Analysis on infestation and related ecology of chigger mites on large Chinese voles (Eothenomys miletus) in five provincial regions of Southwest China.

Based on a long-term field investigation in the five provincial regions of Southwest China between 2001 and 2019, the present paper studied the infestation and related ecology of chigger mites (chiggers) on the large Chinese vole (Eothenomys miletus), an endemic and dominant rodent species in the regions. A total of 52331 chiggers were collected from 2661 voles, and 52261 mites were identified as 185 species and 13 genera in the family Trombiculidae with very high species diversity. The identified 185 chigger species on E. miletus (a single rodent species) even exceeded those recorded in some countries. The overall infestation prevalence (P m  = 53.96%), mean abundance (MA = 19.64) and mean intensity (MI = 36.39) on E. miletus were much higher than those on some other rodent species in the same regions. Although the species composition showed a moderate similarity (J = 0.63) between male and female hosts (E. miletus), the infestation indices (P m  = 56.25%, MA = 21.67) of chiggers on male hosts were higher than those on the females (P m  = 51.23%, MA = 17.09) (P < 0.05). Two dominant chigger species, Leptotrombidium scutellare (C r  = 19.17%) and L. sinicum (C r  = 11.06%), showed an aggregated distribution pattern among different individuals of their host E. miletus, and a relatively high degree of positive association existed between the two dominant chigger species with PCC = 0.57, DI = 0.60 and OI = 0.62 (x 2  = 857.46, P < 0.001). Leptotrombidium densipunctatum, Walchia koi, Helenicula hsui, L. scutellare and W. ewingi showed a high degree of environmental adaptability to their environments with high niche breadths. The theoretical curve of the species abundance distribution of chigger community on E. miletus was successfully fitted with Preston's lognormal distribution model. Based on the theoretical curve fitting, the expected total number of chigger species on E. miletus was roughly estimated to be 223 species, and 38 chigger species were probably missed in the sampling investigation.

Infestation of chigger mites on Chinese mole shrew, Anourosorex squamipes, in Southwest China and ecological analysis.

The Chinese mole shrew, Anourosorex squamipes Milne-Edwards, 1872, is a common species of insectivorous mammal in Southwest China. Based on field investigations between 2001 and 2019, the present study reports the infestation of chiggers (larvae of chigger mites) on the shrew in Southwest China and certain ecology parameters for the first time. A total of 3169 chiggers were collected from 1694 A. squamipes and they were identified into 72 species and 10 genera in the family Trombiculidae. The overall infestation prevalence (Pm), mean abundance (MA) and mean intensity (MI) of A. squamipes with chiggers reached 11.1%, 1.87 and 16.86, respectively. The species diversity, species composition and infestation of chiggers on A. squamipes fluctuated in different environments (latitudes, altitudes, habitats and landscapes) and on different sexes and ages of the shrew hosts with high heterogeneity and low species similarity. In the established linear regression equation (M* = 0.173 + 1.054 M) for dominant mite Leptotrombidium densipunctatum, both the α and ß values (α = 0.173, ß = 1.054) exceeded the boundary values (F = 4.67, p < 0.05), and therefore the spatial distribution pattern of this mite was determined as an aggregated distribution among different individuals of shrew hosts. The species abundance distribution of the chigger community on A. squamipes conformed to the lognormal distribution, and its curve showed a gradually descending tendency from the rare mite species to the dominant mite species. The curve tendency of species-sample relationship implies that more species of chiggers would be found if the host samples infinitely keep increasing.

Title: Infestation de la musaraigne Anourosorex squamipes par les acariens dans le sud-ouest de la Chine et analyse écologique. Abstract: La musaraigne Anourosorex squamipes Milne-Edwards, 1872 est une espèce commune de mammifère insectivore dans le sud-ouest de la Chine. Sur la base d'enquêtes de terrain entre 2001 et 2019, la présente étude signale pour la première fois l'infestation et certains paramètres écologiques des acariens larvaires sur cette musaraigne dans le sud-ouest de la Chine. Un total de 3169 acariens ont été collectés sur 1694 A. squamipes et ils ont été identifiés en 72 espèces et 10 genres de la famille des Trombiculidae. La prévalence globale de l'infestation (Pm), l'abondance moyenne (MA) et l'intensité moyenne (MI) des acariens sur A. squamipes ont atteint respectivement 11,1 %, 1,87 et 16,86. La diversité des espèces, la composition des espèces et l'infestation des acariens sur A. squamipes ont fluctué selon différents environnements (latitudes, altitudes, habitats et paysages) et selon le sexe et l'âge des hôtes avec une forte hétérogénéité et une faible similitude entre espèces. Dans l'équation de régression linéaire établie (M* = 0,173 + 1054 M) pour l'acarien dominant Leptotrombidium densipunctatum, les valeurs α et ß (α = 0,173, ß = 1,054) dépassaient les valeurs limites (F = 4,67, p < 0,05), et par conséquent, le modèle de distribution spatiale a été déterminé comme une distribution agrégée entre différents individus d'hôtes. La distribution de l'abondance des espèces de la communauté d'acariens sur A. squamipes se conformait à la distribution log-normale et la courbe a montré une tendance progressivement descendante des espèces d'acariens rares à l'espèce d'acarien dominante. La tendance de la courbe de la relation espèce-échantillon implique que davantage d'espèces d'acariens seraient trouvées si l'échantillonnage des hôtes continuaient à augmenter à l'infini.

