scholarly journals Orientia tsutsugamushi dynamics in vectors and hosts: ecology and risk factors for foci of scrub typhus transmission in northern Thailand

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Ivo Elliott ◽  
Neeranuch Thangnimitchok ◽  
Kittipong Chaisiri ◽  
Tri Wangrangsimakul ◽  
Piangnet Jaiboon ◽  
...  
Keyword(s):  
High Risk ◽  
Small Mammals ◽  
Disease Ecology ◽  
Scrub Typhus ◽  
Disease Risk ◽  
Diversity Index ◽  
Asia Pacific ◽  
Orientia Tsutsugamushi ◽  
Northern Thailand ◽  
Field Samples

Abstract Background Scrub typhus is an important neglected vector-borne zoonotic disease across the Asia–Pacific region, with an expanding known distribution. The disease ecology is poorly understood, despite the large global burden of disease. The key determinants of high-risk areas of transmission to humans are unknown. Methods Small mammals and chiggers were collected over an 18-month period at three sites of differing ecological profiles with high scrub typhus transmission in Chiang Rai Province, northern Thailand. Field samples were identified and tested for Orientia tsutsugamushi by real-time PCR. The rates and dynamics of infection were recorded, and positive and negative individuals were mapped over time at the scale of single villages. Ecological analyses were performed to describe the species richness, community structure and interactions between infected and uninfected species and habitats. Generalised linear modelling (GLM) was applied to examine these interactions. Results The site with the highest rates of human infection was associated with the highest number of infected chigger pools (41%), individual chiggers (16%), proportion of the known vector species Leptotrombidium deliense (71%) and chigger index (151). Chigger species diversity was lowest (Shannon diversity index H′: 1.77) and rodent density appeared to be high. There were no consistent discrete foci of infection identified at any of the study sites. The small mammals Rattus tanezumi and Bandicota indica and the chiggers L. deliense and Walchia kritochaeta emerged as central nodes in the network analysis. In the GLM, the end of the dry season, and to a lesser extent the end of the wet season, was associated with O. tsutsugamushi-infected small mammals and chiggers. A clear positive association was seen between O. tsutsugamushi-positive chigger pools and the combination of O. tsutsugamushi-positive chigger pools and O. tsutsugamushi-positive small mammals with lowland habitats. Conclusions These findings begin to reveal some of the factors that may determine high-risk foci of scrub typhus at a fine local scale. Understanding these factors may allow practical public health interventions to reduce disease risk. Further studies are needed in areas with diverse ecology. Graphical abstract

scholarly journals Outer Membrane Protein A Conservation among Orientia tsutsugamushi Isolates Suggests Its Potential as a Protective Antigen and Diagnostic Target

2018 ◽  
Author(s):  
Sean M. Evans ◽  
Haley E. Adcox ◽  
Lauren VieBrock ◽  
Ryan S. Green ◽  
Alison Luce-Fedrow ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Outer Membrane ◽  
Outer Membrane Protein ◽  
Tertiary Structure ◽  
Scrub Typhus ◽  
Protein A ◽  
Asia Pacific ◽  
Molecular Diagnostic ◽  
Orientia Tsutsugamushi ◽  
Outer Membrane Protein A

Scrub typhus threatens one billion people in the Asia-Pacific area and cases have emerged outside this region. It is caused by infection with any of the multitude of strains of the bacterium, Orientia tsutsugamushi. A vaccine that affords heterologous protection and a commercially available molecular diagnostic assay are lacking. Herein, we determined that the nucleotide and translated amino acid sequences of outer membrane protein A (OmpA) are highly conserved among 51 O. tsutsugamushi isolates. Molecular modeling revealed the predicted tertiary structure of O. tsutsugamushi OmpA to be very similar to that of the phylogenetically related pathogen, Anaplasma phagocytophilum, including the location of a helix that contains residues functionally essential for A. phagocytophilum infection. PCR primers were developed that amplified ompA DNA from all O. tsutsugamushi strains, but not from negative control bacteria. Using these primers in quantitative real-time PCR enabled sensitive detection and quantitation of O. tsutsugamushi ompA DNA from organs of mice that had been experimentally infected with the Karp or Gilliam strains. The high degree of OmpA conservation among O. tsutsugamushi strains evidences its potential to serve as a molecular diagnostic target and justifies its consideration as a candidate for developing a broadly protective scrub typhus vaccine.

