Neuroinflammation associated with scrub typhus and spotted fever group rickettsioses

Diagnostic markers of acute encephalitis syndrome and COVID-associated multisystem inflammatory syndrome in children from Southern India

Acute encephalitis syndrome (AES) in children poses a significant public health challenge in India. This study aims to explore the utility of host inflammatory mediators and neurofilament (NfL) levels in distinguishing etiologies, assessing disease severity, and predicting outcomes in AES. We assessed 12 mediators in serum (n = 58) and 11 in cerebrospinal fluid (CSF) (n = 42) from 62 children with AES due to scrub typhus, viral etiologies, and COVID-associated multisystem inflammatory syndrome (MIS-C) in Southern India. Additionally, NfL levels in serum (n = 20) and CSF (n = 18) were examined. Clinical data, including Glasgow coma scale (GCS) and Liverpool outcome scores, were recorded. Examining serum and CSF markers in the three AES etiology groups revealed notable distinctions, with scrub typhus differing significantly from viral and MIS-C causes. Viral causes had elevated serum CCL11 and CCL2 compared with scrub typhus, while MIS-C cases showed higher HGF levels than scrub typhus. However, CSF analysis showed a distinct pattern with the scrub typhus group exhibiting elevated levels of IL-1RA, IL-1β, and TNF compared with MIS-C, and lower CCL2 levels compared with the viral group. Modeling the characteristic features, we identified that age ≥3 years with serum CCL11 < 180 pg/mL effectively distinguished scrub typhus from other AES causes. Elevated serum CCL11, HGF, and IL-6:IL-10 ratio were associated with poor outcomes (p = 0.038, 0.005, 0.02). Positive CSF and serum NfL correlation, and negative GCS and serum NfL correlation were observed. Median NfL levels were higher in children with abnormal admission GCS and poor outcomes. Measuring immune mediators and brain injury markers in AES provides valuable diagnostic insights, with the potential to facilitate rapid diagnosis and prognosis. The correlation between CSF and serum NfL, along with distinctive serum cytokine profiles across various etiologies, indicates the adequacy of blood samples alone for assessment and monitoring. The association of elevated levels of CCL11, HGF, and an increased IL-6:IL-10 ratio with adverse outcomes suggests promising avenues for therapeutic exploration, warranting further investigation.

Japanese spotted fever complicated by acute sensorineural hearing loss

Japanese spotted fever is an emerging rickettsiosis caused by Rickettsia japonica and is characterized by high fever, rash, and eschar formation. Other symptoms are often vague and nonspecific and include headaches, nausea, vomiting, and myalgia. We present a case of a 46-year-old woman with Japanese spotted fever, complicated by transient bilateral sensorineural hearing loss and presenting cutaneous IgM/IgG immune complex vasculitis. The patient was admitted with a history of several days of high fever, generalized skin erythema, and hearing impairment. Laboratory findings revealed thrombocytopenia and elevated liver enzyme and C-reactive protein levels. Pure-tone audiometry revealed bilateral sensorineural hearing loss, and a skin biopsy revealed leukocytoclastic vasculitis with deposition of C3 and IgM on the vessel walls. Under the tentative diagnosis of rickettsiosis, scrub typhus, or Japanese spotted fever, the patient was treated with minocycline, and her symptoms improved within approximately 10 days. A definitive diagnosis was made on the basis of a serological test showing increased antibody levels against Rickettsia japonica. Japanese spotted fever can cause transient sensorineural hearing loss, a rare complication that presents with cutaneous IgM/IgG immune complex vasculitis.

Clinical, laboratory profile and molecular characterization of Orientia tsutsugamushi among fatal scrub typhus patients from Karnataka, India

BACKGROUND

Scrub typhus is a vector-borne infection caused by the obligate intracellular organism Orientia tsutsugamushi. In some cases, scrub typhus can result in severe complications, multiorgan failure and death.

OBJECTIVE

To study the clinical and laboratory profiles of patients who succumbed to scrub typhus.

METHODS

A prospective cohort study was conducted from August 2019 through April 2023 on scrub typhus patients admitted to our hospital. Clinical and laboratory parameters of all the patients were recorded, and blood samples were drawn. To confirm scrub typhus, a nested polymerase chain reaction (nPCR) was performed in collected samples. Viable amplicons were sequenced, and phylogenetic analyses were performed to identify infecting genotypes.