Infestation and distribution of chigger mites on Chevrieri's field mouse (Apodemus chevrieri) in Southwest China.

Based on a long-term field investigation on chigger mites in southwest China from 2001 to 2019, the present study analyzed the infestation and distribution of chigger mites on the Chevrieri's field mouse (Apodemus chevrieri) in the region. A total of 12,516 individuals of chigger mites were collected from 1981 A. chevrieri mice, and 12,281 chiggers were identified as 107 species, 11 genera and 3 subfamilies in 2 families, which revealed a high species diversity of the mites on A. chevrieri mice. Of 1981 A. chevrieri mice, 633 ones were infested with chiggers with a relatively high overall prevalence (P M  = 31.95%), mean abundance (MA = 6.32) and mean intensity (MI = 19.77). Of the 107 chigger species identified from A. chevrieri mice, three ones were the most dominant and they were Leptrombidium scutellare, L. densipunctatum and L. cricethrionis, which showed aggregated distribution among different individuals of the mice. A slightly positive association existed between every two dominant chigger species, which implied that the dominant chigger species tend to co-exist on A. chevrieri. The infestations of A. chevrieri with chiggers varied in different latitudes, altitudes and landscapes and they showed some heterogeneity along different environmental gradients. The logistic regression analysis showed that the risk factors for chigger infestations on A. chevrieri were landscapes, ages and altitudes, which implied that the environmental factors and host ages could influence the infestations of the mice with the mites. A theoretical curve of the species abundance distribution of chigger mites on A. chevrieri was successfully fitted by Preston's lognormal model, suggesting that the species abundance distribution conforms to the lognormal distribution pattern. The expected total species of chigger mites on A. chevrieri was roughly estimated to be 136 species and about 29 rare chigger species were probably missed in the sampling field investigation.

Infestation and seasonal fluctuation of chigger mites on the Southeast Asian house rat (Rattus brunneusculus) in southern Yunnan Province, China.

Chigger mites are the common ectoparasites of rodents and the exclusive vector of scrub typhus. The Southeast Asian house rat (Rattus brunneusculus) is an important reservoir host and infectious source of some zoonoses including scrub typhus. From April 2016 to March 2017, a 12-month consecutive investigation was made at Jingha village in southern Yunnan of China, which is an important focus of scrub typhus. The infestation and seasonal fluctuation of chigger mites on R. brunneusculus were studied based on the investigation. From 2,053 captured R. brunneusculus, a total of 99,221 chiggers were collected and identified as comprising 102 species with very high species diversity. The richness (S), diversity index (H'), evenness (E) and dominance index (D) of the chigger community on the rat varied in different months. Of the 102 chigger species, five main species accounted for 84.81% of the total chiggers (84,147/99,221). The five main chiggers were Walchia (W.) micropelta (32.65%), Ascoschoengastia indica (24.68%), Leptotrombidium (L.) deliense (19.02%), W. (W.) turmalis (4.63%) and L. (L.) scutellare (3.83%). Of the five chigger species, L. (L.) deliense and L. (L.) scutellare are the most important vectors of scrub typhus in China. The five chigger species showed different patterns of seasonal fluctuation. The seasonal fluctuation of L. (L.) deliense belonged to summer-autumn type with the highest peak in July, but L.(L.) scutellare mainly appeared in winter and spring with the peak from January to February. The temperature and rainfall were two key factors which influenced the seasonal fluctuation of chigger mites.

A Report of Chigger Mites on the Striped Field Mouse, Apodemus agrarius, in Southwest China.

