Orientia tsutsugamushi Infection

A special issue of Pathogens (ISSN 2076-0817).

Deadline for manuscript submissions: closed (15 March 2022) | Viewed by 6751

Special Issue Editor


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Guest Editor
Department of Microbiology, College of Medicine, Hanyang University, Seoul, Korea
Interests: epidemiology of infectious disease; disease surveillance

Special Issue Information

Dear Colleagues,

Scrub typhus is a life-threatening mite-borne infectious disease caused by Orientia tsutsugamushi, and it is transmitted primarily by the bite of the larvae of Leptotrombidium spp. mite (Acari: Trombiculiidae) infected with Orientia species.

The disease is endemic in Asian countries and the western Pacific area, an area known as the “tsutsugamushi triangle”, and causes an estimated one million cases annually.

Recently, scrub typhus has also been reported outside the usual endemic region, in areas such as South American and African countries, far from the tsutsugamushi triangle, which suggests a wider global distribution of this disease and is attracting more attention to the neglected disease. Nevertheless, the global incidence of scrub typhus is poorly defined because of the limited epidemiological data in many of the endemic countries.

After a bite from an infective mite, a characteristic necrotic inoculation lesion (an eschar) can develop, and the signs and symptoms of scrub typhus typically develop within 1–2 weeks of infection and include fever, headache, malaise, and gastrointestinal symptoms.

Coinfection with both single or different genotypes of O. tsutsugamushi and severe fever with thrombocytopenia syndrome virus (SFTSV), a new emerging tick-borne virus, could also occur in the patient.

Despite recent strides in fundamental research and the development of medical countermeasures for scrub typhus, much remains to be learned about many of these agents in order to aid our understanding of bacterial pathogenesis and for the identification and development of therapeutics and vaccines.

This Special Issue will cover a wide range of topics focusing on scrub typhus, and aims to help to enhance current knowledge of this bacteria and their respective diseases. All types of articles will be considered for publication, including short reports, primary research articles, and reviews.

We look forward to your contribution.


Prof. Dr. Keun Hwa Lee
Guest Editor

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Keywords

  • Scrub typhus
  • Orientia tsutsugamushi
  • Mite-borne diseases
  • Bacteria-host interactions
  • Virulence factors
  • Bacterial pathogenesis
  • Transmission
  • Immune activation and evasion
  • Innate immunity
  • Adaptive immunity
  • Therapeutics
  • Vaccines

Published Papers (3 papers)

