Severe scrub typhus infection: Clinical features, diagnostic challenges and management

Omadacycline in the treatment of scrub typhus: Three case reports

BACKGROUND

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

CASE SUMMARY

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

CONCLUSION

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

Estimating the Seroincidence of Scrub Typhus using Antibody Dynamics after Infection

Scrub typhus, a vector-borne bacterial infection, is an important but neglected disease globally. Accurately characterizing the burden is challenging because of nonspecific symptoms and limited diagnostics. Prior seroepidemiology studies have struggled to find consensus cutoffs that permit comparisons of estimates across contexts and time. In this study, we present a novel approach that does not require a cutoff and instead uses information about antibody kinetics after infection to estimate seroincidence. We use data from three cohorts of scrub typhus patients in Chiang Rai, Thailand, and Vellore, India, to characterize antibody kinetics after infection and two population serosurveys in the Kathmandu Valley, Nepal, and Tamil Nadu, India, to estimate seroincidence. The samples were tested for IgM and IgG responses to Orientia tsutsugamushi-derived recombinant 56-kDa antigen using commercial enzyme-linked immunosorbent assay kits. We used Bayesian hierarchical models to characterize antibody responses after scrub typhus infection and used the joint distributions of the peak antibody titers and decay rates to estimate population-level incidence rates in the cross-sectional serosurveys. Median responses persisted above an optical density (OD) of 1.8 for 23.6 months for IgG and an OD of 1 for 4.5 months for IgM. Among 18- to 29-year-olds, the seroincidence was 10 per 1,000 person-years (95% CI, 5-19) in Tamil Nadu, India, and 14 per 1,000 person-years (95% CI: 10-20) in the Kathmandu Valley, Nepal. When seroincidence was calculated with antibody decay ignored, the disease burden was underestimated by more than 50%. The approach can be deployed prospectively, coupled with existing serosurveys, or leverage banked samples to efficiently generate scrub typhus seroincidence estimates.

Unravelling the Enigma of Scrub Typhus: A Critical Review and Insights Into Epidemiology, Clinical Features, Diagnostic Advances, and Emerging Trends

Scrub typhus (ST) is caused by the bacterium Orientia tsutsugamushi, which exhibits significant antigenic diversity and is prevalent in the Asia-Pacific region. Its clinical presentation is characterized by non-specific symptoms such as headache, myalgia, sweating, and vomiting, along with the abrupt onset of fever and chills. An eschar is often visible in the axilla, groin, or inguinal area and is present in around half of the confirmed cases. The Weil-Felix test is the earliest detection technique, though it is not highly specific. Diagnostic procedures include biopsy, culture, serology, and PCR. The molecularly detectable amount of Orientiae in the bloodstream occasionally reaches levels that are identified during acute illness and vanish after the first round of appropriate antibiotic treatment. This study offers a thorough review of ST, a disease carried by vectors caused by Orientia tsutsugamushi. We emphasize on the significance of monitoring and awareness campaigns, diagnostic problems, and geographical differences. It is essential to use multidisciplinary techniques combining epidemiologists, public health authorities, and doctors. Sustained observation and research are essential for developing successful preventative and control measures. When participating in outdoor activities in areas known for such infections or at particular times of the year when ticks or mites carry the rickettsia infection, people should take great precautions to prevent getting bitten by ticks or mites. Prompt medical evaluation is advised if suspicious symptoms or signs appear, especially in elderly individuals.

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

Background

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

Case presentation

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

Conclusion

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

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

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

Comparative Evaluation of Different Tissues and Molecular Techniques for the Zoonotic Surveillance of Scrub Typhus

Background and Objectives: Scrub typhus (ST) is detected in one-fourth of patients with acute febrile illnesses, confirming its nationwide re-emergence. The disease, if not diagnosed, can lead to multiple organ dysfunction and mortality. Being a vector-borne zoonotic disease, the molecular survey for pathogens in animal hosts is essential to predict the risk of its transmission to humans. Hence, this study aimed at identifying the effective animal tissue and molecular technique for zoonotic surveillance of ST infection in small animal hosts. Methods: Rodents/shrews were trapped from seventeen randomly selected villages in Puducherry between July and September, 2022. The presence of Orientia tsutsugamushi in ectoparasites and tissues including blood, lung, liver, spleen, kidney, heart, brain, and intestine retrieved from the animals was screened by nested PCR targeting 56 kDa, real-time PCR (qPCR) targeting 47 kDa and traD, and conventional PCR targeting groEL. The Weil-Felix test was carried out to detect antibodies against O. tsutsugamushi in rodent/shrew serum samples. Diagnostic accuracy measures of the molecular tests were calculated for each of the tissues by latent class modeling. Results: O. tsutsugamushi detected in the rodents/shrews were identified to be Karp-like and Kawasaki-like strains. Upon statistical analysis, qPCR targeting 47 kDa exhibited the highest accuracy measures in most of the tissues analyzed, with perfect sensitivity and specificity of 100% and 97% for intestine and lung samples for the epidemiological surveillance, respectively. Interpretation and Conclusion: The study recommends qPCR targeting 47 kDa gene and analysis of intestine and lung along with blood for the zoonotic surveillance of ST infection.

Acute ischemic stroke in Tsutsugamushi: understanding the underlying mechanisms and risk factors

BACKGROUND

Tsutsugamushi (scrub typhus) is an acute infectious febrile disease common in the Asia-Pacific region. Common symptoms of tsutsugamushi include lymphadenopathy, fever, and myalgia, and it rarely causes acute ischemic stroke (AIS). However, we hypothesized that tsutsugamushi infection could trigger AIS.

METHOD

We retrospectively examined patients diagnosed with AIS within 2 weeks of tsutsugamushi diagnosis at three hospitals over a 15-year period. We categorized patients who developed AIS while being treated for tsutsugamushi as the case group and those (of similar age and sex) who did not develop AIS as the control group. The case and control groups consisted of 22 and 66 participants, respectively. When a scattered pattern was observed or lesions were found in two or more vascular territories on diffusion-weighted imaging, the pattern was defined as embolic. Other patterns were defined as nonembolic.

RESULTS

Among the 19 patients, excluding three with transient ischemic stroke, 15 (78.9%) showed an embolic pattern. Although fever was common in the control group, it was less common in the case group. A higher D-dimer level at the time of hospitalization was associated with the development of AIS in patients with tsutsugamushi.

