Alexandr A. Stekolnikov

Neotrombicula inopinata (Acari: Trombiculidae) - a possible causative agent of trombiculiasis in Europe

BackgroundFor over a decade, the presence of trombiculid mites in some mountain areas of La Rioja (Northern Spain) and their association with seasonal human dermatitis have been recognized. This work aimed to establish the species identity of the agent causing trombiculiasis in the study area.MethodsTrombiculid larvae (chigger mites) were collected from vegetation in the Sierra Cebollera Natural Park and in Sierra La Hez during an outbreak of human trombiculiasis in 2010. Three specimens collected from a bird were also examined. Identification was made using morphological and morphometric traits based on the most recent taxonomic sources. A comparison of those mites with specimens of the same species collected throughout Europe was performed by means of cluster analysis with multiscale bootstrap resampling and calculation of approximately unbiased p-values.ResultsAll collected mites were identified as Neotrombicula inopinata (Oudemans, 1909). Therefore, this species is the most likely causative agent of trombiculiasis in Spain, not Neotrombicula autumnalis (Shaw, 1790), as it was generally assumed. No chigger was identified as N. autumnalis in the study area. Neotrombicula inopinata clearly differs from N. autumnalis in the presence of eight or more setae in the 1st and 2nd rows of dorsal idiosomal setae vs. six setae in N. autumnalis. Comparison of N. inopinata samples from different locations shows significant geographic variability in morphometric traits. Samples from Western and Eastern Europe and the Caucasus formed three separate clusters.ConclusionSince the taxonomical basis of many studies concerning N. autumnalis as a causative agent of trombiculiasis is insufficient, it is highly possible that N. inopinata may be hiding behind the common name of “harvest bug” in Europe, together with N. autumnalis.

Redescription of a human-infesting European trombiculid mite Kepkatrombicula desaleri (Acari: Trombiculidae) with data on its mouthparts and stylostome

ABSTRACT External morphology of trombiculid larvae Kepkatrombicula desaleri (Methlagl, 1928) collected on chamois in Alps with special consideration of the mouth apparatus was studied by scanning electron microscopy (SEM). Standard morphological description of this species using optical microscopy is also given, with the discussion on its taxonomy. Neotype of K. desaleri is designated. Feeding tube or stylostome formed by larvae in the host skin was examined using histological methods. Larvae of this species possess an unusual organization of the apical portions of the hypostome forming a soft sucker disk. The latter being applied to the stratum corneum of the host epidermis provides an additional pumping effect for engorgement of food through the long stylostome that may extend deep into the dermis at different angles to the surface of the epidermis. Stylostome corresponds to the mesenchymal type of stylostome. Skin reaction is strong and is expressed in the intensive infiltration of the inflammatory foci with leukocytes and erythrocytes. Besides fluid components of the inflammatory focus and cellular debris, larvae also may uptake the whole erythrocytes. Edema, scab formation, as well as the epidermal hyperplasia and hyperkeratosis are not characterized for feeding of larvae of this species. Stylostome organization and the character of the skin inflammatory reaction suggest that big animals like chamois and probably humans are not natural hosts for larvae of this species that may serve as vector of Rickettsiae and causes trombidiosis in man.

A review of Chilean chiggers (Acari: Trombiculidae), with the description of a new genus and ten new species

A new genus and species of chigger mites, Diaguitacarus choapensis gen. et sp. nov., is described from four lizard species of the genus Liolaemus in Choapa Province of Chile. Eight new chigger species are described from lizards of the genera Liolaemus, Phymaturus (Squamata: Liolaemidae), and Microlophus (Squamata: Tropiduridae), in Arica and Parinacota, Atacama, Coquimbo, Valparaíso, and Biobío Regions: Eutrombicula nerudai sp. nov., Eutrombicula mistrali sp. nov., Eutrombicula picunche sp. nov., Microtrombicula mapuche sp. nov., Parasecia molini sp. nov., Paratrombicula philippii sp. nov., Morelacarus jorgei sp. nov., and Morelacarus camanchaca sp. nov. A new species Proschoengastia antarctica sp. nov., which is described from American mink Neovison vison on Navarino Island (Region of Magallanes and Antártica Chilena), is the most southerly chigger species, found at the distance of about 1000 km from the continent of Antarctica. Whartonacarus chaetosus (Brennan and Jones, 1961) comb. nov., which was described from Peru, is for the first time recorded in Chile (Atacama Region) and on Microlophus atacamensis. A new combination Proschoengastia macrochaeta (Brennan and Jones, 1961) comb. nov. is established. The genus Morelacarus Vercammen-Grandjean, 1973 previously known from Mexico and southwestern USA is for the first time recorded in Chile. A review of all previously described Chilean chiggers and a key to Eutrombicula species from Chile are provided. In all, 22 species from 13 genera were recorded in Chile, of which only one species (Whartonacarus chaetosus) is known outside the country.

