Research Advances of Leptotrombidium scutellare in China.

Leptotrombidium scutellare is one of the 6 main vectors of scrub typhus in China. It has been found in more than 15 provinces of China. Especially in Yunnan, it was found to be mainly distributed in some mountainous areas with high altitude, low temperature and low precipitation. Rodents and some other small mammals were the most common hosts of L. scutellare. To date, more than 40 host species of L. scutellare have been recorded with very low host specificity, and the main hosts varied in different geographical regions. L. scutellare had a strong resistance against the cold environment, and the temperature and humidity were 2 important factors affecting its growth and development. Among different individuals of their rodent hosts, L. scutellare mites often showed an aggregated distribution pattern, which reflected the interspecific cooperation of the mites. The chromosome karyotype of L. scutellare was 2n=16 and all the 8 pairs of chromosomes were short rod-shaped with metacentric or sub-metacentric types. The isozyme spectrum supported that L. scutellare, L. deliense and L. rubellum were in the same species group. Based on the natural infection, experimental transmission and epidemiological evidence, L. scutellare has been eventually confirmed as the second major vector of scrub typhus in China, which is second only to L. deliense.

A New Genus and Species of Chiggers (Trombidiformes: Leeuwenhoekiidae) From Peru.

South American chiggers have historically been poorly studied, and this has continued into present times. Of the 33 genera in the family Leeuwenhoekiidae Womersley, only Odontacarus Ewing and Sasacarus Brennan & Jones have been reported in Peru. Here, we describe a new genus, Peruacarus n. gen., and a new species, Peruacarus anthurium n. sp., parasitizing Koford's grass mouse, Akodon kofordi Myers & Patton, in Peru.

New Species of Chiggers (Trombidiformes: Trombiculidae and Leeuwenhoekiidae) From the Conservation Unit Parque Nacional da Serra das Confusões, Brazil.

The Piauí State, Brazil, has never had its chigger fauna recorded. In this study, we examined chiggers collected on marsupials, rodents, and lizards from the conservation unit Parque Nacional da Serra das Confusões (PNSC). Herein we describe four new species, Paraguacarus klompenin. sp., Neoschoengastia ochoain. sp., Quadraseta welbournin. sp., and Susa bauchanin. sp. Furthermore, an additional seven species are reported: Eutrombicula alfreddugesi (Oudemans, 1910), Microtrombicula brachytrichiaBrennan, 1971, Microtrombicula rhipidomysiGoff, Whitaker and Dietz, 1983, Parascoschoengastia aemulata (Brennan and Jones, 1964), Parasecia validaBrennan, 1969, Pseudochoengastia petrolinensis Jacinavicius, Bassini-Silva and Barros-Battesti 2019, and Quadraseta flochi (Brennan and Jones, 1960). This is the first report of chiggers in Piauí State, which includes one of the most biodiverse areas in the Caatinga biome and is of particular importance to conservation. The genera Paraguacarus Goff and Whitaker, 1984 and Susa Audy and Nadcharam, 1960 are reported here for the first time to Brazil.

Severe Trombiculiasis in Hunting Dogs Infested With Neotrombicula inopinata (Acari: Trombiculidae).

This study records the clinical findings in nine hunting dogs showing systemic illness associated with trombiculids and identifies the mite species involved. In fall, coinciding with the seasonality of mites, all dogs were infested with mites and had been in the risk area (Sierra Cebollera Natural Park, La Rioja, Spain) a few hours before the onset of symptoms. The symptoms included vomiting, anorexia, weakness and lethargy, diarrhea, and even stupor. The clinical picture was fast-acting and potentially fatal. The infestations varied from low to severe. Molecular analysis of mites that fed on the dogs confirmed that they were larvae of Neotrombicula inopinata (Oudemans, Acari, Trombiculidae). This is the first time that N. inopinata has been identified as feeding on dogs and implicated in canine systemic illness associated with trombiculids. In contrast to other chiggers, N. inopinata does not seem to cause dermatitis. Likewise, the clinical and epidemiological similarity between the clinical symptoms we describe herein and the occurrence of seasonal canine illness (SCI) led us to suspect that this illness may be caused by infestation with these mites. The condition could be the consequence of severe infestation from large numbers of feeding mites, especially N. inopinata. Whether or not the cases were due to a severe allergic host response to salivary proteins or the result of the transmission of a new or emerging trombiculid-borne pathogen is not known.

The chiggers (Acari: Trombiculidae) on wild birds in Honduras.

