兔痒螨和水牛痒螨第二转录间隔区（ITS-2）基因序列分析

To clarify the taxonomic status of Psoroptes isolates from rabbits and buffalo, the second internal transcribed spacer (ITS-2) of the rRNA gene was investigated for the first time based on specimens of two isolates collected from rabbit and buffalo in Sichuan province, S.W. China, and compared with the homologous genes of other five Psoroptes isolates from other countries deposited in GenBank. The results of sequence analysis indicated that the lengths of ITS-2 in rabbit and buffalo isolates were 277 bp and 281 bp, respectively. There were many transitions, transversions and deletions in nucleotide sequences. Homology analyses indicated that the identity levels of nucleotide of ITS-2 between the buffalo isolate from Sichuan and other isolates from abroad ranged from 87.1% to 88.8%, while the gene homology of ITS-2 between the rabbit isolate from Sichuan and other isolates from abroad ranged from 95.5% to 100.0%. The topology of the phylogenetic trees based on ITS-2 gene revealed that the position of Psoroptes isolates from rabbits and buffalo was relatively fixed whether parsimony distance or likelihood methods were used. The phylogenetic analysis showed that the distance between Psoroptes isolates from rabbit and buffalo was relatively far. The results combined with reported evidences suggest that Psoroptes isolates from rabbits and buffalo may be two different species, namely the Psoroptes isolate from rabbit should belong to P. equi, while the Psoroptes isolate from buffalo may be another valid species in Psoroptes.