CONCLUSIONS

AIS in patients with tsutsugamushi showed an embolic rather than a non-embolic pattern on brain magnetic resonance imaging. It was more likely to occur in patients with risk factors for stroke. Tsutsugamushi patients with AIS were likely to have no fever or high D-dimer levels. We hypothesized that D-dimers play an important role in the pathophysiology, where tsutsugamushi infection increases the likelihood of AIS.

Clinical profile and outcomes of Scrub typhus in pregnant women presenting to a tertiary care hospital of North India

Scrub typhus, caused by Orientia tsutsugamushi, is a re-emerging endemic zoonosis in the Asia Pacific region. It is a febrile condition ranging in severity from mild to severe, with fatality rates as high as 30%. The present study aims towards analysing the clinical profile and pregnancy outcomes in 27 cases of scrub typhus admitted to a tertiary care centre in North India. The medical records of 27 pregnant women who had scrub typhus were analysed. The IgM ELISA was used to look for IgM antibodies to Orientia tsutsugamushi in the patient's serum sample. An optical density of more than or equal to 0.468 was considered as positive. Majority of the pregnant females delivered healthy and live babies. However, poor foetal outcomes were observed in four (14.8%) cases with intrauterine deaths occurring in two (7.4%) cases and still birth in one (3.7%) case, while one (3.7%) patient had spontaneous abortion. Maternal mortality was reported in one patient (3.7%) due to a delay in diagnosis. In endemic settings, a strong index of suspicion for scrub typhus is necessary in pregnant females presenting with fever. The key to reducing morbidity in both the mother and foetus is early diagnosis and treatment.Impact StatementWhat is already known on this subject? Scrub typhus is a febrile condition ranging in severity from mild to severe, with 30% mortality in untreated patients.What do the results of this study add? Majority of the pregnant females delivered healthy and live babies. However, poor foetal outcomes were observed in four (14.8%) cases with intrauterine deaths occurring in two (7.4%) cases and still birth in one (3.7%) case, while one (3.7%) patient had spontaneous abortion. Maternal mortality was reported in one patient (3.7%) due to a delay in diagnosis.What are the implications of these findings for clinical practice and/or further research? In endemic settings, a strong index of suspicion for scrub typhus is necessary for pregnant females presenting with fever. The key to reducing morbidity in both the mother and foetus is early diagnosis and treatment.

Identification of novel variants for complicating cardiac disease in the scrub typhus infection using whole genome sequencing

BACKGROUND/AIMS

Scrub typhus infection has been known to complicate cardiovascular diseases mainly attributing to high mortality. Genetic susceptibility loci for complicating cardiac diseases such as atrial fibrillation, heart failure, and ischemic heart disease identified by genomic study have been limited in scrub typhus infection. Therefore, we investigated the genetic novel variants predicting complicating cardiac diseases in patients with confirmed scrub typhus infection using whole genome sequencing.

METHODS

We performed a prospective study for eight consecutive patients with scrub typhus infection. During follow-up, six cases were clinically diagnosed with complicating cardiac diseases and two controls without complicating cardiac diseases. The whole genomes of the all patients were sequenced, and the individual sequence variants were compared between accordcase and control patients. Variant genotypes were compared and identified as a single nucleotide polymorphism (SNP) of the different genotype distributions between six cases and two controls.

RESULTS

The GG genotype in SNP (rs4977397) of solute carrier 24 family member 2 (SLC24A2) gene and non-TT genotype in SNP (rs2676750) of adenosine deaminase, RNA specific, B2 (ADARB2) gene were distinctively found in the case patients with complicated cardiac disease, compared with control patents in the scrub typhus infection.

CONCLUSION

We suggest that the SNPs of SLC24A2 and ADARB2 might be genetic surrogate markers for complicating cardiac diseases in the scrub typhus infection. Our study show that early detection based on individual sequence variants might be feasible to predict complicating cardiac diseases in patients with scrub typhus infection, if further studies with more participants confirm these findings.

Macrolides versus other antibiotics in pediatric scrub typhus: A meta-analysis

BACKGROUND

While Doxycycline is the recommended drug for treating scrub typhus, there is a growing trend of using Macrolides and Other antibiotics due to their perceived advantages. In this study, we compared the efficacy of Macrolides versus Other antibiotics in the treatment of pediatric scrub typhus.

METHODS

Meta-analysis of randomized controlled trials (RCTs) with GRADE (Grading of Recommendations, Assessment, Development and Evaluation) application. Major databases were searched till 30th December 2022. Children of all age groups were included. Primary outcomes included mortality rate and time to defervescence (h).

RESULTS

Of the 103 citations retrieved, 5 trials, including 383 children up to 15 years of age with probable and confirmed cases of scrub typhus, were included. None of the trials reported mortality rate. The pooled results from the trials found no significant difference between Azithromycin and Other antibiotics for any of the outcome measures. The certainty of evidence for the primary outcome was deemed to be of "very low certainty", while the certainty of evidence for the secondary outcomes ranged from "low to moderate certainty".

CONCLUSIONS

The current meta-analysis revealed that there was no significant difference between Azithromycin and Other antibiotics (such as Doxycycline and Chloramphenicol) in the treatment of scrub typhus in children. However, it's important to note that the evidence generated for the primary outcome was of "very low certainty".

PROSPERO REGISTRATION NUMBER

CRD42021276577.

South Asian Transplant Infectious Disease Guidelines for Solid Organ Transplant Candidates, Recipients, and Donors

These guidelines discuss the epidemiology, screening, diagnosis, posttransplant prophylaxis, monitoring, and management of endemic infections in solid organ transplant (SOT) candidates, recipients, and donors in South Asia. The guidelines also provide recommendations for SOT recipients traveling to this region. These guidelines are based on literature review and expert opinion by transplant physicians, surgeons, and infectious diseases specialists, mostly from South Asian countries (India, Pakistan, Bangladesh, Nepal, and Sri Lanka) as well as transplant experts from other countries. These guidelines cover relevant endemic bacterial infections (tuberculosis, leptospirosis, melioidosis, typhoid, scrub typhus), viral infections (hepatitis A, B, C, D, and E; rabies; and the arboviruses including dengue, chikungunya, Zika, Japanese encephalitis), endemic fungal infections (mucormycosis, histoplasmosis, talaromycosis, sporotrichosis), and endemic parasitic infections (malaria, leishmaniasis, toxoplasmosis, cryptosporidiosis, strongyloidiasis, and filariasis) as well as travelers' diarrhea and vaccination for SOT candidates and recipients including travelers visiting this region. These guidelines are intended to be an overview of each topic; more detailed reviews are being published as a special supplement in the Indian Journal of Transplantation .

