Research progress on the epidemiology of tsutsugamushi disease of summer type in China / 预防医学

@#Tsutsugamushi disease, also known as scrub typhus, is a zoonosis caused by Orientia tsutsugamushi, with rats as the main sources of infection and chigger mites as the only medium of transmission, and has no effective vaccines. Tsutsugamushi disease can be divided into summer, autumn and winter types according to seasons in China, while the summer type is characterized by strong virulence, typical and severe symptoms, high rates of misdiagnosis and mortality. The summer type of tsutsugamushi disease is distributed in the south of 31°N in China, with the epidemic time from June to August, and the cases are predominantly females, farmers and people at ages of over 40 years. Affected by natural environment, social and economic factors, the epidemic areas and the number of cases of summer type of tsutsugamushi disease are increasing continuously. Based on publications pertaining to the epidemiology of summer type of tsutsugamushi disease in China from 1960 to 2023, this review summarizes the mechanism of transmission, epidemiological characteristics and influencing factors, so as to provide the basis for prevention and control of summer type of tsutsugamushi disease in China.

Population and chigger mite infection of rodents in Pudong New Area， Shanghai / 上海预防医学

ObjectiveTo investigate the population and chigger mite infection of rodents in Pudong District， Shanghai， so as to provide the scientific basis for the prevention and control of rodents and chigger transmitted diseases. MethodsThe monitoring work was conducted in four points including Xuanqiao， Hangtou， Laogang and Nanhui New Town with night trapping method from 2020 to 2022. Habitats as farmland， wasteland， rural residential areas， and parks were selected. The rodent species were identified and rodent density was calculated. All chigger mites were collected from the earlaps and auricular fossae of the rodents. The species of chigger mites were identified and the chigger mite index was calculated. ResultsA total of 222 rodents were captured. They belonged to 5 species， 4 genera， 2 families and 2 orders， including 4 species， 3 genera， and 1 family of Rodentia and 1 species of Insectivora. M. musculus was the dominant species， with a composition ratio of 54.05%. Total 80 chigger mites were captured， with a detection rate of 36.03%. The total chigger index was 0.36 and Rattus tanezumi held the highest （6.00）， followed by M. musculus （0.48）. There were 3 species of chigger mites， L.deliense， L.scutellare， and L.gaohuense. L.deliense was the dominant specie， accounting for 55.00%. ConclusionThere is a risk of chigger-borne disease transmission in Pudong New Area with M. musculus as the dominant host and L. deliense as the dominant species.

Fauna of scrub typhus vector chigger mites in Yunnan Province / 中国热带医学

@#Abstract: Chigger mites belong to the phylum Arthropoda, class Arachnida, sub-class Acari, order Parasitiformes, family Trombiculidae and Leeuwenhoekiidae, with a wide range of species. There are more than 3 700 known species of mites globally, of which 531 species in 46 genera from three sub-families have been recorded in China, and 320 species of chigger mites recorded from 3 subfamilies and 32 genera in Yunnan Province. At this stage, chigger mites are the only vectors of scrub typhus, with about 60 species worldwide being potential vectors. Six vectorial mite species have been confirmed in China, including Leptotrombidium deliense, L.scutellare, L.rubellum, L.sialkotense, L.kaohuense, L.insulare. Yunnan Province has reported five vectorial mite species, including the previously-mentioned five species except for L.sialkotense. The zoogeographic study divided Yunnan Province into 5 zoogeographic areas, namely, Central Hengduan Mountains subregion, Southern Hengduan Mountains subregion, Eastern Yunnan Plateau subregion, Western Yunnan Plateau subregion, Southern Yunnan Mountainous subregion. The Southern Hengduan Mountains subregion has the highest number of known genera and species of scrub typhus and the highest number of scrub typhus cases, with 216 species in 22 genera from 3 subfamilies, and all 5 species of vector scrub typhus were distributed. Southern Yunnan Mountain subregion has the least number of mite species, with 91 species in 12 genera from three sub-families, with L. scutellare being the dominant vectorial mite species across the province. Due to suitable natural geographic conditions in Yunnan Province, vectorial mites can propagate rapidly, leading to a large number of scrub typhus cases. According to statistics, the number of scrub typhus cases in Yunnan Province has rapidly increased, with 15.40 times, 20.64 times and 28.91 times more cases in 2016, 2017 and 2018 respectively than in 2006. Scrub typhus remains a serious public health problem in Yunnan Province, posing a threat to the health of the local population. Therefore, prevention and control efforts should continue to focus on the affected areas and the general public.

