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OVERVIEW
Demodecosis 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 make up of the skin and is normally present in small number. The mite resides in hair follicles and glands surrounding the follicles (sebaceous glands). Due to changes in either the genetic or immune system of the animal, the mite begins to proliferate and causes the clinical signs of the disease.
CANINE DEMODEX
Most cases in dogs occur at a young age. There are no sex or breed predilections. There are two forms of the disease. There is no sex or breed predilection. Transmission occurs by direct contact from the bitch to nursing neonates during the first two or three days of neonatal life. Puppies delivered by cesarean section and raised away from the infected carriers mother did not develop the 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 immunosuppression. The feeling is that there is a subnormal percentage of interlukin-2 receptors on certain blood cells called lymphocytes. In adult onset mange, owner must be warned of the possibility of a major internal illness or a malignant cancer.
Breeders must assume responsibility to remove carriers from their kennel (both parents and siblings) to reduce or eliminate the incidence of demodex. By following this culling program, some kennels have eliminated the disease from their line of breeding.
CLINICAL SIGNS
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 fore legs. Most cases heal with less then 10% progressing to generalized demodecosis.
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.
TREATMENT
Localized Demodex
If mild, the disease usually heals spontaneously. Topical treatment a diluted amitraz (3ml to 30 ml of mineral oil), or rotenone 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 Demodex
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.
Juvenile forms are treated by the following medications:
Amitraz (Mitaban-Upjohn) is the first line in the treatment. Dosage and regimen: use weekly to every other week. Apply a protective ophthalmic ointment to the eye. Wash the entire dog with an antibacterial shampoo, benzoyl peroxide, and gently towel dry the pet. Then apply the amitraz. Use either weekly or every other week. Mix ½ vial per gallon of water. Apply to the entire body. Wear protective gloves when applying. This medication may cause transitory sedation for 12-24 hours. We recommend keeping your pet confined during the day of treatment. Do not towel dry, but let your pet air-dry.
We also recommend use of an antibiotic to control secondary skin infections.
Continue treatment until two successive biweekly skin scrapings are negative for the mite.
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