RESULTS

A total of 261 patients were enrolled. Of these, nine (3.45%) patients succumbed at a median (Interquartile Range) duration of 5 (1.5, 10.5) days after admission. Sepsis with septic shock (9, 100%) and acute kidney injury (AKI) (6, 66%) were noted among the succumbed patients. All the succumbed patients (100%) required intensive care admission, inotropic and ventilatory support. While 5 (55%) patients required dialysis, two (22%) required blood transfusion. Three (33%) patient samples were co-positive for Leptospira IgM, and four (44%) patients had superinfection with Candida tropicalis, multi-drug-resistant (MDR) E. Coli sepsis, pan drug-resistant (PDR) Acinetobacter Baumanii, and Klebsiella pneumoniae. Phylogenetic analysis revealed Orientia tsutsugamushi Japanese Gilliam-variant (JG-v) like (50%), Karp-like (37.5%), and Japanese Gilliam (JG) like (12.5%) strains among succumbed patients.

CONCLUSION

Delay in scrub typhus diagnosis can result in severe complications, septic shock, and multisystem organ failure, culminating in death.

Case Report: Encephalitis with Initial Manifestation of Orientia Tsutsugamushi Infection Detected by Metagenomic Next-Generation Sequencing

Purpose

Scrub typhus, caused by Orientia tsutsugamushi, is characterized by fever, eschars, lymphadenopathy, and rash. The absence of eschars in some cases makes it difficult to distinguish it from other diseases, complicating the diagnosis process. Atypical Scrub typhus is difficult to diagnose and often leads to delayed treatment. Therefore, early diagnosis and treatment through effective detection methods have high clinical value. Here, a case of scrub typhus with encephalitis symptoms is reported.

Patients and Methods

A 64-year-old man and mNGS testing.

Results

A 64-year-old man developed cough, headache, and fever, dismissing it as a respiratory tract infection. Initial treatment with cephalosporin antibiotics had minimal effect. Admission to the respiratory department showed inflammation in blood tests. Subsequent CT and further treatment provided no improvement. Multidisciplinary discussions and neurology department guidance were conducted to consider the suspected diagnosis of encephalitis in the patient. After improving the mNGS detection, the patient was diagnosed with "Orientia tsutsugamushi encephalitis". After treatment with doxycycline, the patient's symptoms were alleviated. He remained afebrile in follow-up and adhered well to medical advice.

Conclusion

Our case demonstrates that it is difficult to distinguish Orientia tsutsugamushi encephalitis from central nervous system infectious diseases such as meningitis and encephalitis using conventional diagnostic methods, which may affect the treatment plan for the disease. mNGS is a useful and valuable method for early diagnosis of scrub typhus.

Differential cellular immune responses against Orientia tsutsugamushi Karp and Gilliam strains following acute infection in mice

Scrub typhus is a leading cause of febrile illness in endemic countries due to infection with Orientia tsutsugamushi (Ot), a seriously understudied intracellular bacterium. Pulmonary involvement associated with vascular parasitism in patients is common and can develop into life threatening interstitial pneumonia. The diverse antigenicity of Ot genotypes and inter-strain differences in genome content are connected to varied virulence and clinical outcomes; however, detailed studies of strain-related pulmonary immune responses in human patients or small animal models of infection are lacking. In this study, we have used two clinically prevalent bacterial strains (Karp and Gilliam) to reveal cellular immune responses in inflamed lungs and potential biomarkers of disease severity. The results demonstrate that outbred CD-1 mice are highly susceptible to both Karp and Gilliam strains; however, C57BL/6 (B6) mice were susceptible to Karp, but resistant to Gilliam (with self-limiting infection), corresponding to their tissue bacterial burdens and lung pathological changes. Multicolor flow cytometric analyses of perfused B6 mouse lungs revealed robust and sustained influx and activation of innate immune cells (macrophages, neutrophils, and NK cells), followed by CD4+ and CD8+ T cells, during Karp infection, but such responses were greatly attenuated during Gilliam infection. The robust cellular responses in Karp-infected B6 mice positively correlated with significantly early and high levels of serum cytokine/chemokine protein levels (CXCL1, CCL2/3/5, and G-CSF), as well as pulmonary gene expression (Cxcl1/2, Ccl2/3/4, and Ifng). In vitro infection of B6 mouse-derived primary macrophages also revealed bacterial strain-dependent immune gene expression profiles. This study provided the lines of evidence that highlighted differential tissue cellular responses against Karp vs. Gilliam infection, offering a framework for future investigation of Ot strain-related mechanisms of disease pathogenesis vs. infection control.