An atypical presentation of scrub typhus

Scrub typhus is caused byOrientia tsutsugamushi, characterised by focal or disseminated vasculitis and perivasculitis which may involve the lungs, heart, liver, spleen and central nervous system.The clinical picture and severity of the symptoms varies widely. The neurological manifestations of scrub typhus are diverse. Meningoencephalitis is classical manifestation of scrub typhus but cerebellitis, cranial nerve palsies, plexopathy, transverse myelitis, neuroleptic malignant syndrome and Guillain-Barre syndrome are other manifestations reported in literature. The availability of literature on the neurological manifestations of scrub typhusis limited to case reports mainly. This article shows a case report of neurological manifestations of scrub typhus.

Vector and rodent surveillance for Orientia tsutsugamushi in north India

Background & objectives: Scrub typhus or chigger borne typhus, caused by Orientia tsutsugamushi is an emerging vector-borne disease as large numbers of cases have been reported in various tropical countries. It is transmitted to humans through bites of infected chiggers (larval mites). The knowledge about the vector, its distribution, density and habitat are important so as to understand the epidemiology of scrub typhus in a given area. To control rickettsial infections, regular rodent-vector surveillance should be planned in areas where the disease transmission is occurring and it will also help to strengthen the existing entomological data related to the vector of scrub typhus in northern India. Methods: In the present study, rodent-vector surveillance was planned for one whole year, covering both mite active and non-active seasons (October 2019–December 2020) in selected areas of Chandigarh and Punjab in north India. Rodent tissues and mites were also examined for the presence of O. tsutsugamushi by nested PCR for 56 kDa gene and real-time PCR for 47 kDa outer membrane protein gene. 18S gene PCR was performed for molecular identification of mites. Results: In the surveillance, three types of ectoparasite, viz. mites, fleas and ticks were obtained in rodents. All mites found were of Laelapidae family. None of the pooled rodent tissue samples as well as mite samples were found positive for O. tsutsugamushi by nested PCR for rickettsial DNA. Interpretation & conclusion: In the present study, we did not get any evidence of carriage of O. tsutsugamushi in either mites or rodents collected and sampled in selected regions in Chandigarh and Punjab. We need to strengthen the entomological surveillance over a broader region and increase the frequency of trapping rodents to increase clarity on vector-reservoir dynamics in this geographical region.

Emerging trends of scrub typhus disease in southern Rajasthan, India: A neglected public health problem

Scrub typhus is the oldest known vector-borne zoonotic infectious disease in the world which is life-threatening for all age groups as it presents acute febrile illness along with multi-organ involvements and spread with the biting of infectious ‘Trombiculid mite’ (chigger mite). The pathogen of this disease is an obligatory coccobacillus gram-negative rickettsial bacteria Orientia tsutsugamushi. Scrub typhus disease was previously confined geographically only to the Asia Pacific region (tsutsugamushi triangle), but in recent years it has crossed its limit and has spread in other countries beyond the tsutsugamushi triangle and has become more hazardous for the community. The objective of this study is to explore the scrub typhus disease outbreak trends with existing information in southern Rajasthan state, India. This study concluded that scrub typhus disease is being re-emerged again and again in various Indian geographical regions with new species of vectors. The disease has been raised in tremendous amounts in Rajasthan within the last five years especially in the hilly zone and has led to major public health problems with other zoonotic diseases

Investigation of chigger mites on small mammals in Ruili, Yunnan Province, China

@#Chigger mites are arthropods and are the sole vectors of scrub typhus, and rodents as well as other small mammals are the most common hosts of chigger mite larvae. Therefore, it is of great medical significance to study the ecology of chigger mites. In this study, a detailed analysis of chigger mites was conducted based on field survey data. A total of 4,941 chigger mites were collected from 86 hosts at 34 survey sites in Ruili, Yunnan Province, China. Among the 4,941 chiggers, five genera in one subfamily were identified; Schoengastiella ligula was the dominant chigger species with the highest infestation index, prevalence (Pm, 42.86%) and mean intensity (MI, 59.09%) (P<0.001). The association coefficient (V) between S. ligula and Gahrliepia radiopunctata was positively correlated (P<0.05), indicating the tendency of chiggers to select and coexist on the same host at the same time. The dominant species Leptotrombidium kunmingense, Ascoschoengastia indica, S. ligula and G. radiopunctata showed aggregation distribution patterns, indicating that the distribution of chiggers among different hosts was not uniform. Low altitudes and low latitudes appeared to be more favorable for the growth and reproduction of chigger mites (P<0.05). It is suggested to collect as many host samples as possible in future field investigations to better understand the dynamics of chigger mite populations and their primary hosts.

