Demodectic Mange

When we hear the term "mangy dog," we immediately get this picture in our minds of a dog with severe skin lesions, crusts, open sores, hair loss, uncontrollable itching, and very smelly, though we do occasionally encounter this sad sight, most of the times, the mange we diagnose is not nearly as terrifying. The two most common forms of mange we see in practice are sarcoptic mange, or scabies, which we've already covered here on petcare TV, and demodectic mange, also known as demodecosis.

Demodectic mange is caused by a microscopic cigar-shaped mite which lives deep in the skin at the level of the hair follicles. Years ago it was believed that about 50 percent of dogs had this mite living in their skin as a normal inhabitant-today, however, that number has changed. It is now believed that 100 percent of dogs peacefully coexist with this mite. As gross as this statistic is, consider this-about 30 percent of human adults harbor the human demodectic mange mite in their eyebrows! Well, if this mite lives on all dogs, why don't all dogs have demodectic mange infections? Also, as opposed to the scabies mite which is highly contagious, the democtes mite is non-contagious-so how did all the dogs pick up this infection in the first place? Firstly, dogs are born with the mites-probably, as with many parasites, passed on to them in utero from their mothers. And, it seems that developing an active infection is, surprise, closely linked to the dog's immune state. So, we see more infections in dogs which are immune-compromised-stressed because of emotional issues, recovering from surgery or from a major illness, malnourished from being homeless, female dogs after whelping a litter, etc. The earliest symptoms are simply patchy areas of alopecia, or hair loss, so the coat looks very thin in certain areas-commonly around the face, eyes, neck and shoulders. The exposed skin often looks totally fine, but sometimes can appear slightly irritated with small pustules from secondary skin infection, or, in more chronic cases, can start looking dark and leathery. Interestingly, in contrast to the scabies mite which is intensely pruritic, or itchy, the demodectic mite by itself is not really pruritic-it's the very common secondary skin infection which causes most of the discomfort and itching.

Diagnosis is usually fairly easy to make, as the mites are often readily visible on a skin scraping cytology slide-another difference from scabies which is very difficult to identify. Occasionally, with severe or chronic cases, the mites are so deep within the skin; a skin biopsy is needed to accurately identify the mites.

Once a diagnosis is made treatment should be started. There are a few treatment options available, so you want to check with your veterinarian to see which one he or she prefers. Since many of the small solitary lesions can heal on their own, many veterinarians choose not to treat them. Some may simply use a topical ointment or cream on the few lesions. With more generalized infections, dips may be used, spot-on topical medications, injections, or oral solutions are often employed, and the common secondary skin infection, if present, will be treated concurrently. No one treatment is always 100 percent effective, so your veterinarian may elect to use a combination of treatments. As I mentioned, the good news is-if there is such a thing with a mange infection-this mange is not contagious to you or your other pets, so no precautions need to be made.