What is Mange?

Mange is a term often misused by pet owners to describe any itchy skin condition, especially the ‘mangy’ appearance of a dog with flea allergy dermatitis. However, true mange is a condition caused by a mite that irritates the skin and causes hair loss.

The Demodex mite can cause a skin disease known as Demodectic mange or Demodicosis that includes hair loss, especially around the face, and the development of secondary infections. More rarely, the Sarcoptes mite can cause Sarcoptic mange.

What is demodicosis?

Demodicosis is an inflammatory, parasitic skin disease that is caused by a large population of mites, which lives in the hair follicles of dogs. Normally the mite, known as Demodex canis, is present in almost all dogs. However, an inflammatory reaction develops when the population of mites becomes too large for the immune system to regulate.

What causes demodicosis?

The exact cause of demodicosis is unknown. It is thought that the increase in mite population may result from a genetic or immune system disorder that allows the mites to multiply out of control. Two forms of demodicosis affect dogs. Young dogs, less than one year old, sometimes develop demodicosis before their immune system fully matures. Most show only small patches of hair loss, commonly on the face or legs. This form, called ‘localised’ demodicosis, often resolves without treatment (90% of cases). A small percentage of these cases will progress to the ‘generalised’ form.

Generalised demodicosis is a severe disease affecting many areas of the skin. In adult dogs, generalised demodicosis is often associated with cancer, an immunosuppressive disorder, or other internal disease. In juvenile dogs with generalised demodicosis an inherited immunological disorder is suspected, in which case it is a good idea to spay or neuter affected dogs.

What are the signs of demodicosis?

Localised demodicosis is characterised by patches of mild scaling and redness, primarily located on the face (around the eyes and ears). These patches also may be found infrequently on the limbs and trunk region. Generalised demodicosis is characterised by widespread redness, scaly skin, and hair loss covering the entire body. The rupture of hair follicles, which are distended with mites, predisposes the dog to the development of secondary bacterial skin infections. As the condition progresses, the skin becomes extremely inflamed, and fluid may ooze from the damaged regions.

How is demodicosis diagnosed?

Demodicosis is diagnosed by medical history and physical examination. Skin scrapings are taken from the dog to look for mites, eggs and larval forms in high numbers under a microscope. The skin scraping must be deep to be diagnostic and blood may be produced at the scrape site during or after the sample is taken. In animals with chronic demodicosis, a skin biopsy (surgical removal and microscopic examination of a sample of skin) may be required to identify the mites.

How is demodicosis treated?

Treatment for localised demodicosis often is not required since the disease is thought to resolve spontaneously in most cases (approximately 90%).

However, long-term treatment is required for generalised demodicosis. In most animals with generalised demodicosis, the disease is controlled rather than cured. Generalised demodicosis is a frustrating disease for the pet owner and veterinarian. Repeat applications of specialised shampoos, antiparasitic dips, topical treatments or oral administration of antiparasitic compounds are required. Examination of multiple skin scrapings should be performed at regular intervals to monitor response to treatment. Expect 8 to 12 weeks of treatment or more to control the condition.

What is the prognosis for dogs with demodicosis?

The prognosis for dogs with demodicosis varies. Generally the prognosis for dogs with localised demodicosis is good. The prognosis for generalised demodicosis depends on the underlying disease, the genetic constitution of the affected dog, and the immune status of the dog. In some adult dogs, demodicosis may not respond to treatment.