Demodectic Mange

By November 8, 2016Pet Talk

Canine Demodectic Mange

Mange is a parasitic skin disease caused by microscopic mites.  Some mites live just under the surface of the skin, while mites reside in the hair follicles.  Although these mites share some similar characteristics, there are also important differences.  It is important not to confuse the different types of mange because they all have different causes, treatments, and prognoses.

What causes demodectic mange?

Demodectic mange, sometimes just called “demodex”, is the most common form of mange in dogs.  It is caused by the demodectic mange mite, a parasite which lives in the hair follicles of affected dogs.  Under the microscope, this mite appears shaped like an alligator with eight legs.  All dogs (and many humans) have a few of these mites on their skin.  As long as the body’s immune system is functioning, these mites cause no harm.

Demodectic mange most often occurs when a dog has an immature immune system, allowing the mites to grow rapidly.  Therefore, this disease occurs primarily in dogs less than 12-18 months of age.  In most cases, as a dog matures, the immune system also matures.  Adult dogs that have the disease usually have defective immune systems.

Does this mean that demodectic mange is NOT contagious?

Yes.  Since the mite is found on virtually all dogs, exposure of a normal dog to one with demodectic mange does not transmit the disease.

Why doesn’t the immune system mature correctly in some dogs?

Development of the immune system is under genetic control.  Thus, an affected dog usually comes from a litter containing other affected puppies.  Owners of littermates should be put on the alert to watch for it.  Because the disease is due to a genetic defect, affected dogs should not be bred.  Also, parents of the affected dog should not be bred again.

What does demodectic mange do to the dog?

Surprisingly, a dog with demodectic mange does not itch severely, even though it loses hair in patches.  Areas of bare skin will be seen.  The hair loss usually begins on the face, especially around the eyes.  When there are only a few patches of hair loss, it is termed localized demodectic mange.  If the disease spreads to many areas of the skin, it becomes generalized demodectic mange.

How is demodectic mange treated?

The localized form is usually treated with topical medication.  The generalized form requires shampoo therapy and a special dip or oral medication.  Shampooing with special cleansing shampoos helps to flush out the hair follicles prior to dipping.  Dipping is described below.  For dogs with generalized demodectic mange, secondary skin infections may represent a complicating factor requiring antibiotic therapy.  Dogs with skin infections have very red, inflamed skin.

I heard that there is a drug that can be given orally for demodectic mange?  Is that true?

Yes.  Ivermectin is a drug that is used for prevention of heartworms.  It is also used for certain parasites on cattle.  The cattle preparation has been used orally for demodectic mange in dogs.  In many dogs it is very successful and is less expensive to use than some of the newer topical products.

What is the prognosis for my dog?

Treatment of the localized form is generally successful.  Treatment of the generalized form is also usually successful.  However, if the immune system is defective, neither the mites nor the infection may respond to treatment.


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