Brain transcriptomics reveal the activation of neuroinflammation pathways during acute Orientia tsutsugamushi infection in mice

Scrub typhus, an acute febrile illness caused by Orientia tsutsugamushi (Ot), is prevalent in endemic areas with one million new cases annually. Clinical observations suggest central nervous system (CNS) involvement in severe scrub typhus cases. Acute encephalitis syndrome (AES) associated with Ot infection is a major public health problem; however, the underlying mechanisms of neurological disorder remain poorly understood. By using a well-established murine model of severe scrub typhus and brain RNA-seq, we studied the brain transcriptome dynamics and identified the activated neuroinflammation pathways. Our data indicated a strong enrichment of several immune signaling and inflammation-related pathways at the onset of disease and prior to host death. The strongest upregulation of expression included genes involved in interferon (IFN) responses, defense response to bacteria, immunoglobulin-mediated immunity, IL-6/JAK-STAT signaling, and TNF signaling via NF-κB. We also found a significant increase in the expression of core genes related to blood-brain barrier (BBB) disruption and dysregulation in severe Ot infection. Brain tissue immunostaining and in vitro infection of microglia revealed microglial activation and proinflammatory cytokine production, suggesting a crucial role of microglia in neuroinflammation during scrub typhus. This study provides new insights into neuroinflammation in scrub typhus, highlighting the impact of excessive IFN responses, microglial activation, and BBB dysregulation on disease pathogenesis.

A case of acute encephalitis syndrome and cranial nerve palsy secondary to scrub typhus: A rare presentation from Western Nepal

Key Clinical Message

This case report highlights the importance of considering scrub typhus as a differential diagnosis for acute encephalitis with cranial nerve palsy in the region of the tsutsugamushi triangle.

Abstract

Scrub typhus is a zoonotic rickettsiosis caused by the bacterium Orientia tsutsugamushi. This disease is endemic to a region called the tsutsugamushi triangle that extends from Southeast Asia to the Pacific Ocean. We report a 17-year-old girl from western Nepal who presented with fever, headache, vomiting, and altered sensorium, as well as bilateral lateral rectus palsy, dysphagia, regurgitation of food, dysarthria, and left-sided upper motor neuron type facial palsy. Following laboratory and imaging tests, the patient was diagnosed with scrub typhus and was treated successfully with high-dose dexamethasone and doxycycline. This case highlights the importance of considering scrub typhus in the differential diagnosis of encephalitis with cranial nerve palsy, especially in the region of the tsutsugamushi triangle. It also emphasizes the need for timely diagnosis and treatment of scrub typhus to prevent the development of various complications and ensure earlier recovery of patients.

Rickettsia Deregulates Genes Coding for the Neurotoxic Cell Response Pathways in Cerebrocortical Neurons In Vitro

Rickettsial infections of the central nervous system (CNS) are manifested by severe neurological symptoms and represent a serious life-threatening condition. Despite the considerable health danger, only a few studies have been conducted focusing on the pathogenesis induced by Rickettsia sp. in CNS. To investigate the signaling pathways associated with the neurotoxic effects of rickettsiae, we employed an experimental model of cerebrocortical neurons combined with molecular profiling and comprehensive bioinformatic analysis. The cytopathic effect induced by Rickettsia akari and Rickettsia slovaca was demonstrated by decreased neuronal viability, structural changes in cell morphology, and extensive fragmentation of neurites in vitro. Targeted profiling revealed the deregulation of genes involved in the neuroinflammatory and neurotoxic cell response pathways. Although quantitative analysis showed differences in gene expression response, functional annotation revealed that the biological processes are largely shared between both Rickettsia species. The identified enriched pathways are associated with cytokine signaling, chemotaxis of immune cells, responses to infectious agents, interactions between neurons, endothelial and glial cells, and regulation of neuronal apoptotic processes. The findings of our study provide new insight into the etiopathogenesis of CNS infection and further expand the understanding of molecular signaling associated with neuroinvasive Rickettsia species.

Genomic bacterial load associated with bacterial genotypes and clinical characteristics in patients with scrub typhus in Hainan Island, Southern China

