Epidemiology and clinical aspects of rickettsioses in Thailand

Clinical Profile and Long-Term Outcomes of Scrub Typhus Meningoencephalitis in Children

INTRODUCTION

Scrub typhus is a significant cause of acute encephalitis syndrome (AES) in pediatric populations, particularly in northern India. Its long-term outcomes have not been well studied to date. This study investigates the clinical profile and long-term outcomes of scrub typhus meningoencephalitis in children.

METHODS

This prospective observational study was conducted at King George's Medical University, Uttar Pradesh, India, from August 2018 to October 2020. Children aged 0.3 months to 14 years who presented with AES were tested for scrub typhus using serum IgM Enzyme-Linked Immunosorbent Assay (ELISA) and polymerase chain reaction (PCR) of cerebrospinal fluid (CSF) and peripheral blood mononuclear cells (PBMC). Positive patients were followed up for one year to assess long-term neurological outcomes.

RESULTS

Of 264 children tested for scrub typhus, 78 (29.5%) were positive. Neurological symptoms included altered sensorium (70 (89.74%)), seizures (69 (88.46%)), and focal neurological deficits 8 (10.26%). Hepato-splenomegaly (27 (34.61%)), thrombocytopenia (48 (61.5%)), and raised liver transaminases (51 (65.4%)) were the other common manifestations. Mortality occurred in 10.25% of cases. Sixty-seven cases were followed up for one year. Long-term outcomes indicated that 60 (89.55%) of the patients fully recovered, while seven (10.45%) experienced sequelae, including minor impairment in four (5.97%), moderate impairment in two (2.99%), and severe impairment in one case (1.49%).

CONCLUSION

Scrub typhus is a major cause of AES in children, with significant neurological sequelae in a small number of cases.

Epidemiologic changes of a longitudinal surveillance study spanning 51 years of scrub typhus in mainland China

Scrub typhus may be one of the world's most prevalent, neglected and serious, but easily treatable, febrile diseases. It has become a significant potential threat to public health in China. In this study we used national disease surveillance data to analyze the incidence and spatial-temporal distribution of scrub typhus in mainland China during 1952-1989 and 2006-2018. Descriptive epidemiological methods and spatial-temporal epidemiological methods were used to investigate the epidemiological trends and identify high-risk regions of scrub typhus infection. Over the 51-year period, a total of 182,991 cases and 186 deaths were notified. The average annual incidence was 0.13 cases/100,000 population during 1952-1989. The incidence increased sharply from 0.09/100,000 population in 2006 to 1.93/100,000 population in 2018 and then exponentially increased after 2006. The incidence was significantly higher in females than males (χ2 = 426.32, P < 0.001). Farmers had a higher incidence of scrub typhus than non-farmers (χ2 = 684.58, P < 0.001). The majority of cases each year were reported between July and November with peak incidence occurring during October each year. The trend surface analysis showed that the incidence of scrub typhus increased gradually from north to south, and from east and west to the central area. The spatial autocorrelation analysis showed that a spatial positive correlation existed in the prevalence of scrub typhus on a national scale, which had the characteristic of aggregated distribution (I = 0.533, P < 0.05). LISA analysis showed hotspots (High-High) were primarily located in the southern and southwestern provinces of China with the geographical area expanding annually. These findings provide scientific evidence for the surveillance and control of scrub typhus which may contribute to targeted strategies and measures for the government.

A systematic review of neglected tropical diseases (NTDs) in Myanmar

BACKGROUND

Neglected tropical diseases (NTDs) affect most impoverished communities in developing countries, like Myanmar in Southeast Asia. NTDs have been understudied and underreported in Myanmar.

METHODS

A systematic review of published and grey literature (1900-2023) on neglected tropical diseases (NTDs) in Myanmar was conducted. The literature search included five international databases: PubMed, EMBASE, Ovid Global Health, and Web of Science Core Collection and one national database: the Myanmar Central Biomedical Library (locally published papers and grey literature). The selection criteria included articles with all types of study designs of current or previous infections conducted in humans, that reported NTDs, recognised by WHO, US CDC, and listed in PLoS NTDs. We included melioidosis and rickettsioses which we consider also meet the definition of an NTD.

RESULTS

A total of 5941 records were retrieved and screened, of which, 672 (11%) met the selection criteria and were included in this review. Of the included articles, 449 (65%) were published after 2000 and 369 (55%) were from two regions (Yangon and Mandalay) of Myanmar. Of the included articles, 238 (35%) reported bacterial NTDs, 212 (32%) viral NTDs, 153 (23%) helminth NTDs, 25 (4%) protozoal NTDs and 39 (6%) reported more than one aetiology. Based on reported frequency in descending order, the bacterial NTDs were leprosy, Escherichia coli enteritis, salmonellosis, cholera, shigellosis, melioidosis, leptospirosis and rickettsioses; the viral NTDs were dengue, chikungunya and Japanese encephalitis virus (JEV) infection; the protozoal NTDs were amoebiasis, giardiasis and leishmaniasis, and the helminth NTDs were ascariasis, trichuriasis, hookworm disease, filariasis and strongyloidiasis.

CONCLUSION

This review summarises NTDs reported in Myanmar over the past 100 years. The findings suggest that most NTDs are likely to be under reported, especially from the majority of the country which is far from academic centres. Research capacity building together with strengthening of laboratory systems would lead to better understanding of the true burden of NTDs in Myanmar.

TRIAL REGISTRATION

PROSPERO registration ID: CRD42018092627.

Epidemiology, clinical characteristics, diagnosis, and complications of scrub typhus infection in Nepal: a systematic review

Introduction

Scrub typhus (ST) is a neglected tropical disease of serious concern in Nepal. This systematic review aims to describe the burden of disease, clinical presentation, and complications of ST infection in Nepal.

Methods

A systematic search of PubMed, EMBASE, Google Scholar, and national databases was conducted for any literature published in English between January 2000 and January 2023. Any type of study design (observational studies, case series, and interventional studies) that reported laboratory-confirmed ST and was conducted in Nepal among patients of all age groups was included. The seroprevalence of ST among acute undifferentiated febrile illness (AUFI) cases, geographical distribution, monthly distribution, clinical presentations, complications, and treatment were assessed by the study.

Result

A total of 15 studies with 10, 977 participants were included in the review. The seroprevalence of ST among the AUFI cases in Nepal was 19.31%. Young people at or below 20 years of age were mostly affected. The maximum number of cases were reported from Bagmati province (59.46%) and in the month of August (26.33%). Fever, headache, cough, shortness of breath, nausea, and abdominal pain were the clinical characteristics in decreasing order of occurrence. The most common complication was acute kidney injury, followed by respiratory problems, cardiac issues, and neurological manifestations. The case fatality rate of ST in Nepal was 2.56%.

Conclusion

The authors findings showed a significant burden of ST among AUFI cases in Nepal. Improved surveillance, general public awareness, and early detection post-calamities could help reduce the disease burden and improve patient outcomes.