The chiggers (Acari: Trombiculidae) Blankaartia sinnamaryi (Floch et Fauran, 1956), Parasecia soucouyanti (Brennan et Yunker, 1966), Eutrombicula lipovskyana (Wolfenbarger, 1952) and Neoschoengastia dalmati Brennan, 1951 were found in Honduras on a total of twelve bird species. Parasecia soucouyanti was recorded parasitising birds for the first time. All these mites are here reported from Honduras for the first time.

Evidence for co-invasion events: different chigger species (Actinotrichida, Trombidioidea: trombiculidae) share a host.

Cases of co-invasion of various chigger species parasitizing murids and cricetids in various habitats were analysed using morphological and molecular approaches. Here we provide evidence for 25 new cases of co-parasitism of chigger mites on rodent hosts (Myodes glareolus, Apodemus flavicollis, Apodemus agrarius) accounting for 8.6% of all host-parasite associations observed in this study. The results confirm higher incidence of co-parasitism in vertebrate-associated Parasitengona mites compared to arthropod-associated ones. Among factors influencing the occurrence of co-parasitism in Trombiculidae the body constitution and year-round availability of hosts associated with lower host specificity of larvae should be considered.

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.

Ectoparasitism by Chigger Mite Larvae (Acari: Trombiculidae) in a Wintering Population of Catharus ustulatus (Turdidae) in Southeastern Peru.

We document chigger mite (Acari: Trombiculidae) ectoparasitic infestation (prevalence and intensity) on a population of Catharus ustulatus (Turdidae) wintering at a site (PAD A) in southeastern Peru undergoing development for natural gas exploration. We compare prevalence (i.e., the proportion of individuals infested by chigger mites) and intensity (i.e., the average number of larvae and larvae clusters in infested individuals) at forest edge (<100 m) and interior (>100 m) from PAD A because variations in biotic (e.g., vegetation cover) and abiotic (e.g., relative humidity and temperature) factors are expected to influence chigger mite abundance. Chigger mite prevalence was 100%; all C. ustulatus captured were infested regardless of distance. The range of variation in larvae (2-72 larvae/individual) and cluster intensity (1-4 clusters/individual) did not differ between edge and interior ( P > 0.05), despite differences in herbaceous vegetation cover (UM-W = 180, n = 30, 31; P < 0.01). Ectoparasitic prevalence and intensity in long-distance migratory birds might add risks to an already hazardous journey; because ectoparasitic variation and other selective pressures experienced by individuals at each locality not only may be a cause of within-site mortality, but, by affecting the physical condition of birds, may be carried over to subsequent sites and affect reproductive success and survival. Documenting ectoparasitism at any phase of the life cycle of migrants could improve understanding of population declines of migratory birds.

Comparative stylostome ultrastructure of Hirsutiella zachvatkini (Trombiculidae) and Trombidium holosericeum (Trombidiidae) larvae.

Stylostomes (feeding tubes) of Hirsutiella zachvatkini (Schluger) (Trombiculidae), feeding on bank voles [Myodes glareolus (Schreber)], and of Trombidium holosericeum (L.) (Trombidiidae), feeding on larvae of Stenodemini sp. (Heteroptera, Miridae), were studied by TEM methods and on semi-thin sections. The stylostome of H. zachvatkini is a homogeneous structure of low electron density and without strict margins. It extends within the concave host epidermis, undergoing hyperplasia and hyperkeratosis. TEM does not reveal any obvious stratification in the stylostome walls. The cheliceral movable digits are moved apart by 5-6 µm and tightly applied/adhered to the stylostome substance. A local area beneath the open end of the stylostome canal is not empty but contains a nearly homogeneous substrate, which can pass into the central stylostome canal. The latter is mostly free of contents. In contrast to H. zachvatkini, larvae of T. holosericeum form a root-like stylostome chaotically branching within the clear space underneath the host cuticle free of tissue elements. Tubules of the distal stylostome branches become progressively thinner and disappear blindly. As in H. zachvatkini, the stylostome walls of T. holosericeum are devoid of stratification but show moderate to high electron density. The cheliceral movable digits are moved apart by the same distance, as in H. zachvatkini, and tightly applied to the stylostome substance. The lumen of the central canal is either electron lucent, in the distal portions, or filled with a fine granular or homogeneous substrate of low electron density in the proximal portions forming a type of ampoule. This study shows that Trombiculidae and Trombidiidae share similar initial stages of stylostome formation but the resultant stylostome of each family is distinctly different.

Eco-friendly control of the poultry red mite, Dermanyssus gallinae (Dermanyssidae), using the α-thujone-rich essential oil of Artemisia sieberi (Asteraceae): toxic and repellent potential.

