It is found mostly in young dogs, who acquire it from their mothers. The mites are transferred from mother to pup during the first few days of life. An older pup cannot pick up Demodex mites, and puppies raised by hand will not acquire them either. It is not transmitted to humans or spread among adult dogs. The mites produce a substance that can lower a dog's natural resistance to them, and in this way they multiply.
Demodectic mange is more common in oily-skinned shorthairs and pubescent dogs.
Predisposition to demodicosis seems to be hereditary. Localized demodectic mange can last for up to a year. The first sign is a small, hairless patch near the eye, chin, or forelegs that doesn't itch much. For unknown reasons, in a small number of dogs it will continue to spread. An adult dog may also occasionally develop localized demodicosis.