A review of the global epidemiology of scrub typhus

Deciphering the genotypic diversity and epidemiology of scrub typhus genotypes in India: A systematic review and meta-analysis

BACKGROUND

Scrub typhus is a significant cause of Acute Febrile Illness in India and presents a range of clinical manifestations influenced by the genotypes of the causative agent, Orientia tsutsugamushi. Understanding the distribution of these genotypes is crucial for public health planning, diagnostic accuracy, and vaccine development.

METHODS

In this systematic review, we analyzed 18 studies from an initial pool of 2013 records identified through database searches following PRISMA guidelines. The relevance of the findings to the genotype prevalence of Scrub typhus in India was taken into consideration throughout the selection process. Various genotyping methods, predominantly Polymerase Chain Reaction (PCR), were used in these studies to identify genotypes such as Karp, Gilliam, Kato, and others.

RESULTS

The review revealed diverse prevalence rates of Scrub typhus genotypes across different Indian states. The Karp genotype is the most prevalent in India, with a pooled prevalence of 47 %, followed by the Kato genotype at 40 % and the Gilliam genotype at 28 %. The Karp genotype showed significant variability, with prevalence rates ranging from 100 % in Andhra Pradesh (2018) to 6.16 % in Uttar Pradesh (2016-2017). The Kato genotype's presence varied significantly, with high prevalence in certain states like Karnataka and absence in others like Andhra Pradesh. The Gilliam genotype also displayed a unique distribution pattern, dominating in Uttar Pradesh with a prevalence of 93.8 % in some years. Other genotypes like Boryong, IHS-II, Neimeng, Kuroki, TA763, and Kawasaki also showed varied prevalence across states. There was significant heterogeneity in the prevalence rates of different genotypes among studies, as indicated by I2 statistics.

CONCLUSION

The diversity in Scrub typhus genotypes across India underscores the disease's complex epidemiology, presenting diagnostic challenges and opportunities for targeted public health interventions. For efficient disease management and control plans in India, it is imperative to understand the changing genetic landscape of scrub typhus through ongoing study and surveillance.

A review on trombiculiasis: An underreported parasitosis that affects humans and animals, including world distribution, clinical findings, associated pathogens, prophylaxis and identification methods

Chigger mites comprise three families: Trombiculidae, Leeuwenhoekiidae and Walchiidae, with over 3,000 species worldwide. Their life cycle includes six stages, and the larvae are parasites, while the other stages are free-living predators. Once attached to a host, the larvae spend several days feeding on the host's epithelial tissue, forming the stylostome. An inflammatory reaction can be formed during larval feeding, known as trombiculiasis or trombiculosis. In this study, we provide a literature review using 123 scientific articles on the cases of trombiculiasis in animals and humans reported in different biogeographical regions, including 29 countries and 30 different chigger species, with all the information compiled in the Supplementary material. This review aims to increase the visibility of this disease and group of mites, so that physicians and veterinarians can become more aware of the disease and include the causative agent in differential diagnoses. We also offer knowledge on mounting and control methods in order to improve mite identification for future research. Lastly, the prophylaxis and control methods in cases of infestations and associated pathogens are mentioned.

Retrospective analysis of spatiotemporal variation of scrub typhus in Yunnan Province, 2006-2022

BACKGROUND

Scrub typhus is a life-threatening zoonotic infection. In recent years, the endemic areas of scrub typhus have been continuously expanding, and the incidence rate has been increasing. However, it remains a globally neglected disease. Yunnan Province is a major infected area, and the study of spatiotemporal and seasonal variation scrub typhus in this region is crucial for the prevention and control of the disease.

METHODS/RESULTS

We collected surveillance data on scrub typhus cases in Yunnan Province from 2006 to 2022. Using methods such as spatial trend analysis, Moran's I, and retrospective temporal scan statistics, the spatial and seasonal changes of scrub typhus were analyzed. The study period recorded 71,068 reported cases of scrub typhus in Yunnan Province, with the annual incidence rate sharply increasing (P<0.001). Approximately 93.38% of cases are concentrated in June to November (P = 0.001). Nearly 98.0% of counties were affected. The center of gravity of incidence migrates in a south and west direction. The incidence of scrub typhus was positively correlated spatially, and the spatial clustering distribution was significant. The most likely spatial cluster of cases (relative risk = 14.09, P<0.001) was distributed in Lincang, Dehong, Baoshan, Banna, and Puer. Significant positive correlations between the number of scrub typhus cases and average temperature, precipitation and relative humidity.

CONCLUSIONS

In Yunnan Province, scrub typhus is widely transmitted, with an increasing incidence, and it exhibits distinct seasonal characteristics (from June to November). The center of gravity of incidence has shifted to the south and west, with higher incidence rates observed in border regions. The risk clustering regions encompass all border prefectures. This pattern is significantly correlated with climatic factors such as average temperature, precipitation, and relative humidity. The relevant departments should strengthen the monitoring of scrub typhus, formulate prevention and control strategies, and provide health education to local residents.

Diversity of bartonellae in mites (Acari: Mesostigmata: Macronyssidae and Spinturnicidae) of boreal forest bats: Association of host specificity of mites and habitat selection of hosts with vector potential

Research into various bacterial pathogens that can be transmitted between different animals and may have zoonotic potential has led to the discovery of different strains of Bartonella sp. in bats and their associated ectoparasites. Despite their enormous species diversity, only a few studies have focussed on the detection of bacterial pathogens in insectivorous bats of boreal forests and their associated Macronyssidae and Spinturnicidae mites. We collected and molecularly analysed mite samples from forest-dwelling bat species distributed all along the boreal belt of the Palearctic, from Central Europe to Far East. Ectoparasitic mites were pooled for DNA extraction and DNA amplification polymerase chain reaction (PCRs) were conducted to detect the presence of various bacterial (Anaplasmataceae, Bartonella sp., Rickettsia sp., Mycoplasma sp.) and protozoal (Hepatozoon sp.) pathogens. Bartonella sp. DNA was detected in four different mite species (Macronyssidae: Steatonyssus periblepharus and Spinturnicidae: Spinturnix acuminata, Sp. myoti and Sp. mystacinus), with different prevalences of the targeted gene (gltA, 16-23S ribosomal RNA intergenic spacer and ftsZ). Larger pools (>5 samples pooled) were more likely to harbour Bartonella sp. DNA, than smaller ones. In addition, cave-dwelling bat hosts and host generalist mite species are more associated with Bartonella spp. presence. Spinturnicidae mites may transmit several distinct Bartonella strains, which cluster phylogenetically close to Bartonella species known to cause diseases in humans and livestock. Mites with ubiquitous presence may facilitate the long-term maintenance (and even local recurrence) of Bartonella-infestations inside local bat populations, thus acting as continuous reservoirs for Bartonella spp in bats.

