Clinical manifestations of scrub typhus

Clinical Characteristics and Evolution of Ocular Manifestations in Scrub Typhus

Scrub typhus, caused by Orientia tsutsugamushi infection, manifests with fever, rash, eschar, pneumonia, hepatosplenomegaly, and lymphadenopathy. We conducted a review of the ocular manifestations post-infection and found a high incidence (67%) during the recovery phase (2-4 weeks), particularly prevalent in the tropical Tsutsugamushi triangle. Despite China, only three cases of optic neuritis had been reported, suggesting its rarity due to early antibiotic administration, we present the first documented case of binocular optic neuroretinitis due to Orientia tsutsugamushi infection in China. Ophthalmologic screenings should be conducted for patients with systemic scrub typhus infection to rule out ocular involvement. Based on previous literature and our case findings, whether scrub typhus affects the anterior or posterior segment of the eye may be determined by different strains of the pathogen, and this in turn influences the visual prognosis. Early initiation of antibiotics effectively eradicated the pathogens. Studies have indicated that delayed immune inflammation, rather than direct infection, may be the underlying pathogenesis of ocular manifestations. Early and comprehensive corticosteroid therapy during secondary ocular inflammation has shown to effectively curb disease progression and preserve visual function.

C-C Motif Ligand 7 and C-C Motif Chemokine Receptor 3 Dysregulation in Patients With Scrub Typhus and Association With Mortality

BACKGROUND

Scrub typhus, caused by Orientia tsutsugamushi, involves infiltration of a mixture of perivascular lymphocytes and macrophages into affected organs. We investigated if this is characterized by chemokine dysregulation.

METHODS

mRNA expression of chemokines and receptors was screened in whole blood by cDNA microarray in a subgroup of patients and controls. Regulated transcripts were analyzed in plasma by enzyme immunoassays (chemokines) and in whole blood by quantitative polymerase chain reaction (receptors) from patients with scrub typhus (n = 129), patients with similar febrile illness without O tsutsugamushi infection (n = 31), and healthy controls (n = 31).

RESULTS

cDNA microarray identified dysregulation of the chemokines CCL18 and CCL23 and the receptor CCR3 in severe scrub typhus. Plasma CCL7 (a ligand for CCR3), CCL18, and CCL23 were higher in patients with scrub typhus, with a decline during follow-up. Conversely, mRNA levels of CCR3 and CCR8 (the receptor for CCL18) were decreased in whole blood at hospital admission, followed by an increase during follow-up. CCL7 was independently associated with disease severity. Admission CCL7 levels were associated with short-time mortality.

CONCLUSIONS

Our findings suggest that CCL7 could represent a hitherto unknown pathogenic mediator in O tsutsugamushi infection, contributing to local and systemic inflammation.

Evaluation of the Performance of Various Diagnostic Modalities Available for the Detection of Scrub Typhus in Acute Undifferentiated Febrile Illness (AUFI) Cases at a Teaching Hospital in North Chhattisgarh, India

INTRODUCTION

Due to the lack of adequate data on the effectiveness of diagnostic methods and the ambiguous clinical symptoms that overlap with other febrile illnesses, diagnosing scrub typhus is difficult. This study aims to compare the accuracy of various investigations required for the diagnosis of scrub typhus like immunoglobulin G/immunoglobulin M (IgG/IgM) rapid test, IgM enzyme-linked immunosorbent assay (ELISA), and real-time polymerase chain reaction (RT-PCR) from a patient's serum.

METHODS

This is a prospective study that includes all clinically suspected patients who visited the Outpatient Department (OPD) of Medicine and were admitted to the Medicine wards and Intensive Care Units of Rajmata Shrimati Devendra Kumari Singhdeo Government Medical College, Ambikapur, Chhattisgarh, India. The patients' samples were tested initially using the IgG/IgM rapid test, further confirmed by ELISA, and then subjected to RT-PCR for final confirmation.

RESULTS

A total of 1,620 cases of acute undifferentiated febrile illness were tested, of which 82 tested positive for scrub typhus IgM rapid test. These 82 cases were further tested for confirmation using IgM ELISA, which showed 110 positive results. Additionally, RT-PCR was applied to all 1,620 samples using the DIAGsure Tropical Fever Panel Kit (3B BlackBio Dx Limited, Bhopal, India), resulting in 98 samples testing positive for scrub typhus. Both the ELISA and the rapid diagnostic test offer high capacity for discrimination, with sensitivity and specificity of 92.40%, 93.18%, and 99.20%, 98.17%, respectively (10.9% of cases came positive in serology which was negative in RT-PCR). It can be due to its nonspecific binding with antibodies of other febrile illnesses such as malaria, enteric fever, pulmonary tuberculosis, leptospirosis, etc. Conclusion: RT-PCR has shown excellent results with a sensitivity of >95% and specificity of >99%. Given its high sensitivity and specificity, along with clinical findings, RT-PCR is highly effective in detecting scrub typhus, especially for diagnosing early stages of the disease in cases of acute febrile illness with a duration of less than seven days. In reference labs, RT-PCR is the primary method for confirmation. This paper offers a thorough assessment of all the diagnostic tests for scrub typhus that are now accessible in a setting with limited resources, such as our north Chhattisgarh region.

Two complicated cases of severe scrub typhus, eschar- a non-negligible sign: Case reports and literature review

RATIONALE

Scrub typhus is a mite-borne, acute febrile disease caused by Orientia tsutsugamushi. The endemic areas of scrub typhus are expanding, both globally and in China. Patients who are not treated promptly, are likely to die of multiple organ dysfunction syndrome.

PATIENT CONCERNS

Case I A 61-year-old female patient complained of sudden chest tightness and shortness of breath accompanied by fever for 6 days. Case II A 54-year-old male patient complained of fever and cough for 4 days and renal insufficiency for 2 days.

DIAGNOSES

Scrub typhus, multiple organ dysfunction syndrome.

INTERVENTIONS

After the definite diagnosis, both patients were treated with doxycycline and various organ supports.

OUTCOMES

The patient in case I was ultimately not salvageable. The patient in case II was successfully cured by the prompt administration of doxycycline along with continuous renal replacement therapy.

LESSONS

With early diagnosis and treatment, patients can completely recover. Eschar, a characteristic sign of scrub typhus, is often overlooked, leading to delayed diagnosis and regrettable outcomes.

Orientia tsutsugamushi Ank5 promotes NLRC5 cytoplasmic retention and degradation to inhibit MHC class I expression

How intracellular bacteria subvert the major histocompatibility complex (MHC) class I pathway is poorly understood. Here, we show that the obligate intracellular bacterium Orientia tsutsugamushi uses its effector protein, Ank5, to inhibit nuclear translocation of the MHC class I gene transactivator, NLRC5, and orchestrate its proteasomal degradation. Ank5 uses a tyrosine in its fourth ankyrin repeat to bind the NLRC5 N-terminus while its F-box directs host SCF complex ubiquitination of NLRC5 in the leucine-rich repeat region that dictates susceptibility to Orientia- and Ank5-mediated degradation. The ability of O. tsutsugamushi strains to degrade NLRC5 correlates with ank5 genomic carriage. Ectopically expressed Ank5 that can bind but not degrade NLRC5 protects the transactivator during Orientia infection. Thus, Ank5 is an immunoevasin that uses its bipartite architecture to rid host cells of NLRC5 and reduce surface MHC class I molecules. This study offers insight into how intracellular pathogens can impair MHC class I expression.

