Scrub Typhus In Korea Research Articles

Coinfection With Severe Fever With Thrombocytopenia Syndrome and Scrub Typhus in Korea.

Scrub typhus and severe fever with thrombocytopenia syndrome (SFTS) are the 2 most common tick-borne infectious diseases in Korea. Every year, an increasing number of cases are reported, which is a public health concern. Therefore, we aimed to investigate the prevalence of SFTS-scrub typhus coinfection in patients with SFTS. Clinical samples were collected from 129 patients with SFTS. One-step reverse-transcription polymerase chain reaction (PCR) was performed to identify the SFTS virus (SFTSV), and real-time PCR followed by nested PCR was performed to detect the Orientia tsutsugamushi gene for scrub typhus. Phylogenetic analysis was conducted to confirm the evolutionary relationships among different species. Among 129 SFTS cases, 2 patients with SFTSV were positive for O. tsutsugamushi with a prevalence of coinfection of 1.6% (95% confidence interval, .001-.06). Phylogenetic analysis confirmed these as O. tsutsugamushi strain Boryong. Our study found that 1.6% of patients were coinfected with SFTS and scrub typhus infection. We believe that this information will add a new dimension to clinical diagnosis, which should be considered for better public health management. Further research is needed to better understand the ecological transmission dynamics and geographical distribution of SFTSV and O. tsutsugamushi in endemic countries.

Prevalence of chigger mites and Orientia tsutsugamushi strains in northern regions of Gangwon-do, Korea.

The present study aimed to survey the prevalence of chigger mites and Orientia tsutsugamushi (O. tsutsugamushi) infection in the northern regions of Gangwon-do, Korea. From early February to early June 2015, a total of 17,050 chiggers were collected from striped field mice, Apodemus agrarius, in Cheorwon-gun, Hwacheon-gun, Yanggu-gun, and Goseong-gun, which are well-known endemic areas of scrub typhus in Korea. The chiggers were analyzed using molecular genomic methods, as previously described. Among the 7,964 identified chiggers, the predominant species was Leptotrombidium pallidum (76.9%), followed by L. zetum (16.4%), L. orientale (4.3%), L. palpale (0.3%), L. tectum (0.2%), and Neotrombicula tamiyai (1.8%). The chigger index (CI) was highest in Hwacheon (115.58), followed by Cheorwon (97.02), Yanggu (76.88), and Goseong (54.68). Out of the 79 O. tsutsugamushi-positive chigger pools, 67 (84.8%) were identified as the Boryong strain, 10 (12.7%) as the Youngworl strain, and only 2 were the Jecheon strain. Based on the high infestation of chiggers in striped field rodents and the high rate of O. tsutsugamushi infection in chigger mites, Hwacheon-gun and Cheorwon-gun are presumed to be high-risk areas for scrub typhus. Furthermore, L. pallidum, a major vector of scrub typhus, and the dominant O. tsutsugamushi serotype, the Boryong strain, were found in the northern regions of Gangwon-do, Korea.

The Scrub Typhus Incidence Rate of Agricultural Workers in South Korea: Using Farmers’ Safety Insurance Data

Objectives: We investigated the incidence rate of Scrub typhus in farmers. Methods: Data were obtained from 2016 to 2021 in the farmers’ safety insurance from NongHyup Life Insurance. The incidence was defined as a newly diagnosed patients with Scrub typhus in 2016-2020. The incidence rate was confirmed by sex, age and administrative districts. Results: The age-standardized incidence rate of Scrub typhus was 115 per 100,000 people from 2016 to 2020. The crude rate was presented to be 8.9, 43.8, 79.9, 127.2, 156.3, and 174.3 per 100,000 people, respectively, in the 40s to 80s or over. According to administrative districts, the highest crude rate was 201.6 and 193.0 per 100,000 people in Jeonnam and Gyeongnam, respectively, and the lowest crude rate was 6.0 per 100,000 people in Gangwon. And the monthly incidence was 54.3% in November and 32.0% in October, concentrated in autumn. Conclusions: The age-standardized incidence rate of Scrub typhus in Korea was 115.1 per 100,000 people, and it occurred more frequently in the southern regions in terms of administrative districts and increased with age. Based on this, it is thought that it will be helpful in establishing a management plan to prevent Scrub typhus.

Geographical Distribution and Epidemiologic Factors of Chigger Mites on Apodemus agrarius during Autumn in Korea.

