Canine Demodicosis


Why should I bring my pet to Willows for Demodicosis?

Willows is one of Europe’s leading small animal referral centres. Our state-of-the-art hospital is led by internationally renowned Specialists who are committed to providing the highest standards of veterinary care. The Dermatology service at Willows is led by Dr Richard Harvey BVSc DVD DipECVD PhD FRSB FRCVS, who has treated many dogs with demodicosis and has extensive experience in diagnosing and treating patients.

Our Dermatology service is supported by our multi-disciplinary team of Specialists across a number of disciplines including; Internal Medicine and Soft Tissue. In addition, Willows has a large dedicated team of Nurses and clinical support staff available 24 hours a day, every day of the year to provide the best possible care for your pet.


What is Demodicosis?

Demodicosis is the disease caused when Demodex mite numbers increase within the skin. Demodex spp. are cigar shaped microscopic parasitic mites that live within the hair follicles of all dogs. These mites are passed to puppies from their mothers in the first few days of life, and then live within the hair follicles for the duration of the animal’s life without causing problems. It is thought that the body’s immune system normally helps to keep mite numbers ‘in check’ and prevent the populations getting out of control. For the vast majority of dogs, these mites never cause a problem. However in some instances, mite populations become huge resulting in inflammation and clinical disease.

What Treatments are Available for Demodicosis?

Mild and localised forms of demodicosis in young dogs may not require treatment, and may resolve spontaneously as the animal ages. These cases should be closely monitored if no treatment is given.

Generalised cases in young dogs and those in adult dogs require intensive treatment. A relatively new group of drugs called the isoxazolines are the treatment of choice. Dogs are normally given a tablet to take every one to three months. Other treatment options include certain spot-on products and dip solutions. In severe cases who are not responding to the licensed treatments, off-licence treatments must be used. Some of these drugs, such as ivermectin and milbemycin, are used for demodicosis in other countries.

An essential part of treating adult onset cases is to identify the underlying illness that triggered the problem. This often requires blood testing and scans (CT, ultrasound) to investigate.


What Causes Demodicosis?

There are two presentations of demodicosis depending on the age at which it develops.

Juvenile onset demodicosis tends to occur in puppyhood between the ages of three months and 18 months, and occurs in both localised and generalised forms. The exact cause is quite poorly understood but probably occurs due to an immature immune system which allows mite numbers to increase. This defect may or may not resolve as the puppy ages. It is thought to be ‘mite specific’ because these puppies are healthy in all other respects and do not succumb to other infections.

Adult onset demodicosis usually occurs in the generalised form and in dogs over four. It is generally considered a more severe disease than its juvenile onset counterpart. In these cases, mites have been controlled in normal numbers in the hair follicles for years prior to the onset of disease; the disease tends to result from a systemic illness affecting the immune system. Common triggers for adult onset demodicosis include hormonal diseases and cancer.

Figure 1: Patchy hair loss on a young dog with localised demodicosis


How is Demodicosis Diagnosed?

Demodicosis can often be suspected following a review of the animal’s history and assessment of the clinical signs. The parasitic mites within the hair follicles result in plugging and the formation of ‘black heads’. Hair loss is commonly seen (Figure 1).

Demodicosis can usually be diagnosed relatively easily. Hairs can be plucked from the affected skin and then examined under a microscope for the presence of the mites (Figure 2). Alternatively, the skin can be squeezed and then scraped with a blade to collect up the surface debris from the skin.

Figure 2: Cigar shaped Demodex mites recovered from plucked hairs in a dog


What Can I Expect if my Dog is Treated for Demodicosis?

The prognosis for localised disease in young dogs is very good, and most recover uneventfully from the disease. Generalised cases in young dogs can take many weeks of treatment, however it is usually possible to control the disease with a good long term outlook. The prognosis for adult onset generalised demodicosis is far more uncertain, as many of these dogs have an underlying systemic illness. If this illness can be identified and corrected, the prognosis for managing the demodicosis is much better. Some cases require long term medication to keep mite numbers controlled.

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Skin and Ear Clinic

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To assist owners whose pets have skin and ear conditions, we have put together a range of information pages to talk you through some of the more common dermatology conditions seen by our Specialist team.