Spatio-temporal occurrence, burden, risk factors and modelling methods for estimating scrub typhus burden from global to subnational resolutions: a systematic review protocol

Background

Scrub typhus is a neglected life-threatening vector-borne disease mainly caused by the bacterium Orientia tsutsugamushi, which is occasionally transmitted to humans during feeding of larval mites. It has been estimated that more than 1 billion persons are potentially threatened and 1 million clinical cases occur annually across the world; however, it is unclear how this estimate was computed (and what the original source was) and much remains unknown regarding its global burden and risk factors. This systematic review aims to provide a comprehensive overview of the spatial-temporal distribution of scrub typhus, associated burden and risk factors at global, national and subnational resolutions, and to review the burden estimation models used at those different scales.

Methods

A systematic search for literature on scrub typhus occurrence, risk factors and modelling methods will be conducted. PubMed and five other databases will be searched for published literature, and Google Scholar and nine other databases will be used to search for grey literatures. All titles/abstracts of the searched records will be separately assessed by two reviewers, who will then screen the full-text of potential records to decide eligibility. A pre-formatted spreadsheet will be used by one reviewer to extract data from qualifying research, with a second reviewer checking the results. Data will be tabulated, synthesized descriptively, and summarized narratively for each review question. Where appropriate, meta-analyses will be conducted. The risk of bias will be assessed, and potential publication bias will be detected.

Discussion

This review will provide a comprehensive understanding of the current occurrence, spatial-temporal distribution, and burden of scrub typhus, identify associated risk factors from global to subnational resolutions, consolidate the best practice modeling framework(s) to estimate the burden of scrub typhus at various geographic/temporal resolutions, and decompose the relative contributions of various risk factors at scale.

PROSPERO Registration

CRD42022315209.

Omadacycline in the treatment of scrub typhus: Three case reports

BACKGROUND

Scrub typhus is a naturally occurring acute infectious disease that is primarily transmitted through the bites of chiggers or larval mites infected by Orientia tsutsugamushi (O. tsutsugamushi). Omadacycline, a novel tetracycline, exhibits potent antibacterial efficacy against both typical bacteria and atypical pathogens. However, omadacycline application in the treatment of scrub typhus remains limited.

CASE SUMMARY

In the present work, we report several cases of scrub typhus, with the main clinical symptoms being fever, the formation of eschars or ulcers, local or systemic lymphadenopathy, headache, myalgia and rash. Blood samples were collected before omadacycline was administered, and O. tsutsugamushi infection was confirmed through targeted next-generation sequencing (tNGS). After two days of treatment, the patients' symptoms, including fever, were alleviated, with no adverse drug reactions.

CONCLUSION

tNGS is an effective method for diagnosing scrub typhus. Omadacycline can be considered an alternative option for antiinfective therapy in patients with O. tsutsugamushi infections.

Opsoclonus: A Rare Neurological Manifestation in a Patient With Scrub Typhus Infection

Scrub typhus, prevalent in tropical regions, exhibits a wide range of symptoms, from non-specific signs to severe conditions such as pneumonia, gastroenteritis, lymphadenitis, meningitis, encephalitis, acute kidney injury, and multi-organ dysfunction syndrome. Neurological symptoms like opsoclonus are rarely seen. This report details an unusual case of a 34-year-old male who first complained of high temperature, headache, and sore muscles. Initially treated with antipyretics and oral antibiotics, his symptoms persisted and new ones emerged, leading to an emergency visit with complaints of blurred vision. Upon confirming scrub typhus with opsoclonus, appropriate antibiotics were administered. Persistent fever and opsoclonus prompted suspicion of an atypical infection. A detailed history and investigations, including IgM testing against the scrub typhus antigen, confirmed the diagnosis. Treatment with doxycycline resulted in significant symptom improvement, leading to discharge. This case underscores the need to consider atypical organisms in neurological symptoms, which can be effectively treated with timely diagnosis.

Canonical notch activation in patients with scrub typhus: association with organ dysfunction and poor outcome

PURPOSE

The mechanisms that control inflammation in scrub typhus are not fully elucidated. The Notch pathways are important regulators of inflammation and infection, but have not been investigated in scrub typhus.

METHODS

Plasma levels of the canonical Notch ligand Delta-like protein 1 (DLL1) were measured by enzyme immunoassay and RNA expression of the Notch receptors (NOTCH1, NOTCH2 and NOTCH4) in whole blood was analyzed by real-time PCR in patients with scrub typhus (n = 129), in patients with similar febrile illness without O. tsutsugamushi infection (n = 31) and in healthy controls (n = 31); all from the same area of South India.

RESULTS

Our main results were: (i) plasma DLL1 was markedly increased in scrub typhus patients at hospital admission with a significant decrease during recovery. (ii) RNA expression of NOTCH4 was decreased at admission in whole blood. (iii) A similar pattern for DLL1 and NOTCH4 was seen in febrile disease controls. (iv) Admission DLL1 in plasma was associated with disease severity and short-term survival. (vi) Regulation of Notch pathways in O. tsutsugamushi-infected monocytes as evaluated by public repository data revealed enhanced canonical Notch activation with upregulation of DLL1 and downregulation of NOTCH4.

CONCLUSION

Our findings suggest that scrub typhus patients are characterized by enhanced canonical Notch activation. Elevated plasma levels of DLL1 were associated with organ dysfunction and poor outcomes in these patients.

A cross sectional study on molecular prevalence of Orientia tsutsugamushi in household rat population of South India

This study aimed to assess the molecular prevalence of mite-borne zoonotic pathogen O. tsutsugamushi in household rats of South India through nested polymerase chain reaction amplification of O. tsutsugamushi 47-kDa htrA gene and to determine the most suitable sample type for screening of O. tsutsugamushi in rats. Out of 85 rats trapped in Tamil Nadu, Karnataka, and Puducherry regions, 47 rats were found positive for the O. tsutsugamushi genome with prevalence of 55.29 %. Among different sample types screened, faecal samples exhibited the highest positivity rate, followed by liver, spleen, kidney, and blood samples. Agreement between faecal and spleen samples of rats for the presence of O. tsutsugamushi was the highest. Principal component analysis revealed a positive correlation between the spleen, liver, and faeces and a negative correlation between blood and faeces for the presence of O. tsutsugamushi genome. These findings underscore the varied distribution of O. tsutsugamushi among different samples and indicate that the faecal and liver samples of rats are an ideal choice of samples for epidemiological studies. This is the first study to report a high level of presence of O. tsutsugamushi in faecal samples of rats.

Unveiling the burden of scrub typhus in acute febrile illness cases across India: A systematic review & meta-analysis

Background & objectives Scrub typhus is an emerging mite-borne zoonotic infection that has been overlooked, despite being one of the most widespread severe vector-borne diseases. With an estimated one billion people at risk worldwide and one million annual cases, it poses a significant public health concern. While various studies have investigated the prevalence of scrub typhus in different regions of India, a comprehensive regional systematic review and meta-analysis on the seropositivity of scrub typhus among acute febrile cases has been lacking. To address this gap, we conducted a systematic review and meta-analysis to compile information on the current seroprevalence of scrub typhus in acute febrile illness cases in India. Methods A literature search of multiple databases on prevalence of scrub typhus in acute febrile illness in India, 60 eligible studies out of 573 studies. The prevalence of individual studies was double arcsine transformed, and the pooled prevalence was calculated using inverse variance method. Results In total, these studies encompassed 34,492 febrile cases. The overall seroprevalence of scrub typhus among acute febrile illness cases in India was found to be 26.41 per cent [95% confidence interval (CI): 22.03-31.03]. Additionally, the pooled case fatality rate (based on data from six studies) among scrub typhus-positive cases yielded a case fatality rate of 7.69 per cent (95% CI: 4.37-11.72). Interpretation & conclusions This meta-analysis shows that scrub typhus is a significant health threat in India. Preventive measures to control scrub typhus need to be given priority.

mNGS helped diagnose scrub typhus-associated HLH in children: a report of two cases

Background

Scrub typhus, caused by the Orientia tsutsugamushi (Ot), is a widespread vector-borne disease transmitted by chigger mites. Hemophagocytic lymphohistiocytosis (HLH) is considered to be one of the potentially severe complications. The diagnosis of scrub typhus-associated HLH may be overlooked due to the non-specific clinical characteristics and the absence of pathognomonic eschar.

