Genotype diversity and distribution of Orientia tsutsugamushi in scrub typhus patients and rodents in Shandong,northern China

Orientia tsutsugamushi, the etiologic agent of scrub typhus, is transmitted to humans through the bites of infected chiggers. To identify the genotypes of O.tsutsugamushi and their geographical distribution in Shandong, 236 patient's samples and 1606 captured rodents were collected in major-endemic regions of Shandong Province from June 2013 to December 2014. Sequences were determined for the 56-kDa TSA gene, and the relationship between these sequences and those previously determined was assessed. Two genotypes out of 5 previously reported in Shandong were identified, i.e. Kawasaki-related and STA-07. The Kawasaki-related genotype was predominant (82.1% (23/28) in human and 50% (5/10) in rodents), with wide distribution through the endemic areas of Shandong Province. The STA-07 was confined to Tai'an, Linyi and Qingdao districts. The Fuji-related, Shimikoshi-related and Karp-related genotypes were not found, while identified in previous studies. For prevention and control of scrub typhus in Shandong, more attention should be paid to surveillance of Kawasaki-related and STA-07 genotypes.     

Genetic Variants of Orientia tsutsugamushi in Domestic Rodents,Northern China

We screened Orientia tsutsugamushi from 385 domestic rodents and 19 humans with scrub typhus in rural Tai’an District, Shandong Province, a new scrub typhus epidemic area in northern China. Sequence analysis identified 7 genotypes in the rodents, of which 2 were also identified in the humans.     

Acute Q Fever and Scrub Typhus, Southern Taiwan

Acute Q fever and scrub typhus are zoonoses endemic to southern Taiwan. Among the 137 patients with acute Q fever (89, 65.0%) or scrub typhus (43, 31.4%), we identified 5 patients (3.6%) who were co-infected with Coxiella burnetii and Orientia tsutsugamushi.     

Molecular Epidemiology and Genetic Diversity of Orientia tsutsugamushi from Patients with Scrub Typhus in 3 Regions of India

Scrub typhus, an acute febrile illness that is widespread in the Asia-Pacific region, is caused by the bacterium Orientia tsutsugamushi, which displays high levels of antigenic variation. We conducted an investigation to identify the circulating genotypes of O. tsutsugamushi in 3 scrub typhus–endemic geographic regions of India: South India, Northern India, and Northeast India. Eschar samples collected during September 2010–August 2012 from patients with scrub typhus were subjected to 56-kDa type-specific PCR and sequencing to identify their genotypes. Kato-like strains predominated (61.5%), especially in the South and Northeast, followed by Karp-like strains (27.7%) and Gilliam and Ikeda strains (2.3% each). Neimeng-65 genotype strains were also observed in the Northeast. Clarifying the genotypic diversity of O. tsutsugamushi in India enhances knowledge of the regional diversity among circulating strains and provides potential resources for future region-specific diagnostic studies and vaccine development.     

Broad-coverage molecular epidemiology of Orientia tsutsugamushi in Thailand

Orientia tsutsugamushi, an obligate intracellular bacterium closely related to the genus Rickettsia, is the causative agent of scrub typhus, a major cause of febrile illness in rural areas of Asia–Pacific region. Scrub typhus is transmitted by the bite of infected mites of the genus Leptotrombidium. The region of the 56-kDa TSA gene spanning from variable domain I (VDI) to variable domain IV (VDIV) was sequenced and used for genotyping 77 O. tsutsugamushi samples from human patients confirmed with scrub typhus from 2001 to 2003 and 2009 to 2010 in different regions of Thailand. These sequences were also compared to previously published 56-kDa TSA sequences. Only 4 genotypes out of 8 previously reported in Thailand were identified, i.e. Karp, JG-v, TA763 and Kato, respectively. Two strains were not associated with known genotypes but were closely related to Taiwanese strains. The Karp genotype was confirmed as the predominant clade. The JG-v and TA763 genotypes, in contrast to other studies, also were found. The genotype TA716 was not found, except for one strain previously described.     