The High Prevalence of Orientia tsutsugamushi Among Wild Rodents and the Identification of Its Major Serotypes in Yamaguchi Prefecture, Japan, Where Scrub Typhus Patients Are Rarely Identified

Orientia tsutsugamushi (OT) is an obligate intracellular bacterium transmitted by larval trombiculid mites, responsible for scrub typhus in humans. In Japan, approximately 500 human cases are reported annually, with six major serotypes identified as Kato, Karp, Gilliam, Irie/Kawasaki, Shimokoshi, and Hirano/Kuroki. However, the prevalence of OT in Yamaguchi prefecture remains largely unknown. This study aimed to investigate the prevalence and serotypes of OT in wild rodents collected from eight locations within the prefecture. DNA was extracted from spleen and liver samples of 135 wild rodents collected between 2015 and 2024, and PCR was conducted to detect OT targeting the 56 kDa type-specific antigen gene. As a result, five individuals (3.7%) were detected positive for OT DNA. OT was successfully isolated from two of the five rodents and characterized by multi-locus sequence analysis (MLSA) based on 11 housekeeping genes. The MLSA results indicated that both isolates clustered with OT strain Ikeda (JG serotype). Additionally, we performed a serological test on 117 serum samples from wild rodents using the indirect immune peroxidase test. The results showed that 59.8% (n = 70/117) of the rodents had antibodies against OT, with 73% (n = 51/70) showing the highest titer against the OT strains Gilliam (Gilliam serotype) and Ikeda (JG serotype), known to be transmitted by Leptotrombidum pallidum mites. Overall, the present study identified the OT serotypes and potential primary vector species in Yamaguchi prefecture, emphasizing the need for further surveillance, particularly, in humans.

A Retrospective Report on the Infestation and Distribution of Chiggers on an Endemic Rodent Species (Apodemus latronum) in Southwest China

Chiggers are the exclusive vector of Orientia tsutsugamushi, which is the causative agent of scrub typhus. Based on the field surveys in southwest China between 2001 and 2022, this paper retrospectively reported the chigger infestation and distribution on the large-eared field mouse (Apodemus latronum), an endemic rodent species in the region, for the first time. A total of 933 chiggers were collected from 501 mice, and these chiggers were identified as 2 families, 8 genera, and 61 species. The overall infestation prevalence (PM) and mean abundance (MA) of A. latronum with chiggers reached 19.76% and 1.86 mites/per mouse, respectively. The chigger infestation indices on adult A. latronum (PM = 38.28%, MA = 5.11) were higher than those on juvenile mice (PM = 12.63%, MA = 0.97) with p < 0.01, showing an age bias of infestation. The relative fatness (K) was used to reflect the nutrition status of the mouse host. The mouse hosts with good nutrition (K = 3.4 ± 0.89 g/cm3) harbored fewer chiggers than the hosts with poor nutrition (K = 2.2 ± 0.90 g/cm3) (p < 0.01). The infestation indices of chiggers on A. latronum obviously fluctuated along different altitude gradients (p < 0.01). With the increase in altitudes, the β diversity of the chigger community showed a gradually increasing tendency. The spillover chord diagram, which was based on indices of PAC (potential for apparent competition), revealed high spillover potentials of dominant chigger species dispersing from high altitude gradients to the lowest one. The chigger abundance was positively correlated with the mean monthly temperature (tmp), mean monthly humidity (hum), the mean monthly precipitation (pre), and the human footprint (hfp), and it was negatively correlated with the altitude (ele) (p < 0.05). The temperature and humidity are the most important factors which influence the chigger infestation.

Scrub Typhus Outbreak among Soldiers in Coastal Training Area, Australia, 2022

A scrub typhus outbreak occurred among 24 soldiers from 2 Australian Defence Force infantry units following separate training events conducted in the same coastal location in tropical North Queensland, Australia, in June 2022. Seven soldiers visited a hospital, 5 requiring admission. Outbreak recognition was hampered by the geographic dispersion of soldiers after the exercise and delayed case identification resulting from such factors as prolonged incubation, cross-reactive serologic responses to other pathogens, the nonspecific symptoms of scrub typhus, and the illness's nonnotifiable status in the state of Queensland. Our investigation focused on personal protective measures in a subanalysis of 41 soldiers, revealing an association between scrub typhus infection and the use of doxycycline chemoprophylaxis and permethrin uniform dipping.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSION

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

A case report of fatal Rickettsia japonica bloodstream infection in Zhejiang, China

Japanese spotted fever (JSF) is an emerging acute febrile natural infectious disease caused by the neglected zoonotic pathogen Rickettsia japonica. Here we reported a 64-year-old female patient who initially presented to the local hospital with an intermittent fever of unknown origin (FUO). A systemic, evident edema and eschar on the skin of the patient's upper limb was observed. The patient was diagnosed with critical Rickettsia japonica bloodstream infection by Q-mNGS and treated with doxycycline, as well as symptomatic treatments. Unfortunately, the patient passed away as a result of complications of septic shock and multiple organ and acute respiratory failure. Delayed treatment resulting from the nonspecific clinical symptoms in the early stages of infection can lead to fatal complications. Q-mNGS is an emerging pathogen detection method with the advantages of comprehensive detection, high accuracy and sensitivity and should be promoted and applied by clinicians.

"Is it time to initiate scrub typhus surveillance in Karnataka?"-Lessons from a seroprevalence survey in a rural district

Background

Scrub typhus, caused by Orientia tsutsugamushi, is a commonly occurring, but underdiagnosed rickettsial infection in India. Considering the high incidence of scrub typhus among patients with acute febrile illness in the hospital setting and the paucity of community seroprevalence studies, we aimed to estimate the prevalence of scrub typhus in the community in the Bengaluru Rural District.

Methods

A pilot cross-sectional survey was conducted between October and December 2022 among eligible asymptomatic adults from five randomly selected villages of the Bangalore Rural District after obtaining written informed consent. Serum immunoglobin M (IgM) and immunoglobin G (IgG) antibodies were tested using the respective enzyme-linked immunosorbent assay (ELISA) kits from InBios International Inc, Seattle, USA. Seroprevalence was defined as positivity to either IgG or IgM antibodies or both.

