Case Report: Concurrent Sympatric Scrub Typhus and Japanese Spotted Fever in Japan

Scrub typhus and Japanese spotted fever-both rickettsial diseases-are endemic and notifiable in Japan and may cause a fatal outcome without prompt treatment. Here we present the first case of a concurrent sympatric infection of both diseases with grade II evidence. A 67-year-old woman, after a single event of potential exposure to the pathogens, presented with a 12-day history of fever, pharyngeal pain, papulo-erythematous rash, and pronounced fatigue. Her erythematous rash was distributed on her trunk and extremities, palms, and soles and eventually progressed to purpura. Fever persisted until doxycycline was administered on day 12. A significant > 4-fold increase in immunoglobulin G and immunoglobulin M titers against multiple serotypes of Orientia tsutsugamushi and Rickettsia japonica were revealed by indirect immunoperoxidase assays. These clinical and serological data, even in the absence of molecular or isolation evidence, provided grade II evidence that this was a concurrent infection of sympatric scrub typhus and Japanese spotted fever.

Heterogeneity of Orientia tsutsugamushi genotypes in field-collected trombiculid mites from wild-caught small mammals in Thailand

Trombiculid mites are the vectors of scrub typhus, with infected larval mites (chiggers) transmitting the causative agent, Orientia tsutsugamushi, during feeding. Co-existence of multiple O. tsutsugamushi strains within infected mites has previously been reported in naturally infected, laboratory-reared mite lines using molecular methods to characterize the 56-kDa type-specific antigen (TSA) gene. In the current study, more advanced next-generation sequencing technology was used to reveal the heterogeneity of O. tsutsugamushi genotypes in field-collected trombiculid mites from rodents and small mammals in scrub typhus-endemic areas of Thailand. Twenty-eight trombiculid mites collected from 10 small mammals were positive for O. tsutsugamushi, corresponding to a prevalence rate of 0.7% within the mite population. Twenty-four of the infected mites were Leptotrombidium spp., indicating that this genus is the main vector for O. tsutsugamushi transmission in Thailand. In addition, O. tsutsugamushi was detected in the mite genera Ascoschoengastia, Blankaartia, Gahrliepia, and Lorillatum. Of the 10 infested small animal hosts, six had 2-10 infected mites feeding at the time of collection. Deep sequencing was used to characterize mixed infections (two to three O. tsutsugamushi genotypes within an individual mite), and 5 of the 28 infected mites (17.9%) contained mixed infections. Additionally, 56-kDa TSA gene sequence analysis revealed identical bacterial genotypes among co-feeding mites with single or mixed infections. These results suggest that co-feeding transmission may occur during the feeding process, and could explain the occurrence of mixed infections in individual mites, as well as the recovery of multiple infected mites from the same host. This study also revealed highly diverse within-host O. tsutsugamushi genotypes. The occurrence of multiple O. tsutsugamushi genotypes within individual mites has important implications, and could provide a mechanism for pathogen evolution/diversification in the mite vector.

Long-read whole genome sequencing and comparative analysis of six strains of the human pathogen Orientia tsutsugamushi

BACKGROUND

Orientia tsutsugamushi is a clinically important but neglected obligate intracellular bacterial pathogen of the Rickettsiaceae family that causes the potentially life-threatening human disease scrub typhus. In contrast to the genome reduction seen in many obligate intracellular bacteria, early genetic studies of Orientia have revealed one of the most repetitive bacterial genomes sequenced to date. The dramatic expansion of mobile elements has hampered efforts to generate complete genome sequences using short read sequencing methodologies, and consequently there have been few studies of the comparative genomics of this neglected species.

RESULTS

We report new high-quality genomes of O. tsutsugamushi, generated using PacBio single molecule long read sequencing, for six strains: Karp, Kato, Gilliam, TA686, UT76 and UT176. In comparative genomics analyses of these strains together with existing reference genomes from Ikeda and Boryong strains, we identify a relatively small core genome of 657 genes, grouped into core gene islands and separated by repeat regions, and use the core genes to infer the first whole-genome phylogeny of Orientia.

