Demodicosis – when the skin suffers

A dull coat, hairless, inflamed areas of skin and often very severe itching are characteristic of this parasitic skin disease, which occurs worldwide and can affect dogs of all ages. It is triggered by a mite, Demodex, which is also found on healthy dogs. Why it multiplies at an above-average rate in certain cases and leads to the skin changes mentioned above is still not fully understood. The disease is not considered contagious.

INHALT
Causes and development Symptoms Diagnosis Treatment Forecast
Causes and development

Demodex mites are part of the normal skin flora of dogs and are found primarily in the hair follicles, but also in the sebaceous and sweat glands. Triggered by certain factors that have not yet been fully researched, there is an unnatural increase in the number of mites, which then leads to the destruction of the hair follicles and the overlying skin. This results in secondary bacterial infections, some of which cause severe, purulent skin inflammation. Generalized demodicosis in young dogs is thought to be caused by a specific defect in the immune cells and is therefore considered hereditary. In contrast, spontaneous, localized, often self-healing demodicosis in young dogs is not hereditary and therefore does not require exclusion from breeding. In older dogs, stress, malnutrition, or underlying internal diseases are believed to lead to excessive reproduction of Demodex mites and the associated skin changes.

Demodex mites under the microscope
Microscopic image of Demodex mites
Symptoms

Affected dogs usually first show a few scaly, hairless patches in their coat, but general hair loss may also occur. At this stage, there is often no itching. The affected areas of skin may turn gray as the condition progresses. Secondary bacterial infections can lead to pustules, crusts, and ulcers. Young dogs often show the first skin changes around the eyes, lips, or limbs. If hair loss is limited to certain areas, it is considered localized demodicosis, which, according to the latest findings, is not hereditary. In most cases, self-healing occurs during this phase and the symptoms disappear after a short time.

However, if the skin changes spread to the entire body, this is referred to as generalized demodicosis, which is believed to have a hereditary component. In this phase, the symptoms are often accompanied by severe itching, swollen lymph nodes, severe general discomfort, fever, and pain.

Diagram of Demodex infection of the skin
1 Comedones (blackheads) on the skin surface | 2 Inflammatory change in the hair follicle (redness) | 3 Demodex mite | 4 Demodex mites magnified
Diagnosis

A veterinary examination and treatment is strongly recommended at the latest when the generalized form develops. Even if the veterinarian can already make a tentative diagnosis based on the dog's history and a thorough clinical examination, further examination of the skin is essential to confirm the presence of Demodex mites. Skin material is taken via a deep skin scraping or skin biopsy (skin sample) in order to detect live Demodex mites. It should be noted that only a significantly increased number of eggs, larvae, and mites indicate disease, as individual Demodex mites are part of normal skin colonization.

Treatment

Young dogs suffering from localized demodicosis do not usually require treatment, as the skin changes resolve on their own. In case of doubt, only any secondary infections that may occur should be treated appropriately.

However, generalized demodicosis should always be treated by a veterinarian due to the severity of the symptoms alone. Treatment is very lengthy and includes both external and general treatment. Affected animals are usually treated with an external mite-killing agent applied to the entire body and also receive spot-on or oral preparations. Please discuss the exact treatment plan for your pet with your veterinarian.

Forecast

The prognosis for localized demodicosis is good. In cases of generalized demodicosis, the chances of recovery depend on whether any underlying diseases or immune system disorders can be treated. If this is not the case, the prognosis is generally poor to unfavorable. In some cases, however, the symptoms can be suppressed with lifelong treatment. Due to the hereditary component of the disease, young animals affected by generalized and recurrent demodicosis should be excluded from breeding.