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Chang T, Min KD, Cho SI, Kim Y. Associations of meteorological factors and dynamics of scrub typhus incidence in South Korea: A nationwide time-series study. ENVIRONMENTAL RESEARCH 2024; 245:117994. [PMID: 38151145 DOI: 10.1016/j.envres.2023.117994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Revised: 12/01/2023] [Accepted: 12/18/2023] [Indexed: 12/29/2023]
Abstract
Scrub typhus, also known as Tsutsugamushi disease, is a climate-sensitive vector-borne disease that poses a growing public health threat. However, studies on the association between scrub typhus epidemics and meteorological factors in South Korea need to be complemented. Therefore, we aimed to analyze the association among ambient temperature, precipitation, and the incidence of scrub typhus in South Korea. First, we obtained data on the weekly number of scrub typhus cases and concurrent meteorological variables at the city-county level (Si-Gun) in South Korea between 2001 and 2019. Subsequently, a two-stage meta-regression analysis was conducted. In the first stage, we conducted time-series regression analyses using a distributed lag nonlinear model (DLNM) to investigate the association between temperature, precipitation, and scrub typhus incidence at each location. In the second stage, we employed a multivariate meta-regression model to combine the association estimates from all municipalities, considering regional indicators, such as mite species distribution, Normalized Difference Vegetation Index (NDVI), and urban-rural classification. Weekly mean temperature and weekly total precipitation exhibited a reversed U-shaped nonlinear association with the incidence of scrub typhus. The overall cumulative association with scrub typhus incidence peaked at 18.7 C° (with RRs of 9.73, 95% CI: 5.54-17.10) of ambient temperature (reference 9.7 C°) and 162.0 mm (with RRs of 1.87, 95% CI: 1.02-3.83) of precipitation (reference 2.8 mm), respectively. These findings suggest that meteorological factors contribute to scrub typhus epidemics by interacting with vectors, reservoir hosts, and human behaviors. This information serves as a reference for future public health policies and epidemiological research aimed at controlling scrub typhus infections.
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Affiliation(s)
- Taehee Chang
- Department of Public Health Sciences, Graduate School of Public Health, Seoul National University, Seoul, 08826, Republic of Korea
| | - Kyung-Duk Min
- College of Veterinary Medicine, Chungbuk National University, 28644, Republic of Korea
| | - Sung-Il Cho
- Department of Public Health Sciences, Graduate School of Public Health, Seoul National University, Seoul, 08826, Republic of Korea; Institute of Health and Environment, Seoul National University, Seoul, 08826, Republic of Korea.
| | - Yoonhee Kim
- Department of Global Environmental Health, Graduate School of Medicine, University of Tokyo, Tokyo, 113-0033, Japan.
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Song WY, Lv Y, Yin PW, Yang YY, Guo XG. Potential distribution of Leptotrombidium scutellare in Yunnan and Sichuan Provinces, China, and its association with mite-borne disease transmission. Parasit Vectors 2023; 16:164. [PMID: 37194039 DOI: 10.1186/s13071-023-05789-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Accepted: 04/27/2023] [Indexed: 05/18/2023] Open
Abstract
BACKGROUND Leptotrombidium scutellare is one of the six main vectors of scrub typhus in China and is a putative vector of hemorrhagic fever with renal syndrome (HFRS). This mite constitutes a large portion of the chigger mite community in southwest China. Although empirical data on its distribution are available for several investigated sites, knowledge of the species' association with human well-being and involvement in the prevalence of mite-borne diseases remains scarce. METHODS Occurrence data on the chigger mite were obtained from 21 years (2001-2021) of field sampling. Using boosted regression tree (BRT) ecological models based on climate, land cover and elevation variables, we predicted the environmental suitability for L. scutellare in Yunnan and Sichuan Provinces. The potential distribution range and shifts in the study area for near-current and future scenarios were mapped and the scale of L. scutellare interacting with human activities was evaluated. We tested the explanatory power of the occurrence probability of L. scutellare on incidences of mite-borne diseases. RESULTS Elevation and climate factors were the most important factors contributing to the prediction of the occurrence pattern of L. scutellare. The most suitable habitats for this mite species were mainly concentrated around high-elevation areas, with predictions for the future showing a trend towards a reduction. Human activity was negatively correlated with the environmental suitability of L. scutellare. The occurrence probability of L. scutellare in Yunnan Province had a strong explanatory power on the epidemic pattern of HFRS but not scrub typhus. CONCLUSIONS Our results emphasize the exposure risks introduced by L. scutellare in the high-elevation areas of southwest China. Climate change may lead to a range contraction of this species towards areas of higher elevation and lessen the associated exposure risk. A comprehensive understanding of the transmission risk requires more surveillance efforts.
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Affiliation(s)
- Wen-Yu Song
- Vector Laboratory, Institute of Pathogens and Vectors, Yunnan Provincial Key Laboratory for Zoonosis Control and Prevention, Dali University, Dali, 671000, Yunnan, China
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, 650223, Yunnan, China
| | - Yan Lv
- Vector Laboratory, Institute of Pathogens and Vectors, Yunnan Provincial Key Laboratory for Zoonosis Control and Prevention, Dali University, Dali, 671000, Yunnan, China
| | - Peng-Wu Yin
- Vector Laboratory, Institute of Pathogens and Vectors, Yunnan Provincial Key Laboratory for Zoonosis Control and Prevention, Dali University, Dali, 671000, Yunnan, China
| | - Yi-Yu Yang
- Department of Mathematics and Computer Science, Dali University, Dali, 671003, Yunnan, China
| | - Xian-Guo Guo
- Vector Laboratory, Institute of Pathogens and Vectors, Yunnan Provincial Key Laboratory for Zoonosis Control and Prevention, Dali University, Dali, 671000, Yunnan, China.
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Li B, Guo XG, Ren TG, Peng PY, Song WY, Lv Y, Yin PW, Liu Z, Liu XH, Qian TJ. Analysis on infestation and related ecology of chigger mites on large Chinese voles (Eothenomys miletus) in five provincial regions of Southwest China. Int J Parasitol Parasites Wildl 2022; 19:169-179. [PMID: 36177391 PMCID: PMC9513170 DOI: 10.1016/j.ijppaw.2022.08.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 08/30/2022] [Accepted: 08/31/2022] [Indexed: 11/29/2022]
Abstract
Based on a long-term field investigation in the five provincial regions of Southwest China between 2001 and 2019, the present paper studied the infestation and related ecology of chigger mites (chiggers) on the large Chinese vole (Eothenomys miletus), an endemic and dominant rodent species in the regions. A total of 52331 chiggers were collected from 2661 voles, and 52261 mites were identified as 185 species and 13 genera in the family Trombiculidae with very high species diversity. The identified 185 chigger species on E. miletus (a single rodent species) even exceeded those recorded in some countries. The overall infestation prevalence (Pm = 53.96%), mean abundance (MA = 19.64) and mean intensity (MI = 36.39) on E. miletus were much higher than those on some other rodent species in the same regions. Although the species composition showed a moderate similarity (J = 0.63) between male and female hosts (E. miletus), the infestation indices (Pm = 56.25%, MA = 21.67) of chiggers on male hosts were higher than those on the females (Pm = 51.23%, MA = 17.09) (P < 0.05). Two dominant chigger species, Leptotrombidium scutellare (Cr = 19.17%) and L. sinicum (Cr = 11.06%), showed an aggregated distribution pattern among different individuals of their host E. miletus, and a relatively high degree of positive association existed between the two dominant chigger species with PCC = 0.57, DI = 0.60 and OI = 0.62 (x2 = 857.46, P < 0.001). Leptotrombidium densipunctatum, Walchia koi, Helenicula hsui, L. scutellare and W. ewingi showed a high degree of environmental adaptability to their environments with high niche breadths. The theoretical curve of the species abundance distribution of chigger community on E. miletus was successfully fitted with Preston's lognormal distribution model. Based on the theoretical curve fitting, the expected total number of chigger species on E. miletus was roughly estimated to be 223 species, and 38 chigger species were probably missed in the sampling investigation. Chiggers are the common ectoparasites of rodents and vector of scrub typhus, Eothenomys miletus is the reservoir host and infectious source of zoonoses. The dominant chigger specie, Leptotrombidium scutellare, is one of the main and powerful vectors of scrub typhus in China. To study the chigger mites of E. miletus voles in such a wide geographical region.