Recent Threat of Scrub Typhus in India: A Narrative Review

Scrub typhus is an endemic illness transmitted by vectors and induced by bacteria. It is the most common and severe rickettsial disease. There are many more cases every year with a significant case fatality rate. Despite being a serious public health threat in India, it is uncertain how widespread and burdensome scrub typhus is. The scarcity of statistical information and pertinent health records on scrub typhus in the outbreak region demonstrates that there is still a significant knowledge gap about this neglected illness. Clinical manifestations of this illness include kidney failure, disability, and severe kidney failure. Undifferentiated symptoms, late diagnosis, and treatment failure are all responsible for deaths. Knowing about this disease is important from a public health point of view due to difficulties in specific diagnosis and a shortage of laboratory services in so many places. India is known to have scrub typhus cases, and doctors should be aware of this potentially dangerous but easily curable illness. The disease is highly difficult to identify clinically from other acute afebrile infections due to common symptoms and a paucity of the lesion in the Indian population. The mainstay of diagnosis is antibody-based serological testing. Within the first week of symptoms, scrub typhus can be diagnosed using molecular and serological tests. Our objective is to identify how severe scrub typhus is in India and to investigate the current epidemiology, etiology, complications, management, and treatment of the disease in both long-established endemic regions and new infection foci.

Risk factors analysis for neglected human rickettsioses in rural communities in Nan province, Thailand: A community-based observational study along a landscape gradient

In this study, we estimated exposure for Scrub typhus (STG), Typhus (TG) and Spotted fever groups (SFG) rickettsia using serology at a fine scale (a whole sub-district administration level) of local communities in Nan Province, Thailand. Geographical characteristics of the sub-district were divided into two landscape types: lowland agricultural area in an urbanized setting (lowland-urbanized area) and upland agricultural area located close to a protected area of National Park (upland-forested area). This provided an ideal contrast between the two landscapes with low and high levels of human-altered habitats to study in differences in disease ecology. In total, 824 serum samples of participants residing in the eight villages were tested by screening IgG ELISA, and subsequently confirmed by the gold standard IgG Immunofluorescent Assay (IFA). STG and TG IgG positivity were highest with seroprevalence of 9.8% and 9.0%, respectively; whereas SFG positivity was lower at 6.9%. Inhabitants from the villages located in upland-forested area demonstrated significantly higher STG exposure, compared to those villages in the lowland-urbanized area (chi-square = 51.97, p < 0.0001). In contrast, TG exposure was significantly higher in those villagers living in lowland-urbanized area (chi-square = 28.26, p < 0.0001). In addition to the effect of landscape types, generalized linear model (GLM) analysis identified socio-demographic parameters, i.e., gender, occupation, age, educational level, domestic animal ownership (dog, cattle and poultry) as influential factors to explain the level of rickettsial exposure (antibody titers) in the communities. Our findings raise the public health awareness of rickettsiosis as a cause of undiagnosed febrile illness in the communities.

Evidence of human exposures to rickettsial pathogens were reported from a cross-sectional study at a whole sub-district scale of local communities in Nan Province, Thailand. Seroprevalence and level of rickettsial exposures demonstrated differences between the habitat types, ecological aspects and socio-demographic factors. In addition, abundance of domestic animals in the community appeared to be one of significant factors influencing levels of human exposure to rickettsial pathogens. Our findings will benefit the local public health by raising awareness of rickettsial infections as one of potential health concerns in the community. Inclusion of rickettsioses in routine laboratory diagnosis would help to differentiate unknown febrile illness and guide appropriate treatment. Further studies are required, particularly in the fields of disease ecology as well as medical and veterinary entomology, in order to better understand epidemiology and potential zoonotic transmission of these neglected rickettsioses in endemic areas.

Rickettsiosis in Southeast Asia: Summary for International Travellers during the COVID-19 Pandemic

Rickettsiosis is an important cause of febrile illness among travellers visiting Southeast Asia (SEA). The true incidence of rickettsiosis is underestimated; however, murine typhus and scrub typhus are widely distributed across SEA. Among travellers visiting SEA, scrub typhus was mostly reported from Thailand, whereas murine typhus was frequently found in Indonesia. Although most cases are self-limited or present with mild symptoms, a few cases with severe clinical manifestations have been reported. Doxycycline remains the key treatment of rickettsiosis. Some travellers, such as backpackers, trekkers, or cave explorers, are at a higher risk for rickettsiosis than others. Therefore, in resource-limited conditions, empirical treatment should be considered in these travellers. The coronavirus disease 2019 (COVID-19) pandemic has contributed to difficulty in the diagnosis of rickettsiosis because of the clinical similarities between these diseases. In addition, physical distancing mandated by COVID-19 management guidelines limits accurate physical examination, resulting in misdiagnosis and delayed treatment of rickettsiosis. This review summarises the characteristics of murine typhus and scrub typhus, describes travel-associated rickettsiosis, and discusses the impact of the COVID-19 pandemic on rickettsiosis.

Vaccine Design and Vaccination Strategies against Rickettsiae

Rickettsioses are febrile, potentially lethal infectious diseases that are a serious health threat, especially in poor income countries. The causative agents are small obligate intracellular bacteria, rickettsiae. Rickettsial infections are emerging worldwide with increasing incidence and geographic distribution. Nonetheless, these infections are clearly underdiagnosed because methods of diagnosis are still limited and often not available. Another problem is that the bacteria respond to only a few antibiotics, so delayed or wrong antibiotic treatment often leads to a more severe outcome of the disease. In addition to that, the development of antibiotic resistance is a serious threat because alternative antibiotics are missing. For these reasons, prophylactic vaccines against rickettsiae are urgently needed. In the past years, knowledge about protective immunity against rickettsiae and immunogenic determinants has been increasing and provides a basis for vaccine development against these bacterial pathogens. This review provides an overview of experimental vaccination approaches against rickettsial infections and perspectives on vaccination strategies.

GroEL is an immunodominant surface-exposed antigen of Rickettsia typhi

Rickettsioses are neglected and emerging potentially fatal febrile diseases that are caused by obligate intracellular bacteria, rickettsiae. Rickettsia (R.) typhi and R. prowazekii constitute the typhus group (TG) of rickettsiae and are the causative agents of endemic and epidemic typhus, respectively. We recently generated a monoclonal antibody (BNI52) against R. typhi. Characterization of BNI52 revealed that it specifically recognizes TG rickettsiae but not the members of the spotted fever group (SFG) rickettsiae. We further show that BNI52 binds to protein fragments of ±30 kDa that are exposed on the bacterial surface and also present in the periplasmic space. These protein fragments apparently derive from the cytosolic GroEL protein of R. typhi and are also recognized by antibodies in the sera from patients and infected mice. Furthermore, BNI52 opsonizes the bacteria for the uptake by antigen presenting cells (APC), indicating a contribution of GroEL-specific antibodies to protective immunity. Finally, it is interesting that the GroEL protein belongs to 32 proteins that are differentially downregulated by R. typhi after passage through immunodeficient BALB/c CB17 SCID mice. This could be a hint that the rickettsia GroEL protein may have immunomodulatory properties as shown for the homologous protein from several other bacteria, too. Overall, the results of this study provide evidence that GroEL represents an immunodominant antigen of TG rickettsiae that is recognized by the humoral immune response against these pathogens and that may be interesting as a vaccine candidate. Apart from that, the BNI52 antibody represents a new tool for specific detection of TG rickettsiae in various diagnostic and experimental setups.

Non-linear effect of different humidity types on scrub typhus occurrence in endemic provinces, Thailand

Background

Reported monthly scrub typhus (ST) cases in Thailand has an increase in the number of cases during 2009–2014. Humidity is a crucial climatic factor for the survival of chiggers, which is the disease vectors. The present study was to determine the role of humidity in ST occurrence in Thailand and its delayed effect.

