Species diversity and related ecology of chiggers on small mammals in a unique geographical area of Yunnan Province, southwest China.

Chiggers are common ectoparasites and the exclusive vector of scrub typhus. Based on previous investigations from a unique geographical area in Yunnan Province of southwest China, the Three Parallel Rivers Area, we retrospectively studied the species diversity and related ecology of chiggers on rodents and other small mammals. A very high species diversity of 120 chigger species was identified. Five dominant chigger species accounted for 59.4% (5238/8965) of total chiggers, and among them Leptotrombidium scutellare is the second major vector of scrub typhus in China. Species diversity of the chigger community fluctuates greatly in different altitudinal and latitudinal gradients. There are significant differences in species composition, species diversity and dominant species of chiggers among hosts with apparent community heterogeneity. Based on the species abundance distribution, the expected total number of chigger species was estimated to be 170, 50 more than the number of actually collected species; this further indicates a very high chigger species diversity in this area. The bipartite ecological network analysis revealed the intricate relationships between chigger and host species-positive and negative correlations existed among some species of dominant and vector chiggers.

Infestation and distribution of chiggers on the Anderson's white-bellied rats in southwest China.

As a group of ectoparasites, chiggers (larvae of chigger mites) are the exclusive vector of scrub typhus (tsutsugamushi disease). Rodents are the most important hosts of chiggers. The Anderson's niviventer rat, Niviventer andersoni, is an endemic species of rodent in China. However, few studies have involved this endemic rodent species and its ectoparasites including chiggers. According to the field investigation in five provincial regions of southwest China between 2001 and 2019, this paper retrospectively analysed the infestation and distribution of chiggers on the body surface of N. andersoni in southwest China for the first time. From 77 Anderson's niviventer rats captured, a total of 527 chiggers were collected and they were identified as 39 species and nine genera in two subfamilies of family Trombiculidae. Of 39 chigger species identified, Leptotrombidium deliense and L. scutellare are the most important vectors of scrub typhus in China. The overall infestation indexes were PM = 29.87%, MA = 6.84 and MI = 22.91, and the indexes of chigger mite community were Mf = 39, H' = 2.60, E = 0.71 and D = 0.12. The dominant chigger species are L. wenense, L. xiaguanense and L. fujianense with a total Cr = 51.04%, among which L. wenense is one of the six main vectors of scrub typhus in China. The dominant chigger species are of aggregated distribution among different individuals of the rats.

Detection of Orientia spp. Bacteria in Field-Collected Free-Living Eutrombicula Chigger Mites, United States.

Scrub typhus, a rickettsial disease caused by Orientia spp., is transmitted by infected larval trombiculid mites (chiggers). We report the molecular detection of Orientia species in free-living Eutrombicula chiggers collected in an area in North Carolina, USA, to which spotted fever group rickettsiae infections are endemic.

Comparison of Chiggers (Acari: Trombiculidae, Leeuwenhoekiidae) on Two Sibling Mouse Species, Apodemus draco and A. ilex (Rodentia: Muridae), in Southwest China.

Chigger mites (Acari) are common ectoparasites on rodents, and they are the exclusive vector of scrub typhus. South China field mouse (Apodemus draco) and Lantsang field mouse (A. ilex) are two sibling rodent species. Based on field investigations in southwest China (2001-2015), this paper compared the infestation of these two mouse species with chiggers. Of 42 chigger species identified from two mouse species, 36 were found on A. draco, 11 on A. ilex and 5 common species on both mice. Jaccard similarity index (J = 0.12, J < 0.25) showed a very different species composition of chiggers on two mouse species, and some parameters of the chigger community were also different. The overall mean intensity of chiggers on A. draco (MI = 4.26) was higher than that on A. ilex (MI = 3.91, p < 0.05). The dominant chigger species on A. draco were Trombiculindus yunnanus, Leptotrombidium scutellare (a major vector species in China) and L. sinicum with a total constituent ratio Cr = 42.9% (106/247). Leptorombidium sinicum and L. scutellare independently occurred on A. draco with an association coefficient V = 0.09 (V ≈ 0). The dominant chigger species on A. ilex were L. rusticum, L. densipunctatum and L. gongshanense, with a total Cr = 58.14% (25/43). Leptorombidium rusticum and L. densipunctatum on A. ilex had a slight positive association (V = 0.49, 0.5 < V < 1). All dominant chigger species were unevenly distributed among different individuals of two mouse species. Chigger infestation showed sex bias on different sexes of two mouse species. The species abundance of the chigger community on A. draco was revealed as a log-normal distribution pattern.

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.

Annotated checklist of chigger mites (Trombidiformes: Leeuwenhoekiidae, Trombiculidae and Walchiidae) in Sri Lanka.

