Coagulation and inflammation in scrub typhus and murine typhus--a prospective comparative study from Laos

Association of scrub typhus with the risk of venous thromboembolism and long-term mortality: a population-based cohort study

BACKGROUND

The existing literature lacks studies examining the epidemiological link between scrub typhus and deep vein thrombosis (DVT) or pulmonary embolism (PE), and the long-term outcomes. The objective of this study is to explore the potential association between scrub typhus and the subsequent risk of venous thromboembolism, and long-term mortality.

METHOD

This nationwide cohort study identified 10,121 patients who were newly diagnosed with scrub typhus. Patients with a prior DVT or PE diagnosis before the scrub typhus infection were excluded. A comparison cohort of 101,210 patients was established from the general population using a propensity score matching technique. The cumulative survival HRs for the two cohorts were calculated by the Cox proportional hazards model.

RESULT

After adjusting for sex, age, and comorbidities, the scrub typhus group had an adjusted HR (95% CI) of 1.02 (0.80-1.30) for DVT, 1.11 (0.63-1.93) for PE, and 1.16 (1.08-1.25) for mortality compared to the control group. The post hoc subgroup analysis revealed that individuals younger than 55 years with a prior scrub typhus infection had a significantly higher risk of DVT (HR: 1.59; 95% CI: 1.12-2.25) and long-term mortality (HR: 1.75; 95% CI, 1.54-1.99).

CONCLUSION

The scrub typhus patients showed a 16% higher risk of long-term mortality. For those in scrub typhus cohort below 55 years of age, the risk of developing DVT was 1.59 times higher, and the risk of mortality was 1.75 times higher. Age acted as an effect modifier influencing the relationship between scrub typhus and risk of new-onset DVT and death.

A time-course comparative clinical and immune response evaluation study between the human pathogenic Orientia tsutsugamushi strains: Karp and Gilliam in a rhesus macaque (Macaca mulatta) model

BACKGROUND

Scrub typhus is a vector-borne febrile illness caused by Orientia tsutsugamushi transmitted by the bite of Trombiculid mites. O. tsutsugamushi has a high genetic diversity and is increasingly recognized to have a wider global distribution than previously assumed.

METHODOLOGY/PRINCIPLE FINDINGS

We evaluated the clinical outcomes and host immune responses of the two most relevant human pathogenic strains of O. tsutsugamushi; Karp (n = 4) and Gilliam (n = 4) in a time-course study over 80 days post infection (dpi) in a standardized scrub typhus non-human primate rhesus macaque model. We observed distinct features in clinical progression and immune response between the two strains; Gilliam-infected macaques developed more pronounced systemic infection characterized by an earlier onset of bacteremia, lymph node enlargement, eschar lesions and higher inflammatory markers during the acute phase of infection, when compared to the Karp strain. C-reactive protein (CRP) plasma levels, interferon gamma (IFN-γ, interleukin-1 receptor antagonist (IL-1ra), IL-15 serum concentrations, CRP/IL10- and IFN-γ/IL-10 ratios correlated positively with bacterial load in blood, implying activation of the innate immune response and preferential development of a T helper-type 1 immune response. The O. tsutsugamushi-specific immune memory responses in cells isolated from skin and lymph nodes at 80 dpi were more markedly elevated in the Gilliam-infected macaques than in the Karp-infected group. The comparative cytokine response dynamics of both strains revealed significant up-regulation of IFN-γ, tumor necrosis factor (TNF), IL-15, IL-6, IL-18, regulatory IL-1ra, IL-10, IL-8 and granulocyte-colony-stimulating factor (G-CSF). These data suggest that the clinical outcomes and host immune responses to scrub typhus could be associated with counter balancing effects of pro- and anti-inflammatory cytokine-mediated responses. Currently, no data on characterized time-course comparisons of O. tsutsugamushi strains regarding measures of disease severity and immune response is available. Our study provides evidence for the strain-specificity of host responses in scrub typhus, which supports our understanding of processes at the initial inoculation site (eschar), systemic disease progression, protective and/or pathogenic host immune mechanisms and cellular immune memory function.

CONCLUSIONS/SIGNIFICANCE

This study characterised an improved intradermal rhesus macaque challenge model for scrub typhus, whereby the Gilliam strain infection associated with higher disease severity in the rhesus macaque model than the previous Karp strain infection. Difficulties associated with inoculum quantitation for obligate-intracellular bacteria were overcome by using functional inoculum titrations in outbred mice. The Gilliam-based rhesus macaque model provides improved endpoint measurements and contributes towards the identification of correlates of protection for future vaccine development.

Scrub Typhus and COVID-19 Coinfection Unmasking Antiphospholipid Antibody Syndrome

Scrub typhus is an acute febrile disease caused by Orientia tsutsugamushi with a clinical course varying from mild to fatal. Vascular thrombosis is rare in scrub typhus. There is an increased risk of thrombotic events in Coronavirus disease 19 (COVID-19). We report a young diabetic female who presented with pulmonary embolism, followed by deep venous thrombosis (DVT) and was found to have coinfection with scrub typhus and COVID-19 with underlying antiphospholipid antibody syndrome.