Methods

We obtained the climate data from the Department of Meteorology, the disease data from Ministry of Public Health. Negative binomial regression combined with a distributed lag non-linear model (NB-DLNM) was employed to determine the non-linear effects of different types of humidity on the disease. This model controlled overdispersion and confounder, including seasonality, minimum temperature, and cumulative total rainwater.

Results

The occurrence of the disease in the 6-year period showed the number of cases gradually increased summer season (Mid-February – Mid-May) and then reached a plateau during the rainy season (Mid-May – Mid-October) and then steep fall after the cold season (Mid-October – Mid-February). The high level (at 70%) of minimum relative humidity (RHmin) was associated with a 33% (RR 1.33, 95% CI 1.13–1.57) significant increase in the number of the disease; a high level (at 14 g/m³) of minimum absolute humidity (AHmin) was associated with a 30% (RR 1.30, 95% CI 1.14–1.48); a high level (at 1.4 g/kg) of minimum specific humidity (SHmin) was associated with a 28% (RR 1.28, 95% CI 1.04–1.57). The significant effects of these types of humidity occurred within the past month.

Conclusion

Humidity played a significant role in enhancing ST cases in Thailand, particularly at a high level and usually occurred within the past month. NB-DLNM had good controlled for the overdispersion and provided the precise estimated relative risk of non-linear associations. Results from this study contributed the evidence to support the Ministry of Public Health on warning system which might be useful for public health intervention and preparation in Thailand.

Orientia tsutsugamushi: The dangerous yet neglected foe from the East

Orientia tsutsugamushi (OT), the causative agent of the vector-borne Scrub typhus zoonotic disease in humans, is a unique microorganism that exists in the Asia-Pacific region since a long time. In spite of its occurrence, the organism had been neglected until recent years. Humans are the accidental dead-end hosts of O. tsutsugamushi and display manifestations which are both severe and misleading. The vast antigenic diversity of OT and non-pathognomic symptoms of Scrub typhus, create hurdles in the clinical management of the disease and impede the OT-research. Many countries in the Asia-Pacific region have reported the resurgence of OT- infections and have raised concerns for its expanding distribution. This has triggered the development of advanced techniques for diagnosis and research on exploring a successful vaccine candidate to reduce the burden of the disease. Thus, the aim of this systematic review is to provide an update on the recent advances in the OT-research and highlight the key areas that have remained obscure and demand attention.

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.

Rickettsioses as Major Etiologies of Unrecognized Acute Febrile Illness, Sabah, East Malaysia

Orientia tsutsugamushi, spotted fever group rickettsioses, and typhus group rickettsioses (TGR) are reemerging causes of acute febrile illness (AFI) in Southeast Asia. To further delineate extent, we enrolled patients >4 weeks of age with nonmalarial AFI in Sabah, Malaysia, during 2013-2015. We confirmed rickettsioses (past or acute, IgG titer >160) in 126/354 (36%) patients. We confirmed acute rickettsioses (paired 4-fold IgG titer rise to >160) in 38/145 (26%) patients: 23 O. tsutsugamushi, 9 spotted fever group, 4 TGR, 1 O. tsutsugamushi/spotted fever group, and 1 O. tsutsugamushi/TGR. PCR results were positive in 11/319 (3%) patients. Confirmed rickettsioses were more common in male adults; agricultural/plantation work and recent forest exposure were risk factors. Dizziness and acute hearing loss but not eschars were reported more often with acute rickettsioses. Only 2 patients were treated with doxycycline. Acute rickettsioses are common (>26%), underrecognized, and untreated etiologies of AFI in East Malaysia; empirical doxycycline treatment should be considered.

Underdiagnoses of Rickettsia in patients hospitalized with acute fever in Indonesia: observational study results

BACKGROUND

Reports of human rickettsial infection in Indonesia are limited. This study sought to characterize the epidemiology of human rickettsioses amongst patients hospitalized with fever at 8 tertiary hospitals in Indonesia.

METHODS

Acute and convalescent blood from 975 hospitalized non-dengue patients was tested for Rickettsia IgM and IgG by ELISA. Specimens from cases with seroconversion or increasing IgM and/or IgG titers were tested for Rickettsia IgM and IgG by IFA and Rickettsia genomes using primers for Rickettsia (R.) sp, R. typhi, and Orientia tsutsugamushi. Testing was performed retrospectively on stored specimens; results did not inform patient management.

RESULTS

R. typhi, R. rickettsii, and O. tsutsugamushi IgG antibodies were identified in 269/872 (30.8%), 36/634 (5.7%), and 19/504 (3.8%) of samples, respectively. For the 103/975 (10.6%) non-dengue patients diagnosed with acute rickettsial infection, presenting symptoms included nausea (72%), headache (69%), vomiting (43%), lethargy (33%), anorexia (32%), arthralgia (30%), myalgia (28%), chills (28%), epigastric pain (28%), and rash (17%). No acute rickettsioses cases were suspected during hospitalization. Discharge diagnoses included typhoid fever (44), dengue fever (20), respiratory infections (7), leptospirosis (6), unknown fever (6), sepsis (5), hepatobiliary infections (3), UTI (3), and others (9). Fatalities occurred in 7 (6.8%) patients, mostly with co-morbidities.

CONCLUSIONS

Rickettsial infections are consistently misdiagnosed, often as leptospirosis, dengue, or Salmonella typhi infection. Clinicians should include rickettsioses in their differential diagnosis of fever to guide empiric management; laboratories should support evaluation for rickettsial etiologies; and public policy should be implemented to reduce burden of disease.

The estimated burden of scrub typhus in Thailand from national surveillance data (2003-2018)

BACKGROUND

Scrub typhus is a major cause of acute febrile illness in the tropics and is endemic over large areas of the Asia Pacific region. The national and global burden of scrub typhus remains unclear due to limited data and difficulties surrounding diagnosis.

METHODOLOGY/PRINCIPAL FINDINGS

Scrub typhus reporting data from 2003-2018 were collected from the Thai national disease surveillance system. Additional information including the district, sub-district and village of residence, population, geographical, meteorological and satellite imagery data were also collected for Chiangrai, the province with the highest number of reported cases from 2003-2018. From 2003-2018, 103,345 cases of scrub typhus were reported with the number of reported cases increasing substantially over the observed period. There were more men than women, with agricultural workers the main occupational group affected. The majority of cases occurred in the 15-64 year old age group (72,144/99,543, 72%). Disease burden was greatest in the northern region, accounting for 53% of the total reported cases per year (mean). In the northern region, five provinces-Chiangrai, Chiangmai, Tak, Nan and Mae Hong Son-accounted for 84% (46,927/55,872) of the total cases from the northern region or 45% (46,927/103,345) of cases nationally. The majority of cases occurred from June to November but seasonality was less marked in the southern region. In Chiangrai province, elevation, rainfall, temperature, population size, habitat complexity and diversity of land cover contributed to scrub typhus incidence.

INTERPRETATION

The burden of scrub typhus in Thailand is high with disease incidence rising significantly over the last two decades. However, disease burden is not uniform with northern provinces particularly affected. Agricultural activity along with geographical, meteorological and land cover factors are likely to contribute to disease incidence. Our report, along with existing epidemiological data, suggests that scrub typhus is the most clinically important rickettsial disease globally.