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

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

Once Forgotten Now Re-emerging: Scrub Typhus Infection in Pediatric Patients From North West India

Background Scrub typhus is an important cause of acute febrile illness in children. It is one of the re-emerging infections in the Asia Pacific region. It is caused by the gram-negative bacteria Orientia tsutsugamushi and is spread by the bite of trombiculid mites. The initial symptomatology is nonspecific with fever, headache, vomiting, etc. The presence of eschar is said to be pathognomic. It is a systemic illness, and vasculitis is the basic pathogenic mechanism. Materials and methods A retrospective observational study was conducted in two medical colleges and associated hospitals of western Uttar Pradesh (UP) and Rajasthan, India. Case files of 21 confirmed cases of scrub typhus admitted from April 2021 to October 2022 were reviewed. Scrub typhus was suspected in children with acute undifferentiated fever, and suggestive signs and symptoms were confirmed serologically with IgM enzyme-linked immunoassay (ELISA). Demographic and clinical details were noted. Results During the study period, a total of 335 cases of acute undifferentiated fever were seen, and 6.2% of them were diagnosed as having scrub typhus infection on detailed investigation. The most common symptom was fever in 100% of them, vomiting in 57.1%, abdomen pain in 42.8%, and diarrhea in 19%. Maculopapular, erythematous rash was present in 19% of cases. None of the patients had eschar. Microvascular leakage was the main complication in 28.5%. Unusual complications seen were empyema and valvulitis in 4.7% of patients. Conclusion Scrub typhus is also seen in urban setups and in dry arid areas like Rajasthan and North West UP. So, relevant investigations should be a part of the evaluation in pediatric patients with acute undifferentiated fever. Eschar can be absent, and empyema and valvulitis are some uncommon complications. A high degree of suspicion and early diagnosis are essential as an undiagnosed infection is rapidly fatal.

Costs & outcomes of hospitalized scrub typhus infection in a tertiary hospital in south India

Background & objectives

Scrub typhus is a rickettsial infection seen along the Asian-Pacific rim and imposes a considerable burden on affected people in low- and middle-income countries. The present study was aimed to determine the direct cost of hospitalization of scrub typhus and its trend over six years.

Methods

This was a retrospective, observational, hospital based study of individuals admitted to the hospital, diagnosed with scrub typhus over six years, from January 2013 to December 2018. The potential out of pocket expenditure was evaluated.

Results

A total of 198 patients were included in the study. The median cost of admission (adjusted to INR 2020) for the six years (2013 to 2018) was found to be ₹ 37,026 (US $ 490) [interquartile range (IQR) 22,996-64,992]. The median cost for patients admitted to the intensive care unit (ICU) was ₹ 128,046 (US $ 1695) (IQR 71,575-201,171), while the cost for patients admitted to the ward-alone was ₹ 33,232 (US $ 440) (IQR 19,609-45,373). The multivariable analysis showed that ARDS and SOFA score were the independent predictors of ICU admission.

Interpretation & conclusions

Hospitalisation for scrub typhus is associated with a substantial healthcare expense. The predictors of increased cost were the presence of acute respiratory distress syndrome (ARDS), shock, increasing sequential organ failure assessment (SOFA) score and duration of hospital stay.

Prediction of risk factors for scrub typhus from 2006 to 2019 based on random forest model in Guangzhou, China

OBJECTIVES

Scrub typhus is an increasingly serious public health problem, which is becoming the most common vector-borne disease in Guangzhou. This study aimed to analyse the correlation between scrub typhus incidence and potential factors and rank the importance of influential factors.

METHODS

We collected monthly scrub typhus cases, meteorological variables, rodent density (RD), Normalised Difference Vegetation Index (NDVI), and land use type in Guangzhou from 2006 to 2019. Correlation analysis and a random forest model were used to identify the risk factors for scrub typhus and predict the importance rank of influencing factors related to scrub typhus incidence.

RESULTS

The epidemiological results of the scrub typhus cases in Guangzhou between 2006 and 2019 showed that the incidence rate was on the rise. The results of correlation analysis revealed that a positive relationship between scrub typhus incidence and meteorological factors of mean temperature (T_mean ), accumulative rainfall (RF), relative humidity (RH), sunshine hours (SH), and NDVI, RD, population density, and green land coverage area (all p < 0.001). Additionally, we tested the relationship between the incidence of scrub typhus and the lagging meteorological factors through cross-correlation function, and found that incidence was positively correlated with 1-month lag T_mean , 2-month lag RF, 2-month lag RH, and 6-month lag SH (all p < 0.001). Based on the random forest model, we found that the T_mean was the most important predictor among the influential factors, followed by NDVI.

CONCLUSIONS

Meteorological factors, NDVI, RD, and land use type jointly affect the incidence of scrub typhus in Guangzhou. Our results provide a better understanding of the influential factors correlated with scrub typus, which can improve our capacity for biological monitoring and help public health authorities to formulate disease control strategies.

HLA-B27 Negative Reactive Monoarthritis of the Hip Joint Triggered by Scrub Typhus: A Case Report

Scrub typhus is common in rural Nepal's southern plains, but its diagnosis remains difficult due to a lack of clinical suspicion and poor diagnostic resources. The absence of common manifestations of the condition including eschar might further complicate this problem and may result in treatment delays. We report a case of scrub typhus with the primary presentation of reactive monoarthritis of the left hip joint in a 19-year-old male who presented with difficulty in walking, and pain over the left hip joint. Ultrasonography of the left hip and thigh showed features of synovitis and iliopsoas bursitis. After a meticulous workup, a diagnosis of human leukocyte antigen B27 negative reactive monoarthritis of the left hip joint triggered by scrub typhus infection was made and the patient was treated with doxycycline. Delays in treatment and the rate of complications can be prevented with high clinical suspicion and awareness of the atypical presentation of the condition.