Based on the field investigations in 91 investigation sites (counties) in southwest China between 2001 and 2019, the present paper reported the chigger mites on A. agrarius mice in southwest China for the first time by using a series of statistical methods. From 715 striped field mice captured in 28 of 91 investigated sites, only 255 chiggers were collected, and they were identified as 14 species, 6 genera in 3 subfamilies under 2 families. Of 715 A. agrarius mice, only 24 of them were infested with chigger mites with low overall prevalence (PM=3.4%), overall mean abundance (MA=0.36 mites/host) and overall mean intensity (MI=10.63 mites/host). The species diversity and infestation of chiggers on A. agrarius were much lower than those previously reported on some other rodents in southwest China. On a certain species of rodent, A. agrarius mouse in southwest China seems to have a very low susceptibility to chigger infestations than in other geographical regions. Of 14 chigger species, there were 3 dominant species, Leptotrombidium sialkotense, L. rupestre and Schoengastiella novoconfuciana, which were of aggregated distribution among different individuals of A. agrarius hosts. L. sialkotense, one of 6 main vectors of scrub typhus in China, was the first dominant on A. agrarius. The species similarity of chigger mites on male and female hosts was low with CSS=0.25, and this reflects the sex-bias of different genders of A. agrarius mice in harboring different chigger species.

Functional importance of palmitoyl protein thioesterase 1 (PPT1) expression by Sertoli cells in mediating cholesterol metabolism and maintenance of sperm quality.

Sertoli cells are a type of nurse cell in the seminiferous epithelium that are crucial for sustaining spermatogenesis by extending nutritional and energy support to the developing germ cells. Dysfunction of Sertoli cells could cause disordered spermatogenesis and reduced fertility in males. In this study, we focused on the expression and function of palmitoyl protein thioesterase 1 (PPT1), a lysosomal depalmitoylating enzyme, in Sertoli cells. Here, we show that PPT1 expression in Sertoli cells is responsive to cholesterol treatment and that specific knockout of Ppt1 in Sertoli cells causes male subfertility associated with poor sperm quality and a high ratio of sperm deformity. Specifically, Ppt1 deficiency leads to poor cell variably accompanied with abnormal lysosome accumulation and increased cholesterol levels in Sertoli cells. Further, Ppt1 deficiency results in poor adhesion of developing germ cells to Sertoli cells in the seminiferous epithelium, which is likely to be responsible for the reduced male fertility as a consequence of declines in sperm count and motility as well as a high incidence of sperm head deformity. In summary, PPT1 affects sperm quality and male fertility through regulating lysosomal function and cholesterol metabolism in Sertoli cells.

Landscapes with different biodiversity influence distribution of small mammals and their ectoparasitic chigger mites: A comparative study from southwest China.

From a previous field investigation in Yunnan, southwest China between 2001 and 2015, we selected two types of landscapes to make a retrospectively comparative study on the distribution of small mammals and their ectoparasitic chigger mites. One landscape is "mountainous uncultivated land (MUL)" with higher biodiversity, which is located in a famous "World Nature Heritage Site", the Three-Parallel-Rivers Region in the northwest of Yunnan. The other is "cultivated flatland landscape (CFL)" with lower biodiversity, which is located in the south of Yunnan. The landscapes with different biodiversity apparently influenced the distribution of small mammals and their ectoparasitic chigger mites. Much more species of small mammals and mites were found in MUL than in CFL. A total of 3,177 small mammals captured from MUL were identified as 55 species, 30 genera and 10 families in five orders. From these small mammal hosts, 5,882 chigger mites were collected and identified as 127 species, 15 genera and 3 subfamilies in two families. A total of 1,112 small mammals captured from CFL were identified as 19 species, 12 genera and 5 families in three orders. From these hosts, 17,742 chiggers were collected and identified as 86 species, 12 genera and 3 subfamilies in two families. Both the species diversity (S = 55) and community diversity (H = 2.673) of small mammals in MUL were much higher than those in CFL (S = 19; H = 0.926). There were also higher values of ß diversity in MUL than in CFL. Different main reservoir rodent hosts of zoonoses (including tsutsugamushi disease) were found in two types of landscapes. Rattus tanezumi (one main reservoir host) was most abundant in CFL, which accounted for 80.22% of all the small mammals. Another two main reservoir hosts, Eothenomys miletus and Apodemus chevrieri were the dominant species in MUL, but they were not as abundant as R. tanezumi in CFL. Different vector species of chigger mites also existed in MUL and CFL. Leptotrombidium deliense (a main and powerful vector of tsutsugamushi disease in China) and Ascoschoengastia indica (a potential vector of tsutsugamushi disease) were the dominant species of chigger mites in CFL (Cr = 25.81% for A. indica; Cr = 23.47% for L. deliense). Leptotrombidium scutellare (also a main vector of tsutsugamushi disease in China) was the dominant chigger species in MUL (Cr = 26.09%). Higher infestation of vector mites on small mammals was found in the simple landscape with lower biodiversity (CFL) than in the complex landscape with higher biodiversity (MUL). The overall prevalence (P), mean abundance (MA) and mean intensity (MI) of chigger mites on small mammals were much higher in CFL than in MUL. The main vector mite species on their main rodent hosts also showed a higher P, MA and MI in CFL than in MUL.

Ectoparasitic insects and mites on Yunnan red-backed voles (Eothenomys miletus) from a localized area in southwest China.