Field assessment of Orientia tsutsugamushi infection in small mammals and its association with the occurrence of human scrub typhus in Taiwan

Acta Tropica ◽  
2014 ◽  
Vol 131 ◽  
pp. 117-123 ◽  
Author(s):  
Pey-Ru Lin ◽  
Hui-Ping Tsai ◽  
Ming-Hui Weng ◽  
Hung-Chi Lin ◽  
Kuo-Ching Chen ◽  
...  
Keyword(s):  
Small Mammals ◽  
Scrub Typhus ◽  
Orientia Tsutsugamushi ◽  
Field Assessment

scholarly journals Genetic Typing, Based on the 56-Kilodalton Type-Specific Antigen Gene, of Orientia tsutsugamushi Strains Isolated from Chiggers Collected from Wild-Caught Rodents in Taiwan

2011 ◽  
Vol 77 (10) ◽  
pp. 3398-3405 ◽  
Author(s):  
Pey-Ru Lin ◽  
Hui-Ping Tsai ◽  
Pei-Yi Tsui ◽  
Ming-Hui Weng ◽  
Ming-Der Kuo ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Scrub Typhus ◽  
Sequence Similarity ◽  
Specific Antigen ◽  
Febrile Illness ◽  
Prototype Strain ◽  
Asia Pacific ◽  
Orientia Tsutsugamushi ◽  
Content Type ◽  
Strain Characterization

ABSTRACTOrientia tsutsugamushiis the etiological agent of scrub typhus, a mite-borne, febrile illness that occurs in the Asia-Pacific region. We conducted strain characterization ofO. tsutsugamushiisolates from chiggers obtained from rodents based the nucleotide sequence of the 56-kDa outer membrane protein gene. With the use of PCR, a total of 68 DNA sequences of 56-kDa antigen genes were amplified. Phylogenetic analysis revealed that there were at least six definable clusters among the 68 isolates: 37% Karp-related strains (25/68), 27% TA763 strains (18/68), 12% JG-related strains (8/68), 19% Kato-related strains (13/68), 4% divergent strains (3/68), and 1% representing a Gilliam prototype strain (1/68). Overall, theO. tsutsugamushigenotypes exhibited a high degree of diversity, similar to that seen in strains from the rest of the areas where scrub typhus is endemic. Moreover, the 56-kDa protein sequence similarity betweenO. tsutsugamushiisolates from mites and those from human patients (H. Y. Lu et al., Am. J. Trop. Med. Hyg. 83:658-663, 2010) were striking, thus highlighting potential risk factors for this emerging zoonotic disease.

scholarly journals Scrub Typhus and the Misconception of Doxycycline Resistance

2019 ◽  
Vol 70 (11) ◽  
pp. 2444-2449 ◽  
Author(s):  
Tri Wangrangsimakul ◽  
Weerawat Phuklia ◽  
Paul N Newton ◽  
Allen L Richards ◽  
Nicholas P J Day
Keyword(s):  
Scrub Typhus ◽  
Asia Pacific ◽  
Orientia Tsutsugamushi ◽  
Asia Pacific Region ◽  
Bacterial Host ◽  
Obligate Intracellular ◽  
Independent Verification ◽  
Risk Treatment ◽  
Controversial Nature

Abstract Scrub typhus, a neglected infectious disease caused by the obligate intracellular bacterium Orientia tsutsugamushi, is a major cause of fever across the Asia Pacific region with more than a billion people at risk. Treatment with antibiotics such as doxycycline or chloramphenicol is effective for the majority of patients. In the 1990s, reports from northern Thailand raised a troubling observation; some scrub typhus patients responded poorly to doxycycline, which investigators attributed to doxycycline resistance. Despite the controversial nature of these reports, independent verification was neglected, with subsequent studies speculating on the role of doxycycline resistance in contributing to failure of treatment or prophylaxis. In this review, we have outlined the evidence for drug-resistant Orientia tsutsugamushi, assessed the evidence for doxycycline resistance, and highlight more recent findings unsupportive of doxycycline resistance. We conclude that doxycycline resistance is a misconception, with treatment outcome likely to be determined by other bacterial, host, and pharmacological factors.

