Genus Identification And Phylogenetic Analysis Of Dermacentor On Body Surface And Molecular Diagnosis Of Theileriosis Of Xinjiang Sheep

Tick is a kind of specially hematophagous external parasite and can transmit various kinds of pathogenes such as viruses,bacteria,protozoa and spirochetes.The existence,dynamics and number of ticks have significant impact on the transmission of tick-borne diseases.Theileriosis is a kind of blood protozoonoses transmitted by ticks,which has seriously affected the development of sheep husbandry.Xinjiang is an important area of sheep husbandry in China,the land forms and terrains there are special and the faunal distribution of vector ticks is wide.The species and population structure of parasitic ticks on the body surface of sheep in Xinjiang are unclear,investigation or monitoring are lacking on the infection situation of ovine and caprine theileriosis,and understanding of the species of vector ticks of ovine and caprine theileriosis is absent.In order to solve the above problems,more targeted measures for effective prevention and control of ovine and caprine theileriosis were taken.Hematophagous hard ticks on body surface of sheep in several regions of Xinjiang were collected and identified,the dominant species and community composition of the parasitic ticks in different regions were analyzed,tick-borne and blood derived ovine and caprine theileriosis were detected,and phylogenetic analysis was carried out on epidemic strains of the ticks,hoping to provide base data and technical support for the monitoring of ticks and the study of vector ticks in this area and to lay the foundation for the comprehensive prevention and control of ticks and tick-borne theileriosis.(1)In the study,bloodsucking ticks with sheep were taken as the research objects.By means of morphology and statistics,identification and detection on the randomly collected 18,488 ticks were carried out and the results showed that,hard ticks are identified and classified into 3 genera and 7 species,including Dermacentor nuttalli(5,260,29%),Dermacentor silvarum(2,824,15%),Dermacentor niveus(691,4%),Dermacentor pavlovskyi(6,422,35%),Dermacentor marginatus(2,454,13%),Haemaphysalis punctata(633,3%)and Rhipicephalus turanicus(204,1%);experiments showed that Dermacentor is the main community species among parasitic ticks on the body surface of sheep in Xinjiang,Dermacentor nuttalli is the dominant species and the tick index is relatively high,being 113.58,Haemaphysalis punctata has the lowest tick index of 8.74;the tick index of sheep body surface in test point of Bazhou is higher than that in Altay,followed by that in lli and Hami(175.6 > 125.41 > 30.26 > 1.07);the community species richness in investigation sites in Altay is higher than that in other test points.(2)PCR technique was used to amplify the metagenomic DNA of Dermacentor marginatus,Dermcicentor nuttalli,Dermacentor silvarum,Dermacentor niveus and Dermacentor pavlovskyi to get the genes of ribosomal internal transcribed spacer 2(ITS2),mitochondrial cytochrome oxidase subunit I(COI)and mitochondrial ribosomal DNA(16S rDNA),and the above genes were respectively cloned for sequencing and analysis.Based on the listed correlation sequences,selective molecular systematics study was carried out on 5 species of dominantly distributed Dermacentors.By analyzing the base substitution ratio and genetic distance of the above three types of genes of the 5 species of Dermacentors,it's found that COI gene has more abundant variation points than the other two types of genes and the genetic distance between tick species is large,so the gene is more suitable for classification of Dermacentor genus.(3)In this study,657 sheep blood samples and 832 hard ticks were collected from the sheep husbandry in 10 counties and cities in Xinjiang.PCR technique was used to detect the Theileriosis,and sequencing,comparison and phylogenetic tree analysis were carried out.The results showed that the infection rates of blood derived and tick-borne Theileria ovis were 12.81%(38/657)and 2.88%(29/832),respectively;the test point in Jimunai County had the highest infection rate of 58%;it was found that both the blood derived and tick-borne ovine and caprine theileriosis are Theileria ovis,the similarity between the strain and that in Kashgar,Xinjiang(FJ603460)was 99.8%;phylogenetic tree was established based on 18 SrRNA gene sequence and the result showed that the blood derived Theileria ovis and tick-borne one are clustered into one branch,and then the branch is clustered with the Kashgar strain(FJ603460)Turkish strain(KT851435)and Iraqi strain(KJ452336)into a major branch;the Tanzanian strain(AY260173),Sudanese strain(AY260171),French strain(EU622911)and Spanish strain(AY533144)are clustered into one branch.In this experiment,the main local species of ticks that carries Theileria ovis include Dermcicentor nuttalli,Dermacentor silvarum,Dermacentor marginatus and Dermacentor pavlovskyi.