Diagnosis of scrub typhus

An immunochromatographic test for serological diagnosis of scrub typhus

A fluorescent immunochromatographic test (FM-ICT) was developed for rapid detection of anti-Orientia tsutsugamushi antibodies in serum samples. The FM-ICT was constructed based on the dual-antigen sandwich method. Truncated 56 kDa outer membrane protein of O. tsutsugamushi strain SJ, was expressed in E. coli and mixed with those of Ptan and Gillam strains. A thin line of the protein mixture was precisely sprayed across a nitrocellulose membrane making this the "Test" line. Polyclonal antibodies (pAbs) to O.tsutsugamushi were sprayed in another line across the membrane making this the "Control" line. Fluorescent microspheres conjugated 56 kDa proteins reacting with sample serum will be captured on the "Test" line if the sample contains antibodies to O.tsutsugamushi. Several experimental parameters were optimized. After optimizing the reaction procedure, the results are visible, within 6 min, with the naked eye under ultraviolet light. The limit of detection (LOD) was determined to be 7.63 ng/mL with prepared polyclonal antibodies. No cross-reaction was observed with sera samples from other febrile diseases. In clinical evaluations, the strips showed 94.92% sensitivity (106/112) and 93.75% specificity (56/60). The FM-ICT we developed will provide a new tool for on-site diagnosis of scrub typhus.

A seminested recombinase polymerase amplification assay to detect rickettsial pathogens in clinical samples

Treatment at the early stage of onset is vital for the prognosis of rickettsioses. But the absence of specific clinical symptoms complicates the diagnosis of this condition. Herein we established a seminested recombinase polymerase amplification assay (snRPA-nfo) that enables quick detection and differentiation of rickettsial pathogens in clinical samples with high sensitivity and specificity. The conserved 17-kDa protein gene of Rickettsia sibirica and the 47-kDa protein gene of Orientia tsutsugamushi were targeted for the duplex RPA-nfo assay. The snRPA-nfo assay exhibited an increased LOD in spiked blood samples, up to 1000-fold in comparison to standard RPA-nfo, and a better detection rate (83.3%, 5/6) than TaqMan PCR (16.6%, 1/6, Ct ≤ 35) in clinically confirmed patient blood samples. Thus, snRPA-nfo assay represents a promising alternative to TaqMan PCR in the early diagnosis of rickettsioses for point-of-care testing as well as in resource-limited settings.

The Prevalence of Rodents Orientia tsutsugamushi in China During Two Decades: A Systematic Review and Meta-Analysis

Background: Orientia tsutsugamushi is a zoonotic intracellular pathogen that requires parasitism in eukaryotic cells to reproduce. In recent years, tsutsugamushi disease reported in many places nationwide has crossed the Yangtze River, continuously, spreading to the North China. Now this phenomenon has aroused people's attention. Materials and Methods: In this study, meta-analysis was used to analyze the infection of rodents (vectors) in China, to clarify the transmission rule of O. tsutsugamushi. Results: This study included literature from six databases (PubMed, Web of Science, Science Direct, Wanfang, CNKI, and VIP). A total of 55 articles were included in the study from 610 retrieved articles. The total infection rate of O. tsutsugamushi in rodents was 5.5% (1206/20,620, 95% confidence interval [CI]: 0.0553-0.0617). The prevalence of O. tsutsugamushi in rodents before 2013 (7.73%, 95% CI: 4.11-12.37) was higher than after 2013 (2.11%, 95% CI: 0.64-4.41). O. tsutsugamushi spread among a variety of rodents, among which Rattus losea (13.3%, 95% CI: 4.33-26.26), Rattus tanezumi (5.69%, 95% CI: 1.37-12.72), and Apodemus agrarius (5.32%, 95% CI: 2.26-9.58) infection rate was higher. Kawasaki (8.32%, 95% CI: 1.42-20.17), Karp (7.36%, 95% CI: 2.62-14.22), Kato (2.54%, 95% CI: 0.08-8.28), and Gilliam (2.13%, 95% CI: 0.42-5.09) were the main prevalent genotypes in China. The prevalence of O. tsutsugamushi in rodents was seasonal, increasing gradually in summer (2.39%, 95% CI: 0.46-5.77), peaking in autumn (4.59%, 95% CI: 1.15-10.16), and then declining. The positive rate of immunofluorescence assay (25.07%, 95% CI: 8.44-46.88) was the highest among the detection methods, and it was statistically significant (p < 0.05). Based on the subgroup of geographical factors and climatic factors, the probability of O. tsutsugamushi infection in rodents was the highest when the temperature >19℃ (8.20%, 95% CI: 1.22-20.52), the altitude <100 millimeters (7.23%, 95% CI: 3.45-12.26), the precipitation >700 millimeters (12.22%, 95% CI: 6.45-19.50), and the humidity 60-70% (7.80%, 95% CI: 4.17-12.44). Conclusions: Studies have shown that rodents carrying O. tsutsugamushi are common. People should prevent and control rodents in life and monitor rodents carrying O. tsutsugamushi for a long time.

