• Parasites, Hosts and Diseases
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• v.59 no.3
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• pp.319-324
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• 2021

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.

• Parasites, Hosts and Diseases
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• v.52 no.2
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• pp.225-229
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• 2014

A total of 9,281 larval chigger mites were collected from small mammals captured at Hwaseong-gun, Gyeonggi-do (Province) (2,754 mites from 30 small mammals), Asan city, Chungcheongnam-do (3,358 mites from 48 mammals), and Jangseong-gun, Jeollanam-do (3,169 for 62 mammals) from April-November 2009 in the Republic of Korea (= Korea) and were identified to species. Leptotrombidium pallidum was the predominant species in Hwaseong (95.8%) and Asan (61.2%), while Leptotrombidium scutellare was the predominant species collected from Jangseong (80.1%). Overall, larval chigger mite indices decreased from April (27.3) to June (4.9), then increased in September (95.2) and to a high level in November (169.3). These data suggest that L. pallidum and L. scutellare are the primary vectors of scrub typhus throughout their range in Korea. While other species of larval chigger mites were also collected with some implications in the transmission of Orientia tsutsugamushi, they only accounted for 11.2% of all larval chigger mites collected from small mammals.

• Tuberculosis and Respiratory Diseases
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• v.61 no.4
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• pp.389-393
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• 2006

Tsutstugamushi disease is a major febrile disease that generally occurs in the fall in Korea with hemorrhagic fever with renal syndrome and leptospirosis. This disease is often accompanied by interstitial pneumonia, acute renal failure and liver failure. The causative agent, namely Orientia tsutsugamushi, is transmitted to humans through the bite of a laval trombiculid mite, which is commonly known as a chigger. A 78 year old man was admitted in October 2004 with intractable fever and a drowsy mentality. Two weeks earlier, he visited a private clinic complaining of a simple skin rash. He was treated with antihistamine and steroid, but his symptoms were aggravated and he was referred to our hospital. His physical examination and laboratory findings showed a septic shock status. The maculopapular rash had spread over his face, chest, abdomen and extremities. Eschar was observed in lower back area but it was too difficult to distinguish it from other skin rashes. His chest X-ray appeared as diffuse nodular patchy consolidations in the bilateral lung parenchyme. He was treated with a mechanical ventilator and doxycycline under th suspicion of Tsutstugamushi disease. However, he suffered multiorgan failure accompanied by acute respiratory distress syndrome, acute renal failure and acute hepatitis. He was treated in the intensive care unit for approximately 12 weeks and his general condition was recovered.

• Parasites, Hosts and Diseases
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• v.56 no.5
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• pp.521-525
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• 2018

Rodents are well-known reservoirs and vectors of many emerging and re-emerging infectious diseases, but little is known about their role in zoonotic disease transmission in Bhutan. In this study, a cross-sectional investigation of zoonotic disease pathogens in rodents was performed in Chukha district, Bhutan, where a high incidence of scrub typhus and cases of acute undifferentiated febrile illness had been reported in people during the preceding 4-6 months. Twelve rodents were trapped alive using wire-mesh traps. Following euthanasia, liver and kidney tissues were removed and tested using PCR for Orientia tsutsugamushi and other bacterial and rickettsial pathogens causing bartonellosis, borreliosis, human monocytic ehrlichiosis, human granulocytic anaplasmosis, leptospirosis, and rickettsiosis. A phylogenetic analysis was performed on all rodent species captured and pathogens detected. Four out of the 12 rodents (33.3%) tested positive by PCR for zoonotic pathogens. Anaplasma phagocytophilum, Bartonella grahamii, and B. queenslandensis were identified for the first time in Bhutan. Leptospira interrogans was also detected for the first time from rodents in Bhutan. The findings demonstrate the presence of these zoonotic pathogens in rodents in Bhutan, which may pose a risk of disease transmission to humans.