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Affiliation(s)
- Bei Li
- Institute of Pathogens and Vectors, Yunnan Provincial Key Laboratory for Zoonosis Control and Prevention, Dali University, Dali, Yunnan, 671000, China
| | - Xian-Guo Guo
- Institute of Pathogens and Vectors, Yunnan Provincial Key Laboratory for Zoonosis Control and Prevention, Dali University, Dali, Yunnan, 671000, China
- Corresponding author.
| | - Tian-Guang Ren
- Nursing College of Dali University, Dali, Yunnan, 671000, China
| | - Pei-Ying Peng
- Institute of Microbiology, Qujing Medical College, Qujing, Yunnan, 655011, China
| | - Wen-Yu Song
- Institute of Pathogens and Vectors, Yunnan Provincial Key Laboratory for Zoonosis Control and Prevention, Dali University, Dali, Yunnan, 671000, China
| | - Yan Lv
- Institute of Pathogens and Vectors, Yunnan Provincial Key Laboratory for Zoonosis Control and Prevention, Dali University, Dali, Yunnan, 671000, China
| | - Peng-Wu Yin
- Institute of Pathogens and Vectors, Yunnan Provincial Key Laboratory for Zoonosis Control and Prevention, Dali University, Dali, Yunnan, 671000, China
| | - Zhe Liu
- Institute of Pathogens and Vectors, Yunnan Provincial Key Laboratory for Zoonosis Control and Prevention, Dali University, Dali, Yunnan, 671000, China
- Beijing Health Vocational College, Beijing, 102402, China
| | - Xin-Hang Liu
- Institute of Pathogens and Vectors, Yunnan Provincial Key Laboratory for Zoonosis Control and Prevention, Dali University, Dali, Yunnan, 671000, China
- Central Hospital of Yingkou Economic and Technological Development Zone, Yingkou, Liaoning, 115007, China
| | - Ti-Jun Qian
- Institute of Pathogens and Vectors, Yunnan Provincial Key Laboratory for Zoonosis Control and Prevention, Dali University, Dali, Yunnan, 671000, China
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Chen HF, Peng SH, Tsai KH, Yang CF, Chang MC, Hsueh YL, Su CL, Wang RY, Shu PY, Yang SL. Molecular epidemiology of scrub typhus in Taiwan during 2006-2016. PLoS Negl Trop Dis 2022; 16:e0010369. [PMID: 35486655 PMCID: PMC9094550 DOI: 10.1371/journal.pntd.0010369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Revised: 05/11/2022] [Accepted: 03/29/2022] [Indexed: 12/31/2022] Open
Abstract
Scrub typhus is the most common endemic vector-borne disease in Taiwan. We identified a total of 4,857 laboratory-confirmed cases during 2006-2016 with hyperendemic foci on offshore islands, including Penghu (778 cases, 16.0%) and Kinmen (716 cases, 14.7%), and eastern Taiwan, including Taitung (628 cases, 12.9%) and Hualien (508 cases, 10.5%). Scrub typhus cases occur year-round throughout Taiwan, with a summer peak in June and July. A total of 545 O. tsutsugamushi isolates were successfully obtained from patients infected in diverse geographic areas, including Taiwan and three offshore islands, and the complete open reading frame of the 56 kDa type-specific antigen gene (tsa56) sequence of these isolates was examined. High phylogenetic diversity was found in these isolates, which could be grouped into 36 distinct sequence types. Most isolates belonged to the Karp (49.9%; 272/545), followed by the TW-22 (17.8%; 97/454) and Kawasaki (14.7%; 80/545) genotypes. In conclusion, our data indicate the widespread presence of tsa56 genotypes closely related to Thailand and Korean strains and the presence of the unique endemic strains TW-12, TW-22, TW-29, and TW-36 in Taiwan.
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Affiliation(s)
- Hsiang-Fei Chen
- Center for Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taiwan, Republic of China
| | - Shih-Huan Peng
- Center for Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taiwan, Republic of China
| | - Kun-Hsien Tsai
- Institute of Environmental and Occupational Health Sciences, College of Public Health, National Taiwan University, Taipei, Republic of China
- Department of Public Health, College of Public Health, National Taiwan University, Taipei, Republic of China
| | - Cheng-Fen Yang
- Center for Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taiwan, Republic of China
| | - Mei-Chun Chang
- Center for Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taiwan, Republic of China
| | - Yeou-Lin Hsueh
- Center for Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taiwan, Republic of China
| | - Chien-Ling Su
- Center for Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taiwan, Republic of China
| | - Ruo-Yu Wang
- Center for Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taiwan, Republic of China
| | - Pei-Yun Shu
- Center for Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taiwan, Republic of China
- * E-mail: (P-YS); (S-LY)
| | - Su-Lin Yang
- Center for Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taiwan, Republic of China
- * E-mail: (P-YS); (S-LY)
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Wang T, Meng F, Che T, Chen J, Zhang H, Ji Y, Fan Z, Zhao G, Zhang W, Jiang B, Xu Q, Lv C, Shi T, Ruan S, Liu L, Liu W, Yang Y, Fang L. Mapping the distributions of blood-sucking mites and mite-borne agents in China: a modeling study. Infect Dis Poverty 2022; 11:41. [PMID: 35397554 PMCID: PMC8994071 DOI: 10.1186/s40249-022-00966-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 03/28/2022] [Indexed: 11/10/2022] Open
Abstract
Background Emerging mite-borne pathogens and associated disease burdens in recent decades are raising serious public health concerns, yet their distributions and ecology remain under-investigated. We aim to describe the geographical distributions of blood-sucking mites and mite-borne agents and to assess their ecological niches in China. Methods We mapped 549 species of blood-sucking mites belonging to 100 genera at the county level and eight mite-associated agents detected from 36 species of blood-sucking mites in China during 1978–2020. Impacts of climatic and environmental factors on the ecology of 21 predominant vector mites and a leading pathogen, Orientia tsutsugamushi, were assessed using boosted regression tree (BRT) models, and model-predicted risks were mapped. We also estimated the model-predicted number, area and population size of affected counties for each of the 21 mite species in China. Results Laelaps echidninus is the leading mite species that potentially affects 744 million people, followed by La. jettmari (517 million) and Eulaelaps stabularis (452 million). Leptotrombidium scutellare is the mite species harboring the highest variety of mite-borne agents including four Rickettsia species and two viruses, followed by Eu. stabularis (2 agents), L. palpale (2) and La. echidninus (2). The top two agents that parasitize the largest number of mite species are O. tsutsugamushi (28 species) and hantavirus (8). Mammalian richness, annual mean temperature and precipitation of the driest quarter jointly determine the ecology of the mites, forming four clusters of major mite species with distinct geographic distributions. High-risk areas of O. tsutsugamushi are mainly distributed in southern and eastern coastal provinces where 71.5 million people live. Conclusions Ecological niches of major mite species and mite-borne pathogens are much more extensive than what have been observed, necessitating expansion of current filed surveillance. Graphic Abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s40249-022-00966-0.
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Wulandhari SA, Paladsing Y, Saesim W, Charoennitiwat V, Sonthayanon P, Kumlert R, Morand S, Sumruayphol S, Chaisiri K. High prevalence and low diversity of chigger infestation in small mammals found in Bangkok Metropolitan parks. MEDICAL AND VETERINARY ENTOMOLOGY 2021; 35:534-546. [PMID: 34021500 DOI: 10.1111/mve.12531] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 05/03/2021] [Accepted: 05/10/2021] [Indexed: 06/12/2023]
Abstract
Chiggers are recognized as vectors of scrub typhus disease caused by the bacteria, Orientia tsutsugamushi. The risk of disease exposure is mainly related to chigger bites when humans or animals roam into vector-infested habitats. In big cities, urban public parks could provide areas for the animal-human interface and zoonotic pathogen transmission. The ecology and epidemiology of urban scrub typhus are still poorly understood in Thailand. Small mammals were trapped and examined for chigger infestation in urban public parks across metropolitan Bangkok, Thailand. We found a high prevalence of infestation (76.8%) with surprisingly low diversity. Two chigger species, Leptotrombidium deliense and Ascoschoengastia indica, were identified using morphological characteristics and molecular confirmation. The generalized linear model identified host intrinsic variables (i.e. body mass index) with host density, habitat composition and open field as the extrinsic factors explaining the abundance of chigger infestation. The bacteria O. tsutsugamushi was not detected in chiggers (90 chigger-pooled samples) and animal host tissues (164 spleen samples). However, the existence of chigger vectors calls for the Bangkok Metropolitan Administration and public health authorities to develop a comprehensive scrub typhus monitoring and prevention strategy in the parks and nearby communities.
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Affiliation(s)
- S A Wulandhari
- Department of Medical Entomology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Y Paladsing
- Department of Helminthology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - W Saesim
- Environment Department, Bangkok Metropolitan Administration, Bangkok, Thailand
| | - V Charoennitiwat
- Department of Helminthology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - P Sonthayanon
- Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - R Kumlert
- Division of Vector-Borne Diseases, Department of Disease Control, Ministry of Public Health, Nonthaburi, Thailand
| | - S Morand
- Department of Helminthology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- CNRS-CIRAD, Faculty of Veterinary Technology, Kasetsart University, Bangkok, Thailand
| | - S Sumruayphol
- Department of Medical Entomology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - K Chaisiri
- Department of Helminthology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
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Lee IY, Lim JW, Seo JH, Kim HC, Lee KJ, Yong TS, Lee WJ, Yu JR, Sim S. Geographical Distribution and Epidemiologic Factors of Chigger Mites on Apodemus agrarius during Autumn in Korea. THE KOREAN JOURNAL OF PARASITOLOGY 2021; 59:473-479. [PMID: 34724766 PMCID: PMC8561048 DOI: 10.3347/kjp.2021.59.5.473] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/22/2021] [Accepted: 09/23/2021] [Indexed: 11/23/2022]
Abstract
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.
