Orientia Tsutsugamushi Research Articles

An unusual presentation of scrub typhus with lateral rectus palsy in a child

Scrub typhus, an acute febrile infectious disease prevalent in the “Tsutsugamushi triangle”, is a mite-born rickettsial zoonosis, caused by Orientia tsutsugamushi. Although the clinical presentation is protean, it rarely causes abducens nerve palsy. We report a 13-year-old previously healthy Indian boy who presented with a recent onset right abducens nerve palsy, headache and fever but without the classic dermatological manifestation (“eschar”) of the disease. After exclusion of common infectious and other causes, he was finally diagnosed with scrub typhus associated with an abducens nerve palsy, which responded to doxycycline therapy.

Role of hinge motion and ATP dynamics in factors for inversion stimulation FIS protein deduced while targeting drug resistant Orientia tsutsugamushi

Orientia tsutsugamushi, the causative agent of scrub typhus has been found resistant to various classes of antibiotics such as penicillins, gentamycin and cephalosporins. Review of current literature suggests that the prevalence of scrub typhus has increased globally. Therefore, the current study has aimed at exploring the genome of O. tsutsugamushi to identify potential drug target proteins that can be used for developing novel antibiotics against the pathogen. Subtractive proteomics approach has revealed FIS as a potential drug target protein involved in two component system (TCS), a signaling pathway crucial for bacteria to survive and adjust in changing environmental conditions. Molecular docking studies have revealed compound-356 (CHEMBRIDGE-10040641-3710.356) as a potential inhibitor in both chains A and B of the FIS protein. Simulation results suggest that the docked complex has remained stable and compact throughout the 200 ns run. Significant conformational changes including the hinge motion was observed in the DNA binding domain. Furthermore, the presence of salt bridge between GLU910 and ARG417, rearrangement of interaction residues and displacement of ATP in the central AAA + domain upon binding to the inhibitor were also observed playing a role in stabilizing the protein structure.

A STUDY OF CARDIAC MANIFESTATIONS IN SCRUB TYPHUS FEVER

This work was about spotted fever, a rickettsiosis infection caused by Orientia Tsutsugamushi. The purpose of the study was to compare the outcomes of typhus patients with and without myocarditis and to examine the spectrum of cardiac manifestations in typhus infection in Eastern Medical School and Hospital, Ragolu, Srikakulam, Andra Pradesh and the study was carried out at 81 patients performed. Simple descriptive statistical analyzers are used as materials and methods. Cardiovascular manifestations were assessed using cardiac biomarkers, electrocardiogram and echocardiogram. The development of myocarditis increased the need for ventilation, increased the duration of the intensive care unit and hospitalization. Myocarditis was not associated with worse mortality in our cohort

Urine Metabolite of Mice with Orientia tsutsugamushi Infection.

Scrub typhus is an acute febrile, mite-borne disease endemic to the Asia-Pacific region. In South Korea, it is a seasonal disease that occurs frequently in the autumn, and its incidence has increased steadily. In this study, we used a liquid chromatography and flow injection analysis-tandem mass spectrometry-based targeted urine metabolomics approach to evaluate the host response to Orientia tsutsugamushi infection. Balb/c mice were infected with O. tsutsugamushi Boryong, and their urine metabolite profile was examined. Metabolites that differed significantly between the experimental groups were identified using the Kruskal-Wallis test. Sixty-five differential metabolites were identified. The principal metabolite classes were acylcarnitines, glycerophospholipids, biogenic amines, and amino acids. An ingenuity pathway analysis revealed that several toxic (cardiotoxic, hepatotoxic, and nephrotoxic) metabolites are induced by scrub typhus infection. This is the first report of urinary metabolite biomarkers of scrub typhus infection and it enhances our understanding of the metabolic pathways involved.

Molecular Surveillance for Vector-Borne Bacteria in Rodents and Tree Shrews of Peninsular Malaysia Oil Palm Plantations