Results

The study reported a seroprevalence of 8.9% (95% CI 4.8%-14.7%) among 146 asymptomatic adults. The IgG and IgM antibodies were positive in 7.5% and 2.1% of participants, respectively.

Conclusions

A community seroprevalence of 8.9% warrants further epidemiological surveys and surveillance in the context of climate change, variable clinical presentations of scrub typhus, and the possible need to include this disease in the clinical practice algorithm in the primary care setting. We recommend study designs with "One Health" lens to monitor the trend of this re-emerging public health problem.

Changes in seasonality and sex ratio of scrub typhus: a case study of South Korea from 2003 to 2019 based on wavelet transform analysis

BACKGROUND

Scrub typhus (ST, also known as tsutsugamushi disease) is a common febrile vector-borne disease in South Korea and commonly known as autumn- and female-dominant disease. Although understanding changes in seasonality and sex differences in ST is essential for preparing health interventions, previous studies have not dealt with variations in periodicity and demographic characteristics in detail. Therefore, we aimed to quantify the temporal dynamics of seasonal patterns and sex differences in the incidence of ST in South Korea.

METHODS

We extracted epidemiological week (epi-week)-based ST cases from 2003 to 2019 Korean National Health Insurance Service data (ICD-10-CM code: A75.3). To determine changes in seasonality and sex differences, year-, sex-, and age-group-stratified male-to-female ratios and wavelet transform analyses were conducted.

RESULTS

Between 2003 and 2019, 213,976 ST cases were identified. The incidence per 100,000 population increased by 408.8% from 9.1 in 2003 to 37.2 in 2012, and subsequently decreased by 59.7% from 2012 to 15.0 in 2019. According to the continuous wavelet transform results, ST exhibited a dual seasonal pattern with dominant seasonality in autumn and smaller seasonality in spring from 2005 to 2019. Overall, the periodicity of seasonality decreased, whereas its strength decreased in autumn and increased in spring. With an overall male-to-female ratio being 0.68:1, the ratio has increased from 0.67:1 in 2003 to 0.78:1 in 2019 (Kendall's τ = 0.706, p < 0.001). However, interestingly, the ratio varied significantly across different age groups.

CONCLUSIONS

Our findings quantitatively demonstrated changes in seasonality with dual seasonal pattern and shortened overall periodicity and a decrease in sex differences of ST in South Korea. Our study suggests the need for continuous surveillance on populations of vector and host to address ST dynamics to preemptively prepare against global warming.

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

RATIONALE

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

PATIENT CONCERNS

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

DIAGNOSES

Scrub typhus, multiple organ dysfunction syndrome.

INTERVENTIONS

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

OUTCOMES

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

LESSONS

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

Estimation of scrub typhus incidence and spatiotemporal multicomponent characteristics from 2016 to 2023 in Zhejiang Province, China

Background

China is one of the main epidemic areas of scrub typhus, and Zhejiang Province, which is located in the coastal area of southeastern China, is considered a key region of scrub typhus. However, there may be significant bias in the number of reported cases of scrub typhus, to the extent that its epidemiological patterns are not clearly understood. The purpose of this study was to estimate the possible incidence of scrub typhus and to identify the main driving components affecting the occurrence of scrub typhus at the county level.

Methods

Data on patients with scrub typhus diagnosed at medical institutions between January 2016 and December 2023 were collected from the China Disease Control and Prevention Information System (CDCPIS). The kriging interpolation method was used to estimate the possible incidence of scrub typhus. Additionally, a multivariate time series model was applied to identify the main driving components affecting the occurrence of scrub typhus in different regions.

Results

From January 2016 to September 2023, 2,678 cases of scrub typhus were reported in Zhejiang Province, including 1 case of reported death, with an overall case fatality rate of 0.04%. The seasonal characteristics of scrub typhus in Zhejiang Province followed an annual single peak model, and the months of peak onset in different cities were different. The estimated area with case occurrence was relatively wider. There were 41 counties in Zhejiang Province with an annual reported case count of less than 1, while from the estimated annual incidence, the number of counties with less than 1 case decreased to 21. The average annual number of cases in most regions fluctuated between 0 and 15. The numbers of cases in the central urban area of Hangzhou city, Jiaxin city and Huzhou city did not exceed 5. The estimated random effect variance parameters σ λ 2 , σ ϕ 2 , and σ ν 2 were 0.48, 1.03 and 3.48, respectively. The endemic component values of the top 10 counties were Shuichang, Cangnan, Chun'an, Xinchang, Pingyang, Xianju, Longquan, Dongyang, Yueqing and Qingyuan. The spatiotemporal component values of the top 10 counties were Pujiang, Anji, Pan'an, Dongyang, Jinyun, Ninghai, Yongjia, Xiaoshan, Yinwu and Shengzhou. The autoregressive component values of the top 10 counties were Lin'an, Cangnan, Chun'an, Yiwu, Pujiang, Longquan, Xinchang, Luqiao, Sanmen and Fuyang.

Conclusion

The estimated incidence was higher than the current reported number of cases, and the possible impact area of the epidemic was also wider than the areas with reported cases. The main driving factors of the scrub typhus epidemic in Zhejiang included endemic components such as natural factors, but there was significant heterogeneity in the composition of driving factors in different regions. Some regions were driven by spatiotemporal spread across regions, and the time autoregressive effect in individual regions could not be ignored. These results that monitoring of cases, vectors, and pathogens of scrub typhus should be strengthened. Furthermore, each region should take targeted prevention and control measures based on the main driving factors of the local epidemic to improve the accuracy of prevention and control.

Vector-Borne Zoonotic Lymphadenitis-The Causative Agents, Epidemiology, Diagnostic Approach, and Therapeutic Possibilities-An Overview

In addition to common skin pathogens, acute focal lymphadenitis in humans can, in rare cases, be caused by a zoonotic pathogen. Furthermore, it can develop in the absence of any direct or indirect contact with infected animals, in cases when the microorganism is transmitted by a vector. These clinical entities are rare, and therefore often not easily recognized, yet many zoonotic illnesses are currently considered emerging or re-emerging in many regions. Focal zoonotic vector-borne lymphadenitis and its numerous causative agents, with their variegated clinical manifestations, have been described in some case reports and small case series. Therefore, we summarized those data in this narrative overview, with the aim of raising clinical awareness, which could improve clinical outcomes. This overview briefly covers reported pathogens, their vectors and geographic distribution, and their main clinical manifestations, diagnostic possibilities, and recommended therapy. Vector-borne tularemia, plague, bartonellosis, rickettsioses, borreliosis, and Malayan filariasis are mentioned. According to the existing data, when acute focal bacterial vector-borne zoonotic lymphadenitis is suspected, in severe or complicated cases it seems prudent to apply combined aminoglycoside (or quinolone) plus doxycycline as an empirical therapy, pending definite diagnostic results. In this field, the "one health approach" and further epidemiological and clinical studies are needed.

