Demodectic Mange in Dogs and Cats

Demodectic Mange is an inflammatory parasitic disease of dogs and rarely cats characterized by the presence of a high number of mites in the hair follicles, which often leads to inflammation and infection. The mite, demodex, is part of the normal biological composition of the skin and is normally present in small numbers. The mites reside in hair follicles and glands surrounding the follicles (sebaceous glands). Due to changes in either the genetic or immune system of the animal, the mites begin to proliferate and cause clinical signs of the disease.

Most cases in dogs occur at a young age. There are no sex or breed predilections. Transmission usually occurs by direct contact from the mother to nursing neonates during the first two or three days of neonatal life, and these mites do not normally cause disease. It is those pets that have an inadequate immune system that develop this disease. Adult onset demodex may be due to a decreased resistance to the mite as a result of a compromise of the immune system. It is speculated that some internal disease may cause immuno-suppression.

One of the most common symptoms of this disease is small patches of hair loss (alopecia), towards the front of the body initially, with the ability to affect the whole body. When it is present in adult dogs it commonly affects the feet. If a pet has only a few small patches of alopecia the disease is classified as localized. If it has spread throughout the body it is classified as generalized.

Localized Demodex
Signs are usually mild and one to several patches of hair loss and inflammation are noted. The most common sites are the face and forelegs. Most cases heal, with less than 10% progressing to generalized demodecosis. If mild, the disease usually heals spontaneously. Topical treatment using diluted Amitraz dips may be used. After four weeks of treatment the numbers of mites should be greatly reduced. If more mites are observed, then the condition should be treated as a generalized form.

Generalized Demodecosis

There are many lesions. These are reddened patches and may be itchy. Secondary bacterial infections occur as the numbers of mites proliferate. Differential diagnosis includes primary bacterial infection, fungal infections, contact dermatitis, and immune mediated skin diseases. Adult onset forms may become a management problem due to an underlying cause. Many of these animals may be medically controlled rather than cured. The prognosis is dependent upon the genetic, immunologic, and underlying disease.

Demodectic Pododermatitis

Demodectic Pododermatitis
This condition represents demodectic mange confined to the paws. Bacterial infections usually accompany this condition. Often as generalized demodicosis is treated, the foot is the last stronghold of the mite. Old English Sheepdogs and Shar-peis tend to get severe forms of this condition.

The primary way to diagnose demodectic mange is to do a skin scraping where the patches of alopecia occur. The fortunate thing about demodex is the ease of diagnosis in most dogs. In most cases the mites are easy to find under the microscope. A positive skin scraping of large numbers of demodex mites, along with alopecia is verification of demodectic mange and necessitates treatment.

Ivermectin is a broad spectrum anti-parasite medication generally used for food animals and horses. It is licensed for use in dogs and cats as a heartworm preventive and as a topical ear mite therapy at this time. Ivermectin is inexpensive relative to Milbemycin and involves no labor intensive bathing.

Mitaban is a topical demodex treatment. Treatment of generalized demodex is often done using Mitaban dips. It is important to understand that treatment may take 2-3 months to be effective. Secondary pyoderma (skin infection) is usually also present, therefore your pet may be placed on oral antibiotics for several weeks to months.

The hair is usually clipped to allow the topical medication easy access to the skin, which makes it substantially more effective. The dog is washed with an antibacterial shampoo before the Amitraz dip. This helps treat secondary skin infections, removes oily discharges & scales and opens the hair follicles so the dip can reach the mites. The shampoo must stay on the pet at least 10 minutes before rinsing to be effective. Next the Amitraz dip is applied to the entire coat. The dip should dry on the dog’s fur and should not be rinsed off. This is done once a week or every other week at a veterinary clinic using protective equipment. This medication may cause transitory sedation in pets for 12-24 hours. We recommend keeping your pet confined during the day of treatment. Treatment is continued until 2 consecutive scrapings are negative. Dipping/bathing is discontinued and the pet is rechecked in one month. Dipping/bathing are reinstituted if mites are found again.

Interceptor (active ingredient: Milbemycin oxime) is normally marketed as a monthly heartworm preventive. When it is used on a daily basis, it is effective against generalized demodicosis. Therefore, medicated dips are not needed. However, this treatment is expensive and must continue for 3 months to be effective.

The younger the dog, the better the chance of resolving demodectic mange. In many cases of adult-onset demodicosis, the disease is controlled by dips and baths, but treatment is not always effective. Some cases cannot be successfully controlled. Relapse is always a possibility with generalized demodicosis, but most dogs that relapse do so within a 6-12 month period from the time they appear to have achieved cure.

Physiological stress is an important factor determining the degree of severity of demodectic mange.

1. Females should be spayed as soon as the disease is controlled. Coming into heat, hormone fluctuations, and pregnancy are very stressful. Also, predisposition to demodicosis is hereditary and should not be passed on.
2. The dog should be fed a high quality dog food so as to avoid any nutritionally related problems.
3. Keep the pet parasite-free. Internal parasites are intestinal irritants and fleas may exacerbate the itchiness and skin infection.
4. Keep the pet's vaccinations current.
5. Skin infections are usually present in these cases and antibiotics will likely be necessary. It is very important that cortisone type medications such as prednisone NOT be used in these cases as they will tip the immune balance in favor of the mite.

This is a rare disease is unusually localized. The mite is a different species then the canine form. It usually affects the eyelids, head, neck, ears, and the area in front of the ears. It is usually self-limiting. The generalized form is extremely rare. Localized treatment with Rotenone (Goodwinol) is usually successful. It is a creme that is rubbed into the areas of alopecia once daily. This rubbing initially causes more hair to fall out, but within 1-3 weeks the alopecia usually decreases.

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