Species Identification Of Small Glires And Its Influence On The Study Of Echinococcosis Prevalence In Shiqu County

Echinococcosis is a kind of parasitic disease caused by the larval stage of Echinococcus spp.Small Glires are considered as the key intermediate hosts of Echinococcus.The Shiqu county is located in the eastern part of the Qinghai-Tibet plateau,it is one of the most serious epidemic areas of Echinococcosis in the world.In Shiqu county,the typical alpine meadow ecosystem provides good habitats and food source for small Glires and the small Glires are abundant in number and species.Understanding the community composition of small Glires and the infection rates of Echinococcus in specific species are of great significance for the preventation and treatment of Echinococcosis.However,due to the particularity of the ecological environment,there are still some problems and controversies on the species distribution and basic species classification of small Glires,especially the small rodents who are more abundant in species and more similar among different species.Therefore,this study mainly focuses on the following questions:（1）What is a more efficient classification method for local small rodents in Shiqu county?（2）What is the community composition of local small Glires in Shiqu county?（3）What are the infection rates of Echinococcus in different small Glires in Shiqu county?Eight quadrats（50 m×50 m）were randomly set to capture small Glires in Shiqu county.The Study can be divided into two parts.First,classify and identify the small Glires.The study mainly focuses on the classification of rodents based on the morphological and molecular methods because the classification characteristics of Lagomorpha are relatively obvious in the area.In the process of morphological classification,I compared the difference of molars among the species and did cluster analysis based on body and skull measurements.In the process of molecular biological classification,I constructed the phylogenetic tree,calculated the genetic distance,calculated the genetic differentiation coefficient(F_st)and analyzed the genetic structure based on mitochondrial Cytb gene and COI gene,nuclear i7FGB gene and GHR gene.Second,I detectd the suspected lesions and liver tissues of small Glires based on the mitochondrial COI gene and NDI gene,and counted the infection rates of Echinococcus in different species.A total of 419 Glires were captured in the study,including Lagomorpha（166）and Rodentia（253）.The Lagomorpha were all Ochotona curzoniae.The results showed that the morphological classification method based on molar characteristics was effective for Rodentia（95%,241/253）,but there were ten individuals whose bilateral lower molars were different and two individuals whose key identification characteristics were lacking.They could not be accurately identified in this way.The Rodentia were composed of Lasiopodomys fuscus,Neodon irene,Phaiomys leucurus,Microtus limnophilus and Cricetulus longicaudatus in Shiqu county and the Lasiopodomys fuscus is the main local small rodents.Lasiopodomys fuscus,Neodon irene,Phaiomys leucurus and the individuals whose bilateral lower molars are different could not be classified based on the measurements or the four genes.The total infection rates of Echinococcus were 0.7%（Conservative Infection Rate,CIR）-4.3%（Maximum Infection Rate,MIR）in Glires classified by the morphological classification method,and the infection rates of E.multilocularis were0.2%（CIR）-2.6%（MIR）,the infection rates of E.shiquicus were 0.5%（CIR）-1.7%（MIR）.There were no individual infected by E.granulosus.The infection rates of Echinococcus were different in different species,Lasiopodomys fuscus and Ochotona curzoniae were higher.As main small rodents in Shiqu county,the Lasiopodomys fuscus could not be effectively distinguished from the other two species and the individuals whose bilateral lower molars are different based on the four genes,here I defined them as Lasiopodomys complex.The infection rates of Echinococcus in Lasiopodomys complex are lower than Lasiopodomys fuscus.There are the main conclusions of this study based on the above results:（1）The Cytb gene,COI gene,i7FGB gene and GHR gene can not be used as effective DNA barcodes to realize the effective differentiation of Lasiopodomys fuscus,Neodon irene or Phaiomys leucurus in Shiqu county.The morphological classification method based on molar characteristics is effective for the classification of local small rodents except for particular individuals whose bilateral lower molars are different or key identification characteristics are lacking.（2）In Shiqu county,there are Lagomorpha（Ochotona curzoniae）and Rodentia（Lasiopodomys fuscus,Neodon irene,Phaiomys leucurus,Microtus limnophilus and Cricetulus longicaudatus）.Ochotona curzoniae and Lasiopodomys fuscus are the main local small Glires.（3）In Shiqu county,there may be a certain degree of hybridization among rodents based on the results of morphological classification and molecular biological classification.（4）In Shiqu county,Ochotona curzoniae,Lasiopodomys fuscus and Phaiomys leucurus can be the intermediate hosts of E.multilocularis and E.shiquicus.The infection rates of Ochotona curzoniae and Lasiopodomys fuscus are higher than other Glires classified by the morphological classification method.（5）Lasiopodomys fuscus is the main small rodents in Shiqu county and the main infected species of Echinococcus.I defined the Lasiopodomys complex here because the Lasiopodomys fuscus can not be distinguished from the other two species and the individuals whose bilateral lower molars are different based on molecular biological methods in Shiqu County.The infection rates of Echinococcus in Lasiopodomys complex is lower than the actual infection rates in Lasiopodomys fuscus.Therefore,a standard and effective classification method for Glires is particularly important for the study of Glires-hosted parasitic diseases such as Echinococcosis.