The poultry red mite, Dermanyssus gallinae, represents a key threat for the poultry industry worldwide. The control of D. gallinae is mainly achieved by continuous applications of acaricides. However, the fast-growing development of resistance, and the strict laws concerning chemicals admitted for treatments on food animals, highlighted the importance of alternative control tools. Here, we explored the potential of Artemisia sieberi essential oil against D. gallinae. In this study, the A. sieberi essential oil was analyzed using GC and GC-MS. The oil toxicity through contact and fumigant assays on adult mites was evaluated. The oil repellent activity was assessed on adult mites over different time intervals. Lastly, the residual toxicity of various doses of the oil was evaluated on D. gallinae until 14 days post treatment. GC and GC-MS showed that the oil was rich in α-thujone (31.5%), ß-thujone (11.92%), camphor (12.3%), and 1,8-cineole (10.09%). Contact toxicity on adult mites showed 50% lethal concentration (LC50), LC90, and LC99 of 15.85, 26.63, and 35.42 µg/cm3, respectively. In fumigant assays, the oil was toxic on D. gallinae, and mortality was significantly higher in open containers over closed ones, underlining the key role of highly volatile constituents. Repellent assays showed that after 24 h from the treatment, all doses of the A. sieberi essential oil led to significant repellent activity over the control, except for 2 µg/cm3. After 48 h, A. sieberi essential oil tested at all doses led to significant repellent activity, if compared to the control. Residual toxicity assays showed that time exposure and concentration tested had a significant impact on mite mortality after 1, 2, 5, and 7 days from the treatment. Notably, mortality remained significantly higher over the control for 7 days after spraying with oil at 2%. Further field assays with selected molecules from the A. sieberi essential oil are ongoing, testing them in synergistic blends, as well as in microencapsulated formulations.

Description of Blankaartia shatrovi n. sp. (Acari: Trombiculidae) From Brazil.

The chigger mite genus Blankaartia includes 28 known species, of which 10 are distributed in the Nearctic and Neotropical regions. These species preferentially parasitize birds, but occasionally they can also be found on rodents, bats, and reptiles, showing low host selectivity. In the present study, we report the presence of this genus in Brazil for the first time, including the first report of Blankaartia sinnamaryi (Floch and Fauran) and the description of a new species of Blankaartia collected from birds (Order Passeriformes).

Meteorological factors affecting scrub typhus occurrence: a retrospective study of Yamagata Prefecture, Japan, 1984-2014.

Climate change, by its influence on the ecology of vectors might affect the occurrence of vector-borne diseases. This study examines the effects of meteorological factors in Japan on the occurrence of scrub typhus, a mite-borne zoonosis caused by Orientia tsutsugamushi. Using negative binomial regression, we analysed the relationships between meteorological factors (including temperature, rainfall, snowfall) and spring-early summer cases of scrub typhus in Yamagata Prefecture, Japan, during 1984-2014. The average temperature in July and August of the previous year, cumulative rainfall in September of the previous year, snowfall throughout the winter, and maximum depth of snow cover in January and February were positively correlated with the number of scrub typhus cases. By contrast, cumulative rainfall in July of the previous year showed a negative relationship to the number of cases. These associations can be explained by the life-cycle of Leptotrombidium pallidum, a predominant vector of spring-early summer cases of scrub typhus in northern Japan. Our findings show that several meteorological factors are useful to estimate the number of scrub typhus cases before the endemic period. They are applicable to establish an early warning system for scrub typhus in northern Japan.

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.

Two new species and new records of chiggers (Acari: Leeuwenhoekiidae, Trombiculidae) from birds in Vietnam.

A total of 12 chigger species (Acariformes: Trombiculidae) occurred on 7 bird species in Vietnam. Two new species, namely Neoschoengastia vietnamensis sp. nov. and Hypogastia stekolnikovi sp. nov. are described, figured and compared with similar species placed in relevant genera using differential diagnoses of related species. Figures and diagnosis of Leptotrombidium taiyuanense Tian and Wen, 1984 are added. Odontacarus audy (Radford, 1946), Leptotrombidium allosetum Wang, Liao and Lin, 1981, L. taiyuanense, Leptotrombidium hanseni Traub and Lakshana, 1966, Leptotrombidium kunshui Wen and Xiang, 1984, Leptotrombidium paradux Vercammen-Grandjean and Langston, 1976, Leptotrombidium turdicola Vercammen-Grandjean and Langston, 1976, Neotrombicula elegans Schluger, 1966 and Neoschoengastia longitar-salis Schluger and Belskaya, 1966 were recorded in Vietnam for the first time.

Evidence for interspecific interactions in the ectoparasite infracommunity of a wild mammal.