Etiologies of Acute Undifferentiated Febrile Illness in Bangkok, Thailand

Acute undifferentiated febrile illness (AUFI) has been a diagnostic dilemma in the tropics. Without accurate point-of-care tests, information on local pathogens and clinical parameters is essential for presumptive diagnosis. A prospective hospital-based study was conducted at the Bangkok Hospital for Tropical Diseases from 2013 to 2015 to determine common etiologies of AUFI. A total of 397 adult AUFI cases, excluding malaria by blood smear, were enrolled. Rapid diagnostic tests for tropical infections were performed on admission, and acute and convalescent samples were tested to confirm the diagnosis. Etiologies could be identified in 271 (68.3%) cases. Dengue was the most common cause, with 157 cases (39.6%), followed by murine typhus (20 cases; 5.0%), leptospirosis (16 cases; 4.0%), influenza (14 cases; 3.5%), and bacteremia (six cases; 1.5%). Concurrent infection by at least two pathogens was reported in 37 cases (9.3%). Furthermore, characteristics of dengue and bacterial infections (including leptospirosis and rickettsioses) were compared to facilitate dengue triage, initiate early antibiotic treatment, and minimize unnecessary use of antibiotics. In conclusion, dengue was the most common pathogen for AUFI in urban Thailand. However, murine typhus and leptospirosis were not uncommon. Empirical antibiotic treatment using doxycycline or azithromycin might be more appropriate, but cost-benefit studies are required. Physicians should recognize common causes of AUFI in their localities and use clinical and laboratory clues for provisional diagnosis to provide appropriate treatment while awaiting laboratory confirmation.

Research Progress on Leptotrombidium deliense

This article reviews Leptotrombidium deliense, including its discovery and nomenclature, morphological features and identification, life cycle, ecology, relationship with diseases, chromosomes and artificial cultivation. The first record of L. deliense was early in 1922 by Walch. Under the genus Leptotrombidium, there are many sibling species similar to L. deliense, which makes it difficult to differentiate L. deliense from another sibling chigger mites, for example, L. rubellum. The life cycle of the mite (L. deliense) includes 7 stages: egg, deutovum (or prelarva), larva, nymphochrysalis, nymph, imagochrysalis and adult. The mite has a wide geographical distribution with low host specificity, and it often appears in different regions and habitats and on many species of hosts. As a vector species of chigger mite, L. deliense is of great importance in transmitting scrub typhus (tsutsugamushi disease) in many parts of the world, especially in tropical regions of Southeast Asia. The seasonal fluctuation of the mite population varies in different geographical regions. The mite has been successfully cultured in the laboratory, facilitating research on its chromosomes, biochemistry and molecular biology.

Causes of acute undifferentiated fever and the utility of biomarkers in Chiangrai, northern Thailand

BACKGROUND

Tropical infectious diseases like dengue, scrub typhus, murine typhus, leptospirosis, and enteric fever continue to contribute substantially to the febrile disease burden throughout Southeast Asia while malaria is declining. Recently, there has been increasing focus on biomarkers (i.e. C-reactive protein (CRP) and procalcitonin) in delineating bacterial from viral infections.

METHODOLOGY/PRINCIPAL FINDINGS

A prospective observational study was performed to investigate the causes of acute undifferentiated fever (AUF) in adults admitted to Chiangrai Prachanukroh hospital, northern Thailand, which included an evaluation of CRP and procalcitonin as diagnostic tools. In total, 200 patients with AUF were recruited. Scrub typhus was the leading bacterial cause of AUF (45/200, 22.5%) followed by leptospirosis (15/200, 7.5%) and murine typhus (7/200, 3.5%), while dengue was the leading viral cause (23/200, 11.5%). Bloodstream infections contributed to 7/200 (3.5%) of the study cohort. There were 9 deaths during this study (4.5%): 3 cases of scrub typhus, 2 with septicaemia (Talaromyces marneffei and Haemophilus influenzae), and 4 of unknown aetiologies. Rickettsioses, leptospirosis and culture-attributed bacterial infections, received a combination of 3rd generation cephalosporin plus a rickettsia-active drug in 53%, 73% and 67% of cases, respectively. Low CRP and white blood count were significant predictors of a viral infection (mainly dengue) while the presence of an eschar and elevated aspartate aminotransferase and alkaline phosphatase were important predictors of scrub typhus.

INTERPRETATION

Scrub typhus and dengue are the leading causes of AUF in Chiangrai, Thailand. Eschar, white blood count and CRP were beneficial in differentiating between bacterial and viral infections in this study. CRP outperformed procalcitonin although cut-offs for positivity require further assessment. The study provides evidence that accurate, pathogen-specific rapid diagnostic tests coupled with biomarker point-of-care tests such as CRP can inform the correct use of antibiotics and improve antimicrobial stewardship in this setting.

A review of the global epidemiology of scrub typhus

Scrub typhus is a serious public health problem in the Asia-Pacific area. It threatens one billion people globally, and causes illness in one million people each year. Caused by Orientia tsutsugamushi, scrub typhus can result in severe multiorgan failure with a case fatality rate up to 70% without appropriate treatment. The antigenic heterogeneity of O. tsutsugamushi precludes generic immunity and allows reinfection. As a neglected disease, there is still a large gap in our knowledge of the disease, as evidenced by the sporadic epidemiologic data and other related public health information regarding scrub typhus in its endemic areas. Our objective is to provide a systematic analysis of current epidemiology, prevention and control of scrub typhus in its long-standing endemic areas and recently recognized foci of infection.

An ELISA assay using a combination of recombinant proteins from multiple strains of Orientia tsutsugamushi offers an accurate diagnosis for scrub typhus

Background

Scrub typhus (ST) is a disease caused by an obligate intracellular bacterium, Orientia tsutsugamushi, an organism that requires a BSL3 laboratory for propagation. The disease is hallmarked by an eschar at the site of the chigger bite, followed by the development of fever, malaise, myalgia, anorexia, and papulomacular rash. Indirect immunofluorescent assay (IFA) is the gold standard for scrub typhus diagnosis, however, the subjectivity of the assay, the need for a specialized laboratory and instruments has limited the wide use of the test in resource limited areas.

Methods

A recombinant-protein based enzyme linked immunosorbent assay (ELISA) using the most abundant and immunodominant protein for the detection of Orientia specific antibodies in serum has been developed. The performance of the assay was evaluated using prospectively collected acute sera from 248 randomly selected patients in Thailand. The ELISA assay was evaluated using two different cutoff values.

Results

The receiver operating characteristic (ROC) curve generated cutoff values gave slightly better consistency with diagnosis of ST than those cutoff values established by averaging ELISA optical density of known negatives at 99% confidence interval. Both cutoff values provided similar statistical parameters when compared with the diagnosis of ST, indicating the validity of both calculations to derive cutoff values. These results suggest that both IgG and IgM ELISA performed well to accurately diagnose scrub typhus cases in endemic areas using only acute serum samples.

Conclusions

We have successfully developed an ELISA assay for the detection of Orientia-specific antibodies in serum that could provide effective screening of acute sera under clinical setup and it is also a useful assay to estimate seroprevalence in various endemic areas.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2512-8) contains supplementary material, which is available to authorized users.