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Affiliation(s)
- In Yong Lee
- Department of Environmental Medical Biology and Institute of Tropical Medicine, Yonsei University College of Medicine, Seoul 03722, Korea
| | - Jae-Won Lim
- Biological Resources Research Department, National Institute of Biological Resources, Inchoen 22689, Korea
| | - Jang Hoon Seo
- Department of Biomedical Laboratory Science, Shinhan University, Uijeongbu 11644, Korea
| | - Heung Chul Kim
- 5th Medical Detachment, 168th Multifunctional Medical Battalion, 65th Medical Brigade, Unit 15247, APO 96205-5247, USA
| | - Ku Jae Lee
- Department of Environmental Medical Biology, Wonju Yonsei University College of Medicine, Wonju 26426, Korea
| | - Tai-Soon Yong
- Department of Environmental Medical Biology and Institute of Tropical Medicine, Yonsei University College of Medicine, Seoul 03722, Korea
| | - Won-Ja Lee
- Department of Environmental Medical Biology and Institute of Tropical Medicine, Yonsei University College of Medicine, Seoul 03722, Korea
| | - Jae-Ran Yu
- KU Open Innovation Center, Department of Environmental and Tropical Medicine, School of Medicine, Konkuk University, Chungju 27478, Korea
| | - Seobo Sim
- KU Open Innovation Center, Department of Environmental and Tropical Medicine, School of Medicine, Konkuk University, Chungju 27478, Korea
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Wu DL, Shih HC, Wang JK, Teng HJ, Kuo CC. Commensal Rodent Habitat Expansion Enhances Arthropod Disease Vectors on a Tropical Volcanic Island. Front Vet Sci 2021; 8:736216. [PMID: 34692809 PMCID: PMC8531417 DOI: 10.3389/fvets.2021.736216] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2021] [Accepted: 08/31/2021] [Indexed: 11/28/2022] Open
Abstract
On volcanic islands, the release of animals from predators and competitors can lead to increased body size and population density as well as the expanded habitat use of introduced animals relative to their mainland counterparts. Such alterations might facilitate the spread of diseases on islands when these exotic animals also carry pathogenic agents; however, this has rarely been investigated. The commensal Asian house rat (Rattus tanezumi) is confined to human residential surroundings in mainland Taiwan but can be observed in the forests of nearby Orchid Island, which is a tropical volcanic island. Orchid Island is also a hot spot for scrub typhus, a lethal febrile disease transmitted by larval trombiculid mites (chiggers) that are infected primarily with the rickettsia Orientia tsutsugamushi (OT). We predicted an increase in chigger abundance when rodents (the primary host of chiggers) invade forests from human settlements since soils are largely absent in the latter habitat but necessary for the survival of nymphal and adult mites. A trimonthly rodent survey at 10 sites in three habitats (human residential, grassland, and forest) found only R. tanezumi and showed more R. tanezumi and chiggers in forests than in human residential sites. There was a positive association between rodent and chigger abundance, as well as between rodent body weight and chigger load. Lastly, >95% of chiggers were Leptotrombidium deliense and their OT infection rates were similar among all habitats. Our study demonstrated potentially elevated risks of scrub typhus when this commensal rat species is allowed to invade natural habitats on islands. Additionally, while the success of invasive species can be ascribed to their parasites being left behind, island invaders might instead obtain more parasites if the parasite requires only a single host (e.g., trombiculid mite), is a host generalist (e.g., L. deliense), and is transferred from unsuitable to suitable habitats (i.e., human settlements on the mainland to forests on an island).
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Affiliation(s)
- De-Lun Wu
- Department of Life Science, National Taiwan Normal University, Taipei, Taiwan
| | - Han-Chun Shih
- Epidemic Intelligence Center, Centers for Disease Control, Ministry of Health and Welfare, Taipei, Taiwan
| | - Jen-Kai Wang
- Department of Life Science, National Taiwan Normal University, Taipei, Taiwan
| | - Hwa-Jen Teng
- Center for Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taipei, Taiwan
| | - Chi-Chien Kuo
- Department of Life Science, National Taiwan Normal University, Taipei, Taiwan
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Nationwide Incidence of Chigger Mite Populations and Molecular Detection of Orientia tsutsugamushi in the Republic of Korea, 2020. Microorganisms 2021; 9:microorganisms9081563. [PMID: 34442642 PMCID: PMC8400602 DOI: 10.3390/microorganisms9081563] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 07/02/2021] [Accepted: 07/21/2021] [Indexed: 11/17/2022] Open
Abstract
The Korea Disease Control and Prevention Agency has established regional centers at 16 locations to monitor vectors and pathogens. We investigated the geographical and temporal distribution of chigger mite populations to understand tsutsugamushi disease epidemiology in 2020. To monitor weekly chigger mite populations, 3637 chigger mites were collected from sticky chigger mite traps in autumn. Chigger mites appeared from the first week of October to the third week of December, peaking in the fourth week of October. The predominant species were Leptotrombidium scutellare, Leptotrombidium palpale, Neotrombicula kwangneungensis, Neotrombicula tamiyai, and Leptotrombidium pallidum. To monitor Orientia tsutsugamushi infection in chigger mites, 50,153 chigger mites were collected from 499 trapped wild rodents in spring and autumn, with a chigger index of 100.5. Approximately 50% of chigger mites were pooled into 998 pools, and the minimum infection rate (MIR) of O. tsutsugamushi was 0.1%. Jeongeup had the highest MIR for O. tsutsugamushi (0.7%). The Kato-related genotype was the most common (52.2%), followed by the Karp-related (17.4%), Boryong (13.0%), JG-related (8.7%), Shimokoshi (4.3%), and Kawasaki (4.3%) genotypes. Ecological and geographical studies focusing on the basic ecology and pathology of mites will improve our understanding of tsutsugamushi disease risks in the Republic of Korea.
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Bang MS, Kim CM, Pyun SH, Kim DM, Yun NR. Molecular investigation of tick-borne pathogens in ticks removed from tick-bitten humans in the southwestern region of the Republic of Korea. PLoS One 2021; 16:e0252992. [PMID: 34129613 PMCID: PMC8205137 DOI: 10.1371/journal.pone.0252992] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 05/26/2021] [Indexed: 11/19/2022] Open
Abstract
In this study, we investigated the presence of tick-borne pathogens in ticks removed from tick-bitten humans in the southwestern provinces of the Republic of Korea (ROK). We identified 33 ticks from three tick species, namely Amblyomma testudinarium (60.6%), Haemaphysalis longicornis (27.3%), and Ixodes nipponensis (12.1%) in order of occurrence via morphology and 16S rDNA-targeting polymerase chain reaction (PCR). Tick-borne pathogens were detected in 16 ticks using pathogen-specific PCR. From the results, 12 ticks (36.4%) tested positive for spotted fever group (SFG) Rickettsia: Rickettsia monacensis (1/12), R. tamurae (8/12), and Candidatus Rickettsia jingxinensis (3/12). Three ticks (9.1%) were positive for Anaplasma phagocytophilum. In addition, three ticks (9.1%) tested positive for Babesia gibsoni (1/3) and B. microti (2/3). In conclusion, we identified three tick species; the most common species was A. testudinarium, followed by H. longicornis and I. nipponensis. SFG Rickettsia, A. phagocytophilum, and Babesia spp. were the most frequently detected pathogens in ticks removed from tick-bitten humans. To our knowledge, this is the first report of R. tamurae and Ca. R. jingxinensis detection in Korea. The present results will contribute to the understanding of tick-borne infections in animals and humans in the ROK.
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Affiliation(s)
- Mi Seon Bang
- Department of Medical Science, College of Medicine, Chosun University, Gwangju, Republic of Korea
| | - Choon-Mee Kim
- Premedical Science, College of Medicine, Chosun University, Gwangju, Republic of Korea
| | - Sang-Hyun Pyun
- Graduate School of Chosun University, Gwangju, Republic of Korea
| | - Dong-Min Kim
- Department of Internal Medicine, College of Medicine, Chosun University, Gwangju, Republic of Korea
- * E-mail:
| | - Na Ra Yun
- Department of Internal Medicine, College of Medicine, Chosun University, Gwangju, Republic of Korea
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Linsuwanon P, Auysawasdi N, Wongwairot S, Leepitakrat S, Rodkhamtook W, Wanja E, Monkanna T, Wegner M, Davidson S, Poovorawan Y, Poole-Smith B, Limsuwon C, McCardle P. Assessing scrub typhus and rickettsioses transmission risks in the Chiang Rai province of northern Thailand. Travel Med Infect Dis 2021; 42:102086. [PMID: 34044127 DOI: 10.1016/j.tmaid.2021.102086] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 05/19/2021] [Accepted: 05/20/2021] [Indexed: 01/25/2023]
Abstract
BACKGROUND Scrub typhus is an important disease in the Asia-Pacific countries with increasing relevance for public health worldwide. Entomological risk assessment for scrub typhus and rickettsial disease in Phu Chi Fah village-Chiang Rai was performed to determine areas at greatest risk for disease transmission in order to increase awareness of diseases to travelers and healthcare workers. METHODS From 2016 to 2018, rodents and chiggers were collected from 7 sites covering residential, grassland, and forest areas to determine the prevalence of pathogen of interest. The correlation between land type and vector-host-pathogen interaction system was investigated. RESULT High prevalence of O. tsutsugamushi-infected and Rickettsia-infected chiggers was observed especially in areas with grassland and forest ecotones. Chigger and rodent species composition were negatively associated with the level of human disturbance. Increased density of rodents was responsible for a higher abundance of chigger population and increased prevalence of O. tsutsugmaushi infection in chigger in the following year. CONCLUSION Communities in the study areas have an increased exposure risk to scrub typhus and potentially spotted fever group rickettsiosis. Travellers to this endemic area should pay more attention pathogen risks so as to avoid vector and disease exposure. Seasonal rodenticidal activity may help migitate the risk of pathogen transmission.