Case presentation

We obtained clinical data from two patients in the South of Sichuan, China. The first case involved a 6-year-old girl who exhibited an unexplained fever and was initially diagnosed with sepsis, HLH, and pulmonary infection. The other patient presented a more severe condition characterized by multiple organ dysfunction and was initially diagnosed with septic shock, sepsis, HLH, acute kidney injury (AKI), and pulmonary infection. At first, a specific examination for scrub typhus was not performed due to the absence of a characteristic eschar. Conventional peripheral blood cultures yielded negative results in both patients, and neither of them responded to routine antibiotics. Fortunately, the causative pathogen Orientia tsutsugamushi (Ot) was detected in the plasma samples of both patients using metagenomics next-generation sequencing (mNGS) and further confirmed by polymerase chain reaction. Subsequently, they both were treated with doxycycline and recovered quickly.

Conclusion

The unbiased mNGS provided a clinically actionable diagnosis for an uncommon pathogen-associated infectious disease that had previously evaded conventional diagnostic approaches.

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.

Scrub Typhus: An Acute Precipitant for Acute on Chronic Liver Failure

Acute-on-chronic liver failure (ACLF) is a clinical syndrome with high mortality. Many acute precipitating factors have been implicated in triggering the acute event of ACLF, with bacterial infections being a common precipitant. However, many other precipitants can cause ACLF; therefore, identification of these factors early in the golden window and their treatment can result in improved prognosis. Scrub typhus usually presents as uncomplicated acute febrile illness but rarely as complicated. Few case reports of scrub-typhus-induced acute liver failure have been reported but none with scrub-typhus-precipitating ACLF so far. Therefore, we are reporting a case of scrub-typhus-precipitating ACLF, where timely intervention with antibiotics results in improved outcome.

Case report of scrub typhus complicated by hypokalemia and multiple organ dysfunction syndrome

CONTEXT

Scrub typhus, caused by Orientia tsutsugamushi, has a wide range of clinical manifestations, including meningoencephalitis, acute renal failure, pneumonitis, myocarditis, and septic shock. However, there are no documented cases of scrub typhus with hypokalemia. In this report, we present a case of scrub typhus with hypokalemia and multiple organ failure syndrome, highlighting the importance of electrolyte imbalance in patients with scrub typhus.

CASE REPORT

A 59-year-old woman presented to the emergency department with abdominal pain that had been present for 1 day. On admission, the physical examination and laboratory test results indicated that the patient had renal, liver, and circulatory failure, and hypokalemia. She developed meningitis and disseminated intravascular coagulation during hospitalization. She recovered with appropriate management, and was discharged on day 17.

CONCLUSION

This report highlights the potential for atypical presentations of scrub typhus, including a previously undocumented association with hypokalemia. Although the contribution of hypokalemia to the patient's clinical course remains uncertain, this case underscores the importance of considering electrolyte imbalance in the management of patients with scrub typhus. Further research is warranted to better understand the relationship between scrub typhus and electrolyte imbalance.

Scrub Typhus Presenting as Bilateral Sixth Nerve Palsy

Scrub typhus, a tropical rickettsial infection, can have various neurological manifestations. Here, we present the case of an otherwise healthy 19-year-old female who presented to the emergency department with fever, headache, and diplopia. On examination, she was found to have bilateral sixth nerve palsy and bilateral papilledema. Initial unenhanced CT of the brain and CT venogram were unremarkable. The cerebrospinal fluid study was normal. Later, bloodwork revealed high titers of Orientia tsutsugamushi antibody. A thorough physical examination revealed no evidence of any eschar. She was treated with doxycycline and had significant clinical improvement with partial recovery of bilateral lateral rectus function. We want to highlight the importance of maintaining a high index of suspicion for atypical neurological presentations of scrub typhus.

Clinical and laboratory findings in scrub typhus associated Guillain-Barré syndrome in South Korea

BACKGROUND AND AIMS

Scrub typhus is an endemic disease in the fall season that occurs in a limited number of places known as the Tsutsugamushi Triangle. Peripheral neuropathy is a common complication of scrub typhus. Herein, we encountered several patients with ascending paralysis after scrub typhus infection, who were diagnosed with Guillain-Barré syndrome (GBS). We aimed to investigate the clinical and laboratory characteristics of patients who developed GBS after scrub typhus.

METHODS

Patients were retrospectively recruited from six nationwide tertiary centers in South Korea from January 2017 to December 2021. Patients who had been clinically diagnosed with GBS and confirmed to have scrub typhus via laboratory examination and/or the presence of an eschar before the onset of acute limb paralysis were included. The GBS-associated clinical and electrophysiological characteristics, outcomes, and scrub typhus-associated features were collected.

RESULTS

Of the seven enrolled patients, six were female and one was male. The median time from scrub typhus infection to the onset of limb weakness was 6 (range: 2-14) days. All patients had eschar on their bodies. Four patients (57.1%) were admitted to the intensive care unit and received artificial ventilation for respiratory distress. At 6 months, the median GBS disability score was 2 (range, 1-4) points.

INTERPRETATION

Patients with scrub typhus-associated GBS have a severe clinical presentation and require intensive treatment with additional immunotherapies. Therefore, GBS should be included in the differential diagnosis when peripheral neuropathies develop during scrub typhus treatment. Notably, scrub typhus is associated to GBS.

Neurological Manifestations of Scrub Typhus Infection in Pediatric Patient: A Case Report From Tertiary Care Hospital in Central India

Scrub typhus is a neglected tropical bacterial disease endemic in central India which can manifest as meningitis/meningoencephalitis in children. It is difficult to diagnose clinically, especially in the absence of eschar or rash. Scrub typhus is seldom considered the differential diagnosis of meningitis in the Indian subcontinent. Appropriate investigations can lead to early detection of infection and initiation of correct antibiotic treatment leading to better patient prognosis even when features of meningitis supervene. Here, we report a pediatric case of scrub typhus meningitis that could be saved due to timely investigations and initiation of appropriate antimicrobial agents.

Epidemiology of scrub typhus and other rickettsial infections (2018-22) in the hyper-endemic setting of Mizoram, North-East India

BACKGROUND

In the past decade, scrub typhus cases have been reported across India, even in regions that had no previous history of the disease. In the North-East Indian state of Mizoram, scrub typhus cases were first recorded only in 2012. However, in the last five years, the state has seen a substantial increase in the scrub typhus and other rickettsial infections. As part of the public health response, the Mizoram Government has integrated screening and line listing of scrub typhus and other rickettsial infections across all its health settings, a first in India. Here we detail the epidemiology of scrub typhus and other rickettsial infections from 2018-2022, systematically recorded across the state of Mizoram.

