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.

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.

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

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.

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.

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.

Investigation of Chigger Mites on the Rat Eothenomys miletus in Yunnan / 中国寄生虫学与寄生虫病杂志

Objective To understand the species,species distribution,the dominant species and their interspecies interaction of chigger mites on Eothenomys miletus(a dominant species of rats)in Yunnan.Method The rats were captured with mouse traps in 16 counties(or cities)during 2000-2004.All mites on the surface of two auricles of the hosts were collected and identified.The patch index(m*/m)and the coefficient of association(V)were adopted to judge the spatial distribution patterns and interspecies interaction of the dominant chigger mite species among different individuals of the rats(E.miletus).Results 1157 individuals of E.miletus were captured from 16 counties(citys).37613 chigger mites(belonging to 3 subfamily,9 genus and 80 species)were collected from the auricles(body surface)of 1157 rat hosts with a high “overall mite infestation rate”(68.2%)and “overall mite index”(32.5).Six species of mites were found dominant on E.miletus:Leptotrombidium scutellare,Leptotrombidium sinicum,Helenicula simena,Leptotrombidium eothenomydis,Herpetacarus hastoclavus and Leptotrombidium hiemalis.The distribution of the chigger mites among different individuals of E.miletus showed an aggregation pattern.Both positive and negative association existed between each two dominant species of chigger mites.Conclusion The species composition of chigger mites on Eothenomys miletus is complex with abundant individuals,which reflects a high species diversity of the mites.The main species of chigger mites tend to an aggregation on the body surface of E.miletus.