scholarly journals Origins, Importance and Genetic Stability of the Prototype Strains Gilliam, Karp and Kato of Orientia tsutsugamushi

2019 ◽  
Vol 4 (2) ◽  
pp. 75 ◽  
Author(s):  
Kelly ◽  
Fuerst ◽  
Richards
Keyword(s):  
Scrub Typhus ◽  
Febrile Illness ◽  
Diagnostic Procedures ◽  
Research Literature ◽  
Etiologic Agent ◽  
Asia Pacific ◽  
Future Research ◽  
Orientia Tsutsugamushi ◽  
Culture History ◽  
Clinical Tools

Scrub typhus, a chigger-borne febrile illness, occurs primarily in countries of the Asia-Pacific rim and islands of the Western Pacific. The etiologic agent is the obligate intracellular rickettsial bacterium Orientia tsutsugamushi. Research on O. tsutsugamushi has relied on the availability of several prototype strains, which were isolated from human cases of scrub typhus in the 1940s and 1950s. We review the history of the three original, and most important, prototype strains, Gilliam, Karp and Kato, including information on their isolation, their culture history, their clinical characteristics, their importance within the research literature on scrub typhus, and recent advances in elucidating their molecular genomics. The importance of these strains to the research and development of clinical tools related to scrub typhus is also considered. Finally, we examine whether the strains have been genetically stable since their isolation, and whether prototype strains maintained in separate laboratories are identical, based on pairwise comparisons of several sequences from four genes. By using genetic information archived in international DNA databases, we show that the prototype strains used by different laboratories are essentially identical, and that the strains have retained their genetic integrity at least since the 1950s. The three original prototype strains should remain a standard by which new diagnostic procedures are measured. Given their fundamental position in any comparative studies, they are likely to endure as a critical part of present and future research on scrub typhus and Orientia.

scholarly journals Monitoring Chigger Mites for Orientia tsutsugamushi in Field Small Mammals in Hwaseong-si, Gyeonggi-do, Korea, 2019-2020

2021 ◽  
Vol 59 (3) ◽  
pp. 319-324
Author(s):  
Young Yil Bahk ◽  
Seong Kyu Ahn ◽  
Jinyoung Lee ◽  
Hyung Wook Kwon ◽  
Sung Jong Hong ◽  
...  
Keyword(s):  
Small Mammals ◽  
Scrub Typhus ◽  
Rapid Diagnosis ◽  
The Other ◽  
Orientia Tsutsugamushi ◽  
Chigger Mite ◽  
Apodemus Agrarius ◽  
Tsutsugamushi Disease ◽  
Pcr Test

Incidence of tsutsugamushi disease (scrub typhus) caused by Orientia tsutsugamushi, is steadily increasing. It is a mite-borne disease transmitted by chigger mites. In this study, the chigger mites were collected from field small mammals in Hwaseong-si (city), Gyeonggi-do (province), Korea, 2019 and 2020. The field small mammals captured were 56 Apodemus agrarius (94.9%) and 3 Crocidura lasiura (5.1%). A total of 7,531 chigger mites were collected from the captured small mammals. Using PCR test, 153 chigger mite pools were examined and 17 pools were reported positive for O. tsutsugamushi. The O. tsutsugamushi were identified to 5 strains; Jecheon strain was most prevalent, followed by Boryong strain. The other strains were OI011, Taguchi, and Shimokoshi. Collectively, these results provide essential regional information on mite-borne tsutsugamushi disease in the Hwaseong-si, and further contribute to bring awareness and rapid diagnosis for the tsutsugamushi disease.

scholarly journals New Genotypes and Diversity of Orientia tsutsugamushi Isolated from Scrub Typhus Patients in South Korea as Determined by Multilocus Sequence Typing

2020 ◽  
Author(s):  
Joo-Hee Hwang ◽  
Jeongsik Kim ◽  
In O Sun ◽  
Tae Hee Lee ◽  
Kyung Min Chung ◽  
...  
Keyword(s):  
South Korea ◽  
Multilocus Sequence Typing ◽  
Scrub Typhus ◽  
Asia Pacific ◽  
Pacific Region ◽  
Orientia Tsutsugamushi ◽  
Asia Pacific Region ◽  
Typing Method ◽  
Life Threatening ◽  
New Alleles

