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

Abstract

(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.

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

“…The high species diversity of chigger mites (107 species) on A. chevrieri mouse may reflect the mouse's high potential of harboring abundant mite species. The complicated topography and diverse climate types in southwest China may also contribute to the high species of chigger mites in the region ( Peng et al, 2016 ; Ding et al, 2021a ; Yin et al, 2021 ). Besides, the wide investigation scope in 91 investigation sites of five provincial regions with large host samples (1981 A. chevrieri mice) is also an important factor to lead to the high species of chigger mites in the present study.…”

“…The association coefficient ( V ) used in the present study is a common and applicable way to measure the interspecific relationship between any two species of chigger mites on their hosts ( Liu et al, 2020b ; Yin et al, 2021 ). The result showed that the interspecific association between any two of three dominant chigger species ( L. scutellare , L. densipunctatum and L. cricethrionis ) were slightly positive ( V > 0, P < 0.05), which indicates that the dominant chigger species have a tendency to co-exist on the body surface of A. chevrieri mice.…”

“…Based on the establishment of a contingency table (see Table 4 in “Results”), the association coefficient ( V ) was used to calculate the interspecific association between any two species of chigger mites (chigger species) on the mouse host, A. chevrieri mice. Chi-square test was used for testing the statistical significance of V ( Guo et al, 2006 ; Yin et al, 2021 ). …”

Infestation and Seasonal Fluctuation of Gamasid Mites (Parasitiformes: Gamasida) on Indochinese Forest Rat, Rattus andamanensis (Rodentia: Muridae) in Southern Yunnan of China

“…The constituent ratio ( C r ), prevalence ( P M ), mean abundance ( MA ) and mean intensity ( MI ) were used to calculate the infestation of R. andamanensis with gamasid mites, in which C r represents the percentage of a certain species of gamasid mite in all the mites, P M the percentage of the infested rat hosts with gamasid mites in all the rat hosts, MA the average number of gamasid mites per captured rat host and MI the average number of gamasid mites per infested rat host [ 7 , 27 , 28 , 29 ]. The richness index ( S ), Shannon-Wiener’s diversity index ( H′ ), Pielou’s evenness ( E ) and Simpson’s dominance index ( D ) were used to calculate the community structure of the gamasid mite community on the rat R. andamanensis [ 27 , 30 ].…”

“…Some gamasid mites are ectoparasites and they are often found on the body surface of rodents and some other small mammals [ 5 , 6 ]. The ectoparasitic gamasid mites can directly sting the human body and cause dermatitis, and some of them can be the vector or potential vector of some zoonotic diseases (zoonoses), such as rickettsialpox and hemorrhagic fever with renal syndrome (HFRS) [ 7 , 8 ]. Rodents and some other small mammals (insectivores and tree shrews) are the most important hosts of ectoparasitic gamasid mites [ 9 , 10 , 11 , 12 ].…”