Scrub typhus, caused by mite-borne Orientia tsutsugamushi (O. tsutsugamushi), is a major febrile disease in the Asia-Pacific region. The DNA load of O. tsutsugamushi in the blood was previously found to be significantly higher in patients with fatal disease than those with non-fatal disease and correlated with the duration of illness, presence of eschar, and hepatic enzyme levels. In this prospective observation study, we analyzed the association of bacterial DNA load with clinical features, disease severity, and genotype using real-time PCR targeting the 56 kDa TSA gene of O. tsutsugamushi in the blood samples of 117 surviving patients with scrub typhus who had not received appropriate antibiotic treatment. The median O. tsutsugamushi DNA load was 3.11×103 copies/mL (range, 44 to 3.3×106 copies/mL). The severity of patients was categorized as mild, moderate, and severe based on the number of dysfunctional organs, and no significant difference in O. tsutsugamushi DNA load was found among these groups. Patients infected with the Karp group showed a significantly higher O. tsutsugamushi DNA load than those in the Gilliam (P < 0.05) and TA763 (P < 0.01) groups. Patients belonging to the Li ethnic group showed a significantly higher DNA load than those in the Han ethnic groups. The blood bacterial DNA load of patients showed no significant difference between groups divided by gender, age, with or without eschar, or the season of disease onset. The highest body temperature recorded during fever onset was positively correlated with O. tsutsugamushi DNA load (ρ  =  0.272, P  =  0.022). Correlation analyses indicated that the serum total bilirubin level was positively correlated with O. tsutsugamushi DNA load. In conclusion, the findings in this study demonstrated the association of DNA load of O. tsutsugamushi with the severity and genotype in patients with scrub typhus in Hainan, China.

Association of scrub typhus with incidence of dementia: a nationwide population-based cohort study in Korea

BACKGROUND

Scrub typhus is a mite-borne infectious rickettsial disease that can occur in rural and urban areas, with an especially high prevalence in older populations. This disease causes systemic vasculitis that can invade the central nervous system. Considering these characteristics, here we examined whether scrub typhus was associated with the occurrence of dementia, using large population-based cohort data.

METHOD

This population-based cohort study enrolled patients aged 60-89 years using data from the Health Insurance Review and Assessment database of South Korea between 2009 and 2018. We defined scrub typhus and dementia using International Classification of Diseases, Tenth Edition diagnostic codes. The control group was stratified according to age and sex at a ratio of 1:5 to the case group in the study population. The index date was set after 90 days beyond the date of the scrub typhus diagnosis, while the observation period was from the time of the index appointment to December 31, 2020. The primary outcome was newly diagnosed dementia. The secondary outcome was dementia classification, such as Alzheimer's disease, vascular dementia, and other. All analyses were conducted by matching age, gender, and comorbidity.

RESULTS

During the observation period, 10,460 of 71,047 (14.7%) people who had a history of scrub typhus versus 42,965 of 355,235 (12.1%) people in the control group, that is, with no history of scrub typhus, were diagnosed with dementia (adjusted hazard ratio, 1.12; 95% confidence interval, 1.10-1.15, p < 0.001). The Kaplan-Meier curves for time to cumulative incidence of dementia showed that the dementia incidence in both groups increased over time, while individuals with a past history of scrub typhus had a higher incidence of dementia than the control group. Second, the risk of Alzheimer's disease was significantly higher among patients with a history of scrub typhus (adjusted hazard ratio, 1.15; 95% confidence interval 1.13-1.18, p < 0.001).

CONCLUSION

In conclusion, a history of scrub typhus infection in old age is significantly associated with an increase in dementia, especially Alzheimer's disease. Our results suggest that prevention and appropriate treatment of scrub typhus should be emphasized as a dementia prevention measure.

Neurological manifestations of scrub typhus infection: A systematic review and meta-analysis of clinical features and case fatality

BACKGROUND

Scrub typhus has become a leading cause of central nervous system (CNS) infection in endemic regions. As a treatable condition, prompt recognition is vital. However, few studies have focused on describing the symptomology and outcomes of neurological scrub typhus infection. We conducted a systematic review and meta-analysis to report the clinical features and case fatality ratio (CFR) in patients with CNS scrub typhus infection.

METHODS

A search and analysis plan was published in PROSPERO [ID 328732]. A systematic search of PubMed and Scopus was performed and studies describing patients with CNS manifestations of proven scrub typhus infection were included. The outcomes studied were weighted pooled prevalence (WPP) of clinical features during illness and weighted CFR.

RESULTS

Nineteen studies with 1,221 (656 adults and 565 paediatric) patients were included. The most common clinical features in CNS scrub typhus were those consistent with non-specific acute encephalitis syndromes (AES), such as fever (WPP 100.0% [99.5%-100.0%, I2 = 47.8%]), altered sensorium (67.4% [54.9-78.8%, I2 = 93.3%]), headache (65.0% [51.5-77.6%, I2 = 95.1%]) and neck stiffness 56.6% (29.4-80.4%, I2 = 96.3%). Classical features of scrub typhus were infrequently identified; an eschar was found in only 20.8% (9.8%-34.3%, I2 = 95.4%) and lymphadenopathy in 24.1% (95% CI 11.8% - 38.9%, I2 = 87.8%). The pooled CFR (95% CI) was 3.6% (1.5%- 6.4%, I2 = 67.3%). Paediatric cohorts had a CFR of 6.1% (1.9-12.1%, I2 = 77%) whilst adult cohorts reported 2.6% (0.7-5.3%, I2 = 43%).