An alarming surge of scrub typhus cases presenting as acute encephalitis in children

Scrub typhus, which is prevalent in the Asia Pacific region is most feared owing to its life-threatening neurological complications. We present four cases of scrub typhus with acute encephalitis, including one with multiorgan failure and another serologically proven co-infection with Hepatitis C. Treatment of scrub typhus is not, however, so difficult, so its early diagnosis is paramount.

A rare case of severe leptospirosis infection presenting as septic shock in a non-endemic area: a case report and literature review

BACKGROUND

Leptospirosis is a zoonosis caused by spirochete "genus" leptospira. The clinical presentations of leptospirosis range from an influenza-like presentation of fever and myalgia, to severe forms. Leptospirosis can potentially lead to a misdiagnosis or delay in diagnosis when clinical similarities exist.

CASE PRESENTATION

A 63-year-old man presented with fever, shock and thrombocytopenia followed by diffuse pulmonary hemorrhage. Peripheral blood Metagenomic Next-generation Sequencing (mNGS) reported Leptospira interrogans. The patient was treated with piperacillin-tazobactam (TZP) plus doxycycline and improved dramatically after 7 days.

CONCLUSION

We conclude that leptospirosis can potentially lead to a misdiagnosis or delay in diagnosis. Correctly evaluation of thrombocytopenia in acute febrile illnesses facilitates the differential diagnosis of leptospirosis. mNGS can accurately detect Leptospira DNA during the early stage of the infection.

Leukocytoclastic Vasculitis: A peculiar presentation of scrub typhus

Scrub typhus is a disease endemic to the Indian subcontinent caused by the obligate intracellular pleomorphic organism, Orientia tsutsugamushi. Scrub typhus, among other acute febrile illnesses, manifests as prodromal symptoms of fever, malaise, myalgia and anorexia followed by a distinct maculopapular rash, hepatosplenomegaly and lymphadenopathy. We report the case of a patient presenting to tertiary care hospital in southern India in 2021 who developed a rare cutaneous vasculitis secondary to infection with Orientia tsutsugamushi. After performing the Weil-Felix test, a diagnostic titre of >1:640 against OXK was obtained. Furthermore, a skin biopsy was carried out which confirmed the diagnosis of leukocytoclastic vasculitis. The patient was treated with doxycycline and showed drastic improvement in his symptoms.

A potential tool for predicting epidemic trends and outbreaks of scrub typhus based on Internet search big data analysis in Yunnan Province, China

Introduction

Scrub typhus, caused by Orientia tsutsugamushi, is a neglected tropical disease. The southern part of China is considered an important epidemic and conserved area of scrub typhus. Although a surveillance system has been established, the surveillance of scrub typhus is typically delayed or incomplete and cannot predict trends in morbidity. Internet search data intuitively expose the public's attention to certain diseases when used in the public health area, thus reflecting the prevalence of the diseases.

Methods

In this study, based on the Internet search big data and historical scrub typhus incidence data in Yunnan Province of China, the autoregressive integrated moving average (ARIMA) model and ARIMA with external variables (ARIMAX) model were constructed and compared to predict the scrub typhus incidence.

