Noel D. Preece, Mythili Tadepalli, Sze Fui Hii, Naomi Bowie, Kate Mitram and Stephen Graves
Pathogens 2020, 9(12), 1016; https://doi.org/10.3390/pathogens9121016 - 02 Dec 2020
Cited by 8 | Viewed by 2847
Abstract
Tick bites in Australia are linked to the transmission of a variety of infectious diseases in humans, livestock and wildlife. Despite this recognition, little is currently known about the variety of potential pathogens that are carried and transmitted by Australian ticks. In this [...] Read more.
Tick bites in Australia are linked to the transmission of a variety of infectious diseases in humans, livestock and wildlife. Despite this recognition, little is currently known about the variety of potential pathogens that are carried and transmitted by Australian ticks. In this study, we attempted to expand knowledge of Australian tick-borne bacterial pathogens by analyzing various tick species from the state of Queensland for potential human pathogens belonging to the Rickettsia, Coxiella and Borrelia genera. A total of 203 ticks, comprising of four genera and nine different tick species, were screened by specific qPCR assays. An overall Rickettsia qPCR positivity of 6.4% (13/203) was detected with rickettsial DNA found in four tick species (Ixodes holocyclus, I. tasmani, Amblyommatriguttatum, and Haemaphysalis longicornis). Amplification and analysis of several rickettsial genes from rickettsial qPCR positive samples identified sequences closely related to but genetically distinct from several previously described cultured and uncultured rickettsial species in the Rickettsia spotted fever subgroup. No ticks were positive for either Coxiella or Borrelia DNA. This work suggests that a further diversity of rickettsiae remain to be described in Australian ticks with the full importance of these bacteria to human and animal health yet to be elucidated. Full article
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