METHODOLOGY/PRINCIPAL FINDINGS

The line-listed data positive for scrub typhus and other rickettsial infections identified by rapid immunochromatographic test and/or Weil-Felix test from 2018-22 was used for the analysis. During this period, 22,914 cases of rickettsial infections were recorded, out of which 19,651 were scrub typhus cases. Aizawl is the worst affected, with 10,580 cases (46.17%). The average incidence of rickettsial infections is 3.54 cases per 1000 persons-year, and the case fatality rate is 0.35. Only ∼2% of the reported scrub typhus cases had eschar. Multivariate logistic regression analysis indicate patients with eschar (aOR = 2.5, p<0.05), occupational workers [farmers (aOR:3.9), businessmen (aOR:1.8), construction workers (aOR:17.9); p<0.05], and children (≤10 years) (aOR = 5.4, p<0.05) have higher odds of death due to rickettsial infections.

CONCLUSION

The integration of systematic surveillance and recording of rickettsial diseases across Mizoram has shed important insights into their prevalence, morbidity, and mortality. This study underscores the importance of active surveillance of rickettsial infections across India, as the burden could be substantially higher, and is probably going undetected.

Three cases of scrub typhus with hemorrhage: a case report and literature review

Scrub typhus (ST) is an acute focal infectious disease that is caused by Orientia tsutsugamushi. The Asia-Pacific region is an area of relatively high incidence. There is a high incidence in China, principally owing to the disease being endemic in the south of the country. The main source of ST infection is rats, which act as reservoirs of infection after being bitten by the chigger mite, and the human population is generally susceptible to the disease. ST can be controlled and treated successfully if antibiotics are administered in a timely manner. However, because it does not have a specific clinical manifestation, it is difficult to distinguish ST from other febrile diseases in clinical practice. Therefore, rapid diagnostic methods are still needed to help clinicians make a timely diagnosis. Here, we share three cases of patients with ST who experienced hemorrhage, but did not have typical skin lesions, such as eschar and ulcer, early in the course of their disease, and review the relevant literature regarding ST. We conclude that clinicians should pay attention to the risk of hemorrhage associated with this disease, and emphasize the importance of making an early diagnosis.

Metagenomics as New Tool for Diagnosis of Scrub Typhus: Two Case Reports

Scrub typhus is a vector-borne infectious disease caused by Orientia tsutsugamushi. Accurate and timely diagnosis at the early infection stage could save the patients' lives. Traditional technologies were limited to rapidly and successfully detecting Orientia tsutsugamushi due to poor specificity, especially in the condition of atypical symptoms. The technology of Metagenomic next-generation sequencing (mNGS) is amenable to finding the real pathogen because it holds potential as a diagnostic platform for unbiased pathogen identification and precision medicine. Herein, we reported two clinical case reports relative to the Orientia tsutsugamushi infection diagnosed by mNGS. We hope these two cases will improve clinical diagnosis.

Etiologies of Zoonotic Tropical Febrile Illnesses That Are Not Part of the Notifiable Diseases in Colombia

In Colombia, tropical febrile illnesses represent one of the most important causes of clinical attention. Febrile illnesses in the tropics are mainly zoonotic and have a broad etiology. The Colombian surveillance system monitors some notifiable diseases. However, several etiologies are not monitored by this system. In the present review, we describe eleven different etiologies of zoonotic tropical febrile illnesses that are not monitored by the Colombian surveillance system but have scientific, historical, and contemporary data that confirm or suggest their presence in different regions of the country: Anaplasma, Arenavirus, Bartonella, relapsing fever group Borrelia, Coxiella burnetii, Ehrlichia, Hantavirus, Mayaro virus, Orientia, Oropouche virus, and Rickettsia. These could generate a risk for the local population, travelers, and immigrants, due to which they should be included in the mandatory notification system, considering their importance for Colombian public health.

Multiple Orientia clusters and Th1-skewed chemokine profile: a cross-sectional study in patients with scrub typhus from Nepal

OBJECTIVES

Scrub typhus is an emerging infectious disease in Asia caused by Orientia tsutsugamushi (Ot). From Nepal, only scant data on the genetic epidemiology of this agent is available, and determinants of immunoregulation are poorly understood.

METHODS

Patients (n = 238) referred to the National Public Health Laboratory (Kathmandu, Nepal) from all over Nepal for suspected scrub typhus were enrolled upon positive immunoglobulin (Ig)M testing between July and October 2015. From Ot 16S and 47 kD polymerase chain reaction (PCR)-positive samples, the variable domain I of the 56 kD gene was sequenced and phylogenetically analyzed. T helper (Th) cell-associated cytokines (n = 13) and chemokines (n = 12) were quantified by multiplex bead arrays.

RESULTS

In 93/238 (39.1%) IgM-positive samples, Ot DNA was detected by quantitative PCR. Phylogenetic analysis of 56 kD sequences revealed seven distinct clusters, six of them with high homologies to strains detected in other countries. The Th1-related cytokines interferon-γ and C-X-C motif chemokine ligand 10 were strongly upregulated and correlated with bacteremia, while levels of Th2-associated chemokines were reduced. Bacteremia also correlated with concentrations of interleukin (IL)-6 and IL-10 but not tumor necrosis factor-α.

CONCLUSION

We identified a considerable genetic heterogeneity of human-pathogenic Ot strains circulating in Nepal. Acute Nepalese scrub typhus patients showed strong Th1 but impaired Th2 responses, especially on the chemokine level.

Genetic recombination of Orientia tsutsugamushi strains from scrub typhus patients in Guangxi, Southwest China, and the analysis of clinical features

Three Orientia tsutsugamushi genotypic groups belonging to two prototypes (Gilliam and Karp) were identified in scrub typhus patients from Guangxi, Southwest China. Fever, headache, pneumonia, fatigue, chill, and anorexia were the most common clinical signs. Frequent recombination was observed for their 47-kDa gene compared to 56-kDa and 16S genes. Furthermore, patients infected with the Gilliam prototype represent a much higher proportion of pneumonia (6/6, 100%) than those infected with the Karp prototype (4/8, 50%) (p-value=0.040). This discrepancy is consistent with recent animal tests on rhesus and may indicate different virulence and tissue tropism between different O. tsutsugamushi prototypes.

Vulnerability and agency in research participants' daily lives and the research encounter: A qualitative case study of participants taking part in scrub typhus research in northern Thailand

BACKGROUND

Researchers have a responsibility to protect all participants, especially vulnerable participants, from harm. Vulnerability is increasingly understood to be context specific, yet limited guidance is available regarding the vulnerability and agency of research participants in different cultural settings. This study aims to explore research participants' daily vulnerability and agency, and how these interact with participants' research experiences in their own words. Researchers' views and responses were also explored.

METHODS

A qualitative study was conducted around two scrub typhus research studies in northern Thailand. A thematic analysis was carried out on 42 semi-structured interviews with research participants, their families, researchers and key informants.

RESULTS

The majority of the research participants belonged to a hill tribe ethnic minority group. Common challenges were related to Thai language barriers, travel difficulties, uncertain legal status, unstable employment, lack of education and healthcare. We did not identify new vulnerabilities but we found that the extent of these vulnerabilities might be underestimated or even hidden from researchers in some cases. Despite these challenges people demonstrated agency in their daily lives and were often motivated and supported in this by family members. The majority of perceived research benefits were related to healthcare and gaining knowledge, while attending follow-up visits could be a burden for some.