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

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

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

Background

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

Methods

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

Discussion

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

PROSPERO Registration

CRD42022315209.

A molecular survey of zoonotic pathogens of public health importance in rodents/shrews and their ectoparasites trapped in Puducherry, India

BACKGROUND

Globally, India has a high zoonotic disease burden and lacks surveillance data in humans and animals. Rodents are known reservoirs for many zoonotic diseases and their synanthropic behavior poses a great public health threat.

METHODS

In this study, trapped rodents/shrews from randomly selected villages within Puducherry, India, and their ectoparasites were screened for zoonotic pathogens, namely, Orientia tsutsugamushi, other pathogenic rickettsiae, Leptospira spp., Cryptosporidium spp., Coxiella burnetii and methicillin-resistant Staphylococcus aureus (MRSA) using conventional PCR. A total of 58 rodents/shrews were trapped from 11 villages. The species trapped were Suncus murinus (49/58, 84.48%), Rattus rattus (8/58, 13.79%) and Rattus norvegicus (1/58, 1.72%). All ectoparasites collected were identified as mites and its infestation rate was 46.55% (27/58).

RESULTS

Real-time PCR targeting the 47 kDa gene of O. tsutsugamushi revealed positivity in one rodent and one shrew (3.45%) and two mite pools (7.41%). Conventional PCR targeting the 56 kDa gene revealed positivity in one shrew and two mite pools and the phylogenetic analysis of all three amplicons indicated the circulation of the Gilliam-related serotype. MRSA was detected in the alimentary tract of a shrew (1/32, 3.13%). Leptospira spp., Rickettsia, Cryptosporidium spp. and Co. burnetii tested negative.

CONCLUSIONS

The detection of zoonotic pathogens within reservoir hosts and vectors poses a risk of transmission to humans. This study signifies the need for zoonotic pathogen surveillance in synanthropic rodents/shrews.

Scrub Typhus and Bilateral Lateral Rectus Palsy: An Uncommon Manifestation

Scrub typhus is a zoonotic disease that typically presents as an acute febrile illness. It is caused by the rickettsial organism Orientia tsutsugamushi, which is prevalent in the Asian region. The clinical manifestations of scrub typhus can vary significantly, ranging from mild febrile illness to severe multiorgan dysfunction syndrome. While the clinical presentation can be diverse, abducens nerve palsy is an extremely uncommon complication reported. This report discusses a 14-year-old previously healthy girl, who exhibited sudden onset of bilateral abducens nerve palsy, accompanied by headache and fever, but without the characteristic skin lesion known as "eschar." After ruling out common infectious diseases and other potential causes, she was ultimately diagnosed with scrub typhus complicated by abducens nerve palsy, which showed full recovery with doxycycline treatment.

Global and regional seroprevalence, incidence, mortality of, and risk factors for scrub typhus: A systematic review and meta-analysis

OBJECTIVES

Scrub typhus is underdiagnosed and underreported but emerging as a global public health problem. We aimed to provide the first comprehensive review on the seroprevalence, incidence, mortality of and risk factors for scrub typhus.

METHODS

We searched PubMed, Scopus, Web of Science, China National Knowledge Infrastructure and other databases. Trended incidence and median mortality were calculated and pooled seroprevalence and risk factors for scrub typhus were evaluated using the random-effects meta-analysis.

RESULTS

We included 663 articles from 29 countries/regions. The pooled seroprevalence was 10.73% (95%CI 9.47-12.13%) among healthy individuals and 22.58% (95%CI: 20.55%-24.76%) among febrile patients. Mainland China reported the highest number of cases and South Korea and Thailand had the highest incidence rates. Median mortalities were 5.00% (range: 0.00-56.00%) among hospital inpatients, 6.70% (range: 0.00-33.33%) among patients without specified admission status and 2.17% (range: 0.00-22.22%) among outpatients. The significant risk factors included agricultural work, specific vegetation exposure, other outdoor activities, risky personal health habits, and proximity to rodents, livestock, or poultry.

CONCLUSIONS

Our comprehensive review elucidates the significant yet variable burden of scrub typhus across different regions, underscoring its emergence as a critical public health concern globally.

Estimating the Seroprevalence of Scrub Typhus in Nepal

Prior to the devastating earthquake in Nepal in 2015, scrub typhus was not recognized as a highly endemic disease in the country. This contrasted with neighboring India, where scrub typhus is endemic and there have been sporadic outbreaks of severe forms. This discrepancy underscores the limitations in our comprehensive understanding of the scrub typhus epidemiological patterns in Nepal, especially before 2015. To better understand the dynamic and current status of scrub typhus, this study investigated its prevalence among patients with acute febrile illness in two hospitals located in Pokhara city, Kaski district and Bharatpur city, Chitwan district during 2009-2010. Our findings revealed that 31.5% (239 of 759 patients) of the cases were positives for scrub typhus based on serological and pathogen detection assays. These results provide crucial insights into the pre-earthquake endemicity of scrub typhus in Nepal, implying its long-standing presence in the region prior to the significant environmental transformations caused by the 2015 earthquake. This study also emphasizes the need for heightened awareness and improved diagnostic capabilities to effectively manage and control scrub typhus, which remains a significant public health concern in Nepal.

Scrub typhus meningoencephalitis in children: an experience from Eastern India

Scrub typhus meningoencephalitis (STME) is an uncommon but fatal complication of scrub typhus that requires extra diligence in early identification and treatment. The goal of this study was to look at the clinical characteristics, laboratory results, and outcome of STME in children. A retrospective study was conducted in the paediatric intensive care unit of a tertiary care hospital in Eastern India between April 2021 and September 2022. It was carried out in children aged 1 month-12 years. Sixteen children were diagnosed with STME out of 75 acute encephalitis syndrome (AES) cases. The male-to-female ratio was 3:1, with a mean age of 4.28 ± 3.36 years. All the children hailed from rural areas. Fever (100%), convulsions (87.5), altered sensorium (93.75%), nuchal stiffness (25%), vomiting (75%), pallor (75%), and hepatomegaly (50%) were the most prevalent clinical manifestations. The average duration of fever upon presentation was 8.25 ± 2.11 days and the average length of hospital stay was 9.00 ± 4.59 days. The complications encountered were shock (3), interstitial pneumonia (1), myocarditis (1), raised intracranial pressure (1), and right-sided hemiplegia (1). Fifteen children recovered completely, whereas one child suffered from residual right-sided neurodeficit. A high index of suspicion needs to be maintained for STME as a possible AES entity, as anti-scrub measures administered promptly can go a long way in mitigating the related morbidity and mortality especially in resource-constrained settings.

