Jun 22 2016

Itchy Dog? It Might Be Mites

Skin and ear issues and complaints of itchy dogs are among the top reasons owners bring their canine friends to see us.  Food and seasonal allergies are sometimes causes, as well as fleas.  But sometimes the itchiness can be blamed on microscopic invaders, one of several species of mites.

Sarcoptes scabiei
This is the mite that causes sarcoptic mange, also referred to as scabies.  The adult mite lives in the host’s skin for three to four weeks.  The female mite burrows into the skin after mating and deposits eggs in the tunnel behind her.

The eggs hatch and proceed through various life cycles before the new adults move to the surface of the skin and begin the process anew.  The motion of the burrowing female and the movement of the stages of development cause extreme itching and the presence of the eggs under the skin cause an allergic response that further increases itching.

Sarcoptic mange mites prefer hairless skin for burrowing, so the red, scaly skin that characterizes this skin infection first appears on the ear flaps, elbows and belly.  Left untreated, most of the body will be affected.

This mite is contagious and is spread from dog to dog by direct contact.  Mites can live off of their host, but are only infective for 36 hours, rendering environmental treatment largely unnecessary.  This mite is capable of spreading to cats and humans, but the preferred host is dogs and infections on other species do not tend to persist.

Sarcoptic mange is diagnosed with a skin scraping, in which a sample of the patient’s skin is scraped with a scalpel blade and examined under a microscope.  A scratching dog breaks open the tunnels, which kills the adult mites, making it difficult to see mites on a scraping sample.  When mites are seen, the diagnosis is confirmed; however, if the hair loss and itching pattern suggests sarcoptic mange and no mites are seen, the doctor may opt to treat anyway. In these cases, a medication trial is performed and if improvement is seen within two to four weeks, the diagnosis is considered accurate. Due to the infective nature of this mite, all dogs within the household should be treated.

Your dog may also be treated with corticosteroids to control the itching and antibiotics for secondary bacterial infections (from scratching).

Demodex canis
This is the mite that causes demodectic mange.  All dogs possess this mite on their skin, having contracted it from their mothers after birth from close contact.  In healthy dogs, the mites exist in harmony with their host; however, when the natural balance is upset and the host’s immune system is affected, the mite proliferates out of control and causes serious skin disease.

This form of mange has three forms:
1. Localized, in which the face and head are affected.  Scaly bald patches are seen in several small, round lesions.  This is a common ailment in puppyhood.
2. Generalized, in which the entire dog is covered with patchy fur, bald spots and skin infections.  In severe generalized cases, the patient is also suffering from cancer or organ disease. These patients should receive a full work up.
3. Demodectic Pododermatitis, in which the mange is confined to the feet. Certain breeds, such as the Sharpei and Old English Sheepdog, get severe forms of this condition.  This form of mange is very resistant to treatment, as the mites reside deep within the follicle and patients tend to develop secondary bacterial infections.

Demodex is not considered to be contagious, as the mites are normal residents of a dog’s skin.  Treatment is a multistep approach, involving medication to kill the mites, as well as immune support and feeding a highly nutritious diet.  Skin scrapings are taken every two to four weeks and a patient is considered effectively treated after two to three negative skin scraping tests.  Most young dogs recover completely from this mite; older and chronically immune suppressed patients may need lifelong treatment to keep the mites under control.

Effective treatments for demodectic mange have not always been available, so many home remedies have popped up before production of broad spectrum antiparasitic drugs.  Many of these home remedies are highly dangerous! Please do not apply anything to your pet’s skin or give him anything orally without your vet’s guidance.

Ear Mites
Commonly seen in stray pets, puppies and kittens and outdoor cats, the ear mite is a tiny infectious organism that looks most like a small tick.  They can be seen with the naked eye in severe infections, appearing as small white dots that move, and are easy to identify under the microscope.

Owners frequently think that red and inflamed ears are a result of ear mites, but those cases are usually due to yeast or bacterial infections.  True ear mite infections are characterized by extreme itching and the presence of dry, black and crumbly discharge that resembles coffee grounds.

Ear mites are contagious between pets and if your pet has them, he has certainly gotten them from another animal with which he has been socializing.

Treatment is usually applied topically, either directly in the ear or to the skin.  Injections are available but due to the greater expense and involvement, pets who will not allow handling of their ears are treated this way and all others with topical medications. Over the counter treatments for ear mites are not recommended.

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