CONCLUSIONS

Complete assemblies of multiple Orientia genomes verify initial suggestions that these are remarkable organisms. They have larger genomes compared with most other Rickettsiaceae, with widespread amplification of repeat elements and massive chromosomal rearrangements between strains. At the gene level, Orientia has a relatively small set of universally conserved genes, similar to other obligate intracellular bacteria, and the relative expansion in genome size can be accounted for by gene duplication and repeat amplification. Our study demonstrates the utility of long read sequencing to investigate complex bacterial genomes and characterise genomic variation.

Acute Encephalitis Syndrome in Eastern Uttar Pradesh, India: Changing Etiological Understanding

Seasonal outbreaks of acute encephalitis syndrome (AES) with high case fatality have been occurring in Gorakhpur division in Eastern Uttar Pradesh, India, for more than three decades. Japanese encephalitis virus (JEV) accounted for <10% of AES cases, while the etiology of the remaining cases remained largely unknown. Investigations conducted during the 2014 and 2015 outbreaks indicated Orientia tsutsugamushi (Haruo Hayashi 1920) (Norio Ogata 1929) Tamura et al. 1995 (Rickettsiales: Rickettsiaceae) as the etiology in about 60% of AES cases. Hospital-based surveillance studies indicated that about one-fifth of the patients with acute febrile illness were due to scrub typhus. Further studies are required to identify the etiology of about a third of AES cases that test negative for scrub typhus, JEV, or dengue.

Orientia tsutsugamushi uses two Ank effectors to modulate NF-κB p65 nuclear transport and inhibit NF-κB transcriptional activation

Orientia tsutsugamushi causes scrub typhus, a potentially fatal infection that threatens over one billion people. Nuclear translocation of the transcription factor, NF-κB, is the central initiating cellular event in the antimicrobial response. Here, we report that NF-κB p65 nuclear accumulation and NF-κB-dependent transcription are inhibited in O. tsutsugamushi infected HeLa cells and/or primary macrophages, even in the presence of TNFα. The bacterium modulates p65 subcellular localization by neither degrading it nor inhibiting IκBα degradation. Rather, it exploits host exportin 1 to mediate p65 nuclear export, as this phenomenon is leptomycin B-sensitive. O. tsutsugamushi antagonizes NF-κB-activated transcription even when exportin 1 is inhibited and NF-κB consequently remains in the nucleus. Two ankyrin repeat-containing effectors (Anks), Ank1 and Ank6, each of which possess a C-terminal F-box and exhibit 58.5% amino acid identity, are linked to the pathogen's ability to modulate NF-κB. When ectopically expressed, both translocate to the nucleus, abrogate NF-κB-activated transcription in an exportin 1-independent manner, and pronouncedly reduce TNFα-induced p65 nuclear levels by exportin 1-dependent means. Flag-tagged Ank 1 and Ank6 co-immunoprecipitate p65 and exportin 1. Both also bind importin β1, a host protein that is essential for the classical nuclear import pathway. Importazole, which blocks importin β1 activity, abrogates Ank1 and Ank6 nuclear translocation. The Ank1 and Ank6 regions that bind importin β1 also mediate their transport into the nucleus. Yet, these regions are distinct from those that bind p65/exportin 1. The Ank1 and Ank6 F-box and the region that lies between it and the ankyrin repeat domain are essential for blocking p65 nuclear accumulation. These data reveal a novel mechanism by which O. tsutsugamushi modulates the activity and nuclear transport of NF-κB p65 and identify the first microbial proteins that co-opt both importin β1 and exportin 1 to antagonize a critical arm of the antimicrobial response.

Scrub Typhus as a Cause of Acute Encephalitis Syndrome, Gorakhpur, Uttar Pradesh, India

Outbreaks of acute encephalitis syndrome (AES) have been occurring in Gorakhpur Division, Uttar Pradesh, India, for several years. In 2016, we conducted a case-control study. Our findings revealed a high proportion of AES cases with Orientia tsutsugamushi IgM and IgG, indicating that scrub typhus is a cause of AES.