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.

Prevalence, Clinico-Laboratory Features and Outcomes of Paediatric Scrub Typhus Cases in a Tertiary Care Centre in Eastern India: A prospective observational study

Objectives

Scrub typhus is the most common rickettsial disease in India, caused by Orientia tsutsugamushi and transmitted by chigger mites. Previously prevalent in South India, a resurgence of scrub typhus cases has recently affected Eastern India. This study aimed to estimate the prevalence and describe the clinico-laboratory profile of scrub typhus in paediatric patients (1-12 years old) living in Eastern India.

Methods

This prospective observational study was conducted from January to December 2019 at the Dr B C Roy Post Graduate Institute of Paediatric Sciences, Kolkata, India. All acute undifferentiated cases of febrile illness, in patients aged between 1-12 years, were tested using scrub typhus serology by ELISA. Demographic details, clinical features, laboratory findings, complications and treatment outcomes of these scrub typhus patients were extracted and analysed.

Results

Out of 1,473 patients with acute febrile illness, 67 (4.5%) children were diagnosed with scrub typhus. The mean age of the selected patients was 5.22 ± 3.05 years, and the majority (64.2%) had been running a fever since the preceding 7-14 days. Gastrointestinal symptoms such as vomiting (43.3%) and abdominal pain (32.8%) were most frequently observed. Major clinical signs of scrub typhus were hepatomegaly (41.8%) and splenomegaly (31.3%). Complications were observed in 74.6% of patients, with thrombocytopenia (40.3%) and meningoencephalitis (29.9%) occurring more frequently. The case fatality rate of the study sample was 1.5%.

Conclusion

Classical eschar was absent in three-fourth of the studied patients. Hence, this study advocates laboratory scrub typhus tests for all suspected cases in the endemic region (Eastern India). Prompt treatment with doxycycline and/or azithromycin could prevent complications such as thrombocytopenia/meningoencephalitis and reduce mortality.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Human granulocytotropic anaplasmosis-A systematic review and analysis of the literature

Human granulocytotropic anaplasmosis (HGA) is a zoonotic tick-borne bacterial infection caused by Anaplasma phagocytophilum. While most cases are reported from North America, HGA has been recognized as an emerging disease in several regions of the world in recent decades. Most available data comes from case reports, case series and retrospective studies, while prospective studies and clinical trials are largely lacking. To obtain a clearer picture of the currently known epidemiologic distribution, clinical and paraclinical presentation, diagnostic aspects, complications, therapeutic aspects, and outcomes of HGA, we systematically reviewed the literature and analyzed and summarized the data. Cases of HGA are reported from all continents except from Antarctica. HGA primarily presents as an unspecific febrile illness (88.5% of the cases) often accompanied by thrombocytopenia (71.8% of the cases), abnormal liver injury tests (66.7% of the cases), and leukopenia (49.8% of the cases). Although we found complications reported in a total of 40.5% of the reviewed cases and severe and even life-threatening complications are not infrequent (e.g. acute renal failure 9.8%, multi organ failure 7.5%, ARDS 6.3%, a.o.), sequelae are rare (2.1% of the cases) and lethality is low (3.0% of the cases). Treatment with doxycycline shows a rapid response, with the fever subsiding in the majority of patients within one day of starting treatment. Unlike in human monocytotropic ehrlichiosis (HME), reports of opportunistic infections complicating HGA are rare. HGA during pregnancy does not appear to be associated with unfavorable outcomes. In addition, our analysis provides some evidence that HGA may differ in clinical aspects and laboratory characteristics in different regions of the world. Overall, the data analyzed indicates a non-negligible bias in reporting/publication, so a certain degree of caution is required when generalizing the data.

Explorational analysis of the abundance and prevalence of chigger and gamasid mites parasitic on small mammals in Vietnam

We studied chigger and gamasid mite loads on small mammals during the dry season in Vietnam and used both our field data and museum collections to estimate the influence of environmental factors on mite abundance and prevalence. Generalized linear (mixed effect) models were used to analyze the data. We examined 1,239 small mammal individuals, which were obtained from field expeditions and museum collections belonging to 59 species. In different localities, Rattus Fischer (Rodentia: Muridae), Niviventer Marshall (Rodentia: Muridae), and Maxomys Sody (Rodentia: Muridae) were the most common animals captured. The prevalence of chigger and gamasid mites in our expedition data was high: 72% and 62%, respectively. We found differences in the abundance of chigger mites between different populations of the same species of small mammals. Season and locality were the main factors that influenced chigger mite abundance and prevalence. The best model that predicted the abundance and prevalence of chigger mites included geography (province) as a predictor and host species and season as random effects. For the first time, we analyzed factors connected with climate and weather affecting chigger mites of small mammals in Vietnam.

Dominant B cell-T cell epitopes instigated robust immune response in-silico against Scrub Typhus

Scrub typhus, a potentially life-threatening infectious disease, is attributed to bacteria Orientia tsutsugamushi (O. tsutsugamushi). The transmission of this illness to humans occurs through the bite of infected chiggers, which are the larval forms of mites belonging to the genus Leptotrombidium. In this research, we developed a subunit vaccine specifically designed to target outer membrane proteins. Immunodominant cytotoxic T-lymphocytes (CTLs), B- lymphocytes (BCLs), and major histocompatibility complex (MHC)- II epitopes were identified using machine learning and bioinformatics approaches. These epitopes were arranged in different combinations with the help of suitable linkers like AAY, KK, GPGPG and adjuvant (cholera toxin B) that resulted in a vaccine construct. Physiochemical properties were assessed, where the predicted solubility (0.571) was higher than threshold value. Tertiary structure was predicted using I-TASSER web server and evaluated using Ramachandran plot (94 % residues in most favourable region) and z-score (-6.04), which had shown the structure to have good stability and residue arrangement. Molecular docking with immune receptors, Toll-like receptor (TLR)-2 and -4 showed good residue interaction with 13 and 5 hydrogen bonds respectively. Molecular dynamics simulations of receptor-ligand complex provided the idea about the strong interaction having 1.524751 × 10-5 eigenvalue. Amino acid sequence of vaccine was converted to nucleotide sequence and underwent codon optimization. The optimized codon sequence was used for in-silico cloning, which provided idea about the possibility of synthesis of vaccine using E. coli as host. Overall, this study provided a promising blueprint for a scrub typhus vaccine, although experimental validation is needed for confirmation. Furthermore, it is crucial to acknowledge that while bioinformatics provides valuable insights, in-vitro and in-vivo studies are imperative for a comprehensive evaluation of vaccine candidate. Thus, the integration of computational predictions with empirical research is essential to validate the efficacy, safety, and real-world applicability of the designed vaccine against Scrub Typhus. Nevertheless, the findings are good to carry forward for in-vitro and in-vivo investigations.

