Canine Demodicosis

(Demodectic Mange)

Demodex mites are microscopic parasitic mites normally present in low numbers in the skin. When the mites increase to larger than normal numbers in the skin it causes the disease called demodectic mange, or demodicosis. This may present as a few localised lesions, or it may spread over much larger areas including the feet.

When the mites increase like this, you may see “blackheads” which are blocked hair follicles. This large amount of mites can trigger bacterial infections within the blocked follicles; this type of mite infection may or may not be itchy. Sometimes the mite infection can be so serious that deep infection occurs or the hair follicles become so damaged that they rupture under the skin which will be seen as a painful swelling with the possibility of discharging blood or pus. When the disease is widespread dogs can become very unwell and in extreme cases it can even be life threatening.

The typical clinical signs for demodicosis are:

• Patchy hair loss
• Pustules (pimples)
• Furuncles (blisters)
• Scaling, crusting and thickened skin
• Itchy red skin
• Greasy skin

The juvenile form of generalised demodicosis (starting in dogs less than 3 years of age) is thought to be due to an underlying congenital defect in the way their immune system normally controls the mites. There are some breeds in which this juvenile form of demodicosis is more common, suggesting that the increased susceptibility to demodicosis is likely inherited. Some of these breeds are:

• Boxers
• Pugs
• Scottish Terriers
• Staffordshire Bull Terriers

In older dogs over 3 years of age it is referred to as generalised adult-onset demodicosis and the situation is a little different. In some cases, the demodicosis is associated with another underlying disease or drugs that interfere with the normal immune response. Some common causes are:

• Cushing’s disease
• Hypothyroidism
• Cortisone medication
• Cancer

Treatment for demodicosis includes:

• Oral medication to kill the mites
• Antibiotics if there is infection present
• Medicated shampoos.

Successful treatment relies on the skill of the vet to perform accurate skin scrapings to identify mites and to diagnose the exact type of demodex mite as some are harder to resolve than others. Regular monitoring is required to assess response to medication and experience to know how to alter medications or doses to achieve a resolution. If your pet has been diagnosed with demodicosis that is proving slow and hard to resolve or has resolved and then relapsed, then your dog is likely to benefit from a referral to a specialist dermatologist.

In young dogs where underlying causes are less likely, we can completely clear the infection without relapses in over 90% of cases.

For older dogs with demodicosis, further testing may be required to assess if there is an underlying problem causing the infection. In dogs where there is no underlying disease identified, we can resolve the infection but often need to structure a longer term prevention plan to prevent relapses.

This is a contagious mite infection, unlike demodicosis. It is passed on from other infected dogs or from areas that infected foxes may be. It is more likely to be acquired in semirural areas, or inner city parklands during the cooler wetter months when scabies mites can survive longer in the environment.

Scabies causes severe itch all over and you may see hair loss and crusting of the ear flaps, elbows, under the chest or anywhere on the body.

If your pet is on Revolution or Advocate top spot every month, then your pet is on a prevention therapy and should not get scabies.

If you suspect your dog has scabies please see your vet about treatment and prevention of this infection.

Dog scabies does not survive long on people and is self-limiting i.e. will self-resolve over a week or 2. If you are itchy, then you should see your local medical practitioner (GP,) to discuss if you need treatment or not.

Related reading:

• AREN Dermatology Services

Information provided by Melbourne Veterinary Specialist Centre (MVSC), part of the AREN network.

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