Skin Scraping

This technique is used to recover small ectoparasites, particularly the various species of tiny mites associated with mange.

Deep scraping of the skin surface with a scalpel blade held perpendicular to the surface will recover sufficient epidermal tissue, skin debris and hair to be able to detect mange mites, if present, both those that burrow in the skin (e.g. Sarcoptes) and those that live on the skin surface (e.g. Psoroptes). To maximize parasite recovery, the scraping must be deep enough to draw blood (but not to bleed out the animal!). Usually the scalpel blade used is dipped into a little mineral oil before being used for the scraping. This helps the material collected, including the mites, adhere to the blade.

    Clippers

• Scalpel blade
• Slide
• Microscope

 Select an area for scraping at the edge of a visible lesion, where mites are likely more plentiful

2. Clip hair from area selected for scraping.
3. Squeeze the skin between thumb and forefinger and holding the scalpel blade perpendicular to the surface of the skin scrape the skin with enough pressure for blood to start to ooze from the skin surface.
4. Epidermal debris may be transferred directly to a microscope slide for examination.

Usually the scalpel blade used is dipped into a little mineral oil before being used for the scraping. This helps the material collected, including the mites, adhere to the blade. Sometimes the scraping will be examined directly, without digest. This may be satisfactory for surface mites but is not optimal for burrowing mites. In some cases, skin biopsies may be used in the diagnosis and investigation of ectoparasites, particularly those that burrow into the skin, but sensitivity is often sub-optimal.

In some types of mange (e.g. Sarcoptes), it may be very difficult to find mites in scrapings, and several areas of the skin may have to be examined. For all types of mange, it is important to scrape from lesions that appear “active” – reddened, weeping fluid, covered with new scab material. When examining scrapings microscopically, it is very important to look very carefully at the material in several focal planes.  Sometimes only fragments of mites or mite eggs are present; often these are sufficient for identification. It is also important to realize that, on occasion, free-living arthropods may be present on the skin surface, particularly of carcasses; these have to be differentiated from parasites.