Comparative analysis of F-18 FDG PET/CT images between scrub typhus and systemic lupus erythematosus

This study evaluated the use of F-18 fluorodeoxyglucose (FDG) PET/CT imaging to differentiate between scrub typhus and systemic lupus erythematosus (SLE) in patients presenting with lymphadenopathy. We carried out a retrospective analysis of 18 scrub typhus patients and seven SLE patients, using various imaging parameters, including lymph node size, spleen and liver lengths, the distance between the two farthest lesions (Dmax), and assessments of glucose metabolism. On FDG PET images, we measured the maximum standardized uptake value (SUVmax) of the lymph nodes, spleen, and liver and the mean standardized uptake value (SUVmean) of the liver and spleen. The Dmax values of scrub typhus patients were significantly longer than those of SLE patients, indicating that lymphadenopathy is more generalized in the patients with scrub typhus. The SUVmax values for the lymph node, spleen, and liver were also higher in patients with scrub typhus, while the SUVmean of the liver and spleen did not differ between the two groups. This study is the first to compare FDG PET/CT images between these two conditions, suggesting the potential of this imaging modality to provide critical diagnostic distinctions.

A Splenic Infarct in Scrub Typhus: A Rare Entity

Scrub typhus is a zoonotic feverish condition that can range from mild to severe, potentially life-threatening symptoms. Common signs include fever, headache, muscle pain, and a skin rash. Although rare, splenic infarction is a known complication of scrub typhus, with only a limited number of cases documented in medical literature. The case of a 68-year-old male with fever and abdominal discomfort, ultimately diagnosed with both scrub typhus and splenic infarct, illustrates the importance of recognizing splenic infarction as a potential complication of scrub typhus, particularly in areas where the disease is prevalent. The patient was promptly diagnosed and managed with a favorable outcome.

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.

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

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

Magnetic Resonance Imaging Features of Encephalitis of Scrub Typhus

This case report describes the magnetic resonance imaging (MRI) findings and diagnosis of scrub typhus infection in a woman who had recurrent high fever, akinetic mutism, an eschar, and an increase in lymphocytes.

Central nervous system infections in the tropics

PURPOSE OF REVIEW

Emerging and re-emerging central nervous system (CNS) infections are a major public health concern in the tropics. The reasons for this are myriad; climate change, rainfall, deforestation, increased vector density combined with poverty, poor sanitation and hygiene. This review focuses on pathogens, which have emerged and re-emerged, with the potential for significant morbidity and mortality.

RECENT FINDINGS

In recent years, multiple acute encephalitis outbreaks have been caused by Nipah virus, which carries a high case fatality. Arboviral infections, predominantly dengue, chikungunya and Zika are re-emerging increasingly especially in urban areas due to changing human habitats, vector behaviour and viral evolution. Scrub typhus, another vector borne disease caused by the bacterium Orientia tsutsugamushi , is being established as a leading cause of CNS infections in the tropics.

SUMMARY

A syndromic and epidemiological approach to CNS infections in the tropics is essential to plan appropriate diagnostic tests and management. Rapid diagnostic tests facilitate early diagnosis and thus help prompt initiation and focusing of therapy to prevent adverse outcomes. Vector control, cautious urbanization and deforestation, and reducing disturbance of ecosystems can help prevent spread of vector-borne diseases. Regional diagnostic and treatment approaches and specific vaccines are required to avert morbidity and mortality.

Global seroprevalence of scrub typhus: a systematic review and meta-analysis

Scrub typhus, a neglected disease, is a significant health concern in the Tsutsugamushi triangle of the Asia-Pacific and has raised global concerns due to recent cases occurring outside this region. To estimate the global prevalence of scrub typhus, we conducted a systematic review and meta-analysis. We conducted a systematic search of PubMed, Scopus, and Embase databases for observational studies on scrub typhus. Using a random-effects model, we combined the prevalence estimates with inverse-variance weights while also evaluating heterogeneity and publication bias. Among 3551 reports screened, we identified 181 studies with 1,48,251 samples for inclusion in our synthesis. The overall pooled seroprevalence (95% confidence intervals) of scrub typhus infections was 24.93% (23.27-26.60). Gender-wise pooled prevalence was estimated to be 50.23% (47.05-53.40) for males and 48.84% (45.87-51.80) for females. Eschar prevalence was observed to be 30.34% (22.54-38.15) among the positive cases. One-fourth of all the samples tested positive for scrub typhus and eschar was present in one-third of these total positive cases, encompassing regions beyond the Tsutsugamushi triangle. This estimation underlines the importance of this neglected disease as a public health problem. Strengthening surveillance and implementing disease control measures are needed in the affected regions.

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.

Masqueraders Around Disaster: Clinical Features of Scrub Typhus in Fukushima, Japan

Background

Scrub typhus (ST) is endemic in Fukushima, with the largest number of cases reported in Japan from 2009 to 2010. Although ST is highly treatable, its atypical clinical presentation impedes diagnosis, causing delays in treatment.

Methods

We review the clinical features of ST in adults from 2008 to 2017 at Ohta Nishinouchi General Hospital in Fukushima, Japan.

Results

Fifty-five cases (serotype Karp 24, Irie/Kawasaki 21, Hirano/Kuroki 10) of ST were confirmed via serology based on elevated immunoglobulin (Ig)M and IgG and polymerase chain reaction positivity of eschar samples. The mean age was 69 years, and 64% were female. The case fatality rate was 1.8% (1/55). Approximately 70% of cases (38/55) were not diagnosed as ST upon the initial clinic visit. Inappropriate use of antibiotics was identified in 22% of cases (12/55). In terms of atypical clinical features, 1 or more of the manifestations, fever, rash, and eschar, was absent in 31% of cases (17/55). Approximately 11% of cases presented without eschar (6/55; Karp 1, Irie/Kawasaki 1, Hirano/Kuroki 4). Moreover, severe complications were observed with shock and disseminated intravascular coagulation in 7% of cases (4/55), Thus, while 53% of cases presented with the typical triad (29/55), unusual complications and atypical features occurred in 40% (22/55).

