(SOMETIMES CALLED
"RED MANGE" OR “DEMODICOSIS”)
Demodectic
mange, also called "demodicosis," is caused by a microscopic mite of
the Demodex genus. Three species of Demodex mites
have been identified in dogs: Demodex canis, Demodex gatoi,
and Demodex injai. The most common mite of demodectic mange is Demodex
canis. All dogs raised normally by their mothers possess this mite
as mites are transferred from mother to pup via cuddling during the
first few days of life. Most dogs live in harmony with their
mites, never suffering any consequences from being
parasitized. If, however, conditions change to upset the natural
equilibrium (such as some kind of suppression of the dog's immune
system), the Demodex mites may "gain the upper hand." The mites
proliferate and can cause serious skin disease.
Demodectic
mange (unlike Sarcoptic mange) is not considered a contagious disease
and isolation of affected dogs is generally not considered
necessary. That said, there are some circumstances under which the
mites could spread from one dog to another.
Classically Demodex
mites have been felt to only be transferable from mother to newborn
pup. After the pup is a week or so old, it has developed enough
immunity so that infection is no longer possible. In other words, after
age one week or so, a dog will not longer accept new mites on its body.
Recently this
idea has been challenged as occasionally multiple unrelated dogs break
with demodicosis in the same household. It is not clear if some species
of Demodex are more contagious than others or if some contagion
is possible under certain circumstances. Current thinking is that mites
actually can be transferred from one dog to another but as long as the
dog is healthy, the mites simply add into the dog's natural mite
population and no skin disease results. Isolation of dogs with even the
most severe demodicosis is still felt to be unnecessary; though, in
rare circumstances contagion is possible. While there are still
assorted theories about dog to dog transmission of Demodex mites,
there is no question that mites cannot be transmitted to humans or to
cats.
- Mites live inside hair follicles -- a
difficult place for miticides (chemicals that kill mites) to reach.
- Mites are a normal residents of dog skin;
it is only in some individual dogs that mites cause problems.
Localized
demodicosis occurs as isolated scaly bald patches, usually on the dog's
face, creating a polka-dot appearance. Localized demodicosis is
considered a common puppyhood ailment and approximately 90% of cases
resolve with no treatment of any kind. This is quite a contrast to
generalized demodicosis as described below so it is important to be
able to distinguish localized from generalized disease. It seems like
this would be a simple task since localized demodicosis classically
involves several round facial bald spots and generalized demodicosis
involves a bald scaly entire dog; still, reality does not always fit
into neat categories in this way. Some guidelines used to
distinguish localized demodicosis include:
- Localized disease does not involve more
than two body regions. (One spot or two on the face and one spot or two
on a leg would still qualify as localized even though the spots are not
close together.)
- Localized disease involves no more than 4
spots total on the dog.
Treatment is
not necessary or recommended for localized demodicosis but there are
treatment options for people who simply cannot feel right about doing
nothing. Goodwinol ointment, an insecticide, may be used
daily to control localized demodicosis. Antibacterial gels
are also used against localized demodicosis and associated skin
infections. It is important to note that rubbing a creme or ointment on
a demodicosis lesion can cause reddening of the lesion making it appear
to get worse. It is also possible for rubbing the medication on the
area to break off the weaker hairs at the margin of the lesion causing
the lesion to appear to get bigger. Neither of these situations truly
represents exacerbation of the disease.
Resolution of
a localized demodicosis lesion should be at least partially apparent
after one month though total resolution can take up to three months.
Approximately
10% of localized demodicosis cases will progress to generalized
demodicosis. Enlarged lymph nodes are a bad sign -- often
foretelling generalized mange.
Sometimes the
puppy with localized demodicosis was obtained for breeding purposes.
The current recommendation is not to treat these puppies so that we can
determine if the condition will stay localized and resolve or if it
will generalize. If it stays localized and eventually resolves without
treatment, the animal is still a candidate for breeding. If the
condition generalizes to cover the entire body, the animal should be
sterilized. If the condition receives treatment and resolves, we will
never know how the disease would have gone in its natural state and
will not know whether the pup is carrying the genetic predisposition
for demodectic mange. In this case, it is best to be conservative and
not take the chance of passing on genetic predisposition for this
disease.
Localized
demodicosis is almost exclusively a "puppyhood" disease. When a puppy
develops localized demodicosis the chance of the condition resolving is
90% unless there is a family history of demodicosis in related dogs. In
this case, chance of spontaneous resolution drops to 50%.