• Journal of agricultural medicine and community health
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• v.29 no.1
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• pp.177-184
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• 2004

Objectives: Tsutsugamushi disease is one of the most significant acute febrile illnesses, increasing in frequency of occurrence during the late autumn in rural areas of Korea. Methods: I have conducted a case-control study on 30 cases who had the fever as a chief complaint, then had been ruled out as having the Tsutsugamushi disease. Data was collected retrospectively by review of chart regarding their general characteristics, clinical and laboratory findings, then was analysed by chi-test. Results: Of 30 cases, 16 cases were seropositive and 14 cases were seronegative against O. tsutsugamushi. Of seropositive for tsutsugamushi disease, 56.3% were female; 37.5% were in their seventies; 50.0% were farmers; 62,6% had chances of exposure to fields or mountains. And 75.0% occurred in November. The main symptoms and signs were fever and chill(100.0%), headache(75.0%). weakness and fatigue(93.8%), and eschar(68.8%). The characteristic laboratory findings were elevated AST(50.0%), ALT(62.5%), and abnormal urinalysis(56.3%). On the other hand, of seronegative cases, 57.1% were male; 50.0% were in their fifties; 42.9% were farmers; 57.2% had chances of exposure to fields or mountains. And 71.4% occurred in November. The symptoms and signs were fever and chill(100.0%), headache(85.7%), eschar(64.3%). weakness, fatigue and skin(57.1%). The laboratory findings were elevated AST(71.4%) and ALT(64.3%), and abnormal urinalysis(42.9%). However, there were no significant differences between the seropositive and seronegative cases(P>.05). Conclusions: Acute febrile community inhabitants who have the epidemiological, clinical as well as laboratory features should be focused upon for the early diagnosis and treatment for tsutsugamushi disease whether or not possessing the serological antibody against O. tsutsugamushi.

• Parasites, Hosts and Diseases
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• v.55 no.5
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• pp.555-559
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• 2017

Chigger mites are parasites of rodents and other vertebrates, invertebrates, and other arthropods, and are the only vectors of scrub typhus, in addition to other zoonoses. Therefore, investigating their distribution, diversity, and seasonal abundance is important for public health. Rodent surveillance was conducted at 6 districts in Shandong Province, northern China ($114-112^{\circ}E$, $34-38^{\circ}N$), from January to December 2011. Overall, 225/286 (78.7%) rodents captured were infested with chigger mites. A total of 451 chigger mites were identified as belonging to 5 most commonly collected species and 3 genera in 1 family. Leptotrombidium scutellare and Leptotrombidium intermedia were the most commonly collected chigger mites. L. scutellare (66.2%, 36.7%, and 49.0%) was the most frequently collected chigger mite from Apodemus agrarius, Rattus norvegicus, and Microtus fortis, respectively, whereas L. intermedia (61.5% and 63.2%) was the most frequently collected chigger mite from Cricetulus triton and Mus musculus, respectively. This study demonstrated a relatively high prevalence of chigger mites that varied seasonally in Shandong Province, China.

• Korean Journal of Veterinary Service
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• v.35 no.3
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• pp.183-189
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• 2012

Tsutsugamushi disease or scrub typhus cause by Orientia tsutsugamushi is an endemic disease in Korea. Chigger mites and field rodents play roles in transmission of the disease by the vector and host of the agent. The purpose of this study is to investigate the density of the chigger mites and field rodents due to environmental factors such as temperature, relative humidity, soil thickness and the various vegetations to the 9 field rodent collection sites. The total 62 field rodents was captured by the Sherman collapsible traps from April to October 2009 at the Jangseong of Jeonnam Province, Korea. The trapping rate of the field rodents by the different collecting sites was dominant at subside storage water (24%), bush near by dam (22%), bank around field (20%), followed by 18% of grassy field and surround cattle shed. The distribution of chigger mites by the different collecting sites was the highest at Bush near by dam (28.7%). And the sites of subside storage water, bank around field and surround cattle shed were 20.4%, 18.8%, 16.4%, respectively. On the other hand the collecting sites of stream bank and ridges between rice paddies were not collected. The temperature to the collecting sites was showed $24.1^{\circ}C$ in June and $24.2^{\circ}C$ in October which was higher than April ($10.6^{\circ}C$), whereas lower than May ($25.3^{\circ}C$) and September ($26.8^{\circ}C$). The highest number of mites was collected at $24.2^{\circ}C$ and 46.6% relative humidity in October. The chigger mites and field rodents were highly collected between 18 and 24% at the sites where are loosely in the superficial layers of the soil from 8.0 cm to 10.2 cm. Total 25 species of vegetation were distributed at the collecting sites. In the present study, strong evidence was found that bank around field and grassy field were provided for the prevalence sites of tsutsugamushi disease.