Results

The results showed that the ARIMAX model produced a better outcome than the ARIMA model evaluated by various indexes and comparisons with the actual data.

Conclusions

The study demonstrates that Internet search big data can enhance the traditional surveillance system in monitoring and predicting the prevalence of scrub typhus and provides a potential tool for monitoring epidemic trends of scrub typhus and early warning of its outbreaks.

Evaluation of the Therapeutic Effect of Antibiotics on Scrub Typhus: A Systematic Review and Network Meta-Analysis

Background

To explore the efficacy and safety of drugs in patients with scrub typhus.

Methods

For this systematic review and network meta-analysis, we searched PubMed, Embase, Web of Science, Cochrane Central Register of Clinical Trials, China National Knowledge Infrastructure (CNKI), and Wanfang data (WF) up to December 2021. All randomized controlled trials (RCTs) of antibiotics used to treat scrub typhus were included without language or date restrictions. The overall effectiveness was evaluated from 4 perspectives: cure rate (CR), defervescence time (DT), gastrointestinal symptoms–adverse events (GS-AD), and abnormal blood count–adverse events (ABC-AD). The quality of evidence was evaluated using the Cochrane Risk of Bias tool and GRADE system.

Results

Sixteen studies involving 1,582 patients were included to evaluate 7 drugs, namely, azithromycin, doxycycline, chloramphenicol, tetracycline, rifampin, moxifloxacin, and telithromycin. In this network meta-analysis, rifampicin (82%) and chloramphenicol (65%) were more effective in terms of CR, and moxifloxacin (3%) from the quinolone family was the worst. Azithromycin caused the fewest events in terms of ABC-AD. No differences were found in this network meta-analysis (NMA) in terms of DT and GS-AD.

Conclusions

Rifampicin was associated with the highest CR benefit and the lowest risk of DT when used to treat patients with scrub typhus, except in areas where tuberculosis (TB) was endemic. Azithromycin was found to be better in CR and was associated with a lower probability of GS-AD and ABC-AD; therefore, it may be considered to treat pregnant women and children. Moxifloxacin had a much lower CR than other drugs and is, therefore, not recommended for the management of scrub typhus.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/, identifier: CRD42021287837.

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.

Scrub typhus meningoencephalitis presenting as opsoclonus myoclonus syndrome: A video-based case

Opsoclonus myoclonus syndrome secondary to scrub typhus infection is a rare clinical entity. Hence, it is important to know its clinical manifestations and complications, so that it can be properly managed. We report a 28-year-old female whose initial manifestation was only fever, which subsided in four days. Two days later, she developed opsoclonus myoclonus syndrome. This was managed with doxycycline and clonazepam, but as it persisted, intravenous immunoglobulin was added. She showed excellent response to treatment.

Epidemiologic Changes of Scrub Typhus in China, 1952-2016

Scrub typhus, a miteborne rickettsiosis, has emerged in many areas globally. We analyzed the incidence and spatial–temporal distribution of scrub typhus in China during 1952–1989 and 2006–2016 using national disease surveillance data. A total of 133,623 cases and 174 deaths were recorded. The average annual incidence was 0.13 cases/100,000 population during 1952–1989; incidence increased sharply from 0.09/100,000 population in 2006 to 1.60/100,000 population in 2016. The disease, historically endemic to southern China, has expanded to all the provinces across both rural and urban areas. We identified 3 distinct seasonal patterns nationwide; infections peaked in summer in the southwest, summer-autumn in the southeast, and autumn in the middle-east. Persons >40 years of age and in nonfarming occupations had a higher risk for death. The changing epidemiology of scrub typhus in China warrants an enhanced disease control and prevention program.

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.