Occasionally
an adult dog develops localized demodicosis. We currently do not have
good understanding of the prognosis or significance of this condition
in an adult dog.
Classically
with generalized demodicosis, the entire dog is affected with patchy
fur, skin infections, bald, scaly skin. Sometimes large patches of
affected skin are present, sometimes multiple "polka dots" of lesions
cover the dog, and sometimes the entire body is involved. The secondary
bacterial infections make this a very itchy and often smelly skin
disease. The approach to generalized demodicosis typically depends
on the age at which the dog developed the disease.
ADULT ONSET--
Most demodicosis occurs in young dogs, under age one and a
half. An older dog should not get demodicosis unless he or she has
an underlying problem with the immune system. In such cases,
demodicosis is considered a indication to seek a more serious hidden
condition such as cancer, liver or kidney disease, or an
immune-suppressive hormone imbalance. A more extensive medical
work-up will be required.
JUVENILE
ONSET -- Young dogs have inherently immature immune systems and are
thus susceptible to the development of demodicosis without any sinister
underlying diseases. As they grow up and their immune systems
mature, they tend to naturally gain control of their mite infestation;
in fact, 30-50% of dogs under age 1 year recover spontaneously from
generalized demodicosis without any form of treatment. Usually
treatment is recommended, though, to facilitate recovery.
IT IS VERY
IMPORTANT THAT DOGS WITH A HISTORY OF GENERALIZED
DEMODECTIC MANGE NOT BE BRED AS THERE IS A HEREDITARY
COMPONENT TO THE DEVELOPMENT OF THE DISEASE.
This
condition represents demodectic mange confined to the
paws. Bacterial infectious usually accompany this
condition. Often as generalized demodicosis is treated, the foot
is the last stronghold of the mite. Old English Sheepdogs and Shar
peis tend to get severe forms of this condition. The infection can be
so deep that biopsy is needed to find the mites and make the diagnosis.
It is one of the most resistant forms of demodicosis.
The treatment
of demodicosis only in part relies on medications; some basic steps can
be taken with regard to pet care to maximize the chance of success.
Physiological stress is an important factor determining the degree of
severity of demodectic mange and the following steps should be taken to
reduce stress:
- Females should be spayed as soon as the
disease is controlled. Coming into heat, hormone fluxes, and pregnancy
are very stressful. Also, predisposition to demodicosis is
hereditary and should not be passed on.
- The dog should be fed a reputable brand
of dog food so as to avoid any nutritionally related problems.
- Keep the pet parasite-free. Worms
are irritants that the pet need not deal with and fleas may exacerbate
the itchiness and skin infection.
- Keep up the pet's vaccinations.
- The mites themselves cause suppression of
the immune system so the pet needs every advantage to stay healthy.
- Skin infections are usually present in
these cases and antibiotics will likely be necessary. It is very
important that cortisone type medications such as prednisone NOT be
used in these cases as they will tip the immune balance in favor of the
mite.
CURRENT
TREATMENT OF CHOICE -- IVERMECTIN
Ivermectin is
a broad spectrum anti-parasite medication with a number of uses though
its use in treating demodicosis is not approved by the FDA. When
ivermectin was a new drug it was hoped that it could be used against
demodectic mange mites as at that time only fairly toxic dips were
available and incurable cases were common. After some experimentation
it was found that daily or every other day dosing is necessary for
effective demodicosis treatment and soon ivermectin was felt
unequivocally to be the drug of choice for this condtion. Note that the
weekly protocols that work for other parasites simply do not work on
Demodex mites.
Ivermectin is
inexpensive relative to Milbemycin (see below) and involves no labor
intensive bathing. It DOES, however, taste terrible if given orally (it
may be necessary for the owner to learn how to give ivermectin as an
injectable treatment.) There is, unfortunately, an important
occasional problem that keeps other treatment options listed: drug
sensitivity. Some individual dogs are sensitive to ivermectin and can
die if subjected to a typical therapeutic dose for demodicosis.
THIS MEDICATION
CANNOT BE ASSUMED SAFE FOR USE
IN COLLIES, SHETLAND SHEEPDOGS, AUSTRALIAN SHEPHERDS,
OLD ENGLISH SHEEPDOGS AND,
SOME WOULD SAY, ANY HERDING BREED.