Single dose doxycycline therapy for scrub typhus

A single dose of 200 mg of doxycycline was shown to be as effective as a seven day course of tetracycline, in patients suspected of having scrub typhus. 65 (44%) of the 149 patients studied fulfilled the criteria for definite diagnosis of scrub typhus; 10 had an additional diagnosis. Rickettsia tsutsugamushi was isolated from 49 (75%) patients. There was no difference between the two treatment groups in time to defervescence, abolition of cough and headache, or in the time taken to recover well-being. There were no relapses in either group.Of the remaining 84 patients, a causal diagnosis was achieved in 52. Irrespective of a diagnosis there was no difference in apparent response to either doxycycline or tetracycline.     

套式-聚合酶链反应在山东省恙虫病检测中的应用

目的 :利用分子生物学手段对山东省部分地区的人和鼠进行调查 ,了解恙虫病在山东省的感染情况。方法 :采用套式 -聚合酶链反应 (nested- PCR)技术 ,对在山东省 6个市 (县、区 )捕获的野鼠或家鼠的肝、脾、肾组织标本 ,以及临床诊断为恙虫病的病人血标本进行检测。结果 :共检测鼠脏器标本 198份 ,阳性 8份 ,阳性率为 4 .2 4 % ;共检测临床诊断恙虫病病人血标本 14份 ,阳性 7份 ,阳性率为 5 0 %。结论 :首次在山东省黄河以北地区捕获的鼠体内检测到恙虫病东方体 ,其中两只鼠为褐家鼠 ,表明山东省广泛存在恙虫病的自然疫源地     

Transmission Electron Microscopy Confirmation of Orientia tsutsugamushi in Human Bile

Scrub typhus, the third most frequently reported infectious disease in South Korea, causes serious public health problems. In 2019, we collected a bile specimen from a patient with scrub typhus through percutaneous transhepatic gallbladder drainage and performed transmission electron microscopy to confirm the ultrastructure of Orientia tsutsugamushi.     

Spatial Distribution Analysis of Scrub Typhus in Korea

ObjectiveThis study analyzes the spatial distribution of scrub typhus in Korea.MethodsA spatial distribution of Orientia tsutsugamushi occurrence using a geographic information system (GIS) is presented, and analyzed by means of spatial clustering and correlations.ResultsThe provinces of Gangwon-do and Gyeongsangbuk-do show a low incidence throughout the year. Some districts have almost identical environmental conditions of scrub typhus incidence. The land use change of districts does not directly affect the incidence rate.ConclusionGIS analysis shows the spatial characteristics of scrub typhus. This research can be used to construct a spatial-temporal model to understand the epidemic tsutsugamushi.     

Diversity of Orientia tsutsugamushi clinical isolates in Cambodia reveals active selection and recombination process

Orientia tsutsugamushi, the causative agent of scrub typhus in South East Asia and Pacific, is an obligate intracellular bacterium closely related to the Rickettsia. The pathogen is transmitted to humans through the bites of infected larvae of trombiculid mites of the genus Leptotrombidium in which is maintained trough vertical transmission mechanism. The infection in rodents has been described in over 20 species. Scrub typhus is commonly confused with other tropical fevers and late diagnosis and treatment can lead to severe organ failures and a strain-dependent mortality rate of up to 50%. A MLST scheme associating seven core function genes: adk, lepB, lipA, lipB, secY, sodB and sucA was developed and validated on seven Cambodian strains detected in patients and two complete reference genomes from Korea and Japan. Sequence data were analyzed both with respect to sequence type (ST) diversity and DNA polymorphism. Differing trends were revealed. DNA polymorphism and phylogeny of individual gene loci indicated a significant level of recombination and genetic diversity. However, the ST distribution is clearly clonal and the clinical situation can be summarized by the formula: one patient, one strain, one ST. This contradiction is only apparent and is most likely the consequence of the unique life cycle of O. tsutsugamushi. The quasi exclusive vertical transmission mode in mites generates repeated bottlenecks and small-size populations and strongly limits genetic diversity. O. tsutsugamushi has developed specific mechanisms for generating genetic diversity which include recombination, duplication and conjugation. Recombination and other mechanisms for increasing genetic diversity are likely to occur in rodents which can act as maintenance hosts, although occurrence in mites cannot be excluded. Consequences for the epidemiology of scrub typhus are discussed.     