An Update on Host-Pathogen Interplay and Modulation of Immune Responses during Orientia tsutsugamushi Infection

The obligate intracellular bacterium Orientia tsutsugamushi is the causative agent of scrub typhus in humans, a serious mite-borne disease present in a widespread area of endemicity, which affects an estimated 1 million people every year. This disease may exhibit a broad range of presentations, ranging from asymptomatic to fatal conditions, with the latter being due to disseminated endothelial infection and organ injury. Unique characteristics of the biology and host-pathogen interactions of O. tsutsugamushi, including the high antigenic diversity among strains and the highly variable, short-lived memory responses developed by the host, underlie difficulties faced in the pursuit of an effective vaccine, which is an imperative need. Other factors that have hindered scientific progress relative to the infectious mechanisms of and the immune response triggered by this bacterium in vertebrate hosts include the limited number of mechanistic studies performed on animal models and the lack of genetic tools currently available for this pathogen. However, recent advances in animal model development are promising to improve our understanding of host-pathogen interactions. Here, we comprehensively discuss the recent advances in and future perspectives on host-pathogen interactions and the modulation of immune responses related to this reemerging disease, highlighting the role of animal models.

Mathematical Modeling for Scrub Typhus and Its Implications for Disease Control

BACKGROUND

The incidence rate of scrub typhus has been increasing in the Republic of Korea. Previous studies have suggested that this trend may have resulted from the effects of climate change on the transmission dynamics among vectors and hosts, but a clear explanation of the process is still lacking. In this study, we applied mathematical models to explore the potential factors that influence the epidemiology of tsutsugamushi disease.

METHODS

We developed mathematical models of ordinary differential equations including human, rodent and mite groups. Two models, including simple and complex models, were developed, and all parameters employed in the models were adopted from previous articles that represent epidemiological situations in the Republic of Korea.

RESULTS

The simulation results showed that the force of infection at the equilibrium state under the simple model was 0.236 (per 100,000 person-months), and that in the complex model was 26.796 (per 100,000 person-months). Sensitivity analyses indicated that the most influential parameters were rodent and mite populations and contact rate between them for the simple model, and trans-ovarian transmission for the complex model. In both models, contact rate between humans and mites is more influential than morality rate of rodent and mite group.

CONCLUSION

The results indicate that the effect of controlling either rodents or mites could be limited, and reducing the contact rate between humans and mites is more practical and effective strategy. However, the current level of control would be insufficient relative to the growing mite population.

Characterization of the rhesus macaque (Macaca mulatta) scrub typhus model: Susceptibility to intradermal challenge with the human pathogen Orientia tsutsugamushi Karp

BACKGROUND

Scrub typhus is an important endemic disease in tropical Asia caused by Orientia tsutsugamushi for which no effective broadly protective vaccine is available. The successful evaluation of vaccine candidates requires well-characterized animal models and a better understanding of the immune response against O. tsutsugamushi. While many animal species have been used to study host immunity and vaccine responses in scrub typhus, only limited data exists in non-human primate (NHP) models.

METHODOLOGY/PRINCIPLE FINDINGS

In this study we evaluated a NHP scrub typhus disease model based on intradermal inoculation of O. tsutsugamushi Karp strain in rhesus macaques (n = 7). After an intradermal inoculation with 106 murine LD50 of O. tsutsugamushi at the anterior thigh (n = 4) or mock inoculum (n = 3), a series of time course investigations involving hematological, biochemical, molecular and immunological assays were performed, until day 28, when tissues were collected for pathology and immunohistochemistry. In all NHPs with O. tsutsugamushi inoculation, but not with mock inoculation, the development of a classic eschar with central necrosis, regional lymphadenopathy, and elevation of body temperature was observed on days 7-21 post inoculation (pi); bacteremia was detected by qPCR on days 6-18 pi; and alteration of liver enzyme function and increase of white blood cells on day 14 pi. Immune assays demonstrated raised serum levels of soluble cell adhesion molecules, anti-O. tsutsugamushi-specific antibody responses (IgM and IgG) and pathogen-specific cell-mediated immune responses in inoculated macaques. The qPCR assays detected O. tsutsugamushi in eschar, spleen, draining and non-draining lymph nodes, and immuno-double staining demonstrated intracellular O. tsutsugamushi in antigen presenting cells of eschars and lymph nodes.

CONCLUSIONS/SIGNIFICANCE

These data show the potential of using rhesus macaques as a scrub typhus model, for evaluation of correlates of protection in both natural and vaccine induced immunity, and support the evaluation of future vaccine candidates against scrub typhus.

