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Not All Mites Are Created Equal
Demodicosis is a condition that occurs when the normally self-limiting population of demodex
mites on a dog goes rogue. They are microscopic parasitic mites that inhabit hair follicles, oil
glands, and skin. Demodex mites are non-contagious, host-specific, and are a normal skin
inhabitant of dogs. Demodex mites are NOT Sarcoptes mites (which cause very itchy and
contagious sarcoptic mange).
Dogs of any age can have demodicosis. Young dogs most often get a transient overgrowth of
mites that is localized to a few spots on the face or legs (see below: localized demodicosis). With
a healthy immune response, the majority of these cases will resolve without treatment.
Occasionally demodicosis completely takes the skin of its host hostage (see below: generalized
demodicosis); it spreads to encompass very large areas of skin resulting in massive hair loss
and other complications. This form of demodicosis occurs sporadically in young dogs but
accounts for the majority of the adult cases of demodicosis. The demodex life cycle is completed
on the dog host. Dogs are infected with mites from their mother while nursing during the first
week of life and will have mites throughout their lifetime (in low numbers).
This form of demodicosis presents as small areas of patchy hair loss and flakey skin. It is
suspected that while the immune system is still developing, small populations of mites are
allowed to overpopulate. In young dogs this is called juvenile focal demodicosis (commonly
diagnosed in short-coated or wire-haired dogs and purebred dogs). Focal areas of hair loss are
usually on the face, around the eyes, or on the legs. Once the immune system has appropriately
responded to the parasite, the patchy hair loss will resolve without treatment in the majority of
cases. Infections that do not resolve within a few months or continue to spread require
treatments. Adults dogs very rarely get this type of infection.
Generalized demodicosis occurs in both young and adult dogs and requires a thorough workup
by a veterinarian to narrow down potential underlying causes. This condition can result in very
large patches of hair loss in multiple places, oily midline skin secretions, discoloration and
thickening of the skin, and an overall ill-thrift appearance. It almost always indicates an
underlying health issue no matter what the age of onset, so be alert if these symptoms occur.
Underlying health concerns could include: cancer, allergies, genetic propensity, endocrine
disease, or other conditions or medications causing immunosuppression.
Demodicosis can mimic other diseases. Your pet’s current and previous health history are a
very important part of diagnostics. Dogs with unbalanced nutrition, poor preventative care, or
those living in chronic states of stress are at higher risk of developing demodicosis in addition to
many other health conditions. This is why preventative care and regular checkups are important
in all pets to catch any abnormal or unhealthy conditions as early as possible.
Your local veterinarian can diagnose demodex with some in-house tests. Skin scrapings and
hair plucking from affected areas are the most common test samples. These can be examined
microscopically for signs of mites. In dogs with deep skin infections or severely itchy or inflamed
skin other tests may be utilized. In adult dogs with demodicosis, other diagnostics are also
utilized to determine if an underlying health condition is present.
Once diagnosed, treatment can last several months and is dependant upon the dog’s response
to treatment and other concurrent health conditions. Treatment involves using miticidal
(mite-killing) chemicals. There are many available treatments are not safe to use without prior
knowledge of risks and side effects of the chemical in your pet. Your veterinarian can help
choose the correct miticidal drug and treatment regimen for your pet. Routine vet visits and skin
testing will be needed to confirm successful treatment outcome.
The avermectin family of drugs has been a standby in the treatment of demodex as well as
other canine parasites. While a very useful drug, it can be deadly in the wrong breed of dog or
at the wrong dosages or when used in heartworm positive dogs. Never use avermectins in
herding breed dogs (like collies or shepherds) without discussing the risks in detail with your
pet’s veterinarian. There is a genetic test available to determine if your dog has the avermectin
sensitive gene. Other equally effective chemicals are available for at-risk breeds and the new
chewable type of flea and tick preventatives (isoxazolines) have also shown promise as
Amanda Burow, D.V.M. (Dr. B), is a graduate of Iowa State University’s College of Veterinary Medicine. Dr. Burow’s patient list includes hunting dogs of all varieties, as well as several field trial dogs and full time sporting guide dogs. In addition to practicing general veterinary medicine, she has special interest in the areas of preventive care, emergency medicine, and dermatology. In her spare time, she enjoys being outdoors and on the lake, staying active, reading, and spending time with family and friends.
Mud River is proud to share these tips from Dr. B with our customers. Keep in mind it is best to work with your local veterinarian to determine the needs for your animals.