Scrub Typhus and Its Causative Agent, Orientia tsutsugamushi

Vincent, Gemma

doi:10.1007/978-3-319-46859-4_16

Cited by 11 publications

(11 citation statements)

References 256 publications

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“…Scrub typhus usually presents as acute undifferentiated fever and is caused by Orientia tsutsugamushi , a bacterium of the order Rickettsiales . Human transmission of the bacterium is caused by the bite of infected larval stage (called chiggers) of trombiculid mites 1 . The disease spectrum ranges from fever to lethal complications involving various organs.…”

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confidence: 99%

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Scrub typhus in urban areas of Wardha district in central India

Narang

Deshmukh

Jain

et al. 2022

Indian Journal of Medical Research

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Background & objectives: Scrub typhus caused by Orientia tsutsugamushi presents as acute undifferentiated fever and can be confused with other infectious causes of fever. We studied scrub typhus as part of a study on hospital-based surveillance of zoonotic and vector-borne zoonotic diseases at a tertiary care hospital located in the Wardha district, Maharashtra, India. We report here descriptive epidemiology and climatic factors affecting scrub typhus. Methods: Patients of any age and sex with fever of ≥5 days were enrolled for this study. Data on sociodemographic variables were collected by personal interviews. Blood samples were tested by IgM ELISA to diagnose scrub typhus. Confirmation of scrub typhus was done by indirect immunofluorescence assay for IgM (IgM IFA). The climatic determinants were determined using time-series Poisson regression analysis. Results: It was found that 15.9 per cent of the study participants were positive for scrub typhus by IgM ELISA and IgM IFA, both. Positivity was maximum (23.0%) in 41-60 yr of age and more females were affected than males (16.6 vs . 15.5%). Farmworkers were affected more (23.6%) than non-farm workers (12.9%). The disease positivity was found to be high in monsoon and post-monsoon seasons (22.9 and 19.4%) than in summer and winter. Interpretation & conclusions: There were three hot spots of scrub typhus in urban areas of Wardha district. Rainfall and relative humidity in the previous month were the significant determinants of the disease.

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confidence: 99%

“…groin, axilla and waistband. However, the proportion of scrub typhus patients showing eschar ranges from 1-4 to >60 per cent 1 . One new species, Orientia chuto was identified in Dubai in 2010 2 .…”

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Scrub typhus in urban areas of Wardha district in central India

Narang

Deshmukh

Jain

et al. 2022

Indian Journal of Medical Research

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“…Of these, VD I-IV is the most variable and is the most important in determining the genotype (12). Knowledge of the circulating genotypes in a given area requires amplification of the complete gene followed by sequencing and phylogenetic analysis (6, 10, 30, 31). In India, such data is not available, we present the first comprehensive genotyping data based on amplification and sequencing of the four variable domains (VD I-IV) of the immuno dominant type specific 56 kDa gene.…”

Section: Discussionmentioning

confidence: 99%

“…Only one sequence was found to be Karp. Globally, Karp genotype is reported to account for about 39.5% and found throughout the endemic region (31). Our present study provides first report on Orientia tsutsugamushi genotypes using complete 56 kDa gene sequence.…”

Section: Discussionmentioning

confidence: 99%

Genotyping ofOrientia tsutsugamushicirculating in and around Vellore (South India) using TSA 56 gene

Janaki

Govindasamy

Lakshmisurya

et al. 2023

Preprint

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The immunodominant TSA 56 gene of Orientia tsutsugamushi, (scrub typhus agent) has four variable regions (VD-I to VD-IV) making it useful for genotyping. As of date the genotyping data from India is based on partial 56kDa gene sequence analysis. The complete TSA 56 gene sequence is important for knowing the circulating strains and for designing region specific diagnostics and vaccines. This study was undertaken to determine Orientia tsutsugamushi genotypes circulating in and around Vellore using complete and partial TSA 56 gene. Of the 379 whole blood samples from suspected scrub typhus patients, 162 were positive by 47 kDa qPCR. Long protocol to amplify the complete TSA 56 gene (≈1605 bp) was performed on 21 samples. On the same 21 samples the partial gene sequence was also amplified using the Horinouchi (≈650bp) and the Furuya (≈480 bp) protocol. Using a combination of Sanger and Nanopore technology complete sequence was obtained for 9 and near complete (1551 to 1596 bp) for 4 respectively. As Furuya protocol gave multiple bands we obtained 480 bp sequences from the 13 complete gene sequences by in silico analysis. In contrast, 650bp sequences were obtained for 11 samples while for the remaining two we derived the 650 bp sequences from the complete gene sequences (Long protocol). Phylogenetic analysis of the complete gene (Long protocol) which includes VD-I to VD-IV region and partial gene (Horinouchi) which amplifies the VD-I to VD-III regions showed identical genotypes. Twelve belonged to TA763 genotype and one belongs to Karp genotype. The Furuya sequence (in silico) correctly identified the Karp genotype and 10 of the TA763 genotypes. Two TA763 genotypes (identified by complete and 650 bp partial gene analysis) were misidentified by Furuya sequence analysis as Karp genotype. The limited analysis showed the commonest Orientia tsutsugamushi genotypes circulating in and around Vellore is TA763 and that the 650 bp (Sanger) sequencing could be a cost effective method for identifying the scrub typhus genotypes. However, these results need to be validated by larger prospective multi-centric studies.

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“…Once inside the cell, the organism is transported to the perinuclear area by dynein mediated transport on microtubules, and it multiplies there by binary fission. The organism after multiplication is then released out of the host cell by budding and starts infecting the adjacent cells (23,24).…”

Section: Pathogenesis Of Scrub Typhusmentioning

confidence: 99%

Scrub typhus diagnostics: An overview

Bora²,

Perumalla

et al. 2023

Preprint

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Scrub typhus caused by Orientia tsutsugamushi is a vector-borne, zoonotic disease which is common in the tsutsugamushi triangle. Scrub typhus causes AUFI in patients with non-specific clinical features and is difficult to diagnose when the highly characteristic but not pathognomonic eschar is not seen. As the eschar is not always present, laboratory tests are needed for confirmation. Serological assays are the main stay of laboratory diagnosis of scrub typhus thus far. In this review, we present the salient clinical features and clinical algorithms suggestive of this disease that help in better selection of diagnostics. The various scrub typhus assays along with their advantages and disadvantages have also been discussed. Furthermore, we have also discussed the upcoming diagnostics, both serological and molecular assays which can be available in the near future.

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Scrub Typhus and Its Causative Agent, Orientia tsutsugamushi

Cited by 11 publications

References 256 publications

Scrub typhus in urban areas of Wardha district in central India

Scrub typhus in urban areas of Wardha district in central India

Genotyping ofOrientia tsutsugamushicirculating in and around Vellore (South India) using TSA 56 gene

Scrub typhus diagnostics: An overview

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