Analysis Of The Genetic Diversity Of Psoroptes Ovis Var.Cuniculi(Acari:Psoroptidae)in China,Inferred By Mitochondrial Cytochrome C Oxidase Subunit Ⅰ Gene(COⅠ),Mitochondrial Cytochrome C Oxidase Subunit Ⅱ Gene(COⅡ) And Ribosome Internal Transcribed Spac

Psoroptic mange in rabbit caused by Psoroptes ovis var.cuniculi is a common and highly contagious chronic skin disease in rabbit colonies.The infection rate was I1.11%～70.00%in China.The main clinical symptom of P.ovis infections in rabbits is pruritus and scabs in the external auditory canal.Psoroptic mange causes major economic losses due to the reduce of growth rate,feed conversion ratio and immunity,and even cause death if it is untreated.The areas of rabbit breeding are widely distributed in China which showed different climates,geological and topographical conditions.It is still unknown whether Psoroptes mites in rabbits from different regions can emerge genetic variation.In this study,the genetic diversity of Psoroptes ovis var.cuniculi isolated from Rex-Rabbit and Meat-Rabbit in warm temperate zone and subtropical zone of China(Southwest,Central,North,East and Northwest)had been analyzed.The main results are summarized as follows:1.Genetic diversity of Psoroptes ovis var.cuniculi of rabbits in China based on mitochondrial COI and COII geneIn order to investigate whether the genetic variation in Psoroptes ovis var.cuniculi can be affected by rabbit species,temperature zone and geographical origin,the mitochondrial cytochrome c oxidase I(COI)and mitochondrial cytochrome c oxidase Ⅱ(COII)of 128 P.ovis samples in rabbits collected from 14 regions(belonged to 8 provinces of 5 geographical regions in China)were amplified for the first time using the polymerase chain reaction(PCR)technology.Then,the genetic variation of these samples was evaluated based on COI,COII and concatenated COI+COII sequences.We successfully obtained 119 COI and 126 COII sequences and the lengths of the complete sequences of COI and COII were 1,548bp and 769 bp,respectively.117 concatenated sequences were obtained and the length was 2,317 bp.Based on single gene(COI,COII)and combined gene(COI+COII),Psoroptes ovis var.cuniculi.population in China showed high haplotype diversity(Hd:COⅠ=0.99174,COⅡ=0.91517,COI+COⅡ=0.99853)and nucleotide diversity(π:COⅠ=0.01004,COⅡ=0.00884,COⅠ+COⅡ=0.0099).Genetic distance analysis indicated that genetic distance between populations was not related to the geographical distance.Analysis of molecular variance(AMOVA)indicated that the genetic variation mainly occurred within the overall China populations(COI:87.63%,COII:93.97%,COI+COII:88.38%).Moreover,genetic diversity analysis showed that there was a certain genetic diversity across the population,but no significant genetic differentiation was existed among the populations(Fst:COI=0.1237;COII=0.0603;COI+COII=0.1162).The negative neutrality tests(Tajima’s D and Fu’s Fs)and mismatch distribution diagram with a multi-peak phenomenon indicated that Psoroptes ovis population was a stable population.Haplotype network diagram and ML tree were both revealed that the clustering of Psoroptes ovis var.cuniculi haplotypes was not related to rabbit species,temperature zone or geographical origin.In conclusion,our results showed that P.ovis population in China which presented a high level of genetic diversity and differentiation remained relatively stable for a long time.The genetic structure pattern was not formed based on rabbit species,temperature zone or geographical origin.2.Genetic diversity of Psoroptes ovis var.cuniculi population of rabbits in China based on ribosomal ITS sequenceIn order to further understand genetic variation of Psoroptes ovis var.cuniculi population in China,the nuclear ribosomal DNA internal transcribed spacer region(ITS)(ITS1,5.8S and partial ITS2)of 128 P.ovis samples in rabbits collected from 14 regions(belonged to 8 provinces of 5 geographical regions in China)were amplified,sequenced and analyzed.The lengths of ITS in 128 P.ovis isolates was from 800bp to 804bp and the homology of sequences was from 97.36%to 100.00%.There were 166 variation sites and 92 haplotypes among 128 ITS sequences.The Hd and π of the P.ovis population in China were 0.98364 and 0.02619,respectively.Genetic distance of P.ovis population from different geographical origins was irrelevant to geographic distance.There was an overwhelming genetic variability(97.23%)within the P.ovis population and there was no significant genetic differentiation among the P.ovis population(Fst=0.0277).A frequent gene flow existed among different geographical populations(Nm=8.7753).The negative neutrality tests(Tajima’s D=-0.19708 and Fu’s Fs =-4.46245)and mismatch distribution diagram indicated a multi-peak phenomenon.Haplotype network and ML tree showed that the P.ovis in China was not clustered as rabbit species,temperature zone or geographical origin,while the Psoroptes mites from rabbits clustered with mites from other hosts.In conclusion,based on a comprehensive analysis of mitochondrial and ribosomal genes,the Psoroptes ovis population in China had a high genetic diversity and a frequent gene flow within populations.This population did not experience a population expansion and remained a stable level for a long time.Moreover,it had not formed a genetic structure pattern according to rabbit species,temperature zone or geographical origin.