CONCLUSION

Our meta-analyses illustrate that 3.6% of patients with CNS manifestations of scrub typhus die. Clinicians should have a high index of suspicion for scrub typhus in patients presenting with AES in endemic regions and consider starting empiric treatment whilst awaiting results of investigations, even in the absence of classical signs such as an eschar or lymphadenopathy.

Rare neurological and neuropsychiatric manifestations of scrub typhus: a case series of 10 cases

INTRODUCTION

Scrub typhus is a potentially life-threatening but curable disease that can produce multi-organ failure. Neurological manifestations in scrub typhus have gained attention recently, where the entire neural axis except the myoneural junction can be involved. Although the pathogenesis of neurological involvement has not been established, immune-mediated mechanisms are suspected. This article reports the clinicopathological features of scrub typhus cases presenting several rare neurological and neuropsychiatric manifestations.

METHODS

Three hundred fifty-four serologically confirmed scrub typhus cases were admitted to the Department of General Medicine of Burdwan Medical College and Hospital (West Bengal, India) between May 2018 and May 2022. There were 50 patients who had predominantly neurological manifestations. Of these 50 cases, ten patients presented with extremely rare neurological manifestations.

RESULTS

We report 10 cases of scrub typhus (four men and six women) who presented with complex neurological pictures (posterior reversible encephalopathy syndrome, Opalski syndrome, parkinsonism, cerebellitis, isolated opsoclonus, acute transverse myelitis, myositis, polyradiculoneuropathy with cranial neuropathy, acute transient behavioral changes, and fibromyalgia). Immune-mediated mechanisms might have mediated the pathogenesis of most cases following scrub typhus infection.

CONCLUSION

From a clinicopathological point of view, each case was unique in its presentation and treatment response. In any acute onset neurological disorders associated with febrile illness in the tropics or subtropics, scrub typhus infection should be included in the differential diagnosis, despite the absence of eschar and unremarkable neuroimaging findings. This otherwise curable disease may result in multi-organ dysfunction syndrome and death if the diagnosis is delayed.

Acute demyelination of the medulla oblongata owing to scrub typhus in a 7-year-old boy: case report

ADEM: acute disseminated encephalomyelitis; CT: computed tomography; MRI: magnetic resonance imaging; PGCS: paediatric Glasgow coma scale; PICU: paediatric intensive care unit.

Profile of Scrub Typhus Meningitis/Meningoencephalitis in Children with and without Scrub Typhus IgM Antibody in CSF

The aim of this article was to study the spectrum of scrub typhus meningitis/meningoencephalitis (STM) cases in children. Children ≤14 years of age with acute undifferentiated febrile illness were included. Immunoglobulin M (IgM) enzyme-linked immunosorbent assay was done in blood and cerebrospinal fluid (CSF) of children with suspected STM. Demographic, clinical, and laboratory details were expressed as descriptive statistics. Factors associated with neurological involvement were identified on univariate analysis. A total of 76 children had ST during the study period (meningitis/meningoencephalitis = 8 [10.5%], of which 5 [62.5%] had detectable ST IgM antibodies in CSF). The included children were 4 to 12 years of age with boys > girls. Headache and vomiting were common in those with STM, whereas hyponatremia and thrombocytopenia were common in those without STM. All children with STM recovered with sequelae in one child (right lateral rectus palsy). There was no mortality. STM has an incidence of 10.5% in children with ST from Eastern India. Headache and vomiting were significant predictors of STM, whereas hyponatremia and thrombocytopenia were significant predictor of non-STM.

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.

Neurological facets of scrub typhus: A comprehensive narrative review

Scrub typhus is one of the most frequent causes of acute febrile illness in South and South-east Asian countries. Neurological features accompany 20% of scrub typhus infections, and may affect the central or peripheral nervous system, and sometime, may even occur in combination. Of late, its recognition among clinicians has increased with widening detection of its cutaneous hallmark, called eschar. Multiple mechanisms underlie neurological involvement, including direct invasion (meningitis, encephalitis), vasculitis (myositis) or immune-mediated mechanisms (opsoclonus, myoclonus, optic neuritis, Guillain–Barre syndrome). Despite an immunological basis for several neurological manifestations, response to doxycycline is remarkable, although immune therapy may be necessary for severe involvement. Scientific literature on scrub typhus neurology chiefly emanates from case reports, case series and small studies, and a comprehensive review is warranted to aid clinicians in recognising neurological involvement. This review aims at enriching this gap, and summarises clinical features, laboratory findings, and treatment options for various neurological facets of scrub typhus.