Systematic review of the scrub typhus treatment landscape: Assessing the feasibility of an individual participant-level data (IPD) platform

Background

Scrub typhus is an acute febrile illness caused by intracellular bacteria from the genus Orientia. It is estimated that one billion people are at risk, with one million cases annually mainly affecting rural areas in Asia-Oceania. Relative to its burden, scrub typhus is understudied, and treatment recommendations vary with poor evidence base. These knowledge gaps could be addressed by establishing an individual participant-level data (IPD) platform, which would enable pooled, more detailed and statistically powered analyses to be conducted. This study aims to assess the characteristics of scrub typhus treatment studies and explore the feasibility and potential value of developing a scrub typhus IPD platform to address unanswered research questions.

Methodology/principal findings

We conducted a systematic literature review looking for prospective scrub typhus clinical treatment studies published from 1998 to 2020. Six electronic databases (Ovid Embase, Ovid Medline, Ovid Global Health, Cochrane Library, Scopus, Global Index Medicus), ClinicalTrials.gov, and WHO ICTRP were searched. We extracted data on study design, treatment tested, patient characteristics, diagnostic methods, geographical location, outcome measures, and statistical methodology.

Among 3,100 articles screened, 127 were included in the analysis. 12,079 participants from 12 countries were enrolled in the identified studies. ELISA, PCR, and eschar presence were the most commonly used diagnostic methods. Doxycycline, azithromycin, and chloramphenicol were the most commonly administered antibiotics. Mortality, complications, adverse events, and clinical response were assessed in most studies. There was substantial heterogeneity in the diagnostic methods used, treatment administered (including dosing and duration), and outcome assessed across studies. There were few interventional studies and limited data collected on specific groups such as children and pregnant women.

Conclusions/significance

There were a limited number of interventional trials, highlighting that scrub typhus remains a neglected disease. The heterogeneous nature of the available data reflects the absence of consensus in treatment and research methodologies and poses a significant barrier to aggregating information across available published data without access to the underlying IPD. There is likely to be a substantial amount of data available to address knowledge gaps. Therefore, there is value for an IPD platform that will facilitate pooling and harmonisation of currently scattered data and enable in-depth investigation of priority research questions that can, ultimately, inform clinical practice and improve health outcomes for scrub typhus patients.

Scrub typhus is a febrile illness most commonly found in rural tropical areas. It is caused by a Gram-negative bacteria belonging to the family Rickettsiaceae and transmitted by mites when they feed on vertebrates. There is an estimate of one million cases annually, with an estimated one billion people at risk, mostly in Asia-Oceania. But relative to the scale of the problem, scrub typhus is largely understudied. Evidence-based treatment recommendations by policymakers vary or are non-existent. We searched databases and registries for prospective scrub typhus clinical treatment studies published from 1998 to 2020 and reviewed them. Data from clinical trials and particularly for specific groups, such as pregnant women and children, were minimal. The methods used to measure treatment efficacy were heterogeneous, making it difficult to directly compare or conduct a meta-analysis based on aggregated data. One way to improve the current level of evidence would be by pooling and analysing individual participant-level data (IPD), i.e. the raw data from individual participants in completed studies. This review demonstrated that there is scope for developing a database for individual participant data to enable more detailed analyses. IPD meta-analyses could be a way to address knowledge gaps such as optimum dosing for children and pregnant women.

Viral-induced inflammatory coagulation disorders: Preparing for another epidemic

A number of viral infectious diseases have emerged or reemerged from wildlife vectors that have generated serious threats to global health. Increased international traveling and commerce increase the risk of transmission of viral or other infectious diseases. In addition, recent climate changes accelerate the potential spread of domestic disease. The Coronavirus disease 2019 (COVID-19) pandemic is an important example of the worldwide spread, and the current epidemic will unlikely be the last. Viral hemorrhagic fevers, such as Dengue and Lassa fevers, may also have the potential to spread worldwide with a significant impact on public health with unpredictable timing. Based on the important lessons learned from COVID-19, it would be prudent to prepare for future pandemics of life-threatening viral diseases. Among the various threats, this review focuses on the coagulopathy of acute viral infections since hypercoagulability has been a major challenge in COVID-19, but represents a different presentation compared to viral hemorrhagic fever. However, both thrombosis and hemorrhage are understood as the result of thromboinflammation due to viral infections, and the role of anticoagulation is important to consider.

