Canine Demodectic Mange

Demodectic mange is caused by a mite that lives in the hair follicles of affected dogs. The mite is microscopic, eight legged, and cigar shaped. They are actually a normal inhabitant of the canine skin. In a healthy animal they cause no harm. In young animals, or animals with a weak immune system the mites are able to freely proliferate and cause a dermatitis. In severe cases the mites may spread over the animals entire body and cause hair loss, irritation and predispose to a secondary bacterial skin infection. The immune system of healthy dogs is able to keep the mite population under control. For this reason, demodectes is not considered to be contagious. Dogs with demodectes may have a genetic problem causing them to have a weak immune system. Because it is a genetic problem these dogs should not be bred.

What do the mites do to the dog?

Usually the dog starts loosing hair on the head around the eyes. There may be other areas of the body affected. There is not much itching associated with the mite infestation. When there are only a few patches of hair lost, it is termed localized demodectic mange. If the disease spreads over the entire body, it is called generalized demodectic mange.

How do I know if my dog has demodectic mange?

The diagnosis needs to be made by your veterinarian. After a thorough examination and discussion of the dogs history of skin problems your veterinarian may perform several skin scrapings. First, a few drops of mineral oil are placed on the skin adjacent to a suspicious area. Next, the skin is pinched to express any potential mites from the follicles and a scalpel blade is used to scrape the top layers of the epidermis away. The sample is placed on a slide and examined using a microscope. The veterinarian or veterinary technician examines the slide for the presence of the cigar shaped demodectes mites. Several scrapings may be necessary to find the mites. Occasionally the mites are not found but the veterinarian will recommend treatment anyway based on the history and other signs that support the diagnosis.

Can demodectic mange be treated?

Yes, the localized form is usually treated with a topical medication. The generalized form requires more aggressive treatment.Shampooing with a medicated shampoo helps to open the hair follicles prior to applying a dip. Some dogs need to be treated in the veterinary hospital. Other cases can be treated at home. Your veterinarian can recommend what is best for your pet. If there is a secondary skin infection your veterinarian will prescribe antibiotics. The treatment may take several months to complete. Your veterinarian may want to periodically check skin scrapings to monitor the progress.

Can my dog get it again?

Since the immune system does not fully develop until 12-18 months of age, a dog with demodectic mange may have relapses. If this happens it is important to begin retreatment promptly. Demodectic mange may also occur in old dogs because function of the immune system often declines with age. Dogs who have immune suppression due to illness or medication may also develop demodectic mange. 

by William M. Fraser, D.V.M.

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