First record of Blankaartia sinnamaryi (Floch & Fauran, 1956) (Trombidiformes: Trombiculidae) parasitizing the striped owl in Northeastern Brazil / Primeiro registro de Blankaartia sinnamaryi (Floch & Fauran, 1956) (Trombidiformes: Trombiculidae) parasitando uma coruja-listrada no Nordeste do Brasil

Abstract The chigger species Blankaartia sinnamaryi (Floch & Fauran) has been collected mainly from birds with a few records from reptiles and mammals. In Brazil, this species has been found on birds in the Minas Gerais and Rio de Janeiro states. Here, we report the first record of B. sinnamaryi parasitizing the striped owl, Pseudoscops clamator (Vieillot), in the Paraíba state, Brazil (northeastern region).

Resumo A espécie de trombiculídeo, Blankaartia sinnamaryi (Floch & Fauran) tem sido coletada principalmente parasitando aves, com alguns registros em répteis e mamíferos. No Brasil, essa espécie foi encontrada em aves nos estados de Minas Gerais e Rio de Janeiro. No presente estudo, relatamos o primeiro registro de B. sinnamaryi parasitando a coruja-listrada, Pseudoscops clamator (Vieillot), no estado da Paraíba, Brasil (região Nordeste).

Infestation and distribution of chigger mites on Brown rat (Rattus norvegicus) in Yunnan Province, Southwest China

@#Chigger mites is a group of arthropods and some of them are vectors of scrub typhus. As a common synanthropic rodent species, the Brown rat (Rattus norvegicus) often harbors lots of ectoparasites including chigger mites. According to some “data mining” strategies, the present study took the advantage of the abundant original data from a long-term field ecological investigation between 2001 and 2015 to make a detailed analysis of chigger mites on R. norvegicus in Yunnan Province, Southwest of China. From 18 of 33 investigated counties, only 1414 chigger mites were collected from 1113 Brown rats with relatively low infestations. The 1414 individual chigger mites were identified as comprising 61 species, 11 genera and 2 subfamilies of the family Trombiculidae with a high species diversity (S=61, H’=3.13). Of 61 mite species, there were four main species, Walchia ewingi, Ascoschoengastia indica, W. koi and A. rattinorvegici, which accounted for 44.41% of the total mites. All the chigger mites were of aggregated distribution among different individuals of R. norvegicus. The Brown rats in the outdoor habitats harbored much more individuals and species of chigger mites with a higher mean abundance (MA=1.46) and mean intensity (MI=12.53) than in the indoor habitats (P<0.05). The overall infestation of the rats was significantly higher in the mountainous landscapes than in the flatland landscapes (P<0.001). The species similarity (Css) of the mites on the male and female rats reached 64.44% with sex biased infestations. The male rats harbored more species and individuals of the mites than the female rats. The adult rats harbored more species and individuals of the mites than the juvenile rats. The species abundance distribution of the mites was successfully fitted by Preston’s lognormal model with S

Research Progress on Leptotrombidium deliense

This article reviews Leptotrombidium deliense, including its discovery and nomenclature, morphological features and identification, life cycle, ecology, relationship with diseases, chromosomes and artificial cultivation. The first record of L. deliense was early in 1922 by Walch. Under the genus Leptotrombidium, there are many sibling species similar to L. deliense, which makes it difficult to differentiate L. deliense from another sibling chigger mites, for example, L. rubellum. The life cycle of the mite (L. deliense) includes 7 stages: egg, deutovum (or prelarva), larva, nymphochrysalis, nymph, imagochrysalis and adult. The mite has a wide geographical distribution with low host specificity, and it often appears in different regions and habitats and on many species of hosts. As a vector species of chigger mite, L. deliense is of great importance in transmitting scrub typhus (tsutsugamushi disease) in many parts of the world, especially in tropical regions of Southeast Asia. The seasonal fluctuation of the mite population varies in different geographical regions. The mite has been successfully cultured in the laboratory, facilitating research on its chromosomes, biochemistry and molecular biology.