Endothelial Activation in Orientia tsutsugamushi Infection Is Mediated by Cytokine Secretion From Infected Monocytes

Scrub typhus, caused by Orientia tsutsugamushi, is a common systemic infection in Asia. Delay in diagnosis and treatment can lead to vasculitis in the visceral organs and other complications. The mechanisms that drive endothelial activation and the inflammatory response in O. tsutsugamushi infection remain unknown. In addition, the interaction between monocytes and endothelial cells is still unclear. Here we demonstrate that O. tsutsugamushi-infected human dermal microvascular endothelial cells produced moderate levels of chemokines and low levels of IL-6 and IFN-β, but not TNF or IL-1β. Recombinant TNF and cytokine-rich supernatants from infected monocytes markedly enhanced chemokine production in infected endothelial cells. We also show that TNF and monocyte supernatants, but not O. tsutsugamushi infection of endothelial cells per se, upregulated the endothelial cell surface expression of ICAM-1, E-selectin, and tissue factor. This finding was consistent with the inability of O. tsutsugamushi to induce cytokine secretion from endothelial cells. The upregulation of surface molecules after stimulation with monocyte supernatants was significantly reduced by neutralizing anti-TNF antibodies. These results suggest that endothelial cell activation and response are mainly mediated by inflammatory cytokines secreted from monocytes.

Murine Typhus Infection in Pregnancy: Case Series and Literature Review

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.

Complex Cytokine Responses in Imported Scrub Typhus Cases, Germany, 2010-2018

Scrub typhus is a life-threatening zoonotic disease, which is caused by Orientia tsutsugamushi, an obligatory intracellular Gram-negative bacterium. It is transmitted by Leptotrombidium mites in endemic regions of Southeast Asia. So far, data on imported scrub typhus cases to non-endemic areas and immunological descriptions are rare. Eleven scrub typhus cases that had been diagnosed by the German National Reference Center for Tropical Pathogens between 2010 and 2018 were retrospectively reviewed for clinical symptoms, laboratory changes, and travel destinations. Patient sera were included if follow-up samples showed simultaneous seroconversion for IgM and IgG antibody responses by immunofluorescence assays or concurrence with the first serum sample. The median of seroconversion was week 2 after symptom onset. Cytokine levels were measured over time, demonstrating simultaneously upregulated major Th1, Th2, and Th17 cytokines in the acute phase of infection followed by normalization during convalescence. This study underlines the complex mixed cytokine response elicited by scrub typhus and highlights clinical and diagnostic aspects of imported infections with O. tsutsugamushi.

Temporal analysis of mRNA expression profiles in Orientia infected C3HeB/FeJ mouse

Background

Scrub typhus causes up to 35% mortality if left untreated. One billion people living in the endemic regions are at risk. In spite of its heavy disease burden in some of the most populated areas in the world, there is no vaccine available. Although the disease can be effectively treated by proper antibiotics, timely and accurate diagnosis remains a challenge. Orientia tsutsugamushi infects a variety of mammalian cells in vitro and replicates in the cytoplasm of the infected cells. Microarray analysis has been used extensively to study host-pathogen interactions in in vitro models to understand pathogenesis. However there is a lack of in vivo studies.

Results

In this study, C3HeB/FeJ (C3H) mice were infected by O. tsutsugamushi via the intraperitoneal route and monitored gene expression at 10 different time points post infection. We observed two distinct types of expression profiles in the genes that we analyzed. There are two valleys (4–18 h and 2–4 days) with low number of differentially expressed genes (DEG) with three peaks with high number of DEG at 2 h, 1-day and 7-day post infection. Further analysis revealed that pathways like complement and coagulation cascade, and blood clotting cascade pathways showed significant global changes throughout entire time course. Real time quantitative Polymerase Chain Reaction (RT-qPCR) confirmed the change of expression for genes involved in complement and coagulation cascade. These results suggested dynamic regulation of the complement and coagulation cascades throughout most of the time post infection while some other specific pathways, such as fatty acid metabolism and tryptophan metabolism, are turned on or off at certain times post infection.

Conclusions

The findings highlight the complex interconnection among all different biological pathways. It is conceivable that specific pathways such as cell growth control and cell development in the host are affected by Orientia in the initial phase of infection for Orientia to grow intracellularly. Once Orientia is replicating successfully inside the host as infection progresses, the infection could activate pathways involved in cellular immune responses to defend for host cell survival and try to eliminate the pathogen.

Pulmonary thromboembolism – A rare complication in a scrub typhus infection

We describe a rare haematological complication of pulmonary thromboembolism in a scrub typhus infection. There are very few case reports on scrub typhus infection causing deep venous thrombosis. Vasculitis and perivasculitis with endothelial dysfunction could be considered as the main pathologic mechanism causing this complication.