Rickettsioses in Children - A Review

Rickettsial diseases, caused by a variety of obligate intracellular, Gram-negative bacteria from the genera Rickettsia, Orientia, Ehrlichia, Neorickettsia, Neoehrlichia, and Anaplasma are considered some of the most covert emerging and re-emerging diseases. Scrub typhus, murine flea-borne typhus and Indian tick typhus are commonly being reported and during the last decade. Scrub typhus (ST) has emerged as a serious public health problem in India. Rickettsial infections are generally incapacitating and difficult to diagnose; untreated cases have case fatality rates as high as 30-45% with multiple organ dysfunction, if the specific treatment is delayed. Early clinical suspicion, timely diagnosis followed by institution of specific antimicrobial therapy shortens the course of the disease, lowers the risk of complications and reduces morbidity and mortality due to rickettsial diseases. Still there is large gap in our knowledge of Rickettsioses and the vast variability and non-specific presentation of these have often made it difficult to diagnose clinically. The present review describes the epidemiology, clinical manifestations, diagnostic modalities and treatment of Scrub typhus which is a vastly underdiagnosed entity and clinicians should suspect and test for the disease more often.

Diagnosis of scrub typhus: recent advancements and challenges

Scrub typhus is a mite-borne, acute febrile illness caused by the bacterium Orientia tsutsugamushi. It is a re-emerging infectious disease of the tsutsugamushi triangle. Scrub typhus is transmitted through bites of contaminated chiggers (larval stage). Diagnosis of scrub typhus is challenging as its symptoms mimic with other acute febrile illnesses. Several methods are effectual for diagnosis of scrub typhus that includes enzyme-linked immunosorbent assay (ELISA), immunofluorescence assay (IFA), immunochromatographic test (ICT), Weil-Felix, polymerase chain reaction (PCR) and loop-mediated isothermal amplification (LAMP). Weil-Felix test was initially used for the diagnosis of scrub typhus in underdeveloped countries but not preferred due to a lack of both specificity and sensitivity. Other immuno-based methods like IFA and ELISA are most outrank for detection of scrub typhus due to their higher sensitivity and specificity, but not vigorous to lay bare the infection at early stages and need the convalescent sampling for verification of positive samples. On another deed, PCR based methods becoming acceptable over era due to its dexterity of early-stage diagnosis with higher specificity and sensitivity but lack its applicability in circumstances of scrub typhus due to the variegated genetic makeup of Orientia tsutsugamushi among its serotypes. The present review focused on various detection methods along with their advantages and disadvantages used in the diagnosis of scrub typhus. A comparison between available methods of diagnosis with challenges in the detection of scrub typhus is also summarized.

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

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

Comparison of nested polymerase chain reaction and real-time polymerase chain reaction targeting 47kda gene for the diagnosis of scrub typhus

Introduction

Scrub typhus is a zoonotic infection caused by Orientia tsutsugamushi which is transmitted by Leptotrombidium mites. The disease manifests as a mild-to-severe illness with non-specific clinical symptoms. Rapid diagnosis and prompt treatment are essential for patient management. Both serological and molecular methods are used for the diagnosis of scrub typhus. The present study assessed the usefulness of detection of the gene encoding the 47kDa outer-membrane protein (OMP) for the laboratory diagnosis of scrub typhus.

Materials and Methods

Nested polymerase chain reaction (nPCR) and real-time PCR targeting 47 kDa OMP antigen gene of O. tsutsugamushi were performed on ethylenediaminetetraacetic acid blood samples.

Results

Six of the 103 (5.8%) patients showed the presence of 47kDa gene by nPCR. Seventy of 103 (67.9%) cases showed the presence of 47kDa gene by qPCR. Among the 70 positive cases, the majority of them were females (40/70, 57.1%). The highest number of positive cases was observed during October-February.

Conclusion

Real-time PCR targeting O. tsutsugamushi-specific 47-kDa gene is more sensitive than nPCR and may be the assay of choice for the detection of the organism in patients with suspected scrub typhus.

