Response of Sarcoptes scabiei var. canis (Acari: Sarcoptidae) to lipids of mammalian skin.

Bioassays were conducted to determine if Sarcoptes scabiei (L.) were attracted to lipid compounds that occur in or on the epidermis of human or other mammalian skin. Seventeen lipid compounds attracted S. scabiei including odd and even carbon chain lengths and saturated and unsaturated fatty acids, fatty acid methyl esters, a steroid, a steroid precursor, and a triglyceride. The attractive saturated fatty acids were pentanoic (5:0), hexanoic (6:0), octanoic (8:0), lauric (12:0), pentadecanoic (15:0), and stearic (18:0) acids. The unsaturated fatty acids oleic (18:1 delta), linoleic (18:2 delta), and arachidonic (20:4 delta) acids also attracted scabies mites. No concentration of sebacic (10:0), myristic (14:0), palmitic (16:0), or arachidic (20:0) acids attracted any life stage of S. scabiei. Five fatty acid methyl esters attracted at least one life stage of mites. Cholesterol and squalene, its transient precursor, were both attractive as was the triglyceride, tripalmitin. The molar concentration of lipids that elicited the greatest response by a particular life stage varied between compounds (ranging from 1 to 0.0001 M). Some lipids were attractive at several concentrations, whereas for others a response was elicited by only one concentration. A comparison of different life stages showed that adults, especially females, were attracted more than immatures to most of the compounds. The data show that lipids that occur in the epidermis of human or other mammalian skin attract scabies mites. Therefore, host skin lipids may contribute to host specificity, attract mites to specific anatomical areas of the body, or play key roles in other host-parasite relationships.