Evaluation of Th1 and Th2 immune response in clinical and sub-clinical scrub typhus infection

Scrub typhus (ST), caused by a gram negative intracellular bacteria- Orientia tsutsugamushi, is one among the leading causes of febrile illness across Southeast Asia, including India. Clinical presentation can vary from asymptomatic to severely fatal. Th1-cell mediated immunity has been suggested to play an important role against ST infection in animal models. However, human data on protective immunity are limited. The present study was undertaken to identify host immune correlates that could confer protection in individuals that remain clinically asymptomatic/sub-clinical. Serum cytokine profiling and mRNA expression levels of Th1 (TNF-α, IFN-γ, IL-2) and Th2 (IL-10, IL-6, IL-4) cytokines was studied amongst the clinical and sub-clinical infections. It was observed that a Th1/Th2 pattern is not involved in human ST infection irrespective of being a symptomatic or asymptomatic presentation. However, significant difference was observed in IL-10 serum and gene expression levels. This study suggests a possible role of IL-10 in disease phenotypic presentation. Over-production of IL-10 was found to be a significant factor contributing to the severity of the disease whereas a protective immune mechanism might exist with a low level of IL-10 in ST infection.

Pulmonary Artery Thrombosis Associated with Scrub Typhus

Scrub typhus is an acute febrile disease caused by Orientia tsutsugamushi, and the clinical course varies from mild and self-limiting to fatal. We describe a rare case of a pulmonary artery thrombosis associated with scrub typhus. Vasculitis via endothelial dysfunction caused by scrub typhus could be considered as the main mechanism.

Dysregulated Th1 Immune and Vascular Responses in Scrub Typhus Pathogenesis

Scrub typhus is an emerging, insect-transmitted disease caused by Orientia tsutsugamushi, a Gram- and LPS-negative bacterium that replicates freely within professional phagocytes and endothelial cells. Scrub typhus is prevalent with high mortality rates, but information regarding its molecular pathogenesis, microbial virulence determinants, and key immune responses is limited. Improved animal models have recently been developed that respectively resemble the pathological features of self-limiting or severe scrub typhus in humans. Strong activation of Th1 and CD8, but not Th2 and regulatory T, immune responses, accompanied by altered angiopoietin/Tie2-related regulation, are hallmarks of lethal infection in murine models. This review, based primarily on recent advances from clinical and experimental studies, highlights tissue- and endothelial cell-specific biomarkers that are indicative of immune dysregulation. The potential roles of neutrophils and damage-associated molecular pattern molecules at late stages of disease are discussed in the context of vascular leakage, pulmonary and renal injury, and scrub typhus pathogenesis.

Under-diagnosis of rickettsial disease in clinical practice: A systematic review

BACKGROUND

Rickettsial diseases present as acute febrile illnesses, sometimes with inoculation eschars.

METHODS

We performed a systematic review of studies published between 1997 and 2017 to assess the underestimation of non-eschar rickettsial disease (NERD) relative to eschar rickettsial disease (ERD), as a cause of acute fever in patients with rickettsial diseases that commonly present with eschar(s): scrub typhus (ST), Mediterranean spotted fever (MSF), and African tick-bite fever. We compared ERD/NERD ratios according to study design: 'complete approach' studies, with testing performed in all patients with 'unspecified febrile illness'; versus 'clinical judgement' studies, with testing performed if patients presented with specific symptoms.

RESULTS

In 'complete approach' studies, ERD/NERD ratios were significantly lower, suggesting a considerable under-diagnosis of NERD in 'clinical judgement' studies. Based on these results, we estimate that the diagnosis of rickettsial disease was missed in 66.5% of patients with ST, and in 57.9% of patients with MSF.

CONCLUSIONS

Study design influences the reported eschar rates in ST and MSF significantly. NERD is likely to be a vastly underdiagnosed entity, and clinicians should consider and test for the disease more often.

PROSPERO REGISTRATION NUMBER

CRD 42016053348.

Causes of acute undifferentiated fever and the utility of biomarkers in Chiangrai, northern Thailand

BACKGROUND

Tropical infectious diseases like dengue, scrub typhus, murine typhus, leptospirosis, and enteric fever continue to contribute substantially to the febrile disease burden throughout Southeast Asia while malaria is declining. Recently, there has been increasing focus on biomarkers (i.e. C-reactive protein (CRP) and procalcitonin) in delineating bacterial from viral infections.

METHODOLOGY/PRINCIPAL FINDINGS

A prospective observational study was performed to investigate the causes of acute undifferentiated fever (AUF) in adults admitted to Chiangrai Prachanukroh hospital, northern Thailand, which included an evaluation of CRP and procalcitonin as diagnostic tools. In total, 200 patients with AUF were recruited. Scrub typhus was the leading bacterial cause of AUF (45/200, 22.5%) followed by leptospirosis (15/200, 7.5%) and murine typhus (7/200, 3.5%), while dengue was the leading viral cause (23/200, 11.5%). Bloodstream infections contributed to 7/200 (3.5%) of the study cohort. There were 9 deaths during this study (4.5%): 3 cases of scrub typhus, 2 with septicaemia (Talaromyces marneffei and Haemophilus influenzae), and 4 of unknown aetiologies. Rickettsioses, leptospirosis and culture-attributed bacterial infections, received a combination of 3rd generation cephalosporin plus a rickettsia-active drug in 53%, 73% and 67% of cases, respectively. Low CRP and white blood count were significant predictors of a viral infection (mainly dengue) while the presence of an eschar and elevated aspartate aminotransferase and alkaline phosphatase were important predictors of scrub typhus.