A nationwide survey of chigger mites causing scrub typhus and an investigation of epidemiologic factors for chigger mites was conducted at 16 localities in 8 provinces in Korea during autumn 2009, 2012, and 2013. A total of 233 Apodemus agrarius were captured, and all were infested with chigger mites. The chigger index was highest in Chungcheongbuk-do in 2009 (358.3) and 2012 (290.1) and Chungcheongnam-do in 2013 (294.4). The predominant chigger mite species was Leptotrombidium pallidum in the northern and central parts and L. scutellare in the southern and western parts, Korea. L. pallidum was not found in Jellanam-do and Gyeongsangnam-do and the distribution of L. scutellare had been expanded in the northern parts of Korea. The chigger index of L. pallidum was positively correlated with temperature and negatively correlated with humidity. The incidence of scrub typhus is dependent on L. scutellare index. These findings could be helpful to monitor the distribution of chigger mites and to develop a preventive measures for scrub typhus in Korea.

Deforestation Increases the Risk of Scrub Typhus in Korea.

Background: Scrub typhus is an important public health issue in Korea. Risk factors for scrub typhus include both individual-level factors and environmental drivers, and some are related to the increased density of vector mites and rodents, the natural hosts of the mites. In this regard, deforestation is a potential risk factor, because the deforestation-induced secondary growth of scrub vegetation may increase the densities of mites and rodents. To examine this hypothesis, this study investigated the association between scrub typhus and deforestation. Methods: We acquired district-level data for 2006–2017, including the number of cases of scrub typhus reported annually, deforestation level, and other covariates. Deforestation was assessed using preprocessed remote-sensing satellite data. Bayesian regression models, including Poisson, negative binomial, zero-inflated Poisson, and zero-inflated negative binomial models, were examined, and spatial autocorrelation was considered in hierarchical models. A sensitivity analysis was conducted using different accumulation periods for the deforestation level to examine the robustness of the association. Results: The final models showed a significant association between deforestation and the incidence of scrub typhus (relative risk = 1.20, 95% credible interval = 1.15–1.24). The sensitivity analysis gave consistent results, and a potential long-term effect of deforestation for up to 5 years was shown. Conclusion: The results support the potential public health benefits of forest conservation by suppressing the risk of scrub typhus, implying the need for strong engagement of public health sectors in conservation issues from a One Health perspective.

History of Tsutsugamushi Disease in Korea.

Tsutsugamushi disease or scrub typhus in Korea was first officially reported in foreign soldiers in 1951 and in indigenous persons in 1986. However, the history is further prolonged. The book Dong Ui Bo Gam, published in 1613, described “Soo Dok” (water poisoning), which is similar to tsutsugamushi disease. Further, the term was mentioned in the book Hyang Yak Gu Geup Bang, first published in 1232–1251. During the Japanese colonial rule (1910-1945), Trombicula akamushi was identified in Suwon, Korea, in 1917. Although cases of tsutsugamushi disease in Korea with a murine typhus-like illness and OXK-positivity were reported in 1935, such atypical presentation was not recognized as tsutsugamushi disease. During the Korean War, in 1951, tsutsugamushi disease developed in two British soldiers stationed in the Imjin River, who presented typical features and positive OXK reactions. Indigenous cases have re-emerged since 1986. Thereafter, there were many studies on various aspects of tsutsugamushi disease: epidemiology, vector, small mammals, clinical features and complications, diagnosis, and treatment. Persistence of Orientia tsutsugamushi and its possible recrudescence with pneumonia were reported in 2012 and 2014, respectively.

Differences in agricultural activities related to incidence of scrub typhus between Korea and Japan.

OBJECTIVESThe purpose of this study was to establish a basis for improving or strengthening the preventive strategy against scrub typhus in Korea by comparing and analyzing the difference of prevention behaviors contributing to the occurrence of scrub typhus in Japan and Korea.METHODSThe survey was carried out in Jeollabuk-do, which is a high risk and high incidence area, and Fukuoka Prefecture, which is a high risk and low incidence area. The study included 406 Korean farmers and 216 Japanese farmers. Data were collected through face-to-face surveys by interviewers who had completed standardized education.RESULTSKorean farmers have a higher percentage of agricultural working posture that involved contact with weeds than Japanese farmers (p<0.05). The frequency and proportion of weeding were lower in Korean farmers than in Japanese farmers (p<0.05). The level of knowledge about scrub typhus was significantly higher among Korean farmers than among Japanese farmers (p<0.05). Mostly, the behavior of agriculture work was more appropriate for Japanese farmers than for Korean farmers (p<0.05). The total average level of agricultural work was lower in Korea than in Japan, lower in men than women, and lower in part-time farmers than full-time farmers (p<0.05).CONCLUSIONSThis study suggests that it is reasonable to develop and provide a program that can improve the level of preventive behavior taking into consideration the characteristics of the subject in order to reduce the incidence of diseases in high-risk areas for scrub typhus.