Sensitivity
to ivermectin may not be predictably limited to “collie
breeds” and thus it is often prudent to use a lower test dose
before initiating the relatively high doses of ivermectin needed to
treat demodicosis. Not all individuals of collie heritage are sensitive
to ivermectin and a test is now available through Washington State
University to determine whether an individual should be able to safely
take ivermectin or not. An alternative to testing is to use a low test
dose for a period of time and watch for mild side effects. If there is
any question about your pet’s potential sensitivity to
ivermectin, your veterinarian will instruct you.
There is a
range of ivermectin doses used in the treatment of demodicosis and it
seems that higher doses do clear infection faster than lower doses.
This means that if a lower dose has been ineffective, a higher dose may
still work. This does not mean that a pet owner should experiment with
ivermectin doses on their own as there is some potential for lethal
toxicity if this drug is not used appropriately.
The high
doses of ivermectin used in the treatment of demodicosis are not
compatible with the commonly used flea product spinosad (Comfortis®). The combination of
spinosad and high doses of ivermectin will increase the likelihood of
ivermectin neurologic side effects. While flea control is very
important during the treatment of demodectic mange, a different product
should be used.
Unless the
animal is largely bald or has a short coat, complete clipping will be
required for maximal contact with the dip.
Dip should be
preceded by a benzoyl peroxide bath to help clear up skin infections
and open the hair follicles so the dip can penetrate to the mites.
Shampoo must sit on the pet at least 10 minutes before rinsing.
CAUTION: this type of shampoo can stain jewelry and clothing.
Dip is
applied by sponge. Gloves should be worn while applying
dip. The dip dries on the dog's fur and should not be rinsed
off. The dog should not get wet between dips.
Dipping
occasionally yields mild sedation as a side effect. Very small
dogs may become highly sedated and require an antidote but this is
unusual. For your convenience, dipping and bathing may be performed at
the hospital thus allowing for veterinary supervision in the event of
side effects.
Dipping/bathing
is recommended every two weeks according to the FDA approved label on
the bottle of dip. Most universities are finding that the cure rate
jumps from 25% to 80% when dip is used at double strength and applied
weekly. No toxic effects have been seen using the dip in this way
and this is our current recommendation when opting for dips except in
very small dogs and puppies.
Dipping is a
fair alternative for ivermectin in collie breeds and in ivermectin
sensitive individuals.
AMITRAZ DIPPING
SHOULD NOT BE USED IN TOY BREEDS
OR IN YOUNG (UNDER 4 MONTHS OF AGE) PUPPIES.
NOTE: Amitraz
is a drug of the monoamine oxidase inhibitor class. People who are
taking selected serotonin reuptake inhibitors (such as Prozac®) could have a bad
reaction to the use of amitraz if they administer dips to pets. Human
diabetics should also avoid administering amitraz dips.
SOMETHING
ELSE YOUR VETERINARIAN MIGHT TRY -- INTERCEPTOR®
Interceptor
(active ingredient: Milbemycin oxime) is normally marketed as a
monthly heartworm preventive; when it is used on a daily basis, it is
effective against generalized demodicosis. This discovery was welcomed
by the veterinary profession as finally demodicosis can be treated
without labor intensive dipping or concern about ivermectin
sensitivity. The downside to this treatment is expense as Interceptor
is typically sold in 6 dose packages and it is not uncommon for several
months of treatment to be needed. Sometimes it is possible to obtain
discounted product that is short-dated (meaning it will expire before
six months have passed). This product cannot be sold for heartworm
prevention if it will expire before it is used up but for daily use
against Demodex mites it would be fine and used well before its
expiration date.
INTERCEPTOR MAY
BE USED IN ANY PATIENT SAFELY;
THE ONLY DOWNSIDE IS EXPENSE.
The younger
the dog, the better the chance of cure. Most dogs under one year
and a half years of age, recovery completely from generalized
demodicosis. In many cases of adult-onset demodicosis, the disease is
controlled with treatment but cure is not always possible. Some
cases can never be controlled.
Treatment, no
matter which option is chosen, should be accompanied by skin scrapes
every 2 weeks. In this way the effectiveness of treatment is assessed
and modifications can be made. After two consecutive scrapes are
negative, treatment is discontinued but a final scrape should be
performed after one month off therapy. The reason for the final scrape
is to be sure the mites are not coming back (which they can do if every
single mite on the dog is not eradicated).
When relapse
occurs it is often because the dog appeared to be normal and the owner
did not return for the appropriate re-scrapings. Relapse is always a
possibility with generalized demodicosis as there is no easy way to
confirm that every mite has been killed but most dogs that relapse do
so within a 6-12 month period from the time they appear to have
achieved cure.