CONCLUSIONS

Our approach to research in culturally and socioeconomically diverse settings should be more responsive to participants' specific vulnerabilities and abilities evidenced in their daily life, rather than attributing vulnerability on the basis of membership of pre-defined 'vulnerable groups'. Researchers need to be aware and responsive towards the challenges participants face locally in order to minimise the burdens of research participation whilst allowing participants to benefit from research.

Spatio-temporal occurrence, burden, risk factors and modelling methods for estimating scrub typhus burden from global to subnational resolutions: a systematic review protocol

Background: Scrub typhus is a neglected life-threatening vector-borne disease mainly caused by the bacterium Orientia tsutsugamushi, which is occasionally transmitted to humans during feeding of larval mites. It has been estimated that more than 1 billion persons potentially threatened and 1 million clinical cases occur annually across the world; however, it is unclear how this estimate was computed (and what the original source was) and much remains unknown regarding its global burden and risk factors. This systematic review aims to provide a comprehensive overview of the spatial-temporal distribution of scrub typhus, associated burden and risk factors at global, national and subnational resolutions, and to review the burden estimation models used at those different scales. Methods: A systematic search for literature on scrub typhus occurrence, risk factors and modelling methods will be conducted. PubMed and five other databases will be searched for published literature, and Google Scholar and nine other databases will be used to search for grey literatures. All titles/abstracts of the searched records will be separately assessed by two reviewers, who will then screen the full-text of potential records to decide eligibility. Two reviewers will independently perform corresponding data extraction and finally cross-check using designed standardized forms. Data will be tabulated, synthesized descriptively, and summarized narratively for each review question. Where appropriate, meta-analyses will be conducted. The risk of bias will be assessed, and potential publication bias will be detected. Discussion: This review will provide a comprehensive understanding of the current occurrence, spatial-temporal distribution, and burden of scrub typhus, identify associated risk factors from global to subnational resolutions, consolidate the best practice modeling framework(s) to estimate the burden of scrub typhus at various geographic/temporal resolutions, and decompose the relative contributions of various risk factors at scale. PROSPERO Registration: CRD42022315209

Direct diagnosis of scrub typhus by full-length 16S ribosomal RNA gene analysis using Oxford Nanopore sequencing

Scrub typhus (caused by Orientia tsutsugamushi) is a neglected and underdiagnosed disease due to its non-specific clinical presentation and challenging diagnostics. We document the first study of direct diagnosis of scrub typhus from the blood sample of a patient by full-length 16S ribosomal RNA gene amplicon analysis using Oxford Nanopore sequencing.

Acute Pancreatitis, Shock, and Multiple Organ Dysfunction Syndrome in Scrub Typhus

Scrub typhus is an endemic disease caused by the bites of infected chiggers (larval mites) harboring causative bacteria Orientia tsutsugamushi. Acute pancreatitis is a rare but occasionally fatal complication of scrub typhus infection caused by vascular and perivascular inflammation of the pancreas.A 34-year-old female presented with severe epigastric pain and multiple episodes of vomiting. Extensive evaluation of the patient revealed acute pancreatitis secondary to scrub typhus. The patient also had septic shock and multiple organ dysfunction syndrome. The patient was mechanically ventilated and treated with doxycycline, and pancreatitis was managed conservatively.

Systematic Surveillance of Rickettsial Diseases in 27 Hospitals from 26 Provinces throughout Vietnam

In Vietnam, the public health burden of rickettsial infections continues to be underestimated due to knowledge gaps in the epidemiology of these diseases. We conducted a systematic study among 27 hospitals from 26 provinces in eight ecological regions throughout Vietnam to investigate the prevalence, distribution, and clinical characteristics of rickettsial diseases. We recruited 1834 patients in the study from April 2018 to October 2019. The findings showed that rickettsial diseases were common among undifferentiated febrile patients, with 564 (30.8%) patients positive by qPCR for scrub typhus, murine typhus or spotted fever. Scrub typhus (484, 85.8%) was the most common rickettsial disease, followed by murine typhus (67, 11.9%) and spotted fever (10, 1.8%). Rickettsial diseases were widely distributed in all regions of Vietnam and presented with nonspecific clinical manifestations.

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.

Contemporary diagnostics for medically relevant fastidious microorganisms belonging to the genera Anaplasma, Bartonella, Coxiella, Orientia, and Rickettsia

Many of the human infectious pathogens—especially the zoonotic or vector-borne bacteria—are fastidious organisms that are difficult to cultivate because of their strong adaption to the infected host culminating in their near-complete physiological dependence on this environment. These bacterial species exhibit reduced multiplication rates once they are removed from their optimal ecological niche. This fact complicates the laboratory diagnosis of the disease and hinders the detection and further characterization of the underlying organisms, e.g. at the level of their resistance to antibiotics due to their slow growth. Here, we describe the current state of microbiological diagnostics for five genera of human pathogens with a fastidious laboratory lifestyle. For Anaplasma spp., Bartonella spp., Coxiella burnetii, Orientia spp. and Rickettsia spp., we will summarize the existing diagnostic protocols, the specific limitations for implementation of novel diagnostic approaches and the need for further optimization or expansion of the diagnostic armamentarium. We will reflect upon the diagnostic opportunities provided by new technologies including mass spectrometry and next-generation nucleic acid sequencing. Finally, we will review the (im)possibilities of rapidly developing new in vitro diagnostic tools for diseases of which the causative agents are fastidiously growing and therefore hard to detect.

Developing a multiplex loop-mediated isothermal amplification assay (LAMP) to determine severe fever with thrombocytopenia syndrome (SFTS) and scrub typhus

Severe fever with thrombocytopenia syndrome (SFTS) and scrub typhus are endemic zoonotic diseases that pose significant public health threats in East Asia. As these two diseases share common clinical features, as well as overlapping disease regions, it is difficult to differentiate between SFTS and scrub typhus. A multiplex reverse-transcription loop‑mediated isothermal amplification (RT-LAMP) assay was developed to detect large segments and GroES genes for SFTS virus (SFTSV) and Orientia tsutsugamushi (OT). The performance of the RT-LAMP assay was compared and evaluated with those of commercial PowerChek™ SFTSV real-time PCR and LiliF™ TSUTSU nested PCR for 23 SFTS and 12 scrub typhus clinical samples, respectively. The multiplex SFTSV/OT/Internal control (IC) RT-LAMP assay showed comparable sensitivity (91.3%) with that of commercial PowerChek™ SFTSV Real-time PCR (95.6%) and higher sensitivity (91.6%) than that of LiliF™ TSUTSU nested PCR (75%). In addition, the multiplex SFTSV/OT RT-LAMP assay showed 100% specificity and no cross-reactivity for blood from uninfected healthy patients and samples from patients infected with other fever viruses. Thus, the multiplex SFTSV/OT/IC RT-LAMP assay could serve as a useful point-of-care molecular diagnostic test for SFTS and scrub typhus.

An unusual presentation of scrub typhus in a child: a case report

Background

Scrub Typhus (ST) is an acute, febrile zoonotic disease caused by the bacterium Orientia tsutsugamushi which is endemic to the Asia-Pacific region. Infected adults rarely present with sensorineural hearing loss and otalgia. Though few cases of pediatric cases are known to present with otalgia, no pediatric cases of sensorineural deafness complicating ST have been reported to date.