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

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

Use of Multiplex Real-Time PCR To Diagnose Scrub Typhus

Scrub typhus, caused by Orientia tsutsugamushi, is a common cause of acute undifferentiated febrile illness in the Asia-Pacific region. However, its nonspecific clinical manifestation often prevents early diagnosis. We propose the use of PCR and serologic tests as diagnostic tools. Here, we developed a multiplex real-time PCR assay using hydrolysis (TaqMan) probes targeting O. tsutsugamushi 47-kDa, groEL, and human interferon beta (IFN-β gene) genes to improve early diagnosis of scrub typhus. The amplification efficiency was higher than 94%, and the lower detection limit was 10 copies per reaction. We used a human gene as an internal DNA quality and quantity control. To determine the sensitivity of this PCR assay, we selected patients with confirmed scrub typhus who exhibited a clear 4-fold increase in the level of IgG and/or IgM. The PCR assay result was positive in 45 of 52 patients, indicating a sensitivity of 86.5% (95% confidence interval [CI]: 74.2 to 94.4). The PCR assessment was negative for all 136 non-scrub typhus patients, indicating a specificity of 100% (95% CI: 97.3 to 100). In addition, this test helped diagnose patients with inconclusive immunofluorescence assay (IFA) results and using single blood samples. In conclusion, the real-time PCR assay proposed here is sensitive and specific in diagnosing scrub typhus. Combining PCR and serologic tests will improve the diagnosis of scrub typhus among patients presenting with acute febrile illness.

CD4+ T Cells Are as Protective as CD8+ T Cells against Rickettsia typhi Infection by Activating Macrophage Bactericidal Activity

Rickettsia typhi is an intracellular bacterium that causes endemic typhus, a febrile disease that can be fatal due to complications including pneumonia, hepatitis and meningoencephalitis, the latter being a regular outcome in T and B cell-deficient C57BL/6 RAG1^-/- mice upon Rickettsia typhi infection. Here, we show that CD4⁺ T_H1 cells that are generated in C57BL/6 mice upon R. typhi infection are as protective as cytotoxic CD8⁺ T cells. CD4⁺- as well as CD8⁺-deficient C57BL/6 survived the infection without showing symptoms of disease at any point in time. Moreover, adoptively transferred CD8⁺ and CD4⁺ immune T cells entered the CNS of C57BL/6 RAG1^-/- mice with advanced infection and both eradicated the bacteria. However, immune CD4⁺ T cells protected only approximately 60% of the animals from death. They induced the expression of iNOS in infiltrating macrophages as well as in resident microglia in the CNS which can contribute to bacterial killing but also accelerate pathology. In vitro immune CD4⁺ T cells inhibited bacterial growth in infected macrophages which was in part mediated by the release of IFNγ. Collectively, our data demonstrate that CD4⁺ T cells are as protective as CD8⁺ T cells against R. typhi, provided that CD4⁺ T_H1 effector cells are present in time to support bactericidal activity of phagocytes via the release of IFNγ and other factors. With regard to vaccination against TG Rickettsiae, our findings suggest that the induction of CD4⁺ T_H1 effector cells is sufficient for protection.

Endemic typhus caused by Rickettsia typhi usually is a relatively mild disease. However, CNS inflammation and neurological symptoms are complications that can occur in severe cases. This outcome of disease is regularly observed in T and B cell-deficient C57BL/6 RAG1^-/- mice upon infection with R. typhi. We show here that CD4⁺ T cells are as protective as cytotoxic CD8⁺ T cells against R. typhi as long as they are present in time. This is evidenced by the fact that neither CD8⁺ nor CD4⁺ T cell-deficient C57BL/6 mice develop disease which is also true for R. typhi-infected C57BL/6 RAG1^-/- mice that receive immune CD8⁺ or CD4⁺ at an early point in time. Moreover, adoptive transfer of immune CD4⁺ T cells still protects approximately 60% of C57BL/6 RAG1^-/- mice when applied later in advanced infection when the bacteria start to rise. Although CD8⁺ T cells are faster and more efficient in bacterial elimination, R. typhi is not detectable in CD4⁺ T cell recipients anymore. We further show that immune CD4⁺ T cells activate bactericidal functions of microglia and macrophages in the CNS in vivo and inhibit bacterial growth in infected macrophages in vitro which is in part mediated by the release of IFNγ. Collectively, we demonstrate for the first time that CD4⁺ T cells alone are sufficient to protect against R. typhi infection. With regard to vaccination our findings suggest that the induction of R. typhi-specific CD4⁺ T_H1 effector T cells may be as effective as the much more difficult targeting of cytotoxic CD8⁺ T cells.

Spontaneous Splenic Rupture Caused by Scrub Typhus

Spontaneous rupture of the spleen is rarely described as a complication of scrub typhus infection. We report a previously healthy 74-year-old Thai female farmer who presented in Nakhon Ratchasima, Thailand, with a history of fever and malaise for 5 days, followed by abdominal pain for 1 day. An exploratory laparotomy was performed due to peritonitis. Operative findings revealed a ruptured spleen and hemoperitoneum. A splenectomy was performed afterward. Scrub typhus was confirmed by a 4-fold increase of IgM titer using an indirect immunofluorescence antibody assay and a positive result from the polymerase chain reaction targeting the 47- and 56-kDa genes in Orientia tsutsugamushi She responded well to intravenous chloramphenicol and defervesced within 24 hours without any complication.

Rickettsial Disease in the Peruvian Amazon Basin

Using a large, passive, clinic-based surveillance program in Iquitos, Peru, we characterized the prevalence of rickettsial infections among undifferentiated febrile cases and obtained evidence of pathogen transmission in potential domestic reservoir contacts and their ectoparasites. Blood specimens from humans and animals were assayed for spotted fever group rickettsiae (SFGR) and typhus group rickettsiae (TGR) by ELISA and/or PCR; ectoparasites were screened by PCR. Logistic regression was used to determine associations between patient history, demographic characteristics of participants and symptoms, clinical findings and outcome of rickettsial infection. Of the 2,054 enrolled participants, almost 2% showed evidence of seroconversion or a 4-fold rise in antibody titers specific for rickettsiae between acute and convalescent blood samples. Of 190 fleas (Ctenocephalides felis) and 60 ticks (Rhipicephalus sanguineus) tested, 185 (97.4%) and 3 (5%), respectively, were positive for Rickettsia spp. Candidatus Rickettsia asemboensis was identified in 100% and 33% of the fleas and ticks tested, respectively. Collectively, our serologic data indicates that human pathogenic SFGR are present in the Peruvian Amazon and pose a significant risk of infection to individuals exposed to wild, domestic and peri-domestic animals and their ectoparasites.

Rickettsial infection remains relatively unexplored in South America compared to other regions of the world. For most regions of Peru (including the Amazon Basin), nothing more than broad serological characterization is available about circulating rickettsiae. Even less is known about the animal reservoirs and insect vectors involved in disease transmission. With this study we aimed to better characterize the circulating species of Rickettsia in humans in the Amazon Basin, as well as investigate their domestic animal reservoir and arthropod vectors. Out of 2054 fever patients enrolled we identified 38 individuals with serologic evidence for acute rickettsial infection. Their homes were visited in order to draw blood samples and collect ectoparasites from their domestic animals. Serology and molecular methods were used to test the animal blood samples as well as the ectoparasites. The information collected contributes to the understanding of the transmission dynamics of rickettsial diseases in Iquitos and leads to a better understanding of the exposure risk to rickettsial infection and it will guide approaches for prevention.