Severe Fever with Thrombocytopenia Syndrome in Patients Suspected of Having Scrub Typhus

To determine prevalence of severe fever with thrombocytopenia syndrome in South Korea, we examined serum samples from patients with fever and insect bite history in scrub typhus-endemic areas. During the 2013 scrub typhus season, prevalence of this syndrome among patients suspected of having scrub typhus was high (23.0%), suggesting possible co-infection.

Surveillance for Scrub Typhus, Rickettsial Diseases, and Leptospirosis in US and Multinational Military Training Exercise Cobra Gold Sites in Thailand

We report findings of field surveillance for disease vectors and the prevalence of Orientia tsutsugamushi, the causative agent for scrub typhus, and other Rickettsial species that cause murine typhus and spotted fever group rickettsioses, in chigger mites and small rodents; and Leptospira in rodent kidney, urine, and environmental water samples. The study sites included various Royal Thai Army military installations and other training sites, and surrounding areas where the multinational military training exercise Cobra Gold was conducted in Thailand in 2017 and 2018. The overall prevalence of O. tsutsugamushi and Rickettsia infection in chiggers was 1.3% (20/1,594) and 7.5% (119/1,594), respectively. Serum samples of the captured rodents indicated previous exposure to O. tsutsugamushi infection with a seropositive rate of 12.2%. Leptospira species were isolated from rodent kidneys and water samples collected from catchment areas as well as tap water used for hand washing. Findings from this surveillance are important in determining the potential for scrub typhus, rickettsioses, and leptospirosis risk to military and US government personnel, as well as for informing regional and combatant commanders for prevention, correct diagnosis, prompt treatment, and timely and focused implementation of vector control and personal protective measures.

A review of the global epidemiology of scrub typhus

Scrub typhus is a serious public health problem in the Asia-Pacific area. It threatens one billion people globally, and causes illness in one million people each year. Caused by Orientia tsutsugamushi, scrub typhus can result in severe multiorgan failure with a case fatality rate up to 70% without appropriate treatment. The antigenic heterogeneity of O. tsutsugamushi precludes generic immunity and allows reinfection. As a neglected disease, there is still a large gap in our knowledge of the disease, as evidenced by the sporadic epidemiologic data and other related public health information regarding scrub typhus in its endemic areas. Our objective is to provide a systematic analysis of current epidemiology, prevention and control of scrub typhus in its long-standing endemic areas and recently recognized foci of infection.

Prevalence and Phylogenetic Analysis of Orientia tsutsugamushi in Rodents and Mites from Central India

Orientia tsutsugamushi, the causative agent of scrub typhus in humans, is an obligate intracytosolic bacterium transmitted among animals and to humans by some species of larval trombiculid mites (chiggers) and is hosted mainly by rodents. In this study, we attempted detection of O. tsutsugamushi from blood and tissue samples of rodents trapped from different locations in Central India using PCR targeting the 56 kDa outer membrane protein gene and the 47 kDa high temperature transmembrane protein gene. A total of 59 rodent samples comprising 38 of blood collected from domestic and public surroundings and 21 of tissue from agricultural farm were included in this study. The 56 kDa outer membrane protein gene was detected from 10 of 59 samples by PCR, and the 47 kDa protein gene was detected from 4 of 59 samples by nested-PCR. Mites collected from the rodents were identified as Ornithonyssus bacoti, and one of five pooled samples was found to be positive for O. tsutsugamushi using PCR targeting 56 kDa outer membrane protein gene. Thus, perpetuation of O. tsutsugamushi among rodents and mites was detected constituting a potential public health concern.

Murine models of scrub typhus associated with host control of Orientia tsutsugamushi infection

Background

Scrub typhus, a febrile illness of substantial incidence and mortality, is caused by infection with the obligately intracellular bacterium Orientia tsutsugamushi. It is estimated that there are more than one million cases annually transmitted by the parasitic larval stage of trombiculid mites in the Asia-Pacific region. The antigenic and genetic diversity of the multiple strains of O. tsutsugamushi hinders the advancement of laboratory diagnosis, development of long-lasting vaccine-induced protection, and interpretation of clinical infection. Despite the life-threatening severity of the illness in hundreds of thousands of cases annually, 85–93% of patients survive, often without anti-rickettsial treatment. To more completely understand the disease caused by Orientia infection, animal models which closely correlate with the clinical manifestations, target cells, organ involvement, and histopathologic lesions of human cases of scrub typhus should be employed. Previously, our laboratory has extensively characterized two relevant C57BL/6 mouse models using O. tsutsugamushi Karp strain: a route-specific intradermal model of infection and persistence and a hematogenously disseminated dose-dependent lethal model.