Isolation and Genetic Characterization ofOrientia tsutsugamushifrom Scrub Typhus Patients in Gyeongsangnam-do, Korea

Orientia tsutsugamushi (O. tsutsugamushi), which is endemic to an Asia-Pacific region, has increased its incidence and caused annually around 10 thousand patients infected with scrub typhus in Korea in the past several years. In the present study, we isolated 44 O. tsutsugamushi from the patients with febrile illness accompanied with or without an eschar in Gyeongsangnam-do, Korea. These isolates were characterized by genetic analysis of the major outer membrane protein, the 56-kDa type-specific antigen (tsa56), which is unique to O. tsutsugamushi. Two types of sequences of tsa56, designated by JJ1 and JJ2, were determined from 37 and 7 isolates of the 44 isolates, respectively. JJ1 and JJ2 showed 74.7~90.8% identity in nucleotide sequence and 66.1~90.5% identity in amino acid sequence with 33 reference strains except for Boryong and Kuroki. JJ1 and JJ2 had 100 and 99.9% nucleotide identity to Boryong strain, and 99.9 and 99.8 % to Kuroki, which has been known to be similar to Boryong, respectively. In addition, they showed 77.9~ 81.4% nucleotide identity with the cluster of Gilliam-related genotypes, whereas they showed higher nucleotide identity (89.6~90.8%) with the cluster of Karp-related genotypes. To our knowledge, this is the first report to isolate O. tsutsugamushi and characterize their genotype as the Boryong in Jinju and West Gyeongsangnam-do, Korea, even though it has been reported that the Boryong was the predominant genotype in isolates from chiggers, domestic rodents, and patients in the southern part of Korea. Furthermore, our isolates could be useful source to study on the pathophysiology and epidemiology of scrub typhus in Korea.

Extracorporeal Membrane Oxygenation for Complicated Scrub Typhus

Scrub typhus is a mite-borne infectious disease caused by Orientia tsutsugamushi . Although early diagnosis and appropriate antibiotic therapy improve the prognosis for the majority of patients, life-threatening complications are not uncommon. Here, we present a case of successful veno-veno-type extracorporeal membrane oxygenation for scrub typhus-induced complications, including acute respiratory distress syndrome, myocarditis and multi-organ dysfunction. To our knowledge, this is the first case report of successful extracorporeal membrane oxygenation in complicated scrub typhus in Korea.

Impact of Daily Average Temperature on Annual Incidence of Scrub Typhus for Predicting

Background: Scrub typhus is an acute febrile infectious disease. It is one of the most prevalent vector borne disease and occurs most frequently from October to December in Korea. The incidence of scrub typhus in Korea has shown rapidly increasing trend last decades and over 10,000 cases were reported in 2013. Weather variables are potential predictors of scrub typhus incidence. Predicting annual incidence of scrub typhus before autumn facilitates early public health responses to minimize morbidity. This study explored the impact of daily average temperature on the outbreak of scrub typhus in Korea. Methods: Analysis was performed using data on monthly weather variables and notified annual cases of scrub typhus in 68 cities, Korea from 2001 to 2008. Cities are categorized according to average annual incidence from 2001 to 2008 (High incidence area: average annual incidence &gt;30 cases/100,000 persons, medium incidence area: 10-30 cases/100,000 persons, low incidence area: 0-10 cases/100,000 persons). A Poisson generalized estimating equations (GEE) model was used to estimate the impact of daily average temperature in the summer season on annual incidence of scrub typhus. Results: For high incidence area, medium incidence area and low incidence area, the average incidence per year was increased by 31% [95% confidence interval (CI): 15, 49%], 37% [95% CI: 22, 54%] and 28% [95% CI: 11, 48%] for a 1 degrees C increase in daily average temperature in August after controlling for potential confounding effects of precipitation and humidity. Daily average temperature, precipitation and humidity of other months like June, July in summer season did not impact on annual incidence for predicting. Conclusions: These findings suggest that daily average temperature in August have a considerable impact on annual incidence of scrub typhus in Korea for predicting before coming of autumn as outbreak season.

