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Orientia tsutsugamushi is the etiological agent of scrub typhus, an acute, mite-borne, febrile illness that occurs in the Asia-Pacific region. Historically, strain characterization used serological analysis and revealed dramatic antigenic diversity. Eyeing a recommendation of potential vaccine candidates for broad protection, we review geographic diversity and serological and DNA prevalences. DNA analysis together with immunological analysis suggest that the prototype Karp strain and closely related strains are the most common throughout the region of endemicity. According to serological analysis, ∼50% of isolates are seroreactive to Karp antisera, and approximately one-quarter of isolates are seroreactive to antisera against the prototype Gilliam strain. Molecular methods reveal greater diversity. By molecular methods, strains phylogenetically similar to Karp make up ∼40% of all genotyped isolates, followed by the JG genotype group (Japan strains serotypically similar to the Gilliam strain but genetically non-Gilliam; 18% of all genotyped isolates). Three other genotype groups (Kato-related, Kawasaki-like, and TA763-like) each represent ∼10% of genotyped isolates. Strains genetically similar to the Gilliam strain make up only 5% of isolates. Strains from these groups should be included in any potential vaccine.

Scrub typhus, caused by Orientia tsutsugamushi, has been thought to be geographically restricted to the “tsutsugamushi triangle” in the Asia–Pacific region. In this report, a potential focus in southern Chile is identified. Scrub typhus is a vector-borne zoonosis caused by Orientia tsutsugamushi . The infection is transmitted by “chiggers” (i.e., the larvae of trombiculid mites of the genus leptotrombidium). Although chiggers feed on various vertebrates, the main reservoir is the vector itself, which maintains orientia organisms through transstadial and transovarial transmission. 1 After the bite of an infective chigger, a characteristic necrotic inoculation lesion, termed eschar, can develop, which typically contains high bacterial loads. The microorganism then spreads through the lymphatic fluid and blood, causing systemic manifestations that include fever, rash, and laboratory abnormalities such as elevated levels of C-reactive protein and liver . . .

Scrub typhus is a potentially fatal rickettsiosis caused by Orientia species intracellular bacteria of the genus Orientia. Although considered to be restricted to the Asia Pacific region, scrub typhus has recently been discovered in southern Chile. We analyzed Orientia gene sequences of 16S rRNA (rrs) and 47-kDa (htrA) from 18 scrub typhus patients from Chile. Sequences were ≥99.7% identical among the samples for both amplified genes. Their diversity was 3.1%-3.5% for rrs and 11.2%-11.8% for htrA compared with O. tsusugamushi and 3.0% for rrs and 14.8% for htrA compared with Candidatus Orientia chuto. Phylogenetic analyses of both genes grouped the specimens from Chile in a different clade from other Orientia species. Our results indicate that Orientia isolates from Chile constitute a novel species, which, until they are cultivated and fully characterized, we propose to designate as Candidatus Orientia chiloensis, after the Chiloé Archipelago where the pathogen was identified.

Orientia tsutsugamushi , the causative agent of scrub typhus, is endemic to the Asia–Pacific region. In South Korea, the Boryong strain is considered dominant; however, nationwide phylogeographic distribution and genetic diversity based on clinical isolates remain incompletely characterized. In this study, 121 O. tsutsugamushi clinical isolates were collected from scrub typhus patients at 11 hospitals across South Korea between 2015 and 2024. Isolates were genotyped using 56-kDa gene sequencing and multilocus sequence typing (MLST) of seven housekeeping genes. Sequence analysis and phylogenetic reconstruction were performed using BLAST, PubMLST, BURST, MEGA11, DnaSP6, and R-based tools. Five 56-kDa genotypes were identified: Boryong (93.4%), Ikeda, Je-cheon, Young-worl, and Yeo-joo. MLST revealed 11 sequence types (STs), including five novel STs. While the Boryong strain and related STs were distributed nationwide, minor strains showed restricted distribution in northern regions. Several isolates sharing the same 56-kDa genotype exhibited different MLST STs, indicating possible recombination or local microevolution. This study provides the first nationwide MLST-based characterization of O. tsutsugamushi in South Korea and demonstrates the dominance of the Boryong strain alongside localized diversity. Our findings underscore the utility of MLST for higher-resolution typing and support the need for continued molecular surveillance to inform regional epidemiology and disease management.