Case presentation

A 5-year-old, previously healthy girl presented with a one-week history of high-grade intermittent fever, Headache and right ear pain with a recent onset of reduced hearing. She had a fever up to 39 °C, cervical lymphadenopathy, bilateral pleural effusion with diffuse infiltrations, and mild hepatosplenomegaly with no evidence of rash. Her initial examination was normal except for mildly enlarged tonsils. Unilateral right ear hearing loss was noted using Weber’s test. Evidence of progressive, mild anemia, and raised inflammatory markers was noted. Diagnosis of scrub typhus was confirmed by positive detection of Orentia tsutsugamushi IgM antibodies on rapid diagnostic test and the presence of chigger mite in the right external auditory canal on repeat examination. She responded dramatically to the empirical treatment of ceftriaxone and doxycycline. On follow-up, she did not have any residual hearing loss and her ear pain had resolved completely.

Conclusion

Acute onset hearing loss or severe otalgia with or without findings should be an important diagnostic clue for suspecting scrub typhus in patients who present with a history of fever especially in endemic areas.

A suspected surgical case of acute abdomen: A case report of scrub typhus

Introduction

Scrub typhus presents with diverse clinical manifestations which range from sub-clinical disease to organ failure and fatal disease.

Case presentation

The patient presented with fever followed by acute abdominal pain and later developed septic shock with multi-organ failure. Radiological evaluations were normal, however, on thorough physical examination, an eschar was found in her right inguinal region.

Clinical discussion

Aside from classical clinical symptoms, it can also involve various organs, most commonly of respiratory, cardiovascular and hepatic systems. Additionally, suspected patients should be thoroughly examined for the presence of an eschar, especially over the covered areas such as the groin, genitalia, infra-mammary area and axilla.

Conclusion

Scrub typhus should be considered in all patients from an endemic area presenting as acute undifferentiated febrile illness associated with organ involvement. Positive finding of an eschar and high index of suspicion for the various presentations of scrub typhus can avoid unnecessary surgical exploration and aid in prompt diagnosis and treatment.

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The presentation of scrub typhus can either be non-specific, associated with pain abdomen or other organ dysfunction.

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It should be considered in all patients from an endemic area with acute undifferentiated febrile illness and organ involvement.

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Suspected patients should be thoroughly examined for the presence of an eschar, including the covered areas.

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High index of suspicion for its various presentations can avoid unnecessary surgical exploration and aid in prompt management.

Differential analysis of Orientia tsutsugamushi genomes for therapeutic target identification and possible intervention through natural product inhibitor screening

Orientia tsutsugamushi (Ott) is a causative agent of scrub typhus, and one of the emerging pathogens that could affect a large human population. It is one of the misdiagnosed and under-reported, febrile illnesses that infects various body organs (skin, heart, lung, kidney, and brain). The control of this infection is hampered due to the lack of drugs or vaccine against it. This study was undertaken to identify potential drug targets from the core genome of Ott and investigate novel natural product inhibitors against them. Hence, the available genomes for 22 strains of Ott were downloaded from the PATRIC database, and pan-genomic analysis was performed. Only 202 genes were present in the core region. Among these, 94 were identified as essential, 32 non-homologous to humans, nine non-homologous to useful gut flora and a single gene dapD as a drug target. Product of this gene (2,3,4,5-tetrahydropyridine-2-carboxylate N-succinyltransferase) was modeled and docked against traditional Indian (Ayurvedic) and Chinese phytochemical libraries, with best hits selected for docking, based on multiple target-drug/s interactions and minimum energy scores. ADMET profiling and molecular dynamics simulation was performed for top three compounds from each library to assess the toxicity and stability, respectively. We presume that these compounds (ZINC8214635, ZINC32793028, ZINC08101133, ZINC85625167, ZINC06018678, and ZINC13377938) could be successful inhibitors of Ott. However, in-depth experimental and clinical research is needed for further validation.

Acalculous Cholecystitis in a Young Adult with Scrub Typhus: A Case Report and Epidemiology of Scrub Typhus in the Maldives

Scrub typhus is a neglected tropical disease predominantly occurring in Asia. The causative agent is a bacterium transmitted by the larval stage of mites found in rural vegetation in endemic regions. Cases of scrub typhus frequently present as acute undifferentiated febrile illness, and without early diagnosis and treatment, the disease can develop fatal complications. We retrospectively reviewed de-identified data from a 23-year-old woman who presented to an emergency department with complaints of worsening abdominal pain. On presentation, she appeared jaundiced and toxic-looking. Other positive findings on abdominal examination were a positive Murphey’s sign, abdominal guarding and hepatosplenomegaly. Magnetic resonance cholangiopancreatography demonstrated acalculous cholecystitis. Additional findings included eschar on the medial aspect of the left thigh with inguinal regional lymphadenopathy. Further, positive results were obtained for immunoglobulins M and G, confirming scrub typhus. The workup for other infectious causes of acute acalculous cholecystitis (AAC) detected antibodies against human herpesvirus 4 (Epstein–Barr virus), suggesting an alternative cause of AAC. Whether that represented re-activation of the Epstein–Barr virus could not be determined. As other reports have described acute acalculous cholecystitis in adult scrub typhus patients, we recommend doxycycline to treat acute acalculous cholecystitis in endemic regions while awaiting serological confirmation.

The Early Diagnosis of Scrub Typhus by Metagenomic Next-Generation Sequencing

Introduction: Scrub typhus is a mite-borne infection widespread in Southeast Asia, with clinical symptoms such as fever, chills, skin rash, eschar at the bite site, and other signs of acute febrile illness. The Rickettsia pathogen (Orientia tsutsugamushi) is always difficult to be diagnosed at an early stage by traditional clinical diagnostic methods, especially for patients without typical eschar. This greatly increases the mortality of patients with scrub typhus. A new approach should be introduced to improve its clinical diagnosis.

Methods: During May 2018 to March 2021, 13 samples from 10 patients with suspected scrub typhus were collected. Metagenomic next-generation sequencing (mNGS) and other diagnostic methods (including serology using Weil–Felix reaction and indirect immunofluorescence test (IIFT) for scrub typhus and respiratory tract profile IgM as well as culture for routine bacteria) were used to identify the pathogens in this study.

Results: The results of mNGS were all positive, with mapped reads of O. tsutsugamushi ranging from 1 to 460. Eight patients (80%) were diagnosed as scrub typhus. The other two were diagnosed as suspected scrub typhus due to the limited number of reads of the pathogen (one and two, respectively). According to clinical evidences, nine of the 10 patients were finally diagnosed as scrub typhus, except for patient 9 (suspected scrub typhus by mNGS with one specific reads of the pathogen) diagnosed as acute exacerbation of chronic obstructive pulmonary disease. For the five scrub typhus patients without typical eschar, mNGS gave all positive results (4–460 specific reads). For other methods, only Weil–Felix reaction of one patient detected the pathogen. In addition, the respiratory tract profile (IgM) detected various pathogens, but all were confirmed to be false positive.

Conclusions: mNGS performed better than conventional clinical methods to early diagnose scrub typhus. This approach can be routinely carried out for early and precise diagnosis in clinical infections, especially for those hard to be identified by traditional diagnostic methods.