Conclusions

Diagnosis of ST becomes clinically challenging in the absence of typical features. In Fukushima, an endemic area of ST, an atypical presentation involving multisystem disease is common.

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.

Development and implementation of a strategy for early diagnosis and management of scrub typhus: an emerging public health threat

Scrub typhus, caused by Orientia tsutsugamushi, is a re-emerging zoonotic disease in the tropics with considerable morbidity and mortality rates. This disease, which is mostly prevalent in rural areas, remains underdiagnosed and underreported because of the low index of suspicion and non-specific clinical presentation. Limited access to healthcare, diagnostics, and treatment in rural settings further makes it challenging to distinguish it from other febrile illnesses. While easily treatable, improper treatment leads to severe forms of the disease and even death. As there is no existing public health program to address scrub typhus in India, there is an urgent need to design a program and test its effectiveness for control and management of the disease. With this backdrop, this implementation research protocol has been developed for a trial in few of the endemic "pockets" of Odisha, an eastern Indian state that can be scalable to other endemic areas of the country, if found effective. The main goal of the proposed project is to include scrub typhus as a differential diagnosis of fever cases in every tier of the public health system, starting from the community level to the health system, for the early diagnosis among suspected cases and to ensure that individuals receive complete treatment. The current study aimed to describe the protocol of the proposed Scrub Typhus Control Program (STCP) in detail so that it can receive valuable views from peers which can further strengthen the attempt.

Pathological Responses in Asian House Shrews (Suncus murinus) to the Naturally Acquired Orientia tsutsugamushi Infection

Scrub typhus is a re-emerging disease caused by Orientia tsutsugamushi, transmitted by mites belonging to the family Trombiculidae. Humans and rodents acquire the infection by the bite of larval mites/chiggers. Suncus murinus, the Asian house shrew, has been reported to harbor the vector mites and has been naturally infected with O. tsutsugamushi. The present study aimed to localize and record O. tsutsugamushi in the tissues and the host response in shrews naturally infected with O. tsutsugamushi. Sheehan's modified May-Grunwald Giemsa staining was carried out in 365 tissues from 87 animals, and rickettsiae were documented in 87 tissues from 20 animals. Immunohistochemical (IHC) staining, using polyclonal antibodies raised against selected epitopes of the 56-kDa antigen, was carried out, and 81/87 tissue sections were tested positive for O. tsutsugamushi. By IHC, in addition to the endothelium, the pathogen was also demonstrated by IHC in cardiomyocytes, the bronchiolar epithelium, stroma of the lungs, hepatocytes, the bile duct epithelium, the epithelium and goblet cells of intestine, the tubular epithelium of the kidney, and splenic macrophages. Furthermore, the pathogen was confirmed by real-time PCR using blood (n = 20) and tissues (n = 81) of the IHC-positive animals. None of the blood samples and only 22 out of 81 IHC-positive tissues were tested positive by PCR. By nucleotide sequencing of the 56-kDa gene, Gilliam and Karp strains were found circulating among these animals. Although these bacterial strains are highly virulent and cause a wide range of pathological alterations, hence exploring their adaptive mechanisms of survival in shrews will be of significance. Given that the pathogen localizes in various organs following a transient bacteremia, we recommend the inclusion of tissues from the heart, lung, intestine, and kidney of reservoir animals, in addition to blood samples, for future molecular surveillance of scrub typhus.

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

CONTEXT

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

CASE REPORT

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

CONCLUSION

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

Scrub typhus in Northeast India: epidemiology, clinical presentations, and diagnostic approaches

Scrub typhus is one of the most neglected tropical diseases, a leading cause of acute undifferentiated febrile illness in areas of the 'tsutsugamushi triangle', diagnosed frequently in South Asian countries. The bacteria Orientia tsutsugamushi is the causative agent of the disease, which enters the human body through the bite of trombiculid mites (also known as chiggers) of the genus Leptotrombidium deliense. Diagnosis of the disease is challenging, as its early symptoms mimic other febrile illnesses like dengue, influenza and corona viruses. Lack of rapid, reliable and cost-effective diagnostic methods further complicates the identification process. Northeast India, a mountainous region with a predominantly rural tribal population, has witnessed a resurgence of scrub typhus cases in recent years. Various ecological factors, including rodent populations, habitat characteristics and climatic conditions, influence its prevalence. Entomological investigations have confirmed the abundance of vector mites, highlighting the importance of understanding their distribution and the probability of transmission of scrub typhus in the region. Proper diagnosis, awareness campaigns and behavioural interventions are essential for controlling scrub typhus outbreaks and reducing its impact on public health in Northeast India. Further research and community-based studies are necessary to accurately assess the disease burden and implement effective prevention strategies.

Changing epidemiologic patterns of typhus group rickettsiosis and scrub typhus in China, 1950-2022

OBJECTIVES

We conducted a systematic analysis of the notifiable rickettsial diseases in humans in China during 1950-2022.

METHODS

We utilized descriptive statistics to analyze the epidemiological characteristics, clinical manifestations, and diagnostic characteristics of typhus group rickettsiosis (TGR) and scrub typhus (ST) cases.

RESULTS

Since the 1950s, there have been variations in the incidence rate of TGR and ST in China, with a downtrend for TGR and an uptrend for ST. The South became a high-incidence area of TGR, whereas the North was previously the high-incidence area. ST cases were concentrated in the South and the geographic area of ST spread northward and westward. The seasonality of TGR and ST were similar in the South but distinct in the North. Most TGR and ST cases were reported by county-level medical institutions, whereas primary institutions reported the least. Delayed diagnosis was associated with fatal outcomes of TGR and ST. Cases in low-incidence provinces, confirmed by laboratory tests and reported from county/municipal-level institutions had higher odds of delayed diagnoses.

CONCLUSIONS

Our study revealed significant changes in the epidemiological characteristics of TGR and ST in China, which can provide useful information to enhance the control and prevention strategies of rickettsial diseases in China.

