Scrub typhus caused by Orientia tsutsugamushi Kawasaki-related genotypes in Shandong Province,northern China

Orientia tsutsugamushi, the causative agent of scrub typhus, is an obligate intracellular bacterium and characterized by dramatic genetic diversity. To elucidate the genotypes of O. tsutsugamushi populating in patients in Shandong Province, a new epidemic zone in China, we sequenced partial of the 56-kDa type-specific antigen gene (TSA) and identified the genotypes of 43 O. tsutsugamushi samples from human patients confirmed with scrub typhus from 2010 to 2013. All of the 43 sequences are in the same clade, 39 of them are in one branch and the other four sequences, nominated as SH1002, SH1306, SH1309, and SH1307 are in four separate branches. To clarify the clinical characterizations caused by Kawasaki-related genotypes, we studied the clinical profiles of these 43 scrub typhus patients. Most patients (88.1%) were farmers lived in rural areas. They presented with fever (100.0%), headache (79.1%), dizziness (32.6%), generalized myalgia (48.8%), fatigue (53.5%), anorexia (53.5%), facial flushing (23.3%), conjunctival congestion (11.6%), skin rashes (58.1%) and lymphadenopathy (23.3%). Eschar (97.7%) was quite common in patients, which provided doctors with a luminous clue for diagnosis of scrub typhus. Thrombocytopenia was seen in 23.1% of patients, and three patients (7.0%) had bronchopneumonia. There was no death report in Shandong Province during the study period. The present study provides beneficial data for clinical, serological, and molecular diagnosis of scrub typhus infections, and also provides foundations for subsequent studies.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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     

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.     

Orientia tsutsugamushi infection in rodents in Anhui Province of China

We conducted an investigation of Orientia tsutsugamushi infection among rodents in non-endemic areas in Anhui Province. Fifty-six (56) rodents including 44 Apodemus agrarius and 12 Niviventer niviventer were trapped and captured in autumn in the fields of three counties in Anhui Province. DNA samples were amplified and sequenced for the 56 kDa protein gene of Orientia tsutsugamushi. The overall infection rate in the rodents was 23.2%(13/56). The rate of detection of O. tsutsugamushi in Apodemus agrarius and Niviventer niviventer were 27.3% and 8.3% respectively. Moreover, we identified two genotypes (Karp and Gilliam strains) of Orientia tsutsugamushi in rodents. Our study demonstrated that Apodemus agrarius is the main host for O. tsutsugamushi pathogen and this is the first report of Karp and Gilliam strains in these non-endemic areas in Anhui Province.     

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.     

Indoor and Outdoor Rodent Hosts of Orientia tsutsugamushi,Shandong Province,China

During December 2012–July 2016, we tested small indoor and outdoor mammals in Qingdao, China, for Orientia tsutsugamushi infection. We found that outdoor Apodemus agrarius mice, Cricetulus barabensis hamsters, and Niviventer confucianus rats, as well as indoor Mus musculus mice, tested positive for O. tsutsugamushi by PCR.     

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.     

Targeted capture and sequencing of Orientia tsutsugamushi genomes from chiggers and humans

Scrub typhus is a febrile disease caused by Orientia tsutsugamushi, transmitted by larval stage Trombiculid mites (chiggers), whose primary hosts are small mammals. The phylogenomics of O. tsutsugamushi in chiggers, small mammals and humans remains poorly understood. To combat the limitations imposed by the low relative quantities of pathogen DNA in typical O. tsutsugamushi clinical and ecological samples, along with the technical, safety and cost limitations of cell culture, a novel probe-based target enrichment sequencing protocol was developed. The method was designed to capture variation among conserved genes and facilitate phylogenomic analysis at the scale of population samples. A whole-genome amplification step was incorporated to enhance the efficiency of sequencing by reducing duplication rates. This resulted in on-target capture rates of up to 93% for a diverse set of human, chigger, and rodent samples, with the greatest success rate in samples with real-time PCR C_t values below 35. Analysis of the best-performing samples revealed phylogeographic clustering at local, provincial and international scales. Applying the methodology to a comprehensive set of samples could yield a more complete understanding of the ecology, genomic evolution and population structure of O. tsutsugamushi and other similarly challenging organisms, with potential benefits in the development of diagnostic tests and vaccines.     