Development of multiplex PCR for neglected infectious diseases

Scrub typhus, murine typhus, and leptospirosis are widely neglected infectious diseases caused by Orientia tsutsugamushi, Rickettsia typhi, and pathogenic Leptospira spp., respectively. Patients usually present with non-specific symptoms and therefore are commonly diagnosed with acute undifferentiated febrile illness. Consequently, patients face delayed treatment and increased mortality. Antibody-based serological test currently used as gold standard has limitations due to insufficient antibody titers, especially in the early phase of infection. In this study, we aimed to develop multiplex PCR to combine 3 primer pairs that target specific genes encoding 56-kDa TSA of O. tsutsugamushi, 17-kDa antigen of R. typhi, and LipL32 of L. Interrogans and evaluate its performance in comparison to the standard serological tests. Using EDTA blood samples of known patients, the sensitivity and specificity of our multiplex PCR was 100% and 70%, respectively. In addition, the assay was able to diagnose the co-infection of scrub typhus and leptospirosis. The assay may be useful in identifying causative agents during the early phase of these diseases, enabling prompt and appropriate treatment.

Scrub typhus, murine typhus, and leptospirosis are diagnosed as acute undifferentiated febrile illness. Diagnostic tests for these diseases depend on antibody detection. However, antibody detection is still limited by its tendency to return negative results during the early phase of aforementioned diseases. In this study, a novel multiplex PCR has been developed for detecting Orientia tsutsugamushi, Rickettsia typhi, and Leptospira interrogans that are simultaneously amplified in a single tube. The results have shown that multiplex PCR could be used as a diagnostic tool for detecting bacteria during the early phase of scrub typhus, murine typhus, and leptospirosis, allowing for administration of appropriate treatment.

Evaluation of scrub typhus diagnosis in China: analysis of nationwide surveillance data from 2006 to 2016

Background

Scrub typhus is a life-threatening disease caused by Orientia tsutsugamushi, and specific antimicrobial medicine is available. Early and accurate diagnosis is essential for reducing the risk of severe complications and death. In this study, we aimed to evaluate the case diagnosis situation among medical care institutions and geographical regions in China, and the results will benefit both clinical practice and the disease surveillance system.

Methods

We extracted individual scrub typhus case data 2006–2016 from a national disease surveillance system in China. The diagnosis category and interval time from illness onset to diagnosis were compared among three levels of medical care institutions and provinces. The descriptive analysis method was performed in our study.

Results

During the 11-year study period, 93 481 scrub typhus cases, including 57 deaths, were recorded in the nationwide surveillance system. The overall proportion of laboratory-confirmed cases was only 4.7%, and this proportion varied greatly among primary medical centres (2.8%), county level hospitals (4.2%), and city level hospitals (6.3%). Notably, the proportion of laboratory-confirmed cases has consistently decreased from 16.3% in 2006 to 2.6% in 2016, and the same decreasing trend was found among all three levels of medical care institutions. The interval from illness onset to case diagnosis (T_diag) for all cases was 5 days (interquartile range [IQR]: 2–9 days) and decreased from 7 days (IQR: 3–11 days) in 2006 to 5 days (IQR: 2–8 days) in 2016. The risk of death for patients with a T_diag of > 7 days was 2.2 times higher (OR = 2.21, 95% CI: 1.05–5.21) than that of patients with a T_diag of < 2 days.

Conclusions

The interval time from illness onset to diagnosis for scrub typhus cases decreased greatly in China; however, the diagnosis rate of cases with laboratory-confirmed results must be increased among all levels of medical care institutions to reduce both the risk of death and the misuse of antibiotics associated with scrub typhus.

Electronic supplementary material

The online version of this article (10.1186/s40249-019-0566-0) contains supplementary material, which is available to authorized users.

Outer Membrane Protein A Conservation among Orientia tsutsugamushi Isolates Suggests Its Potential as a Protective Antigen and Diagnostic Target

Scrub typhus threatens one billion people in the Asia-Pacific area and cases have emerged outside this region. It is caused by infection with any of the multitude of strains of the bacterium Orientia tsutsugamushi. A vaccine that affords heterologous protection and a commercially-available molecular diagnostic assay are lacking. Herein, we determined that the nucleotide and translated amino acid sequences of outer membrane protein A (OmpA) are highly conserved among 51 O. tsutsugamushi isolates. Molecular modeling revealed the predicted tertiary structure of O. tsutsugamushi OmpA to be very similar to that of the phylogenetically-related pathogen, Anaplasma phagocytophilum, including the location of a helix that contains residues functionally essential for A. phagocytophilum infection. PCR primers were developed that amplified ompA DNA from all O. tsutsugamushi strains, but not from negative control bacteria. Using these primers in quantitative PCR enabled sensitive detection and quantitation of O. tsutsugamushi ompA DNA from organs and blood of mice that had been experimentally infected with the Karp or Gilliam strains. The high degree of OmpA conservation among O. tsutsugamushi strains evidences its potential to serve as a molecular diagnostic target and justifies its consideration as a candidate for developing a broadly-protective scrub typhus vaccine.

