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What causes demodectic mange?
Demodectic mange, sometimes just called “demodex”, 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 8 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 which 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 is not dangerous
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 litter mates should be put on the alert to watch for it. Because the disease is often due to a genetic defect, affected dogs should not be bred. Also, parents of the affected dog should not be bred again.
Sometimes the disease can occur as a result of treatment of the dog with immunosuppressant drugs including corticosteroids.
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 localised demodectic mange. If the disease spreads to many areas of the skin, it becomes generalised demodectic mange.
How is demodectic mange treated?
Recently studies are showing the Bravecto and Nexgard, which are oral flea and tick reatments, have good activity against demodex, and are the currently recommended treatment.
Historically, we have used insecticide shampoos and medications, which potentially can cause toxicities
For dogs with generalised demodectic mange, secondary skin infections may represent a complicating factor requiring antibiotic therapy. Dogs with skin infections have very red, inflamed skin and these dogs are usually itchy.
What is the prognosis for my dog?
Treatment of the localised form is generally successful. Treatment of the generalised form is also usually successful. However, if the abnormality in the immune system is severe the dog may require regular treatment for the rest of its life.
Following successful treatment, is it likely to reoccur
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 minimise 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 special shampoo commonly used for demodectic mange can have side effects both to your dog and yourself if not properly used. If in doubt consult your Veterinary surgeon. After the treatment it will be necessary to examine your dog for the presence of live mites or mite eggs. Further treatment will be determined by the results.
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Dee Why Vet
Who We Are