• Parasites, Hosts and Diseases
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• v.59 no.4
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• pp.377-392
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• 2021

This paper is to illustrate the infestation and related ecological characteristics of chigger mites on the Asian house rat (Rattus tanezumi). A total of 17,221 chigger mites were collected from 2,761 R. tanezumi rats, and then identified as 131 species and 19 genera in 2 families. Leptotrombidium deliense, the most powerful vector of scrub typhus in China, was the first major dominant species on R. tanezumi. All the dominant mite species were of an aggregated distribution among different individuals of R. tanezumi. The species composition and infestations of chiggers on R. tanezumi varied along different geographical regions, habitats and altitudes. The species-abundance distribution of the chigger mite community was successfully fitted and the theoretical curve equation was ${\hat{S}}(R)={37e^{-(0.28R)}}^2$. The total chigger species on R. tanezumi were estimated to be 199 species or 234 species, and this further suggested that R. tanezumi has a great potential to harbor abundant species of chigger mites. The results of the species-plot relationship indicated that the chig-ger mite community on R. tanezumi in Yunnan was an uneven community with very high heterogeneity. Wide geographi-cal regions with large host samples are recommended in the investigations of chigger mites.

• Parasites, Hosts and Diseases
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• v.58 no.3
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• pp.301-308
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• 2020

Owing to global climate change, the global resurgence of vector-borne infectious diseases and their potential to inflict widespread casualties among human populations has emerged as a pivotal burden on public health systems. Tsutsugamushi disease (scrub typhus) in the Republic of Korea is steadily increasing and was designated as a legal communicable disease in 1994. The disease is a mite-borne acute febrile disease most commonly contracted from October to December. In this study, we tried to determine the prevalence of tsutsugamushi disease transmitted by chigger mites living on rodents and investigated their target vector diversity, abundance, and distribution to enable the mapping of hotspots for this disease in 2015. A total of 5 species belonging to 4 genera (109 mites): Leptotrombidium scutellare 60.6%, L. pallidum 28.4% Neotrombicula tamiyai 9.2%, Euschoengastia koreaensis/0.9%), and Neoschoengastia asakawa 0.9% were collected using chigger mite collecting traps mimicking human skin odor and sticky chigger traps from April to November 2015. Chigger mites causing tsutsugamushi disease in wild rodents were also collected in Hwaseong for the zoonotic surveillance of the vector. A total of 77 rodents belonging to 3 genera: Apodemus agrarius (93.5%), Crocidura lasiura (5.2%), and Micromys minutus (1.3%) were collected in April, October, and November 2015. The most common mite was L. pallidum (46.9%), followed by L. scutellare (18.6%), and L. orientale (18.0%). However, any of the chigger mite pools collected from rodent hosts was tested positive for Orientia tsutsugamushi, the pathogen of tsutsugamushi disease, in this survey.

• Parasites, Hosts and Diseases
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• v.59 no.6
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• pp.625-634
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• 2021

Based on the field investigations in 91 investigation sites (counties) in southwest China between 2001 and 2019, the present paper reported the chigger mites on A. agrarius mice in southwest China for the first time by using a series of statistical methods. From 715 striped field mice captured in 28 of 91 investigated sites, only 255 chiggers were collected, and they were identified as 14 species, 6 genera in 3 subfamilies under 2 families. Of 715 A. agrarius mice, only 24 of them were infested with chigger mites with low overall prevalence (P_M=3.4%), overall mean abundance (M_A=0.36 mites/host) and overall mean intensity (M_I=10.63 mites/host). The species diversity and infestation of chiggers on A. agrarius were much lower than those previously reported on some other rodents in southwest China. On a certain species of rodent, A. agrarius mouse in southwest China seems to have a very low susceptibility to chigger infestations than in other geographical regions. Of 14 chigger species, there were 3 dominant species, Leptotrombidium sialkotense, L. rupestre and Schoengastiella novoconfuciana, which were of aggregated distribution among different individuals of A. agrarius hosts. L. sialkotense, one of 6 main vectors of scrub typhus in China, was the first dominant on A. agrarius. The species similarity of chigger mites on male and female hosts was low with C_SS=0.25, and this reflects the sex-bias of different genders of A. agrarius mice in harboring different chigger species.