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Canine demodicosis

Demodicosis is caused by a microscopic mite, Demodex canis, which normally lives in the hair follicles of all dogs, in very small numbers and without causing harm. The disease appears when this parasite multiplies excessively, which almost...

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Definition Signs Causes Transmission Diagnosis Treatment Prevention Complications When to see a vet Prognosis FAQ Sources Affected species

What is it?

Demodicosis is caused by a microscopic mite, Demodex canis, which normally lives in the hair follicles of all dogs, in very small numbers and without causing harm.

The disease appears when this parasite multiplies excessively, which almost always reflects a failure of the skin's defenses: immaturity in young people, underlying disease or weakening treatment in adults.

It takes two forms: a localized form in young dogs, benign and often self-limiting, and a generalized form, more severe, which requires long treatment.

Key point

The generalized superinfected form is a serious disease: it requires regular veterinary monitoring and comprehensive treatment.

Commonly observed signs

These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.

Related signs — each one links to its page:

Hair loss Scabs and skin lesions Itching Dull coat Swollen lymph nodes Pain

Hairless areas, well defined, first around the eyes, on the muzzle and on the front legs.

Reddened, thickened skin, sometimes grayish, with black dots at the base of the hairs.

Scabs, dandruff and scales.

Itching is often moderate, or even absent at first: this is a sign that helps distinguish it from sarcoptic scabies, which is very itchy.

In the generalized form: extensive plaques, superinfected skin, oozing, smelly, painful to the touch.

Lymph nodes enlarged and reduced when a bacterial infection sets in.

Involvement of the paws alone in some dogs, with lameness and swelling of the spaces between the toes.

When to consult without delay

This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.

Causes and risk factors

Excessive multiplication of the Demodex canis mite in hair follicles.

In puppies, it is favored by a still immature immune system, sometimes with a hereditary component.

In adults, the appearance of demodicosis should prompt a search for a cause of reduced immunity: hormonal illness, general illness, tumor, or treatment reducing defenses.

Stress, malnutrition, a heavy parasitic infestation or heat in the female dog can contribute to the outbreak.

Young age: the localized form mainly affects puppies and dogs less than a year and a half.

Familial predisposition, with more sensitive bloodlines.

Poor general condition: internal parasitism, undernutrition, chronic illness.

Treatments reducing immune defenses, particularly prolonged ones.

Hormonal diseases and general illnesses in adult dogs.

Significant stress, difficult withdrawal, overloaded community life.

Transmission

The mite passes from the mother to the puppies through close contact in the very first days of life: this is the normal route of colonization, in healthy dogs as in others.

Outside of this period, the disease is not considered contagious: a sick dog does not contaminate other dogs in the household, who are already harboring their own Demodex.

There is no transmission to humans or cats.

Diagnosis and care

Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.

The diagnosis is based on deep skin scrapings, carried out in consultation: the veterinarian takes the skin until blood beads up, then observes the mites under a microscope.

Examination of plucked hairs or a biopsy may be necessary on thick areas, such as the pads.

Additional samples look for an associated bacterial or fungal infection, which is very common.

In an adult, a general assessment is essential to identify the underlying disease: without this, the skin treatment will not work.

Monitoring is done by repeated scrapings: the treatment is only stopped on successive negative results, never solely on the dog's good appearance.

Treatment

The localized form of young people often heals alone or with local care, under veterinary supervision: it should not be treated blindly.

The generalized form requires prescribed and prolonged external antiparasitic treatment, continued for several weeks beyond the disappearance of the lesions.

Associated bacterial infections warrant antibiotic treatment and local care, including appropriate shampoos.

The underlying cause must be treated in adults, otherwise relapses will repeat.

Over-the-counter treatments, home remedies based on oil, waste oil or agricultural products are dangerous: they burn the skin and delay treatment.

Nutritional support improves skin quality during regrowth.

Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.

Prevention

There is no direct prevention, the mite being present in all dogs.

Maintain good general condition: quality food, deworming, flea and tick control.

Avoid treatments that weaken immunity without veterinary supervision.

Do not breed a dog that has presented a generalized juvenile form.

Monitor the skin of puppies from a litter at risk and consult at the first areas without hair.

Possible complications

Deep bacterial superinfection of the skin, painful, sometimes accompanied by fever and depression.

Long-lasting thickening of the skin and scarring with incomplete hair regrowth.

Disabling leg damage, with persistent lameness.

In neglected generalized forms, marked alteration of the general condition.

Relapses until the underlying cause is identified and treated.

When to see a veterinarian

Your puppy has one or more hairless areas around the eyes, nose or paws.

The lesions spread, the skin becomes red, thick or oozing.

Your adult dog suddenly develops extensive hair loss.

The skin smells bad, feels sore, or bleeds.

Your dog is limping with swollen paws between his toes.

He is depressed, eating less or has a fever: consult quickly.

Prognosis

The localized form of young dogs recovers in the vast majority of cases, often without sequelae.

The generalized form also recovers in most dogs, but at the cost of long treatment, sometimes several months, and rigorous monitoring.

In adults, the prognosis depends mainly on the disease that allowed the parasite to proliferate.

Premature treatment cessation is the leading cause of relapse.

Frequently asked questions

Can I get demodicosis from my dog?

No. Dog Demodex is not transmitted to humans or cats. This is an important difference from sarcoptic mange, which can cause temporary itching in humans.

Should I isolate my dog from other dogs in the house?

This is not necessary in usual cases: each dog already harbors its own Demodex and the disease is not contagious between adults. The veterinarian will tell you if your situation requires special precautions.

My ten year old dog has just developed one: is this worrying?

In an adult, this disease is a signal: it often reveals another condition which weakens the defenses. A complete workup is warranted, as treating the skin alone will not be enough.

Why does the treatment take so long?

Because the mites are lodged deep in the follicles and the skin takes time to rebuild itself. Treatment continues several weeks after apparent healing, until repeated negative scrapings.