Dogs infested with sarcoptic mites will present to the veterinarian with a history of the sudden onset of intense itchiness (pruritis), and probably also with red, raw skin sores and thick crusted areas caused by self-trauma from the dog’s effort to alleviate the itchiness. The most common method of diagnosing Sarcoptes scabiei infection is by treating the dog with a topical medication that specifically targets and kills these mites. It is called a “scabicidal” medication, and this process is called “diagnosis by treatment” or “trial therapy.” Other tests can be conducted to identify the mites, but those tests are uncommonly done in routine veterinary practices. The physical signs that the dog presents with, together with the results of treating the dog with scabicidal medications, are the best way to definitively diagnose and to treat this disorder.
Skin scrapings and examination of fecal samples can also be useful in the diagnosis of sarcoptic mange, although they are not particularly reliable. They certainly are not as helpful as the response to scabicidal treatment. In Europe, there is an enzyme-linked immunosorbent assay (ELISA) available to test for sarcoptic mite antigen. It is not yet widely available in North America. Another way that sarcoptes mange can be diagnosed is by rubbing the edge of the dog’s ear and watching for a reflex scratching action in one of its hind legs. This is an extremely common reaction in dogs with sarcoptic mange. Occasionally, the mites or their eggs can be identified in a fecal sample through a fairly simple procedure called a fecal floatation.
Once sarcoptic mange is diagnosed and treatment is begun, it can take up to two weeks to see any significant reduction in the itchiness suffered by the affected animal. It may take 3 months or more for a complete resolution of the condition to occur.