1.Infestation and distribution of chigger mites on Brown rat (Rattus norvegicus) in Yunnan Province, Southwest China
Ding, F. ; Guo, X.G. ; Song, W.Y. ; Fan, R. ; Zhao, C.F. ; Mao, K.Y. ; Zhang, Z.W. ; Peng, P.Y. ; Lin, H. ; Dong, W.G. ; Qian, T.J. ; Yang, Z.H. ; Zou, Y.J.
Tropical Biomedicine 2021;38(No.1):111-121
Chigger mites is a group of arthropods and some of them are vectors of scrub typhus. As a
common synanthropic rodent species, the Brown rat (Rattus norvegicus) often harbors lots of
ectoparasites including chigger mites. According to some “data mining” strategies, the present
study took the advantage of the abundant original data from a long-term field ecological
investigation between 2001 and 2015 to make a detailed analysis of chigger mites on
R. norvegicus in Yunnan Province, Southwest of China. From 18 of 33 investigated counties,
only 1414 chigger mites were collected from 1113 Brown rats with relatively low infestations.
The 1414 individual chigger mites were identified as comprising 61 species, 11 genera and
2 subfamilies of the family Trombiculidae with a high species diversity (S=61, H’=3.13). Of 61
mite species, there were four main species, Walchia ewingi, Ascoschoengastia indica, W. koi and
A. rattinorvegici, which accounted for 44.41% of the total mites. All the chigger mites were of
aggregated distribution among different individuals of R. norvegicus. The Brown rats in the
outdoor habitats harbored much more individuals and species of chigger mites with a
higher mean abundance (MA=1.46) and mean intensity (MI=12.53) than in the indoor habitats
(P<0.05). The overall infestation of the rats was significantly higher in the mountainous
landscapes than in the flatland landscapes (P<0.001). The species similarity (Css) of the
mites on the male and female rats reached 64.44% with sex biased infestations. The male
rats harbored more species and individuals of the mites than the female rats. The adult rats
harbored more species and individuals of the mites than the juvenile rats. The species
abundance distribution of the mites was successfully fitted by Preston’s lognormal model
with S
^
(R)=15e–[0.31(R–1)]2
(α=0.31, R2=0.95). On the basis of fitting the theoretical curve by Preston’s
model, the total mite species on R. norvegicus was estimated to be 86 species, and 25 rare
mite species were missed in the sampling field investigation. The curve tendency of the
species-plot relationship indicates that R. norvegicus have a great potential to harbor many
species of chigger mites, and more species of the mites would be collected if more rats are
sampled.