INTERPRETATION

Scrub typhus and dengue are the leading causes of AUF in Chiangrai, Thailand. Eschar, white blood count and CRP were beneficial in differentiating between bacterial and viral infections in this study. CRP outperformed procalcitonin although cut-offs for positivity require further assessment. The study provides evidence that accurate, pathogen-specific rapid diagnostic tests coupled with biomarker point-of-care tests such as CRP can inform the correct use of antibiotics and improve antimicrobial stewardship in this setting.

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.

Clinical proteomic analysis of scrub typhus infection

Background

Scrub typhus is an acute and febrile infectious disease caused by the Gram-negative α-proteobacterium Orientia tsutsugamushi from the family Rickettsiaceae that is widely distributed in Northern, Southern and Eastern Asia. In the present study, we analysed the serum proteome of scrub typhus patients to investigate specific clinical protein patterns in an attempt to explain pathophysiology and discover potential biomarkers of infection.

Methods

Serum samples were collected from three patients (before and after treatment with antibiotics) and three healthy subjects. One-dimensional sodium dodecyl sulphate–polyacrylamide gel electrophoresis followed by liquid chromatography-tandem mass spectrometry was performed to identify differentially abundant proteins using quantitative proteomic approaches. Bioinformatic analysis was then performed using Ingenuity Pathway Analysis.

Results

Proteomic analysis identified 236 serum proteins, of which 32 were differentially expressed in normal subjects, naive scrub typhus patients and patients treated with antibiotics. Comparative bioinformatic analysis of the identified proteins revealed up-regulation of proteins involved in immune responses, especially complement system, following infection with O. tsutsugamushi, and normal expression was largely rescued by antibiotic treatment.

Conclusions

This is the first proteomic study of clinical serum samples from scrub typhus patients. Proteomic analysis identified changes in protein expression upon infection with O. tsutsugamushi and following antibiotic treatment. Our results provide valuable information for further investigation of scrub typhus therapy and diagnosis.

Electronic supplementary material

The online version of this article (10.1186/s12014-018-9181-5) contains supplementary material, which is available to authorized users.

Activation of the coagulation cascade in patients with scrub typhus

This retrospective study aimed to evaluate the levels of coagulation factors and presence of disseminated intravascular coagulation (DIC) in patients with scrub typhus. We included patients confirmed to have scrub typhus at the Chosun University Hospital between September 2004 and December 2009. The DIC scores were evaluated in 365 patients and 36 healthy controls. The median concentrations of fibrinogen, d-dimer, and fibrin/fibrinogen degradation products (FDP) were compared between patients and healthy controls (p<0.001 for all tests). Patients with scrub typhus had longer prothrombin time and lower platelet counts than the controls. Major bleeding was observed in 18/365 patients with scrub typhus. Fifty-one (14.0%) patients presented with severe complications of scrub typhus. Overt DIC and thrombocytopenia (<100,000 platelets/mm³) were observed more frequently in patients with bleeding and severe illness. Furthermore, median platelet counts were low in both groups. Approximately 2.7% (n=10) and 16.4% (n=60) patients with scrub typhus had overt DIC, as defined by the International Society on Thrombosis and Hemostasis DIC score (DIC1) and the DIC-scoring template with a fibrinogen/C-reactive protein-ratio (DIC2), respectively. Three (16.7%) and 10 (55.6%) patients with bleeding had overt DIC, as defined by the DIC1 and DIC2, respectively. Seven (13.7%) and 26 (51%) patients with severe illness had overt DIC, as defined by DIC1 and DIC2, respectively. In conclusion, activation of the coagulation system is an important feature of scrub typhus and is correlated with severe disease, including bleeding. This is the first study to report a relationship between DIC and scrub typhus.

Clinical and laboratory characteristics, epidemiology, and outcomes of murine typhus: A systematic review

Murine or endemic typhus, a febrile disease caused by Rickettsia typhi, is often misdiagnosed due to its non-specific presentation. We sought to evaluate all available evidence in the literature regarding the clinical and laboratory manifestations, epidemiological characteristics, and outcomes of murine typhus. Pubmed was searched for all articles providing available data. In an effort to incorporate contemporary data, only studies from 1980 were included. Thirty-three case series including 2074 patients were included in final analysis. Available evidence suggests that the classic triad of fever, headache and rash is encountered in only one-third of patients. Other frequent symptoms were chills, malaise, myalgia, and anorexia. A tetrad of reported laboratory abnormalities consisting of elevated liver enzymes, lactate dehydrogenase, erythrocyte sedimentation rate and hypoalbuminemia was detected. Complications were observed in one-fourth of patients, reported mortality was extremely low, but untreated patients had notably longer duration of fever. Among epidemiological characteristics, a seasonal distribution with most cases reported during warmer months, was the most prominent finding. Murine typhus in children exhibits several different characteristics, with abdominal pain, diarrhea, and sore throat reported more commonly, higher frequency of anemia, lower frequency of hypoalbuminemia, hematuria and proteinuria and a much lower rate of complications. This systematic review of published evidence provides a thorough description of the clinical and laboratory features of murine typhus and highlights important differences in children.

