Tag Archives: itch

Demodectic mange

Demodectic mange is caused by the demodex mite, Demodex canis, which lives in normal skin and is present in small numbers in all dogs.  Humans have their own demodex mites (D. folliculorum, D. brevis) and the dog demodex mite never affects humans.

The entire life cycle of the demodex mite is spent on the skin. It lives in hair follicles and feeds on cells, serum and epidermal debris.

Transmission of mites from bitch to puppies occurs during nursing in the first 2 days of life.

Occasionally a puppy’s immature immune system allows the mites to multiply abnormally and mild localised skin disease results.  A small proportion of affected pups have a more depressed immune system and generalised demedicosis develops.

The signs of localised demodicosis include patchy hair loss and mild scaliness on the face.  Sometimes the skin is mildly red but in the early stages it is usually not itchy. Most cases occur before 6 months of age and heal spontaneously.

Up to 10% of affected dogs progress to the generalised form. It usually starts during puppyhood. With generalised demidicosis we see hair loss, inflammation and enlarged glands. Secondary bacterial infections cause scratching, redness, swelling and crusting of the skin.

Dogs with chronic generalised demodicosis have depressed immune T-cell responses. Eradication of the mites results in restoration of the T-cell function.

Breeds predisposed to generalised demodicosis include the Old English Sheep dog, Afghan Hound, Collie, German Shepherd, Staffordshire and Pit bull terrier, Doberman, Dalmatians, Great Dane, English Bulldogs, Boston terriers, Dachshunds, Chihuahua, Boxers, pugs, Sharpeis, Beagles and Pointers. Pure bred dogs have a much higher incidence than mongrels. There is evidence that it is an inherited problem.

To diagnose demodectic mange we scrape affected areas with the side of a scalpel blade and check for mites under the microscope.

We usually do not treat mild localised demidicosis as 90% of cases will clear spontaneously.

If the hair loss spreads and the skin becomes red, itchy or crusty then we treat the pup with a miticide. Regular skin scraping monitors the progress of eradication.  Treatment is continued for at least a month after a negative skin-scraping.

Secondary bacterial infections are treated with antibiotics and antiseptic shampoos as they arise.

Sarcoptic mange or scabies

Itchy dog?

Sarcoptic mange causes severe itching.  Dogs chew and scratch their skin constantly.  They lose hair and the skin is thick and red, especially on the ears, legs and belly.

What causes sarcoptic mange?

It is caused by a mite that lives on the skin of any age dog.  It’s also called fox mange. Many dogs catch it from foxes.

Is it contagious?

Sarcoptic mange is highly contagious to other dogs. Humans in close contact with their dog  can catch it, too.  Although the mites are not able to complete their life cycle on humans, they cause a rash and severe itching before they finally die.  Contact your family doctor or pharmacist for advice on treatment.

How is sarcoptic mange diagnosed?

Diagnosis is made by scraping the skin with the side of a scalpel blade and examining it under the microscope.  Despite severe itchiness there are often only a small number of mites present on the dog.  If all skin scrapings are negative and we are still suspicious we do a treatment trial.

How is it treated?

The spot on treatment Revolution applied weekly for 3 weeks is easy and effective.  Sometimes we inject or drench with ivermectin weekly. Ivermectin is not licensed for use in dogs and is dangerous for collie breeds.

All dogs in contact with the affected dog should be treated.

Discard the dog’s bedding before treatment.

If any member of the family develops an itchy skin rash, please tell your doctor that you have been exposed to a dog with sarcoptic mange, also known as scabies.

Flea control in cats

Because of the all the rain over the last 6 months and now the very warm days, fleas are hatching in unprecedented numbers  around Canberra.

Signs of flea infestation:

  • Cats develop an allergy to flea bites. They groom or scratch excessively and develop “miliary” dermatitis.
  • The fleas cause anaemia in kittens and debilitated animals.
  • Cats are infested with tapeworm (Dipylidium caninum) from eating infected fleas during grooming.

Flea control

  • Conquer fleas on your cat with long lasting flea control products (Frontline, Advocate, Revolution, Advantage) applied as a spot on. Flea collars, shampoos and powders kill fleas present on your cat at the time of application but have little residual effect.
  • Remove flea eggs, larvae and pupae from the environment with regular vacuuming of carpets, sofas and beds. Throw away or burn the dust bag to prevent eggs and larvae developing.
  • Professional fumigation controls larvae and pupae.
  • Wash bedding in hot water or replace regularly.
  • Spray garden sheds, cars and favoured outdoor sleeping spots.

Cat fleas hatch from flea pupae in your house in warm, humid conditions. Our carpeted, centrally heated homes are ideal for the year round development of fleas.

After feeding on a cat adult female fleas lay eggs that fall off onto couches, carpets and beds. The microscopic eggs develop first into larvae that migrate deep into carpets, furniture or cracks in floors away from the light, and then into pupae. The pupae contain adult fleas which lie in wait for the next cat or dog to pass.

Effective flea control depends on knowing the flea’s life cycle.