Many human clinical cases attributed to vector-borne pathogens are underreported in Malaysia, especially in rural localities where healthcare infrastructures are lacking. Here, 217 small mammals, consisting of rodents and tree shrews, were trapped in oil palm plantations in the Peninsular Malaysia states of Johor and Perak. Species identification was performed using morphological and DNA barcoding analyses, and 203 small mammals were included in the detection of selected vector-borne bacteria. The DNA extracted from the spleens was examined for Orientia tsutsugamushi, Borrelia spp., Bartonella spp. and Rickettsia spp. using established PCR assays. The small mammals collected in this study included Rattus tanezumi R3 mitotype (n = 113), Rattus argentiventer (n = 24), Rattus tiomanicus (n = 22), Rattus exulans (n = 17), Rattus tanezumi sensu stricto (n = 1) and Tupaia glis (n = 40). Orientia tsutsugamushi, Borrelia spp. and Bartonella phoceensis were detected in the small mammals with the respective detection rates of 12.3%, 5.9% and 4.9%. Rickettsia spp., however, was not detected. This study encountered the presence of both Lyme disease and relapsing fever-related borreliae in small mammals collected from the oil palm plantation study sites. All three microorganisms (Orientia tsutsugamushi, Borrelia spp. and Bartonella phoceensis) were detected in the R. tanezumi R3 mitotype, suggesting that the species is a competent host for multiple microorganisms. Further investigations are warranted to elucidate the relationships between the ectoparasites, the small mammals and the respective pathogens.

Orientia tsutsugamushi Infection in Wild Small Mammals in Western Yunnan Province, China

Small mammals can transmit and serve as a reservoir for Orientia tsutsugamushi (Ot) in nature by carrying infected mites. In Yunnan, one of China's main foci of scrub typhus, etiological evidence and genetic diversity for Ot is limited. A total of 2538 small mammals were captured seasonally from 2015 to 2016 in the three counties of Yunnan, and the spleen or liver tissue was examined for Ot based on 56 kDa nPCR. The overall prevalence of Ot was 1.77%, ranging from 0.26 to 9.09% across different species. The Gilliam strain was found in 35.6% (16/45) of the wild small mammals, followed by the Karp 11.1% (5/45) and TA763 (1/45) strains, the last of which was discovered in western Yunnan for the first time. In Lianghe, Ot infection rates in wild small mammals were higher than in the other two counties. The infection rates of Eothenomys miletus with Ot were highest in the three dominant species. Ot infection rates in wild small mammals were higher in Lianghe (1200-1400 m) and Yulong (2800-3000 m). These findings could provide research clues for further confirmation of scrub typhus foci in western Yunnan or other similar natural environments.

A Rare Presentation of Scrub Typhus: Multi-Organ Dysfunction [Acute Kidney Injury, Hepatitis] and Acute Respiratory Distress Syndrome

Scrub typhus is an acute febrile illness caused by Orientia tsutsugamushi- a gram negative intracellular bacilli. It typically manifests as eschar formation, fever, rash, myalgia and diffuse lymphadenopathy. The clinical severity of scrub typhus ranges from mild fever to a lethal outcome. Complications like sepsis, acute respiratory distress syndrome (ARDS) and multi organ dysfunction syndrome (MODS)--hepatitis, acute kidney injury contribute to the higher mortality rates, which range from 7-30% in untreated cases. Here, we report a case of 35 years old male who presented with complaints of fever, headache, generalised abdominal pain and dry cough for 7 days. The patient was tested positive for Scrub Typhus IgM antibody; and was complicated with MODS- AKI, Hepatitis and ARDS. After extensive intensive care, monitoring and treatment of 15-20 days, the patient recovered. Hence, early diagnosis and prompt treatment aids in decreasing the mortality in such cases.

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.

Efficacy of Oral Doxycycline versus Intravenous Doxycycline for the Treatment of Uncomplicated Scrub Typhus in Children: A Prospective Interventional Study

Introduction: Orientia tsutsugamushi causes acute febrile illness known as scrub typhus, which is spread by the bite of the trombiculid mite. Doxycycline is the first-line treatment for clinically diagnosed cases of scrub typhus. If not diagnosed and treated early, it can lead to complications such as acute renal failure, meningoencephalitis, gastrointestinal bleeding, and multiple organ failure. However, there have been no trials comparing the effectiveness of oral and Intravenous (i.v.) doxycycline for scrub typhus treatment. Aim: To assess the efficacy of intravenous versus oral doxycycline in managing uncomplicated scrub typhus. Materials and Methods: This prospective interventional research was conducted in the Paediatrics Department at Maharajah’s Institute of Medical Sciences, Vizianagaram, India, from June 2021 to July 2022. Out of a total of 178 children diagnosed with scrub typhus during the study period, 102 children who received either oral or intravenous doxycycline as monotherapy were included. The primary outcome measures studied were the incidence of delayed defervescence and the time of defervescence. The t-test or Mann-Whitney test was applied for continuous data, and the Chi-square test or Fischer’s-exact test was used to compare dichotomous variables. Results: The mean age of children treated with oral doxycycline was 9.5±2.7 years and with i.v. doxycycline was 8.2±2.4 years. Among the 178 children diagnosed with scrub typhus, 102 (57.3%) children treated with doxycycline alone were included in the study. Out of these, 78 (76.4%) cases received oral doxycycline, while 28 (27.4%) cases received intravenous doxycycline. There was no statistically significant difference in the response rate between the two groups. The p-value for time to defervescence was 0.672, and the p-value for the incidence of delayed defervescence was 0.9845. Conclusion: Both oral and intravenous forms of doxycycline demonstrated similar efficacy in the treatment of scrub typhus. Nearly all children in both groups became afebrile within 72 hours after starting treatment.