Increased Nucleosomes and Neutrophil Activation Link to Disease Progression in Patients with Scrub Typhus but Not Murine Typhus in Laos

Cell-mediated immunity is essential in protection against rickettsial illnesses, but the role of neutrophils in these intracellular vasculotropic infections remains unclear. This study analyzed the plasma levels of nucleosomes, FSAP-activation (nucleosome-releasing factor), and neutrophil activation, as evidenced by neutrophil-elastase (ELA) complexes, in sympatric Lao patients with scrub typhus and murine typhus. In acute scrub typhus elevated nucleosome levels correlated with lower GCS scores, raised respiratory rate, jaundice and impaired liver function, whereas neutrophil activation correlated with fibrinolysis and high IL-8 plasma levels, a recently identified predictor of severe disease and mortality. Nucleosome and ELA complex levels were associated with a 4.8-fold and 4-fold increased risk of developing severe scrub typhus, beyond cut off values of 1,040 U/ml for nucleosomes and 275 U/ml for ELA complexes respectively. In murine typhus, nucleosome levels associated with pro-inflammatory cytokines and the duration of illness, while ELA complexes correlated strongly with inflammation markers, jaundice and increased respiratory rates. This study found strong correlations between circulating nucleosomes and neutrophil activation in patients with scrub typhus, but not murine typhus, providing indirect evidence that nucleosomes could originate from neutrophil extracellular trap (NET) degradation. High circulating plasma nucleosomes and ELA complexes represent independent risk factors for developing severe complications in scrub typhus. As nucleosomes and histones exposed on NETs are highly cytotoxic to endothelial cells and are strongly pro-coagulant, neutrophil-derived nucleosomes could contribute to vascular damage, the pro-coagulant state and exacerbation of disease in scrub typhus, thus indicating a detrimental role of neutrophil activation. The data suggest that increased neutrophil activation relates to disease progression and severe complications, and increased plasma levels of nucleosomes and ELA complexes represent independent risk factors for developing severe scrub typhus.

Tropical rickettsial illnesses, especially scrub typhus and murine typhus, are increasingly recognized as a leading cause of treatable undifferentiated febrile illness in Asia, but remain severely neglected and under appreciated diseases in many areas. In this study we investigated the relationship of markers of neutrophil activation and cell death with disease severity in patients with acute scrub typhus and murine typhus in Laos. These easily measurable circulating markers were associated with a 4 to 5-fold increased risk of developing severe clinical disease manifestations in scrub typhus and represent independent predictors of severe disease, and possibly death. We also found strong correlations between circulating markers of cell death and neutrophil activation in patients with scrub typhus, but not murine typhus, providing indirect evidence that neutrophil extracellular traps could contribute to the vascular damage and pro-coagulant state leading to exacerbation of disease in scrub typhus, thus indicating a detrimental role of neutrophil activation. The data suggest that increased neutrophil activation relates to disease progression and severe complications, and increased plasma levels of nucleosomes and ELA complexes represent independent risk factors for developing severe scrub typhus.

A nonhuman primate scrub typhus model: protective immune responses induced by pKarp47 DNA vaccination in cynomolgus macaques

We developed an intradermal (ID) challenge cynomolgus macaque (Macaca fascicularis) model of scrub typhus, the leading cause of treatable undifferentiated febrile illness in tropical Asia, caused by the obligate intracellular bacterium, Orientia tsutsugamushi. A well-characterized animal model is required for the development of clinically relevant diagnostic assays and evaluation of therapeutic agents and candidate vaccines. We investigated scrub typhus disease pathophysiology and evaluated two O. tsutsugamushi 47-kDa, Ag-based candidate vaccines, a DNA plasmid vaccine (pKarp47), and a virus-vectored vaccine (Kp47/47-Venezuelan equine encephalitis virus replicon particle) for safety, immunogenicity, and efficacy against homologous ID challenge with O. tsutsugamushi Karp. Control cynomolgus macaques developed fever, classic eschars, lymphadenopathy, bacteremia, altered liver function, increased WBC counts, pathogen-specific Ab (IgM and IgG), and cell-mediated immune responses. Vaccinated macaques receiving the DNA plasmid pKarp47 vaccine had significantly increased O. tsutsugamushi-specific, IFN-γ-producing PBMCs (p = 0.04), reduced eschar frequency and bacteremia duration (p ≤ 0.01), delayed bacteremia onset (p < 0.05), reduced circulating bacterial biomass (p = 0.01), and greater reduction of liver transaminase levels (p < 0.03) than controls. This study demonstrates a vaccine-induced immune response capable of conferring sterile immunity against high-dose homologous ID challenge of O. tsutsugamushi in a nonhuman primate model, and it provides insight into cell-mediated immune control of O. tsutsugamushi and dissemination dynamics, highlights the importance of bacteremia indices for evaluation of both natural and vaccine-induced immune responses, and importantly, to our knowledge, has determined the first phenotypic correlates of immune protection in scrub typhus. We conclude that this model is suitable for detailed investigations into vaccine-induced immune responses and correlates of immunity for scrub typhus.

