Aussie Genetics Fact Sheet: Generalized Demodectic Mange by C.A. Sharp Demodectic mange is an auto-immune reaction to mites that naturally occur on skin. All dogs have the mites, not all dogs react. Veterinary opinion varies, but most seem to agree that if the disease occurs in a young animal and remains localized it is not hereditary. Localized demo will go away whether you treat it or not. Generalized demo starts like localized, but spreads across the body and must be controlled with medication. Not all dogs respond to medication and some will die of the disease. This type is hereditary, though the mode of inheritance is unknown. Dogs which have generalized demodectic mange should not be bred. If the a sire or dam produces it more than once, particularly with unrelated mates, the owner should seriously consider removing that animal from breeding. Siblings of a dog with generalized demo should not be bred back on their own pedigrees, nor should they be bred to mates from families where the disease has occurred.