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Affiliation(s)
- Piyada Linsuwanon
- Department of Entomology, US Medical Directorate-Armed Forces Research Institute of Medical Science, Bangkok, Thailand.
| | - Nutthanun Auysawasdi
- Department of Entomology, US Medical Directorate-Armed Forces Research Institute of Medical Science, Bangkok, Thailand
| | - Sirima Wongwairot
- Department of Entomology, US Medical Directorate-Armed Forces Research Institute of Medical Science, Bangkok, Thailand
| | - Surachai Leepitakrat
- Department of Entomology, US Medical Directorate-Armed Forces Research Institute of Medical Science, Bangkok, Thailand
| | - Wuttikon Rodkhamtook
- Research Division, Royal Thai Army Component-Armed Forces Research Institute of Medical Science, Bangkok, Thailand
| | - Elizabeth Wanja
- Department of Entomology, US Medical Directorate-Armed Forces Research Institute of Medical Science, Bangkok, Thailand
| | - Taweesak Monkanna
- Department of Entomology, US Medical Directorate-Armed Forces Research Institute of Medical Science, Bangkok, Thailand
| | - Matthew Wegner
- Department of Veterinary Medicine, US Medical Directorate-Armed Forces Research Institute of Medical Science, Bangkok, Thailand
| | - Silas Davidson
- Department of Entomology, US Medical Directorate-Armed Forces Research Institute of Medical Science, Bangkok, Thailand
| | - Yong Poovorawan
- Center of Excellence in Clinical Virology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Betty Poole-Smith
- Department of Entomology, US Medical Directorate-Armed Forces Research Institute of Medical Science, Bangkok, Thailand
| | - Chawin Limsuwon
- Department of Entomology, US Medical Directorate-Armed Forces Research Institute of Medical Science, Bangkok, Thailand
| | - Patrick McCardle
- Department of Entomology, US Medical Directorate-Armed Forces Research Institute of Medical Science, Bangkok, Thailand
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Bahk YY, Jun H, Park SH, Jung H, Jegal S, Kim-Jeon MD, Roh JY, Lee WG, Ahn SK, Lee J, Joo K, Gong YW, Kwon MJ, Kim TS. Surveillance of Chigger Mite Vectors for Tsutsugamushi Disease in the Hwaseong Area, Gyeonggi-do, Republic of Korea, 2015. THE KOREAN JOURNAL OF PARASITOLOGY 2020; 58:301-308. [PMID: 32615743 PMCID: PMC7338901 DOI: 10.3347/kjp.2020.58.3.301] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Accepted: 04/20/2020] [Indexed: 11/25/2022]
Abstract
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.
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Affiliation(s)
- Young Yil Bahk
- Department of Biotechnology, College of Biomedical and Health Science, Konkuk University, Chungju 27478, Korea
| | - Hojong Jun
- Department of Tropical Medicine, Inha University College of Medicine, Incheon 22212, Korea
| | - Seo Hye Park
- Department of Tropical Medicine, Inha University College of Medicine, Incheon 22212, Korea
| | - Haneul Jung
- Department of Tropical Medicine, Inha University College of Medicine, Incheon 22212, Korea
| | - Seung Jegal
- Department of Infectious Diseases Diagnosis, Incheon Metropolitan City Institute of Public Health and Environment, Incheon 22320, Korea
| | - Myung-Deok Kim-Jeon
- Department of Infectious Diseases Diagnosis, Incheon Metropolitan City Institute of Public Health and Environment, Incheon 22320, Korea
| | - Jong Yul Roh
- Division of Vectors and Parasitic Diseases, Korea Centers for Disease Control and Prevention, Osong 28159, Korea
| | - Wook-Gyo Lee
- Division of Vectors and Parasitic Diseases, Korea Centers for Disease Control and Prevention, Osong 28159, Korea
| | - Seong Kyu Ahn
- Department of Tropical Medicine, Inha University College of Medicine, Incheon 22212, Korea
| | - Jinyoung Lee
- Department of Tropical Medicine, Inha University College of Medicine, Incheon 22212, Korea
| | - Kwangsig Joo
- Department of Infectious Diseases Diagnosis, Incheon Metropolitan City Institute of Public Health and Environment, Incheon 22320, Korea
| | - Young Woo Gong
- Department of Infectious Diseases Diagnosis, Incheon Metropolitan City Institute of Public Health and Environment, Incheon 22320, Korea
| | - Mun Ju Kwon
- Department of Infectious Diseases Diagnosis, Incheon Metropolitan City Institute of Public Health and Environment, Incheon 22320, Korea
| | - Tong-Soo Kim
- Department of Tropical Medicine, Inha University College of Medicine, Incheon 22212, Korea
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Wei CY, Wang JK, Shih HC, Wang HC, Kuo CC. Invasive plants facilitated by socioeconomic change harbor vectors of scrub typhus and spotted fever. PLoS Negl Trop Dis 2020; 14:e0007519. [PMID: 31961870 PMCID: PMC6994164 DOI: 10.1371/journal.pntd.0007519] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2019] [Revised: 01/31/2020] [Accepted: 11/25/2019] [Indexed: 12/04/2022] Open
Abstract
BACKGROUND Ecological determinants of most emerging vector-borne diseases are understudied, particularly for neglected tropical disease. Moreover, although socioeconomic impacts can have significant downstream effects on human risks to vector-borne diseases via a change in land cover, particularly facilitating the invasion of exotic plants, related studies remains very scarce. Scrub typhus and spotted fever are neglected diseases emerging around the globe and are transmitted by chigger mites and ticks infective of Orientia tsutsugamushi and Rickettsia spp., respectively, with small mammals as the primary hosts of both vectors. METHODOLOGY/PRINCIPAL FINDINGS We investigated how invasions of the plant Leucaena leucocephala caused by widespread abandonment of farmlands driven by industrialization affected abundance of chiggers and ticks in Penghu Island, Taiwan. We determined ectoparasite abundance by trapping small mammals in three types of habitats (invasion site, agricultural field, human residential) every two months for a year. Based on ectoparasite burdens, invasion sites harbored more chiggers and ticks than the other two habitats. Furthermore, hosts maintained higher burdens of both vectors in early winter and burdens of chiggers were more stable across seasons in invasion sites, suggesting that sites with invasive plants could be a temporary refuge for both vectors and might help mitigate the negative influence of unfavorable climate. Infective rates of O. tsutsugamushi in chiggers and Rickettsia in ticks were also consistently not lower in invasion sites. Top soil temperature and relative humidity were similar across the three habitats, but invasion sites contained more of the rat Rattus losea, on which chiggers and ticks were more engorged than those from the most commonly trapped species (Suncus murinus shrew), indicating that abundance of the host R. losea instead of microclimate might better determine the abundance of both vectors. CONCLUSIONS/SIGNIFICANCE This study highlights an important but largely neglected issue that socioeconomic change can have unexpected consequences for human health induced particularly by invasive plants, which could become a hotspot for emerging infectious diseases but usually are very hard to be eradicated. In the future, a more comprehensive approach that integrates socio-economics, land use, exotic species, and human health should be considered to fully understand potential emergence of vector-borne diseases.
