Introduction
Demodectic mange (Demodecosis) is caused by an
external parasite that is also present in low numbers on healthy
animals, including people. Whether or not a pet shows symptoms of
this disease depends primarily on their immune status. Since there is
no easy test to determine immune status, it is impossible to predict
which pets will get this disease, or how well a pet will heal if it
shows symptoms of demodex.
It is important to note that the diagnosis of
this skin condition, like most skin conditions, cannot be made just
by looking at a pet. Diagnostic tests are mandatory to arrive at a
correct diagnosis and achieve a satisfactory outcome to therapy.
Stating that an animal looks "mangey" is not the same thing as making
a positive diagnosis of mange. Pets that have Ringworm
or Sarcoptic
mange can look like they have
demodex.
Cause
Demodectic mange is caused by a mite, a
microscopic ectoparasite that infects the hair follicles. Most pups
pick up these mites from their mother when they are nursing, and do
not normally cause any problems. It is those pets that have an
inadequate immune system that develop this disease.
The parasite is cigar shaped and
has several pairs of legs. It is only visible under a microscope.
This is a picture of one that is laying on its back, its legs are
towards the right, and its mouth is at the far right.
There are underlying causes that can weaken the
immune system and make a pet more susceptible to this disease. These
include the chronic use of cortisone, Cushing's
disease, heartworm, cancer, and hypothyroidism.
Adult dogs that have demodex take longer to treat than young
dogs.
Symptoms
One of the most common symptoms of this disease is
small patches of hair loss (alopecia), towards the front of the body
initially, with the ability to affect the whole body. When it is
present in adult dogs it commonly affects the feet.
If a pet has only a few small patches of alopecia
the disease is classified as localized. If it has spread throughout
the body it is classified as generalized. Most pets that have
demodectic mange are young, which is a big aid in the
diagnostic
process.
The patch
of hair missing on this pups face is caused by Demodex, and
is an example of the localized
classification.
This is
an example of generalized demodecosis on the chest and front
legs. This is a serious condition and carries a guarded
prognosis.
Diagnosis
The primary way to diagnose demodectic mange is to do a skin
scraping where the patches of alopecia occur. The
fortunate thing about demodex is the ease of diagnosis in most dogs (Shar Pei's
can be an exception). In most cases the mites are easy to find under the microscope,
and if your pet is diagnosed as having this disease, one of our staff members
will show them to you. A positive skin scraping of large numbers of demodex
mites, along with alopecia (remember demodex is naturally found in the skin
also), is verification of demodectic mange and necessitates treatment.
Treatment
We are fortunate to have several medications at
our disposal to treat demodecosis. Unfortunately, one of the most
common medications called Mitaban, is no longer available. These
medications have proven to be highly effective, and have saved many
pets from suffering, and even euthanasia. Sometimes the most we can
hope for is to control the problem, not cure it. Treatment duration
needs to based on skin scrapings, not just the appearance of the
skin. a skin that looks like it is healed can still harbor demodex
mites. This is especially true for adult dogs with feet
lesions.
Unfortunately, due to the fact that the immune
system is paramount in whether or not your pet gets this disease, no
guarantee can be made that these medications will work. No matter
which form of demodex is treated, several ancillary issues need to be
addressed. Your pet needs to be on optimum nutrition, stay current on
vaccines, and be free of internal
parasites (worms). Like any disease
process, the psychological needs of your pet need to be met, which
includes plenty of exercise, TLC, and access to fresh water at all
times. Other skin conditions like allergies can occur simultaneously,
and need to be treated also.
1. Localized Treatment
Bathing with an antibacterial shampoo is the first
step in therapy. This loosens up scales, removes oily discharges, and
decreases the secondary bacterial infection that is usually present.
Localized demodex can be treated with a medication
called Goodwinol. It is a creme that is rubbed into the areas of
alopecia once daily. This rubbing initially causes more hair to fall
out, but within 1-3 weeks the problem usually goes away. If more
areas of alopecia appear during this time they should be treated with
Goodwinol and brought to the attention of one of our doctors during
recheck exams.
Another treatment for localized demodex involves the use of
Mitaban mixed into olive oil. This mixture is applied on the areas of hair loss
daily. It is possible for localized demodex to progress to generalized demodex
even if it is treated. Localized demodex might even resolve without any treatment.
2. Generalized Treatment
Generalized demodex is treated with a combination
of medications and modalities. It is important to understand that
treatment may take 2-3 months to be effective. The hair is usually
clipped to allow the topical medication easy access to the skin,
which makes it substantially more effective. Secondary pyoderma (skin
infection) is usually present also, so your pet is put on oral
antibiotics for several weeks to months.
The main drug used to treat
generalized demodex is called Mitaban. Unfortunately, Upjohn no
longer makes it, so we have to use substitutes. Mitaban has to be
used precisely by label instructions. Since it is difficult for
people to do this properly in their homes, we treat most pets in
our hospital. Pets are dipped once per week, in between these dips
your pet should not be bathed. We continue dipping until
successive skin scrapings are negative for the
mites.
If Mitaban does not work there are other
medications that are used with varying success to cure the problem.
These include oral Ivermectin and Milbemycin (Interceptor). Side
effects like excess salivation, incoordination, even coma and death
are possible, so they must be used judisciously. They should not be
given to Collies, Shelties, australian shepherds, or dogs that are
positive for heartworm. There can be no guarantee that they will
work, especially in a disease that is so closely associated with the
immune system. Spaying infected females is helpful.
Prevention
Pets that have this disease should not be bred.
Otherwise, it is difficult to predict just what pets will get this
problem.
Return to top
of page
|
