Also Known As: Demodex, Demodectic mange, Red mange, follicular mange
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.
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.
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.
Canine Demodicosis
C a n i n e D e m o d i c o s i s
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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 commonly occur as a result of the demodicosis. After a few months, the skin
may become covered with infected, pus-filled, crusty, bloody sores.
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, secondary bacterial infections
occur, 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.
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 guarded for recovery; the disease may be controlled through medication and therapies,
but not always cured.
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 and lengthy treatment
plan. Thus, the underlying disease should be determined and the dog’s overall health should
be improved before attempting to treat demodicosis. Sometimes in older dogs the disease
cannot be cured but only controlled. Oral antibiotics are often needed for 1-2 months to
treat secondary bacterial infection. Options for treatment of the demodex mites include
topical therapy with weekly amitraz dips, or systemic medication with daily ivermectin or
milbemycin. These potentially toxic medications should be dispensed by a veterinarian at
a carefully calculated dose, and ivermectin (in the dose needed to treat demodex) should
never be used in herding breed dogs such as collies, shelties, Australian shepherds, Old
English sheepdogs, or border collies, as death can ensue. A genetic test is available to
screen animals for sensitivity to Ivermectin (http://www.vetmed.wsu.edu/deptsVCPL/). Regardless of therapy, treatment is continued until one month beyond a negative
skin scraping (no live or dead mites), which is an average of 3-4 months. Regular rechecks
with your veterinarian are important to determine need for continued therapy.
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. Dogs with generalized demodicosis should be spayed or neutered, as they
will pass the immune defect which will predispose their puppies to demodicosis as well.
