Demodex Mites in Dogs 

1. Localised (spontaneous) demodicosis

Dogs of all breeds can suffer from this form of demodicosis. Young dogs are mostly affected.

With the localised form, there are up to five areas of skin with little or no hair. If there are more than five areas, it is the generalised form. The areas are reddened and scaly, whilst the dog often experiences no itching. The changes caused by demodex mites can be found on your dog’s head, throat, limbs and torso.

It’s not uncommon for the disease to be detected completely by accident or not at all. Spontaneous recovery occurs with over 90% of cases with localised demodicosis.

2. Localised, iatrogenic demodicosis

Another form of localised demodicosis is sometimes triggered by a localised weakening of the immune system. This occurs, for instance, from cortisone injections or topical applications of a cortisone cream. Mostly only the area of skin affected is where the injection was given or the ointment applied.

Skin changes occur similarly to the spontaneous form, resulting in areas in the fur with hair loss, skin reddening and formation of scales. The skin is often very thin. This sometimes persists for a long time due to the depot effect of the cortisone injection. If no complications such as inflammations occur, you can wait for healing without treatment.

3. Generalised, hereditary demodicosis

This form is assumed to be caused by hereditary immunodeficiency combined with additional immunosuppression. Depending on the breed, this occurs in young dogs up to 1.5 to 2 years of age.

Skin alterations often begin with single spots – similar to the localised form with the formation of scales, skin reddening and hair loss, but spread quickly (generalisation). The head and front limbs are often first affected, but the alterations then spread throughout the skin.

In this form, bacterial infections usually develop as a result of the demodex mite infestation. These cause itching and can result in severe skin symptoms. Symptoms include fistulas, edema, papules and pustules, as well as severe complications such as fever or swelling of the body’s lymph nodes.

4. Generalised demodicosis from immunosuppression

Older dogs too can suffer from a generalised form of demodicosis regardless of breed.

On the one hand, development can be iatrogenic, i.e. due to the administration of immunosuppressive medication like cortisone. On the other hand, existing primary diseases like tumours and metabolic diseases (cushing, diabetes, hypothyreosis etc.) can also trigger excessive reproduction of demodex mites.

5. Pododemodicosis

With this form of demodicosis, inflammatory skin changes occur in the paws, which are then swollen and painful.

Breeds like Great Danes, Old English Sheepdogs and other large breeds are mostly affected, as well as West Highland White Terriers, Pugs, French and English Bulldogs and Shar Peis. This form can emerge as a stand-alone problem, in addition to the generalised form.

6. Demodicosis caused by Demodex cornei and Demodex injai

There are other forms of demodicosis, although they are caused by different mite species than the previously mentioned Demodex canis. However, researchers have not yet been able to clarify whether transmission occurs from affected to healthy dogs with these species.

Demodex cornei is accompanied by skin reddening, scales and, unlike other demodex mites in dogs, significant itching. Demodex injai apparently lives in the sebaceous glands and leads to fatty skin, poor coat quality and a thinning coat especially on the back.