Distribution and Host Selection of Tropical Rat Mite, Ornithonyssus bacoti, in Yunnan Province of Southwest China

(1) Background: As a species of gamasid mite, the tropical rat mite (Ornithonyssus bacoti) is a common ectoparasite on rodents and some other small mammals. Besides stinging humans to cause dermatitis, O. bacoti can be a vector of rickettsia pox and a potential vector of hemorrhagic fever with renal syndrome (HFRS). (2) Objective: The present study was conducted to understand the host selection of O. bacoti on different animal hosts and the distribution in different environmental gradients in Yunnan Province of Southwest China. (3) Methods: The original data came from the investigations in 39 counties of Yunnan, between 1990 and 2015. The animal hosts, rodents and some other small mammals were mainly trapped with mouse traps. The O. bacoti mites on the body surface of animal hosts were collected and identified in a conventional way. The constituent ratio (Cr), prevalence (PM), mean abundance (MA) and mean intensity (MI) were used to reflect infestations of animal hosts with O. bacoti mites. The patchiness index and Taylor’s power law were used to measure the spatial distribution pattern of O. bacoti mites on their hosts. (4) Results: A total of 4121 tropical rat mites (O. bacoti) were identified from 15 species and 14,739 individuals of hosts, and 99.20% of them were found on rodents. More than half of O. bacoti mites (51.78%) were identified from the Asian house rat (Rattus tanezumi), and 40.09% of the mites from the Norway rat (R. norvegicus) (p < 0.05). The infestations of R. tanezumi (PM = 7.61%, MA = 0.40 and MI = 5.31) and R. norvegicus (PM = 10.98, MA = 1.14 and MI = 10.39) with O. bacoti mites were significantly higher than those of other host species (p < 0.05). The infestations of two dominant rat hosts (R. tanezumi and R. norvegicus) with O. bacoti mites varied in different environmental gradients (latitudes, longitudes, altitudes, landscapes and habitats) and on different sexes and ages of the hosts. The prevalence of juvenile R. norvegicus rats with O. bacoti mites (PM = 12.90%) was significantly higher than that of adult rats (PM = 9.62%) (p < 0.05). The prevalence (PM = 38.46%) and mean abundance (MA = 2.28 mites/host) of R. tanezumi rats with O. bacoti mites in the high latitude were higher than those in the low latitudes (p < 0.05). The majority of the total collected 4121 O. bacoti mites was found in the flatland landscape (91.28%) and indoor habitat (73.48%) (p < 0.05). The PM (10.66%) and MA (0.49 mites/host) of R. tanezumi rats with O. bacoti mites were significantly higher in the indoor habitat than in the outdoor habitat (p < 0.05). The tropical rat mites showed an aggregated distribution pattern on their first dominant host, R. tanezumi. Conclusion: The tropical rat mite (O. bacoti) is a widely distributed species of gamasid mite in Yunnan Province, Southwest China, and its dominant hosts are two synanthropic species of rats, R. tanezumi and R. norvegicus. It is mainly distributed in the flatland landscape and indoor habitat. It has some host-specificity, with a preference to rodents, especially R. tanezumi and R. norvegicus. The O. bacoti mites are of aggregated distribution on R. tanezumi rats.

Detection of DNA of Rickettsia and Orientia tsutsugamushi in rodents and ectoparasites in Ha Giang province

Rickettsial fever is one of a zoonotic disease which is caused by bacteria genus Rickettsia. The ectoparasites such as ticks, mites, fleas, lice... were demonstrated as the main transmited vectors through host reservoirs are rodents and small animals including mice, squirrels, mink... In this study, the rodents and ectoparasites species were identified. The molecular detection of Rickettsia was also performed. In 2018, 83 rats were trapped in 2 villages Thanh Duc and Phu Linh, Vi Xuyen district, Ha Giang province, in which 48.2% mice were found as house mice Rattus flavipectus, 21.7% was forest mice R. rattus, 12% was R. fulvescens, 8.4% was R. nitidus, the remaining rates were R. bowersi, Mus. pahari, Leopoldamys sabanus, Mus musculus and R. niviventer, accounting for 1.2% - 3.6%. The ectoparasites survey found 5 chigger mite species including Leptotrombidium (Leptotrombidium) deliense, Ascoschoengastia (Laurentella) indica, Garhliepia (Walchia) rustica, Lorilutum oreophilum and Shunsenia sp as well as 3 gamasid mite species such as Laelaps (Echidninus) sedlaceki, Laelaps (Laelaps) nuttali and Lenstivalius klossi bispiniformis. The result indicated that 19.3% and 10.8% mice were positive with Ricketsia spotted fever group (SFG) and Rickettsia typhi, respectively by real-time PCR. The nested PCR result showed that 19.4% R. flavipectus mice and 10% L. (L.) deliense chigger mites were positive with Orientia tsutsugamushi.

