Ribosomal and mitochondrial DNA sequence variation in Sarcoptes mites from different hosts and geographical regions.

In order to investigate the extent of the genetic variation in the DNA sequences of Sarcoptes scabiei, mite populations collected on Alpine chamois ( Rupicapra rupicapra), Pyrenean chamois ( Rupicapra pyrenaica) and red fox ( Vulpes vulpes) from different localities of Italy and Spain were studied. Sequence analyses were carried out on the second internal transcribed spacer of the nuclear ribosomal DNA and on the 16S mitochondrial rRNA gene. ITS-2 sequences showed a higher degree of genetic polymorphism, mostly randomly distributed in the isolates from different hosts and localities, although both genomic regions are characterised by fixed nucleotide substitutions which were able to discriminate the mites collected on Pyrenean chamois from north-western Spain and on foxes from north-eastern Spain and from north-western Italy with respect to the other isolates. These results suggest the existence of a limitation to free gene exchange between the studied populations, probably related to the genetic structuring of local populations rather than to a differential adaptation to host species.