Canine Demodectic - (Demodex) Red Mange

Demodectic mange, sometimes just called "demodex," is caused by the demodectic mite, a parasite which lives in the hair follicles of affected dogs. 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. This occurs primarily in dogs less than 12-18 months of age. In most cases, as a dog matures, the immune system also matures and the condition improves or just disappears. Adult dogs that have the disease usually have defective immune systems.

Since the mite is found on virtually all dogs it is classed as contagtious. However, exposure of a normal dog to one with demodectic mange is not contagtious.

Development of the immune system is under genetic control. An affected dog usually comes from a litter containing other affected puppies. Guardians of littermates should be put on the alert to watch for it.

Surprisingly, a dog with demodectic mange does not itch severely, even though he 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."

The localized form is usually treated with topical medication.

A vet will advise that the generalized form requires shampoo therapy and a special dip or oral medication. In my opinion this can be ineffective and time consuming, secondary skin infections may also represent a complicating factor requiring antibiotic therapy. Dogs with skin infections have very red, inflamed skin. This is the source of the term "red mange."

Ivermectin is a drug that is used for prevention of heartworms. It is also used for certain parasites on cattle. The cattle preparation  can be used orally for demodectic mange and is less expensive to use than some of the more topical products a vet will prescribe.

However, it is a very strong drug that can cause severe side-effects, including death, if it is not dosed properly. It is not approved for use in dogs, so veterinarians are reluctant to prescribe it unless  you are willing to accept liability for adverse effects.

Regardless of the treatment if the immune system is defective, neither the mites nor the infection may respond to treatment.

Because the immune system does not mature until 12-18 months of age, a dog with demodectic mange may have relapses until that age. It is important for retreatment to begin promptly to minimize the possibility of developing uncontrollable problems.

Demodectic mange may also occur in very old dogs because function of the immune system often declines with age.

Dogs who have immune suppression due to illness or medication are also candidates for demodectic mange.

The dip commonly prescriped for washing contains the insecticide amitraz. Its use requires some caution because it is a strong insecticide that can have some side-effects to your dog and to you if it is not used properly. Your dog may experience vomiting and sedation for 24-36 hours following each application. If so, those problems will usually be self-limiting. If this occurs, the dip should be diluted with 25% more water the next time it is used. Since each dipping results in the development of tolerance to the dip, your dog is less likely to have side-effects with each subsequent treatment. Your dog should be dipped three times at seven day intervals, then examined by your vet for the presence of live mites or mite eggs. Further treatment will be determined by the results. If you do the dipping yourself, be sure to wear rubber gloves to prevent getting it on your hands.

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