Keywords

HLA-B27; case reports; reactive arthritis; scrub typhus.

Association of Scrub Typhus in Children with Acute Encephalitis Syndrome and Meningoencephalitis, Southern India

Scrub typhus is an established cause of acute encephalitis syndrome (AES) in northern states of India. We systematically investigated 376 children with AES in southern India, using a stepwise diagnostic strategy for the causative agent of scrub typhus, Orientia tsutsugamushi, including IgM and PCR testing of blood and cerebrospinal fluid (CSF) to grade its association with AES. We diagnosed scrub typhus in 87 (23%) children; of those, association with AES was confirmed in 16 (18%) cases, probable in 55 (63%), and possible in 16 (18%). IgM detection in CSF had a sensitivity of 93% and specificity of 82% compared with PCR. Our findings suggest scrub typhus as an emerging common treatable cause of AES in children in southern India and highlight the importance of routine testing for scrub typhus in diagnostic algorithms. Our results also suggest the potential promise of IgM screening of CSF for diagnosis of AES resulting from scrub typhus.

Neurological manifestations of scrub typhus: encephalitis and Guillain-Barré syndrome (GBS)

Scrub typhus is a tropical febrile illness that mainly affects rural populations in tropical and subtropical countries. It can range in severity from a mild febrile illness to multisystem involvement. Systemic dysfunction often appears in the second week of sickness, and hepatic, renal and brain involvement are well documented. Although encephalitis is the most frequent neurological ailment, a wide range of unusual complications involving the central and peripheral nervous systems have been identified-however, concomitant multiaxial involvement of the central and peripheral nervous systems is unique. We report a case of a young man with serologically confirmed scrub typhus presenting with fever, eschar, altered sensorium and progressive quadriplegia with hyporeflexic deep tendon reflexes. MRI revealed changes suggestive of encephalitis, and there was evidence of axonopathy on nerve conduction studies. A diagnosis of scrub typhus encephalitis with concomitant Guillain-Barré syndrome was made. He received doxycycline and intravenous immunoglobulin therapy, in addition to supportive treatment.

Imported Rickettsial Infections to the United Kingdom, 2015-2020

OBJECTIVE

The burden of imported rickettsial infection in the UK is not previously described. This retrospective review identifies rickettsial cases diagnosed at the national reference laboratory between 2015-2022.

METHODS

Samples testing positive for spotted fever group, typhus group and scrub typhus IgG/IgM on acute and convalescent blood samples, and/or PCR on tissue/blood were categorised as suspected, confirmed or past infection.

RESULTS

220 patients had rickettsioses, the commonest import was acute spotted fever group infection (61%, 125/205), 54% (62/114) from South Africa. Acute typhus group cases, 60% (40/67) from Southeast Asia. One patient with Rickettsia typhi bacteremia died. Scrub typhus group infections (5%, 10/205) were exclusively from Asia and the Western Pacific regions. Overall, 43% of confirmed cases (39/91) had not received doxycycline prior to results.

CONCLUSIONS

Rickettsial infections are important and under-recognised causes of imported fever in the UK. Thorough history, examination and timely treatment with doxycycline should be considered if there is suspicion of Rickettsia infection before testing.

Scrub typhus seroprevalence from an eastern state of India: findings from the state-wide serosurvey

BACKGROUND

Scrub typhus is a mite-borne infectious disease caused primarily by the obligate intracellular bacteria Orientia tsutsugamushi, which is transmitted by chigger mites. The objective of this study was to determine the prevalence of scrub typhus among adults in Odisha, an eastern state of India.

METHODS

A descriptive cross-sectional study was conducted to analyse 1840 serum samples from five districts (Khordha, Cuttack, Ganjam, Malkangiri and Sundargarh) of Odisha collected during 2020-2021. Both immunoglobulin G (IgG) and IgM antibodies against scrub typhus were tested using commercial enzyme-linked immunosorbent assay kits. Point estimates of the 95% confidence interval and adjusted odds ratio were calculated.

RESULTS

Of 1840 participants, the prevalence of IgG positivity was 1034 (56.19%) and that of IgM was 523 (28.42%). The majority of participants were in the 18-45 y age group (53.7%). Cuttack had the highest IgG positivity (64.54%) and Malkangiri had the lowest (29.32%). The highest and lowest positivity for IgM were found in Malkangiri (40.84%) and Cuttack (25.30%), respectively.

CONCLUSIONS

With an increasing number of infections detected in the state, scrub typhus is emerging as a public health threat. Increasing awareness among the general public and healthcare professionals through health education campaigns regarding scrub typhus is essential. Early detection of the disease through the establishment of a laboratory surveillance system is required to control the transmission of scrub typhus.

Revisiting scrub typhus: A neglected tropical disease

Scrub typhus is an under diagnosed re-emerging vector borne disease caused by an intracellular gram negative bacteria, Orientia. The disease is commonly prevalent in rural and hilly areas of Tsutsugumashi triangle. The diagnosis of the disease is very challenging due to similarity of its early symptoms with other febrile illnesses, like dengue and COVID 19, as well as non-availability of rapid, reliable and cost-effective methods. Moreover, the diverse clinical presentation in severe cases make it significant health problem. The occupational and behavioral risks responsible for the transmission lead to urgent need of vaccine development against the disease. The complete knowledge about its pathogenesis and the interaction with host's immune cells may help the scientists in developing the appropriate diagnostic methods as well as the vaccines.

Development of paper-based DNA sensor for detection of O. tsutsugamushi using sustainable GQDs@AuNPs nanocomposite

The graphene quantum dots (GQDs) was synthesized using potato starch and water by hydrothermal method and further used for reduction of tetracholoroauric acid to form graphene quantum dots-gold (GQDs@AuNPs) nanocomposite. The GQDs/GQDs@AuNPs were analyzed using FTIR, UV-Vis, Flourometry and HR-TEM. The synthesized GQDs@AuNPs were further used for fabrication of cost-effective screen-printed paper electrode (SPPE) based DNA sensor for the detection of O. tsutsugamushi using htrA gene specific 5'NH2 linked DNA probe. Modification of SPPE using GQDs@AuNPs nanocomposite and ssDNA probe was monitored using EIS, FTIR, FE-SEM and AFM. The sensor detection limit (LOD) was assessed as 0.002 ng/μl from the standard calibration curve with the correlation coefficient, R² = 0.993. The sensitivity of the DNA sensor was calculated as 7700 μA/cm²/ng for ssGDNA of O. tsutsugamushi using cyclic voltammetry. The sensor validation was done using scrub typhus patient's blood DNA samples. The sensor showed good storage stability at 4 °C for six months with just a loss of 12% of the initial current values. The SPPE/DNA sensor developed is very specific, sensitive, stable and detects O. tsutsugamushi in less time.