A Revised Checklist of Chigger Mites (Acari: Trombiculidae) From Thailand, with the Description of Three New Species

Abstract Chigger mites of Thailand were studied on the basis of larvae collected from 19 small mammal species (17 species of Rodentia, 1 species of Erinaceomorpha, and 1 species of Scandentia) and revision of published data. Samples of 38 trombiculid species were collected from 11 provinces. Three new species were described: Trombiculindus kosapani sp. nov., Helenicula naresuani sp. nov., and Walchia chavali sp. nov. Ten species were recorded in Thailand for the first time: Leptotrombidium sialkotense Vercammen-Grandjean and Langston, 1976; Leptotrombidium subangulare Wen and Xiang, 1984; Leptotrombidium tenompaki Stekolnikov, 2013; Leptotrombidium turdicola Vercammen-Grandjean and Langston, 1976; Leptotrombidium yunlingense Yu, Yang, Zhang and Hu, 1981; Lorillatum hekouensis Yu, Chen and Lin, 1996; Helenicula pilosa (Abonnenc and Taufflieb, 1957); Gahrliepia xiaowoi Wen and Xiang, 1984; Walchia minuscuta Chen, 1978; and Walchia ventralis (Womersley, 1952). In all, 99 chigger mite species were considered; the presence of 93 species was established in Thailand by original data or properly documented records in the scientific literature. Evidence for 64 species records of 147 from a previous checklist of Thai chiggers (Tanskul 1993) remains unknown. Distribution of chigger species by geographical regions of Thailand is discussed.

Four new species of chigger mites (Acari: Trombiculidae) of the genus Eutrombicula from Chile

ABSTRACT Four new species of chigger mites, Eutrombicula chillanensis n. sp., Eutrombicula araucanensis n. sp., Eutrombicula liolaemi n. sp., and Eutrombicula paula n. sp., are described from three species of South American ground lizards of the genus Liolaemus Wiegmann, 1834 collected in Chile.

Contributions to the fauna of reptilian chiggers (Acari: Trombiculidae) from the Central Mediterranean, with a description of one new species

A new species of chigger mite, Lacertacarus sardiniensis sp. nov., is described from a lizard Podarcis tiliguerta (Gmelin) collected in Sardinia. One species, Ericotrombidium caucasicum (Schluger, 1967), previously known from Southern Russia and Southern Ukraine, is recorded for the first time on the lizards Podarcis filfolensis (Bedriaga) and Podarcis siculus (Rafinesque-Schmaltz), and on Malta, Lipari Island and Alicudi Island (Aeolian Islands, Sicily, Italy). http://zoobank.org/urn:lsid:zoobank.org:pub:CD41E85B-1801-4FA3-BC42-28F5F1AC14C1

Autofluorescence microscopy for paired-matched morphological and molecular identification of individual chigger mites (Acari: Trombiculidae), the vectors of scrub typhus

Background Conventional gold standard characterization of chigger mites involves chemical preparation procedures (i.e. specimen clearing) for visualization of morphological features, which however contributes to destruction of the arthropod host DNA and any endosymbiont or pathogen DNA harbored within the specimen. Methodology/Principal findings In this study, a novel work flow based on autofluorescence microscopy was developed to enable identification of trombiculid mites to the species level on the basis of morphological traits without any special preparation, while preserving the mite DNA for subsequent genotyping. A panel of 16 specifically selected fluorescence microscopy images of mite features from available identification keys served for complete chigger morphological identification to the species level, and was paired with corresponding genotype data. We evaluated and validated this method for paired chigger morphological and genotypic ID using the mitochondrial cytochrome c oxidase subunit I gene (coi) in 113 chigger specimens representing 12 species and 7 genera (Leptotrombidium, Ascoschoengastia, Gahrliepia, Walchia, Blankaartia, Schoengastia and Schoutedenichia) from the Lao People’s Democratic Republic (Lao PDR) to the species level (complete characterization), and 153 chiggers from 5 genera (Leptotrombidium, Ascoschoengastia, Helenicula, Schoengastiella and Walchia) from Thailand, Cambodia and Lao PDR to the genus level. A phylogenetic tree constructed from 77 coi gene sequences (approximately 640 bp length, n = 52 new coi sequences and n = 25 downloaded from GenBank), demonstrated clear grouping of assigned morphotypes at the genus levels, although evidence of both genetic polymorphism and morphological plasticity was found. Conclusions/Significance With this new methodology, we provided the largest collection of characterized coi gene sequences for trombiculid mites to date, and almost doubled the number of available characterized coi gene sequences with a single study. The ability to provide paired phenotypic-genotypic data is of central importance for future characterization of mites and dissecting the molecular epidemiology of mites transmitting diseases like scrub typhus.

First finding of the chigger mite Neotrombicula talmiensis (Acari: Trombiculidae) in Italy

The first record of the chigger mite Neotrombicula talmiensis (Schluger, 1955) in Italy and on the grey squirrel Sciurus carolinensis Gmelin is reported. Four chigger specimens were found on this invasive North American squirrel species in February 2014 in the territory of Parchi di Nervi, Genoa.