Intranasal Immunization With Nanoparticles Containing an Orientia tsutsugamushi Protein Vaccine Candidate and a Polysorbitol Transporter Adjuvant Enhances Both Humoral and Cellular Immune Responses.

Scrub typhus, a mite-borne infectious disease, is caused by Orientia tsutsugamushi. Despite many attempts to develop a protective strategy, an effective preventive vaccine has not been developed. The identification of appropriate Ags that cover diverse antigenic strains and provide long-lasting immunity is a fundamental challenge in the development of a scrub typhus vaccine. We investigated whether this limitation could be overcome by harnessing the nanoparticle-forming polysorbitol transporter (PST) for an O. tsutsugamushi vaccine strategy. Two target proteins, 56-kDa type-specific Ag (TSA56) and surface cell Ag A (ScaA) were used as vaccine candidates. PST formed stable nano-size complexes with TSA56 (TSA56-PST) and ScaA (ScaA-PST); neither exhibited cytotoxicity. The formation of Ag-specific IgG2a, IgG2b, and IgA in mice was enhanced by intranasal vaccination with TSA56-PST or ScaA-PST. The vaccines containing PST induced Ag-specific proliferation of CD8+ and CD4+ T cells. Furthermore, the vaccines containing PST improved the mouse survival against O. tsutsugamushi infection. Collectively, the present study indicated that PST could enhance both Ag-specific humoral immunity and T cell response, which are essential to effectively confer protective immunity against O. tsutsugamushi infection. These findings suggest that PST has potential for use in an intranasal vaccination strategy.

A Case Series of Scrub Meningoencephalitis from a Tertiary Care Center in North India

Abstract Scrub typhus infection is reemerging leading cause of acute febrile illnesses in post-rainy or monsoon season in Southeast Asia. It is caused by Orientia tsutsugamushi and spread by the bite of chiggers, larval forms of trombiculid mites. The clinical picture can range from simple acute febrile illness to multiorgan dysfunction. Neurological manifestations also vary from aseptic meningitis, meningoencephalitis, cerebral infarction, acute disseminated encephalomyelitis, transverse myelitis, and psychiatric manifestations. Here, we present a case series of eight cases of scrub meningoencephalitis diagnosed based on clinical, laboratory, and radiological criteria.

Prevalence and heterogeneity of antibiotic resistance genes in Orientia tsutsugamushi and other rickettsial genomes

Despite a million infections every year and an estimated one billion people at risk, scrub typhus is regarded as a neglected tropical disease. The causative bacterium Orientia tsutsugamushi, a member of rickettsiae, seems to be intrinsically resistant to several classes of antibiotics. The emergence of antibiotic-resistant scrub typhus is likely to become a global public health concern. Yet, it is unknown as to how common antibiotic resistance genes are in O. tsutsugamushi, and how variable these loci are among the genomes of rickettsiae. By using the comprehensive antibiotic resistance database, we explored 79 complete genomes from 24 species of rickettsiae for antibiotic resistance loci. There were 244 unique antibiotic resistance genes in rickettsiae. Both the total and unique antibiotic resistance genes in O. tsutsugamushi were significantly less compared to other members of rickettsiae. However, antibiotic resistance genes in O. tsutsugamushi genomes were more unique and highly variable. Many genes such as resistant variants of evgS, and vanS A/G were present in numerous copies. These results will have important implications in the context of antibiotic-resistant scrub typhus.