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Affiliation(s)
- Chen-Yu Wei
- Department of Life Science, National Taiwan Normal University, Taipei, Taiwan
| | - Jen-Kai Wang
- Department of Life Science, National Taiwan Normal University, Taipei, Taiwan
| | - Han-Chun Shih
- Center for Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taipei, Taiwan
| | - Hsi-Chieh Wang
- Center for Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taipei, Taiwan
- Institute of Environmental and Occupational Health Sciences, College of Public Health, National Taiwan University, Taipei, Taiwan
| | - Chi-Chien Kuo
- Department of Life Science, National Taiwan Normal University, Taipei, Taiwan
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Kim SY, Gill B, Song BG, Chu H, Park WI, Lee HI, Shin EH, Cho SH, Roh JY. Annual Fluctuation in Chigger Mite Populations and Orientia Tsutsugamushi Infections in Scrub Typhus Endemic Regions of South Korea. Osong Public Health Res Perspect 2019; 10:351-358. [PMID: 31897364 PMCID: PMC6927423 DOI: 10.24171/j.phrp.2019.10.6.05] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Objectives Chigger mites are vectors for scrub typhus. This study evaluated the annual fluctuations in chigger mite populations and Orientia tsutsugamushi infections in South Korea. Methods During 2006 and 2007, chigger mites were collected monthly from wild rodents in 4 scrub typhus endemic regions of South Korea. The chigger mites were classified based on morphological characteristics, and analyzed using nested PCR for the detection of Orientia tsutsugamushi. Results During the surveillance period, the overall trapping rate for wild rodents was 10.8%. In total, 17,457 chigger mites (representing 5 genera and 15 species) were collected, and the average chigger index (representing the number of chigger mites per rodent), was 31.7. The monthly chigger index was consistently high (> 30) in Spring (March to April) and Autumn (October to November). The mite species included Leptotrombidium pallidum (43.5%), L. orientale (18.9%), L. scutellare (18.1%), L. palpale (10.6%), and L. zetum (3.6%). L. scutellare and L. palpale populations, were relatively higher in Autumn. Monthly O. tsutsugamushi infection rates in wild rodents (average: 4.8%) and chigger mites (average: 0.7%) peaked in Spring and Autumn. Conclusion The findings demonstrated a bimodal pattern of the incidence of O. tsutsugamushi infections. Higher infection rates were observed in both wild rodents and chigger mites, in Spring and Autumn. However, this did not reflect the unimodal incidence of scrub typhus in Autumn. Further studies are needed to identify factors, such as human behavior and harvesting in Autumn that may explain this discordance.
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Affiliation(s)
- Seong Yoon Kim
- Division of Vectors and Parasitic Diseases, Korea Centers for Disease Control and Prevention, Cheongju, Korea
| | - Byoungchul Gill
- Division of Laboratory Diagnosis Management, Korea Centers for Disease Control and Prevention, Cheongju, Korea
| | - Bong Gu Song
- Division of Vectors and Parasitic Diseases, Korea Centers for Disease Control and Prevention, Cheongju, Korea
| | - Hyuk Chu
- Division of Bacterial Disease Research, Korea Centers for Disease Control and Prevention, Cheongju, Korea
| | - Won Il Park
- Division of Vectors and Parasitic Diseases, Korea Centers for Disease Control and Prevention, Cheongju, Korea
| | - Hee Il Lee
- Division of Vectors and Parasitic Diseases, Korea Centers for Disease Control and Prevention, Cheongju, Korea
| | - E-Hyun Shin
- Division of Vectors and Parasitic Diseases, Korea Centers for Disease Control and Prevention, Cheongju, Korea
| | - Shin-Hyeong Cho
- Division of Vectors and Parasitic Diseases, Korea Centers for Disease Control and Prevention, Cheongju, Korea
| | - Jong Yul Roh
- Division of Vectors and Parasitic Diseases, Korea Centers for Disease Control and Prevention, Cheongju, Korea
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Elliott I, Pearson I, Dahal P, Thomas NV, Roberts T, Newton PN. Scrub typhus ecology: a systematic review of Orientia in vectors and hosts. Parasit Vectors 2019; 12:513. [PMID: 31685019 PMCID: PMC6829833 DOI: 10.1186/s13071-019-3751-x] [Citation(s) in RCA: 88] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Accepted: 10/12/2019] [Indexed: 01/06/2023] Open
Abstract
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.
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Affiliation(s)
- Ivo Elliott
- Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit, Microbiology Laboratory, Mahosot Hospital, Vientiane, Lao PDR
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Isabelle Pearson
- Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit, Microbiology Laboratory, Mahosot Hospital, Vientiane, Lao PDR
| | - Prabin Dahal
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
- Worldwide Anti Malarial Resistance Network, University of Oxford, Oxford, UK
- Linacre College, University of Oxford, St Cross Road, Oxford, UK
| | - Nigel V. Thomas
- Worldwide Anti Malarial Resistance Network, University of Oxford, Oxford, UK
| | - Tamalee Roberts
- Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit, Microbiology Laboratory, Mahosot Hospital, Vientiane, Lao PDR
| | - Paul N. Newton
- Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit, Microbiology Laboratory, Mahosot Hospital, Vientiane, Lao PDR
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
- Worldwide Anti Malarial Resistance Network, University of Oxford, Oxford, UK
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16
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Bang MS, Kim CM, Park JW, Chung JK, Kim DM, Yun NR. Prevalence of Orientia tsutsugamushi, Anaplasma phagocytophilum and Leptospira interrogans in striped field mice in Gwangju, Republic of Korea. PLoS One 2019; 14:e0215526. [PMID: 31419222 PMCID: PMC6697328 DOI: 10.1371/journal.pone.0215526] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 04/03/2019] [Indexed: 11/18/2022] Open
Abstract
This study investigated the prevalence of Orientia tsutsugamushi, Anaplasma phagocytophilum, and Leptospira interrogans in wild rodents through molecular detection using organ samples and through serological assay using blood samples of mice collected from two distinct sites in Gwangju Metropolitan City, Republic of Korea (ROK). A total of 47 wild rodents, identified as Apodemus agrarius (A. agrarius), were captured from June to August 2016. The seroprevalence of antibodies against bacterial pathogens in A. agrarius sera was analyzed; 17.4% (8/46) were identified as O. tsutsugamushi through indirect immunofluorescence assay and 2.2% (1/46) were identified as Leptospira species through passive hemagglutination assay. Using polymerase chain reaction, the spleen, kidney and blood samples were investigated for the presence of O. tsutsugamushi, A. phagocytophilum, and L. interrogans. Out of the 47 A. agrarius, 19.1% (9/47) were positive for A. phagocytophilum and 6.4% (3/47) were positive for L. interrogans, while none were positive for O. tsutsugamushi. Four out of 46 (8.7%) blood samples, six out of 45 (13.3%) spleen samples, and one out of 47 (2.1%) kidney samples were positive for A. phagocytophilum. Three out of 47 (6.4%) kidney samples were positive for L. interrogans. The sequencing results of PCR positive samples demonstrated > 99% similarity with A. phagocytophilum and L. interrogans sequences. A. phagocytophilum was mostly detected in the spleen, whereas L. interrogans was mostly detected in the kidneys. Notably, A. phagocytophilum and L. interrogans were detected in A. agrarius living in close proximity to humans in the metropolitan suburban areas. The results of this study indicate that rodent-borne bacteria may be present in wild rodents in the metropolitan suburban areas of ROK.
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Affiliation(s)
- Mi-Seon Bang
- Department of Internal Medicine, College of Medicine, Chosun University, Gwangju, Republic of Korea
| | - Choon-Mee Kim
- Premedical Science, College of Medicine, Chosun University, Gwangju, Republic of Korea
| | - Jung Wook Park
- Division of Infectious Disease Investigation, Health and Environment Research Institute of Gwangju City, Gwangju, Republic of Korea
| | - Jae Keun Chung
- Division of Infectious Disease Investigation, Health and Environment Research Institute of Gwangju City, Gwangju, Republic of Korea
| | - Dong-Min Kim
- Department of Internal Medicine, College of Medicine, Chosun University, Gwangju, Republic of Korea
| | - Na Ra Yun
- Department of Internal Medicine, College of Medicine, Chosun University, Gwangju, Republic of Korea
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Park SW, Lee CS, Kim JH, Bae IG, Moon C, Kwak YG, Kim BN, Lee JH, Ryu SY, Jang HC, Hur J, Jun JB, Jung Y, Chang HH, Kim YK, Hwang JH, Kim YS, Jeong HW, Song KH, Park WB, Kim ES, Oh MD. Severe fever with thrombocytopenia syndrome: comparison with scrub typhus and clinical diagnostic prediction. BMC Infect Dis 2019; 19:174. [PMID: 30782137 PMCID: PMC6381645 DOI: 10.1186/s12879-019-3773-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Accepted: 02/01/2019] [Indexed: 01/21/2023] Open
Abstract
Background Severe fever with thrombocytopenia syndrome (SFTS) is emerging in Asian 3 countries, China, Japan and Korea, which are scrub typhus endemic areas, and its incidence is increasing. As the two infections overlap epidemiologically and clinically and the accessibility or sensitivity of diagnostic tests is limited, early clinical prediction may be useful for diagnostic and therapeutic purposes. Methods Patients aged ≥16 years who were clinically suspected and laboratory-confirmed to be infected with Orientia tsutsugamushi or the SFTS virus in South Korea were enrolled. Clinical and laboratory parameters were compared. Scrub typhus was further subclassified according to the status of eschar and skin rash. An SFTS prediction scoring tool was generated based on a logistic regression analysis of SFTS compared with scrub typhus. Results The analysis was performed on 255 patients with scrub typhus and 107 patients with SFTS. At initial presentation, subjective symptoms except for gastrointestinal symptoms, were more prominent in scrub typhus patients. In addition to the characteristic eschar and skin rash, headache was significantly more prominent in scrub typhus, while laboratory abnormalities were more prominent in SFTS. Leukopenia (white blood cell count < 4000/mm3; odds ratio [OR] 30.13), thrombocytopenia (platelet count < 80,000 /mm3; OR 19.73) and low C-reactive protein (< 1 mg/dL; OR 67.46) were consistent risk factors for SFTS (all P < 0.001). A prediction score was generated using these 3 variables, and a score ≥ 2 had a sensitivity of 93.1% (95% confidence interval [CI], 87.9–96.4%) and a specificity of 96.1% (95% CI, 93.8–97.6%) for SFTS. Conclusion This prediction scoring tool may be useful for differentiating SFTS from eschar- or skin rash-negative scrub typhus. It is a simple and readily applicable tool with potential for use in primary care settings.