Principal findings

To complement the lethal model, here we illustrate a sublethal model in the same mouse strain using the O. tsutsugamushi Gilliam strain, which resulted in dose-dependent severity of illness, weight loss, and systemic dissemination to endothelial cells of the microcirculation and mononuclear phagocytic cells. Histopathologic lesions included expansion of the pulmonary interstitium by inflammatory cell infiltrates and multifocal hepatic lesions with mononuclear cellular infiltrates, renal interstitial lymphohistiocytic inflammation, mild meningoencephalitis, and characteristic typhus nodules.

Significance

These models parallel characteristics of human cases of scrub typhus, and will be used in concert to understand differences in severity which lead to lethality or host control of the infection and to address the explanation for short duration of heterologous immunity in Orientia infection.

Scrub typhus is an acute febrile illness with considerable mortality, and no available vaccine, caused by the obligately intracellular bacterium, Orientia tsutsugamushi. Despite the life-threatening severity of the illness in approximately one million cases annually, 85–93% of patients survive. The lack of appropriate animal models of scrub typhus has left a void in the fundamental knowledge necessary to develop a vaccine, such as mechanisms which contribute to disease severity and immunity. Here, we report a sublethal inbred murine model for scrub typhus using the intradermal and intravenous routes of inoculation, which are comparable to the natural route of chigger-bite transmission and subsequent hematogenous spread. This model, infection of mice with O. tsutsugamushi Gilliam strain, can be employed in conjunction with the lethal model of O. tsutsugamushi Karp strain to perform in-depth mechanistic studies related to strain cross-protection, lethality, pathogenesis and specific immunological investigations of the host immune response.

Diversification of Orientia tsutsugamushi genotypes by intragenic recombination and their potential expansion in endemic areas

Background

Scrub typhus is a mite-borne febrile disease caused by O. tsutsugamushi infection. Recently, emergence of scrub typhus has attracted considerable attention in several endemic countries in Asia and the western Pacific. In addition, the antigenic diversity of the intracellular pathogen has been a serious obstacle for developing effective diagnostics and vaccine.

Methodology/Principal findings

To understand the evolutionary pathway of genotypic diversification of O. tsutsugamushi and the environmental factors associated with the epidemiological features of scrub typhus, we analyzed sequence data, including spatiotemporal information, of the tsa56 gene encoding a major outer membrane protein responsible for antigenic variation. A total of 324 tsa56 sequences covering more than 85% of its open reading frame were analyzed and classified into 17 genotypes based on phylogenetic relationship. Extensive sequence analysis of tsa56 genes using diverse informatics tools revealed multiple intragenic recombination events, as well as a substantially higher mutation rate than other house-keeping genes. This suggests that genetic diversification occurred via frequent point mutations and subsequent genetic recombination. Interestingly, more diverse bacterial genotypes and dominant vector species prevail in Taiwan compared to other endemic regions. Furthermore, the co-presence of identical and sub-identical clones of tsa56 gene in geographically distant areas implies potential spread of O. tsutsugamushi genotypes.

Conclusions/Significance

Fluctuation and diversification of vector species harboring O. tsutsugamushi in local endemic areas may facilitate genetic recombination among diverse genotypes. Therefore, careful monitoring of dominant vector species, as well as the prevalence of O. tsutsugamushi genotypes may be advisable to enable proper anticipation of epidemiological changes of scrub typhus.

Scrub typhus, caused by Orientia tsutsugamushi infection, is a mite-borne febrile illness endemic in the Asia-Pacific region. Recent emergence and continuous local outbreaks in many of the endemic countries make it a serious public health issue. In addition, the antigenic diversity of the tsa56 gene, encoding a major outer membrane protein, hampers the development of effective diagnostics and vaccine. Here, we extensively analyzed tsa56 sequences and their spatiotemporal information to elucidate the evolutionary pathway of genotypic diversification, as well as the environmental basis associated with the epidemiological changes of scrub typhus. Based on various informatics analyses, we found that genetic diversification of tsa56 might have been attained via frequent point mutations and subsequent genetic recombination among diverse genotypes. Prevalence of numerous bacterial genotypes and dominant vector species in Taiwan also suggest that the subtropical area located at the center of endemicity, may serve as a local mixing ground for genotype diversification. In addition, detection of identical and sub-identical clones of tsa56 genes in geographically distant countries indicates a potential spreading of bacterial genotypes. Continuous monitoring of dominant vector species and the associated O. tsutsugamushi genotypes might be required for developing better diagnostics and an effective vaccine for scrub typhus.