Scrub typhus, caused by Orientia tsutsugamushi , is an important and neglected vector-borne zoonotic disease with an expanding known distribution. The ecology of the disease is complex and poorly understood, impairing discussion of public health interventions. To highlight what we know and the themes of our ignorance, we conducted a systematic review of all studies investigating the pathogen in vectors and non-human hosts. A total of 276 articles in 7 languages were included, with 793 study sites across 30 countries. There was no time restriction for article inclusion, with the oldest published in 1924. Seventy-six potential vector species and 234 vertebrate host species were tested, accounting for over one million trombiculid mites (‘chiggers’) and 83,000 vertebrates. The proportion of O. tsutsugamushi positivity was recorded for different categories of laboratory test and host species. Vector and host collection sites were geocoded and mapped. Ecological data associated with these sites were summarised. A further 145 articles encompassing general themes of scrub typhus ecology were reviewed. These topics range from the life-cycle to transmission, habitats, seasonality and human risks. Important gaps in our understanding are highlighted together with possible tools to begin to unravel these. Many of the data reported are highly variable and inconsistent and minimum data reporting standards are proposed. With more recent reports of human Orientia sp. infection in the Middle East and South America and enormous advances in research technology over recent decades, this comprehensive review provides a detailed summary of work investigating this pathogen in vectors and non-human hosts and updates current understanding of the complex ecology of scrub typhus. A better understanding of scrub typhus ecology has important relevance to ongoing research into improving diagnostics, developing vaccines and identifying useful public health interventions to reduce the burden of the disease.

We performed molecular characterization of Orientia tsutsugamushi on DNA sequences from 5 patients from Bhutan with scrub typhus. In the 56 kDa gene, all isolates aligned with those from other Asia countries, including Nepal, India, Thailand, and Taiwan. High serum IgM titers correlated with PCR positivity in acutely ill patients.

We report 3 cases of dual-genotype Orientia tsutsugamushi infection in Hainan Island, China. Patients exhibited diverse clinical manifestations, including afebrile illness and multiorgan involvement, highlighting the complexity associated with genetic diversity in scrub typhus. Clinicians should maintain heightened suspicion for atypical scrub typhus manifestations in endemic regions.

The intracellular bacterium Orientia tsutsugamushi relies on the microtubule cytoskeleton and the motor protein dynein to traffic to the perinuclear region within infected cells. However, it remains unclear how the bacterium is coupled to the dynein machinery and how transport is regulated. Here, we discover that O. tsutsugamushi uses its autotransporter protein ScaC to recruit the dynein adaptors BICD1 and BICD2 for movement to the perinucleus. We show that ScaC is sufficient to engage dynein-based motility in the absence of other bacterial proteins and that BICD1 and BICD2 are required for efficient movement of O. tsutsugamushi during infection. Using TIRF single-molecule assays, we demonstrate that ScaC induces BICD2 to adopt an open conformation which activates the assembly of dynein-dynactin complexes. Our results reveal a role for BICD adaptors during bacterial infection and provide mechanistic insights into the life cycle of an important human pathogen. The pathogen Orientia tsutsugamushi is an obligate intracellular bacterium that depends on host cell machinery for intracellular movement. Here, Manigrasso et al. provide insights into the molecular mechanisms by which the bacteria hijack the host’s microtubule networks to navigate within cells.

Scrub typhus is a leading cause of severe undifferentiated fever in Asia. This community-based surveillance study assessed the epidemiologic characteristics of scrub typhus in an area of India where the disease is endemic.

Scrub typhus, caused by Orientia spp., is a mite-borne disease historically restricted to the Asia-Pacific region. Autochthonous cases have been confirmed in southern Chile, while serological evidence has been reported in Peru, Honduras and Colombia, suggesting wider distribution in Latin America. Identifying recent exposure among febrile patients is essential to evaluate its role in acute undifferentiated febrile illness (AUFI) etiology. To assess the possible implication of Orientia infection as a cause of AUFI in Villeta, Colombia. Between September and December 2021, patients with AUFI were recruited. Whole-blood samples were tested for Orientia DNA by real-time PCR targeting the 16S rRNA gene. Acute and convalescent serum samples were analyzed for IgG antibodies by IFA and ELISA, with paired samples titration to assess seroconversion. Reactive sera were further confirmed by Western blot. Forty-one acute whole-blood samples were tested by qPCR; no Orientia DNA was detected. Serology identified antibodies in 27 % (11/41) of patients: six positive by ELISA, two by IFA, and three by both methods. Based on paired sera, eight cases (20 %) were classified as recent infections, including cases of seroconversion, and three (7 %) as previous exposures. Western blot confirmed specific reactivity against Orientia antigens in all positive samples. This study provides serological evidence of Orientia circulation among febrile patients in Villeta, Colombia, including clear cases of seroconversion. Western blot validated reactivity against immunodominant proteins. Findings suggest a local scrub typhus–like illness and highlight the need for pathogen isolation and genetic characterization to clarify its contribution to AUFI.