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Name
Demodectic Mange, Canine
Short Description
Demodex, Demodectic mange, canine demodicosis
Affected Animals: Dogs and cats.
Overview: Canine demodicosis is a type of mange that occurs
when abnormally high numbers of a mite called Demodex canis multiply
on the skin. This mite is normally present in small numbers in the
skin of healthy dogs, but when a dog's immune system becomes
weakened, the mites can overgrow and cause disease and inflammation
of the skin.
It is not uncommon for nursing puppies to become infected with this
eight-legged skin parasite during the first two to three days of
life. The mites can be passed from the mother to the nursing puppies
because the puppies have weak and underdeveloped immune systems that
allow the mites to overgrow, causing occasional localized patches of
hair loss, redness and scaling. However, as the puppies grow and
their immune systems become stronger, they are usually able to fight
off the disease on their own with little or no medical intervention.
It is possible for older dogs -- those four years
of age or older -- to develop canine demodicosis, but for them, the
disease is much more serious. The infestation can be localized to a
few areas of the body, or generalized, meaning that the mites are
all over the body. Generalized demodicosis usually means that the
dog has a serious underlying disease that is weakening the immune
system, thereby making the dog susceptible to overgrowth of the
Demodex mites.
Clinical Signs:
There are two types of demodicosis -- localized, meaning confined to
a few specific areas of the skin, and generalized, in which the
mites have spread all over the body. Each type has a different set
of signs or symptoms.
Localized demodicosis occurs most often in young
puppies six months old or younger. The mites usually will appear on
the front legs and face, and the effects of their presence will be
fairly mild. Hair loss is a common symptom, and in the bald patches
the skin may be red and scaly, and may or may not be itchy. Most
cases heal without treatment and do not progress to generalized
demodicosis.
Generalized demodicosis is far more severe than the localized form,
especially when it starts when the dog is an adult of four or five
years of age. Clinical signs begin with multiple areas of hair loss,
scaling, and redness. These small areas get larger and progress to
affect the entire body, causing severe irritation of the skin.
Secondarily, severe bacterial infections that are often resistant to
antibiotics commonly occur as a result of the demodicosis -- making
treatment almost impossible. After a few months, the skin may become
covered with infected, pus-filled, crusty, bloody sores. Because the
dog's quality of life is usually so poor at this point, owners often
elect euthanasia.
Symptoms:
See Clinical Signs.
Description: Demodex is a type of skin mite that has a head
and eight legs extending from a long, tubular body. In the skin of
healthy dogs and puppies, the mites can exist in small numbers, but
when the dog's immune system is weakened or not functioning
normally, the population of mites begin to increase to the point
that skin disease begins.
Demodicosis can manifest itself in two forms. The first is a milder
form that occurs commonly in young puppies that get the mites from
their mother while nursing. The Demodex mite, which will be
localized to just a few regions of the puppy's skin, may cause hair
loss, mild redness, scaling, and occasional itchiness. However, with
time, the puppy's immune system will strengthen so that it resists
the mites and prevents them from overgrowing.
Generalized demodicosis may occur in a dog that,
as a puppy, had localized demodicosis that never went away, or in a
dog that developed localized demodicosis as an adult. This form of
the disease can be very serious because it usually means that
another disease is causing the dog's immune system to function
poorly, allowing the mite to proliferate at an uncontrolled rate.
Because the mites burrow deep into the skin, they cause irritation
leading to severe inflammatory skin disease. Many times, forms of
bacteria that resist antibiotic medications will grow on the skin,
causing severe infections that make the illness worse. The diseased
skin of a dog with generalized demodicosis is often hairless,
reddened, scaling and, in certain areas, will ooze a pus-filled,
bloody material that forms thick crusts. When severe infection
occurs, an owner may elect euthanasia for the affected dog because
of the poor quality of life.
Diagnosis: The veterinarian will be able to diagnose
demodicosis after analyzing skin scrapings from the dog and
detecting the presence of the mites under a microscope. In an adult
dog that has the more severe, generalized form, additional
diagnostic tests may need to be performed to find the underlying
disease that has caused the immune system to be weak and has made
the dog susceptible to demodicosis as a result.
Prognosis: Localized demodicosis will usually heal on its
own within six to eight weeks. The treatment is usually minimal, as
most cases will resolve without treatment. The prognosis for
generalized demodicosis affecting adult dogs greater than two years
of age is poor for recovery; the disease may be controlled through
medication and therapies, but not always cured.
Transmission or Cause: Localized demodicosis usually is passed from the
mother to her nursing puppies after they are born. Generally, a
puppy will clear the mite infection once its immune system
strengthens. However, when a young dog is not able to rid itself of
mites, or when treatment fails, the animal will continue to have the
infection as an adult.
Adult dogs can have localized demodicosis from puppyhood, or develop
localized demodicosis during periods of stress when their immune
systems are suppressed. For example, dogs that have puppies
sometimes will develop localized areas of demodicosis because their
immune systems are temporarily weakened from the pregnancy. However,
the demodicosis usually goes away once the dog's immune system
recovers.
Unfortunately, older dogs that have an underlying
disease such as cancer or are being given medications that suppress
the immune system can develop the generalized form of the disease.
Treatment:
When the demodicosis is localized or only affects a few regions of a
puppy's skin, it will usually heal within six to eight weeks with
minimal or no medical treatment. Generalized demodicosis, however,
often requires a very intense, lengthy, and costly treatment plan.
Thus, the underlying disease should be determined and the dog's
overall health should be improved before attempting to treat
demodicosis. Many times the disease cannot be cured but only
controlled. Amitraz solutions, dispensed at a concentration and
regime set by a veterinarian, can be effective in killing the mites.
A veterinarian should be consulted about other treatment options
that may be available.
Prevention: The best prevention is to keep animals in good
health. Regular visits to the veterinarian will help maintain the
dog's overall health and detect underlying conditions that could
weaken the dog's immune system. Regular de-worming and vaccinations
are also important. Pet owners should consult with a veterinarian
before breeding dogs that have had demodicosis.