Ectoparasitic insects and mites on Yunnan red-backed voles (Eothenomys miletus) in Dali prefecture, Yunnan Province, southwest China, were studied between 2003 and 2004. In total, 34,389 individuals of 86 species of ectoparasitic insects (seven species of fleas and five species of sucking lice) and mites (23 species of gamasid mites and 51 species of chigger mites) were collected from 916 individual hosts. The diversity of ectoparasites on this single rodent species in such a small area was much higher than in previous reports, which concerned more host species and greater geographical areas. The majority of the ectoparasites were chigger mites, which accounted for 59.3% of the parasite species and 87.4% of the individual parasites. Most voles harbored parasites with an overall prevalence (P) of 82.5% and mean abundance (MA) of 37.5 parasites per host. The dispersion coefficient (C) and patchiness index (m*/m) were used to study the spatial patterns of the seven dominant parasite species, and all seven had aggregated distributions. The species abundance distribution of the ectoparasites on the vole was fitted by Preston's lognormal distribution (R (2) = 0.82), and the total expected parasite species was estimated from this plot as 167 species. Yunnan red-backed voles harbor many ectoparasites as revealed by examination of a large host population. Future field investigations should sample large numbers of host individuals to assess ectoparasite populations.

[Diversity of ectoparasites on Niviventer confucianus in the surrounding areas of Erhai Lake].

OBJECTIVE: To understand the species diversity of ectoparasites on Niviventer confucianus in the surrounding areas of Erhai Lake. METHODS: Small mammals were randomly captured in 12 investigated sites surrounding Erhai Lake with baited mouse cages. The cage-traps were examined and re-baited each morning. Trapped small mammals were brought to the laboratory for identification according to color, body length, ear length, hind foot length. All ectoparasites on the surface of the hosts were collected and identified. The constituent ratio (C), prevalence (P) and average ectoparasite abundance (A) were used to evaluate the prevalence and density of ectoparasites. Non-parametric Mann-Whitney U-test was used to test differences in the abundance and richness of ectoparasites between female and male hosts. Spearman correlation analysis was used to analyze the relationship between ectoparasites and the body parameters of hosts. RESULTS: Eighty-nine individuals of N. confucianus were captured, of which 79% were found infested with 51 species of ectoparasites, including 31 species of chigger mites, 13 species of mesostigmatid (gamasid) mites, 4 species of fleas and 3 species of sucking lice. Walchia ewingi Fuller (66.2%), Laelaps turkestanicus Lange (38.5%), Paradoxopsyllus custodis Jordan (42.9%) and Hoplopleura pacifica (80.1%) were the most predominant species of chigger mites, gamasid mites, fleas, and sucking lice, respectively. Non-parametric Mann-Whitney U-test showed that there was no significant difference between male and female hosts on the species richness and abundance of total ectoparasites, chigger mites, sucking lice, fleas or gamasid mites. Spearman correlation analysis showed that the abundance and species of total ectoparasites, chigger mites, sucking lice, fleas or gamasid mites were not correlated with the body weight of hosts. CONCLUSION: There is a high speices diversity of ectoparasites on N. confucianus. Sucking lice, fleas, chiggers and gamasid mites are the main ectoparasites.

[Study of chigger communities on major species of rodents in Yunnan Province].

OBJECTIVE: To understand the characteristics of the chigger communities on the major species of rodent hosts. METHODS: Rats were captured in 16 counties (or towns) of Yunnan. All the mites on the two auricles of the host were collected and identified. Shannon-Weiner's indices (H,E), the richness indices and dominance indices were adopted to judge the diversity and community structure of chiggers on their hosts (7 species of rodents). RESULTS: From the 7 species of dominant rodent hosts, 131 species of chiggers were identified, belonging to 17 genera of Trombiculidae. Among them, abundant individuals were collected from 6 species which were considered to be dominant chigger species. Shannon-Weiner's indices (H) of the chigger communities showed the following sequence: Rattus norvegicus>Apodemus chevrieri>Eothenomys miletus>Mus pahari>Rattus nitidus>Rattus flavipectus>Mus caroli, and the richness indices were similar to this tendency. The niche breadth of the 6 dominant chigger species showed the following tendency: Herpetacarus hastoclavus>Leptotrombidium scutellare>Leptotrombidium sinicum>Helenicula siena>Leptotrombidium hiemalis>Leptotrombidium eothenomydis. There was a wide niche overlap between any two chigger species with all indices beyond 0.76. Slight positive association existed between each two dominant species of chigger mites by the coefficient of association (V). CONCLUSION: The community structure of chigger mites on the 7 major species of rodent hosts is complex, reflecting a high diversity of mite species. The niche breadth of the 6 dominant chigger species is different with a wide niche overlap.