Redescription of the female of bumblebee-associated gamasid mite Proctolaelaps sibiriensis (Davydova, 1988) (Acari: Mesostigmata: Melicharidae) from North Asia

The female of Proctolaelaps sibiriensis (Davydova) (Acari: Mesostigmata: Melicharidae) is redescribed on the basis of type series and new materials collected from bumblebees (Hymenoptera: Apidae) in Tyumen Province, close to the type locality in Novosibirsk Province. A key to world bumblebee-associated species of the genus Proctolaelaps is presented.

North Pacific versus North Atlantic: a case with species of the amphiboreal littoral mite genus Thalassogamasus gen. nov. (Parasitifomes, Mesostigmata, Parasitidae)

A new amphiboreal gamasid mite genus, Thalassogamasus gen. n. is described, characterised by two distinct dorsal shields (opisthonotum hypotrichous, usually with ten pairs of setae); peritrematal shield reduced and posteriorly free; setae al1, al2 on palp genu and al on palp femur entire; dorsal chaetome homogenous; opisthosoma laterocaudally hypertrichous; in female, epigynium whip-like anteriorly, endogynium with two thick sclerotic masss; in male, tritosternum fully lost, hypostome deeply cleft, cheliceral arthrodial membrane fringelike. The new genus includes T. sidortschukae sp. nov. (Chukotka and Okhotsk coast), T. kurilensis sp. nov. (Kuril Islands) and T. lindrothi (Sellnick, 1974) (Iceland) comb. nov. The female of T. lindrothi (Sellnick, 1974) is considered conspecific with the male of Parasitus (Neogamasus) anderssoni Sellnick, 1974, comb. nov., syn. nov. All three Thalassogamasus species are seaside dwellers, inhabiting sandy beaches, salt marshes, and seaweed accumulations. Keys to the species (females and males) are presented. Peculiar morphological aspects of the dorsal shields, peritremes, and leg tarsi of the new genus are discussed. For another littoral species of Parasitidae, Parasitus kempersi Oudemans, 1902, a new combination is established, Phorytocarpais kempersi (Oudemans, 1902) comb. nov. Three littoral species of Uropoda (Phaulodinychus) Berlese, 1903 are first recorded from Russia: U. (P.) japanorepleta Hiramatsu, 1980 (northern and eastern Chukotka, Magadan Region, Kuril Islands), U. (P.) maritima Hiramatsu, 1977, and U. (P.) marihirschmanni Hiramatsu, 1977 (Kuril Islands).

Soil mesostigmatid mites as a potential tool for bioindication concerning ecological status of forest

Free-living predatory mesostigmatid soil mites from five different forests from the Danube Delta Biosphere Reserve (DDBR) were analyzed in order to get information for defining the conservation status of the investigated sites. On the whole, in the five studied sites 32 species of Mesostigmata belonging to 22 genera and 11 families were recorded. The analyzed material includes new species of Romanian fauna as well as rare and less cited species from Romania. A quarter of the identified species were formerly found in the Danube Delta, two species being identified only within DDBR territory. The particular conditions of each stand (vegetation, type of soil etc.) as well as climatic conditions influence both the quantitative and qualitative aspects of the structure of the mesostigmatid mites communities. Horizontal and vertical distributions and the aspects of demographic structure are discussed and the degree of similarity of the gamasid mite communities from the five sites were analyzed on the basis of specific composition and quantitative parameters.