A skin scraping is indicated in any skin disorder, especially those involving:
- Alopecia or hair loss
- Pruritis or itchiness.
Once submitted to the laboratory by the vet, the hair/skin combination is treated with potassium hydroxide which clears the sample, making the detection of the dermatophyte spores and hyphae possible by light microscopy. Once the spores are seen invading the hair shaft, a diagnosis of ringworm can be made.If further identification is required, the dermatophyte can be cultured on specialised medium and classified according to both microscopic and macroscopic characteristics.
These can often be seen by the naked eye but need to be looked at under a low powered microscope for confirmation. They include fleas, lice, ticks and some mites e.g. Cheyletiella. Other skin parasites, such as Demodex and Sarcoptes are microscopic and often require multiple preparations and extensive screening for positive identification.
These may be seen as primary or secondary pathogens. Rainscald is caused by Dermatophilus congolensis, which in certain warm and wet conditions will rapidly multiply to cause a severe dermatitis. Alternatively, many skin commensals will take advantage of a breakdown in the skin barrier to produce a secondary infection. Thee can be detected by direct staining or culture.