Kinetics of IgM and IgG antibodies after scrub typhus infection and the clinical implications

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The kinetics of IgM and IgG post scrub typhus infection remain elusive.

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Scrub typhus patients were followed up to study antibody kinetics.

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IgM remained above the threshold for 12 months.

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IgG reached a peak at 10 months and remained above the threshold for 36 months.

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Paired IgM samples are required for accurate diagnosis.

Objectives

The serological detection of IgM antibodies is the most widely used test to diagnose scrub typhus infection. However, the kinetics of IgM and IgG antibodies post-infection remain elusive, which could contribute to false positivity. The objective of this study was to document the nature of the evolution of these antibody titres after infection.

Methods

Adult patients previously confirmed to have scrub typhus by IgM ELISA, positive PCR, or both, were included in this cross-sectional study. The levels of IgM and IgG antibodies in serum samples were tested using an ELISA and the distribution curve was plotted.

Results

Two hundred and three patients were included in this study. Post-infection serum sampling was done between 1 month and 46 months after documented infection. IgM levels declined gradually but remained elevated above the diagnostic cut-off for up to 12 months post-infection. However, IgG levels continued to rise reaching a peak at 10 months, followed by a gradual decline over several months. In the majority of cases, the IgG levels remained above the cut-off threshold for more than 36 months.

Conclusions

Clinicians need to be cautious in using a single serum sample for the detection of IgM to diagnose scrub typhus, as it remains elevated for up to 12 months after the infection, whereas the serum IgG level could be used as an indicator of past infection.

Development of a rapid and visual nucleotide detection method for a Chinese epidemic strain of Orientia tsutsugamushi based on recombinase polymerase amplification assay and lateral flow test

OBJECTIVES

Orientia tsutsugamushi is an obligate intracellular pathogen that causes scrub typhus. Diagnosing scrub typhus remains a challenge, and a sensitive, specific, simple, and rapid diagnostic test is still needed.

METHODS

A recombinase polymerase amplification (RPA) assay combined with a lateral flow (LF) test targeting the 56-kDa gene of a Karp-like strain of O. tsutsugamushi was developed and optimized. The detection limits, sensitivity, specificity, and simulative clinical performance were evaluated.

RESULTS

Primers and probe were screened to establish the RPA assay, and the reaction conditions were optimized. The detection limit was 10 copies/reaction in detecting plasmid DNA and 12 copies/reaction in detecting genomic DNA. The RPA-LF method could differentiate O. tsutsugamushi from other phylogenetically related bacteria. The sensitivity was 100% and specificity was over 90%, when evaluated using infected animal samples or simulative clinical samples. Furthermore, the method was completed in 20min at 37°C followed by a 3-5min incubation at room temperature for the development of an immunochromatographic strip, and the results could be determined visually.

CONCLUSIONS

This method is promising for wide-ranging use in basic medical units considering that it requires minimal instruments and infrastructure and is highly time-efficient, sensitive, and specific for diagnosing scrub typhus.

