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Dog: Demodicosis

General information

Other common/scientific names: mange, demodex mange, red mange, Demodex mites

Ectoparasites are parasites that live on the exterior or surface of an animal. The common canine ectoparasites include fleas, ticks, lice and mites. They can transmit various diseases and cause hypersensitivity and skin disorders in animals. Ectoparasites can also cause life-threatening anemia in young and debilitated animals. Some ectoparasites (mites and lice) spend their entire life on the dog while other ectoparasites (fleas and ticks) spend part of their life cycle in the environment. Fleas, ticks and mites are not species specific, meaning they can infest animals of different species, i.e., canine mites can cause symptoms on humans. Lice on the other hand only infest a specific species, i.e., dog lice only infest dogs.

Demodex mites are ectoparasites which live and feed in the hair follicles and oil glands of the skin. These skin mites are microscopic, unseen by the naked eye. Many dogs have small numbers of Demodex mites in their skin without causing any problems or clinical signs.

Causes

Demodicosis or demodectic mange is caused by a small skin mite called Demodex canis. Dogs show clinical signs of demodectic mange because their immune systems do not respond to the mites appropriately. This can be seen in young dogs with underdeveloped immune systems or older dogs which have a weakened immune system due to chronic disease such as cancer, liver or kidney disease or diabetes mellitus. Some dogs have a genetic predisposition to developing demodicosis which is hereditary.

Infection

Demodectic mange is not considered a contagious disease. However, there are some circumstances where mites could be spread from one dog to another. Demodex mites can be transferred from the mother to the newborn pup through normal cuddling during the first few days of life. If the pup has a normal, healthy immune system, the pup should be able to either eliminate the mites or live without developing any symptoms. Because of this, dogs showing signs of demodicosis do not need to be isolated from other dogs. However, a weakened immune system or stress to the immune system can allow the mites to proliferate causing a serious skin disease.

Cardinal symptom

Hair loss

Symptoms

There are two forms of demodicosis: localized and generalized. Localized demodicosis usually occurs in dogs less than two years of age who show signs of small, isolated bald patches on the face and neck. For the most part, the skin is not inflamed and only mildly pruritic (itchy).

In contrast, the generalized form affects the entire body with large patches of hair loss and reddened, inflamed skin with scabs and crusts. Young dogs and adult dogs can both be affected with the generalized form which can result in secondary bacterial infections, enlarged lymph nodes, lethargy, fever and cellulitis. Demodectic pododermatitis is a form of generalized demodicosis confined to the paws. The skin around the toes becomes infected, swollen and painful. Dogs with generalized demodicosis may shows signs of an underlying disease affecting their immune system such as cancer, liver or kidney disease or diabetes mellitus.

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Abb. GFTF0QWU: Generalized Demodicosis in a Boxer.
This is a picture of generalized demodicosis. Note the areas of skin loss over the entire body with scabs and crusts.

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Abb. GFTF2A0K: Generalized Demodicosis of the paw.
This picture shows a pododermatitis with red, inflamed skin of the foot.

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Abb. GFTF42QJ: Generalized Demodicosis.
This is a picture of generalized demodicosis. Note the areas of skin loss over the entire body with scabs and crusts.

Diagnosis

Diagnosis of canine demodicosis is made by performing a skin scraping on the affected areas and identifying the Demodex mite under the microscope. The Demodex mite is an elongated, cigar-shaped mite with eight legs. Because the mite can be found in normal, asymptomatic dogs, a diagnosis of demodicosis should only be made if several adults mites or young mites are found.

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Abb. GFTF89W7: Demodex canis mite seen under a microscope.

In the case of generalized demodicosis, more diagnostic tests may be required to identify the underlying condition. It is vital that the underlying disease be diagnosed and treated to prevent recurrence of demodectic mange.

Treatment

Treatment of demodectic mange depends on the patient’s age and the severity of the disease.

Treatments include topical medications, whole body dips and oral antiparasitics. Young dogs with small areas of localized hair loss generally do not need aggressive treatment. These dogs can be treated with a topical cream or gel. One option is to not treat localized demodicosis in young dogs. These dogs are then closely observed for signs of generalized demodicosis. If the condition worsens or does not resolve, more aggressive treatment of whole body dips or oral antiparasitics may be needed.

Dogs with generalized demodicosis require intensive treatment with dips and/or oral medications. Some dogs are very sensitive to these parasitical dips and must be monitored at a veterinary clinic. A commonly used dip for treatment of demodicosis is no longer available in United States. Some oral medications are extra-label meaning they are used in a manner for which the medication is not FDA approved. Because of this, these medications should only be administered under the guidance of a veterinarian. Many dogs with generalized demodicosis also need concurrent antibiotic or antifungal therapy to treat secondary skin infections. Treatment of the underlying condition must also be instituted. Skin scrapings should be performed every 2-4 weeks to monitor the response to treatment.

Prognosis

Prognosis is good for localized demodicosis in young dogs. And, many young dogs with generalized demodicosis can completely recover. However, older dogs with adult onset demodicosis may need regular treatments for the rest of their lives to control the disease. Severe cases with underlying systemic disease may have a poor prognosis and never be controlled.

Prevention

All dogs with generalized demodicosis should be neutered to prevent passing the predisposition to their offspring. Neutering also decreases the stress of breeding and pregnancy which can trigger clinical signs of demodicosis. If the condition resolves without treatment, the young dog may not have the genetic disposition and could possibly be used for breeding. However, if there is any doubt, the dog should be neutered to eliminate the passing of this genetic trait.

Tips

Dogs with generalized demodicosis should fed a high quality dog food and routinely dewormed and vaccinated. Maintaining a healthy pet decreases the chance of recurrence of demodicosis.

Update version: 4/24/2014, © Copyright by www.enpevet.de
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