Mortality and complications of scrub typhus in the paediatric population: a systematic review and meta-analysis

Scrub typhus is a leading cause of treatable febrile illness. It can produce complications and dysfunction of multiple organs in children and is associated with considerable mortality. We attempted to perform a systematic review of original articles published between 1990 to 2020 based on certain selection criteria to estimate the case fatality risk of this disease in children. We addressed the pattern of complications of this disease with its impact on mortality We calculated pooled prevalence with a random effects model (restricted maximum likelihood method) that assumed varying effect sizes between studies using R statistical software. We reported the case fatality rate and its 95% confidence intervals (CIs) in the pooled analysis. Thirty-seven articles with a total of 3329 children were identified for inclusion. The case fatality rate was 1.1% (CI 0.05 to 2, I2=58% and prediction interval 0-6%). The mortality rate showed a declining trend over the last 5 y. Hepatitis (30.68% [95% CI 18.52 to 44.38]) remains the most common complication, followed by shock (14.45% [95% CI 7.71 to 22.85]), pneumonia (14.71% [95% CI 9.76 to 20.48]), acute kidney injury (13.72% [95% CI 8.49 to 19.97]) and meningitis/meningoencephalitis (11.57% [95% CI 7.83 to 15.92]). Multi-organ dysfunction syndrome was the main contributor to mortality.

Halved Incidence of Scrub Typhus after Travel Restrictions to Confine a Surge of COVID-19 in Taiwan

Scrub typhus is a rickettsial disease that is usually transmitted by mite exposure. Infected patients may present with a fever, fatigue, headache, and muscle pain. A blackish skin lesion, called eschar, is pathognomic. The mortality rate in untreated cases is high. The first case of scrub typhus in Taiwan was reported in 1908 during the Japanese colonization. In this article, using the National Infectious Disease Statistics System (NIDSS) from the Taiwan CDC, we analyzed the dynamic incidence of scrub typhus from 2016 to 2021, both seasonally and geographically. In addition, we asked whether the recent travel restrictions and social distancing policy in Taiwan (19 May to 27 July 2021), implemented due to the COVID-19 outbreak, would change the incidence of scrub typhus. The results showed that scrub typhus was most common in summer, with an incidence almost twofold greater than that in winter or spring. Most cases were identified in rural regions. Interestingly, there was a significant 52% reduction in the summer incidence in 2021, compared to the average summer incidence of the past 5 years. This reduction coincided with the countrywide lockdown measures and travel restrictions. The restricted measures for outdoor activities may have contributed to the reduced incidence of scrub typhus.

Outcome of scrub typhus in pregnancy during COVID-19 pandemic: A case report

Coronavirus disease 2019 (COVID-19) pandemic has emerged as the major public health threat in recent times. Although associated with high morbidity and mortality affecting all age groups across populations, “pregnant women” represent a subgroup that needs extra surveillance. We present the case of a primigravida in her advanced pregnancy presenting with acute febrile illness with flu-like symptoms. The clinico-radiological picture was suspicious for COVID-19; however, she tested negative for COVID-19 on two occasions. On further investigations, she tested positive for Scrub typhus (IgM-ELISA) and responded to treatment with doxycycline. However, due to the ongoing COVID-19 pandemic, much time was lost before suspecting and reaching the final diagnosis. Therefore, the patient had to suffer due to delayed medical intervention and intrauterine fetal death. Despite the unprecedented rise of COVID-19 in pregnant women in recent times, we should not forget about other tropical illnesses, which can mimic COVID-19 in clinical presentation and affect feto-maternal outcomes adversely.

Interferon receptor-deficient mice are susceptible to eschar-associated rickettsiosis

Arthropod-borne rickettsial pathogens cause mild and severe human disease worldwide. The tick-borne pathogen Rickettsia parkeri elicits skin lesions (eschars) and disseminated disease in humans; however, inbred mice are generally resistant to infection. We report that intradermal infection of mice lacking both interferon receptors (Ifnar1-/-;Ifngr1-/-) with as few as 10 R. parkeri elicits eschar formation and disseminated, lethal disease. Similar to human infection, eschars exhibited necrosis and inflammation, with bacteria primarily found in leukocytes. Using this model, we find that the actin-based motility factor Sca2 is required for dissemination from the skin to internal organs, and the outer membrane protein OmpB contributes to eschar formation. Immunizing Ifnar1-/-;Ifngr1-/- mice with sca2 and ompB mutant R. parkeri protects against rechallenge, revealing live-attenuated vaccine candidates. Thus, Ifnar1-/-;Ifngr1-/- mice are a tractable model to investigate rickettsiosis, virulence factors, and immunity. Our results further suggest that discrepancies between mouse and human susceptibility may be due to differences in interferon signaling.

Exploring Tropical Infections: A Focus on Scrub Typhus

Scrub typhus is caused by Orientia tsutsugamushi and has a near global prevalence. It is associated with local and systemic manifestations that lead to morbidity and mortality. Given the nonspecific presentation of fever in a returning traveler, a high index of suspicion and thorough skin examination for eschar are critical to establishing a diagnosis. Early treatment is crucial to avoid severe outcomes, further highlighting the need to include scrub typhus in differential diagnosis. An accompanying narrative case explores the epidemiology, diagnosis, and management of scrub typhus.

Pan-proteome profiling of emerging and re-emerging zoonotic pathogen Orientia tsutsugamushi for getting insight into microbial pathogenesis

With the occurrence and evolution of antibiotic and multidrug resistance in bacteria most of the existing remedies are becoming ineffective. The pan-proteome exploration of the bacterial pathogens helps to identify the wide spectrum therapeutic targets which will be effective against all strains in a species. The current study is focused on the pan-proteome profiling of zoonotic pathogen Orientia tsutsugamushi (Ott) for the identification of potential therapeutic targets. The pan-proteome of Ott is estimated to be extensive in nature that has 1429 protein clusters, out of which 694 were core, 391 were accessory, and 344 were unique. It was revealed that 622 proteins were essential, 222 proteins were virulent factors, and 42 proteins were involved in antibiotic resistance. The potential therapeutic targets were further classified into eleven broad classes among which gene expression and regulation, transport, and metabolism were dominant. The biological interactome analysis of therapeutic targets revealed that an ample amount of interactions were present among the proteins involved in DNA replication, ribosome assembly, cellwall metabolism, cell division, and antimicrobial resistance. The predicted therapeutic targets from the pan-proteome of Ott are involved in various biological processes, virulence, and antibiotic resistance; hence envisioned as potential candidates for drug discovery to combat scrub typhus.

Pathogens in Vasculitis: Is It Really Idiopathic?

Vasculitis is an autoimmune disease characterized by the infiltration of leukocytes in blood vessels. An increasing number of studies on human and animal models have implicated various microorganisms in the pathogenesis of vasculitis. Previous studies have shown the presence of infectious agents, including viruses, bacteria, and fungi, in diseased vessels. However, despite continued research, the link between infection and vasculitis is not fully understood, possibly owing to the lack of appropriate animal models that mirror human disease and the technical limitations of pathogen detection in blood vessels. Among the pathogen-induced animal models, Candida albicans water-soluble fraction (CAWS)-induced coronary arteritis is currently considered one of the representative models of Kawasaki (KD) disease. Advances in metagenomic next-generation sequencing have enabled the detection of all nucleic acids in tissue, which can help identify candidate pathogens, including previously unidentified viruses. In this review, we discuss the findings from reports on pathogen-associated vasculitis in animal models and humans, with a specific focus on the investigation of the pathogenesis of vasculitis. Further studies on animal models and microbes in diseased vessels may provide important insights into the pathogenesis of vasculitis, which is often considered an idiopathic disease.