Pregnancy outcome in relation to treatment of murine typhus and scrub typhus infection: a fever cohort and a case series analysis

Background

There is a paucity of published reports on pregnancy outcome following scrub and murine typhus despite these infections being leading causes of undifferentiated fever in Asia. This study aimed to relate pregnancy outcome with treatment of typhus.

Methodology/Principal Findings

Data were analyzed from: i) pregnant women with a diagnosis of scrub and/or murine typhus from a fever cohort studies; ii) case series of published studies in PubMed using the search terms “scrub typhus” (ST), “murine typhus” (MT), “Orientia tsutsugamushi”, “Rickettsia tsutsugamushi”, “Rickettsia typhi”, “rickettsiae”, “typhus”, or “rickettsiosis”; and “pregnancy”, until February 2014 and iii) an unpublished case series. Fever clearance time (FCT) and pregnancy outcome (miscarriage and delivery) were compared to treatment. Poor neonatal outcome was a composite measure for pregnancies sustained to 28 weeks or more of gestation ending in stillbirth, preterm birth, or delivery of a growth restricted or low birth weight newborn.

Results

There were 26 women in the fever cohort. MT and ST were clinically indistinguishable apart from two ST patients with eschars. FCTs (median [range] hours) were 25 [16–42] for azithromycin (n = 5), 34 [20–53] for antimalarials (n = 5) and 92 [6–260] for other antibiotics/supportive therapy (n = 16). There were 36.4% (8/22) with a poor neonatal outcome.

In 18 years, 97 pregnancies were collated, 82 with known outcomes, including two maternal deaths. Proportions of miscarriage 17.3% (14/81) and poor neonatal outcomes 41.8% (28/67) were high, increasing with longer FCTs (p = 0.050, linear trend). Use of azithromycin was not significantly associated with improved neonatal outcomes (p = 0.610)

Conclusion

The published ST and MT world literature amounts to less than 100 pregnancies due to under recognition and under diagnosis. Evidence supporting the most commonly used treatment, azithromycin, is weak. Collaborative, prospective clinical trials in pregnant women are urgently required to reduce the burden of adverse maternal and newborn outcomes and to determine the safety and efficacy of antimicrobial treatment.

Typhus is an under-recognised and under-studied public health problem in Asia. In rural areas of Southeast Asia murine and scrub typhus are probably the most common treatable cause of fever. The estimated number of scrub typhus cases in Southeast Asia, more than 1 million yearly, results in approximately 50–80,000 deaths per year. Treatment delays due to lack of appropriate diagnostics and lack of awareness lead to a substantial health and economic impact in the one of the world's most densely populated regions. Only 97 cases in pregnancy are available from the published world literature over the past 18 years. Only 82 of these had known outcomes, including two maternal deaths. The proportion of poor neonatal outcome including stillbirth, prematurity and low birth weight was high occurring in more than 40% of pregnancies, and higher when the fever clearance time was longer. While poor neonatal outcomes were observed with all antibiotics prescribed, azithromycin appeared to be associated with shorter fever clearance times but this was not statistically significant. Evidence to support the use of azithromycin is weak. The correct antimicrobial or combination for undifferentiated fever in pregnant women in Southeast Asia is unknown.

Rickettsial infections in Southeast Asia: implications for local populace and febrile returned travelers

Rickettsial infections represent a major cause of non-malarial febrile illnesses among the residents of Southeast Asia and returned travelers from that region. There are several challenges in recognition, diagnosis, and management of rickettsioses endemic to Southeast Asia. This review focuses on the prevalent rickettsial infections, namely, murine typhus (Rickettsia typhi), scrub typhus (Orientia tsutsugamushi), and members of spotted fever group rickettsiae. Information on epidemiology and regional variance in the prevalence of rickettsial infections is analyzed. Clinical characteristics of main groups of rickettsioses, unusual presentations, and common pitfalls in diagnosis are further discussed. In particular, relevant epidemiologic and clinical aspects on emerging spotted fever group rickettsiae in the region, such as Rickettsia honei, R. felis, R. japonica, and R. helvetica, are presented. Furthermore, challenges in laboratory diagnosis and management aspects of rickettsial infections unique to Southeast Asia are discussed, and data on emerging resistance to antimicrobial drugs and treatment/prevention options are also reviewed.