Scrub typhus: A prospective, observational study during an outbreak in Rajasthan, India

BACKGROUND

Scrub typhus, a potentially fatal rickettsial infection, is common in India. It usually presents with acute febrile illness along with multi-organ involvement caused by Orientia tsutsugamushi. As there was an outbreak of scrub typhus in the Hadoti region of Rajasthan and there is a paucity of data from this region, we studied this entity to describe the diverse epidemiological, clinico-radiological, laboratory parameters and outcome profile of patients with scrub typhus in a tertiary care hospital.

METHODS

In this descriptive study, we included all patients with an acute febrile illness diagnosed as scrub typhus by positive IgM antibodies against O. tsutsugamushi, over a period of 4 months (July to October 2014). All relevant data were recorded and analysed.

RESULTS

A total of 66 (24 males/42 females) patients were enrolled. Fever was the most common presenting symptom (100%), and in 67% its duration was for 7-14 days. Other symptoms were breathlessness (66.7%), haemoptysis (63.6%), oliguria (51.5%) and altered mental status (39.4%). The pathognomonic features such as eschar (12%) and lymphadenopathy (18%) were not so common. The commonest radiological observation was consistent with acute respiratory distress syndrome. Complications noted were respiratory (69.7%), renal (51.5%) and hepatic dysfunction (48.5%). The overall mortality rate was 21.2%.

CONCLUSIONS

Scrub typhus has emerged as an important cause of febrile illness in the Hadoti region and can present with varying clinical manifestations with or without eschar. A high index of suspicion, early diagnosis and prompt intervention may help in reducing the mortality.

Prevalence and clinical presentation of Rickettsia, Coxiella, Leptospira, Bartonella and chikungunya virus infections among hospital-based febrile patients from December 2008 to November 2009 in Bangladesh

BACKGROUND

We conducted a study to identify Rickettsia, Coxiella, Leptospira, Bartonella, and Chikungunya virus infections among febrile patients presenting at hospitals in Bangladesh.

METHODS

We collected blood samples from patients at six tertiary hospitals from December 2008 to November 2009 and performed laboratory tests at the United States Centers for Disease Control and Prevention (CDC).

RESULTS

Out of 720 enrolled patients, 263 (37%) were infected with Rickettsia; 132 patients had immunofluorescence antibody titer >64 against spotted fever, 63 patients against scrub typhus fever and 10 patients against typhus fever. Ten patients were identified with Coxiella. We isolated Leptospira from two patients and Bartonella from one patient. Ten patients had antibodies against Chikungunya virus. The proportion of patients who died was higher with rickettsial fever (5%) compared to those without a diagnosis of rickettsial infection (2%). None of the patients were initially diagnosed with rickettsial fever.

CONCLUSIONS

Rickettsial infections are frequent yet under-recognized cause of febrile illness in Bangladesh. Clinical guidelines should be revised so that local clinicians can diagnose rickettsial infections and provide appropriate drug treatment.

Use of eschar swabbing for the molecular diagnosis and genotyping of Orientia tsutsugamushi causing scrub typhus in Quang Nam province, Vietnam

BACKGROUND

Scrub typhus is a rickettsiosis which is caused by Orientia tsutsugamushi and occurs throughout the Asia-Pacific region. Molecular diagnosis of rickettsioses using eschar swabs has recently emerged, and may be very useful for the diagnosis of these diseases in tropical settings.