Epidemiological and clinical characteristics of scrub typhus in Guizhou Province, China: An outbreak study of scrub typhus

The reported cases of scrub typhus (ST) have continued to escalate, with outbreaks occurring regionally in China. These pose an increasing public health threat at a time when public health has been overwhelmed. During the period from July to August 2022, in Rongjiang County, Guizhou Province, China, 13 out of 21 fever patients were diagnosed with scrub typhus, based on epidemiological investigation and blood test analysis. The major clinical symptoms of these patients showed fever, chills, headache, eschar, fatigue and pneumonia, which were accompanied by a rise in C-reactive protein, neutrophils, alanine transaminase (ALT) and aspartate aminotransferase (AST). Furthermore, nearly half of them exhibited abnormal electrocardiogram activity. Through semi-nested PCR, Sanger sequencing and phylogenetic tree construction, the Karp strain of Orientia tsutsugamushi (O. tsutsugamushi) was confirmed as the pathogen causing ST in Rongjiang County, which shared the same evolutionary branch with O. tsutsugamushi isolated from wild mouse liver or spleen, indicating that the wild mouse plays an important role in transmitting the disease. In contrast to the sporadic cases in the past, our study is the first to disclose an epidemic and the corresponding clinical characteristics of ST in Guizhou province, which is of great significance for the prevention and treatment of regional illnesses.

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

BACKGROUND AND AIMS

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

METHODS

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

RESULTS

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

INTERPRETATION

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

Molecular detection of Orientia tsutsugamushi in ectoparasites & their small mammal hosts captured from scrub typhus endemic areas in Madurai district, India

BACKGROUND OBJECTIVES

Scrub typhus, caused by Orientia tsutsugamushi present in small mammals harbouring the ectoparasites. A study was undertaken to detect the pathogen present in small mammals and its ectoparasites in the scrub typhus-reported areas.

METHODS

The small mammals (rodents/shrews) and its ectoparasites were screened for O. tsutsugamushi using nested PCR amplification of the groEL gene. Small mammals were collected by trapping and screened for ectoparasites (mites, ticks and fleas) by combing method.

RESULTS

All the chigger mites collected were tested negative for O. tsutsugamushi . Interestingly, adult non-trombiculid mites ( Oribatida sp., Dermanyssus gallinae ), fleas ( Xenopsylla astia, X. cheopis, Ctenophalides felis and Ctenophalides sp.) and ticks ( Rhipicephalus sanguineus , R. haemaphysaloides ) screened were found to be positive for O. tsutsugamushi , which the authors believe is the first report on these species globally. Bandicota bengalensis with O. tsutsugamushi infection is reported for the first time in India. The O. tsutsugamushi groEL sequences from the positive samples were similar to the reference strains, Karp and Ikeda and phylogenetically clustered in clade IV with less evolutionary divergence. The blood samples of Rattus rattus , Suncus murinus and B. bengalensis collected from this area were tested positive for O. tsutsugamushi ; interestingly, the sequence similarity was much pronounced with their ectoparasites indicating the transmission of the pathogen to host or vice versa .

INTERPRETATION CONCLUSIONS

The outcome of the present investigations widened our scope on the pathogens present in ectoparasites and rodents/shrews from this area. This will help to formulate the required vector control methods to combat zoonotic diseases.

Analysis of Differences in Characteristics of High-Risk Endemic Areas for Contracting Japanese Spotted Fever, Tsutsugamushi Disease, and Severe Fever With Thrombocytopenia Syndrome

Background

Tick-borne infections, including tsutsugamushi disease, Japanese spotted fever, and severe fever with thrombocytopenia syndrome (SFTS), are prevalent in East Asia with varying geographic distribution and seasonality. This study aimed to investigate the differences in the characteristics among endemic areas for contracting each infection.

Methods

We conducted an ecologic study in Japan, using data from a nationwide inpatient database and publicly available geospatial data. We identified 4493 patients who were hospitalized for tick-borne infections between July 2010 and March 2021. Mixed-effects modified Poisson regression analysis was used to identify factors associated with a higher risk of contracting each tick-borne disease (Tsutsugamushi, Japanese spotted fever, and SFTS).

Results

Mixed-effects modified Poisson regression analysis revealed that environmental factors, such as temperature, sunlight duration, elevation, precipitation, and vegetation, were associated with the risk of contracting these diseases. Tsutsugamushi disease was positively associated with higher temperatures, farms, and forests, whereas Japanese spotted fever and SFTS were positively associated with higher solar radiation and forests.

Conclusions

Our findings from this ecologic study indicate that different environmental factors play a significant role in the risk of transmission of tick-borne infections. Understanding the differences can aid in identifying high-risk areas and developing public health strategies for infection prevention. Further research is needed to address causal relationships.

Spontaneous splenic rupture associated with scrub typhus: a case report

BACKGROUND

Scrub typhus, an acute febrile disease with mild to severe, life-threatening manifestations, potentially presents with a variety of complications, including pneumonia, acute respiratory distress syndrome, cardiac arrhythmias (such as atrial fibrillation), myocarditis, shock, peptic ulcer, gastrointestinal bleeding, meningitis, encephalitis, and renal failure. Of the various complications associated with scrub typhus, splenic rupture has rarely been reported, and its mechanisms are unknown. This study reports a case of scrub typhus-related spontaneous splenic rupture and identifies possible mechanisms through the gross and histopathologic findings.

CASE PRESENTATION

A 78-year-old man presented to our emergency room with a 5-day history of fever and skin rash. On physical examination, eschar was observed on the left upper abdominal quadrant. The abdomen was not tender, and there was no history of trauma. The Orientia tsutsugamushi antibody titer using the indirect immunofluorescent antibody test was 1:640. On Day 6 of hospitalization, he complained of sudden-onset left upper abdominal quadrant pain and showed mental changes. His vital signs were a blood pressure of 70/40 mmHg, a heart rate pf 140 beats per min, and a respiratory rate of 20 breaths per min, with a temperature of 36.8 °C. There were no signs of gastrointestinal bleeding, such as hematemesis, melena, or hematochezia. Grey Turner's sign was suspected during an abdominal examination. Portable ultrasonography showed retroperitoneal bleeding, so an emergency exploratory laparotomy was performed, leading to a diagnosis of hemoperitoneum due to splenic rupture and a splenectomy. The patient had been taking oral doxycycline (100 mg twice daily) for 6 days; after surgery, this was discontinued, and intravenous azithromycin (500 mg daily) was administered. No arrhythmia associated with azithromycin was observed. However, renal failure with hemodialysis, persistent hyperbilirubinemia, and multiorgan failure occurred. The patient did not recover and died on the fifty-sixth day of hospitalization.

CONCLUSIONS

Clinicians should consider the possibility of splenic rupture in patients with scrub typhus who display sudden-onset abdominal pain and unstable vital signs. In addition, splenic capsular rupture and extra-capsular hemorrhage are thought to be caused by splenomegaly and capsular distention resulting from red blood cell congestion in the red pulp destroying the splenic sinus.