Healthy Dogs

Demodectic Mange in Dogs

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 susceptibility.

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.

Localized Demodectic Mange

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 weeks.

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 and expense.