Demodectic mange is caused by a
tiny mite, Demodex canis, too small to be seen with the naked eye. Nearly all
dogs acquire mange mites from their mother
during the first few days of life. These mites are considered normal skin fauna when present in
small numbers. They produce disease only when an abnormal immune system allows
their numbers to get out of control. This occurs primarily in puppies and in
adult dogs with lowered immunity. A high incidence of mange in certain
bloodlines suggests that some purebred dogs are born with an inherited immune
Demodectic mange occurs in localized and generalized forms. The diagnosis is
made by taking multiple skin scrapings and looking for the mites. Demodectic
mites are usually easy to find.
This disease occurs in dogs under 1 year of age. The appearance of the skin
is similar to that of ringworm. The principal sign is
thinning hair around the eyelids, lips, and corners of
the mouth, and occasionally on the trunk, the legs, and the feet. The thinning
progresses to patches of ragged hair loss about 1 inch (2.5 cm)
in diameter. In some cases the skin becomes red, scaly, and infected.
Localized mange usually heals spontaneously in six to eight weeks, but may
wax and wane for several months. If more than five patches are present, the
disease could be progressing to the generalized form. This occurs in
approximately 10 percent of cases.
Treatment: A topical ointment containing either benzoyl peroxide gel (OxyDex
or Pyoben), or a mild topical preparation used to treat ear mites can be massaged into
affected areas once a day. This may shorten the course of the disease. The
medication should be rubbed with the lay of the hair to minimize further hair
loss. Treatment may cause the area to look worse for the first two to three
There is no evidence that treating localized mange prevents the disease from
becoming generalized. The dog should be checked again in four weeks.
Generalized Demodectic Mange
Dogs with the generalized disease develop patches of hair loss on the head,
legs, and trunk. These patches coalesce to form large areas of hair loss. The
hair follicles become plugged with mites and skin scales. The skin breaks down
to form sores, crusts, and draining tracts, presenting a most disabling
problem. Some cases are a continuation of localized mange; others develop
spontaneously in older dogs.
When generalized demodectic mange develops in dogs under 1 year of age,
there is a 30 to 50 percent chance that the puppy will recover spontaneously.
It is uncertain whether medical treatment accelerates this recovery.
In dogs older than 1 year, a spontaneous cure is unlikely but the outlook
for improvement with medical treatment has increased dramatically in recent
decades. Most dogs can be cured with intense therapy. Most of the remaining
cases can be controlled if the owner is willing to commit the necessary time