Chigger Mite (Acari: Trombiculidae) Survey of Rodents in Shandong Province, Northern China

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°E, 34–38°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.

Seroepidemiological Survey of Zoonotic Diseases in Small Mammals with PCR Detection of Orientia tsutsugamushi in Chiggers, Gwangju, Korea

Serosurveillance for zoonotic diseases in small mammals and detection of chiggers, the vector of Orientia tsutsugamushi, were conducted from September 2014 to August 2015 in Gwangju Metropolitan Area. Apodemus agrarius was the most commonly collected small mammals (158; 91.8%), followed by Myodes regulus (8; 4.6%), and Crocidura lasiura (6; 3.5%). The highest seroprevalence of small mammals for O. tsutsugamushi (41; 26.3%) was followed by hantaviruses (24; 15.4%), Rickettsia spp. (22; 14.1%), and Leptospira (2; 1.3%). A total of 3,194 chiggers were collected from small mammals, and 1,236 of 3,194 chiggers were identified with 7 species of 3 genera: Leptotrombidium scutellare was the most commonly collected species (585; 47.3%), followed by L. orientale (422; 34.1%), Euchoengastia koreaensis (99; 8.0%), L. palpale (58; 4.7%), L. pallidum (36; 2.9%), Neotrombicula gardellai (28; 2.3%), and L. zetum (8; 0.6%). L. scutellare was the predominant species. Three of 1,236 chigger mites were positive for O. tsutsugamushi by PCR. As a result of phylogenetic analysis, the O. tsutsugamushi strain of chigger mites had sequence homology of 90.1-98.2% with Boryong. This study provides baseline data on the distribution of zoonotic diseases and potential vectors for the development of prevention strategies of vector borne diseases in Gwangju metropolitan area.

Epidemic of Scrub Typhus in Haroti Region of Rajasthan.

Scrub typhus is a rare form of disease caused by gram negative bacterium Orientia tsutsugamushi, of family Rickettsiaceae, transmitted by bite of infected trombiculid mite larva (chigger). The present prospective study is undertaken with the aim of the clinical manifestations, course, complications and outcome of scrub typhus in Haroti region of Rajasthan state during the recent epidemic. Method: This prospective study was conducted in indoor patients of MBS hospital and various private nursing homes in Kota city from August 2012 to November 2012. Twenty cases with positive Scrub typhus card test in the age group of 20 years to 60 years, comprising of 14 males and 06 females were included in the study group in clinically suspected cases with fever, rashes, cough with or without eschar and regional lymphadenopathy. Cases were studied in detail and followed up for improvement and any permanent damage or death. Results: Out of 20 patients, 16 patients improved and discharged from hospital in stable condition without any disability. 02 patients (10%) died because of late presentation and multiorgan involvement especially respiratory failure or meningoencephalitis. Conclusion: Haroti witnessed recent epidemic of Scrub typhus. Renal, respiratory and neurological complications were main cause of mortality and morbidity.

A New Species of Chigger Mite (Acari: Trombiculidae) from Rodents in Southwest China

This paper describes a new species of chigger mite (Acari: Trombiculidae), Gahrliepia cangshanensis n. sp., from rodents in southwest China. The specimens were collected from Yunnan red-backed voles, Eothenomys miletus (Thomas, 1914), and a Chinese white-bellied rat, Niviventer confucianus (Milne-Edwards, 1871) in Yunnan Province. The new species is unique mainly in its number of dorsal setae (n=21), and it has the following features: fT (formula of palpotarsus)=4B (B=branched), fp (formula of palpal seta)=B/N/N/N/B (N=naked), a broad tongue-shaped scutum with an almost straight posterior margin, and 17 PPLs (posterior posterolateral seta) with a length of 36-43 microm. This chigger mite may also infect other rodent hosts and may be distributed in other localities.

Larval Chigger Mites Collected from Small Mammals in 3 Provinces, Korea

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.