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Affiliation(s)
- Sang-Won Park
- Department of Internal Medicine, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 03080, the Republic of Korea.,Department of Internal Medicine, Boramae Medical Center, Seoul, Republic of Korea
| | - Chang-Seop Lee
- Department of Internal Medicine, Chonbuk National University Medical School, Jeonju, Republic of Korea
| | - Jeong-Han Kim
- Department of Internal Medicine, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 03080, the Republic of Korea
| | - In-Gyu Bae
- Department of Internal Medicine, Gyeongsang National University School of Medicine, Jinju, Republic of Korea
| | - Chisook Moon
- Department of Internal Medicine, Inje University College of Medicine, Busan, Republic of Korea
| | - Yee Gyung Kwak
- Department of Internal Medicine, Inje University College of Medicine, Busan, Republic of Korea
| | - Baek-Nam Kim
- Department of Internal Medicine, Inje University College of Medicine, Busan, Republic of Korea
| | - Jae Hoon Lee
- Department of Internal Medicine, Wonkwang University School of Medicine, Iksan, Republic of Korea
| | - Seong Yeol Ryu
- Department of Internal Medicine, Keimyung University Dongsan Medical Center, Daegu, Republic of Korea
| | - Hee-Chang Jang
- Department of Infectious Diseases, Chonnam National University Medical School, Gwangju, Republic of Korea
| | - Jian Hur
- Department of Internal Medicine, Yeungnam University College of Medicine, Daegu, Republic of Korea
| | - Jae-Bum Jun
- Department of Internal Medicine, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Republic of Korea
| | - Younghee Jung
- Department of Internal Medicine, Hallym University Sacred Heart Hospital, Anyang, Republic of Korea
| | - Hyun-Ha Chang
- Department of Internal Medicine, School of Medicine, Kyungpook National University Kyungpook National University Hospital, Daegu, Republic of Korea
| | - Young Keun Kim
- Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea
| | - Jeong-Hwan Hwang
- Department of Internal Medicine, Chonbuk National University Medical School, Jeonju, Republic of Korea
| | - Yeon-Sook Kim
- Department of Internal Medicine, Chungnam National University School of Medicine, Daejeon, Republic of Korea
| | - Hye Won Jeong
- Department of Internal Medicine, Chungbuk National University College of Medicine, Cheongju, Republic of Korea
| | - Kyoung-Ho Song
- Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Republic of Korea
| | - Wan Beom Park
- Department of Internal Medicine, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 03080, the Republic of Korea
| | - Eu Suk Kim
- Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Republic of Korea
| | - Myoung-Don Oh
- Department of Internal Medicine, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 03080, the Republic of Korea.
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Takhampunya R, Korkusol A, Promsathaporn S, Tippayachai B, Leepitakrat S, Richards AL, Davidson SA. Heterogeneity of Orientia tsutsugamushi genotypes in field-collected trombiculid mites from wild-caught small mammals in Thailand. PLoS Negl Trop Dis 2018; 12:e0006632. [PMID: 30011267 PMCID: PMC6062101 DOI: 10.1371/journal.pntd.0006632] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 07/26/2018] [Accepted: 06/22/2018] [Indexed: 12/30/2022] Open
Abstract
Trombiculid mites are the vectors of scrub typhus, with infected larval mites (chiggers) transmitting the causative agent, Orientia tsutsugamushi, during feeding. Co-existence of multiple O. tsutsugamushi strains within infected mites has previously been reported in naturally infected, laboratory-reared mite lines using molecular methods to characterize the 56-kDa type-specific antigen (TSA) gene. In the current study, more advanced next-generation sequencing technology was used to reveal the heterogeneity of O. tsutsugamushi genotypes in field-collected trombiculid mites from rodents and small mammals in scrub typhus-endemic areas of Thailand. Twenty-eight trombiculid mites collected from 10 small mammals were positive for O. tsutsugamushi, corresponding to a prevalence rate of 0.7% within the mite population. Twenty-four of the infected mites were Leptotrombidium spp., indicating that this genus is the main vector for O. tsutsugamushi transmission in Thailand. In addition, O. tsutsugamushi was detected in the mite genera Ascoschoengastia, Blankaartia, Gahrliepia, and Lorillatum. Of the 10 infested small animal hosts, six had 2-10 infected mites feeding at the time of collection. Deep sequencing was used to characterize mixed infections (two to three O. tsutsugamushi genotypes within an individual mite), and 5 of the 28 infected mites (17.9%) contained mixed infections. Additionally, 56-kDa TSA gene sequence analysis revealed identical bacterial genotypes among co-feeding mites with single or mixed infections. These results suggest that co-feeding transmission may occur during the feeding process, and could explain the occurrence of mixed infections in individual mites, as well as the recovery of multiple infected mites from the same host. This study also revealed highly diverse within-host O. tsutsugamushi genotypes. The occurrence of multiple O. tsutsugamushi genotypes within individual mites has important implications, and could provide a mechanism for pathogen evolution/diversification in the mite vector.
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Affiliation(s)
- Ratree Takhampunya
- Department of Entomology, Armed Forces Research Institute of Medical Sciences-United States Army Medical Directorate, Bangkok, Thailand
| | - Achareeya Korkusol
- Department of Entomology, Armed Forces Research Institute of Medical Sciences-United States Army Medical Directorate, Bangkok, Thailand
| | - Sommai Promsathaporn
- Department of Entomology, Armed Forces Research Institute of Medical Sciences-United States Army Medical Directorate, Bangkok, Thailand
| | - Bousaraporn Tippayachai
- Department of Entomology, Armed Forces Research Institute of Medical Sciences-United States Army Medical Directorate, Bangkok, Thailand
| | - Surachai Leepitakrat
- Department of Entomology, Armed Forces Research Institute of Medical Sciences-United States Army Medical Directorate, Bangkok, Thailand
| | - Allen L. Richards
- Viral and Rickettsial Diseases Department, Naval Medical Research Center, Silver Spring, Maryland, United States of America
| | - Silas A. Davidson
- Department of Entomology, Armed Forces Research Institute of Medical Sciences-United States Army Medical Directorate, Bangkok, Thailand
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Wi YM, Woo HI, Park D, Lee KH, Kang CI, Chung DR, Peck KR, Song JH. Severe Fever with Thrombocytopenia Syndrome in Patients Suspected of Having Scrub Typhus. Emerg Infect Dis 2018; 22:1992-1995. [PMID: 27767909 PMCID: PMC5088014 DOI: 10.3201/eid2211.160597] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
To determine prevalence of severe fever with thrombocytopenia syndrome in South Korea, we examined serum samples from patients with fever and insect bite history in scrub typhus-endemic areas. During the 2013 scrub typhus season, prevalence of this syndrome among patients suspected of having scrub typhus was high (23.0%), suggesting possible co-infection.