SARCOPTIC MANGE
IS A COMPLETELY DIFFERENT DISEASE.
In older
times, some 30 years ago, dipping dogs with demodectic mange in motor
oil was a popular home remedy. Skin exposure to motor oil can cause
rashes and skin destruction in severe cases. The hydrocarbons can be
absorbed through the skin and cause a dangerous drop in blood pressure.
If motor oil is licked off the coat, resultant vomiting can lead to
aspiration of motor oil into the lungs and pneumonia. Kidney and liver
damage can result from motor oil dipping.
PLEASE: DO NOT
DIP YOUR DOG IN MOTOR OIL!
DEMODEX MANGE
(DEMODECTIC MANGE) TREATMENT
There are
three treatments for demodectic mange that work for most dogs. The
first is the use of amitraz pour on (Mitaban Rx) every other week
for 6 to 8 applications or until 2 consecutive skin scrapings are
negative, which probably cures demodectic mange in about 80% of dogs
when application directions are followed, although this is just a guess
based on averaging results from available studies. This is the only
approved treatment for demodecosis. The second treatment is ivermectin
given by injection or orally at the rate of 250ug/kg or higher (up to
600ug/kg in resistant cases) daily until two skin scrapings are
negative, which probably also works about 80% of the time. This
treatment has to be used very carefully in collies and shelties, who
are more likely to suffer toxic reactions to ivermectin. The third
treatment that is sometimes used is oral milbemycin (Interceptor Rx)
given daily for six to eight weeks and my best guess is that it is
about as effective as the other therapies. It is probably wise to be
cautious about using this therapy in collies and shelties, too --
although we have done this on a couple of occasions without problems,
so far.
Even though
we use six to eight weeks as sort of a minimum therapy time, it is
important to remember that it can take up to a year of therapy in some
dogs to cure demodecosis. It might be possible to cure more dogs if
intense treatment was used longer than a year but we haven't tried
that.
Some dogs who
do not respond to one therapy will respond to one of the others, so it
is probably possible to cure demodectic mange in about 90% of dogs. In
the remaining dogs it is usually possible to control the disease even
if it can't be eliminated, by use of intermittent therapy. We
have done once a month amitraz applications when this was necessary, in
most cases. We have a couple of patients who we use ivermectin
intermittently with (probably average two or three month long
treatments a year).
It seems to
help a lot to use an antibiotic for secondary bacterial infections
during the first two to three months of therapy for demodectic mange
unless treating an early case in which secondary bacterial infection
hasn't occurred. It is also helpful to use an antibacterial and
antiseborrheic shampoo to treat secondary skin disease and get rid of
crusts and exudate on the skin. This is especially important when using
amitraz.
There are a
couple of legal problems associated with the therapy for demodecosis,
which hamper therapeutic efforts in some patients. The first legal
hurdle is that it is illegal to use an EPA approved product in a manner
inconsistent with its labelling and Mitaban (Rx) is EPA approved rather
than FDA approved. So once weekly dips, which seem to work better, are
actually illegal. So is long term intermittent use. The second legal
problem is that the use of ivermectin and milbemycin for the treatment
of demodecosis is an "off-label" use. This isn't illegal, but when
off-label treatments are used they are supposed to be used after an
approved treatment fails. So technically, your vet should use amitraz
first and then the other therapies. This is a problem due to the
requirements for successful use of amitraz in some dog breeds (see next
paragraph).
Amitraz works
best on short haired dogs and on dogs whose medium to long length hair
has been clipped completely in order to allow better exposure to the
amitraz pour on. Longer haired breeds will need to be clipped
repeatedly until therapy is successful, which can be a long time. It
also works best when all scabs and sores have been cleaned off prior to
application and when an anti-sebborheic shampoo has been used prior to
application of the pour on and then the dog at least towel dried.
Finally, it is necessary to sponge or pour amitraz onto the whole
surface of the skin, affected as well as unaffected areas. If these
steps are not taken, amitraz is much more likely to fail.
Now to get to
your specific questions. 1) I think that this is almost certainly
juvenile onset demodecosis. 2) I think it is very likely that the
use of prednisone or other corticosteroids would cause worsening of
demodecosis in a patient who had this condition and I think that it is
likely to have done that in your dog's case. 3) I personally like
the ivermectin therapy best at the present time, although we usually
start with amitraz to try to stay on the right side of the legal
issues. Be persistent with therapy. Most of the treatment failures
result from giving up on treatment before it has a chance to work.
CUTDOWNSKENNELS@HOTMAIL.COM
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