Chigger mites (Leeuwenhoekiidae, Trombiculidae, and Walchiidae) are parasites of any terrestrial vertebrate. The present study updates the list of chigger mite (Trombiculidae, Leeuwenhoekiidae, and Walchiidae) species recorded from Sri Lanka along with taxonomic classification based on previous investigations since 1946 to date and our observations in western and southern parts of the country. This checklist listed 15 species in 9 genera within the three chigger families. For now, murid species were the host most sampledparasitized by chiggers in Sri Lanka. However, further studies are required to increase the diversity of chigger mites in Sri Lanka and probably the description of new species, which will be possible with morphological and molecular characterization.

Rickettsia felis and Other Rickettsia Species in Chigger Mites Collected from Wild Rodents in North Carolina, USA.

Chiggers are vectors of rickettsial pathogenic bacteria, Orientia spp., that cause the human disease, scrub typhus, in the Asian-Pacific area and northern Australia (known as the Tsutsugamushi Triangle). More recently, reports of scrub typhus in Africa, southern Chile, and the Middle East have reshaped our understanding of the epidemiology of this disease, indicating it has a broad geographical distribution. Despite the growing number of studies and discoveries of chigger-borne human disease outside of the Tsutsugamushi Triangle, rickettsial pathogens in chigger mites in the US are still undetermined. The aim of our study was to investigate possible Rickettsia DNA in chiggers collected from rodents in North Carolina, USA. Of 46 chiggers tested, 47.8% tested positive for amplicons of the 23S-5S gene, 36.9% tested positive for 17 kDa, and 15.2% tested positive for gltA. Nucleotide sequence analyses of the Rickettsia-specific 23S-5S intergenic spacer (IGS), 17 kDa, and gltA gene fragments indicated that the amplicons from these chiggers were closely related to those in R. felis, R. conorii, R. typhi, and unidentified Rickettsia species. In this study, we provide the first evidence of Rickettsia infection in chiggers collected from rodents within the continental USA. In North Carolina, a US state with the highest annual cases of spotted fever rickettsioses, these results suggest chigger bites could pose a risk to public health, warranting further study.

Annotated checklist of chigger mites (Trombidiformes: Leeuwenhoekiidae, Trombiculidae and Walchiidae) in Sri Lanka

Chigger mites (Leeuwenhoekiidae, Trombiculidae, and Walchiidae) are parasites of any terrestrial vertebrate. The present study updates the list of chigger mite (Trombiculidae, Leeuwenhoekiidae, and Walchiidae) species recorded from Sri Lanka along with taxonomic classification based on previous investigations since 1946 to date and our observations in western and southern parts of the country. This checklist listed 15 species in 9 genera within the three chigger families. For now, murid species were the host most sampledparasitized by chiggers in Sri Lanka. However, further studies are required to increase the diversity of chigger mites in Sri Lanka and probably the description of new species, which will be possible with morphological and molecular characterization.

Contribution to the knowledge of Quadraseta pazca (Brennan and Jones, 1964) (Trombidiformes: Trombiculidae), including new host-association and locality records

The Neotropical genus Quadraseta Brennan has 15 valid species associated with small mammals and birds. Quadraseta pazca (Brennan and Jones, 1964) is the type species chosen by Brennan (1970) to describe the genus Quadraseta. This species was originally described parasitizing murids in Argentina and later recorded parasitizing cricetids in two different Brazilian states, Minas Gerais and São Paulo. In this study, we provide a redescription of Q. pazca based on the type series. The following characters separate this species from the others within the genus: palptibia lateral setae branched; adoral setae branched; one pair of clavate trichobothria (si); leg I genu with three solenidia (σ); and the base of microseta (ε) of leg I tarsus is proximal to the base of solenidion (ω). In addition, we also provide new locality and host-association records for this species in Brazil.

Synonymy of Quadraseta brennani Goff & Whitaker, 1984 with Quadraseta antillarum (Brennan, 1967) (Trombidiformes: Trombiculidae)

Chiggers are ectoparasites of vertebrates and can cause trombiculiasis or transmit pathogens to their hosts. In the Neotropical region, the genus Quadraseta Brennan includes 16 valid species. Quadraseta antillarum (Brennan) and Quadraseta brennani (Goff & Whitaker), are morphologically identical and we propose the synonymy of Q. brennani with Q. antillarum, based on examination of both type series. The little big-eared bat, Micronycteris megalotis Gray from Venezuela is recorded as a new host.

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.

Contribution to the Taxonomy and Host-Relations of the Genus Serratacarus (Trombidiformes: Trombiculidae).

