Mange
- Demodectic in Dogs
Mange is a parasitic skin disease caused
by microscopic mites. Two different mange mites cause skin disease in dogs. One
lives just under the surface of the skin, while the other resides deep in the
hair follicles. Although both mites share similar characteristics, there are
also important differences. It is important not to confuse the two types of
mange because they have different causes, treatments, and prognoses.
What
causes demodectic mange?
Demodectic mange, sometimes just called "demodex"
or "red mange", is the most common form of mange in dogs. It is
caused by the Demodex canis, a parasite that lives in the hair follicles
of dogs. Under the microscope, this mite is shaped like a cigar with eight
legs.
"As long as the body's immune
system is functioning properly, these mites cause no harm. "
All normal dogs (and many humans)
have a few of these mites on their skin. As long as the body's immune system is
functioning properly, these mites cause no harm.
Demodectic mange most often occurs
when a dog has an immature immune system, allowing the number of skin mites to
increase rapidly. As a result, this disease occurs primarily in dogs less than
twelve to eighteen months of age. As the dog matures, its immune system also
matures. Adult dogs that have the disease usually have defective immune
systems. Demodectic mange may occur in older dogs because function of the
immune system often declines with age. Dogs who have immune suppression due to
illness or certain medications are also candidates for demodectic mange.
Is
demodectic mange contagious?
"Demodectic mange is not
contagious to other animals or humans."
No, demodectic mange is not
contagious to other animals or humans. Demodex mites are transmitted to
puppies from their mother during the first few days of life. Since the mite is
found on virtually all dogs, exposure of a normal dog to one with demodectic
mange is not dangerous.
If your dog is showing these
symptoms do not wait for the mange to spread. It's better to contact your Veterinarian.
Why
doesn't the immune system mature correctly in some dogs?
Development of the immune system is
under genetic or hereditary control. Thus, an affected dog often has
littermates that are also affected. Owners of littermates should be alerted to
watch for the development of mange in their puppies. Because the disease is due
to a genetic defect, affected dogs should not be bred, and the parents of the
affected dog should not be bred again.
What
does demodectic mange do to the dog?
Surprisingly, a dog with demodectic
mange usually does not itch severely, even though it loses hair in patches. The
hair loss usually begins on the face, especially around the eyes. When there
are only a few patches of hair loss, the condition is called localized
demodectic mange. If the disease spreads to many areas of the skin, it becomes generalized
demodectic mange.
How
is demodectic mange diagnosed?
"Your veterinarian will take
deep skin scrapings and examine them under the microscope to diagnose this
disease."
Your veterinarian will take deep
skin scrapings and examine them under the microscope to diagnose this disease.
The finding of larger than normal numbers of Demodex mites in skin scrapings
confirms the diagnosis. Occasionally, the disease will be diagnosed by means of
a skin biopsy in dogs that have chronic skin infections that have not responded
appropriately to treatment.
How
is demodectic mange treated?
The localized form is usually
treated with topical medication. The generalized form requires more aggressive
treatment using special shampoos and dips, along with oral medication.
Shampooing with special cleansing shampoos containing benzoyl peroxide helps to
flush out and open the hair follicles prior to dipping. A separate handout is
available to describe the dipping process. In some cases, especially dogs with
generalized demodectic mange, secondary skin infections complicate the
condition, requiring antibiotic therapy. Dogs with skin infections often have
very red, inflamed skin. This is the source of the term "red mange."
Are
there any problems with topical treatment?
The dip commonly used for demodectic
mange contains the insecticide amitraz. It must be used cautiously
because it is a strong insecticide that can cause side effects, both to your
dog and to you, if not used properly. Your dog may experience
vomiting and sedation for twenty-four to thirty-six hours following each
application. Most of these problems are self-limiting and resolve without
medical intervention. If your dog reacts in this manner, you should dilute the
next dip with 25% more water. Since most dogs develop tolerance to the dip as
they are repeated, your dog is less likely to have side effects with each
subsequent treatment. After receiving two to three dipping treatments at
seven-day intervals, skin scrapings should be repeated and examined for the
presence of live mites or mite eggs. The results of these skin scrapings will
determine whether further treatment is needed.
I
heard that there is a drug that can be given orally for demodectic mange. Is
that true?
Yes, under certain conditions.
Ivermectins are a class of drugs that are approved for prevention of
heartworm disease in dogs and cats. Milbemycin oxime, the active ingredient of
Interceptor® and Sentinel® heartworm preventives, may be used to treat
demodicosis in certain cases. Certain ivermectins are used to treat parasites
on cattle. In the past, the cattle preparation has been used orally for
demodectic mange in some dogs. However, it is a very strong drug that can cause
severe side-effects, including death, if it is not administered properly. It is
not approved for use in dogs, so we would only consider using it as long as you
are willing to accept liability for adverse effects. Veterinarians do not
generally recommend ivermectin usage in collies, Shetland sheepdogs, Australian
shepherds, old English sheepdogs, or any other herding breed.
What
is the prognosis for my dog?
Treatment of demodectic mange is
generally successful. However, if the immune system is defective, neither the
mites nor the infection may respond to treatment. With generalized demodicosis,
successful treatment may take a long time.
Following
successful treatment, is it likely to recur?
"It
is important to treat as soon as a relapse occurs to minimize the possibility
of developing uncontrollable problems."
Because the immune system does not
mature until twelve to eighteen months of age, a dog with demodectic mange may
have relapses until that age. It is important to treat as soon as a relapse
occurs to minimize the possibility of developing uncontrollable problems.
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This client information sheet is
based on material written by: Ernest Ward, DVM
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