METHODOLOGY/PRINCIPAL FINDINGS

Quantitative polymerase chain reaction (qPCR) was used to detect O. tsutsugamushi DNA in whole blood and eschar swab specimens of 67 patients who were clinically suspected of scrub typhus in Quang Nam province, Vietnam. Among the 20 patients for whom both eschar and whole blood were obtained, 17 (85%) of the eschar specimens and 5 (25%) of the whole blood specimens tested positive for O. tsutsugamushi. Genetic analysis of the 56-kDa TSA gene sequences demonstrated that the 14 sequences obtained in this study, including 12 eschar swabs and 2 whole blood specimens, were related to 4 groups: Karp, Kawasaki, Gilliam (JG-v and TG-v) and TA716. The majority (9/14; 64.4%) of contemporary O. tsutsugamushi genotypes in Quang Nam province were related to the Karp group.

CONCLUSIONS

These results suggest that polyclonal antigen pools used for serological testing in the future should contain at least Karp, Kawasaki, Gilliam and TA716 antigens for Vietnamese patients, as well as patients who have traveled to Vietnam. qPCR after eschar swabbing should be considered for molecular diagnosis of scrub typhus in endemic patients as well as in travelers, since it is easy to perform and appears very useful for the rapid detection of Orientia tsutsugamushi in the early phase of infection.

Scrub Typhus Leading to Acute Encephalitis Syndrome, Assam, India

To determine the contribution of Orientia tsutsugamushi, the agent of scrub typhus, as a cause of acute encephalitis syndrome (AES) in Assam, India, we conducted a retrospective study of hospital patients with symptoms of AES during 2013–2015. Our findings suggest that O. tsutsugamushi infection leads to AES and the resulting illness and death.

Q Fever, Scrub Typhus, and Rickettsial Diseases in Children, Kenya, 2011-2012

To increase knowledge of undifferentiated fevers in Kenya, we tested paired serum samples from febrile children in western Kenya for antibodies against pathogens increasingly recognized to cause febrile illness in Africa. Of patients assessed, 8.9%, 22.4%, 1.1%, and 3.6% had enhanced seroreactivity to Coxiella burnetii, spotted fever group rickettsiae, typhus group rickettsiae, and scrub typhus group orientiae, respectively.

Endemic Scrub Typhus in South America

Scrub typhus is a life-threatening zoonosis caused by Orientia tsutsugamushi organisms that are transmitted by the larvae of trombiculid mites. Endemic scrub typhus was originally thought to be confined to the so called "tsutsugamushi triangle" within the Asia-Pacific region. In 2006, however, two individual cases were detected in the Middle East and South America, which suggested that the pathogen was present farther afield. Here, we report three autochthonous cases of scrub typhus caused by O. tsutsugamushi acquired on Chiloé Island in southern Chile, which suggests the existence of an endemic focus in South America. (Funded by the Chilean Comisión Nacional de Investigación Científica y Tecnológica and the Wellcome Trust.).

Clinical Evaluation of Rapid Diagnostic Test Kit for Scrub Typhus with Improved Performance

Diagnosis of scrub typhus is challenging due to its more than twenty serotypes and the similar clinical symptoms with other acute febrile illnesses including leptospirosis, murine typhus and hemorrhagic fever with renal syndrome. Accuracy and rapidity of a diagnostic test to Orientia tsutsugamushi is an important step to diagnose this disease. To discriminate scrub typhus from other diseases, the improved ImmuneMed Scrub Typhus Rapid Diagnostic Test (RDT) was evaluated in Korea and Sri Lanka. The sensitivity at the base of each IgM and IgG indirect immunofluorescent assay (IFA) in Korean patients was 98.6% and 97.1%, and the specificity was 98.2% and 97.7% respectively. The sensitivity and specificity for retrospective diagnosis at the base of IFA in Sri Lanka was 92.1% and 96.1%. ImmuneMed RDT was not reactive to any serum from seventeen diseases including hemorrhagic fever with renal syndrome (n = 48), leptospirosis (n = 23), and murine typhus (n = 48). ImmuneMed RDT shows superior sensitivity (98.6% and 97.1%) compared with SD Bioline RDT (84.4% at IgM and 83.3% at IgG) in Korea. The retrospective diagnosis of ImmuneMed RDT exhibits 94.0% identity with enzyme-linked Immunosorbent assay (ELISA) using South India patient serum samples. These results suggest that this RDT can replace other diagnostic tests and is applicable for global diagnosis of scrub typhus. This rapid and accurate diagnosis will be beneficial for diagnosing and managing scrub typhus.