Ectoparasite occurrence associated with males and females of wild rodents Oligoryzomys flavescens (Waterhouse) and Akodon azarae (Fischer) (Rodentia: Cricetidae: Sigmodontinae) in the Punta Lara wetlands, Argentina

The objective of this research was to study infestation parameters and indexes of ectoparasites associated with each sex of the wild rodents Oligoryzomys flavescens (Waterhouse) andAkodon azarae (Fischer) in the Punta Lara wetlands, Argentina. A trend towards higher mean abundance (MA) and ectoparasite specific richness was observed in males of O. flavescens whereas those values were similar for both A. azarae sexes. The prevalence of the following ectoparasites was significantly higher on males (P < 0.05): Mysolaelaps microspinosus Fonseca (65.2 percent) and Hoplopleura travassosi Werneck (73.9 percent) on O. flavescens, and Ixodes loricatus Neumann (71.4 percent) on A. azarae. Only H. travassosi mean abundance was significantly higher on males (MA = 44.1). Since I. loricatus and Hoplopleura spp. are involved in the transmission of pathogens that cause diseases in animals and humans, and whose reservoirs are rodent hosts, these results are epidemiologically important.

Serosurveillance of Scrub Typhus in Small Mammals Collected from Military Training Sites near the DMZ, Northern Gyeonggi-do, Korea, and Analysis of the Relative Abundance of Chiggers from Mammals Examined

Comprehensive quarterly serosurveillance on scrub typhus in small mammals collected from military training sites located near the Demilitarized Zone (DMZ), northern Gyeonggi-do (Province), ROK was conducted to determine the potential rodent-borne and associated ectoparasite disease risks to military personnel. A total of 1,196 rodents and insectivores representing 8 species, Apodemus agrarius (87.3%, n = 1,044), Mus musculus (5.4%, n = 65), Crocidura lasiura (3.3%, n = 40), Microtus fortis (2.6%, n = 31), Micromys minutus (0.3%, n = 4), Tscherskia triton (0.3%, n = 4), Rattus norvegicus (0.3%, n = 4), and Myodes regulus (0.3%, n = 4) were assayed for the presence of antibodies to Orientia tsutsugamushi. O. tsutsugamushi antibodies were detected in 6 of 8 species and seroprevalence determined; A. agrarius (45.6%), M. musculus (23.1%), M. fortis (48.4%), M. minutus (50.0%), T. triton (50.0%), and R. norvegicus (25.0%). A total of 31,184 chigger mites collected from 508 rodents and insectivores were slide-mounted and 10 species belonging to 4 genera were identified. Leptotrombidium pallidum (53.4%) was the most frequently collected, followed by L. palpale (15.7%), Neotrombicula tamiyai (14.3%), L. orientale (10.7%), L. zetum (3.1%), Walchia fragilis (2.1%), and L. gemiticulum (0.8%), while the remaining 3 species, L. subintermedium, N. gardellai, and Euschoengastia koreaensis were rarely observed (prevalence < 10%). In contrast to previous surveys, higher chigger indices of the primary scrub typhus vectors, L. pallidum (165.4), L. orientale (45.0), and L. palpale (21.4), were observed during the spring season.

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

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

STUDY ON DETECTION OF HEMORRHAGIC FEVER WITH RENAL SYDNROME VIRUS GENE BY DIG LABELED PROBE / 中国人兽共患病学报

Dig-DNA probes of hemorrhagic fever with renal syndrome vinus M S gene fragment were prepared by PCR and random primer labeling, The probes had speciality to HFRSV-RNA and could detect 10pg RNA by RNA-DNA dot-blot hybridization. The results of hybridization showed that positive reactions were found in 5, 10 chigger mites groups from antigenic positive rats, 10 mites group from antigenic negative rats, 10, 50 free chigger mites, and hung of antigenic positive mice 100mg, 500mg. But negative reation in 5 mites group from antigenic negative mice.

Study of Chigger Communities on Major Species of Rodents in Yunnan Province / 中国寄生虫学与寄生虫病杂志

Leptotrombidium eothenomydis.There was a wide niche overlap between any two chigger species with all indices beyond 0.76.Slight positive association existed between each two dominant species of chigger mites by the coefficient of association(V).Conclusion The community structure of chigger mites on the 7 major species of rodent hosts is complex,reflecting a high diversity of mite species.The niche breadth of the 6 dominant chigger species is different with a wide niche overlap.