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Hairless, scaly areas are typical of a demodex mite infestation.
Has your dog ever had bald patches in its fur although it is otherwise well? Demodex mites could be the cause. These small parasites populate the fur of dogs and trigger demodicosis when they reproduce heavily. Find out in this article how you can help your pet and what else you need to know about demodex mites with dogs.
Demodex mites (Demodex canis, hair follicle mites) are a normal part of a dog’s skin fauna. They are usually transmitted by mother dogs to their puppies.
In up to 50% of all healthy dogs, mites can be detected living in the hair follicles, as well as in the dog’s sebaceous and perspiratory glands. They don’t cause itching or any other symptoms of disease – they are usually not contagious either.
Hair follicle mites only become problematic if they reproduce en masse. Only then do they trigger symptoms of illness.
Manifestations & symptoms: What are the most significant symptoms?
Medics speak of demodicosis if demodex mites reproduce uncontrollably on a dog. This occurs with dogs in different forms and with different symptoms. Overall, there are six variants:
Variant 1
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.
Variant 2
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.
Variant 3
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.
Variant 4
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.
Variant 5
5. Pododemodicosis
With this form of demodicosis, inflammatory skin changes occur in the paws, which are then swollen and painful.
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.
Diagnosis: How can demodex mites in dogs be detected?
All forms of demodicosis are diagnosed in the same way: the vet needs a deep skin scraping. Depending on the localisation of the skin alterations, squash preparations and examining the roots of plucked hairs can provide demonstrable evidence.
Due to inflammation, sometimes chronic thickened skin cannot be diagnosed in the way described above. If demodex mites are strongly suspected, vets therefore take a skin biopsy from your dog.
Demodex mites become visible under the microscope.
Treatment: What are the treatment options?
Treatment for demodicosis depends on the form and symptoms. The vet will decide accordingly which treatment is necessary.
Spot-on products and shampoos can help to treat demodex mites in dogs. However, the vet may need to administer antibiotics if a secondary infection occurs. The success of treatment can be supported with immune-strengthening methods.
Prognosis: What are the chances of recovery with demodex mites?
The prognosis depends on which form of demodicosis the dog has. Whilst the localised forms sometimes heal even without treatment, treating generalised forms can be very demanding. Many treatment cycles are often necessary.
With generalised demodicosis due to immunosuppression, the vet primarily has to treat the underlying diseases.
Prevention: How do I avoid demodicosis in dogs?
Since demodex mites are part of a dog’s normal skin fauna, prevention with medication is not possible. Instead, it is recommended to support and boost the immune system to prevent in particular the localised, spontaneous form.
There is a predisposition for demodicosis in short-haired brachycephalic (short snout) breeds like English or French Bulldog and the Pug, Shar Pei, Doberman, German Shepherd, Dachshund and some terrier breeds. Since this predisposition is hereditary, dogs suffering from generalised demodicosis should not be deployed for breeding.
Franziska Pantelic, Veterinarian
I am supporting the zooplus magazine for several years with my extensive expertise. I became a licensed veterinarian as early as 2009 and currently operate a mobile small animal practice in the metropolitan area of Munich.
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