Rickettsioses in Australia: isolation of Rickettsia tsutsugamushi and R. australis from naturally infected arthropods

The vectors of scrub typhus and Queensland tick typhus have not previously been positively identified in Australia. Small mammals were trapped at Mossman (north Queensland) and 4 strains of Rickettsia tsutsugamushi were isolated in mice inoculated with suspensions of Leptotrombidium deliense removed from bandicoots. No strains were isolated from unfed, larval L. deliense collected from the forest floor, but 21 further strains were obtained from tissues of 141 animals of 5 species.A focus of infected ticks was defined when cases of Queensland tick typhus were identified in soldiers at Canungra (S.E. Queensland). Rickettsia australis was subsequently isolated in suckling mice from 2 pools of scrub ticks (Ixodes holocyclus) and 1 pool of I. tasmani.     

Recent studies on scrub typhus and Rickettsia tsutsugamushi in Shandong Province - China

In an outbreak of scrub typhus occurred 138 cases in 1986 in Menying County of Shandong Province of China which were confirmed through clinical and epidemiological surveys and laboratory techniques. In the endemic areas, the predominant species of mite is Leptotrombidium (L.) scutelarae and the predominat rodent is Apodemus agrarius, which may be the main vector and reservoir. Several strains of Rickettsia tsutsugamushi (R.T.) were obtained from mites, wild mice and patients, of which 3 human strains (SDH871, SDH875, SDH878) cause illness and some deaths in mice, except SDH871. The LD50 of SDH878 is 3.4. Cross-protection was observed among the strains, SDH871, SDH878, and prototype strain karp. Also the antibodies in mucoid peritoneal fluid were detectable with high titer. Shandong R.T. belongs to the serotype of the Gilliam strain.Presented at the 4th International Symposium on Rickettsiae and Rickettsial Diseases, Pietany, C.S.F.R., 1–6 October, 1990.     

The longevity of antibody to Rickettsia tsutsugamushi in patients with confirmed scrub typhus

Serological surveillance for up to two years of 114 patients with laboratory confirmed scrub typhus showed that antibody to Rickettsia tsutsugamushi as demonstrated by the indirect fluorescent antibody test is short-lived. The mean reversion time from mean peak titre (1:499) was 48·9 weeks and the calculated annual reversion rate to a titre <1:50 was 61%. This can be used to estimate attack rates based on point prevalence of antibody. The relationship between antibody prevalence and attack rates observed by other workers was confirmed using this model. The possible uses of the finding and its implications in Malaysia are briefly discussed.     

Epidemiological Characteristics of Scrub Typhus in Korea, 2009

Objectives

Currently, the incidence of scrub typhus has increased in urban areas. In this study, we described the epidemiological characteristics of scrub typhus cases reported in the urban areas of Korea in 2009.

Methods

We analysed the case investigation reports of scrub typhus cases that were collected in Korea in 2009. Specially, the different risk factors such as fieldwork and outdoor activity were compared to urban and rural areas, and six urban cities. Statistical analysis was performed using χ² test.

Results

A total of 4,461 cases (including 1,663 suspected cases) were analysed in this study. Among these, the case reports of 4,254 cases had complete addresses. The cases with outdoor activities were 720 (85.2%) in urban areas. In Daegu and Daejeon, the number of cases participated in outdoor activities was 32 (34.4%) and 23 (31.5%), respectively. In other urban areas, cases with outdoor activities were more than 85%.

Conclusion

The most common infection risk factor was outdoor activity in urban areas. However, the proportion and distribution of outdoor activities were different in urban areas. These results will be used to establish strategies for effective prevention and management in urban areas.Key words: epidemiology, korea, Orientia tsutsugamushi, scrub typhus     

Epidemiological and serological study of scrub typhus among Chinese military in the Pescadores islands of Taiwan.

An outbreak of 69 cases of scrub typhus occurred among Chinese military personnel stationed in the Pescadores Islands, Taiwan Province, Republic of China between May and November 1975. A retrospective epidemiological study of this outbreak indicated that military personnel over 40 were more likely to have scrub typhus than those under 40. High risk groups included the Garrison Force (home guard), anti-aircraft gunners and infantry and armoured units stationed at Hsing-jen. The onset of symptoms in 69% occurred within one year of residence in the Pescadores. The clinical course of scrub typhus and the serological response to infection were also studied. Eschar formation, fever, headache chills and lymph node enlargement were the predominant clinical manifestations noted. The indirect immunofluorescent antibody test (IFAT) demonstrated diagnostic (four-fold) rises in antibody titres to Rickettsia tsutsugamushi reference strains in 36 of 41 paired sera tested. 11 of 19 patients from whom only single sera were obtained had IFA titres presumptive of scrub typhus (greater than or equal to 1:160). Of 19 patients experiencing possible primary infections, 13 (68%) responded with antibodies directed against more than one reference strain of R. tsutsugamushi. These results suggest that several antigenically diverse strains of R. tsutsugamushi may be active in the Pescadores.     