Scrub typhus in a primary health care center of Nepal: A case series

Introduction

Scrub typhus is endemic in most parts of Southeast Asia including Nepal. Fever, rash, headache, myalgia, eschar are the common clinical features. Though endemic, scrub typhus is grossly underdiagnosed in our country due to the lack of diagnostic tools and non-specific presentation of the disease. Here we present a series of 23 cases of scrub typhus from a primary healthcare center of Nepal.

Method

This is a retrospective case series done among 23 patients diagnosed with scrub typhus and admitted to Aaruchanaute Primary health care center between August 15, 2021 to September 14, 2021. Epidemiological, clinical features and clinical outcomes of all the patients are described.

Results

Among 23 patients admitted to the primary health care center,78% were of age group 20–60 with 47% male patients. Fever was reported by all patients followed by headache (65%), cough (43%) and eschar (8%). All patients were diagnosed by rapid diagnostic kit. 95% of patients had complete recovery whereas 1 patient was referred to a higher center due to complications he developed during the period of hospital stay.

Conclusion

We conclude that when a patient presents with fever and eschar, there should be a high index of suspicion for scrub typhus, though eschar may not be present in many of the cases. Early diagnosis and prompt treatment with antibiotics is the key as the disease entity shows a good response to treatment while preventing potentially fatal complications.

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Scrub typhus is a mite-borne, acute, febrile illness caused by Orientia tsutsugamushi.

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Fever, rash, headache, myalgia, gastrointestinal symptoms and eschar are the usual clinical presentation.

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Mostly underdiagnosed in Nepal because of lack of specialized diagnostic tools.

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Can also be missed while trying to exclude COVID-19 during this pandemic.

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This case series analyses the clinical presentation and management in a resource-limited setting.

Diagnostic Value of CD4/CD8 in Scrub Typhus

Scrub typhus is often misdiagnosed in febrile patients, leading to antibiotic abuse and multiple complications. We conducted a retrospective record review at the Fourth Affiliated Hospital of Guangxi Medical University in China. Data were collected on 52 patients with a confirmed diagnosis of scrub typhus and complete clinical data. In addition, data were collected on 52 patients with bloodstream infection, 25 patients with HIV infection, 112 patients with common community-acquired pneumonia (CCAP), and 36 patients with severe community-acquired pneumonia (SCAP) to serve as control groups. The peripheral blood CD4 and CD8 counts, CD4/CD8 ratio, C-reactive protein, procalcitonin, alanine aminotransferase, aspartate aminotransferase, creatinine, and β2 microglobulin levels; and the white blood cell count and neutrophil percentage were compared between the scrub typhus and the control groups. The value of these biomarkers in the diagnosis of scrub typhus was assessed using receiver-operating characteristic curve analysis. The scrub typhus group had a significantly lower CD4 count and CD4/CD8 ratio than the bloodstream infection, CCAP, and SCAP groups, and a significantly greater CD4 count and CD4/CD8 ratio than the HIV infection group. In contrast, the scrub typhus group had a significantly greater CD8 count than the bloodstream infection and CCAP and SCAP groups, and it had a lower level of CD8 than the HIV infection group. The areas under the curve of CD4/CD8 were more than 0.93 in the receiver-operating characteristic curve analysis. These findings suggest that the CD4/CD8 ratio is a useful ancillary test for diagnosing scrub typhus.

Oral Azithromycin Versus Doxycycline in the Treatment of Children With Uncomplicated Scrub Typhus: A Randomized Controlled Trial

OBJECTIVES

To compare the efficacy of azithromycin versus doxycycline in treatment of children with uncomplicated scrub typhus in terms of percentage of children who attained remission of fever after 72 hours of administration of first dose of the study drug, mean time taken to attain fever defervescence, normalization of laboratory parameters, resolution of hepatosplenomegaly and lymphadenopathy.

DESIGN

Interventional, open-labeled randomized controlled trial.

STUDY METHODS

Patients admitted with undifferentiated fever in the In-Patient Department (IPD), Department of Paediatrics, All India Institute of Medical Sciences, Bhubaneswar, India, as per the inclusion criteria were randomized and was treated with azithromycin at 10 mg/kg/d in one group and doxycycline at 4.4 mg/kg/d for 5 days in the other group and was assessed based on the primary and secondary objectives.

RESULTS

There was no statistically significant difference between the percentage of children who attained remission of fever after 72 hours of administration of azithromycin (98.2%) and doxycycline (96.5%) (P value 0.47) and the average time taken for fever defervescence (azithromycin: 24.53 hours; doxycycline: 25.82 hours; P value 0.36). The odds of attaining fever remission in the doxycycline group as compared with the azithromycin group was 1.01 (95% confidence interval -0.60 to -1.71), which was also statistically not significant. There was less incidence of adverse drug events in the azithromycin group (1.78%) as compared with the doxycycline group (8.6%), which was statistically significant (P value 0.02).

CONCLUSION

Azithromycin is equally efficacious in terms of fever defervescence, resolution of clinical signs and laboratory parameters as doxycycline, is safer and better tolerated in children.