Cytokine network in scrub typhus: high levels of interleukin-8 are associated with disease severity and mortality

Background

Scrub typhus, caused by Orientia tsutsugamushi, is endemic in the Asia-Pacific region. Mortality is high if untreated, and even with treatment as high as 10–20%, further knowledge of the immune response during scrub typhus is needed. The current study was aimed at comparing plasma levels of a variety of inflammatory mediators in scrub typhus patients and controls in South India in order to map the broader cytokine profile and their relation to disease severity and clinical outcome.

Methodology/Principal Findings

We examined plasma levels of several cytokines in scrub typhus patients (n = 129) compared to healthy controls (n = 31) and infectious disease controls (n = 31), both in the acute phase and after recovery, by multiplex technology and enzyme immunoassays. Scrub typhus patients were characterized by marked changes in the cytokine network during the acute phase, differing not only from healthy controls but also from infectious disease controls. While most of the inflammatory markers were raised in scrub typhus, platelet-derived mediators such as RANTES were markedly decreased, probably reflecting enhanced platelet activation. Some of the inflammatory markers, including various chemokines (e.g., interleukin-8, monocyte chemoattractant peptide-1 and macrophage inflammatory protein-1β) and downstream markers of inflammation (e.g., C-reactive protein and pentraxin-3), were also associated with disease severity and mortality during follow-up, with a particular strong association with interleukin-8.

Conclusions/Significance

Our findings suggest that scrub typhus is characterized by a certain cytokine profile that includes dysregulated levels of a wide range of mediators, and that this enhanced inflammation could contribute to disease severity and clinical outcome.

Scrub typhus is a potentially fatal disease affecting at least 1 million people yearly, with 1 billion at risk in the Asia-Pacific region. Caused by the bacterium Orientia tsutsugamushi, which is transmitted by mites, people with more outdoor activities, like farmers and construction workers, often low-income populations, are at higher risk. The interaction between the bacteria and cells in the patient triggers inflammatory responses, including production of several cytokines, representing both beneficial and detrimental effects to the host. In order to develop better treatment and even a vaccine, we need a better understanding of the pathophysiological mechanisms of the disease. The current study was aimed at comparing levels of inflammatory mediators in scrub typhus patients, including recovered patients, in order to map the broader cytokine profile and see how this can be related to disease severity and clinical outcome. Our findings suggest that scrub typhus is characterized by a specific cytokine profile that includes dysregulated levels of a wide range of inflammatory mediators. Further studies on this issue may lead to much-needed new therapeutic targets and prognostic markers in scrub typhus patients.

[Macrophage activation syndrome: rare complication of murine typhus]

INTRODUCTION

Typhi is one of the rickettsial species endemic in the Mediterranean countries and is associated with the zoonotic infection of murine typhus, which may have a complicated course especially in adult patients. The association with macrophage activation syndrome (MAS) has rarely been reported in the medical literature.

CASE REPORT

We describe a case of murine typhus in a diabetic woman complicated with MAS, who was effectively treated with cyclin and parenteral immunoglobulin.

CONCLUSION

The murine typhus can be exceptionally complicated with SAM. This infection should be suspected in front of the discovery of SAM.

Orientia tsutsugamushi in human scrub typhus eschars shows tropism for dendritic cells and monocytes rather than endothelium

Scrub typhus is a common and underdiagnosed cause of febrile illness in Southeast Asia, caused by infection with Orientia tsutsugamushi. Inoculation of the organism at a cutaneous mite bite site commonly results in formation of a localized pathological skin reaction termed an eschar. The site of development of the obligate intracellular bacteria within the eschar and the mechanisms of dissemination to cause systemic infection are unclear. Previous postmortem and in vitro reports demonstrated infection of endothelial cells, but recent pathophysiological investigations of typhus patients using surrogate markers of endothelial cell and leucocyte activation indicated a more prevalent host leucocyte than endothelial cell response in vivo. We therefore examined eschar skin biopsies from patients with scrub typhus to determine and characterize the phenotypes of host cells in vivo with intracellular infection by O. tsutsugamushi, using histology, immunohistochemistry, double immunofluorescence confocal laser scanning microscopy and electron microscopy. Immunophenotyping of host leucocytes infected with O. tsutsugamushi showed a tropism for host monocytes and dendritic cells, which were spatially related to different histological zones of the eschar. Infected leucocyte subsets were characterized by expression of HLADR+, with an "inflammatory" monocyte phenotype of CD14/LSP-1/CD68 positive or dendritic cell phenotype of CD1a/DCSIGN/S100/FXIIIa and CD163 positive staining, or occasional CD3 positive T-cells. Endothelial cell infection was rare, and histology did not indicate a widespread inflammatory vasculitis as the cause of the eschar. Infection of dendritic cells and activated inflammatory monocytes offers a potential route for dissemination of O. tsutsugamushi from the initial eschar site. This newly described cellular tropism for O. tsutsugamushi may influence its interaction with local host immune responses.