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Research

12 pages, 8881 KiB  
Article
A Murine Model of Waning Scrub Typhus Cross-Protection between Heterologous Strains of Orientia tsutsugamushi
by Nicole L. Mendell, Guang Xu, Thomas R. Shelite, Donald H. Bouyer and David H. Walker
Pathogens 2022, 11(5), 512; https://0-doi-org.brum.beds.ac.uk/10.3390/pathogens11050512 - 26 Apr 2022
Cited by 2 | Viewed by 1730
Abstract
Orientia tsutsugamushi, the etiologic agent of the life-threatening febrile disease scrub typhus, is an obligately intracellular small coccobacillary bacterium belonging to the family Rickettsiaceae and is transmitted by the parasitic larval stage of trombiculid mites. Progress towards a vaccine for protection against [...] Read more.
Orientia tsutsugamushi, the etiologic agent of the life-threatening febrile disease scrub typhus, is an obligately intracellular small coccobacillary bacterium belonging to the family Rickettsiaceae and is transmitted by the parasitic larval stage of trombiculid mites. Progress towards a vaccine for protection against scrub typhus has been impeded by characteristics of the pathogen and the infection. There are numerous strains of O. tsutsugamushi in the Asia-Pacific region with geographical overlap. In human cases immunity has been described as poor against heterologous strains of the pathogen, as well as short-lived against the homologous strain, with a mean antibody reversion rate of less than one year. Animal models of cross-protection as well as of deterioration of this cross-protection are needed to enhance understanding of transient immunity to scrub typhus. To build upon current understanding of this ineffective protection we sought to utilize our recently developed models, sublethal intradermal infection followed by challenge via ordinarily lethal hematogenous dissemination. Mice that were initially infected sublethally with O. tsutsugamushi Gilliam strain and were challenged with an ordinarily lethal dose of heterologous Karp strain were protected from death by a robust immune response at one month after the primary infection as evidenced by an abundance of mononuclear cellular infiltrates in target organs such as lung, liver, and kidney; maintenance of body weight; and low bacterial loads in the organs. Waning protection from lethal Karp strain challenge indicated by weight loss mirroring that observed in naïve mice was observed as early as 9 months after primary Gilliam strain infection, and higher bacterial loads, severe disease, and eventual death in some mice was observed after challenge with Karp strain at 14 months post-initial heterologous infection. Full article
(This article belongs to the Special Issue Orientia tsutsugamushi Infection)
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9 pages, 2120 KiB  
Article
Halved Incidence of Scrub Typhus after Travel Restrictions to Confine a Surge of COVID-19 in Taiwan
by En-Cheng Lin, Hung-Pin Tu and Chien-Hui Hong
Pathogens 2021, 10(11), 1386; https://0-doi-org.brum.beds.ac.uk/10.3390/pathogens10111386 - 27 Oct 2021
Cited by 5 | Viewed by 1891
Abstract
Scrub typhus is a rickettsial disease that is usually transmitted by mite exposure. Infected patients may present with a fever, fatigue, headache, and muscle pain. A blackish skin lesion, called eschar, is pathognomic. The mortality rate in untreated cases is high. The first [...] Read more.
Scrub typhus is a rickettsial disease that is usually transmitted by mite exposure. Infected patients may present with a fever, fatigue, headache, and muscle pain. A blackish skin lesion, called eschar, is pathognomic. The mortality rate in untreated cases is high. The first case of scrub typhus in Taiwan was reported in 1908 during the Japanese colonization. In this article, using the National Infectious Disease Statistics System (NIDSS) from the Taiwan CDC, we analyzed the dynamic incidence of scrub typhus from 2016 to 2021, both seasonally and geographically. In addition, we asked whether the recent travel restrictions and social distancing policy in Taiwan (19 May to 27 July 2021), implemented due to the COVID-19 outbreak, would change the incidence of scrub typhus. The results showed that scrub typhus was most common in summer, with an incidence almost twofold greater than that in winter or spring. Most cases were identified in rural regions. Interestingly, there was a significant 52% reduction in the summer incidence in 2021, compared to the average summer incidence of the past 5 years. This reduction coincided with the countrywide lockdown measures and travel restrictions. The restricted measures for outdoor activities may have contributed to the reduced incidence of scrub typhus. Full article
(This article belongs to the Special Issue Orientia tsutsugamushi Infection)
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18 pages, 2498 KiB  
Article
Establishment of a Rhesus Macaque Model for Scrub Typhus Transmission: Pilot Study to Evaluate the Minimal Orientia tsutsugamushi Transmission Time by Leptotrombidium chiangraiensis Chiggers
by Piyada Linsuwanon, Sirima Wongwairot, Nutthanun Auysawasdi, Taweesak Monkanna, Allen L. Richards, Surachai Leepitakrat, Piyanate Sunyakumthorn, Rawiwan Im-Erbsin, Katie Poole-Smith and Patrick McCardle
Pathogens 2021, 10(8), 1028; https://0-doi-org.brum.beds.ac.uk/10.3390/pathogens10081028 - 13 Aug 2021
Cited by 1 | Viewed by 2306
Abstract
Recently, an intradermal inoculation of the rhesus macaque model of scrub typhus has been characterized at our institution. The current project was to establish a rhesus macaque model of scrub typhus using the naturally infected chigger challenge method that faithfully mimics the natural [...] Read more.
Recently, an intradermal inoculation of the rhesus macaque model of scrub typhus has been characterized at our institution. The current project was to establish a rhesus macaque model of scrub typhus using the naturally infected chigger challenge method that faithfully mimics the natural route of pathogen transmission to fully understand the host-pathogen-vector interactions influencing pathogen transmission. Unlike the needle-based inoculation route, Orientia tsutsugamushi-infected chiggers introduce both pathogen and chigger saliva into the host epidermis at the bite site. However, information on the interaction or influence of chigger saliva on pathogenesis and immunity of host has been limited, consequently hindering vaccine development and transmission-blocking studies. To characterize chigger inoculated O. tsutsugamushi in rhesus macaques, we determined the minimum chigger attachment time required to efficiently transmit O. tsutsugamushi to the immunocompetent hosts and preliminary assessed clinical parameters, course of bacterial infection, and host’s immunological response to identifying potential factors influencing pathogen infection. Chigger infestation on hosts resulted in: (i) Rapid transmission of O. tsutsugamushi within 1 h and (ii) antigen-specific type I and II T-cell responses were markedly increased during the acute phase of infection, suggesting that both systems play critical roles in response to the pathogen control during the primary infection. In summary, we demonstrate that O. tsutsugamushi infection in rhesus macaques via chigger challenge recapitulates the time of disease onset and bacteremia observed in scrub typhus patients. Levels of proinflammatory cytokines and chemokines were positively correlated with bacteremia. Full article
(This article belongs to the Special Issue Orientia tsutsugamushi Infection)
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