The burden of scrub typhus in India: A systematic review

BACKGROUND

Scrub typhus, a vector-borne zoonotic infection caused by the bacteria Orientia tsutsugamushi, is one of the most common and clinically important rickettsial infections worldwide. An estimated one million cases occur annually with a high case fatality rate. Although scrub typhus is a major public health threat in India, the burden and distribution remains unclear. We aimed to estimate the burden of scrub typhus in India.

METHODOLOGY

We performed a systematic review of published literature on scrub typhus from India to extract information on epidemiology, morbidity, and mortality. Important databases were searched using keywords and appropriate combinations. We identified observational, interventional, and population-based studies and extracted the data to evaluate the number of cases diagnosed using serology or PCR and the number of deaths due to scrub typhus. We conducted a systematic narrative synthesis to summarize included studies.

PRINCIPAL FINDINGS

In the last decade, there were 18,781 confirmed scrub typhus cases reported in 138 hospital-based studies and two community-based studies. IgM ELISA was used in 122 studies to confirm the cases in majority (89%). The proportion of scrub typhus among acute undifferentiated febrile illness (AUFI) studies was 25.3%, and community seroprevalence was 34.2%. Ninety studies had data published on multiple organ involvement out of which 17.4% of cases had multiple organ dysfunction syndromes, 20.4% patients required ICU admission, and 19.1% needed ventilation. The overall case-fatality rate was 6.3%, and the mortality among those with multi-organ dysfunction syndrome was as high as 38.9%.

CONCLUSION/SIGNIFICANCE

Scrub typhus, a common acute febrile illness in India causing severe morbidity, accounts for a large number of deaths. The burden of the disease has been underappreciated. Early diagnosis and prompt treatment can significantly reduce complications and mortality. Establishing good surveillance and instituting appropriate control measures are urgently needed.

Scrub typhus: a reemerging infection

PURPOSE OF REVIEW

Scrub typhus, caused by Orientia tsutsugamushi, is a widely neglected disease which is gaining global momentum because of its resurgence patterns. The disease is now being reported in newer regions as well as areas previously endemic areas. In this review, we aim to comprehensively review the data available to assist physicians in making an accurate diagnosis and appropriate management of the disease.

RECENT FINDINGS

Several diagnostic tests have been developed for confirming scrub typhus. However, there is lack of clarity on which tests are most appropriate in a given clinical scenario. A recent study has demonstrated that in early disease (<7 days) when serological tests remain negative, the quantitative polymerase chain reaction is the most sensitive test. Among the serological tests, both IgM enzyme-linked immunosorbent assay as well as rapid diagnostic tests revealed excellent sensitivities and specificities.

SUMMARY

With the reemergence of scrub typhus, a high degree of clinical suspicion is required to appropriately diagnose this disease which presents as an acute febrile illness. It can progress to develop various complications leading to multi-organ dysfunction syndrome. Mild illness responds well to antibiotic treatment with doxycycline and azithromycin. Further studies are required to determine the most optimal therapy in severe scrub typhus infections and superiority of one drug over the other.

Scrub typhus and lateral rectus palsy: an uncommon presentation of a common illness

Scrub typhus is a zoonosis, which usually manifests as an acute febrile illness. It is caused by a rickettsia, Orientia tsutsugamushi, which is endemic in the Asian region. It can present with varied clinical manifestations, ranging from acute febrile illness to life-threatening multiorgan dysfunction syndrome. Central nervous system involvement in the form of altered sensorium and/or meningitis is frequently observed in scrub typhus. However, isolated cranial nerve involvement is uncommon and so far only a few such cases have been reported in the literature. We present a rare case of scrub typhus with fever and diplopia at presentation, which completely improved with doxycycline-based treatment.

Seroprevalence and Clinical Features of Scrub Typhus among Febrile Patients Attending a Referral Hospital in Kathmandu, Nepal

(1) Background: Scrub typhus (ST) is endemic to Nepal. It is often underdiagnosed and misdiagnosed due to non-specific clinical presentation coupled with limited microbiological facilities, leading to adverse clinical outcomes. This study aimed to assess the seroprevalence of scrub typhus in febrile patients attending Sukraraj Tropical and Infectious Disease Hospital (STIDH), Nepal, from August 2018 to April 2019. (2) Materials and Method: Blood/serum samples and clinical and demographic data of adult febrile patients (≥19 years) who attended or were referred to the hospital were collected after obtaining written informed consent from the participants excluding immunocompromised individuals. Collected blood/serum samples were subjected to hematological, biochemical, and serological tests. A serological test for scrub typhus was performed using the ImmuneMed scrub typhus rapid diagnostic test kit. Data generated were analyzed using SPSS software version 24.0. (3) Results: Amongst the 2070 febrile patients, 462 (22.3%) were seropositive to at least one etiological agent of febrile illnesses (scrub typhus: 253 cases, dengue: 101 cases, leptospirosis: 9, brucellosis: 52, malaria: 9 and kala-azar: 20 cases). Scrub typhus accounted for 12.2% (n = 253) of total febrile illnesses followed by dengue (4.9%, n = 101). Mixed seropositivity of scrub typhus with dengue, brucellosis, and typhoid was found in 12 (0.6%), 9 (0.4%), and 5 (0.2%) cases, respectively. Among 253 scrub typhus patients, 53.4% were female. Among the 154 patients, the most common symptoms were fever (100%), headache (79.2%), sweating (70.1%), breathing difficulty (51.3%), redness of the eye (43.5%), and pathognomonic eschar was observed in 9.1% patients. Fifty percent of scrub typhus patients had low platelet count and >30% of patients had an elevated level of liver enzymes (such as serum glutamic oxaloacetic transaminase (SGPT) and serum glutamic pyruvic transaminase (SGOT). (4) Conclusion: Scrub typhus is a considerable cause of febrile illness in Nepal. Females apparently have a higher chance of acquiring scrub typhus. ST presents nonspecific clinical presentation. The diagnostic dilemma of typhus patients can be minimized by the early monitoring of ST-associated symptoms. The country's health system needs to be strengthened for early outbreak detection, and immediate response actions against scrub typhus to control the future outbreak of ST.

Screening and genotyping of Orientia tsutsugamushi from field-collected on-host chiggers (Acari: Prostigmata) recovered from a positive scrub typhus locality in Kelantan, Malaysia

Orientia tsutsugamushi is the causative agent of scrub typhus vectored by larval stages of trombiculid mites (chiggers) that occur in most tropical regions of Southeast Asia. A total of 242 chiggers extracted from eight small mammals captured from a positive scrub typhus locality in Kelantan, Malaysia, were screened for the presence of O. tsutsugamushi. The chiggers were grouped in 16 pools for extraction of DNA prior to screening of O. tsutsugamushi based on the nucleotide sequence of 56-kDa type specific antigen (TSA) gene using nested polymerase chain reaction. Two species of on-host chiggers were identified, the one, Leptotrombidium deliense, much more dominant (94.8%) than the other, Ascoshoengastia sp. (5.2%). The pathogen was detected in two pools (12.5%) of L. deliense recovered from Rattus rattus and Tupaia sp. The 56-kDa TSA gene sequence analysis revealed the O. tsutsugamushi harboured in those chiggers were Karp prototype strain with high similarity (99.3%). Findings of this study strongly supported the existence of scrub typhus infections in certain parts of Malaysia which agrees with previous local reports. Moreover, this study highlighted the pressing need of a large-scale close observation of O. tsutsugamushi DNA sequences from chiggers that can probably be collected from other positive scrub typhus localities to precisely provide the distribution and prevalence of this zoonotic pathogen.