The occurrence of dorsal bare area and ventro-lateral scales was studied in Sarcoptes scabiei (Linnaeus) females from three types of infestation: Norwegian Scabies (W. S S.I strain), an epidemic outbreak of classical scabies (HSC strain) and swine scabies (P strain). The presence of dorsal bare area did not differ between W, S S.l and HSC strains, but there was a difference between the human strains and P strain. Ventro-Iateral scales were not seen in P strain, but it was possible to identify them in one W. S S. 1 strain female. T he variability among strains difficults the identification of parasite morphology-host-clinical relationships.
Keywords: sarcoptes scabiei, norwegian scabies, morphologic variability, Costa Rica