Persisting Rickettsia typhi Causes Fatal Central Nervous System Inflammation

Rickettsioses are emerging febrile diseases caused by obligate intracellular bacteria belonging to the family Rickettsiaceae. Rickettsia typhi belongs to the typhus group (TG) of this family and is the causative agent of endemic typhus, a disease that can be fatal. In the present study, we analyzed the course of R. typhi infection in C57BL/6 RAG1(-/-) mice. Although these mice lack adaptive immunity, they developed only mild and temporary symptoms of disease and survived R. typhi infection for a long period of time. To our surprise, 3 to 4 months after infection, C57BL/6 RAG1(-/-) mice suddenly developed lethal neurological disorders. Analysis of these mice at the time of death revealed high bacterial loads, predominantly in the brain. This was accompanied by a massive expansion of microglia and by neuronal cell death. Furthermore, high numbers of infiltrating CD11b(+) macrophages were detectable in the brain. In contrast to the microglia, these cells harbored R. typhi and showed an inflammatory phenotype, as indicated by inducible nitric oxide synthase (iNOS) expression, which was not observed in the periphery. Having shown that R. typhi persists in immunocompromised mice, we finally asked whether the bacteria are also able to persist in resistant C57BL/6 and BALB/c wild-type mice. Indeed, R. typhi could be recultivated from lung, spleen, and brain tissues from both strains even up to 1 year after infection. This is the first report demonstrating persistence and reappearance of R. typhi, mainly restricted to the central nervous system in immunocompromised mice.

Severe murine typhus with pulmonary system involvement

We encountered a case of severe murine typhus complicated by acute respiratory distress syndrome. To determine worldwide prevalence of such cases, we reviewed the literature and found that respiratory symptoms occur in ≈30% of murine typhus patients. In disease-endemic areas, murine typhus should be considered for patients with respiratory symptoms and fever.

Improved Quantification, Propagation, Purification and Storage of the Obligate Intracellular Human Pathogen Orientia tsutsugamushi

Background

Scrub typhus is a leading cause of serious febrile illness in rural Southeast Asia. The causative agent, Orientia tsutsugamushi, is an obligate intracellular bacterium that is transmitted to humans by the bite of a Leptotrombidium mite. Research into the basic mechanisms of cell biology and pathogenicity of O. tsutsugamushi has lagged behind that of other important human pathogens. One reason for this is that O. tsutsugamushi is an obligate intracellular bacterium that can only be cultured in mammalian cells and that requires specific methodologies for propagation and analysis. Here, we have performed a body of work designed to improve methods for quantification, propagation, purification and long-term storage of this important but neglected human pathogen. These results will be useful to other researchers working on O. tsutsugamushi and also other obligate intracellular pathogens such as those in the Rickettsiales and Chlamydiales families.

Methodology

A clinical isolate of O. tsutsugamushi was grown in cultured mouse embryonic fibroblast (L929) cells. Bacterial growth was measured using an O. tsutsugamushi-specific qPCR assay. Conditions leading to improvements in viability and growth were monitored in terms of the effect on bacterial cell number after growth in cultured mammalian cells.

Key results

Conclusions

Here we present a standardised method for comparing the viability of O. tsutsugamushi after purification, treatment and propagation under various conditions. Taken together, we present a body of data to support improved techniques for propagation, purification and storage of this organism. This data will be useful both for improving clinical isolation rates as well as performing in vitro cell biology experiments.

Scrub typhus is a serious, neglected tropical disease that is endemic in large parts of Asia and northern Australia. It is caused by the bacterium O. tsutsugamushi, which is maintained in Leptotrombiculid mites, small arthropods that occasionally bite humans and transmit the disease. O. tsutsugamushi is an obligate intracellular bacterium, which means that it can only survive and grow when it is physically enclosed within a cell, both when it is living in its vector mite, and when it is living in the human or other mammalian host. This makes it difficult to work with in the laboratory, as it needs to be cultured together with host cells. This technical difficulty is one reason why our understanding of this human pathogen is less well-developed than for many other pathogens of equivalent incidence and severity. Here, we have performed a body of work that was designed to measure and improve methods for growing these bacteria in the laboratory, purifying the bacteria from their host cells without damaging them, and preserving bacteria for long periods of time by cryopreservation. This work will support future efforts to understand the basic science behind this and similar intracellular human pathogens.

Epidemiology of scrub typhus and the eschars patterns in South Korea from 2008 to 2012

In South Korea, scrub typhus is the most common acute febrile illness in autumn. We analyzed scrub typhus cases reported from 2008 to 2012 to describe the epidemiology of scrub typhus as well as eschar patterns. A total of 30,478 cases were reported from 2008 to 2012; the incidence rates were higher in the southern and western regions of South Korea. The common clinical symptoms of confirmed scrub typhus cases from 2010 to 2012 were fever/chills (95.2%), eschars (78.9%), and myalgia (61.7%). The primary sites of eschars were the lower extremities (19.0%), abdomen/waist (13.4%), and axilla (11.5%) in men and the shoulder/frontal chest (15.1%), lower extremities (14.5%), and abdomen/waist (13.6%) in women. Regardless of gender, eschars tended to be more on the lower extremities among the leisure activities group. Among the occupational farm work group, who usually lived in rural areas, eschars appeared most frequently on the abdomen/waist in men and on the shoulder/frontal chest in women. Eschar patterns were influenced by gender and activities. These results could facilitate the prevention of scrub typhus and clarify the current status of scrub typhus in South Korea.

Murine typhus in a liver transplant recipient: report of a first case

Zoonoses, especially rickettsial diseases, are rarely reported in solid organ transplant recipients. We report here a case of murine typhus in a 69-year-old liver transplant recipient, who presented with acute febrile illness 5 years post transplantation. Although receiving treatment with broad-spectrum antibiotics, he was still febrile and developed progressive dyspnea. Laboratory results showed elevated transaminases and his chest radiograph revealed bilateral interstitial infiltration. The diagnosis of murine typhus was made by a 4-fold rise in specific Rickettsia typhi antibody, using indirect immunofluorescent assay. He dramatically improved after treatment with doxycycline for 7 days. To our knowledge, this is the first case report of murine typhus in a liver transplant recipient.

Multiple Orientia tsutsugamushi ankyrin repeat proteins interact with SCF1 ubiquitin ligase complex and eukaryotic elongation factor 1 α

Background

Orientia tsutsugamushi, the causative agent of scrub typhus, is an obligate intracellular bacterium. Previously, a large number of genes that encode proteins containing eukaryotic protein-protein interaction motifs such as ankyrin-repeat (Ank) domains were identified in the O. tsutsugamushi genome. However, little is known about the Ank protein function in O. tsutsugamushi.

Methodology/Principal Findings

To characterize the function of Ank proteins, we investigated a group of Ank proteins containing an F-box–like domain in the C-terminus in addition to the Ank domains. All nine selected ank genes were expressed at the transcriptional level in host cells infected with O. tsutsugamushi, and specific antibody responses against three Ank proteins were detected in the serum from human patients, indicating an active expression of the bacterial Ank proteins post infection. When ectopically expressed in HeLa cells, the Ank proteins of O. tsutsugamushi were consistently found in the nucleus and/or cytoplasm. In GST pull-down assays, multiple Ank proteins specifically interacted with Cullin1 and Skp1, core components of the SCF1 ubiquitin ligase complex, as well as the eukaryotic elongation factor 1 α (EF1α). Moreover, one Ank protein co-localized with the identified host targets and induced downregulation of EF1α potentially via enhanced ubiquitination. The downregulation of EF1α was observed consistently in diverse host cell types infected with O. tsutsugamushi.

Conclusion/Significance

These results suggest that conserved targeting and subsequent degradation of EF1α by multiple O. tsutsugamushi Ank proteins could be a novel bacterial strategy for replication and/or pathogenesis during mammalian host infection.

