Molecular Phylogenetics On The Second Internal Transcribed Spacer Of The Genus Sarcoptes

The mite Sarcoptes scabiei is the causative organism of scabies, a debilitating skin condition endemic in many disadvantaged populations worldwide and responsible for epizootic mange in many wild and domestic animal populations. It has severely threat to the develedopment of animal husbandry. We used PCR to detect the genetic diversity and analysis of genetic relationship of the Sarcoptes scabiei isolates from difference places and hosts.Four isolates from three host specied in three places of the China (S.scabiei var. cuniculi from Zigong,S.scabiei var. cuniculi from Yaan, S.scabiei var. suis from Yingjing,S.scabiei var. caprae from Jianyang) was investigated to clarify the taxonomic status of mites of the genus Sarcoptes . A pair of primers were designed according to AF129164 in Genbank. Then the full length DNA of the second internal transcribed spacer (ITS2) gene of 4 isolated in China were amplified by PCR. The amplified products were coined into the pGM-T vector or pMD18-T vector and sequenced. The results showed that the nucleotide sequence length of ITS2 gene is all 361bp. The nucleotide sequences of the ITS2 gene of 4 S.scabiei isolates in China were analyzed and compared, the results showed that the nucleotide sequences homogeneity between them is 93.9%-98.3%. There was no deletion or insertion mutation within the 4 S.scabiei isolates. The base composition of the 4 S.scabiei isolates were biased ,averaging 61.10% A+T, similar to that observed previously in Sarcoptes (Zahler et al.,1999).The topology of the phylogenetic trees based ITS2 were relatively robust whether parsimony distance or likelihood methods were used. The S.scabiei var. cuniculi isolates from different place, the S.scabiei var. suis isolates from the China and Spain clustered together in all dendrogram. However, the phylogenetic status of S.scabiei var. caprae remained uncertain.ITS2 sequence comparisons and the dendrogram were obtained using the programs DNAstar and MEGA2.0. The comparion results showed that the nucleotide sequences homogeneity between the 4 S.scabiei isolates was very high, so we confirm the view that the genus Sarcoptes consists of a single, heterogenous species by the criterion of Zahler et...