Clinical proteomic analysis of scrub typhus infection

Background

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

Methods

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

Results

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

Conclusions

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

Electronic supplementary material

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

Central Nervous System Infection Associated with Orientia tsutsugamushi in South Korea

Orientia tsutsugamushi is a major cause of vector-borne infection in Asia. Prompt recognition and appropriate treatment are crucial because of its potentially fatal complications and lack of response to beta-lactam antibiotics. The present study retrospectively evaluated the clinical characteristics and laboratory findings of 16 patients with scrub typhus-related central nervous system (CNS) infections. Single titers ≥ 1:40 of total serum antibodies against O. tsutsugamushi detected by an indirect immunofluorescent assay were considered as positive results. The median age was 35.5 (range, 14-72) years, and 10 (62.5%) patients were female. The most common symptoms were headache (81.3%) and fever (81.3%). Eschar formation was found in three (18.8%) patients. Among patients with encephalitis, seizures and altered consciousness occurred in five (83.3%) and four (66.7%) patients, respectively. An abnormal liver function was noted in seven (43.8%) patients. The median antibody titer was 1:120 (range, 1:40-1:2,560). Typical cerebrospinal fluid profiles were lymphocytic pleocytosis, mild protein elevations, and normal glucose levels. All patients received an empirical treatment with doxycycline and most (93.8%) of them recovered without neurological sequelae. None of the patients reported side effects of the doxycycline treatment. An empirical treatment with doxycycline is needed in patients with CNS infections in scrub typhus endemic areas.

Scrub typhus: risks, diagnostic issues, and management challenges

Scrub typhus is an acute febrile illness in the “tsutsugamushi triangle”, transmitted by chiggers that can be treated effectively if detected early. Laboratory testing, including molecular and serological assays, is needed for confirming the diagnosis, especially in the absence of the pathognomonic eschar. In this review, factors that play a role in disease occurrence and clinical clues for diagnosis, in addition to risk factors contributing to disease severity, including mortality, are discussed in detail. Moreover, issues related to diagnostic assays, treatment, and mixed infections are also enumerated and described.

Clinical Predictors of Multiple Organ Dysfunction Syndromes in Pediatric patients with Scrub Typhus

Scrub typhus can produce multiple organ dysfunction syndrome (MODS). Early recognition of the patients at risk of MODS would be helpful in providing timely management and reducing the mortality. In all, 449 children with scrub typhus were enrolled at three hospitals in Yunnan, China from January 2010 to January 2015. The patients' clinical status of organ system dysfunction was evaluated on the day of discharge from hospital by using standard criteria. The patients were classified into MODS present (64 cases, 14.3%) or MODS absent (385 cases, 85.7%). Multivariate logistic regression analyses revealed that the prognostic factors for MODS included skin rash (odds ratio, OR = 3.3, p = 0.037), time interval form treatment to defervescence (OR = 1.2, p = 0.035), hemoglobin (OR = 0.54, p = 0.041), platelet counts (OR = 0.06, p < 0.001), aspartate-aminotransferase (OR = 4.7, p = 0.011) and total bilirubin (OR = 2.3, p = 0.013). By describing risk factors resulting in MODS in pediatric scrub typhus, our study provides clinicians with important information to improve the clinical monitoring and prognostication of MODS.

Endemic Scrub Typhus in South America

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

Serodiagnosis of Scrub Typhus at a Tertiary Care Hospital from Southern India

INTRODUCTION

Scrub typhus, a zoonotic disease is one of the most covert emerging and re-emerging Rickettsial infections. There is an upsurge in the incidence of the disease worldwide with ever-changing habitat. Clinical diagnosis of scrub typhus is challenging as the signs and symptoms of scrub typhus are similar to other febrile illnesses. In developing countries, among the various laboratory tests to diagnose scrub typhus, Weil-Felix test is commonly performed despite its low sensitivity. The Immunofluorescence antibody (IFA) test has its limitations in terms of cost and expertise required. The present study was conducted to determine the seropositivity of IgM ELISA for scrub typhus in clinically suspected cases.

MATERIALS AND METHODS

Weil-Felix test and IgM ELISA were performed using clinically suspected cases of scrub typhus using commercially available kits.

RESULTS

Out of 482 samples tested, 109 were positive by both Weil-Felix test and IgM ELISA. One hundred and sixteen samples which were negative by Weil-Felix test reacted positive by IgM ELISA. Fourteen samples which were positive by Weil-Felix test were negative by ELISA.

CONCLUSION

Owing to the limitations of the Weil-Felix test and IFA, commercially available recombinant IgM ELISA which has a good sensitivity and specificity may be an alternative in laboratories with moderate set up.