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

Introduction

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

Case presentation

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

Clinical discussion

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

Conclusion

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

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

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

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

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

Case Report: Fulminant Myocarditis Successfully Treated With Extracorporeal Membrane Oxygenation in Ikeda Strain Orientia tsutsugamushi Infection

Scrub typhus is an acute zoonotic febrile illness caused by Orientia tsutsugamushi having a specific geographic endemic area. This infection could be complicated with multi-organ involvement including myocarditis with variable severity. Here, we report a rare case of scrub typhus with biopsy-proven acute fulminant myocarditis which progressed very rapidly to cardiac arrest and was treated successfully with extracorporeal cardiopulmonary resuscitation. Clinicians should be alert to possible rapid progression of scrub typhus myocarditis to fulminant form and be prepared for close monitoring and temporary mechanical support if indicated.

mNGS helped diagnose scrub typhus presenting as a urinary tract infection with high D-dimer levels: a case report

Background

Scrub typhus is caused by O. tsutsugamushi and spreads through mite larvae biting the skin. Classic symptoms of the disease are eschar and lymphadenopathy. Previous reports have revealed clinical manifestations of scrub typhus, including gastrointestinal symptoms, meningoencephalitis, ocular flutter, pneumonitis, acute respiratory distress syndrome, and acute kidney injury. However, cases of scrub typhus presenting as a urinary tract infection (UTI) with high D-dimer levels could be easily misdiagnosed when clinical attention is insufficient, resulting in difficulty in making a timely diagnosis of the infection. Metagenomics next-generation sequencing (mNGS) is a revolutionary and highly sensitive method that may help in diagnosing atypical cases, even when trace amounts of pathogens are present.

Case presentation

A 52-year-old female presented with a 10-day history of fever, chills, headache and myalgia. She was initially diagnosed with influenza at a local clinic. Various antibacterials were used on the 2nd–12th day onwards; however, her symptoms persisted and were followed by increased urination duration, frequency, urgency and dysuria for 2 days. Orientia tsutsugamushi was confirmed as the pathogen responsible for the infection through mNGS analysis of her blood samples from Day 13 onwards. The patient’s temperature changed remarkably 24 h after the initiation of doxycycline. Over the next 48 h (i.e., Day 15 onwards), the patient showed clinical improvement. She recovered and was discharged from the hospital.

Conclusions

Scrub typhus can present atypical clinical symptoms, such as UTIs, in a febrile patient. mNGS may be a useful method for identifying O. tsutsugamushi infection in patients with atypical clinical manifestations.

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

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

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

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

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

Scrub Typhus: Report of Three Cases From Rural Nepal and a Brief Literature Review

Scrub typhus is endemic among farmers in the rural southern part of Nepal. It is grossly underdiagnosed due to a lack of clinical suspicion and inadequate testing facilities. The most common clinical features of the disease include fever, rashes, vomiting, myalgia, and eschar. The disease may present with ocular changes such as conjunctival injection, gastrointestinal features such as hepatitis and splenomegaly, acute kidney injury (AKI), or neurological findings in the form of meningoencephalitis. Herein, we present a report of three cases of scrub typhus from a rural part of South-west Nepal who failed to receive appropriate treatment initially. One of the patients recovered well with the treatment, the other developed AKI but recovered over the next few weeks. One of the patients died due to sepsis/multiorgan failure secondary to scrub typhus. While managing such cases in places with limited diagnostic facilities, the incorporation of early appropriate empirical therapy for scrub typhus after a careful clinical assessment prevents complications and saves lives.

Identification of a Novel Antigen for Serological Diagnosis of Scrub Typhus

Scrub typhus is an acute infectious disease caused by the bacterium Orientia tsutsugamushi, which is widely distributed in northern, southern, and eastern Asia. Early diagnosis is essential because the average case fatality rate is usually >10% but can be as high as 45% if antimicrobial treatment is delayed. Although an O. tsutsugamushi 56-kDa type-specific antigen (TSA) is commonly used for serological diagnosis of scrub typhus, the 56-kDa TSA shows variations among O. tsutsugamushi strains, which may lead to poor diagnostic results. Therefore, the discovery of new antigenic proteins may improve diagnostic accuracy. In this study, we identified an O. tsutsugamushi 27 kDa antigen through an immunoinformatic approach and verified its diagnostic potential using patient samples. Compared with the O. tsutsugamushi 56-kDa antigen, the new 27-kDa antigen showed better diagnostic specificity with similar diagnostic sensitivity. Therefore, the O. tsutsugamushi 27-kDa antigen shows potential as a novel serological diagnostic antigen for scrub typhus, providing higher diagnostic accuracy for O. tsutsugamushi than the 56-kDa antigen.

Exploring Tropical Infections: A Focus on Scrub Typhus

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

Scrub typhus in pregnancy presenting with permanent hearing loss: A case report

As clinicians, we need to be vigilant about these rare and atypical presentations given the endemic nature of scrub typhus in southern belt of the country. Timely diagnosis and appropriate treatment is the key aspect to prevent further complications.

Scrub typhus and antibiotic-resistant Orientia tsutsugamushi

Introduction: Scrub typhus is one of the most underdiagnosed and under-reported febrile illnesses requiring hospitalization, mainly occurring in Southeast and East Asia and the Pacific Islands, in an area referred to as the 'Tsutsugamushi Triangle.' Scrub typhus is a zoonotic rickettsial disease that is transmitted to humans by trombiculid mites.Areas covered: A MEDLINE/PubMed search of the available literature was performed to describe the role of antibiotic-resistant scrub typhus in therapy failure.Expert opinion: Scrub typhus is characterized by an eschar that may appear 2-3 days before sudden-onset fever with chills, headache, backache, myalgia, profuse sweating, vomiting, and enlarged lymph nodes. A macular or maculopapular skin rash can develop within 3-8 days after the onset of fever. Various antibiotics, such as chloramphenicol, tetracycline, doxycycline, macrolides, quinolones, and rifampicin, have been used to treat scrub typhus. Resistance to tetracycline has been proposed to underlie delayed clinical improvement since 1996, but recent reports have questioned the existence of doxycycline resistance. Nevertheless, the existence and importance of antibiotic-resistant scrub typhus remain uncertain and require further study.

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.