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Kim G, Ha NY, Min CK, Kim HI, Yen NTH, Lee KH, Oh I, Kang JS, Choi MS, Kim IS, Cho NH. Diversification of Orientia tsutsugamushi genotypes by intragenic recombination and their potential expansion in endemic areas. PLoS Negl Trop Dis 2017; 11:e0005408. [PMID: 28248956 PMCID: PMC5348041 DOI: 10.1371/journal.pntd.0005408] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2016] [Revised: 03/13/2017] [Accepted: 02/13/2017] [Indexed: 12/31/2022] Open
Abstract
Background Scrub typhus is a mite-borne febrile disease caused by O. tsutsugamushi infection. Recently, emergence of scrub typhus has attracted considerable attention in several endemic countries in Asia and the western Pacific. In addition, the antigenic diversity of the intracellular pathogen has been a serious obstacle for developing effective diagnostics and vaccine. Methodology/Principal findings To understand the evolutionary pathway of genotypic diversification of O. tsutsugamushi and the environmental factors associated with the epidemiological features of scrub typhus, we analyzed sequence data, including spatiotemporal information, of the tsa56 gene encoding a major outer membrane protein responsible for antigenic variation. A total of 324 tsa56 sequences covering more than 85% of its open reading frame were analyzed and classified into 17 genotypes based on phylogenetic relationship. Extensive sequence analysis of tsa56 genes using diverse informatics tools revealed multiple intragenic recombination events, as well as a substantially higher mutation rate than other house-keeping genes. This suggests that genetic diversification occurred via frequent point mutations and subsequent genetic recombination. Interestingly, more diverse bacterial genotypes and dominant vector species prevail in Taiwan compared to other endemic regions. Furthermore, the co-presence of identical and sub-identical clones of tsa56 gene in geographically distant areas implies potential spread of O. tsutsugamushi genotypes. Conclusions/Significance Fluctuation and diversification of vector species harboring O. tsutsugamushi in local endemic areas may facilitate genetic recombination among diverse genotypes. Therefore, careful monitoring of dominant vector species, as well as the prevalence of O. tsutsugamushi genotypes may be advisable to enable proper anticipation of epidemiological changes of scrub typhus. Scrub typhus, caused by Orientia tsutsugamushi infection, is a mite-borne febrile illness endemic in the Asia-Pacific region. Recent emergence and continuous local outbreaks in many of the endemic countries make it a serious public health issue. In addition, the antigenic diversity of the tsa56 gene, encoding a major outer membrane protein, hampers the development of effective diagnostics and vaccine. Here, we extensively analyzed tsa56 sequences and their spatiotemporal information to elucidate the evolutionary pathway of genotypic diversification, as well as the environmental basis associated with the epidemiological changes of scrub typhus. Based on various informatics analyses, we found that genetic diversification of tsa56 might have been attained via frequent point mutations and subsequent genetic recombination among diverse genotypes. Prevalence of numerous bacterial genotypes and dominant vector species in Taiwan also suggest that the subtropical area located at the center of endemicity, may serve as a local mixing ground for genotype diversification. In addition, detection of identical and sub-identical clones of tsa56 genes in geographically distant countries indicates a potential spreading of bacterial genotypes. Continuous monitoring of dominant vector species and the associated O. tsutsugamushi genotypes might be required for developing better diagnostics and an effective vaccine for scrub typhus.
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Affiliation(s)
- Gwanghun Kim
- Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Na-Young Ha
- Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Chan-Ki Min
- Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Hong-Il Kim
- Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Nguyen Thi Hai Yen
- Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Keun-Hwa Lee
- Department of Microbiology and Immunology, Jeju National University School of Medicine, Jeju, Republic of Korea
| | - Inbo Oh
- Environmental Health Center, University of Ulsan College of Medicine, Ulsan, Republic of Korea
| | - Jae-Seung Kang
- Department of Microbiology, Inha University School of Medicine, Incheon, Republic of Korea
| | - Myung-Sik Choi
- Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Ik-Sang Kim
- Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Nam-Hyuk Cho
- Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Republic of Korea
- Institute of Endemic Disease, Seoul National University Medical Research Center and Bundang Hospital, Seoul, Republic of Korea
- * E-mail:
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Jang MS, Kim CM, Kim DM, Yoon NR, Han MA, Kim HK, Oh WS, Yoon HJ, Wie SH, Hur J. Comparison of Preferred Bite Sites Between Mites and Ticks on Humans in Korea. Am J Trop Med Hyg 2016; 95:1021-1025. [PMID: 27645781 DOI: 10.4269/ajtmh.16-0186] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 08/16/2016] [Indexed: 11/07/2022] Open
Abstract
Identification of mite and tick bite sites provides important clinical information. The predominant mite species in Korea associated with scrub typhus are Leptotrombidium pallidum and Leptotrombidium scutellare The most abundant tick species is Haemaphysalis longicornis To date, there has been no comparative study on preferred bite sites between mites and ticks in humans. This study included a review of medical records and a field study. For mite bite sites, eschars were checked on 506 patients with scrub typhus, confirmed by indirect immunofluorescence assay or nested polymerase chain reaction on the 56-kDa type-specific antigen gene of Orientia tsutsugamushi Tick bite sites were identified and marked on a diagram for 91 patients who experienced tick bites within the previous year through a field epidemiological investigation. The mite and tick bite sites in Koreans were compared. The most frequently observed mite bite sites were the anterior chest, including the axillae (29.1%) and the abdominal region, including the inguinal area (26.1%). Tick bite sites were most frequent on the lower extremities (33.0%), followed by the abdominal region, including the inguinal area (26.4%), and upper extremities (26.4%). The distribution was significantly different between mite and tick bite sites (P < 0.001). There was a statistically significant difference in the mite bite (P = 0.001), but not tick bite sites (P = 0.985), between men and women. This is the first report on the differences between tick and mite bite sites, and may help clinicians reach a rapid diagnosis of mite- or tick-borne infection.
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Affiliation(s)
- Mi-Sun Jang
- Department of Internal Medicine, College of Medicine, Chosun University, Gwangju, South Korea
| | - Choon-Mee Kim
- Premedical Science, College of Medicine, Chosun University, Gwangju, South Korea
| | - Dong-Min Kim
- Department of Internal Medicine, College of Medicine, Chosun University, Gwangju, South Korea.
| | - Na Ra Yoon
- Department of Internal Medicine, College of Medicine, Chosun University, Gwangju, South Korea
| | - Mi Ah Han
- Department of Preventive Medicine, College of Medicine, Chosun University, Gwangju, South Korea
| | - Hyun-Kuk Kim
- Department of Pulmonary and Critical Care Medicine, Haeundae Paik Hospital, Inje University College of Medicine, Busan, Korea
| | - Won Sup Oh
- Department of Internal Medicine, Kangwon National University School of Medicine, Chuncheon, Korea
| | - Hee-Jung Yoon
- Department of Infectious Diseases, Seoul Metropolitan Government Seobuk Hospital, Seoul, Korea
| | - Seong-Heon Wie
- Department of Internal Medicine, St. Vincent's Hospital, School of Medicine, The Catholic University of Korea, Seoul, South Korea
| | - Jian Hur
- Department of Internal Medicine, Yeungnam University, College of Medicine, Daegu, South Korea
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Abstract
The obligate intracellular bacterium Orientia tsutsugamushi is responsible for more than one million cases of scrub typhus annually throughout the Asia-Pacific region. Human infection occurs via the bite of the larval form (chigger) of several species of trombiculid mites. While in some patients the result of infection is a mild, febrile illness, others experience severe complications, which may even be fatal. This review discusses the genome and biology of the causative agent, the changing epidemiology of scrub typhus, the challenges of its diagnosis, and current treatment recommendations.
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Affiliation(s)
- Sunil Thomas
- Lankenau Institute for Medical Research, Wynnewood, Pennsylvania USA
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23
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Species diversity of ectoparasitic chigger mites (Acari: Prostigmata) on small mammals in Yunnan Province, China. Parasitol Res 2016; 115:3605-18. [PMID: 27212464 DOI: 10.1007/s00436-016-5127-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Accepted: 05/12/2016] [Indexed: 10/21/2022]
Abstract
Chigger mites are a large group of arthropods and the larvae of mites are ectoparasites. Some species of ectoparasitic mites (larvae) can be the transmitting vectors of tsutsugamushi disease (scrub typhus). Yunnan Province is located in the southwest of China with complicated topographic landform and high biodiversity, where there are five zoogeographical subregions. Rodents and some other small mammals were trapped and examined for ectoparasitic chigger mites in 29 investigation sites in Yunnan during 2001-2013. From 13,760 individuals and 76 species of small mammal hosts, we collected 274 species of mites, which were identified as comprising 26 genera in two families. The species diversity of chigger mites (274 species) in the present study were not only much higher than that from other provinces of China but also largely exceeded that recorded from other regions and countries in the world. Of the five zoogeographical subregions, both the species diversity and Shannon-Weiner's diversity of mites were the highest in subregion II (southern subregion of Hengduan Mountains) with middle altitudes and middle latitude. Both the species diversity of mites and Shannon-Wiener diversity index showed a parabolic tendency from the low altitude (<500 m) to the high altitude (>3500 m) along the vertical gradients with the peak occurring in the middle-altitude regions (2000-2500 m). Of four dominant hosts, the species richness of mites was highest on Eothenomys miletus (S = 165) and Shannon-Wiener diversity index was highest on Rattus norvegicus (H = 3.13). Along latitude gradients, species richness of chigger mites increased first and then decreased, peaking at 25° to 26° N with 193 mite species. The geographical location, complex topography, and landscape with diverse small mammal hosts in Yunnan Province have contributed to the extremely high species diversity of mites in the province. The large sampling size of small mammal hosts in a wide geographical scope within a long time span also made it possible to have collected so many species of chigger mites.
