Demodex (Canine)

Canine demodex is a non-contagious parasitic skin disease caused by the microscopic mite, Demodex canis. This parasite may be found living in the hair follicles of both normal and affected dogs. The initial proliferation of mites may be due to a genetic or immunologic disorder.

Common name: Canine demodex, demodicosis, Demodectic, follicular, or red mange

Scientific name: Canine demodex, demodicosis, demodectic mange

Diagnosis

Signalment

In young, otherwise healthy dogs, a genetic predisposition is likely present. The breeds that appear to be at increased risk for demodicosis include the West Highland White terrier, Chinese Shar Pei, Scottish terrier, English bulldog, Boston terrier, Great Dane, Weimaraner, Airedale terrier, Alaskan Malamute, Doberman Pinscher, and Afghan hound. However, demodicosis occurs in all breeds. Genetics, suppression of the immune system, other underlying serious illness, poor nutrition, stress, heat cycles, giving birth, and other parasitic diseases may all be predisposing factors that allow mites to multiple in large numbers.

Incidence/prevalence

While the exact incidence of canine demodicosis is unknown, it is the most common form of mange in dogs.

Geographic distribution

There is no known geographic predilection for this disease.

Clinical signs (primary most to least frequent, scientific term, synonyms)

Erythema (redness), alopecia (hair loss), seborrhea sicca (dry skin, flakes), seborrhea oleosa (oily skin), pruritus (itch).

Clinical signs (secondary, most to least frequent, scientific term, synonyms)

Papules (red bumps), pustules (pimples), follicular casts (keratin and follicular material adherent to the hair shaft), comedones (blackheads), swollen, painful, exudative and crusted skin lesions (due to secondary deep bacterial infection), enlarged lymph nodes, ceruminous (waxy) otitis externa (inflammation of external ear canal).

Cause (scientific, common term)

Demodex canis, genetic predisposition, immunosuppression.

Organ system affected (most to least affected)

Skin, many other organ systems affected if concurrent, immunosuppressive disease is present.

Diagnostic tests

Deep skin scraping, skin cytology (impression smear, acetate tape preparations) to evaluate for infection, skin biopsy. If adult in onset, other diagnostic tests may be indicated to evaluate for an underlying disease condition.

Differential Diagnosis

Superficial or deep pyoderma (skin infection due bacteria), malassezia dermatitis (skin infection due to yeast), dermatophytosis (ringworm, fungal infection), hypersensitivity (allergic skin disease), auto-immune skin disorders.

Overview

Canine demodex, also known as demodicosis or demodectic mange, is a non-contagious parasitic skin disease caused by the microscopic mite, Demodex canis. This parasite is a normal inhabitant of the skin and ear canal. Two types of demodicosis are recognized, localized and generalized, and the course and prognosis is very different for each. Localized demodicosis presents as one or more small areas of red, scaly, non-itchy patches of hair loss often located on the face or forelimbs. Most of these cases will resolve without treatment. Generalized demodicosis involves several regions of the body or two or more feet. Secondary skin infections, which cause itch, may manifest as papules (red bumps), pustules (pimples) and follicular casts (keratin and follicular material adherent to the hair shaft). Comedones (blackheads) and swollen, painful, exudative and crusted skin lesions, as well as enlarged lymph nodes, are present in more severe cases. The generalized form may begin in young dogs (3-18 months of age) and they may carry this condition into adulthood or a true adult-onset of the disease may occur. The adult-onset form is generally defined to begin after 18 months of age and may be more difficult to manage. In either case, the initial proliferation of mites is likely due to a genetic or immunologic disorder. Deep skin scrapings establish the diagnosis in most cases. Additional sampling of the skin to evaluate for skin infection is also performed. In older dogs with demodicosis, or patients not responding to appropriate therapy, further diagnostic testing is always warranted to search for an underlying immunosuppressive illness, such as systemic, endocrine (hormonal), or neoplastic (cancerous) conditions. Treatment with immunosuppressive medications, such as steroids and chemotherapy agents, may also result in demodicosis.

While demodicosis may occur in all breeds, those at increased risk include the West Highland White Terrier, Chinese Shar Pei, Scottish Terrier, English Bulldog, Boston Terrier, Great Dane, Weimaraner, Airedale Terrier, Alaskan Malamute, Doberman Pinscher, and Afghan Hound. Due to the hereditary nature of this condition, patients with generalized demodicosis should not be used for breeding purposes.

Treatment

Home Care

There is no adequate home care regimen for demodecosis.

Professional Care

A veterinarian may prescribe a safe and effective treatment program that includes medication administered by mouth or the application of a dip to kill mites. Therapeutic bathing and antibiotics are often prescribed for several weeks to treat secondary skin infections.

Action

Diagnosis and development of a treatment plan should be made by a veterinarian. Regular re-evaluations, usually at 4-6 week intervals, are necessary to monitor the response to treatment and perform microscopic mite counts.

Outcome

Both the localized and generalized form of disease can usually be effectively treated. However, if immunodeficiency or a concurrent illness is present, response to treatment may be poor, unless the underlying disease is effectively managed. Treatment may be required for several months to over a year and compliance is critical for a successful outcome. Treatment for the generalized form of disease is continued for 30 days after a second negative skin scraping is obtained and a cure is not declared until after a disease free interval of one year.

Recommended Treatment

Demodex must be treated by a veterinarian. See your veterinarian if Demodex is suspected.