Demodectic mange, or "Red Mange" is a dermatologic skin disorder in which the normal demodectic mites are uninhibited and create multifocal skin lesions. This specific mite normally resides on/in the skin of healthy dogs, cats, and even humans! It is proposed that puppies who develop Demodectic mange have a genetic predisposition to developing the mange. If an adult dog develops this mange, it is speculated that either it is a reoccurrence of mange (if they had it as a puppy) or a condition in which the immune system is weakened which normal keeps these mites in check. Those possible conditions are hypothyroidism, stress, Cushing's disease, kidney or liver dysfunction, or other conditions. As this is considered a heritable trait, pets with this condition should be spayed or neutered.
The clinical signs of Demodectic mange are hair loss, crusting and scaling (particularly around the eyes and ears), potential itching, and a skin odor. Demodex should always be considered as a possible differential for any puppy with hair loss.
Diagnosis involves a thorough history and physical examination along with a skin scraping. Unfortunately the skin scrape is not highly sensitive meaning that the mites can be difficult to locate. However once mites are positively identified, therapy can be instituted.
Therapy involves providing a medicine, commonly ivermectin, to the dog once a day for at least 1-2 months. Collie breeds and collie crosses should use a product such as milbemycin as some collies have a predisposition to ivermectin toxicity. Secondary bacterial skin infections are very common and should be treated with appropriate antibiotics. Patients should be skin scraped monthly until negative results occur. Medicine should continue one month beyond a negative skin scraping. The length of therapy can vary greatly from pet to pet. Some animals only require 1 month of therapy and others may require several months to a year.
This condition cannot be cured in every case, but it can be successfully managed. It is possible and even likely that this condition will manifest itself years later, especially if another illness or stressful event occurs.