A Case of Immune Thrombocytopenic Purpura Associated with Scrub Typhus

Thrombocytopenia is a common manifestation of rickettsial disease. However, the pathogenesis of thrombocytopenia in many rickettsial diseases is poorly understood. Thrombocytopenia may be associated with consumption due to widespread endothelial damage or disseminated intravascular coagulation, hypersplenism, decreased marrow production, and immune-mediated platelet destruction. Some reports have found anti-platelet antibodies detected in thrombocytopenic patients with rickettsial disease. In addition to thrombocytopenia, facial palsy and Guillain-Barre syndrome were also reported as immune-mediated phenomena in scrub typhus. Here we report a case diagnosed as immune-mediated thrombocytopenia associated with scrub typhus. This is the first report of immune thrombocytopenic purpura (ITP) associated with scrub typhus in Korea. The patient exhibited eschar with a high titer of anti-tsutsugamushi antibody, thrombocytopenia, severe gastrointestinal hemorrhage, and purpura on the lower region of both legs. After steroid treatment, the sustained thrombocytopenia recovered. (Korean J Med 2014;86:362-366)

Are There Spatial and Temporal Correlations in the Incidence Distribution of Scrub Typhus in Korea?

ObjectivesA hierarchical generalized linear model (HGLM) was applied to estimate the transmission pattern of scrub typhus from 2001 to 2011 in the Republic of Korea, based on spatial and temporal correlation. MethodsBased on the descriptive statistics of scrub typhus incidence from 2001 to 2011 reported to the Korean Centers for Disease Control and Prevention, the spatial and temporal correlations were estimated by HGLM. Incidences according to age, sex, and year were also estimated by the best-fit model out of nine HGLMs. A disease map was drawn to view the annual regional spread of the disease. ResultsThe total number of scrub typhus cases reported from 2001 to 2011 was 51,136: male, 18,628 (36.4%); female, 32,508 (63.6%). The best-fi;t model selected was a combination of the spatial model (Markov random-field model) and temporal model (first order autoregressive model) of scrub typhus transmission. The peak incidence was 28.80 per 100,000 persons in early October and the peak incidence was 40.17 per 100,000 persons in those aged 63.3 years old by the best-fit HGLM. The disease map showed the spread of disease from the southern central area to a nationwide area, excepting Gangwon-do (province), Gyeongsangbuk-do (province), and Seoul. ConclusionIn the transmission of scrub typhus in Korea, there was a correlation to the incidence of adjacent areas, as well as that of the previous year. According to the disease map, we are unlikely to see any decrease in the incidence in the near future, unless ongoing aggressive measures to prevent the exposure to the vector, chigger mites, in rural areas, are put into place.

Spatial Distribution Analysis of Scrub Typhus in Korea

ObjectiveThis study analyzes the spatial distribution of scrub typhus in Korea. MethodsA spatial distribution of Orientia tsutsugamushi occurrence using a geographic information system (GIS) is presented, and analyzed by means of spatial clustering and correlations. ResultsThe provinces of Gangwon-do and Gyeongsangbuk-do show a low incidence throughout the year. Some districts have almost identical environmental conditions of scrub typhus incidence. The land use change of districts does not directly affect the incidence rate. ConclusionGIS analysis shows the spatial characteristics of scrub typhus. This research can be used to construct a spatial-temporal model to understand the epidemic tsutsugamushi.

Massive small bowel bleeding caused by scrub typhus in Korea

A 79-year-old man was diagnosed with scrub typhus based on fever, eschar, skin rash and a markedly elevated serum tsutsugamushi antibody and doxycycline was started. Five days later, hematochezia developed and multiple small bowel ulcerations with hemorrhage were seen on colonoscopy. Despite intensive therapy, the massive hematochezia worsened and the distal small bowel was resected. Multiple ulcerated lesions were identified pathologically as vasculitis caused by scrub typhus. This is the first reported case of pathologically proven small bowel involvement in scrub typhus infection.

Geographical Distribution and Relative Abundance of Vectors of Scrub Typhus in the Republic of Korea