Neonatal Scrub TyphusA Series of Five Cases

Scrub typhus is a rickettsial infection caused by Orientia tsutsugamushi. This is transmitted by trombiculid mite called chiggers. A number of cases of scrub typhus are being reported from North India. However, there has been a steady increase in the number of cases from Southern India, especially Tamil Nadu, Kerala, and Karnataka. The manifestation of the disease is due to the vasculitis and perivasculitic involvement. This vasculitis is responsible for oedema, skin rash and end organ ischaemic injury. A skin lesion called eschar is pathognomic of this condition, which is present in 40% of the cases. It is a close differential diagnosis for other common infectious diseases like- dengue fever, malaria, enteric fever and severe sepsis. Scrub typhus is rare in neonates. Herewith, the authors reported five cases of neonatal scrub typhus with varied clinical manifestations. All the five neonates (2 females and 3 males) had fever and high C-reactive Protein (CRP), two had hepatosplenomegaly, two presented with shock, one had paralytic ileus, one baby had features of aseptic meningitis and one had pericardial and pleural effusion. Two out of five babies had an eschar, which is pathognomonic of scrub typhus.Three babies were treated with doxycycline and two babies required Intravenous (i.v.) azithromycin. All of them recovered completely, except one baby, who succumbed to the illness. A high index of suspicion is required to diagnose scrub typhus in neonates early.Timely intervention will prevent morbidity and mortality.

Doxycycline-resistant Scrub Typhus in a Syndromic Child

Scrub Typhus, a human febrile illness caused by Orientia tsutsugamushi, is common in Asia and infects persons those visiting the endemic areas. Scrub typhus is a zoonotic infection. It is transmitted by a trombiculid mite which introduces the bacteria by its bite. Scrub typhus is associated with maculopapular rashes and local and/or generalised lymphadenopathy.It is characterised by eschar at the site of the bite. A child with doxycycline-resistant scrub typhus is being presented here. A 10-year-old female child was bought to the hospital with complaints of fever for six days, cough for three days, loose stools for two days, and vomiting for one day duration. S1 and S2 sounds were heard while bilateral vesicular breath sounds were normal. There was no hepatosplenomegaly and Central Nervous System (CNS) examination showed no focal neurologic deficits. Investigations showed a normal leukocyte count and Differential Leucocyte Count (DLC), microcytic hypochromic anaemia, thrombocytopenia, hyponatremia, and elevated liver enzymes. Scrub Immunoglobulin M (IgM) was positive. Chest radiograph showed a bell-shaped chest with vertical straightening of ribs. The child was started on intravenous (i.v.) fluids, Doxycycline 4 mg/kg, and paracetamol. The child continued to spike fever at day 6 of Doxycycline and hence was started on Azithromycin 10 mg/kg, following which the fever subsided and the child was discharged.

Current status of mites and mite-borne diseases in India.

Mites act as the vectors of zoonotic vector-borne disease scrub typhus caused by the rickettsial pathogen Orientia tsutsugamushi. In India, scrub typhus is transmitted by the mite Leptotrombidium deliense. Rodents are the reservoirs and support the spread of this disease. Sarcoptes scabiei or the itch mite is causing scabies which is a common skin infection in India. Dermatitis, trombiculosis, and mite dust allergy are common mite-borne diseases transmitted by Pyemotidae family. D. brevis folliculorum and Demodex brevis are two major mite species found on humans also causing a disease; "Demodicosis", common in India. Dermanyssus gallinae, fowl mite causes pruritis in poultry birds, transmits infections to poultry workers when they come into contact with birds. There is a re-emergence of mite-borne diseases, especially scrub typhus, in many parts of India requiring urgent attention for its control. This review is aimed to update the available information on mites and mite transmitted diseases prevalent in India to highlight the importance of rodent and chigger mite vector control to prevent forthcoming mite-borne diseases in India.

Orientia tsutsugamushi Infection Stimulates Syk-Dependent Responses and Innate Cytosolic Defenses in Macrophages.