Effects of Accounting for Interval-Censored Antibody Titer Decay on Seroincidence in a Longitudinal Cohort Study of Leptospirosis

Accurate measurements of seroincidence are critical for infections undercounted by reported cases, such as influenza, arboviral diseases, and leptospirosis. However, conventional methods of interpreting paired serological samples do not account for antibody titer decay, resulting in underestimated seroincidence rates. To improve interpretation of paired sera, we modeled exponential decay of interval-censored microscopic agglutination test titers using a historical data set of leptospirosis cases traced to a point source exposure in Italy in 1984. We then applied that decay rate to a longitudinal cohort study conducted in a high-transmission setting in Salvador, Brazil (2013-2015). We estimated a decay constant of 0.926 (95% confidence interval: 0.918, 0.934) titer dilutions per month. Accounting for decay in the cohort increased the mean infection rate to 1.21 times the conventionally defined rate over 6-month intervals (range, 1.10-1.36) and 1.82 times that rate over 12-month intervals (range, 1.65-2.07). Improved estimates of infection in longitudinal data have broad epidemiologic implications, including comparing studies with different sampling intervals, improving sample size estimation, and determining risk factors for infection and the role of acquired immunity. Our method of estimating and accounting for titer decay is generalizable to other infections defined using interval-censored serological assays.

Afebrile scrub typhus infection with cardiac manifestation

Scrub typhus is an acute febrile disease transmitted via bites from mite larvae (chigger) infected with Orientia tsutsugamushi. Arrhythmias, ischaemic changes and QT prolongation are some of the observed ECG abnormalities. The patient being reported presented with angina and was found to have sinus bradycardia with ST elevation in inferior leads and T wave inversion in lateral leads. His coronary angiography was normal. Further evaluation leads to the diagnosis of scrub typhus infection. Following doxycycline therapy, his ECG became normal. Afebrile scrub typhus infection with cardiac manifestation is an uncommon scenario.

Misdiagnosis of scrub typhus as hemorrhagic fever with renal syndrome and potential co-infection of both diseases in patients in Shandong Province, China, 2013-2014

Background

Scrub typhus, caused by Orientia tsutsugamushi, an obligate intracellular gram-negative bacterium, along with hemorrhagic fever with renal syndrome (HFRS), caused by hantaviruses, are natural-focus infectious diseases prevalent in Shandong Province, China. Both diseases have similar clinical manifestations in certain disease stages and similar epidemic seasons, which has caused difficulties for physicians in distinguishing them. The aim of this study was to investigate whether misdiagnosis of scrub typhus as HFRS occurred in patients in Shandong Province.

Methods

Serum samples (N = 112) of clinically suspected HFRS patients from 2013 to 2014 in Shandong Province were analyzed with enzyme-linked immunosorbent assay (ELISA) for antibodies to both hantavirus and Orientia tsutsugamushi.

Results

ELISA showed that 56.3% (63/112) and 8.0% (9/112) of clinically suspected HFRS patients were IgM antibody positive to hantavirus and O. tsutsugamushi, respectively. Among the hantavirus IgM antibody positive patients, 7.9% (5/63) were also IgM antibody positive to O. tsutsugamushi. Among the hantavirus IgM antibody negative sera, 8.2% (4/49) of sera were positive to O. tsutsugamushi.

Conclusions

We concluded that some scrub typhus patients were misdiagnosed as HFRS and co-infection of scrub typhus and HFRS might exist in China. Due to the different treatments for scrub typhus and HFRS, physicians should carefully differentiate between scrub typhus and HFRS and consider administering anti-rickettsia antibiotics if treatment for HFRS alone does not work.

Scrub typhus is caused by O. tsutsugamushi and hemorrhagic fever with renal syndrome (HFRS) is caused by hantavirus. Both diseases have similar manifestations and have their peak epidemic season in the fall, which makes their clinical differentiation difficult to be differentiated from each other clinically. In this study, we found that scrub typhus was indeed misdiagnosed as HFRS and co-infection of O. tsutsugamushi and hantaviruses might exist in China. Owing to different treatments of HFRS and scrub typhus, physicians need pay attention to differentiate them; identify co-infection of HFRS and scrub typhus; and consider administering antibiotics if antiviral treatment alone does not work.

Scrub typhus mimicking the clinical course of infectious mononucleosis: a case report

Objective: Scrub typhus is a relatively common life-threating disease; its symptoms are non-specific and similar to those of other viral infections. Therefore, scrub typhus might be underdiagnosed.

Patient: Herein, we report a patient with scrub typhus whose clinical course mimicked that of infectious mononucleosis. A 63-year-old male patient with hypertension presented to our hospital complaining of symptoms including prolonged fever, pharyngeal discomfort, and a mild headache. He showed the appearance of a rash after amoxicillin administration. At the same time, he did not show a crusted rash on his body surface.

Results: After a comprehensive examination, Epstein-Barr virus and cytomegalovirus infections were ruled out. We suspected that this patient suffered from scrub typhus on the basis of his usual lifestyle. Finally, polymerase chain reaction analysis showed a positive result for deoxyribonucleic acid of Orientia tsutsugamushi in his blood sample. Fortunately, he recovered naturally with only supportive treatment during his hospitalization.

Conclusion: We should observe and monitor patients with infectious mononucleosis-like symptoms and emphasize the importance of a clinical interview.

Intranasal Vaccination with Outer-Membrane Protein of Orientia tsutsugamushi induces Protective Immunity Against Scrub Typhus

Scrub typhus develops after the individual is bitten by a trombiculid mite infected with Orientia tsutsugamushi. Since it has been reported that pneumonia is frequently observed in patients with scrub typhus, we investigated whether intranasal (i.n.) vaccination with the outer membrane protein of O. tsutsugamushi (OMPOT) would induce a protective immunity against O. tsutsugamushi infection. It was particular interest that when mice were infected with O. tsutsugamushi, the bacteria disseminated into the lungs, causing pneumonia. The i.n. vaccination with OMPOT induced IgG responses in serum and bronchoalveolar lavage (BAL) fluid. The anti-O. tsutsugamushi IgA Abs in BAL fluid after the vaccination showed a high correlation of the protection against O. tsutsugamushi. The vaccination induced strong Ag-specific Th1 and Th17 responses in the both spleen and lungs. In conclusion, the current study demonstrated that i.n. vaccination with OMPOT elicited protective immunity against scrub typhus in mouse with O. tsutsugamushi infection causing subsequent pneumonia.

Risk mapping of scrub typhus infections in Qingdao city, China

BACKGROUND

The emergence and re-emergence of scrub typhus has been reported in the past decade in many global regions. In this study, we aim to identify potential scrub typhus infection risk zones with high spatial resolution in Qingdao city, in which scrub typhus is endemic, to guide local prevention and control strategies.