Orientia tsutsugamushi in eschars from scrub typhus patients

To verify the value of eschars for the diagnosis of scrub typhus and to characterize genotypes of Orientia tsutsugamushi in patients, we examined eschars and blood specimens of 7 patients from Shandong Province, People's Republic of China, for O. tsutsugamushi by polymerase chain reaction targeting the Sta56 gene. All 7 eschars and acute-phase blood samples were positive, while no specific DNA amplicons were obtained from the 7 convalescent-phase blood samples collected after antimicrobial drug therapy. The findings indicate that patients' eschars can be used for detection and genetic characterization of O. tsutsugamushi during the convalescent phase.     

山东省恙虫病血清流行病学调查研究

目的：对山东省不同地区人间和鼠间恙虫病感染情况进行较为全面的了解。方法：采用IFAT、M—CFT等血清学方法在全省10个市开展不同人群间和鼠间调查。结果：首次在我省黄河以北地区检出恙虫病感染鼠；在我省褐家鼠中检出恙虫病立克次体抗体，血清学显示其感染率达10％；通过血清学检查还从大仓鼠中检出恙虫病立克次体抗体，其感染率达15．63％。通过血清学方法证实我省潍坊、菏泽存在恙虫病人间感染。结论：我省广泛存在恙虫病疫区，黑线姬鼠为主要传染源，其血清学阳性率达19．46％，但褐家鼠甚至包括大仓鼠也有可能是本病的重要传染源；山东省恙虫病的流行极有可能存在多样性。     

安徽省2008-2017年恙虫病流行特征与重复感染分析

  目的  了解安徽省2008-2017年恙虫病流行特征,为制定防治策略和控制措施提供科学依据。  方法  采用描述流行病学方法对2008-2017年安徽省恙虫病病例进行描述分析。  结果  2008-2017年安徽省恙虫病整体发病呈上升趋势（χ2=3 522.49,P<0.001）,2016年发病率最高为3.98/10万;病例明显集中在9月份~11月份,属于典型的“秋冬型”,10月达到高峰,具有“10月高发”现象;病例主要集中在40~79岁年龄段,占总报告病例数的76.64%,60~69岁年龄段累计病例数最多,发病以农民为主。  结论  近年来,安徽省恙虫病发病整体呈上升趋势,需加强对重点地区恙虫病的日常监测工作和恙虫病病原检测工作,积极开展恙虫病的防治与健康教育工作。     

Human seroepidemiology of Rickettsia and Orientia species in Chile – A cross-sectional study in five regions

In recent years, the spectrum and epidemiology of human rickettsioses has become an emerging topic in Chile. This survey aimed to assess the seroprevalence of spotted fever group rickettsiae (SFGR), typhus group rickettsiae (TGR), and scrub typhus group orientiae (STGO) in northern, central, and southern Chile. We performed a cross-sectional study of healthy adults in rural and urban settings of five regions. Participants were chosen by double stratified random sampling in urban and by convenience in rural locations (n = 1302). Serum specimens were analyzed for group-specific IgG antibodies against SFGR, TGR, and STGO by enzyme-linked immunosorbent assays (ELISAs). Overall seroprevalences to SFGR, TGR, and STGO were 5.3 %, 1.2 %, and 0.4 %, respectively. Prevalences showed geographical differences. Statistical analyses revealed an association of older age with seropositivity to SFGR and to TGR and of rural setting and male gender with seropositivity to SFGR. The study indicates that SFGR, TGR, and STGO are endemic in Chile. The very low STGO seroprevalence might indicate an insufficient sensitivity of serological tests using Asian O. tsutsugamushi strains as ELISA antigens for the detection of antibodies against Chilean Orientia species.