Rapid increase of scrub typhus: an epidemiology and spatial-temporal cluster analysis in Guangzhou City, Southern China, 2006-2012

BACKGROUND

Scrub typhus has been increasingly reported in Southern China, and public health authorities are concerned about its increased incidence. Additionally, little evidence is available on the epidemiology of scrub typhus in Southern China. This study aims to analyze the epidemiological and geographic features of ST in Guangzhou City, Southern China, to guide the future prevention efforts.

METHODS

Scrub typhus surveillance data in Guangzhou City during 2006-2012 were obtained from the Chinese National Communicable Disease Surveillance Network. We first conducted a descriptive analysis to analyze the epidemiological features of scrub typhus. Then we used space-time scan statistic based on a discrete Poisson model to detect and evaluate high-risk spatial-temporal clusters of scrub typhus.

RESULTS

There were 4,001 cases of scrub typhus in Guangzhou City during the study period. The incidence of scrub typhus increased from 3.29 per 100,000 in 2006 to 9.85 per 100,000 in 2012. A summer peak was observed in June and July with a second peak in September and October except year 2009 and 2011. The majority of the cases (71.4%) were among persons aged ≥40 years, and female incidence was higher than male incidence in persons ≥50 years. In the space-time analysis, high-risk clusters were concentrated in rural areas in Guangzhou City. Over the past 7 years, Haizhu District, an urban area, was found to be a high-risk cluster for the first time in 2012.

CONCLUSION

The resurgence of scrub typhus epidemics in Guangzhou population in 2012 necessitates more effective measures for minimizing future epidemics. Consideration of high-risk population and historical spatial-temporal clusters may help prevent scrub typhus. The risk of scrub typhus in urban areas should not be neglected and needs more attention from public health authorities.

Rickettsial infections in Southeast Asia: implications for local populace and febrile returned travelers

Rickettsial infections represent a major cause of non-malarial febrile illnesses among the residents of Southeast Asia and returned travelers from that region. There are several challenges in recognition, diagnosis, and management of rickettsioses endemic to Southeast Asia. This review focuses on the prevalent rickettsial infections, namely, murine typhus (Rickettsia typhi), scrub typhus (Orientia tsutsugamushi), and members of spotted fever group rickettsiae. Information on epidemiology and regional variance in the prevalence of rickettsial infections is analyzed. Clinical characteristics of main groups of rickettsioses, unusual presentations, and common pitfalls in diagnosis are further discussed. In particular, relevant epidemiologic and clinical aspects on emerging spotted fever group rickettsiae in the region, such as Rickettsia honei, R. felis, R. japonica, and R. helvetica, are presented. Furthermore, challenges in laboratory diagnosis and management aspects of rickettsial infections unique to Southeast Asia are discussed, and data on emerging resistance to antimicrobial drugs and treatment/prevention options are also reviewed.

Rickettsiae, protozoa, and opisthokonta/metazoa

Rhizobiales (formerly named Rickettsiales) cause in rare instances meningitis and meningovasculitis, respectively. In case of history of exposure, infection by Rhizobiales needs to be considered since both diagnosis and therapy may be extremely difficult and pathogen-specific. The same applies to protozoa; in this chapter, Babesia species, free-living amoebae and Entamoeba histolytica infection, including severe meningitis and brain abscess, infection by Trypanosoma species (South American and African trypanosomiasis) are discussed with respect to history, epidemiology, clinical signs, and symptoms as well as differential diagnosis and therapy. Parasitic flatworms and roundworms, potentially able to invade the central nervous system, trematodes (flukes), cestodes (in particular, Cysticercus cellulosae), but also nematodes (in particular, Strongyloides spp. in the immunocompromised) are of worldwide importance. In contrast, filarial worms, Toxocara spp., Trichinella spp., Gnathostoma and Angiostrongylus spp. are seen only in certain geographically confined areas. Even more regionally confined are infestations of the central nervous system by metazoa, in particular, tongue worms (=arthropods) or larvae of flies (=maggots). The aim of this chapter is (1) to alert the neurologist to these infections, and (2) to enable the attending emergency neurologist to take a knowledgeable history, with an emphasis on epidemiology, clinical signs, and symptoms as well as therapeutic management possibilities.

Clinical risk-scoring algorithm to forecast scrub typhus severity

Background

The study explored clinical risk characteristics that may be used to forecast scrub typhus severity under routine clinical practices.

Methods

Retrospective data were collected from patients registered at two university-affiliated tertiary care hospitals in the north of Thailand, from 2004 to 2010. Key information was retrieved from in-patient records, out patient cards, laboratory reports and registers. Patients were classified into three severity groups: nonsevere, severe (those with at least one organ involvement), and deceased. Prognostic characteristics for scrub typhus severity were analyzed by a multivariable ordinal continuation ratio regression.

Results

A total of 526 patients were classified into nonsevere (n = 357), severe (n = 100), and deceased (n = 69). The significant multivariable prognostic characteristics for scrub typhus severity were increased body temperature (odds ratio [OR] = 0.58, 95% confidence interval [CI] = 0.45–0.74, P < 0.001), increased pulse rate (OR = 1.03, 95% CI = 1.01–1.05, P < 0.001), presence of crepitation (OR = 3.25, 95% CI = 1.52–6.96, P = 0.001), increased percentage of lymphocytes (OR = 0.97, 95% CI = 0.95–0.98, P = 0.001), increased aspartate aminotransferase (every 10 IU/L) (OR = 1.04, 95% CI = 1.02–1.06, P < 0.001), increased serum albumin (OR = 0.47, 95% CI = 0.27–0.80, P = 0.001), increased serum creatinine (OR = 1.83, 95% CI = 1.50–2.24, P < 0.001), and increased levels of positive urine albumin (OR = 1.43, 95% CI = 1.17–1.75, P < 0.001).

Conclusion

Patients suspicious of scrub typhus with low body temperature, rapid pulse rate, presence of crepitation, low percentage of lymphocyte, low serum albumin, elevated aspartate aminotransferase, elevated serum creatinine, and positive urine albumin should be monitored closely for severity progression.

Clinical risk-scoring algorithm to forecast scrub typhus severity

Purpose

To develop a simple risk-scoring system to forecast scrub typhus severity.

Patients and methods

Seven years’ retrospective data of patients diagnosed with scrub typhus from two university-affiliated hospitals in the north of Thailand were analyzed. Patients were categorized into three severity groups: nonsevere, severe, and dead. Predictors for severity were analyzed under multivariable ordinal continuation ratio logistic regression. Significant coefficients were transformed into item score and summed to total scores.

Results

Predictors of scrub typhus severity were age >15 years, (odds ratio [OR] =4.09), pulse rate >100/minute (OR 3.19), crepitation (OR 2.97), serum aspartate aminotransferase >160 IU/L (OR 2.89), serum albumin ≤3.0 g/dL (OR 4.69), and serum creatinine >1.4 mg/dL (OR 8.19). The scores which ranged from 0 to 16, classified patients into three risk levels: non-severe (score ≤5, n=278, 52.8%), severe (score 6–9, n=143, 27.2%), and fatal (score ≥10, n=105, 20.0%). Exact severity classification was obtained in 68.3% of cases. Underestimations of 5.9% and overestimations of 25.8% were clinically acceptable.

Conclusion

The derived scrub typhus severity score classified patients into their severity levels with high levels of prediction, with clinically acceptable under- and overestimations. This classification may assist clinicians in patient prognostication, investigation, and management. The scoring algorithm should be validated by independent data before adoption into routine clinical practice.

