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Demodectic
Mange
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. It is very important to remember that a pet with an optimal
healthy immune system is much less prone than
pets with compromised immune systems.
Article courtesy of LBAH
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