Third Street Veterinary Hospital, PC
McMinnville, Oregon 97128
Office phone: (503) 472-9418
Mange
is a parasitic skin disease caused by microscopic mites. Two different types of
mange mites are significant in dogs.
One type lives just under the surface of the skin, while the other type
resides in the hair follicles. Although
both types of mites share some 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.
Demodectic
mange, sometimes just called "demodex," is the most common form of
mange in dogs. It 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.
Contributing Factors
A
dog with demodectic mange usually comes from a litter containing other affected
puppies. This is because development of
the immune system is under genetic control.
Owners of littermates should be put on the alert to watch for it. Because the disease is due to a genetic
defect, affected dogs should not be bred.
Also, parents of the affected dog should not be bred again.
Prevalence
Demodectic
mange is a common parasitic skin disease of dogs. It is primarily seen in dogs less than one year of age.
Causes/Transmission
Demodectic
mange most often occurs when a dog has an immature immune system, allowing the
mites to grow rapidly. Consequently,
this disease occurs primarily in dogs less than 12-18 months of age. In most cases, the immune system matures as
a dog grows. When we see the disease in
adult dogs, we can usually make the assumption that the dog has a defective
immune systems.
Since
the mite is found on virtually all dogs, exposure of a normal dog to one with
demodectic mange is not dangerous. The other type of mange, called sarcoptic
mange, is highly contagious between dogs.
Clinical Signs
Surprisingly,
a dog with demodectic mange does not itch severely, even though it loses hair
in patches. Areas of bare skin will be
seen. 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.
Diagnosis
Diagnosis
is made by a deep skin scraping that is examined under the microscope. Usually, large numbers of mites are found.
Treatment
The
localized form is usually treated with topical medication. The generalized form requires shampoo
therapy and a special dip or oral medication.
Shampooing with special cleansing shampoos helps to flush out the hair
follicles prior to dipping. Dipping is described
below.
For
dogs with generalized demodectic mange, secondary skin infections may 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."
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.
Prognosis
Treatment
of the localized form is generally successful.
Treatment of the generalized form is also usually successful. However, if the immune system is defective,
neither the mites nor the infection may respond to treatment.
Transmission to Humans
Canine
demodectic mange is not contagious to humans.
Prevention
The
dip commonly used for demodectic mange 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 3
times at 7 day intervals, then examined 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.
Instructions for treatment
of your dog are noted:
1)
____ Apply the dispensed ointment to
the areas of hair loss. Do not get it
in your dog's eyes. Apply it once daily
for 10-14 days. At that time, the dog
should be reexamined to decide if further treatment is needed.
2)
____ Give ____ ml of the oral insecticide once daily. This needs to be continued for 2-4 weeks past apparent
recovery.
3)
____ Bathe your dog with the recommended medicated shampoo, then rinse the
shampoo. Next, slowly pour amitraz dip
over the entire body. This should be
done 3 times at 7 day intervals.
Mix one bottle of amitraz with two
gallons of water. Once the bottle is
opened, amitraz deteriorates rapidly, even if not diluted. Therefore, unused dip cannot be used
later. Wear rubber gloves while
handling the dip; wash your hands and arms with soap and water after treatment
of your dog. Do not rinse the dip off
your dog; allow it to air dry. A hair
dryer may be used if the temperature is cool.
If vomiting or sedation occurs
within 24-36 hours after dipping, dilute the dip with 25% more water (2.5
gallons instead of 2 the next time).
These side effects should resolve without treatment.
4)
____ After the third dipping, we should examine your dog for the presence of
live mites or mite eggs. The need for
further treatment will be discussed.
Some dogs require up to 12-15 dippings before no live mites or eggs are
present. We should examine your dog
after every third dip.
5)
____ Administer the dispensed antibiotics according to the label. When the prescription is completed, your dog
should be examined to determine if further antibiotic treatment is needed.
6)
____ For lesions on the feet, mix l cc of amitraz dip (straight from the
bottle) with 1 oz of propylene glycol.
Apply this mixture to the feet 2-3 times per week. It must be mixed fresh each week. If the feet are affected, they will often be
the last part of the body to heal. Let us know if you cannot find the propylene
glycol at your pharmacy. Remember to
wear gloves when applying dip to the dog's feet.
7)
____ At the first sign of recurrence of this disease, we should see your dog
again to determine what treatment is needed.
This may happen until it is 12-18 months old.
8)
____ We will apply the amitraz dip to your dog. Return the dog in ____ days for the next treatment.
9) ____ Return your dog in ____ days to have it
examined for the presence of mites.