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Kuo CC, Lee PL, Chen CH, Wang HC. Surveillance of potential hosts and vectors of scrub typhus in Taiwan. Parasit Vectors 2015; 8:611. [PMID: 26626287 PMCID: PMC4666075 DOI: 10.1186/s13071-015-1221-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Accepted: 11/21/2015] [Indexed: 03/11/2023] Open
Abstract
Background Scrub typhus is a lethal infectious disease vectored by larval trombiculid mites (i.e. chiggers) infected with Orientia tsutsugamushi (OT) and recent decades have witnessed an emergence of scrub typhus in several countries. Identification of chigger species and their vertebrate hosts is fundamental for the assessment of human risks to scrub typhus under environmental changes, but intensive and extensive survey of chiggers and their hosts is still lacking in Taiwan. Methods Chiggers were collected from shrews and rodents in nine counties of Taiwan and were assayed for OT infections with nested polymerase chain reaction (PCR). PCR products were further sequenced to reveal probable OT strains. Rodents were assessed for OT exposure by immunofluorescent antibody assay. Lastly, incidence rate of scrub typhus in each county was associated with loads and prevalence of chigger infestations, seropositivity rate in rodents, and OT positivity rate in chiggers. Results Rattus losea was the most abundant (48.7 % of 1,285 individuals) and widespread (occurred in nine counties) small mammal species and hosted the majority of chiggers (76.4 % of 128,520 chiggers). Leptotrombidium deliense was the most common (64.9 % of all identified chiggers) and widespread (occurred in seven counties) chigger species but was replaced by Leptotrombidium pallidum or Leptotrombidium scutellare during the cold seasons in two counties (Matsu and Kinmen) where winter temperatures were lower than other study sites. Seropositivity rate for OT exposure in 876 assayed rodents was 43.0 % and OT positivity rate in 347 pools of chiggers was 55.9 %, with 15 OT strains identified in the 107 successfully sequenced samples. Incidence rate of scrub typhus was positively correlated with chigger loads, prevalence of chigger infestations, seropositivity rate but not OT positivity rate in chiggers. Conclusions Our study reveals R. losea as the primary host for chiggers and there exists a geographical and seasonal variation in chigger species in Taiwan. It also emphasizes the importance of recognition of chigger vectors and their vertebrate hosts for a better prediction of human risks to scrub typhus under rapid environmental changes.
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Affiliation(s)
- Chi-Chien Kuo
- Department of Life Science, National Taiwan Normal University, Taipei, Taiwan.
| | - Pei-Lung Lee
- Center for Research, Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taipei, No. 161, Kun-Yang Street, Taipei, 11561, Taiwan.
| | - Chun-Hsung Chen
- Center for Research, Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taipei, No. 161, Kun-Yang Street, Taipei, 11561, Taiwan.
| | - Hsi-Chieh Wang
- Center for Research, Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taipei, No. 161, Kun-Yang Street, Taipei, 11561, Taiwan.
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Jeung YS, Kim CM, Yun NR, Kim SW, Han MA, Kim DM. Effect of Latitude and Seasonal Variation on Scrub Typhus, South Korea, 2001-2013. Am J Trop Med Hyg 2015; 94:22-5. [PMID: 26503283 DOI: 10.4269/ajtmh.15-0474] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2015] [Accepted: 08/20/2015] [Indexed: 11/07/2022] Open
Abstract
In South Korea, scrub typhus is one of the most common rickettsial diseases. The number of scrub typhus patients has increased in South Korea, a total of 69,210 cases were reported from 2001 to 2013. The seasonality and relation of scrub typhus cases to latitude were analyzed in this article using data obtained from the National Notifiable Diseases Surveillance System website of the Korea Centers for Disease Control and Prevention. The incidence of scrub typhus tended to increase in the later months of the year, especially in October-December. In general, lower latitudes were associated with a later peak incidence. Our results suggest for the first time that the monthly observed incidence tended to increase in the later months of the year as the latitude decreased, and on a yearly basis in Korea.
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Affiliation(s)
- Ye Sul Jeung
- School of Medicine, Chosun University, Gwangju, South Korea; Premedical Science, College of Medicine, Chosun University, Gwangju, South Korea; Department of Internal Medicine, School of Medicine, Chosun University, Gwangju, South Korea; Department of Neurosurgery, School of Medicine, Chosun University, Gwangju, South Korea; Department of Preventive Medicine, School of Medicine, Chosun University, Gwangju, South Korea
| | - Choon-Mee Kim
- School of Medicine, Chosun University, Gwangju, South Korea; Premedical Science, College of Medicine, Chosun University, Gwangju, South Korea; Department of Internal Medicine, School of Medicine, Chosun University, Gwangju, South Korea; Department of Neurosurgery, School of Medicine, Chosun University, Gwangju, South Korea; Department of Preventive Medicine, School of Medicine, Chosun University, Gwangju, South Korea
| | - Na Ra Yun
- School of Medicine, Chosun University, Gwangju, South Korea; Premedical Science, College of Medicine, Chosun University, Gwangju, South Korea; Department of Internal Medicine, School of Medicine, Chosun University, Gwangju, South Korea; Department of Neurosurgery, School of Medicine, Chosun University, Gwangju, South Korea; Department of Preventive Medicine, School of Medicine, Chosun University, Gwangju, South Korea
| | - Seok-Won Kim
- School of Medicine, Chosun University, Gwangju, South Korea; Premedical Science, College of Medicine, Chosun University, Gwangju, South Korea; Department of Internal Medicine, School of Medicine, Chosun University, Gwangju, South Korea; Department of Neurosurgery, School of Medicine, Chosun University, Gwangju, South Korea; Department of Preventive Medicine, School of Medicine, Chosun University, Gwangju, South Korea
| | - Mi Ah Han
- School of Medicine, Chosun University, Gwangju, South Korea; Premedical Science, College of Medicine, Chosun University, Gwangju, South Korea; Department of Internal Medicine, School of Medicine, Chosun University, Gwangju, South Korea; Department of Neurosurgery, School of Medicine, Chosun University, Gwangju, South Korea; Department of Preventive Medicine, School of Medicine, Chosun University, Gwangju, South Korea
| | - Dong-Min Kim
- School of Medicine, Chosun University, Gwangju, South Korea; Premedical Science, College of Medicine, Chosun University, Gwangju, South Korea; Department of Internal Medicine, School of Medicine, Chosun University, Gwangju, South Korea; Department of Neurosurgery, School of Medicine, Chosun University, Gwangju, South Korea; Department of Preventive Medicine, School of Medicine, Chosun University, Gwangju, South Korea
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26
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Lee HW, Cho PY, Moon SU, Na BK, Kang YJ, Sohn Y, Youn SK, Hong Y, Kim TS. Current situation of scrub typhus in South Korea from 2001-2013. Parasit Vectors 2015; 8:238. [PMID: 25928653 PMCID: PMC4416255 DOI: 10.1186/s13071-015-0858-6] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 04/13/2015] [Indexed: 11/20/2022] Open
Abstract
Background The bacteria Orientia tsutsugamushi is the causative agent of scrub typhus, mite-borne disease, which causes an acute febrile illness in patients. An epidemiologic study was conducted to understand the characteristics of scrub typhus in South Korea. Findings Reporting of tsutsugamushi disease is mandatory in South Korea since 1994. To investigate the prevalence of tsutsugamushi disease from 2001 to 2013, medical records from the Korea Center for Disease Control and Prevention were reviewed. In total, 70,914 cases were reported during 2001–2013. Of these, 37.16% (26,349) were male and 62.84% (44,565) were female. The highest number of cases was in the 60–69-year-old age group (19,484; 27.48%), and 72.22% (51,212) were in the 50–79-year-old age group. There were 65,100 cases (91.80%) reported during October (24,964; 35.20%) and November (40,136; 56.60%). An almost four-fold increase in the number of patients was observed in 2013 (10,485 cases) compared to 2001 (2,637 cases). The highest number of patients was reported in the Jeonbuk (9,425; 13.29%) and lowest in the Jeju (362; 0.51%). Conclusions A rapid increase in the incidence of patients with tsutsugamushi disease was observed in most areas from 2001 to 2013, with the majority of cases reported in the western and southern coast.
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Affiliation(s)
- Hyeong-Woo Lee
- Department of Pathology, Immunology, and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL, 32610, USA.
| | - Pyo Yun Cho
- Departments of Parasitology and Tropical Medicine, Inha University School of Medicine, Incheon, 400-712, Republic of Korea.
| | - Sung-Ung Moon
- Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, 463-939, Korea.
| | - Byoung-Kuk Na
- Department of Parasitology and Institute of Health Sciences, Gyeongsang National University School of Medicine, Jinju, 660-751, Korea.
| | - Yoon-Joong Kang
- Department of Biomedical Science, Jungwon University, Goesan, Chungbuk, 367-805, Republic of Korea.
| | - Youngjoo Sohn
- Department of Anatomy, College of Korean Medicine, Institute of Korean Medicine, Kyung Hee University, Seoul, 130-701, Korea.
| | - Seung-Ki Youn
- Department of Epidemiology, National Institute of Health, Osong, 363-951, Republic of Korea.
| | - Yeongseon Hong
- Department of Public Health, Sahmyook University, Seoul, 139-742, Republic of Korea.
| | - Tong-Soo Kim
- Departments of Parasitology and Tropical Medicine, Inha University School of Medicine, Incheon, 400-712, Republic of Korea.
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