Species diversity of ectoparasitic chigger mites (Acari: Prostigmata) on small mammals in Yunnan Province, China

Abstract

Chigger mites are a large group of arthropods and the larvae of mites are ectoparasites. Some species of ectoparasitic mites (larvae) can be the transmitting vectors of tsutsugamushi disease (scrub typhus). Yunnan Province is located in the southwest of China with complicated topographic landform and high biodiversity, where there are five zoogeographical subregions. Rodents and some other small mammals were trapped and examined for ectoparasitic chigger mites in 29 investigation sites in Yunnan during 2001-2013. From 13,760 individuals and 76 species of small mammal hosts, we collected 274 species of mites, which were identified as comprising 26 genera in two families. The species diversity of chigger mites (274 species) in the present study were not only much higher than that from other provinces of China but also largely exceeded that recorded from other regions and countries in the world. Of the five zoogeographical subregions, both the species diversity and Shannon-Weiner's diversity of mites were the highest in subregion II (southern subregion of Hengduan Mountains) with middle altitudes and middle latitude. Both the species diversity of mites and Shannon-Wiener diversity index showed a parabolic tendency from the low altitude (<500 m) to the high altitude (>3500 m) along the vertical gradients with the peak occurring in the middle-altitude regions (2000-2500 m). Of four dominant hosts, the species richness of mites was highest on Eothenomys miletus (S = 165) and Shannon-Wiener diversity index was highest on Rattus norvegicus (H = 3.13). Along latitude gradients, species richness of chigger mites increased first and then decreased, peaking at 25° to 26° N with 193 mite species. The geographical location, complex topography, and landscape with diverse small mammal hosts in Yunnan Province have contributed to the extremely high species diversity of mites in the province. The large sampling size of small mammal hosts in a wide geographical scope within a long time span also made it possible to have collected so many species of chigger mites.

Diversification of Orientia tsutsugamushi genotypes by intragenic recombination and their potential expansion in endemic areas

“…tsutsugamushi and multiple vector species in Taiwan is quite marked when compared to those of other endemic countries. The local prevalence of Leptotrombidium species is generally determined by multiple environmental factors such as temperature, precipitation, and host diversity [79,80]. Considering that L .…”

Research Progress on Leptotrombidium deliense

“…To date, more than 30 species of small mammals (mainly rodents and insectivores) and birds have been reported to be the hosts of L. deliense [12,23]. Of the various species of rodents (order Rodentia), the following species are the common hosts of L. deliense : Apodemus agrarius, A. chevrieri, Dremomys pernyi, Eothenomys miletus, E. custos, Mus pahari, Niviventer confucianus, N. fulvescens, N. andersoni, Rattus tanezumi ( R. flavipectus ), R. norvegicus, R. losea, R. rattus, R. brunneusculus ( R. sladeni ), R. nitidus, R. bowersi , among others [2,19,41,42]. Besides many species of rodents, some species in the order Insectivora (insectivores) and Scandentia (tree shrew) are also important hosts of the mite, L. deliense , for example, Anowrosorex squamipes, Crocidura dracula, C. attenuata, Hylomys suillus, Neotetracus sinensis and Suncus murinus .…”

“…This species of chigger mite ( L. deliense ) is common in some coastal areas and islands of Asian-Pacific regions with low altitude and hot weather. In some mountainous areas with high altitude, however, some other dominant species of chigger mites often take the place of L. deliense because of cold and dry weather [42]. Several investigators roughly divided various habitats into 2 types, the indoor habitat (houses, barns and stables) and outdoor habitat (paddy fields, various farmlands and cultivated habitats, uncultivated bush habitats, woodlands and forests, etc.…”

“…Several investigators roughly divided various habitats into 2 types, the indoor habitat (houses, barns and stables) and outdoor habitat (paddy fields, various farmlands and cultivated habitats, uncultivated bush habitats, woodlands and forests, etc. ), and found that L. deliense was distributed in both habitats, but mainly outdoors [19,41,42]. Other studies stated that L. deliense could be spread to some new places with heavy rain or flood because it could survive for a few days in fresh water or seawater [7,41].…”

“…Nonetheless, L. deliense was the dominant species of chigger mites in some places of Yunnan, especially in some flatlands and valleys along rivers with low altitude, hot and humid weather [2,41,42]. As one species of chigger mites in the family Trombiculidae, Leptotrombidium deliense has been proved to be the main vector of scrub typhus in many parts of Southeast Asia where scrub typhus, caused by the agent of O. tsutsugamushi infection, is the second common febrile disease next to malaria.…”