A survey to determine the geographical distribution and relative abundance of potential vectors of scrub typhus was conducted from October to November 2006 at 13 localities throughout the Republic of Korea. Apodemus agrarius accounted for 97.6% (80/82) of all rodents, while only 2 Myodes regulus (2/82) were collected. A total of 10,860 chiggers were collected from A. agrarius belonging to 4 genera and 8 species, while only Walchia fragilis (40) was collected from Myodes regulus. Leptotrombidium pallidum (8,137; 74.9%), a vector of scrub typhus, was the predominant species collected from A. agrarius followed by Leptotrombidium scutellare (2,057, 18.9%), Leptotrombidium palpale (279; 2.7%), Leptotrombidium orientale (232; 2.1%), and Leptotrombidium zetum (79; 0.7%), Neotrombicula tamiyai (58; 0.5%), Euschoengastica koreaensis (16; 0.1%), and Cheladonta ikaoensis (2; < 0.1%). L. pallidum was the predominant chigger collected at collection sites in Gangwon (100%), Gyeonggi (87.2%), Chungnam (100%), Chungbuk (100%), Jeonbuk (73.9%), Jeonnam (77.0%), and Gyeongbuk (66.1%) provinces, whereas L. scutellare was the predominant chigger collected in Gyeongnam province (77.9%) and Jeju Island (62.3%). Data suggest a correlation between chigger population abundance and human cases of scrub typhus in Korea.

Doxycycline Resistance in Orientia tsutsugamushi Isolated from Korean Patients

Background :Doxycycline has been the drug of choice for the treatment of scrub typhus. However, scrub typhus with poor response to doxycycline was first reported in Thailand in 1996. To date, it is not known whether doxycycline resistant scrub typhus is present in Korea. To investigate the doxycycline resistance of scrub typhus in Korea, we performed an experiment to evaluate the degree of growth inhibition of Orientia tsutsugamushi at the minimal inhibitory concentration (MIC) of doxycycline. Materials and Methods : 37 isolates of Orientia tsutsugamushi were collected from Korean patients with scrub typhus during 10 year period (from 1997 to 2007). 34 isolates consisted of Boryong serotype or related serotypes. These strains were stained with FS15, a monoclonal antibody against the linear epitope on the protein located at the outer membrane of O. tsutsugamushi. Three isolates were confirmed as serotype Gilliam, which was stained by anti-Gilliam antibody. The antibodystainable 35 isolates were incubated in media containing 0.1 and 0.2 μg/mL of doxycycline for 3 days. Then the growth indices of Orientia were measured by flow cytometry. If the growth index was greater than 10%, the isolate was tentatively classified as an isolate resistant to doxycycline and its MIC was measured. Results :Demographic and treatment data were similar to the results of previous reports. Infection was mainly observed in Inchon and the Chungcheongnam province. No patient showed delayed response to antibiotics. Of 35 hospitalized patients, 4 (11.4%) were managed at the intensive care unit, and 1 (2.9%) died of nosocomial pneumonia. All the 2 patients whose isolates were serotype Gilliam Yonchon/Ikeda-like strain were managed at the intensive care unit. Six of the 34 isolates from Korean patients exhibited growth indices greater than 10% at the MIC of doxycycline; however, the MICs of these isolates did not exceed 0.2 μg/mL. One isolate of serotype Gilliam showed an MIC of 0.0125 ug/mL, which seemed to be underestimated due to weak fluorescence of the anti-Gilliam antibody. Conclusions :Although the number of tested isolates is small, insensitivity of scrub typhus to doxycycline is not a major reason for treatment failure in Korea. Serotype Gilliam, especially Yochon/ Ikeda-like strain, may be associated with severe form of scrub typhus. More studies concerning the antibiotic susceptibility for serotype Gilliam are warranted.

A Case of Concomitant Scrub Typhus and Leptospirosis

Tsutsugamushi disease (Scrub typhus) is an acute, febrile illness caused by Orientia tsutsugamushi, which is transmitted to humans through chigger bites. Leptospirosis, a febrile disea se caused by various pathogenic Leptospira, and is acquired by exposure to contaminated water and soil. Both diseases have been the most common acute febrile diseases in the autumn in Korea for many years. Concomitant leptospirosis and scrub typhus is quite rare. We report a case of a coinfection with leptospirosis and scrub typhus in a 51-year-old male who presented with fever, abdominal pain and acute dyspnea. The patient was diagnosed with as acalculous cholecystitis, acute respiratory distress syndrome, and septic shock caused by the infection. This is the first case report of a coinfection with leptospirosis and scrub typhus in Korea. (Tuberc Respir Dis 2007; 63: 378-381)

Scrub Typhus in Korea: Importance of Early Clinical Diagnosis in This Newly Recognized Endemic Area

Scrub typhus became a well recognized infectious disease threat to military operations in the Pacific Theater during World War II. Early diagnosis and treatment with tetracycline or chloramphenicol dramatically reduces the mortality and morbidity of this disease. Korea is a newly recognized scrub typhus endemic country. We report our experience with 189 scrub typhus patients seen at a civilian outpatient clinic in Chinhae, Republic of Korea, from 1985 through 1990, and verify the accuracy of clinical diagnosis by serologic tests.