Researches On Host Specificity And Epidemiological Prediction Of Fleas And Sucking Lice In Yunnan Province

Objectives:(1) To comparatively study the ectoparasitic fleas and sucking lice on small mammals in Yunnan Province, which covered the host range, niche breadth and niche overlap; (2) To predict the prevalence of ectoparasitic fleas and sucking lice on some typical hosts by a certain epidemiological model.Materials and Methods:(1) The original data came from the field investigation in 23 locations of Yunnan Province from 1997 to 2009; (2) The constituent ratio (Cr), species richness (S), Levins'niche breadth and correspondence analysis were used to measure the host specificity. Based on Pianka's niche overlap of the dominant insect species, hierarchical cluster analysis was used to classify the niche overlapping groups, which reflect the host resource utilizations by corresponding ectoparasitic insects, fleas or sucking lice; (3) Taylor's power law indicating aggregation patterns, which based on mean abundance and variance of abundance, was used to predict the prevalence of both categories of insects, fleas and sucking lice, on a species of rat host, Rattus norvegicus.Results:(1) A total of 15 082 individuals of small mammals were captured and identified as five orders (Rodentia, Insectivora, Scandentia, Lagomorpha and Carnivora),10 families,35 genera and 65 species. From the body surface of small mammalian hosts,12 264 individuals of fleas were collected, which represents 6 families,26 genera and 51 species, and 38 885 individuals of sucking lice representing 5 families,7 genera and 31 species; (2) Most species of fleas have the high values of host range, niche breadth and niche overlap in comparison with sucking lice. Based on niche overlap, sucking louse species'resource utilization were sorted into 8 niche overlapping groups atλ= 15, whereas fleas were sorted into 4 groups; (3) Most species of sucking lice usually showed a higher host specificity at different taxonomic levels (species level, genus level and family level), and a certain species of sucking louse usually choose one or few small mammalian species as their dominant hosts, whereas fleas have a lower host specificity; (4) A highly linear correlation existed between the observed prevalence and predicted prevalence, a modeling efficiency of predicted prevalence against observed prevalence was successfully obtained with a high fitting goodness.Conclusions:(1) Ectoparasitic sucking lice have a higher degree of host specificity, and a prominent niche separation exists in the host selection of sucking lice. Sucking lice have a higher level of coevolution with their small mammal hosts since a certain species of sucking louse usually choose one or few small mammalian species as their dominant hosts; (2) In comparison with sucking lice, fleas have a lower degree of host specificity that varies among parasite species. Although most species of fleas exist niche overlap in the host selection of fleas, fleas have a lower level of coevolution with their small mammal hosts than sucking lice; (3) Vector-borne Diseases transmission between different hosts could be reduced by narrow host range, high degree of coevolution between sucking lice and their small mammalian host, and high host specificity, whereas viceversa increased vector-borne diseases transmission. This is the basic factor of fleas as vectors of zoonoses diseases (plague and endemic typhus, etc.) transmission between different animal hosts, and animal host to human host; (4) The prevalence of both fleas and sucking lice on Rattus norvegicus can be expected by an epidemiological model based on their mean abundance.