METHODOLOGY/PRINCIPAL FINDINGS

Scrub typhus cases in Qingdao city during 2006-2018 were retrieved from the Chinese National Infectious Diseases Reporting System. We divided Qingdao city into 1,101 gridded squares and classified them into two categories: areas with and without recorded scrub typhus cases. A boosted regression tree model was used to explore environmental and socioeconomic covariates associated with scrub typhus occurrence and predict the risk of scrub typhus infection across the whole area of Qingdao city. A total of 989 scrub typhus cases were reported in Qingdao from 2006-2018, with most cases located in rural and suburban areas. The predicted risk map generated by the boosted regression tree models indicated that the highest infection risk areas were mainly concentrated in the mid-east and northeast regions of Qingdao, with gross domestic product (20.9%±1.8% standard error) and annual cumulative precipitation (20.3%±1.1%) contributing the most to the variation in the models. By using a threshold environmental suitability value of 0.26, we identified 757 squares (68.7% of the total) with a favourable environment for scrub typhus infection; 66.2% (501/757) of the squares had not yet recorded cases. It is estimated that 6.32 million people (72.5% of the total population) reside in areas with a high risk of scrub typhus infection.

CONCLUSIONS/SIGNIFICANCE

Many locations in Qingdao city with no recorded scrub typhus cases were identified as being at risk for scrub typhus occurrence. In these at-risk areas, awareness and capacity for case diagnosis and treatment should be enhanced in the local medical service institutes.

Knowledge, attitude and practices about dengue fever among adults living in Pwani Region, Tanzania in 2019

BACKGROUND

Dengue fever (DF) is currently widespread in tropical and sub-tropical countries. Among the triggers of epidemic include urbanization and internal migrations. Within the past few years, there have been DF outbreaks in Tanzania. Although Pwani region is among the predicted risk areas for the DF, there is insufficient data about people's knowledge, attitude and practices towards prevention of DF in their settings. Therefore, the aim of this study was to assess knowledge, attitude and practices about DF among adults in Pwani region in Tanzania.

METHODS

The cross-sectional study conducted in Mkuranga District, Pwani region in Tanzania. We used face-to-face interviews to collect data. The main analytical procedure was descriptive using frequencies.

RESULTS

The majority, 97.7%, were aware of DF. Nevertheless, almost 80% had a low knowledge on symptoms, transmission and vector control measures. Furthermore, less than 20% had positive attitude towards dengue fever prevention, severity of the illness and health seeking behavior.

CONCLUSION

Lack of enough knowledge and positive attitude about disease transmission, symptoms and preventive measures put the population at high risk of contracting the disease. There is need to create and improve friendly, correct and simple information, education and education messages for the rural populations.

Neurological Manifestations of Scrub Typhus: A Case Series from Tertiary Care Hospital in Southern East Rajasthan

Scrub typhus is an acute febrile infectious illness caused by rickettsia species Orientia tsutsugamushi. In recent years, scrub typhus has reemerged as a life-threatening disease in India Scrub typhus has diverse clinical manifestations ranging from a nonspecific febrile illness to severe multiorgan dysfunction, and neurological complications are also common. Spectrum of neurological complications varies from common complications such as aseptic meningitis, meningoencephalitis and cerebellitis to rare complications such as myelitis, cerebral hemorrhage, acute disseminated encephalomyelitis (ADEM), and cerebral infarction. Scrub typhus is not a common cause of acute febrile illness in state like Rajasthan, but has emerged as a life-threatening disease in recent years along with dreaded neurological complications. This case series highlights various neurological manifestations of scrub typhus as early diagnosis and treatment of neurological complications have good prognosis.

Performance of molecular and serologic tests for the diagnosis of scrub typhus

Diagnosis of scrub typhus, caused by the bacterium Orientia tsutsugamushi, is challenging because of the overlap of its non-specific symptoms with other infections coupled with the lack of sufficient data on the performance of diagnostic tests. Early diagnosis of scrub typhus is crucial to improve outcomes and this study evaluates the diagnostic performance of various tests. The present study aims at assessing the accuracy of various rapid diagnostic tests, serologic tests, and nucleic acid amplification methods on well-characterized patient samples. Adult patients with acute febrile illness and manifestations suggestive of scrub typhus confirmed by positive PCR in the blood, eschar or tissue were characterized as cases. Patients with acute febrile illness and a confirmed alternate etiology such as culture-confirmed typhoid, smear/PCR positive for malaria, PCR/NS1 antigen positive for dengue, PCR positive for influenza, PCR/MAT positive for leptospirosis, PCR positive for spotted fever were characterized as controls with other infections. The healthy controls consisted of subjects from the same geographic region. We performed the following tests on blood samples for scrub typhus and calculated the sensitivity, specificity, positive predictive value, and negative predictive value: (1) Quantitative real time PCR using 47kDa gene (qPCR); (2) Conventional PCR using 56kDa gene (cPCR); (3) Loop-mediated isothermal amplification assay (LAMP assay); (4) Immunofluorescence assay (IFA); (5) Enzyme-linked immunosorbent assay (ELISA); (6) Weil-Felix test(WF test); and (7) Immunochromatographic Rapid Diagnostic Test (RDT).Among the 316 participants, 158 had confirmed scrub typhus (cases) and 158 were controls. ELISA and RDT detecting Orientia tsutsugamushi specific IgM antibodies had excellent discriminative potential with sensitivities and specificities of 92%, 94% and 92%, 92% respectively. The sensitivity and specificity of IFA were found to be 95% and 74% respectively. IgM serology had a false positivity rate of 8% with other acute febrile illnesses such as dengue, leptospirosis and spotted fever due to the nonspecific binding of the pentavalent IgM. LAMP assay had 91.7% sensitivity and 77.2% specificity while qPCR provided excellent sensitivity (97%) and perfect specificity. In conclusion, ELISA and RDT detecting Orientia tsutsugamushi specific IgM antibodies have excellent sensitivity and specificity while the accuracy of IFA is suboptimal for the diagnosis of scrub typhus. Given its perfect specificity and superior sensitivity, qPCR is preferred for diagnostic confirmation in reference laboratories particularly for diagnosis of early disease with less than 7 days duration. This study provides a comprehensive evaluation of all currently available diagnostic tests for scrub typhus.

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.