AbstractOrientia tsutsugamushi, an obligate intracellular organism, is the causative agent of scrub typhus, which is endemic in the Asia-Pacific region. No comparative studies on the genotypic properties of O. tsutsugamushi have been performed using multilocus sequence typing (MLST) in South Korea. Here, we characterized 51 clinical isolates from Jeonju, in southwestern Korea, and we compared them to isolates from Thailand, Laos, and Japan. We also identified 10 new alleles and six novel sequence types. Overall, our results suggest that the relative genetic stability and the clonal populations of O. tsutsugamushi strains in South Korea have remained mostly conserved.Author summaryScrub typhus is a life-threatening disease, caused by infection with O. tsutsugamushi, a Gram-negative intracellular bacterium. Approximately one million people are infected globally every year, especially in the Asia-Pacific region. Strains of O. tsutsugamushi are typically distinguished serologically on the basis of sequences of the highly polymorphic 56-kDa outer membrane protein. Multilocus sequence typing (MLST) is a generic typing method that provides a unified bacterial isolate characterization approach that can be used for evolutionary and population studies of bacteria. In this study, we describe the development and application of a MLST scheme that was applied to 51 O. tsutsugamushi isolates. We found 10 new alleles and six new STs, which yielded a total of seven O. tsutsugamushi STs in South Korea. Among seven different STs (ST 48, 93-98), ST 48 account for the largest proportion (49.0%) of O. tsutsugamushi STs in South Korea. With the exception of the appearance of six novel STs, the clonal populations have remained conserved but further study of population structure and evolutionary trends is warranted.

scholarly journals Azithromycin Activities against Orientia tsutsugamushi Strains Isolated in Cases of Scrub Typhus in Northern Thailand

1999 ◽  
Vol 43 (11) ◽  
pp. 2817-2818 ◽  
Author(s):  
George Watt ◽  
Pacharee Kantipong ◽  
Krisada Jongsakul ◽  
Pochaman Watcharapichat ◽  
Duangporn Phulsuksombati
Keyword(s):  
Pregnant Women ◽  
Scrub Typhus ◽  
Survival Rates ◽  
Drug Resistant ◽  
Orientia Tsutsugamushi ◽  
Northern Thailand ◽  
Human Trials

ABSTRACT Azithromycin was given to mice and humans infected with strains ofOrientia tsutsugamushi from northern Thailand, where drug-resistant scrub typhus occurs. Azithromycin and doxycycline yielded comparable mouse survival rates (73 and 79%, respectively;P > 0.5). Symptoms, signs, and fever in two pregnant women abated rapidly with azithromycin. Prospective human trials are needed.

Scrub typhus (Orientia tsutsugamushi), A rapidly spreading epidemic in Chennai - A standalone lab experience

2016 ◽  
Vol 5 (09) ◽  
pp. 4896
Author(s):  
Sripriya C.S.* ◽  
Shanthi B. ◽  
Arockia Doss S. ◽  
Antonie Raj I. ◽  
Mohana Priya
Keyword(s):  
Scrub Typhus ◽  
Clinical Symptoms ◽  
Clinical Manifestations ◽  
Febrile Illness ◽  
Orientia Tsutsugamushi ◽  
The Past ◽  
Igm Elisa ◽  
The Mean ◽  
Specific Symptoms ◽  
Symptoms And Signs

Scrub typhus (Orientia tsutsugamushi), is a strict intracellular bacterium which is reported to be a recent threat to parts of southern India. There is re-emergence of scrub typhus during the past few years in Chennai. Scrub typhus is an acute febrile illness which generally causes non-specific symptoms and signs. The clinical manifestations of this disease range from sub-clinical disease to organ failure to fatal disease. This study documents our laboratory experience in diagnosis of scrub typhus in patients with fever and suspected clinical symptoms of scrub typhus infection for a period of two years from April 2014 to April 2016 using immunochromatography and IgM ELISA methods. The study was conducted on 648 patients out of whom 188 patients were found to be positive for scrub typhus. Results also showed that pediatric (0 -12 years) and young adults (20 – 39 years) were more exposed to scrub typhus infection and female patients were more infected compared to male. The study also showed that the rate of infection was higher between September to February which also suggested that the infection rate is proportional to the climatic condition. Statistical analysis showed that the mean age of the patients in this study was 37.6, standard deviation was 18.97, CV % was 50.45. 

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