Orientia tsutsugamushi is an obligately intracellular bacterium and an etiological agent of scrub typhus. Human studies and animal models of scrub typhus have shown robust type 1-skewed proinflammatory responses during severe infection. Macrophages (MΦ) play a critical role in initiating such responses, yet mechanisms of innate recognition for O. tsutsugamushi remain unclear. In this study, we investigated whether Syk-dependent C-type lectin receptors (CLRs) contribute to innate immune recognition and the generation of proinflammatory responses. To validate the role of CLRs in scrub typhus, we infected murine bone marrow-derived MΦ with O. tsutsugamushi in the presence of selective Syk inhibitors and analyzed a panel of CLRs and proinflammatory markers via qRT-PCR. We found that Mincle/Clec4a and Clec5a transcription was significantly abrogated upon Syk inhibition at 6 h of infection. The effect of Syk inhibition on Mincle protein expression was validated via Western blot. Syk-inhibited MΦ had diminished expression of type 1 cytokines/chemokines (Il12p40, Tnf, Il27p28, Cxcl1) during infection. Additionally, expression of innate immune cytosolic sensors (Mx1 and Oas1-3) was highly induced in the brain of lethally infected mice. We established that Mx1 and Oas1 expression was reduced in Syk-inhibited MΦ, while Oas2, Oas3, and MerTK were not sensitive to Syk inhibition. This study reveals that Syk-dependent CLRs contribute to inflammatory responses against O. tsutsugamushi. It also provides the first evidence for Syk-dependent activation of intracellular defenses during infection, suggesting a role of pattern recognition receptor crosstalk in orchestrating macrophage-mediated responses to this poorly studied bacterium.

A Use of 56-kDa Recombinant Protein of Orientia tsutsugamushi Karp Serotype in Serodiagnosis of Scrub Typhus by Enzyme-Linked Immunosorbent Assay in Thais.

Scrub typhus is a mite-borne disease caused by a Gram-negative obligately intracellular bacillus, Orientia tsutsugamushi. The disease is endemic in the Asia-Australia-Pacific region, including Thailand. Scrub typhus generally manifests as acute undifferentiated febrile fever along with myalgia, rash, and lymphadenopathy. An eschar can be a valuable diagnostic clue, but this skin lesion may be missed in some patients. The disease symptoms resemble those of other febrile illnesses such as leptospirosis, typhoid, murine typhus, malaria, and dengue fever, making a laboratory diagnosis necessary for the definitive diagnosis. In this study, we expressed a recombinant protein derived from 56-kDa type-specific antigen of O. tsutsugamushi Karp serotype and tested its ability to detect and differentiate scrub typhus infection. IgM and IgG antibodies were determined in sera from scrub typhus (n = 92) and other febrile illness patients (murine typhus (n = 25), melioidosis (n = 36), leptospirosis (n = 42), and dengue (n = 35)) from Thailand. Sensitivities of 87.0% and 59.8% with a specified assay cut-off were obtained for IgM and IgG indirect ELISAs, respectively, with a specificity of 100% in both tests. The sensitivity was increased to 95.7% when a combination of IgM and IgG ELISAs results was considered. Our study suggested a potential of the 56-kDa recombinant protein for further development and evaluation for use in scrub typhus serodiagnosis.

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

ObjectivesScrub 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. MethodsPatients (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. ResultsIn 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. ConclusionWe 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.

CCR7/dendritic cell axis mediates early bacterial dissemination in Orientia tsutsugamushi-infected mice.

Scrub typhus is a life-threatening zoonosis caused by the obligate intracellular bacterium Orientia tsutsugamushi (Ot) that is transmitted by the infected larvae of trombiculid mites. However, the mechanism by which Ot disseminates from the bite site to visceral organs remains unclear; host innate immunity against bacterial dissemination and replication during early infection is poorly understood. In this study, by using an intradermal infection mouse model and fluorescent probe-labeled Ot, we assessed the dynamic pattern of innate immune cell responses at the inoculation site. We found that neutrophils were the first responders to Ot infection and migrated into the skin for bacterial uptake. Ot infection greatly induced neutrophil activation, and Ot-neutrophil interaction remarkably promoted cell death both in vitro and in vivo. Depletion of neutrophils did not alter bacterial dissemination in mice, as evidenced by similar bacterial burdens in the skin and draining lymph nodes (dLN) at day 3, as well as in the lungs and brains at day 14, as compared to the control mice. Instead, dendritic cells (DCs) and macrophages played a role as a Trojan horse and transmitted Ot from the skin into dLN. Importantly, the absence of homing receptor CCR7 or neutralization of its ligand, CCL21, significantly impaired DC migration, resulting in reduced bacterial burdens in dLN. Taken together, our study sheds light on a CCR7/dendritic cell-mediated mechanism of early Ot dissemination and provides new insights into therapeutic and vaccine development strategies for scrub typhus.

Expression of Concern: Orientia tsutsugamushi Stimulates an Original Gene Expression Program in Monocytes: Relationship with Gene Expression in Patients with Scrub Typhus.

Expression of Concern: Orientia tsutsugamushi Stimulates an Original Gene Expression Program in Monocytes: Relationship with Gene Expression in Patients with Scrub Typhus.