Antibody prevalence and factors associated with exposure to Orientia tsutsugamushi in different aboriginal subgroups in West Malaysia

BACKGROUND

Limited data is available on the current status of scrub typhus infection in the aboriginal population in Malaysia. This study was aimed to provide recent data on the degree of exposure of 280 individuals from seven aboriginal subgroups to Orientia tsutsugamushi (causative agent of scrub typhus) in West Malaysia. The environment, socioeconomic and behavioural risk factors associated with the disease were also investigated.

METHODS/FINDINGS

The antibody prevalence to O. tsutsugamushi ranged from 0 to 36.4% in seven subgroups, with high prevalence rates noted in subgroups involved in agricultural activity and the lowest prevalence rates noted in subgroups whose main occupations were associated to fishing. Univariate analysis indicated populations with age above 18 years (OR = 1.15, 95% CI = 1.02-1.30, P = 0.015), working (OR = 1.99, 95% CI = 1.01-3.92, P = 0.044), working at agriculture area (OR = 1.18, 95% CI = 0.98-1.42, P = 0.031), receiving household income less than US$ 166.7 (RM500) per month (OR = 2.43, 95% CI = 1.16-5.11, P = 0.016) and having close contact with animal pets (OR = 4.06, 95% CI = 1.20-13.76, P = 0.016) are significantly associated with exposure to O. tsutsugamushi. Multivariate analysis confirms that participants who are above 18 years old, receiving household income less than US$ 166.7 (RM500) per month and having close contact with animal pets are 3.6 times (95% CI = 1.81-7.03, P<0.001), 1.3 times (95% CI = 1.14-1.64, P = 0.002) and 1.2 times (95% CI = 1.05-1.06, P = 0.006) more likely to have exposure to O. tsutsugamushi, respectively.

CONCLUSION

The present study indicates that scrub typhus is still an important disease in the aboriginal population in Malaysia. Awareness about the disease and education on the preventive measures are important in reducing the risk of acquiring scrub typhus in the population studied.

Zoonoses in South-East Asia: a regional burden, a global threat

Zoonoses are an issue of growing interest in South-East Asia, where environmental factors and socio-economic context favor the endemization of well-known diseases and the emergence of new pathogens at the human-wildlife interface. However, the health status of the region with respect to many zoonotic diseases remains poorly defined, despite the high overall burden of zoonoses on the countries of the area, and the global risk of new biological threats in the region. The first objective of this paper was to provide an update of data on the zoonoses commonly described by the scientific community and reported by governmental institutions and international organizations in continental South-East Asia. The analysis of the available data led to the identification of some trends in the evolution of the diseases, as well as some gaps in knowledge and in the current surveillance and control networks. In light of these findings, we discuss measures for effectively addressing zoonotic disease issues in South-East Asia, such as the allocation of funds for research and for surveillance and control programs, and a multi-sectoral and multi-disciplinary approach at various levels.

Scrub typhus and comparisons of four main ethnic communities in taiwan in 2004 versus 2008 using geographically weighted regression

Purpose:

On the main island of Taiwan, a higher risk of scrub typhus infection has been reported in endemic clusters in Southeastern Taiwan and in mountainous township areas. However, research on health care problems associated with scrub typhus in Taiwanese ethnic peoples is limited. This study employs spatial analysis of areal data to determine spatial features related to scrub typhus and the four main Taiwanese ethnicities: Hoklo, Hakka, Mainlander, and aboriginal communities, respectively.

Methods:

We used a GWR spatial method to analyze the local regressed relationships between scrub typhus incidence and ethnic community percentage in 349 townships in Taiwan, and the subsequent spatial regressed resultants and local parameter estimates were compared between two periods of 2004 and 2008 by kappa statistics.

Results:

In the GWR models, the spatial regressed relationships of scrub typhus incidences and the Hoklo communities showed significant and negative parameter estimates in numerous locations, showing clusters in Southeastern and Southwestern Taiwan, and areas of the central and southern mountainous townships. Both Hakka and Mainlander communities in the mountainous townships showed less-regressed clusters with scrub typhus prevalence. However, clusters of Aboriginal populations were positively correlated with scrub typhus in highly infected mountainous areas and in Southeastern Taiwan. The kappa value results and the comparisons of local parameter estimates in the 349 townships in Taiwan between 2004 and 2008 indicated that the incidence of scrub typhus in the Hoklo communities was substantial, in the Hakka communities was fair, in the Mainlander communities was slight, and in the aboriginal communities was moderate, respectively.

Conclusion:

The aboriginal communities have been closely associated with higher risks of scrub typhus in the mountainous townships and in the southeastern portion of Taiwan.

Severe murine typhus with shock and acute respiratory failure in a Japanese traveler after returning from Thailand

We treated a case of severe murine typhus in a Japanese traveler after returning from Thailand. Although the disease is typically self-limited or mild, the patient showed shock and multiple organ failure including acute respiratory distress syndrome. Then the patient fully recovered following intensive care and administration of antirickettsial medicines.

Seroepidemiology of rickettsioses in Sri Lanka: a patient based study

Background

Rickettsioses are emerging infections in Sri Lanka as shown by the increase in the number of clinically diagnosed rickettsial patients being reported to the Epidemiology Unit, Sri Lanka. However, mapping the disease for the whole island with laboratory confirmed cases has not been previously carried out.

Methods

615 samples received from 23 hospital representing 8 provinces were tested using ELISA or IFA methods and clinical data was collected using a validated questionnaire.

Results

Rash was found among more spotted fever seropositive patients than scrub typhus seropositive patients while the opposite was true for the presence of eschar. Spotted fever and scrub typhus was found in a geographically restricted manner. Consistent temporal patterns were seen for the presentation of patients with rickettsioses in Kandy and Kurunegala districts for 2009 and 2010.

Conclusions

This study expanded knowledge on the distribution of rickettsioses in Sri Lanka and their clinical profiles which in turn helps in the clinical diagnosis of these infections.

Murine typhus in a pregnant woman

BACKGROUND

Murine typhus is a flea-borne disease caused by Rickettsia typhi. Although uncommon in most of the United States, it is endemic in Southern California. Most cases are unrecognized given its nonspecific viral symptoms and rare complications.

CASE

A pregnant patient presented with complaints of fever and chills. Physical examination was benign. Laboratory abnormalities included elevated transaminases, proteinuria, and thrombocytopenia. The patient gave a history of exposure to cats and opossums in an area endemic for murine typhus. After empiric treatment with azithromycin, her clinical symptoms and laboratory abnormalities promptly improved. Serologies confirmed acute infection with R. typhi.

CONCLUSION

Although the signs and symptoms of murine typhus can mimic other pregnancy-related complications, a high index of suspicion in endemic areas can lead to the correct diagnosis and prompt treatment.

Acute scrub typhus in Northern Thailand: EKG changes

The electrocardiographic (EKG) manifestations of scrub typhus were prospectively evaluated in 29 adult patients who acquired Orientia tsutsugamushi infection in Chiang Rai, Northern Thailand. EKGs were normal in 22 of the 29 patients (76%); minor non-specific changes were found in the other 7 patients; ie ST segment/T wave changes (10%), U waves (7%), and premature ventricular contractions (4%). These results suggest that EKG changes in scrub typhus acquired in areas of diminished antibiotic susceptibility are similar to those observed in O. tsutsugamushi infection acquired elsewhere.