BACKGROUND: Co-infection with multiple parasite species is commonly observed in nature and interspecific interactions are likely to occur in parasite infracommunities. Such interactions may affect the distribution of parasites among hosts but also the response of infracommunities to perturbations. However, the response of infracommunities to perturbations has not been well studied experimentally for ectoparasite communities of small mammal hosts. METHODS: In the current study we used experimental perturbations of the ectoparasite infracommunity of sengis from Africa. We suppressed tick recruitment by applying an acaride and monitored the effects on the ectoparasite community. RESULTS: Our treatment affected the target as well as two non-target species directly. The experimental removal of the dominant tick (Rhipicephalus spp.) resulted in increases in the abundance of chiggers and lice. However, while these effects were short-lived in chiggers, which are questing from the environment, they were long-lasting for lice which spend their entire life-cycle on the host. In addition, the recruitment rates of some ectoparasite species were high and did not always correspond to total burdens observed. CONCLUSION: These findings indicate that infracommunity interactions may contribute to patterns of parasite burdens. The divergent responses of species with differing life-history traits suggest that perturbation responses may be affected by parasite life-history and that the ectoparasite infracommunity of sengis may lack resilience to perturbations. The latter observation contrasts with the high resilience reported previously for endoparasite communities and also suggests that anti-parasite treatments can affect the distribution of non-target species.

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.

Host-associated differences in morphometric traits of parasitic larvae Hirsutiella zachvatkini (Actinotrichida: Trombiculidae).

Examination of host-associated variation in the chigger mite Hirsutiella zachvatkini (Schluger) revealed morphological differences among larvae infesting sympatric hosts: Apodemus agrarius, Apodemus flavicollis and Myodes glareolus. The analysis included 61 variables of larvae obtained from their gnathosoma, idiosoma and legs (measurements and counts). Statistically significant differences were observed for metric characters of the legs as opposed to the scutum. In view of the conspecificity of the mites, supported by comparison of COI gene products obtained from larvae and laboratory-reared deutonymphs, the observed variation is attributed to phenotypic plasticity. The knowledge of larval morphology, including intraspecific variation of metric characters, supported by molecular and host range data, places H. zachvatkini among the most comprehensively defined members of Trombiculidae.

Comparative morphology and ultrastructure of the prosomal salivary glands in the unfed larvae Leptotrombidium orientale (Acariformes, Trombiculidae), a possible vector of tsutsugamushi disease agent.

The prosomal salivary glands of the unfed larvae Leptotrombidium orientale (Schluger) were investigated using transmission electron microscopy. In total, four pairs of the prosomal glands were identified--three pairs, the lateral, the medial and the anterior, belong to the podocephalic system, and one pair, the posterior, is separate having an own excretory duct. All glands are simple alveolar/acinous with prismatic cells arranged around a relatively small intra-alveolar lumen with the duct base. The cells of all glands besides the lateral ones contain practically mature electron-dense secretory granules ready to be discharged from the cells. The secretory granules in the lateral glands undergo formation and maturation due to the Golgi body activity. The cells of all gland types contain a large basally located nucleus and variously expressed rough endoplasmic reticulum. Specialized duct-forming cells filled with numerous freely scattered microtubules are situated in the middle zone of each gland's acinus and form the intra-alveolar lumen and the duct base. Both the acinar (secretory) and the duct-forming cells contact each other via gap junctions and septate desmosomes. Axons of nerve cells come close to the basal extensions of the duct-forming cells where they form the bulb-shaped synaptic terminations. The process of secretion is under the control of the nerve system that provides contraction of the duct-forming cells and discharge of secretion from the secretory cells into the intra-alveolar lumen and further to the exterior. Unfed larvae of L. orientale, the potential vector of tsutsugamushi disease agents, contain the most simply organized salivary secretory granules among known trombiculid larvae, and this secretion, besides the lateral glands, does not undergo significant additional maturation. Thus, the larvae are apparently ready to feed on the appropriate host just nearly after hatching.

Influence of Orientia tsutsugamushi infection on the developmental biology of Leptotrombidium imphalum and Leptotrombidium chiangraiensis (Acari: Trombiculidae).

Leptotrombidium chiangraiensis Tanskul & Linthicum, and Leptotrombidium imphalum Vercammen-Grandjean are important vectors of scrub typhus in rice field habitats in northern Thailand. The developmental biology of all stages of the life cycle of two generations of these species of mites infected with Orientia tsutsugamushi (Hayashi) and uninfected mites is reported. The development of the infected lines of both F1 and F2 L. chiangraiensis were significantly longer than their respective uninfected lines (P < 0.05). The developmental times of uninfected and infected F1 lines of L. imphalum were not significantly different; however, F2 infected lines took significantly longer to develop (P < 0.05). Both F1 and F2 generations of infected L. imphalum and L. chiangraiensis oviposited on average >150 fewer eggs than uninfected mites.