Geographic Divergence of Bovine and Human Shiga Toxin–Producing Escherichia coli O157:H7 Genotypes,New Zealand

Shiga toxin-producing Escherichia coli (STEC) O157:H7 is a zoonotic pathogen of public health concern worldwide. To compare the local and large-scale geographic distributions of genotypes of STEC O157:H7 isolates obtained from various bovine and human sources during 2008–2011, we used pulsed-field gel electrophoresis and Shiga toxin–encoding bacteriophage insertion (SBI) typing. Using multivariate methods, we compared isolates from the North and South Islands of New Zealand with isolates from Australia and the United States. The STEC O157:H7 population structure differed substantially between the 2 islands and showed evidence of finer scale spatial structuring, which is consistent with highly localized transmission rather than disseminated foodborne outbreaks. The distribution of SBI types differed markedly among isolates from New Zealand, Australia, and the United States. Our findings also provide evidence for the historic introduction into New Zealand of a subset of globally circulating STEC O157:H7 strains that have continued to evolve and be transmitted locally between cattle and humans.     

Trends in the Incidence of Scrub Typhus: The Fastest Growing Vector-Borne Disease in Korea

Scrub typhus, also called tsutsugamushi disease, is classified as a Group 3 disease in Korea according to the National Notifiable Diseases Surveillance Systems. It is an infectious disease transmitted to humans through the bite of mites that are infected with an intracellular parasite called Orientia tsutsugamushi (Family: Rickettsiaceae). This study aims to identify the demographic characteristics of the infected cases according to profession, region, gender, and onset period and provide a basic data for prevention and control of the disease in the infected patients. Between 2001 and 2010, 16,741 men (36.3%) and 29,373 women (63.7%) were reported to have been infected with scrub typhus, with men being 1.6 times less infected than women. When classified according to age, it was found that 4421 persons (9.6%) were under 40 years of age; 6601 (13.1%) in their 40s; 9714 (21.1%) in their 50s; 13,067 (28.3%) in 60s; 10,128 (22.0%) in their 70s; and 2723 (5.9%) aged 80 or more. The elderly (60 years or older) represented more than half of the infected cases. When the infections were classified according to region, it was found that the county residents had the major share of infection, with a total of 1583 infected cases (59.85).     

Technique and interpretation of the Weil-Felix test in typhus fever

Two different types of the curve of OX19 agglutinin formation are found in patients suffering from louse-borne typhus. The two types of reaction curve are related to the clinical course of the disease and form the basis for the interpretation of the results of the Weil-Felix test.Rickettsial vaccines stimulate demonstrable OX19 agglutinins in a relatively high proportion of inoculated persons. The OX19 antibody response is of a moderate degree, similar to the O antibody response after T.A.B. inoculation.Residual OX19 agglutinins, due to a previous attack of louse-borne typhus, do not show significant fluctuation of the titre in the course of various febrile diseases. It may be assumed that the same holds for OX19 agglutinins produced in response to anti-typhus inoculation. Residual O agglutinins for typhoid and paratyphoid bacilli, whether due to previous infection or inoculation, also behave in like manner.The technique of the agglutination test with preserved suspensions of Proteus OX19 is described. Repeated tests with low dilutions of serum, including dilutions 1 : 25 and 1 : 50, are of especial importance in early diagnosis. Some of the possible sources of error are discussed.The various modifications of a slide-agglutination test, now used by German workers for rapid diagnosis in field conditions, are briefly mentioned.The following typhus-like fevers occur in the areas which at present are, or soon may become, a theatre of operations, viz., murine typhus, “fièvre boutonneuse,” tick typhus of India and scrub typhus. The Proteus OX reactions peculiar to each of these varieties of the disease are compared with the OX19 reaction as it is known in louse-borne typhus.