The genus SerratacarusGoff and Whitaker 1984, currently includes only two species, Serratacarus dietzi Goff and Whitaker, 1994 and Serratacarus lasiurus Goff and Whitaker, 1994, which were recorded on cricetid rodents from natural reserve areas of Brazil. Here, we provide a review of the morphological characters for both species and synonymize of the species Trombewingia brasiliensisGoff and Gettinger, 1991 with S. lasiurus. Additionally, we provide new locality records for both species and the first record for S. dietzi on southeastern four-eyed opossum, Philander frenatus Olfers, 1818 (Didelphimorphia, Didelphidae).

First report of Ericotrombidium ibericense in domestic dogs.

PURPOSE: Larval stages of trombiculid mites infest a wide variety of wild and domestic animals. The most common clinical signs related with the presence of these parasites are alopecia, crusts, erythema, excoriation, erosion, papules, pustules and vesicles. Most of trombiculid infestations may not be perceived by the clinician due to their small size. Although Ericotrombidium ibericense has been recorded on cats, it has not been found on dogs. METHODS: In August 2019, three domestic dogs presenting pruritic dermatological lesions in the ventral area of the body and interdigital spaces were presented at a veterinary clinic in Santarém, central Portugal. Trombiculid mites were extracted from the skin and preserved in 70% ethanol. Specimens were prepared in slides with Hoyer's medium and observed with optical microscopy. RESULTS: After morphological examination of the specimens, mites were identified as E. ibericense (Acariformes: Trombiculidae). CONCLUSIONS: Most of the trombiculids recorded in European clinical practice are generally identified as Neotrombicula autumnalis by default, since, in most cases, mites are not examined morphologically. This is the first record of E. ibericense in domestic dogs. More studies are needed to evaluate the distribution of these mites in Portugal. Veterinary clinicians must be aware of this parasitosis, as trombiculids can cause exuberant clinical signs, but are often misdiagnosed.

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

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).

A checklist of chiggers (Trombidiformes: Trombiculidae and Leeuwenhoekiidae) of Panama

An updated checklist of chiggers from the family Trombiculidae and Leeuwenhoekiidae is presented, with 81 species in 38 genera parasitizing different terrestrial vertebrate hosts in Panama. The depository for all Panamanian records, including new localities and host-associations records for the species Blankaartia sinnamaryi (Floch and Fauran, 1956), Eutrombicula tinami (Oudemans, 1910), Eutrombicula goeldii (Oudemans, 1910), Hooperella vesperuginis (Brennan and Jones, 1960), and Pseudoschoengastia bulbifera Brennan, 1960 were provided.

A new species of Hannemania Oudemans, 1911 (Trombidiformes: Leeuwenhoekiidae) from Brazil

Hannemania has 27 described species parasitizing amphibians in the Americas. To date, five species have been recorded from Brazil. Here, we describe a new species for the country, collected parasitising the South American white-lipped grass frog, Miranda’s white-lipped frog, basin white-lipped, Bahia dwarf frog and granular toad all from Ceará state, Brazil.

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

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).

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)

Contribution to the taxonomy and host-relations of the genus serratacarus (Trombidiformes: Trombiculidae)

The genus SerratacarusGoff and Whitaker 1984, currently includes only two species, Serratacarus dietzi Goff and Whitaker, 1994 and Serratacarus lasiurus Goff and Whitaker, 1994, which were recorded on cricetid rodents from natural reserve areas of Brazil. Here, we provide a review of the morphological characters for both species and synonymize of the species Trombewingia brasiliensisGoff and Gettinger, 1991 with S. lasiurus. Additionally, we provide new locality records for both species and the first record for S. dietzi on southeastern four-eyed opossum, Philander frenatus Olfers, 1818 (Didelphimorphia, Didelphidae).

Pathology of Trombiculosis caused by Neoschoengastia simonovichi in Wild Red-Legged Partridges (Alectoris rufa).

Lesions caused by trombiculid mite larvae ('chiggers') in birds have been inadequately described. A juvenile red-legged partridge (Alectoris rufa) presented with multifocal, crater-like lesions of necrotizing dermatitis, which often contained multiple orange mites. Microscopically, there was a nodular necrotizing and pyogranulomatous dermatitis with occasional intralesional arthropods. Histologically, the mites were readily identified by the presence of stylostomes within the necrotic areas. Morphological and morphometrical studies on isolated mites identified them as Neoschoengastia (Hypogastia) simonovichi. This is the first report of N. simonovichi as an aetiological agent of severe trombiculosis in wild birds in Western Europe. Infestation with this parasite requires further study to understand its role in animal and human trombiculosis and its potential role as a vector of infectious, including zoonotic, agents.