“Deeeeep and wide, Deeeeep and wide, there’s a fountain flowing deep and wide.”
I never fail to think of that church song from my childhood when it’s time to perform a skin scraping on a patient. I have the late Dr. Matt Wiggins, our Auburn University College of Veterinary Medicine dermatology professor to thank for that.
“Whenever you do a skin scraping, it has to be deep and wide. Every time. You aren’t through with a skin scraping unless it’s deep and wide,” he would always say.
Skin scraping is a dermatologic tool used for demonstrating parasites in the skin of patients of all species, including humans.
It is used most commonly to search for Demodex canis, the causative organism of Demodicosis, one of the four types of mange in dogs. Cats have their own Demodex, Demodex felis.
Skin scraping is also utilized in the search for Sarcoptes scabiei, the mite that causes scabies in dogs, cats and sometimes people. If your pet’s doctor suspects S. scabiei as the main offender, the skin scraping needn’t be quite so deep, as these arachnids (mites are relatives of spiders) live close to the surface of the skin. However, “wide” is still de rigueur, as the numbers of scabies mites are typically low, and it is preferable to avoid a second skin scraping when possible.
Cheyletiella spp. can also be demonstrated with this technique.
HOW IS IT DONE?
The skin scraping process begins with hair removal, where indicated. Often the dermatologic condition itself has already achieved this step for us. A small amount of mineral oil is applied to the skin, and two drops of oil are spread on a microscope slide.
The area of suspect skin is squeezed, as D. canis mites can sometimes be brought to the surface this way. Still pinched, the skin is scraped with a scalpel blade* that has been dulled for the purpose. The resulting blood, skin cells and debris are mixed into one of the drops of mineral oil already on the microscope slide.
Most practitioners take a second scraping of the same location prior to heading to the microscope. The slide is examined under relatively low magnification, 10x. If mites are found, the clinician will make note of the life-cycle stages, such as larva, nymph and adult of D. canis. Finding earlier stages than adults indicates a more-active process, which may require more aggressive and longer treatment.
The resulting “wound” is similar to scraping one’s elbow on the sidewalk, and heals very rapidly. In our practice, we dispense an ointment that speeds healing and increases comfort level.
*I once attended a dermatology lecture at which the professor mentioned he calls his favorite skin-scraping scalpel blade “Excalibur.”